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Fluid migration paths in the marine strata of typical structures in the western Hubei-eastern Chongqing area, China

Fluid migration paths in the marine strata of typical structures in the western Hubei-eastern... Pet.Sci.(2013)10:1-18 1 DOI 10.1007/s12182-013-0244-y Fluid migration paths in the marine strata of typical structures in the western Hubei– eastern Chongqing area, China 1 1 2 1 1 Xu Guosheng , Liang Jiaju , Gong Deyu , Wang Guozhi , Yuan Haifeng , 1 3 Cao Junxing and Zhang Chengfu State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (Chengdu University of Technology), Sichuan 610059, China Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China 3X\DQJ+HQDQ&KLQD6,123(&=KRQJ\XDQ2LO¿HOG&RPSDQ\ JHUOLQ+HLGHOEHUHUODJ%9‹&KLQD8QLYHUVLW\RI3HWUROHXP %HLMLQJ DQG6SULQJHU Abstract: 7KHZHVWHUQ+XEHL±HDVWHUQ&KRQJTLQJDUHDLVDQLPSRUWDQWSURVSHFWLYH]RQHIRURLODQG JDVH[SORUDWLRQLQWKHFHQWUDODQJW]H<DUHD7KUHHUHSUHVHQWDWLYHVWUXFWXUHVWKH;LQFKDQJVWUXFWXUH /RQJMXEDJDVEHDULQJVWUXFWXUHDQGWKH-LDQQDQJDV¿HOGZHUHHOHFWHGVWRDQDO\]HELRPDUNHUSDUDPHWHUV in marine strata and to examine various types of natural gas and hydrocarbon sources. Fluid inclusions; carbon, oxygen, and strontium isotopic characteristics; organic geochemical analysis and simulation RIK\GURFDUERQJHQHUDWLRQDQGH[SXOVLRQKLVWRU\RIVRXUFHURFNVZHUHXVHGIRUWUDFLQJÀXLGPLJUDWLRQ paths in marine strata of the study area. The Carboniferous-Triassic reservoirs in three typical structures DOOH[SHULHQFHGDWOHDVWWZRVWDJHVRIÀXLGDFFXPXODWLRQ$OOP DULQHVWUDWDDERYHWKHHDUO\HUPLDQ3HUHZ VKRZQWRKDYHÀXLGVRULJLQDWLQJLQWKHHUPLDQ3IHUHGURFNVIURPZKLFKWKHODWHGLIVWDJH7KHÀXLGVXLGVÀ DFFXPXODWHGLQWKHODWH3HUPLDQUHVHUYRLUVRIWKH;LQFKDQJFWXUHVWUXHUHZ&DPEULDQXLGVÀZKLOHWKRVH LQWKHODWH&DUERQLIHURXVUHVHUYRLUVZHUHVRXUFHGIURPDFRPELQ DWLRQRI6LOXULDQDQG&DPEULDQÀXLGV $ORQJGLVWDQFHDQGJHVFDOHODUFURVVIRUPDWLRQDOÀRZRIÀXLGVGHVWUR\HGWKHSUHVHUYDWLRQFRQGLWLRQVRI HDUOLHUVKRUWGLVWDQFHLRQDODFFXPXODWHG$FURVVIRUPDWDFFXPXODWLRQK\GURFDUERQVRI6LOXULDQXLGVÀDVZ shown in the late Permian reservoirs of the Longjuba structure with favorable hydrocarbon preservation conditions. The fluid accumulation in the Carboniferous reservoirs of the Jiannan structure mainly RULJLQDWHGIURPQHLJKERULQJ6LOXULDQVWUDWDZLWKDVPDOODPRXQWIURPWKH&DPEULDQVWUDWD$VDUHVXOW the Jiannan structure was determined to have the best preservation conditions of the three. Comparative DQDO\VLVRIÀXLGPLJUDWLRQSDWKVLQWKHWKUHHVWUXFWXUHVUHYHDOHGWKDWWKH]RQHZLWKDZHDNHUODWHWHFWRQLVP DQGQRVXSHULPSRVLWLRQDQGPRGL¿FDWLRQRIWKH8SSHUDQG/RZHUDOHR]RLF3ÀXLGVRUWKH8SSHU3DOHR]RLF ]RQHLWKZWKHXLGÀJLQJFKDUIURPWKH/RZHUDOHR]RLF3LQWKHWHUQHVZ+XEHL±HDVWHUQ&KRQJTLQJDUHDDUH important target areas for future exploration. Key words:HVWHUQ+XEHL±HDVWHUQ:&KRQJTLQJDUHDPDULQHVWUDWDDOJHRFKHPLFWUDFHUÀXLGPLJUDWLRQ path &DOHGRQLDQ'RQJZX,QGR6LQLDQDQVKDQ<DQG+LPDOD\DQ 1 Introduction movements. The multi-phase tectonic activities have to a The marine carbonate areas of the superimposed basins certain degree reformed and damaged the early excellent in the south of China have become important targets for preservation condition. It is safe to say that the preservation H[SORUDWLRQIRURLODQGJDVLQ&KLQD+RZHYHUDVWKH\KDYH FRQGLWLRQKDVEHFRPHDNH\IDFWRUUHVWULFWLQJWKHH[SORUDWLRQ a deep burial depth and have experienced multiple cycles for oil and gas in these marine carbonate areas in the south of structural movements and intense post-reconstructions, of China. Scholars have studied the preservation condition the geological conditions of these areas are especially IURPVXFKSHUVSHFWLYHVDVFDSURFNSK\VLFDOSURSHUWLHV complicated. The most influential movements are the hydrodynamic environment, sealing ability of faults and tectonic movements. It is not possible for us to evaluate the static preservation condition of the complicated areas that HPDLOOLDQJMLDMX#TTFRP &RUUHVSRQGLQJDXWKRU have gone through multi-phase tectonic activities from only Received June 8, 2011 WKHSHUVSHFWLYHRIJHQHUDOSDUDPHWHUVRIFDSURFNSK\VLFDO 2 Pet.Sci.(2013)10:1-18 properties. We have found a new way to evaluate the LVDSDUWRIWKHFHQWUDODQJW]H< DUHD ;XDQG/LQ preservation condition of the marine oil and gas from the Liu et al, 2007), is geographically located in the western G\QDPLFHYDOXDWLRQ$SHUVSHFWLYHRISDOHRÀXLGJHRFKHPLVWU\ +XEHL3URYLQFHDQGHDVWHUQ&KRQJTLQJ&LW\7KLVDUHDLV can be conducted for the preservation condition of the areas that have experienced multi-phase tectonic activities. The front in the eastern margin of the Sichuan Basin, covering following three typical structures that differ significantly in DQ[LDQ:6KL]KXDQG/LFKXDQV\QFOLQRULXPV)DQJGRXVKDQ H[SORUDWLRQIHFWLYHQHVVHI;LQFKDQJ/RQJMXEDDQG-LDQQDQ and Qiyueshan anticlinoriums, and other tectonic units ZHUHFKRVHQDVFDVHVWRDQDO\]HRLODQGJDVVRXUFHVLQWKH )LJ 7KHVWXG\UHJLRQKDVDQDUHDRINP , and PDULQHVWUDWDRIZHVWHUQ+XEHL±HDVWHUQ&KRQJTLQJDUHDDQG VHFRQGDU\VWUXFWXUHVXSL]HDUHGHYHORSHGZKLFKLQFOXGH<WKH WRWUDFHÀXLGPLJUDWLRQSDWKV7KLVLVH[SHFWHGWRVKHGOLJKW /LDQJTLDR&L]KX\D*DRIHQJFKDQJ0DFDRED'DFKLJDQMLQJ RQWKHIRUPDWLRQHYROXWLRQGHVWUXFWLRQDQGPRGL¿FDWLRQRI +XDQJMLQWDLDQMLQJ<&KD\XDQSLQJ;LQFKDQJ-LDQQDQDQG IHUHQWVWUXFWXUHVDQGWRSURYLGHDVFLHQWL¿FEDVLVIRUIXUWKGLI HU /RQJMXEDVWUXFWXUHV1XPHURXVJDV¿HOGVLQFOXGLQJ-LDQQDQ exploration for oil and gas in this area. Gaofengchang, and Dachiganjing, and gas-bearing structures DQMLQJDQG/RQJMXED<DQJGX[L&L]KX\D<XSL]H<LQFOXGLQJ 2 Geological setting have already been discovered. 7KHZHVWHUQ+XEHL±HDVWHUQ&KRQJTLQJDUHDZKLFK 0DULQHEDVLQVZHUHGHYHORSHGLQWKHFHQWUDODQJW]H< Fengjie The Yangtze River Yunyang 0 10 20 km Wanxian Xinchang2 Well Xinchang Tuxiangba Gaofengchang Cizhuya Longjuba Synclinorium Long 8 well of Wanxian Liangqiao Ma’ancao Jian 44 well Yupize Dachiganjing Jiannan Sujiachang Jian well 38 Lichuan Zhongxian Synclinorium Synclinorium Yangduxi of Shizhu of Lichuan Yanjing Chayuanping Shizhu Huangjintai Boundary line Reverse fault The Yangtze River Fengdu Anticlinorium Anticlinorium of Qiyueshan of Fangdoushan Shuangliuba Anticlinorium Typical structure Secondary structure Fig. 1KRQJTLQJDUHDDQGORFDWLRQGLDJUDPRIW\SLFDOVWUXFWXUHV&ODVVL¿FDWLRQRIWHFWRQLFXQLWVLQWKHZHVWHUQ+XEHL±HDVWHUQ& DUHDIURPWKHHDUO\6LQLDQSHULRGRIWKH/DWH3URWHUR]RLF X)HWDO/LXHWDOX;DQG/LQ&KHQ WRWKHODWH(DUO\ULDVVLF7 RIWKH0HVR]RLFHUD7KHVWXG\ et al, 2007). The area west of the Qiyueshan anticlinorium to area experienced Caledonian and Indo-Sinian closure and WKH)DQJGRXVKDQDQWLFOLQRULXPDQGWKH6KL]KXV\QFOLQRULXP orogeny in the South China and Paleo-Qinling oceans, LVFKDUDFWHUL]HGE\IDYRUDEOHSUHVHUYDWLRQFRQGLWLRQV where two stages of mass marine regression occurred, and with a high degree of trap identification. In addition, the marine strata were developed mainly as deep-water basin area is situated in a beneficial paleo-tectonic position for DQGVKDOORZSODWIRUPIDFLHV )LJ 0XOWLSOHVHWVRIVRXUFH K\GURFDUERQPLJUDWLRQDQGDFFXPXODWLRQZKLFKPDNHVLWD reservoir-seal assemblages were developed vertically. Two IDYRUDEOHH[SORUDWLRQ]RQH *XRHWDO 7KH4L\XHVKDQ sets of large source-reservoir-seal assemblages (i.e., upper anticlinorium and its eastern part as well as the Lichuan DQGORZHUDVVHPEODJHV ZHUHGLYLGHGE\H[WUHPHO\WKLFN V\QFOLQRULXPDUHFRPSDUDWLYHO\SURVSHFWLYH]RQHV 'DLHWDO Silurian shale as the boundary, constituting the two major 2001). In the Longjuba-Jiannan structure echeloned in the exploration regions in this study area (Wu, 1997; Yang et al, FHQWUDO6KL]KXV\QFOLQRULXPDK\GURFDUERQDFFXPXODWLRQ JHRWHFWRQLFDOO\FODVVL¿HGDVDGHSUHVVLRQEHOWRIWKH'DEDVKDQ Variscan Caledonian Jinning Indo-Sinian tectonic cycle Variscan tectonic cycle tectonic cycle tectonic cycle tectonic cycle Jialingjiang Hanjiadian Longmaxi Lower Upper Lower Middle Lower Triassic Permian Silurian Ordovician Cambrian Sinian Mesozoic Palaeozoic Feixianguan Pet.Sci.(2013)10:1-18 3 FRPSRVLWLRQVRIK\GURFDUERQVIURPWKHVDPHVRXUFHURFNV Stratigraphy Code Lithology Age, Ma Tectonic cycle while large differences are evident in those from different ErathemSystem Series Formation VRXUFHURFNV6XFKVLPLODULWLHVVHUYHDVDEDVLVIRURLO T j 1 5 T j source correlation. Currently, gas chromatography and mass 1 4 T j VSHFWURPHWU\ *&06 SURYLGHZLGHO\XVHGELRPDUNHUVIRU 1 3 RLOVRXUFHFRUUHODWLRQ $O0HVKDULHWDO +\GURFDUERQV T j are altered during biodegradation processes (Rowe and T j 0XHKOHQEDFKV0DVWHUVRQ DQGJURXQGZDWHU T f scouring, resulting in incorrect oil-source correlation. +RZHYHUWKHLQIOXHQFHVRIH[WHUQDOVHFRQGDU\IDFWRUVDUH T f effectively reduced in the correlation processes through the T f XVHRIVXFKWHFKQLTXHVDVELRPDUNHUVDQGFRPSUHKHQVLYH FRPSDULVRQRIYDULRXVSDUDPHWHUV$OWKRXJKLVRWRSHVDUH T f WKHPRVWLPSRUWDQWLQGLFDWRUVLQRLOJDVFRPSDULVRQV +DR 251.0 Dalong P d et al, 2000), fractionation will occur in isotopes during Changxing P ch hydrocarbon migration (Galimov et al, 1973; Karlsen et al, Longtan P l %RUHKDPHWDO ZKLFKFUHDWHVGLI¿FXOWLHVLQJDV source correlation. Maokou P m $QPRGHOWRHVWLPDWHRUJDQLFPDWXULW\RQWKHEDVLV of vitrinite reflectance was first completed by the time- Qixia P q temperature index (TTI) method (Waples, 1980) and this was Liangshan P l 299.0 Carboni- WKHQUHSODFHGE\DPRGHOWKDWFDOFXODWHVYLWULQLWHUHÀHFWLYLW\ Middle Huanglong C hl ferous (R PRUHHI¿FLHQWO\NQRZQDVWKH(DV\ R dynamic model o o 359.2 6ZHHQH\DQG%XUQKDP $WKHUPDOUHODWHGELRPDUNHU S h UDWLRZDVSURSRVHGE\0DFNHQ]LHHWDO 0DFNHQ]LHHWDO 0DFNHQ]LHDQG0FNHQ]LH IRUEDVLQ 416.0 Xiaoheba S x 1 modeling, so that the paleotemperature could be calculated more accurately (Welte and Yalcin, 1988; Ungerer, 1990). WKH(DV\+RZHYHU R FKHPLFDONLQHWLFPRGHOODWHUSURSRVHG by Sweeney and Burnham (1990) is the most commonly S l used model in current studies on paleotemperature. On the EDVLVRIYLWULQLWHUHÀHFWDQFHPHDVXUHGIURPGULOOLQJFRUHVD EHWWHU(DV\ R dynamic simulation method with a broader 433.7 application scope was used in this study to reconstruct the WKHUPDOKLVWRU\RIVRXUFHURFNVDQGWKHHYROXWLRQDU\KLVWRU\ of hydrocarbon generation. The previous R YDOXHZDV 488.3 $VHFRQGDU\K\GURFDUERQPLJUDWLRQDQGUHVHUYRLUJHFKDU principle was described by England et al (1987; 1995), 5FNKHLPDQG(QJODQG  DQG(QJODQGDQG0DFNHQ]LH 542.0 (1989), in which the component, phases, temperature, and other information on inclusions were used to calibrate the history of hydrocarbon charge and time of hydrocarbon accumulation. In addition, fluid inclusion stratigraphy was Fig. 2 Synthetic column map of Z-T in the western applied to fluid source and migration pathway research +XEHL±HDVWHUQ&KRQJTLQJDUHDVKRZLQJWHFWRQLFF\FOHV by some scholars (Barclay et al, 2000). The inclusion KRPRJHQL]DWLRQWHPSHUDWXUHGLVFXVVHGKHUHLQJHQHUDOO\ belt was formed with Jiannan as the center. The Jiannan gas refers to that of hydrocarbon-bearing saline inclusion, rather field was discovered in the central syncline, proving that WKDQWKDWRIK\GURFDUERQLQFOXVLRQV7KHKRPRJHQL]DWLRQ the Longjuba-Jiannan structure had favorable preservation temperature of hydrocarbon inclusions is often lower than that conditions for gas reservoirs in addition to a tectonic setting of saline inclusions of the same period (Lu and Guo, 2000). for hydrocarbon accumulation (Chen, 2003; Gao, 2004). Inclusions are able to reflect the essential characteristics of ore-forming fluids and provide a series of original data on 3 Sample analysis such mineral formation parameters as temperature, elemental $VLVZLGHO\DFFHSWHGNHURJHQLQVRXUFHURFNVLV FRPSRVLWLRQDQGVDOLQLW\$IOXLGJHRFKHPLFDOWUDFHUZDV FUDFNHGLQWRSHWUROHXPDQGQDWXUDOJDVXQGHUFHUWDLQ combined with the inclusion test and analysis methods in this FRQGLWLRQVDQGK\GURFDUERQLQVRXUFHURFNVKDVDJHQHWLF JHGXUDWLRQVSDSHUWRVWXG\ÀXLGPLJUDWLRQSDWKDQGFKDU relationship with bitumen in addition to oil and gas in the URFNUHVHUYRLUV7KXVVLPLODULWLHVH[LVWLQWKHFKHPLFDO of natural gas, inclusions, carbon, oxygen, and strontium in HWKHQGHWHUPLQHGELRPDUNHUVDQGVWDEOHFDUERQLVRWRSHV 4 Pet.Sci.(2013)10:1-18 YHLQVDQGVXUURXQGLQJURFNVLQDGGLWLRQWRRWKHUJHRFKHPLFDO well is of high maturity, only methane and small amounts of analysis data and their sources. ethane and propane were detected; thus, light hydrocarbon )LYHQHZVDPSOHVRISRWHQWLDOVRXUFHURFNVDQGILYH DQDO\VLVFRXOGQRWEHSHUIRUPHG$VDUHVXOWWKHJDVLVRWRSLF samples of residual organic material in reservoirs were PDVVVSHFWURPHWHU70$ZDVXVHGWRGHWHUPLQHVWDEOH REWDLQHGIURPHOOZ;LQFKDQJLQWKHHVWHUQZ+XEHL±HDVWHUQ carbon isotopes of natural gas. &KRQJTLQJDUHD$JDVFKURPDWRJUDSK +3+HZOHWW The collected samples of calcite and gypsum veins that 3DFNDUG DQGJDVFKURPDWRJUDSKPDVVVSHFWURPHWHU *& ¿OOHGIUDFWXUHVLQUHVHUYRLUURFNVHUHZWHVWHGE\WKH*XL\DQJ 068063 ZHUHXVHGWRPHDVXUHWRWDOK\GURFDUERQJDV ,QVWLWXWHRI*HRFKHPLVWU\&KLQHVH$FDGHP\RI6FLHQFHV FKURPDWRJDSK\ELRPDUNHUVDQGYLWULQLWHUHIOHFWDQFHZDV It was determined that hydrocarbon gases were contained measured with a microphotometer (Tables 1-3). Due to the LQIOXLGLQFOXVLRQV+RZHYHUIHZK\GURFDUERQEHDULQJ high maturity of residual organic matter in the study area, the organic extract was too limited to permit the analysis of group ,QFOXVLRQ 0&,Œ DQDO\VLVFRXOGQRWEHSHUIRUPHG,QVWHDG components and their isotopes. ODVHU5DPDQTXDQWLWDWLYHDQDO\VLVZDVXVHGRQLQFOXVLRQ The analysis data of 17 natural gas samples in 16 wells components. In addition, carbon, oxygen, and strontium were used in this study (Table 4 and Table 5), including one isotopic values were obtained with the UK VG354 isotope Permian natural gas sample from the well Long 8 in the PDVVVSHFWURPHWHU 7,06 E\WKH,VRWRSH0DVV/DERUDWRU\RI Longjuba structure. Because the Permian natural gas in this DEOH 1DQMLQJ8QLYHUVLW\ 7$QDO\VLV&HQWHU0RGHUQ Table 1WDVDPSOHVIURPZHOO;LQFKDQJ6DWXUDWHGK\GURFDUERQFKURPDWRJUDSK\SDUDPHWHUVRIPDULQHVWUD C +C 21 22 Sample No. Depth, m +RUL]RQ Lithologic description ™& ™& Pr/nC Ph/nC Pr/Ph 21 22 17 18 /C +C 28 29 ;& 2824.42 T f 'DUNJUD\OLPHVWRQHSRWHQWLDOVRXUFHURFNV 1.33 0.95 0.64 0.86 0.53 ;& 2828.22 T f %ODFNOLPHVWRQHSRWHQWLDOVRXUFHURFNV / 3.16 1.05 1.42 0.55 'DUNJUD\OLPHVWRQHRUJDQLFPDWWHUILOOHGDORQJVXWXUH ;& 2848.22 T f 4.90 2.49 0.29 0.75 0.48 ]RQHV *UD\GDUNJUD\OLPHVWRQHRUJDQLFPDWWHUILOOHGDORQJ ;& 2853.83 T f 3.21 2.01 0.63 1.06 0.50 VXWXUH]RQHV /LJKWJUD\OLPHVWRQHEODFNRUJDQLFPDWWHUILOOHGDORQJ ;& 2862.90 T f 12.75 1.99 0.75 0.96 0.60 VXWXUH]RQHV ;&V 3338.35 P c %ODFNOLPHVWRQHSRWHQWLDOVRXUFHURFNV 1.82 1.34 0.43 0.74 0.51 ;& 3376.04 P c JDQLFPDWWHU'DUNJUD\OLPHVWRQH¿OOHGZLWKPDVVLYHRU 4.00 1.37 1.50 1.82 0.23 ;&V 4607.54 P T %ODFNFRDOURFNSRWHQWLDOVRXUFHURFNV / 2.22 0.83 1.10 0.59 ;&V 4608.54 P T %ODFNFRDOURFNSRWHQWLDOVRXUFHURFNV 10.00 1.56 1.11 1.25 0.40 *UD\GRORPLWHELWXPHQDORQJVXWXUH]RQHVDQG¿OOHGLQ ;& 4623.04 C c 0.53 0.67 0.70 1.03 0.61 factures Table 2HUSDQHDQGVWHUDQHELRPDUNHUSDUDPHWHUVRIPDULQHVWUDWDVDPS7 OHVIURPWKHZHOO;LQFKDQJ C Ts/ C 22S/ Gammacerane / Tricyclic-terpane/ C ĮĮĮ 6  C +C -pregnane Diasterane/ 29 32 29 21 22 Sample No. +RUL]RQ Ts/Tm (C Ts+C ) (22S+22R) C hopane C hopane /(20S+20R) /C ĮĮĮ 5 regular sterane 29 29 30 30 29 ;& T f 0.69 0.21 0.59 0.26 1.06 0.38 0.44 0.14 ;& T f 0.95 0.29 0.62 0.17 3.67 0.30 2.61 0.22 ;& T f 0.56 0.25 0.59 0.26 0.49 0.41 0.23 0.07 ;& T f 0.73 0.14 0.59 0.26 2.02 0.36 1.15 0.14 ;& T f 1.61 0.18 0.62 0.34 0.58 0.35 1.14 0.26 ;&V P c 0.50 0.09 0.59 0.29 0.26 0.46 0.09 0.06 ;& P c 0.93 0.28 0.57 0.19 1.71 0.34 1.03 0.20 ;&V P T 1.07 0.21 0.60 0.23 2.50 0.31 3.15 0.23 ;&V P T 0.90 0.18 0.60 0.19 3.33 0.29 2.62 0.28 ;& C c 0.98 0.18 0.60 0.29 1.26 0.37 0.58 0.41 LQFOXVLRQVZHUHGHWHFWHG7KXV0ROHFXODU&RPSRVLWLRQRI2LO Pet.Sci.(2013)10:1-18 5 Table 3URPDWLFFKDUDFWHULVWLFSDUDPHWHUVRIVDPSOHVIURPZHOO;LQFKD$ QJ 5HODWLYHFRQWHQW 5HODWLYHFRQWHQW Sample 'LEHQ]RWKLRSKHQH +RUL]RQ SF/P No. Phenanthrene Chrysene GLEHQ]RIXUDQDQG 'LEHQ]RWKLRSKHQH Fluorene 'LEHQ]RIXUDQ ÀXRUHQH ;& T f 94.34 / 5.66 0.978 0.244 / 0.047 78.50 / 21.50 ;& T f 87.52 / 12.48 1.050 0.624 0.279 0.033 23.00 67.38 9.62 ;& T f 93.90 / 6.10 3.222 0.993 0.547 0.003 5.38 80.52 14.10 ;& T f 99.45 / 0.55 2.388 0.332 0.021 / / 100.00 / ;& T f 84.16 / 15.84 1.162 2.225 / 0.032 16.94 67.56 15.50 ;&V P c 93.46 / 6.54 2.851 0.751 0.368 0.006 8.23 84.58 7.19 ;& P c 89.86 / 10.14 1.842 4.408 1.345 0.014 12.80 75.29 11.91 ;&V P T 77.81 / 22.19 1.397 1.845 0.603 0.029 10.15 67.13 22.72 ;&V P T 80.63 / 19.37 1.310 2.250 0.544 0.030 12.57 65.53 21.91 ;& C c 89.57 / 10.43 0.894 0.716 0.110 0.031 26.93 47.67 25.40 Table 4 Conventional components of natural gas in C -T j formations in the Jiannan-Longjuba structure and characteristics of carbon isotopes in well Long 8, 2 1 VWUXFWXUHLVLQDFFRUGDQFHZLWKWKDWUHSRUWHGE\0D  7KHGDWDIRUWKH-LDQQDQ-LDQQDQJDV¿HOGDQGDGMDFHQWDUHDV Well No. Formation Depth, m C , C  C  N  CO  + C /C -C 1 2 3 2 2 2 1 1 5 Long 8 P m 98.35 0.14 / 0.28 1.2 / 99.85 Jian 32 T j 2494.05-2531 94.70 0.17 — 1.67 3.07 0.40 99.82 Jian 3 T f 2709-2762 96.04 0.20 — 0.31 2.93 0.52 99.79 Jian 10 T f 2927-2941 9652 0.12 — 1.15 1.94 0.27 99.88 Jian 45 T f 3061-3089 94.93 0.21 — 1.87 2.81 0.18 99.78 Jian 15 T f 3110-3161.1 96.55 0.12 — 1.51 1.72 0.105 99.88 Jian 41 T f 3343.6-3402 92.00 0.14 — 0.84 4.51 2.48 99.85 Jian 47 T f 3614.4-3642.6 95.93 0.09 — 1.72 1.98 0.28 99.91 Jian 16 P c 3109.9-3229.6 86.73 0.17 — 1.19 8.56 3.36 99.80 Jian 40 P c 3329.6-3348.4 87.04 0.07 — 0.77 8.87 3.24 99.92 Jian 43 P c 3456-3483 92.05 0.19 — 0.26 5.70 1.80 99.72 Jian 44 P c 3738.11-3760.18 88.37 0.06 — 1.30 7.39 2.88 99.93 Jian 13 C 3728.59-3748.15 94.31 1.22 0.24 3.39 0.68 0.162 98.72 Jian 37 C 3836.4-3860.0 94.71 1.24 0.15 3.24 0.66 0 98.70 Jian 28 C 3943-3950 94.57 1.23 0.13 3.51 0.56 0 98.72 Table 5 QJMXEDVWUXFWXUHLVLQ7KHGDWDIRUWKH/R$QDO\VLVUHVXOWVRIWKHFDUERQLVRWRSHVRIWKHQDWXUDOJDVLQWKH/RQJMXEDVWUXFWXUHDQG-LDQQDQJDV¿HOG K,QVWLWXWHRI-LDQJKDQ2LO¿HOGDFFRUGDQFHZLWKWKDWRIWKH([SORUDWLRQDQG'HYHORSPHQW5HVHDUF 13 13 13 13 Structure location Well No. Formation Depth, m į C , ‰ į C , ‰ į C į C , ‰ 1 2 2 1 Longjuba Long 8 P m -29.9 -32.7 -2.8 Jian 31 T j 2777.5-2856 -32.2 -37.8 -5.6 The northern high point Jian 31 T j 2777.5-2856 -32.4 -36.4 -4.0 Jian 35 T f 3066.4-3114 -32.1 -38.4 -6.3 The southern high point Jian 27 Ceping1 T f 3680.78-4506.33 -31.0 -38.0 -7.0 Jian 61 T f -33.1 -41.4 -8.3 Jian 10 T f 2927-2941 -32.1 -37.4 -5.3 The northern high point Jian 10 T f 2927-2941 -31.4 -33.3 -1.9 Jian 51 T f -30.8 -28.5 2.3 Jian 43 P ch 3456-3483 -32.0 -38.9 -6.9 Southern high point Jian 43 P ch 3456-3483 -32.2 -37.2 -5.0 Jian 16 P ch 3109.9-3229.6 -31.7 -33.6 -1.9 Northern high point Jian 44 Yuan1 P ch 3145.94-3600 -33.5 -35.6 -2.1 Jian 34 C 3770-3784 -37.2 -41.4 -4.2 Northern high point Jian 28 C 3941-3950 -35.2 -40.0 -4.8 Jian 28 C 3943-3950 -37.9 -41.4 -3.5 '0)'2)6) )'0) )0) )0)2) 6 Pet.Sci.(2013)10:1-18 Table 6IHUHQWURFNVDQGP,VRWRSLFJHRFKHPLFDODQDO\VLVUHVXOWVRIGLI LQHUDOVLQZHOOV;LQFKDQJ/RQJDQG-LDQ 13 18 87 86 Well Sample No. Lithology Well depth, m +RUL]RQ į C (PDB), ‰ į O (PDB), ‰ Sr/ Sr ;F9 Grayish-white megacryst gypsum 3340.5 íí 0.71 ;F9 Calcite veins 4.708 -5.647 0.7075 ;F& 'DUNJUH\PLFULWH 4.632 -4.43 0.7071 ;LQFKDQJ P ch Grayish-white fine-medium grained calcite ;F9 4.946 -6.98 0.7074 vein patch 3375.64 ;F& Grey micrite 4.742 -4.19 0.707 Grayish-white fine-medium grained calcite Bao 10V 3.747 -6.263 0.7071 veins 2 4314.67 P ch Bao 10C Grey micrite 4.086 -6.081 í Grayish-white fine-medium grained calcite Bao 19V 4.111 -5.908 0.7071 veins Long 8 4557.84 P m Bao 19C 'DUNJUH\PLFULWH 3.873 -5.182 í Bao 22V :KLWH¿QHJUDLQHGFDOFLWHYHLQV 4.108 -5.146 0.7071 4784.48 P m Bao 22C 'DUNJUH\PLFULWH 3.817 -4.727 í J38-6V Grayish-white calcite veins 4.07 -7.113 0.7075 3151.42 J38-6C 'DUNJUH\PLFULWH 4.497 -5.105 í Jian 38 T f Grayish-white fine-medium grained calcite J38-9V 3.748 -6.611 0.7075 veins 3153.2 J38-9C Grey calcarenite 3.956 -6.401 0.7076 DFFRXQWIRURIDOOVDPSOHVWKRVHRIPHGLXPJRRG 4 Organic geochemical tracers in marine VRXUFHURFNZLWKD72&EHWZHHQDQGDFFRXQW strata IRURIDOOVDPSOHVDQGWKRVHRIH[FHOOHQWVRXUFHURFN ZLWKD72&DERYHDFFRXQWIRURIWKHVDPSOHV 7KHZHVWHUQ+XEHL±HDVWHUQ&KRQJTLQJDUHDKDVIRXUVHWV ,QWKH6KL]KX/LFKXDQDUHDWKH R RIWKHVKDOHVRXUFHURFN RI7KH\DUHWKHORZHUVRXUFHURFNVLOXULDQORZHU6&DPEULDQ o LVJHQHUDOO\DERYHLQGLFDWLQJDGU\JDVVWDJH7KH Permian coal-measures, and Permian carbonate. The lower 3HUPLDQFDUERQDWHVRXUFHURFNVKDYHEHHQVHOGRPVWXGLHG &DPEULDQVRXUFHURFNVRIWKH4LRQJ]KXVL)RUPDWLRQLQ DQGDUHFRQVLGHUHGDVPLQRUVRXUFHURFNV WKHHDVW6LFKXDQ%DVLQDUHPDLQO\JUD\LVKEODFNVKDOHZLWK $IWHUDQDO\]LQJWKHFKDUDFWHULVWLFVRIWKHIRXUVHWVRI maximum, minimum and average total organic carbon (TOC) VRXUFHURFNVLQWKHVWXG\DUHDZHZHUHDEOHWRGHILQHWKH YDOXHVRI,QDGGLWLRQDQGUHVSHFWLYHO\ origin of the hydrocarbon in the main production formations VDPSOHV RIWKHWRWDOVDPSOHV KDYHD72& E\VWXG\LQJWKHELRPDUNHUFKDUDFWHULVWLFVRIWKHRUJDQLF YDOXHDERYH7KHK\GURFDUERQJHQHUDWLRQSRWHQWLDO PDWWHU¿OOLQJWKHIUDFWXUHV,QDGGLWLRQZHWUDFHGWKHRULJLQ YDOXHRIWKH&DPEULDQVRXUFHURFNVLQLPPDWXUHDQGORZHU of the fluid by studying the strontium, carbon, and oxygen mature stage is between 0.5 mg/g and 20 mg/g. In the lower LVRWRSHVRIWKHYHLQVRIFDOFLWHGRORPLWHDQGJ\SVXPOOLQJ¿ SDUWKLJKTXDOLW\RXUFHVURFNV&KDYH2YDOXHD7DERYH fractures. We also identified the hydrocarbon accumulation and a hydrocarbon generation potential value between 2 mg/g period and the reservoir forming time through examination of and 35 mg/g. The R RIWKHVRXUFHURFNVLVEHWZHHQDQG inclusions. ZLWKDQDYHUDJHDWUHDFKLQJWKHRYHUPDWXUHVWDJH 7KH6LOXULDQVRXUFHURFNVRIWKH/RQJPD[L)RUPDWLRQLQ 4.1 Organic geochemical tracer in the marine strata WKH6KL]KX;LDQIHQJ/DLIHQJDUHDDUHZHOOGHYHORSHGZLWK of Xinchang structure DQDEXQGDQFHRIRUJDQLFPDWWHU0RVW  RIWKHVDPSOHV KDYH2&D7YDOXHDERYHWKH2&DYHUDJH7YDOXHRIWKH &RULQJZDVSHUIRUPHGRQO\LQZHOO;LQFKDQJRIWKH VRXUFHURFNVLV7KHVRXUFHURFNVKDYHDK\GURFDUERQ ;LQFKDQJVWUXFWXUHVRGULOOFRUHIURPWKLVZHOOZDVWKHRQO\ generation potential value between 2 mg/g and 35 mg/g, intact samples available. Tables 1 and 2 demonstrate the which is higher in the northern part than in the southern part. distribution of the residual organic matter from the source The R LQ6LOXULDQURFNVLQWKHVWXG\DUHDLVEHWZHHQ URFNVDQGUHVHUYRLUV DQG &KURPDWRJUDSK\IURPWKHWKUHHVDPSOHV ;&V;& 7KH3HUPLDQVRXUFHURFNVLQFOXGHWKHFRDOPHDVXUHVDQG V;&V RI3HUPLDQVRXUFHURFNVVKRZHGDXQLPRGDO FDUERQDWHVVKDOHVDPSOHVLQWKHZHVWHUQ+XEHL±HDVWHUQ distribution of saturated hydrocarbons from high to low, of &KRQJTLQJDUHDKDYHDQDYHUDJH2&7YDOXHRI7KH which the ratio between low nDONDQHVDQGKLJK nDONDQHV VDPSOHVRISRRUVRXUFHURFNZLWKD2&7EHWZHHQDQG was 1.34, 2.22, and 1.56, respectively (Fig. 3, Table 1). The Pet.Sci.(2013)10:1-18 7 ratio between isoprenoid hydrocarbon and the corresponding showed two different types of characteristics (Fig. 4, Table nDONDQHZDVHLWKHUGRPLQDWHGE\ nDONDQHRULVRSUHQRLG  ,Q;&IRUV7PH[DPSOH7ZDV& Ts/(C Ts + 29 29 K\GURFDUERQ,Q;&VWKHVDPSOHRIFRDOPHDVXUH C ) was 0.25; gammacerane/C hopane was 0.26; tricyclic 29 30 VRXUFHURFNVLQWKH4L[LD7PV)RUPDWLRQZDV7& Ts/ terpane/C hopane was 0.49; relative content of C and C 29 30 21 22 (C Ts+C ) was 0.18; gammacerane/C hopane was 0.19; pregnane was 0.23; and the ratio of diasterane and regular 29 29 30 tricyclic terpane/C hopane was 3.33; relative content of C sterane was 0.07, showing a similar trend to that of the 30 21 and C pregnane was 2.62; and the ratio between diasterane 3HUPLDQFDUERQDWHVRXUFHURFNV+RZHYHUWKHELRPDUNHU DQGUHJXODUVWHUDQHZDV,Q;&VDVDPSOHRI SDUDPHWHUVRI;&VKRZHGFKDUDFWHULVWLFVLPLODUVWRWKRVH FDUERQDWHVRXUFHURFNVLQWKH&KDQJ[LQJ)RUPDWLRQV7 RI3HUPLDQFRDOPHDVXUHVRXUFHURFNVRIZKLFKV7P7ZDV Tm was 0.50; C Ts/(C Ts+C ) was 0.18; gammacerane/ 0.73; C Ts/(C Ts + C ) was 0.14; gammacerane/C hopane 29 29 29 29 29 29 30 C hopane was 0.29; tricyclic terpane/C hopane was 0.26; was 0.26; tricyclic terpane/C hopane was 2.02; relative 30 30 30 relative content of C and C pregnane was 0.09; and the content of C and C pregnane was 1.15; and the ratio of 21 22 21 22 ratio between diasterane and regular sterane was 0.06 (Table GLDVWHUDQHDQGUHJXODUWHUDQHVZDVDEOH 7 0RUHRYHU 2). Therefore there are at least two different sets of Permian VRPHELRPDUNHUSDUDPHWHUVRIWKLVUHVLGXDORUJDQLFPDWWHU VRXUFHURFNV7KHVHDUHWKH3HUPLDQFRDOPHDVXUHVRXUFH also showed similar characteristics to those from Permian URFNVLQWKH4L[LD)RUPDWLRQDQG3HUPLDQFDUERQDWHVRXUFH FDUERQDWHVRXUFHURFNV7PVVXFKDQGDV7GLDVWHUDQHUHJXODU URFNVLQWKH&KDQJ[LQJ)RUPDWLRQ7KHUHVLGXDORUJDQLF sterane. PDWWHULQWKHSRUHVRIWKH3HUPLDQUHVHUYRLUV;& $QDO\VLVRIDURPDWLFELRPDUNHUVLQZHOO;LQFKDQJ showed a unimodal distribution in saturated hydrocarbon  7DEOH VKRZHGWKDW3HUPLDQFRDOURFNVLQWKH chromatography with a ratio of low-n to high-n carbon of 4L[LD)RUPDWLRQDQGFDUERQDWHURFNVLQWKH&KDQJ[LQJ 1.37, significantly dominated by low-n carbon. In addition, )RUPDWLRQKDGDSKHQDQWKUHQHFRQWHQWRI the sample was dominated by nDONDQHDFFRUGLQJWRWKHUDWLR approaching that of organic matter in the Triassic reservoirs of isoprenoid hydrocarbon and nDONDQH,QWKLVVDPSOHV7 RIWKH)HL[LDQJXDQ)RUPDWLRQZKLFKZDV Tm was 0.93; C Ts/(C Ts+C ) was 0.28; gammacerane/ $PRQJGLEHQ]RWKLRSKHQHGLEHQ]RIXUDQIOXRUHQHDQG 29 29 29 C hopane was 0.19; tricyclic terpane/C hopane was 1.71; their homologues, the fluorene content was similar, while 30 30 relative content of C and C pregnane was 1.02; and the GLIIHUHQFHVH[LVWLQWKHFRQWHQWVRIGLEHQ]RWKLRSKHQHDQG 21 22 ratio between diasterane and regular sterane was 0.20 (Table GLEHQ]RIXUDQ+RZHYHUQRJUHDWGLIIHUHQFHVH[LVWLQ) 7KHELRPDUNHUGLVWULEXWLRQRIWHUSDQHDQGVWHUDQHVKRZHG '0) IOXRUHQHGLPHWK\OIOXRUHQH 6)3 GLEHQ]RWKLRSKHQH that the residual organic matter in the pores of the Permian SKHQDQWKUHQH RU)0)2)'0)'2)6) ÀXRUHQH reservoirs was sourced from Permian coal-measure source PHWK\OIOXRUHQHGLEHQ]RIXUDQ  GLPHWK\OIOXRUHQH URFNV GLPHWK\OGLEHQ]RIXUDQGLEHQ]RWKLRSKHQH UDWLRVRIWKH RUJDQLFPDWWHULQ3HUPLDQVRXUFHURFNVDQG7ULDVVLF XC2 reservoirs, while the organic matter in the Triassic reservoirs XC2-1 H[KLELWHGFKDUDFWHULVWLFVRI3HUPLDQVRXUFHURFNV XC2-2 XC2-11 Therefore, the hydrocarbon sources of residual organic XC2-12 matter in the Triassic reservoirs of the Feixianguan Formation XC2-13 XC2-14s ZHUHIURP3HUPLDQFDUERQDWHURFNVDQGPL[HGFRDO XC2-20 PHDVXUHVRXUFHURFNV+RZHYHUVDWXUDWHGK\GURFDUERQ XC2-23s XC2-22s chromatography proved that the three samples underwent XC2-25 a certain degree of biodegradation, indicating that the preservation conditions of these samples had been damaged in the geological history. 7KHRUJDQLFVDPSOH;&IURPD&DUERQLIHURXV reservoir showed a bimodal distribution in saturated Carbon number hydrocarbon chromatography, of which the ratio of low-n and Fig. 3 nDONDQHGLVWULEXWLRQFKDUDFWHULVWLFVRIPDULQHVWUDWDVDPSOHV high-n carbon was 0.67, indicating high-nDONDQHVGRPLQDWH IURPZHOO;LQFKDQJ The pristane/nC ratio was 0.7 with dominant nC ; the 17 17 &KURPDWRJUDSK\RIJDQLFRUPDWWHUOOLQJ¿WKHVXWXUH]RQH phytane/nC ratio was 1.03 with dominant phytane; and the LQWKH)HL[LDQJXDQ)RUPDWLRQLQZHOO;LQFKDQJ ;& pristane/phytane ratio was 0.61 with dominant phytane. The 11, 12, 13) showed a unimodal distribution in saturated saturated hydrocarbon chromatography of this sample showed hydrocarbon. The ratio between low-n and high-n carbon was FKDUDFWHULVWLFVLPLODUVWRWKDWRI6LOXULDQRXUFHVURFNV ;XHW DQGLQWKHWKUHHVDPSOHVVKRZLQJVLJQL¿FDQW DO EXWFHUWDLQIHUHQFHVGLIH[LVW6LOXULDQVRXUFHURFNV FKDUDFWHULVWLFVRIOLJKWHUDONDQHVD 7EOH  nDONDQHZDV are dominated by high-nDONDQHVLWKZVDWXUDWHGK\GURFDUERQ essentially dominant in the ratio between isoprenoid and FKURPDWRJUDSK\IURPORZWRKLJKZKLOHWKDWRI;& nDONDQHDQGSK\WDQHZDVGRPLQDQWLQWKHUDWLREHWZHHQ was from high to low with characteristics similar to that of pristane and phytane, which is a similar trend to that of the &DPEULDQVRXUFHURFNV7KHWHUSDQHDQGVWHUDQHELRPDUNHU 3HUPLDQFDUERQDWHVRXUFHURFNV+RZHYHUWKHWHUSDQHDQG parameters of this sample, including tricyclic terpane/ VWHUDQHELRPDUNHUSDUDPHWHUVRIWKHUHVLGXDOJDQLFRUPDWWHU C hopane, relative content of C and C pregnane, and 30 21 22 from the three samples from the Feixianguan Formation GLDVWHUDQHUHJXODUVWHUDQHVGLIIHUHGVLJQL¿FDQWO\IURPWKRVH Relative mass fraction, % 8 Pet.Sci.(2013)10:1-18 Abundance Abundance Sample number: XC2-11 M/Z 191 M/Z 217 450000 Depth 2848.22m Formation: T f 50000 10000 34.00 38.00 42.00 46.00 50.00 54.00 58.00 62.00 66.00 70.00 74.00 Time Time 38.00 40.00 42.00 44.00 46.00 48.00 50.00 52.00 54.00 56.00 Abundance Abundance Sample number: XC2-12 Depth: 2853.83m Formation: T f Time Time 38.00 40.00 42.00 44.00 46.00 48.00 50.00 52.00 54.00 56.00 34.00 38.00 42.00 46.00 50.00 54.00 58.00 62.00 66.00 70.00 74.00 Abundance Abundance Sample number: XC2-20 Depth: 3376.04m Formation: P c Time 34.00 38.00 42.00 46.00 50.00 54.00 58.00 62.00 66.00 70.00 Time 37.00 39.00 41.00 43.00 45.00 47.00 49.00 51.00 53.00 55.00 57.00 59.00 Abundance Abundance Sample number: XC2-23S Depth: 4607.54m Formation: P q Time Time 34.00 38.00 42.00 46.00 50.00 54.00 58.00 62.00 66.00 70.00 74.00 38.00 40.00 42.00 44.00 46.00 48.00 50.00 52.00 54.00 56.00 Sample number: XC2-25 Abundance Abundance Depth: 4623.04m Formation: C c Time 34.00 38.00 42.00 46.00 50.00 54.00 58.00 62.00 66.00 70.00 74.00 Time 38.00 40.00 42.00 44.00 46.00 48.00 50.00 52.00 54.00 56.00 Fig. 4 HUSDQHDQGVWHUDQHELRPDUNHUGLDJUDPRIVDPSOHVIURPZHOO;LQF7 KDQJ REVHUYHGLQ3HUPLDQVRXUFHURFNV geochemical characteristics evident in the sample show We consider that the main hydrocarbon sources of WKDWWKH&DUERQLIHURXVDQG3HUPLDQURFNVRQFHZHUHSDUWRI WKH&DUERQLIHURXVUHVHUYRLUVLQZHOO;LQFKDQJZHUH WZRGLIIHUHQWIOXLGV\VWHPVWKDWLV3HUPLDQURFNVDQGWKH 6LOXULDQDQG&DPEULDQVRXUFHURFNV6HYHUHELRGHJUDGDWLRQ underlying strata were completely disconnected before the occurred in the sample; thus, preservation conditions of K\GURFDUERQJHQHUDWHGLQ&DPEULDQRXUFHVURFNVPLJUDWHGWR the petroleum system were damaged. The present organic WKH&DUERQLIHURXVURFNV Pet.Sci.(2013)10:1-18 9 4.2 Organic geochemical tracers in the marine strata The carbon isotope analysis of the natural gas from the of the Longjuba structure well Long 8 in P m Formation indicates that the natural gas is overmatured dry and sapropelic gas (Table 5), with a high 0HWKDQHLVWKHGRPLQDQWQDWXUDOJDVFRPSRQHQWRIWKH PHWKDQHFDUERQLVRWRSHUDWLR)URPWKHFURVVSORWRIį C and 3HUPLDQ0DRNRX)RUPDWLRQLQWKHZHOO/RQJ/RQJMXED į C (Fig. 5), it can be seen that the natural gas from the well VWUXFWXUHDFFRXQWLQJIRU1 and CO were second 2 2 Long 8 P m Formation and the natural gas from P m, P ch and 1 1 2 and third, respectively. The content of ethane was lower at T f formations in eastern Sichuan are basically distributed QR+ S was detected (Table 4). in the same area in the cross-plot, which indicates that the 7KHFDUERQLVRWRSHVRIWKH&+ LVLQÀXHQFHGE\WKHW\SHV 3HUPLDQVRXUFHURFNVKDYHDOVRPDGHVRPHFRQWULEXWLRQWR ZKLFKUHVXOWVLQDQRIWKHVRXUFHURFNVLQDGGLWLRQWRPDWXULW\ the formation of natural gas from the P m Formation in well RYHUODSRIWKHį C distribution interval of coal-type and oil- Long 8. The cause of the reversal of methane and ethane W\SHJDVHVFODVVL¿HGDVKXPLFDQGVDSURSHOLFUHVSHFWLYHO\ ratios might be the mixing of different natural gases from $VDUHVXOWLWLVGLI¿FXOWWRGHWHUPLQHWKHIHUHQFHGLIEHWZHHQ IHUHQWVRXUFHURFNVGLI WKHVHJDVW\SHVXVLQJį C . The carbon isotope ratio in heavy hydrocarbons of natural gas, such as ethane, is more Table 77KHFODVVL¿FDWLRQRIFDUERQLVRWRSHVLQPDULQHQDWXUDOJDV VWDEOH7KLVFDQDFFXUDWHO\UHÀHFWWKHW\SHVRIJDVJHQHUDWLQJ 13 13 materials. By examining criteria based on the carbon isotope Types į C , ‰ į C , ‰ 2 1 analysis of 283 continental and marine samples from 8 basins mature <-40 Sapropelic <-34.0 LQ&KLQD 6KLHWDO;XHWDO'DL=KDQJ overmature >-40 et al, 1987; 1988) in addition to research data of the natural mature <-40 +XPLFEHDULQJ -34.0 - -29.5 sapropelic overmature >-40 gas in marine sediments in the Tarim Basin (Zhao et al, 2001; mature <-32 /LDQJHWDOLH;HWDO ZHHVWLPDWHGWKHJHQHWLF +XPLF >-29.5 overmature >-32 types of natural gas (Table 7). -26 East Sichuan Basin, T f Humic East Sichuan Basin, P ch -28 gas (North) Jian 51 East Sichuan Basin, P m -30 East Sichuan Basin, C hl T f 2 Pch P ch Feixianguan Feix Changxing Changxing 1 Humic bearing Jiannan gas field, T j Formation Fo Formation Formation sapropelic gas -32 Jiannan gas field, T f L Longjuba Lo Jiannan gas field, P ch P m -34 Jiannan gas field, C Jian Jian an 44 44 44 4 4 Longjuba structure, P m -36 1 P m Maokou Formation Jian Jian Jian Jian 43 43 43 43 Jian Jian Jian Jian 10 10 10 10 Sapropelic gas -38 Jian 27 C C Jian Jian Jian 25 25 25 Carboniferous T f, T j, P ch 1 1 2 Jian 43 -40 Jian 28 28 Jian Jian 28 (South) -42 Jian 61 Jian 34 -44 -39 -38 -37 -36 -35 -34 -33 -32 -31 -30 -29 į C1, ‰ /RQJMXEDVWUXFWXUH-LDQQDQJDV¿HOG0HWKDQHDQGHWKDQHFDUERQLVRWRSHUDWLRVRIQDWXUDOJDVLQWKH Fig. 5 and eastern Sichuan Basin Through the matrix-source-judging formula proposed FDOFXODWLRQWKHPDWXULW\RIWKHVRXUFHURFNVLV by Pang et al (2000), with the methane carbon isotopes and ZLWKDQDYHUDJHYDOXHRI7KHDVSKDOWUHIOHFWDQFHRI the components of the natural gas from the well Long 8, WKHGDUNJUH\ELRFODVWLFOLPHVWRQHVDWDGHSWKRIP st WKHJDVW\SHLQGH[ *7, DQGNHURJHQW\SHLQGH[ .7, DUH in the well Long 8 of the 1 HFWLRQVRIWKH3HUPLDQDRNRX0 obtained and listed as follows: the GTI is 0.339; the KTI is )RUPDWLRQLV$IWHUFRQYHUVLRQLWVYLWULQLWHUHÀHFWDQFH $OOWKHGDWDLQGLFDWHWKDWWKHQDWXUDOJDVRULJLQDWHGIUR P LV7KHFDOFXODWHGPDWXULW\RIWKHVRXUFHURFNVZKLFK WKHUHODWLYHO\KLJKTXDOLW\VRXUFHURFNV2QWKHEDVLVRIRXU formed the methane found in the well is not in agreement C ,‰ 2 10 Pet.Sci.(2013)10:1-18 ZLWKWKHPHDVXUHGPDWXULW\RIWKHVRXUFHURFNVIURPWKH such a reversal is due to a higher degree of maturity. Instead, 3HUPLDQ0DRNRX)RUPDWLRQEXWLWLVFORVHUWRWKHPDWXULW\ we consider it is due to the mixing of sources. RIWKHVRXUFHURFNVIURPWKHLOXULDQ6PXGURFNV7KHYLWULQLWH The carbon isotopes of the natural gas generated from UHÀHFWDQFHRIWKHVRXUFHURFNVIURPWKHLOXULDQ6LQWKHVWXG\ Carboniferous of Jiannan gas field are lighter. The average 13 13 DUHDLV /LXHWDO 7KHQDWXUDOJDVIURPWKH C C 1 2 Long 8 well in P m Formation is a mixed product from both HTXDOVWRRULVOHVVWKDQÅZKLFKLVREYLRXVO\OLJKWHU Silurian mudstones and Permian carbonates sources. than those of the natural gas samples from the Permian, the Triassic and the Carboniferous of eastern Sichuan. The 4.3 Organic geochemical tracers in marine strata of natural gas in eastern Sichuan is mainly generated from the Jiannan structure 6LOXULDQRXUFHVURFNV =KXHWDO 7KHQDWXUDOJDVIURP the Carboniferous of Jiannan might be the product of the 7KHQDWXUDOJDVGU\LQJFRHI¿FLHQW & /C -C ) of the four 1 1 5 PL[LQJRIJDVIURPRWKHURXUFHVURFNVVXFKDVWKH&DPEULDQ production formations (Jialingjiang, Feixianguan, Changxing VRXUFHURFNVDWWKHGHHSHUSDUWRUWKHRWKHUSDUWVRIWKH DQG+XDQJORQJ LQ-LDQQDQJDVILHOGLVDERYHZLWKD formation. The reversal of the carbon isotope of the natural PD[LPXPYDOXHRILQGLFDWLQJDQRYHUPDWXUHGU\JDV gas also occurs. 7KHQDWXUDOJDVLQ&DUERQLIHURXVURFNVKDVDUHODWLYHO\KLJK R7VWXG\WKHVRXUFHURFNVLQJUHDWHUGHWDLOZHXVHGWKH C FRQWHQWZLWKDVPDOOTXDQWLW\RI&   DQG 2 3 FDUERQLVRWRSHYDOXHVRIWKHNHURJHQLQYDULRXVVHWVRIVRXUFH its CO DQG+ 6FRQWHQWVDUHERWKEHORZDEOH 7 2 2 URFNVLQWKHHDVW6LFKXDQ%DVLQDQGFRPSDUHGWKHPZLWK 7KHFRPSRVLWLRQVRIQDWXUDOJDVLQYDULRXVKRUL]RQVRIWKH WKHį C RIQDWXUDOJDVLQWKH-LDQQDQJDV¿HOG )LJ 7KH -LDQQDQJDV¿HOGHUHZEDVLFDOO\WKHDPHVZLWKDKLJKFRQWHQW 1 NHURJHQLQOLPHVWRQHVDPSOHVRI3 l, P T3 m, and P w was of methane and low contents of ethane, propane, and other 1 1 1 2 DPL[HGW\SHZLWKWKHDYHUDJHį C between -26.8‰ heavy hydrocarbon components, showing it is post-mature NHURJHQ DQGÅZKLFKLVÅÅKHDYLHUWKDQWKHį C value S\URO\VLVJDV+RZHYHUVXFKFRPSRQHQWFKDUDFWHULVWLFVDUH 1 in T f in the northern high point (-30.8‰ - -32.1‰), which IHUHQFHVLQJHQHVLVXQDEOHWRUHÀHFWGLI 1 corresponds to the fractionation during the alteration from The isotope ratios of methane in the natural gas from NHURJHQWR&+ . The natural gas of the T f Formation in the the P m, P ch and T f formations in the Jiannan gas field 4 1 1 2 1 QRUWKHUQKLJKSRLQWRULJLQDWHGIURPPL[HGW\SHRXUFHVURFNV DUHKLJKEHWZHHQDQGZKLFKLQGLFDWHVWKDWWKH classified as mainly sapropelic. The shale in P l, P w, and evolutionary degree of the natural gas is high. In comparison, 2 2 P d and the bioclastic limestone in P ch were humic with a WKHLUHWKDQHLVRWRSHVDUHZLGHO\GLVWULEXWHGZLWKVWULNLQJ 2 2 VLJQL¿FDQWO\KHDY\į C value, the average of which was differences being displayed in the high points of the south and NHURJHQ betweenÅDQGÅ7KHį C value in these WKHQRUWK7KHį C in the high point of the north is heavier, NHURJHQ IRXUIRUPDWLRQVZDVÅÅKHDYLHUWKDQWKHį C value in ZLWKDQDYHUDJHYDOXHRIZKLFKXJJHVWVVWKDWPRVWRI 1 the Permian and Triassic natural gas with the maximum at the natural gas is from humus-bearing sapropels, with only a 10‰, indicating that these four formations are not the source few exceptions, some of which might be sapropelic gas. The of the Permian and Triassic natural gas in the Jiannan gas į C in the high point of the south is lighter, with an average ¿HOG)RUWKLVUHDVRQLWFDQEHDVVXPHGWKDWWKHQDWXUDOJDV YDOXHRIZKLFKVXJJHVWVWKDWWKHQDWXUDOJDVLV from the Permian and the Triassic in the Jiannan gas field VDSURSHOLFJDV )LJDEOHDQG 7$OOWKHGDWDLQGLFDWHWKDW the genesis and the sources of the natural gas are complicated. 13 13 )URPWKHFURVVSORWRIį C DQGį C (Fig. 5), it can be seen 1 2 that the distribution of carbon isotopes of the natural gas T j 3 1 T f from the P ch and T f IRUPDWLRQVLQWKH-LDQQDQJDV¿HOGDQG 2 1 III -31.8 the distribution of carbon isotopes of the natural gas from -32.3 P d P ch -32.4 the Carboniferous in eastern Sichuan basically overlap but -25.2 P ch 2 II some differences are shown in the distribution of the carbon P w P m -32.7 isotopes of the natural gas from T f and P ch formations in the 1 2 -25.1 -23.2 -26.8 P l LQHDVWHUQ6LFKXDQLVPDLQO\IURPVDSURSHOLFVRXUFHURFNV -24.2 -23.5 P l P q-P m from the lower part of the Silurian system (Dai et al, 2010), 2 1 1 the natural gas from the P ch and T f formations in the -28.3 2 1 -27.5 -36.8 O -S 3 1 -29.5 SDUWRIWKH6LOXULDQV\VWHP+RZHYHUWKHFRQWULEXWLRQRI VRXUFHURFNVIURPWKH3HUPLDQV\VWHPFDQQRWEHLJQRUHG7KH -31.6 higher ethane carbon isotope ratios of the gas samples from the north points of P ch and T f formations indicate a greater 2 1 -40 -38 -36 -34 -32 -30 -28 -26 -24 -22 -20 FRQWULEXWLRQIURPWKH3HUPLDQVRXUFHURFNV+XPLFJDVLV į C, ‰ even found in the well No.51 in T f Formation of Jiannan gas Natural gas Kerogen type Type I Type II Type III Coal methane ¿HOG7KHUHYHUVDORIWKHFDUERQLVRWRSHVRIWKHJDVIURP3 ch and T f formations of Jiannan gas field mostly occurs, the Fig. 6&RPSDULVRQRIį C of the natural gas in the Longjuba structure and 1 1 -LDQQDQJDV¿HOGDQGį C LQVRXUFHURFNVLQWKHHDVWHUQ6LFKXDQ%DVLQ only difference being the degree. Some scholars maintain that NHURJHQ LVDOVRPDLQO\IURPVRXUFHURFNVRIWKHORZHU -LDQQDQJDV¿HOG RWKHUSDUWVRIWKHDUHD$VWKHQDWXUDOJDVLQWKH&DUERQLIHURXV LVÅDQGWKHDYHUDJHYDOXHRIWKHį YDOXHRIWKHį Pet.Sci.(2013)10:1-18 11 LVJHQHUDWHGPDLQO\IURP6LOXULDQVRXUFHURFNVDQGSDUWRI bearing series. The natural gas from the Carboniferous LWLVJHQHUDWHGIURP3HUPLDQPL[HGVRXUFHURFNVPDLQO\ IRUPDWLRQVZDVPDLQO\JHQHUDWHGLQWKHVRXUFHURFNVRIWKH VDSURSHOLFVRXUFHURFNV7KH3HUPLDQKXPXVEHDULQJVRXUFH 6LOXULDQV\VWHPDQGWKH&DPEULDQVRXUFHURFNVKDYHDOVR URFNVKDYHPDGHOHVVFRQWULEXWLRQWRWKHIRUPDWLRQRIWKH contributed to it. QDWXUDOJDVRIWKHDUHD7KHDYHUDJHį C values of the NHURJHQ 5 Fluid migration paths UHVSHFWLYHO\VRFODVVL¿HGDVVDSURSHOLFNHURJHQ7KHQDWXUDO To more accurately trace the fluid migration paths, a gas in the Carboniferous is typical sapropelic natural gas with SUR¿OHZDVVHOHFWHGIURPDQ[LDQ:QRUWKZHVWWR;LDRTLQJ\D LWVį C value below -40‰; its gas sources are the sapropelic southeast that essentially includes the Fangdoushan and VRXUFHURFNVLQWKH&DPEULDQDQGWKH6LOXULDQ 4L\XHVKDQIDXOW]RQHVWKH-LDQQDQVWUXFWXUHDQGRWKHU Comprehensive analysis shows that the natural gas in WHFWRQLF]RQHV7KURXJK )LJDQDO\VLV D RIÀXLGPLJUDWLRQ the Jiannan gas field is mainly sapropelic; that the natural SDWKVRIWKUHHW\SLFDOVWUXFWXUHV²;LQFKDQJ/RQJDQG gas from P ch and T f formations was mainly generated in Jian 38 wells, hydrocarbon accumulation and migration 2 1 were examined, the formation, evolution, destruction and VRXUFHURFNVDVLWVHFRQGDU\VVRXUFH$SHFL¿FVVDPSOHIURP modification of different structures were studied, and well No. 51 in T f Formation of Jiannan gas field displays hydrocarbon preservation conditions were evaluated in this VRPHUHODWLRQZLWKWKH3HUPLDQVRXUFHURFNVRIWKHFRDO area. (a) Regional cross-section Jiannan Xinchang Longjuba structure structure structure SE 0 10km Jian3 well Xinchang2 well Long8 well Depth, m J-T 5000 P Fangdoushan fault belt Qiyueshan fault belt Decollement fold zone of baffle structure in East Sichuan (c) Pathways of fluid movement in Longjuba structure (d) Pathways of fluid movement in Jiannan structure (b) Pathways of fluid movement in Xinchang structure Elevation, m Xinchang2 well Elevation, m Long8 well Elevation, m Jian38 well 0 0 1000 T T C 6000 O 4000 O C 8000 D+C Formation and Fluid charge Fluid charge Reverse fault in early period stratigraphic unit in late period )OXLGPLJUDWLRQSDWKVLQPDULQHVWUDWDRIWKHZHVWHUQ+XEHL±HD VWHUQ&KRQJTLQJDUHD Fig. 7 5.1 Fluid migration path in Xinchang structure of strontium isotopic ratio used in this study is applicable to rRFNVLQVRXWKHUQ&KLQD 87 86 The Sr/ Sr value of normal paleo-seawater in the $FFRUGLQJWRVWXGLHVRQFDUERQR[\JHQDQGVWURQWLXP Early Triassic (the similar sedimentary age of Jialingjiang isotopes in the Permian Changxing Formation of well )RUPDWLRQ VLPXODWHGE\0F$UWKXU  DQG.RUWHHW ;LQFKDQJDEOH 7 VLJQL¿FDQWIHUHQFHVGLIZHUHREVHUYHG al (2005a; 2005b) ranged from 0.7076 to 0.7082; that of LQWKHR[\JHQLVRWRSHVDQGZHDNGLIIHUHQFHVZHUHREVHUYHG seawater (the similar sedimentary age of Daye Formation) in carbon isotopes. These studies implied that the fluids VLPXODWHGE\5HLQKDUGWHWDO  HL]HUDQG9HWDO leading to vein formation were not sourced from the products ranged from 0.7076 to 0.7078; and that of Early Permian RIDGMDFHQWVXUURXQGLQJURFNVDIWHUUHGLVVROXWLRQ+RZHYHU 87 86 QRUPDOVHDZDWHUUDQJHGIURPWR$QDO\VLVZDV the Sr/ Sr value of gypsum filling spaces in the Permian performed on strontium isotopic composition and evolution Changxing Formation (0.7100) was close to the strontium RI/DWHULDVVLF3HUPLDQí(DUO\7VHDZDWHULQPDULQHFDUERQDWH isotope of Early Cambrian seawater, which was reported as URFNVLQ=KRQJOLDQJVKDQ&KRQJTLQJUHSRUWHGE\+XDQJHWDO %XUNHHWDOHQLVRQ'HWDOKL6HW (2008). The conclusions were consistent with those published DORUWH.HWDO 7KHVHUHVXOWVLQGLFDWHWKDWÀXLGV by Korte et al (2003; 2005a; 2005b), proving that the criterion leading to the formation of gypsum were sourced from lower 6LOXULDQVRXUFHURFNVZLWK3HUPLDQKXPXVEHDULQJVDSURSHOLF NHURJHQLQWKH&DPEULDQDQG6LOXULDQDUHÅDQGÅ 12 Pet.Sci.(2013)10:1-18 Cambrian strata. 5.2 Fluid migration path in Longjuba structure Previously accumulated calcium-carbonate-rich fluids $QDO\VLVRIFDUERQDQGR[\JHQLVRWRSHVIURPWKH3HUPLDQ ZHUHVRXUFHGIURP3HUPLDQURFNVZLWKDEXQGDQWRUJDQLF in the well Long 8, indicated that although carbon and inclusions (Fig. 9(a)), indicating that the Permian source URFNVUHDFKHGWKHSHDNRIK\GURFDUERQJHQHUDWLRQDWWKLV Bitumen VWDJH7KHKRPRJHQL]DWLRQWHPSHUDWXUHSHDNVRIFRH[LVWLQJ saline inclusions were 120-130 °C and 160-190 °C (Fig. 9(b)), corresponding to the depths of hydrocarbon migration and accumulation at 3,333-3,667 m and 4,666-5,667 m, UHVSHFWLYHO\$FFRUGLQJWRWKHK\GURFDUERQJHQHUDWLRQ KLVWRU\RI8SSHU3HUPLDQVRXUFHURFNVVLPXODWHGE\WKH (DV\ R FKHPLFDONLQHWLFPRGHO )LJ D WKH R value o o RIVRXUFHURFNVUDQJHGIURPWRLQWKHPLGGOH /DWHULDVVLF7WKHURFNVZHUHEXULHGPLQWKLVVWDJH of abundant hydrocarbon generation. In the initial Early -XUDVVLFWKHPDWXULW\RIWKHVRXUFHURFNVZDVDERXW Calcite DWZKLFKVWDJHK\GURFDUERQJHQHUDWLRQUHDFKHGLWVSHDN,Q (a) WKHPLGGOH(DUO\-XUDVVLFWKHPDWXULW\RIVRXUFHURFNVZDV DWZKLFKVWDJHJDVJHQHUDWLRQRFFXUUHG,QWKHODWH Early Jurassic, R YDOXHZDVDWZKLFKWDJHVVLJQL¿FDQW JDVJHQHUDWLRQRFFXUUHGLQHUPLDQ3RXUFHVURFNV0HDQZKLOH Gypsum LQFOXVLRQFKDUDFWHULVWLFVDQGKRPRJHQL]DWLRQWHPSHUDWXUHV also show that two-stage hydrocarbons were captured in Permian reservoirs (P ch ) in the initial and the late epochs of the Early Jurassic. 5HVLGXDOELRPDUNHUFKDUDFWHULVWLFVRIRUJDQLFPDWWHU obtained from the fractures of the third member of Feixianguan Formation, show its source was Permian source URFNV7KHWLPHRIIRUPDWLRQRIWKHJDQLFRUPDWWHUOOLQJ¿WKH UHVHUYRLUIUDFWXUHVVKRXOGEHHTXLYDOHQWWRWKHFDSWXUHWLPH Calcite of vein inclusions in reservoir fractures of the lower Triassic Feixianguan Formation because both have the same set of VRXUFHURFNV )LJ D (b) 7KHJ\SVXPOOLQJ¿WKHUHVHUYRLUIUDFWXUHVRIWKH3HUPLDQ Changxing Formation has been proved to be sourced from WKHXQGHUO\LQJ&DPEULDQ$ODUJHDPRXQWRIZDWHUVROXEOH 02cm methane exists in the inclusions along indistinct fractures in J\SVXP )LJ F LQGLFDWLQJWKDW&DPEULDQVRXUFHURFNV evolved to hydrocarbon expulsion with a high maturity or to a generation stage of abundant dry gas. The vein-filling VHTXHQFHVKRZVWKHIRUPDWLRQRIJ\SVXPDVZODWHUWKDQWKDW RIWKHFDOFLWH )LJ E $JHODUDPRXQWRIQDWXUDOJDVDQG calcium-sulfate-rich water generated in Cambrian source URFNVPLJUDWHGWRWKHRYHUO\LQJ3HUPLDQUHVHUYRLUVWKHPDLQ pathway of which was probably faults and fractures generated by Yanshan tectonism. In addition, the residual organic ELRPDUNHUVDORQJ&DUERQLIHURXVUHVHUYRLUIUDFWXUHVKDYH FKDUDFWHULVWLFVRI&DPEULDQDQG6LOXULDQVRXUFHURFNV $WOHDVWWZRVWDJHVRIÀXLGDFFXPXODWLRQRFFXUUHGLQWKH Bitumen Calcite 3HUPLDQUHVHUYRLUVRIWKH;LQFKDQJVWUXFWXUH )LJ E $W (c) WKHHDUO\WDJHVWKHFDOFLXPFDUERQDWHULFKXLGÀZDVVRXUFHG IURPWKH3HUPLDQDQGIRUPHGWKHFDOFLWH$WWKHODWHVWDJH &RUHSKRWRVRIZHOO;LQFKDQJDQGZHOO-LDQ D 7KH Fig. 8 YHLQ¿OOLQJVHTXHQFHRIWKHUHVHUYRLULQULDVVLF/RZHU7HL[LD) QJXDQ WKHFDOFLXPVXOIDWHULFKXLGÀZDVVRXUFHGIURPWKH&DPEULDQ )RUPDWLRQ DWWKHGHSWKRIP RIWKH;LQFKDQJZHOO WKH DQGIRUPHGWKHJ\SVXP0RUHRYHUWKHODWHUDFFXPXODWHG FDOFLWHILOOHGEHIRUHWKHELWXPHQ  E 7KHYHLQILOOLQJVHTXHQ FHRI ÀXLGVPDGHFHUWDLQPRGL¿FDWLRQVWRWKHÀXLGVJHGHDUOLHUFKDU the reservoir in Upper Permian, Changxing Formation (at the depth Earlier hydrocarbon preservation conditions were damaged RIP RIWKH;LQFKDQJZHOO WKHFDOFLWH¿OOHGEHIRUH WKH JHVFDOHFURVVIRUPDWLRQDOÀRZRIE\WKHORQJGLVWDQFHDQGODU J\SVXP  F 7KHYHLQILOOLQJVHTXHQFHRIWKHUHVHUYRLULQ/RZH U ÀXLGVOHDGLQJWRHULRXVVSUREOHPVIRURLODQGJDVH[SORUDWLRQ Triassic, Feixianguan Formation (at the depth of 3,151.42 m) of the LQWKH;LQFKDQJVWUXFWXUH -LDQZHOO WKHFDOFLWH¿OOHGEHIRUHWKHELWXPHQ  Pet.Sci.(2013)10:1-18 13 P m 4784.48 m 140-150 °C V- V- LL (e) 2914.97 (a) 25% 2608.1 20% 2755.77 2637.8 2682.04 2880.05 2775.94 2826.06 2650.07 2741.47 2863.19 2810.9 15% 2650 2700 2750 2800 2850 2900 2950 -1 Raman shift, cm 10% (f) 5% 0% Homogenization temperature, °C (b) 2912.07 (g) 70% 999.762 2604.96 60% 50% 40% 1158.55 30% 20% 1000 1500 2000 2500 3000 -1 10% Raman shift, cm 0% (c) 130-135 135-145 140-145 145-150 Homogenization temperature, °C P ch (h) 4314.67 m 130-170 °C 2914.2 V-L 1086.64 LCH -H S 4 2 1000 1500 2000 2500 3000 LCH 4 -1 Raman shift, cm (d) (i) Fig. 9KRWRV3KRPRJHQL]DWLRQWHPSHUDWXUHDQGODVHU5DPDQSHFWUDVRIÀXLGLQFOXVLRQV D 7KHJDQLFRUÀXLGLQFOXVLRQVRIFDOFLWHVYHLQLQHUPLDQ3UHVHUYRLU IUDFWXUHVRIVDPSOH ;&P3 FK ;LQFKDQJZHOO E +RPRJHQL]DWLRQWHPSHUDWXUHGLVWULEXWLRQGLDJUDPRIÀXLGLQFOXVLRQVLQFDOFLWHYHLQV RI3HUPLDQUHVHUYRLUV DWWKHGHSWKRIP RIWKHDQJ;LQFKZHOO F /DVHU5DPDQSHFWUDVRIJDQLFRULQFOXVLRQVLQHWKVHFRQGPHPEHURIWKH8SSHU Permian Changxing Formation (P ch RIWKH;LQFKDQJZHOO G )OXLGLQFOXVLRQVLQFDOFLWHYHLQV ¿OOLQJUHVHUYRLUIUDFWXUHVRIWKH&KDQJ[LQJ)RUPDWLRQ /RQJZHOO H )OXLGLQFOXVLRQVRIFDOFLWHYHLQV¿OOLQJ3HUPL DQUHVHUYRLUIUDFWXUHVRIWKH0DRNRX)RUPDWLRQZHOO/RQJ /DVHU I5DPDQSHFWUDJDQLFVRIRU LQFOXVLRQVLQWKHYHLQVRIWKH0DRNRX)RUPDWLRQZHOO/RQJ J *DVOLTXLGVDOLQHLQFOXVLRQVFRH[LVWLQJZLWKRUJDQLFLQFOXVLRQVZKLFKDUHGDUNJUD\ VLQJOHSKDVHGDQGLQWKHKDSHVRIUHFWDQJOHDOLQH6LQFOXVLRQVDUHOLTXLGDQGJDVSKDVHGKRUL]RQ7 f GHSWKPHOOZ-LDQ K +RPRJHQL]DWLRQ WHPSHUDWXUHGLVWULEXWLRQGLDJUDPRIÀXLGLQFOXVLRQVLQWKHWKLUGPHPEHURIWKH/RZHUULDVVLF7)HL[LDQJXDQ)RUPDWLRQ 7 f ) of the well Jian 38. (i) Laser 3 -1 -1 Raman spectra of organic inclusions in the third member of Lower Triassic Feixianguan Formation (T f ) of the well Jian 38; 2914.2 cm and 1086.64 cm UHIHUWR&+ LQWKLV¿JXUHDQGFDOFLWHUHVSHFWLYHO\ 90-100 100-110 110-120 120-130 130-140 140-150 150-160 160-170 170-180 180-190 190-200 200-210 Counts Counts Counts 14 Pet.Sci.(2013)10:1-18 400 360 320 280 240 200 160 120 80 40 0 Time, Ma Depth, PALEOZOIC MESOZOIC CENOZOIC Fm Pg Ng SD C P Tr J K T x 1000 3 0.40%R T b 0.60%R T j T f P ch P m P q 0.80%R S h S x 1.20ˁR S l 1.60ˁR 2.00ˁR 2.40ˁR 2.80ˁR (a) 400 360 320 280 240 200 160 120 80 40 0 Time, Ma Depth, CENOZOIC PALEOZOIC MESOZOIC Fm SD C P Tr J K Pg Ng T x T b 0.40%R T j T f 4000 1 0.80%R P ch P m P q 5000 1 S h 1.20%R S x o 1 S l 1.60%R 1 2.00%R 2.40%R 2.80%R 3.20%R (b) %XULDOKLVWRU\DQGK\GURFDUERQJHQHUDWLRQKLVWRU\RIVRXUFHURFNV Fig. 10 R[\JHQLVRWRSHVRIYHLQVDQGVXUURXQGLQJURFNVUDQJHGLQWKH respectively; those of P ch ranged from -1.5‰ to 4.5‰ and VFRSHRIQRUPDOVHDZDWHUGXULQJWKHVDPHSHULRGį C and from -6.5‰ to 0‰, respectively (Korte et al, 2005a; 2005b). į O of P m ranged from -2‰ to 6‰ and from 6‰ to 0‰, +RZHYHUVLJQL¿FDQWIHUHQFHVGLIH[LVWLQFDUERQDQGR[\JHQ 1 Pet.Sci.(2013)10:1-18 15 DEOHLVRWRSHVEHWZHHQ3HUPLDQYHLQVDQGVXUURXQGLQJURFNV 7 through petrography. The accumulation of Permian fluids 6). It was shown that the fluids leading to the formation of was prior to that of hydrocarbons generated in the underlying veins were not directly sourced from the fluids of adjacent 6LOXULDQVRXUFHURFNV,IWKHDFFXPXODWLRQRIK\GURFDUERQV VXUURXQGLQJURFNV7KHIOXLGVILOOLQJWKHIUDFWXUHVRIWKH JHQHUDWHGLQWKHVHVRXUFHURFNVZDVHDUOLHUWKHQWUDFHVRI 0DRNRX)RUPDWLRQ 3 m) and Changxing Formation (P ch ) 6LOXULDQÀXLGVVKRXOGEHUHWDLQHGLQWKH3HUPLDQFDOFLWHYHLQV 1 2 87 86 had Sr/ Sr values of 0.7071, within the strontium isotope 7KHUHIRUHWKHDFFXPXODWLRQRI6LOXULDQXLGVÀDVZODWHUIURP UDQJHRI/DWH3HUPLDQVHDZDWHU %XUNHHWDO'HQLVRQ short-distance cross-formational migration of natural gas to HWDO6KLHWDO.RUWHHWDO 7KLV¿QGLQJ the Permian reservoirs. Tectonism was not very intense, and indicates that the fluids in Lower Permian were sourced the faults and fractures were only able to connect the Silurian from the overlying Upper Permian. The fluids in the Upper DQG3HUPLDQXLGV7KHÀVLJQL¿FDQWO\GHHS3HUPLDQUHVHUYRLUV Permian were not directly sourced from adjacent surrounding DQGWKLFNRYHUO\LQJJ\SVXPKDOLWHEHGVDOORZHGK\GURFDUERQ URFNVEXWIURPRWKHUSDUWVLQ3HUPLDQUHVHUYRLUV preservation conditions to partially remain in this structure. $OOIOXLGVRIYHLQVILOOLQJ3HUPLDQUHVHUYRLUVRIWKHZHOO Exploration results have shown Longjuba to be a gas-bearing Long 8 were sourced from the Late Permian. The inclusions structure. in calcite veins of Changxing Formation samples (4,314.67 5.3 Fluid migration path in the Jiannan structure P FRQVLVWHGRIJDVOLTXLGVDOLQHZDWHUVROXEOH&+ + S, 4 2 DQG&+ inclusions (Fig. 9(d)). These results indicate that 4 'U\EODFNELWXPHQZDVGLVFRYHUHGLQFDOFLWHYHLQV¿OOLQJ ÀXLGDFFXPXODWLRQRFFXUUHGDWWKHSHDNWDJHVRIK\GURFDUERQ micrite fractures adjacent to the third-member Lower Triassic JHQHUDWLRQDWZKLFKWLPHWKHKRPRJHQL]DWLRQWHPSHUDWXUH Feixianguan Formation of the well Jian 38 in the Jiannan of coexisting saline inclusions ranged between 130 °C VWUXFWXUH P 7KHFDOFLWHZDV¿OOHG¿UVWIROORZHG and 170 °C, corresponding to hydrocarbon migration and by bitumen, leading to a significant time order with a vein accumulation depths between 3,667 m and 5,000 m. width of 2-4 mm. Carbon, oxygen, and strontium isotopes The fluid inclusions in calcite veins filling the reservoir RIYHLQVDQGVXUURXQGLQJURFNVLQWKLVIRUPDWLRQZHUHLQWKH fractures of the first member of the Lower Permian UDQJHRI(DUO\ULDVVLF7 QRUPDOVHDZDWHUDEOH 7  %XUNH 0DRNRX)RUPDWLRQ P PDLQO\FRQVLVWHGRIJDV HWDO'HQLVRQHWDO LQGLFDWLQJQRLQÀXHQFHRQ OLTXLGRUJDQLFLQFOXVLRQV )LJ H  I DWZKLFKWLPHWKH WKHVHLVRWRSHVLQVXUURXQGLQJURFNVDQGYHLQV+RZHYHU KRPRJHQL]DWLRQWHPSHUDWXUHSHDNUDQJHGEHWZHHQƒ& VLJQL¿FDQWIHUHQFHVGLIH[LVWHGLQFDUERQDQGR[\JHQLVRWRSHV and 150 °C and the hydrocarbon accumulation depth was EHWZHHQYHLQVDQGVXUURXQGLQJURFNV7KHIOXLGVOHDGLQJWR estimated at between 4,000 m and 4,330 m. The hydrocarbon the formation of veins were probably sourced from external 87 86 JHQHUDWLRQKLVWRU\RI3HUPLDQVRXUFHURFNVLQWKH/RQJ IOXLGVUDWKHUWKDQIURPWKHVXUURXQGLQJURFNV7KH Sr/ Sr well (Fig. 10(b)), indicates that hydrocarbon generation YDOXHRIWKHVXUURXQGLQJURFNV  ZDVFRQVLVWHQW RFFXUUHGLQHUPLDQ3RXUFHVURFNVLQWKHODWH0LGGOHULDVVLF7 with that of Early Triassic normal seawater (0.7076), which DQGUHDFKHGWKHSHDNVWDJHLQWKHHDUO\/DWHULDVVLF7ZLWKD LQGLFDWHVWKDWWKHVXUURXQGLQJURFNVZHUHQRWLQIOXHQFHGE\ corresponding R YDOXHRI*DVJHQHUDWLRQEHJDQLQWKH o H[WHUQDOÀXLGVZKLOHPRUHVWURQWLXPLVRWRSLFFKDUDFWHULVWLFV ODWH0LGGOH-XUDVVLFZLWKDFRUUHVSRQGLQJ R YDOXHRI o of seawater in the original sedimentation were retained. The 87 86 )URPWKHLQFOXVLRQFKDUDFWHULVWLFVDQGKRPRJHQL]DWLRQ Sr/ Sr value of veins (0.7075) was also close to the high 87 86 temperatures, we deduce that hydrocarbons were primarily value of Sr/ Sr in Late Permian seawater (0.7067-0.7076), captured in the Permian reservoirs of the well Long 8 during indicating that the fluids leading to the formation of veins WKHHDUO\0LGGOH-XUDVVLF+RZHYHUWKHFRPSRVLWLRQDQG could be sourced from the Lower Triassic and the Upper isotopic characteristics of natural gas in the Permian in this Permian strata. well suggest that the natural gas is mainly from Silurian and 3HUPLDQVRXUFHURFNV7KHUHIRUHPXOWLVRXUFHDQGPXOWL limestone fractures of the third-member (T f ) Lower Triassic stage hydrocarbons were captured in Permian reservoirs. Feixianguan Formation (3,153.20 m) mainly consisted of gas- The Permian reservoirs of the Longjuba structure were OLTXLGDQGJDQLFRULQFOXVLRQV )LJ J 7KHJDVOLTXLGÀXLG PDLQO\FKDUDFWHUL]HGE\WZRVWDJHIOXLGDFFXPXODWLRQ LQFOXVLRQVZHUHȝPLQVL]HDQGWKHKRPRJHQL]DWLRQ (Fig. 7(c)). One stage was the accumulation process of temperature ranged between 132 °C and 148 °C (the WKH8SSHU3HUPLDQFDOFLXPVXOIDWHULFKIOXLGVDQGOLTXLG KRPRJHQL]DWLRQWHPSHUDWXUHSHDNUDQJHGEHWZHHQƒ& hydrocarbon fluids. Strontium, carbon, and oxygen isotopic and 145 °C (Fig. 9(h))). Temperature measurement and laser characteristics of calcite veins filling the reservoir fractures Raman spectroscopy revealed that the organic inclusions RIWKH&KDQJ[LQJDQG0DRNRXIRUPDWLRQVUHYHDOHGWKDWWKH mainly consisted of water-soluble methane (Fig. 9(i)), while fluids of calcite veins were mainly sourced from the Upper + S was contained in some inclusions. Calcite veins were Permian, and the inclusions in calcite veins mainly consisted ULFKLQZDWHUVROXEOHPHWKDQHLQFOXVLRQVEXWODFNHGOLTXLG RIJDVOLTXLGJH7KHLQFOXVLRQVÀXLGRFFXUUHGFKDUDWWKHSHDN petroleum inclusions. Thus, the charge of fluids leading to of hydrocarbon generation, and hydrocarbons were sourced WKHIRUPDWLRQRIFDOFLWHYHLQVOLNHO\RFFXUUHGDIWHUSHWUROHXP IURPWKH8SSHU3HUPLDQVRXUFHURFNV0RUHRYHUDQDO\VLVRI pyrolysis. Calcite was mainly distributed at the fracture edges, natural gas in Permian reservoirs revealed the other stage of and sparse dry bitumen was distributed in the center of the IOXLGDFFXPXODWLRQZDVPDLQO\IURP6LOXULDQVRXUFHURFNV IUDFWXUHV7KXVWKHELWXPHQLQWKHFHQWHURIIUDFWXUHVOLNHO\ DQGSDUWIURP3HUPLDQVRXUFHURFNV7KHWLPHRUGHURIWKH HQWHUHGWKHIDFWXUHVDWWKHVDPHWLPHDVWKHÀXLGVOHDGLQJWR two-stage fluid accumulation was unable to be determined WKHIRUPDWLRQRIFDOFLWH¿QDOO\VHWWOLQJLQWKHUHVLGXDOVSDFH 7KHÀXLGLQFOXVLRQVRIFDOFLWHYHLQV¿OOLQJWKHVXUURXQGLQJ 16 Pet.Sci.(2013)10:1-18 (Fig. 8(c)). VRXUFHURFNV$IDYRUDEOHVRXUFHUHVHUYRLUDVVHPEODJHZDV $QDO\VLVRIFDUERQR[\JHQDQGVWURQWLXPLVRWRSHV IRUPHGEHWZHHQ6LOXULDQVRXUFHURFNVDQG&DUERQLIHURXV RIYHLQVDQGVXUURXQGLQJURFNVLQWKH/RZHU7ULDVVLF Feixianguan Formation revealed that the original fluids ,QWKH-LDQQDQVWUXFWXUHGXULQJDQVKDQ< DQG+LPDOD\DQ OHDGLQJWRWKHIRUPDWLRQRIYHLQVZHUHPRVWOLNHO\VRXUFHG WHFWRQLVPWKHWUDSVRIYDULRXVKRUL]RQVUHPDLQHGLQWDFWDQG IURPWKH/RZHUULDVVLF7 RU8SSHU3HUPLDQ+RZHYHUWKH no long-distance cross-formational accumulation of Cambrian Lower Triassic Feixianguan had no potential for hydrocarbon IOXLGVRFFXUUHGLQWKH3HUPLDQUHVHUYRLUV$FFRUGLQJO\WKH JHQHUDWLRQLQGLFDWLQJWKDWWKHZDWHUVROXEOHPHWKDQH¿OOLQJ hydrocarbon preservation conditions were excellent, and WKHIUDFWXUHVZHUHOLNHO\VRXUFHGIURPRWKHUVWUDWDEHORZ Jiannan gas field was discovered with vertical development the Feixianguan Formation. Drilling data from the Jianghan RIJDVUHVHUYRLUVLQWKH&DUERQLIHURXV+XDQJORQJ3HUPLDQ Oilfield indicate that natural gas was discovered in both Changxing, and the Triassic Feixianguan and Jialingjiang the underlying Upper Permian and Lower Permian strata, formations. showing that the natural gas in Feixianguan gas reservoirs Through the study of organic geochemical tracers in could have the same hydrocarbon source as that of the marine strata of the three typical structures, the differences underlying Permian reservoirs. RIWKHIOXLGPRYHPHQWKDYHEHHQIXOO\UHFRJQL]HGDQGWKH On the basis of the above analysis, gas sources of the 3HUPLDQDQGULDVVLF7QDWXUDOJDVLQ-LDQQDQJDV¿HOGPDLQO\ VWUXFWXUHVKDYHDOVREHHQDQDO\]HG 7DEOH 7KHODWHU LQFOXGH3HUPLDQFDUERQDWHVRXUFHURFNVDQGFRDOPHDVXUH accumulation of the Silurian and Cambrian fluids occurred Q in the Carboniferous, Permian, and Triassic reservoirs. the case of earlier favorable preservation conditions, vertical In the case of a long-distance and large-scale cross- migration occurred in part of the natural gas generated in the formational migration occurring in deep Cambrian fluids, 6LOXULDQRXUFHVURFNVEXWGLGQRWUHDFKWKHHQWLUH)HL[LDQJXDQ ODWHUDFFXPXODWHGÀXLGVPRGL¿HGH[LVWLQJDFFXPXODWHGÀXLGV DQG-LDOLQJMLDQJIRUPDWLRQVLQWKH/RZHUULDVVLF70RVWRI resulting in the reduction of preservation conditions of earlier WKHÀXLGJHFKDURFFXUUHGRQO\LQWKHRYHUO\LQJ&DUERQLIHURXV accumulated hydrocarbons. This has created major problems +XDQJORQJ)RUPDWLRQ IRUH[SORUDWLRQLQHUPLDQ3VWUDWDLQWKH;LQFKDQJVWUXFWXUH,Q Traces of two-stage fluid migration and accumulation case of a short-distance cross-formational charge of Silurian were observed in the Jiannan gas field (Fig. 7(d)). One ÀXLGVWRWKH&DUERQLIHURXVDQG3HUPLDQUHVHUYRLUVRQO\ORFDO stage of fluid migration was the accumulation of calcium- modification occurred to the earlier closed and complete FDUERQDWHULFKÀXLGVZLWK3HUPLDQURFNVDVWKHLUVRXUFH$W preservation systems, which resulted in favorable hydrocarbon WKHVDPHWLPHDVLJQLILFDQWDPRXQWRIOLTXLGK\GURFDUERQV preservation conditions. Exploration has shown Longjuba JHQHUDWHGLQ3HUPLDQVRXUFHURFNVPLJUDWHGWRWKHULDVVLF7 is a gas-bearing structure. The Silurian and Cambrian fluid UHVHUYRLUV1RREYLRXVDFFXPXODWHGWUDFHVRIÀXLGVH[LVWHGLQ accumulation in the neighboring Carboniferous reservoirs did RWKHUKRUL]RQVZKLOHDIDYRUDEOHVRXUFHUHVHUYRLUDVVHPEODJH not reach the entire Permian reservoir; the Permian-Triassic ZDVIRUPHGDPRQJWKH3HUPLDQRXUFHVURFNVDQGWKH3HUPLDQ and the Silurian-Carboniferous source-reservoir assemblages 7KHRWKHUVWDJHRIÀXLGPLJUDWLRQZDVLDVVLFUHVHUYRLUVU7DQG were classified as two non-interfering fluid systems with shown as the accumulation of hydrocarbons into the overlying excellent hydrocarbon preservation conditions, leading to the Carboniferous reservoirs mainly generated in the Silurian H[SORUDWLRQDQGGLVFRYHU\RIWKH-LDQQDQJDV¿HOG Table 8G-LDQQDQVWUXFWXUHVDQGWKHLUH[SORUDWLRQVLWXDWLRQVIHUHQFHVRIWKHÀXLGPLJUDWLRQLQ;LQFKDQJ/RQJMXEDDQ7KHGLI The relation between the (DUO\ÀXLG /DWHÀXLG Distance between Exploration Structures Preservation hydrocarbon and the source accumulation accumulation the formation achievement 1) The Triassic residual organic matter comes from the Permian carbonate and FRDOPHDVXUHVRXUFHURFNV 2) The Permian residual organic matter Permian &DPEULDQĺ ORQJGLVWDQFH$ Overall ;LQFKDQJ is from the Permian coal-measure source None ULDVVLF7ĺ3HUPLDQ Permian cross-formational destruction URFNV 3) The Carboniferous residual organic matter is from the Silurian and &DPEULDQVRXUFHURFNV Small gas bearing 1) The Permian natural gas is from the VKRUWGLVWDQFH$ Partial Longjuba 3HUPLDQĺ3HUPLDQ 6LOXULDQĺ3HUPLDQ pools such as Longjuba 3HUPLDQDQGWKH6LOXULDQVRXUFHURFNV cross-formational destruction structure 1) The natural gas of the northern high Gas pools in the point comes from the Permian source +XDQJORQJ)RUPDWLRQRI URFNV 7KHÀXLG the Carboniferous, the 2) The Permian and the Triassic natural accumulation Cambrian, Silurian Changxing Formation of the Jiannan gas is derived from the Silurian source ULDVVLF3HUPLDQĺ7 from neighboring No destruction ĺ&DUERQLIHURXV Permian, the Feixianguan URFNV strata and Jialingjiang formations 3) The Carboniferous natural gas is from of the Triassic (Jiannan gas WKH6LOXULDQVRXUFHURFNVZLWKDVPDOO ¿HOG SDUWIURPWKH&DPEULDQVRXUFHURFNV VRXUFHURFNVLQDGGLWLRQWR6LOXULDQVRXUFHURFNV7KHUHIRUHL IRUPDWLRQHYROXWLRQPRGL¿FDWLRQDQGGHVWUXFWLRQRIGLIIHUHQW UHVHUYRLUVUHVXOWLQJLQDQDGGLWLRQDOLQGHSHQGHQWÀXLGV\VWHP Pet.Sci.(2013)10:1-18 17 reservoirs. SPE Reservoir Evaluation and Engineering. 2009. 12(1): 6 Conclusions 88-95 FOD\RUGHQ6$5:+3DUQHOO%DU-HWDO$VVHVVPHQWRIÀXLG FRQWDFWV $W OHDVWIRXUVHWVRIVRXUFHURFNVH[LVWHGLQWKHZHVWHUQ DQGFRPSDUWPHQWDOL]DWLRQLQVDQGVWRQHUHVHUYRLUVXVLQJIOXLG +XEHL±HDVWHUQ&KRQJTLQJDUHD3HUPLDQPDULQHFDUERQDWH LQFOXVLRQV$QH[DPSOHIURPWKH0DJQXV2LO)LHOG1RUWK6HD DQGFRDOPHDVXUHVRXUFHURFNVDQG6LOXULDQDQG&DPEULDQ $$3*%XOOHWLQ DUJLOODFHRXVVRXUFHURFNV7KHQDWXUDOJDVDQGWKHUHVLGXDO organic matter in the Triassic and the Permian strata showed RIJDVLQ$XVWUDOLDQ%RZHQ%DVLQFRDOV2UJDQLF*HRFKHPLVWU\ VLPLODUFKDUDFWHULVWLFVWRWKRVHRIWKH6LOXULDQVRXUFHURFNV 1998. 29(1-3): 347-362 WKH3HUPLDQPDULQHFDUERQDWHVRXUFHURFNVDQGWKHFRDO VHDZDWHUDULDWLRQRI9HWDO$+'HQLVRQ5(+HWKHULQJWRQ(:NH%XU 87 86 PHDVXUHVRXUFHURFNVZKLOHWKHQDWXUDOJDVDQGWKHUHVLGXDO Sr/ 6UWKURXJKRXW3KDQHUR]RLFWLPH*HRORJ\ organic matter in the Carboniferous reservoirs showed similar FKDUDFWHULVWLFVWRWKRVHRIWKH6LOXULDQVRXUFHURFNVZLWKD Q+'&KH3DQJ/1L;)HWDO1HZEULHIUHPDUNVRQK\GURFDUERQ VPDOOSDUWFRPLQJIURPWKH&DPEULDQVRXUFHURFNV DQJW]HSURVSHFWLQJUHRIPDULQHVWUDWDLQWKHPLGGOH<DQGXSSHU JLRQ Petroleum Geology and Experiment. 2007. 29(1): 13-18 (in Chinese) $WOHDVWWZRVWDJHVRIIOXLGDFFXPXODWLRQRFFXUUHG Q0&KH.([SORUDWLRQSRWHQWLDORIQDWXUDOJDVLQZHVWHUQ+XEH L± in Carboniferous-Triassic reservoirs in the study area. HDVWHUQ&KRQJTLQJDUHD-RXUQDORI-LDQJKDQ3HWUROHXP,QVWLWXWH Earlier marine strata above the Permian were shown with 2003. 25(1): 27-29 (in Chinese) DQDFFXPXODWLRQRIOLTXLGK\GURFDUERQVJHQHUDWLQJLQWKH -;'DL7KHLGHQWL¿FDWLRQRIDONDQHJDV6FLHQFHLQ&KLQD 6H ULHV% 3HUPLDQRXUFHVURFNVWRWKH3HUPLDQDQGWKH/RZHUULDVVLF7 1992. 2: 185-193 (in Chinese) reservoirs. This accumulation was considered as internal -;'DL1L<<DQG+XDQJ63'LVFXVVLRQRQWKHFDUERQLVRWRS LF fluid flow within the same relatively complete preservation UHYHUVDORIDONDQHJDVHVIURPWKH+XDQJORQJ)RUPDWLRQLQWKH system. The later accumulation of the Silurian and Cambrian 6LFKXDQ%DVLQ$FWD&KLQD3HWUROHL6LQLFD    LQ fluids occurred in the Carboniferous, Permian, and Triassic Chinese) reservoirs. In the case of a long-distance and large-scale 6'DL:+H=$DQGDQJ: -<7KLQNLQJRI0HVR3DOHR]RLF cross-formational migration occurring in deep Cambrian hydrocarbon exploration in South China. Oil and Gas Geology. 2001. 22(3): 195-202 (in Chinese) ÀXLGVODWHUDFFXPXODWHGÀXLGVPRGL¿HGH[LVWLQJDFFXPXODWHG LVRQ5HQ'(.RHSQLFN5%%XUNH:+HWDO&RQVWUXFWLRQRIWKH fluids, resulting in destruction of preservation conditions 87 86 0LVVLVVLSSLDQ3HQQV\OYDQLDQDQG3HUPLDQVHDZDWHU Sr/ Sr curve. of earlier accumulated hydrocarbons. In case of a short- Chemical Geology. 1994. 112(1-2): 145-167 distance cross-formational charge of Silurian fluids to the ODQG(JQ:$DQG0DFNHQ]LH$66RPHDVSHFWVRIWKHRUJDQLF geochemistry of petroleum fluids. Geologische Rundschau. 1989. occurred to the earlier closed and complete preservation 78(1): 291-303 systems. The Silurian and Cambrian fluid accumulation in ODQG:$(QJ0DFNHQ]LH$60DQQ'0HWDO7KHPRYHPHQWDQG the neighboring Carboniferous reservoirs did not reach the entrapment of petroleum fluids in the subsurface. Journal of the entire Permian reservoir; and the Permian-Triassic and the Geological Society. 1987. 144(2): 327-347 Silurian-Carboniferous source-reservoir assemblages were ODQG:$0XJJHULGJH$(QJ+ Clifford3-HWDO0RGHOOLQJGHQVLW\ FODVVL¿HGDVWZRQRQLQWHUIHULQJÀXLGV\VWHPVLWKZH[FHOOHQW driven mixing rates in petroleum reservoirs on geological time- scales, with application to the detection of barriers in the Forties hydrocarbon preservation conditions. Field (UKCS) (in the Geochemistry of Reservoirs). Geological 3) On the basis of studies of fluid migration paths in Society Special Publications. 1995. 86: 185-201 (in Chinese) marine strata and comparative analysis of the exploration Fu Z R, Li Z J and Zheng D Y. Structural pattern and tectonic evolution results, it was shown that intense late tectonism causing RI11(WUHQGLQJVWULNHVOLSRURJHQLFEHOWLQWKHERUGHUUHJLRQRI long-distance and large-scale cross-formational migration RIGHHS/RZHU3DOHR]RLFIOXLGVZDVFULWLFDOWRK\GURFDUERQ 272 (in Chinese) SUHVHUYDWLRQFRQGLWLRQVLQ8SSHU3DOHR]RLFDQG0HVR]RLF Gal imov (03URNKRURY V S, Fedoseyev'9HWDO+HWHURJHQHRXV PDULQHVWUDWD$FFRUGLQJO\WKH]RQHVZLWKOHVVVHYHUHODWH carbon isotope effects in synthesis of diamond and graphite from gas. WHFWRQLVPLQWKHZHVWHUQ+XEHL±HDVWHUQ&KRQJTLQJDUHDZLWK Geochemistry International. 1973. 10(2): 306-312 no superimposition or modification of Upper and Lower /$QDO\VLV*DR RQSURVSHFWVLQZHVWHUQ+XEHL±HDVWHUQ&KRQJTLQJ 3DOHR]RLFIOXLGVDQGDQ8SSHU3DOHR]RLF]RQHZLWKIOXLG region. Southern China Oil & Gas. 2004. 17(2): 49-52 (in Chinese) =&KHQ)0*XR.)X<;HWDO1DWXUDOJDVUHVHUYRLULQJFRQ GLWLRQV RI6LQLDQDQG&DPEULDQIURPZHVWHUQ+XEHLWRHDVWHUQ&KRQJTLQJ areas for future hydrocarbon exploration. areas. Journal of Southwest Petroleum University (Science & Technology Edition). 2008. 30(4): 39-42 (in Chinese) Acknowledgements )DR+/L67*RQJ=6HWDO7KHUPDOUHJLPHLQWHUUHVHUYRLU 7KLVZRUNZDVVSRQVRUHGE\1DWLRQDO3URJUDPVIRU compositional heterogeneities, and reservoir-filling history of the Dongfang Gas Field, Yinggehai Basin, South China Sea: Evidence Fundamental Research and Development (973 Program, $$3*%XOOHWLQIRUHSLVRGLFÀXLGLQMHFWLRQVLQRYHUSUHVVXUHGEDVLQV 2012CB214805), and the National Natural Science 2000. 84(5): 607-626 Foundation (40930424). QJ6-4LQJ++XD5+XDQJHW3DO37KHIRUPDWLRQDQGHYROXWLRQRI seawater strontium isotopes from Late Permian to Early Triassic— References %DVHGRQWKHUHVHDUFKRQFDUERQDWLWHLQ=KRQJOLDQJ0RXQWDLQ 0HVKDULO$$$.RNDO6/-HQGHQ3'HWDO$QLQYHVWLJDWLRQ RI &KRQJTLQJ6FLHQFHLQ&KLQD 6HULHV'(DUWK6FLHQFHV 397IHFWVHIRQJHRFKHPLFDO¿QJHUSULQWLQJRIFRQGHQVDWHVIURPJD 12(3): 273-283 (in Chinese) FKDUJLQJIURPWKH/RZHU3DOHR]RLFVKRXOGEHLPSRUWDQWWDUJHW +XQDQDQG-LDQJ[LSURYLQFH(DUWK6FLHQFH)URQWLHUV &DUERQLIHURXVDQG3HUPLDQUHVHUYRLUVRQO\ORFDOPRGL¿FDWLRQ HRULJLQ %RUHKDP&-*ROGLQJ6'DQG*OLNVRQ0)DFWRUVFRQWUROOLQJWK 18 Pet.Sci.(2013)10:1-18 Kar lsen '$1HGNYLWQH T, Larter S RHWDO\GURFDUERQ+FRPSRVLWLRQ RIDXWKLJHQLFLQFOXVLRQV$SSOLFDWLRQWRHOXFLGDWLRQRISHWUROH XP $EVWUDFWV UHVHUYRLU¿OOLQJKLVWRU\*HRFKLPLFDHW&RVPRFKLPLFD$FWD  ++XDQJ6KL6-6KHQ/&HWDO6WUDWLJUDSKLFDOVLJQLILFDQFHRIWKH 57(15): 3641-3659 VWURQWLXPLVRWRSLFFXUYHRIWKHXSSHU3DOHR]RLFRI6LFKXDQDQG 18 13 Kor te C, Jasper T.R]XU+:HWDOį 2DQGį C of Permian  LQ&KLQHVH   *XL]KRX-RXUQDORI6WUDWLJUDSK\ EUDFKLRSRGV$UHFRUGRIVHDZDWHUHYROXWLRQDQGFRQWLQHQWDO ;KL66XQ'04LQ6)HWDO&DUERQLVRWRSLFFKDUDFWHULVWLF VRI glaciation. Palaeogeography, Palaeoclimatology, Palaeoecology. natural gas in the great-medium coal-formed gas fields of China. 2005a. 224(4): 333-351 Experimental Petroleum Geology. 2000. 22(1): 16-21 (in Chinese) 13 18 Kor te C.R]XU+:DQGHL]HU9-į &DQGį O values of Triassic .(YDOXDWLRQRIDVLPSOHPRGHORIYLWULQLWH$HQH\--DQG%XUQKDP6ZH EUDFKLRSRGVDQGFDUERQDWHURFNVDVSUR[LHVIRUFRHYDOVHDZDWHU UHIOHFWDQFHEDVHGRQFKHPLFDONLQHWLFV$$3*%XOOHWLQ and palaeotemperature. Palaeogeography, Palaeoclimatology, 74(10): 1559-1570 Palaeoecology. 2005b. 226(3-4): 287-306Ung erer36WDWHRIWKHDUWRIUHVHDUFKLQNLQHWLFPRGHOLQJRIRLO KHWDOWURQWLXPLVRWRSH6HYRO%UXFNVFKHQ3WH&:.R]XU+RU XWLRQRI formation and expulsion. Organic Geochemistry. 1990. 16(1-3): Late Permian and Triassic seawater. Geochimica et Cosmochimica 1-25 87 86 13 18 $FWD   ]HU-HL$OD9'$]P\.HWDO Sr/ 6Uį &DQGį O evolution of QJ'/LD*=KDQJ6&=KDR0-HWDO7KHK\GURFDUERQIRU PDWLRQ   &KHPLFDO*HRORJ\3KDQHUR]RLFVHDZDWHU period in Kuche Depression. Chinese Science Bulletin. 2002. S1: 55- LPHDQG7WHPSHUDWXUHLQSSOL$SHWUROHXPOHV':IRUPDWLRQDS: FDWLRQ 63 (in Chinese) RI/RSDWLQ¶VPHWKRGVWRSHWUROHXPH[SORUDWLRQ$$3*%XOOHWLQ *;DR/LX7-3DQ<:/HWDO*HQHWLFW\SHVRIWKHQDWXUDO JDVLQ 1980. 64(6): 916-926 the northeast and the east of Sichuan Basin. Petroleum Geology and Wel te '+ and Yalcin 01%DVLQPRGHOOLQJ²$QHZFRPSUHKHQVLYH Experiment. 2002. 24(6): 512-516 (in Chinese) method in petroleum geology. Organic Geochemistry. 1988. 13(1-3): +)/LX;LD<LQ3<-<HWDO&RXSOLQJPHFKDQLVPRIVWULNH VOLS 141-151 orogen and basin. Earth Science Frontiers. 1999. 6(3): 121-132 (in <7KH<PHWKRGX:DQGSUDFWLFHRIVHTXHQFHVWUDWLJUDSKLFDQDO\VLV Chinese) in the nonmarine basins. Petroleum Exploration and Development. ;0XR*/LX=)DQG)X<;([SORUDWLRQSRWHQWLDORIQDWXUDO JDVRI 1997. 24(5): 7-10 (in Chinese) ORZHUDVVHPEODJHLQVRXWKHDVWPDUJLQRIPLGGOHDQJW]H<%ORFN =</L;LH-DQG/X;:$QDSSURDFKWRWKHFKDQJLQJRULJLQDQG *HRORJ\DQG0LQHUDO5HVRXUFHVRI6RXWK&KLQD L Q FODVVL¿FDWLRQRIHWKDQHFDUERQLVRWRSHLQPDULQHDULPJDVDVLQ%RI7 Chinese) Petroleum Exploration and Development. 1999. 26(6): 27-29 (in +=DQG*XR'-URJUHVV3DQGWUHQGVRIUHVHDUFKRQÀXLGLQ/X FOXVLRQV Chinese) Geological Review. 2000. 46(4): 385-391 (in Chinese) *6&DR=KX--)0HWDO'LYLVLRQRI;XÀXLGFRPSDUWPHQWV DQGWKH /*HRWHFWRQLFV0DDQG0DULQH2LODQG*DV*HRORJ\LQ6RXWK&KL QD formation and evolution of oil and gas accumulation in the typical Beijing: Geology Press. 2004. 461-462 (in Chinese) VWUXFWXUHVRIZHVWHUQ+XEHL±HDVWHUQ&KRQJTLQJDUHD&KLQD-RXUQDO NHQ]LHDF0$6DQG0FNHQ]LH',VRPHUL]DWLRQDQGDURPDWL]DWLRQ of Chengdu University of Technology (Science & Technology of hydrocarbons in sedimentary basins formed by extension. Edition). 2009. 36(6): 621-630 (in Chinese) *HRORJLFDO0DJD]LQH   <&;X6KHQ3DR70;HWDO*HRFKHPLVWU\RQPDQWOHGHULYHG NHQ]LH$6D0F/HZLV&$ and 0D[ZHOO-50ROHFXODUSDUDPHWHUV YRODWLOHVLQQDWXUDOJDVHVIURPHDVWHUQ&KLQDRLOJDVSURYLQFHV , $ of maturation in the Toarcian shales, Paris Basin, France—IV novel helium resource—commercial accumulation of mantle-derived Laboratory thermal alteration studies. Geochimica et Cosmochimica helium in the sedimentary crust. Science in China (Ser. D). 1997. $FWD   42(2): 315-321 NHQ]LH$60D[ZHOO0DF J R, Coleman0/HWDO%LRORJLFDOPDUNHU =<DQG/LQ;X*3KDQHUR]RLFWHFWRQLFHYROXWLRQDQGLWVQFHLQÀXHRQ and isotope studies of North Sea crude oils and sediments. WKHSHWUROHXPV\VWHPLQWKHDQJW]HPLGGOHUHJLRQ<*HRWHFWRQLFD HW Proceedings of the World Petroleum Congress. 1984. 11(2): 45-56 0HWDOORJHQLD   LQ&KLQHVH WHUVRQ:'3HWUROHXP¿OOLQJKLVWRU\RI0DV$ODVNDFHQWUDO1RUWK6ORSH J=+DQ<=KDQJ&/=KX/+HWDO7KHW\SHDQGVWDJHRIEDVLQ H[DV7¿HOGV'DOODV8QLYHUVLW\RI PRXQWDLQWUDQVIRUPDWLRQLQFRQWLQHQWDORURJHQ\²7DNLQJ4LQOLQJ UWKXU-F$005HFHQWWUHQGVLQVWURQWLXPLVRWRSHVWUDWLJUDSK\HUUD7 as an example. Earth Science Frontiers. 1999. 6(4): 273-281 (in Nova. 1994. 6: 331-358 Chinese) /LJ-;44HW=KRX<DO+7KHTXDQWLWDWLYHLRQLGHQWL¿FDWPRGHO3DQ 1HZ0HWKRGWR,GHQWLI\WKH1DWXUDO$57+DR--DQG-LDQJ<QJ6=KD of the evolution degree of mixing natural gas source material and the \SH8VLQJ&DUERQ,VRWRSHRIWKH0HWKDQHDQG7J(WKDQH*DV%HLMLQ $ Geology Press. 1988 (in Chinese) Chinese) QJ<*=KD=KDQJ).DQG=KHQ&<7KH0HWKRGVWR,GHQWLI\WKH QKDUGW(5HL*%OHQNLQVRS-DQG3DWWHUVRQ57$VVHVVPHQWRID 6U Carbon Isotope. Beijing: Geology Press. 1987 (in Chinese) 87 86 isotope vital effect ( Sr/ 6U LQPDULQHWD[DIURP/HH6WRFNLQJ R0-=KD=HQJ)*4LQ6)HWDOZR7S\URO\WLFJDVHVIRXQG DQG ,VODQG%DKDPDV*HR0DULQH/HWWHUV   proved in Talimu Basin. Natural Gas Industry. 2001. 21(1): 35-38 (in RH'DQG0XHKOHQEDFKVRZ K,VRWRSLF¿QJHUSULQWVRIVKDOORZJDVHVLQ Chinese) the Western Canadian sedimentary basin: Tools for remediation of Zhu G Y, Zhang S C, Liang Y B, et al. The characteristics of natural gas OHDNLQJKHDY\RLOZHOOVJDQLF2U*HRFKHPLVWU\    in Sichuan Basin and its sources. Earth Science Frontiers. 2006. 871 13(2): 234-248 (in Chinese) NKHLP5F-DQG(QJODQG:$2UJDQLFJHRFKHPLVWU\RISHWUROHXP UHVHUYRLUV6RFLHW\RI([SORUDWLRQ*HRSK\VLFLVWVWK$QQXDO (Edited by Hao Jie) LQ DSSOLFDWLRQRIWKLVPRGHOFWD3HWUROHL6LQLFD (* ,QWHUQDWLRQDO&RQIHUHQFH([SDQGHG$EVWUDFWVDQG%LRJUDSKLHV6 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Petroleum Science Springer Journals

Fluid migration paths in the marine strata of typical structures in the western Hubei-eastern Chongqing area, China

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Publisher
Springer Journals
Copyright
Copyright © 2013 by China University of Petroleum (Beijing) and Springer-Verlag Berlin Heidelberg
Subject
Earth Sciences; Mineral Resources; Industrial Chemistry/Chemical Engineering; Industrial and Production Engineering; Energy Economics
ISSN
1672-5107
eISSN
1995-8226
DOI
10.1007/s12182-013-0244-y
Publisher site
See Article on Publisher Site

Abstract

Pet.Sci.(2013)10:1-18 1 DOI 10.1007/s12182-013-0244-y Fluid migration paths in the marine strata of typical structures in the western Hubei– eastern Chongqing area, China 1 1 2 1 1 Xu Guosheng , Liang Jiaju , Gong Deyu , Wang Guozhi , Yuan Haifeng , 1 3 Cao Junxing and Zhang Chengfu State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (Chengdu University of Technology), Sichuan 610059, China Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China 3X\DQJ+HQDQ&KLQD6,123(&=KRQJ\XDQ2LO¿HOG&RPSDQ\ JHUOLQ+HLGHOEHUHUODJ%9‹&KLQD8QLYHUVLW\RI3HWUROHXP %HLMLQJ DQG6SULQJHU Abstract: 7KHZHVWHUQ+XEHL±HDVWHUQ&KRQJTLQJDUHDLVDQLPSRUWDQWSURVSHFWLYH]RQHIRURLODQG JDVH[SORUDWLRQLQWKHFHQWUDODQJW]H<DUHD7KUHHUHSUHVHQWDWLYHVWUXFWXUHVWKH;LQFKDQJVWUXFWXUH /RQJMXEDJDVEHDULQJVWUXFWXUHDQGWKH-LDQQDQJDV¿HOGZHUHHOHFWHGVWRDQDO\]HELRPDUNHUSDUDPHWHUV in marine strata and to examine various types of natural gas and hydrocarbon sources. Fluid inclusions; carbon, oxygen, and strontium isotopic characteristics; organic geochemical analysis and simulation RIK\GURFDUERQJHQHUDWLRQDQGH[SXOVLRQKLVWRU\RIVRXUFHURFNVZHUHXVHGIRUWUDFLQJÀXLGPLJUDWLRQ paths in marine strata of the study area. The Carboniferous-Triassic reservoirs in three typical structures DOOH[SHULHQFHGDWOHDVWWZRVWDJHVRIÀXLGDFFXPXODWLRQ$OOP DULQHVWUDWDDERYHWKHHDUO\HUPLDQ3HUHZ VKRZQWRKDYHÀXLGVRULJLQDWLQJLQWKHHUPLDQ3IHUHGURFNVIURPZKLFKWKHODWHGLIVWDJH7KHÀXLGVXLGVÀ DFFXPXODWHGLQWKHODWH3HUPLDQUHVHUYRLUVRIWKH;LQFKDQJFWXUHVWUXHUHZ&DPEULDQXLGVÀZKLOHWKRVH LQWKHODWH&DUERQLIHURXVUHVHUYRLUVZHUHVRXUFHGIURPDFRPELQ DWLRQRI6LOXULDQDQG&DPEULDQÀXLGV $ORQJGLVWDQFHDQGJHVFDOHODUFURVVIRUPDWLRQDOÀRZRIÀXLGVGHVWUR\HGWKHSUHVHUYDWLRQFRQGLWLRQVRI HDUOLHUVKRUWGLVWDQFHLRQDODFFXPXODWHG$FURVVIRUPDWDFFXPXODWLRQK\GURFDUERQVRI6LOXULDQXLGVÀDVZ shown in the late Permian reservoirs of the Longjuba structure with favorable hydrocarbon preservation conditions. The fluid accumulation in the Carboniferous reservoirs of the Jiannan structure mainly RULJLQDWHGIURPQHLJKERULQJ6LOXULDQVWUDWDZLWKDVPDOODPRXQWIURPWKH&DPEULDQVWUDWD$VDUHVXOW the Jiannan structure was determined to have the best preservation conditions of the three. Comparative DQDO\VLVRIÀXLGPLJUDWLRQSDWKVLQWKHWKUHHVWUXFWXUHVUHYHDOHGWKDWWKH]RQHZLWKDZHDNHUODWHWHFWRQLVP DQGQRVXSHULPSRVLWLRQDQGPRGL¿FDWLRQRIWKH8SSHUDQG/RZHUDOHR]RLF3ÀXLGVRUWKH8SSHU3DOHR]RLF ]RQHLWKZWKHXLGÀJLQJFKDUIURPWKH/RZHUDOHR]RLF3LQWKHWHUQHVZ+XEHL±HDVWHUQ&KRQJTLQJDUHDDUH important target areas for future exploration. Key words:HVWHUQ+XEHL±HDVWHUQ:&KRQJTLQJDUHDPDULQHVWUDWDDOJHRFKHPLFWUDFHUÀXLGPLJUDWLRQ path &DOHGRQLDQ'RQJZX,QGR6LQLDQDQVKDQ<DQG+LPDOD\DQ 1 Introduction movements. The multi-phase tectonic activities have to a The marine carbonate areas of the superimposed basins certain degree reformed and damaged the early excellent in the south of China have become important targets for preservation condition. It is safe to say that the preservation H[SORUDWLRQIRURLODQGJDVLQ&KLQD+RZHYHUDVWKH\KDYH FRQGLWLRQKDVEHFRPHDNH\IDFWRUUHVWULFWLQJWKHH[SORUDWLRQ a deep burial depth and have experienced multiple cycles for oil and gas in these marine carbonate areas in the south of structural movements and intense post-reconstructions, of China. Scholars have studied the preservation condition the geological conditions of these areas are especially IURPVXFKSHUVSHFWLYHVDVFDSURFNSK\VLFDOSURSHUWLHV complicated. The most influential movements are the hydrodynamic environment, sealing ability of faults and tectonic movements. It is not possible for us to evaluate the static preservation condition of the complicated areas that HPDLOOLDQJMLDMX#TTFRP &RUUHVSRQGLQJDXWKRU have gone through multi-phase tectonic activities from only Received June 8, 2011 WKHSHUVSHFWLYHRIJHQHUDOSDUDPHWHUVRIFDSURFNSK\VLFDO 2 Pet.Sci.(2013)10:1-18 properties. We have found a new way to evaluate the LVDSDUWRIWKHFHQWUDODQJW]H< DUHD ;XDQG/LQ preservation condition of the marine oil and gas from the Liu et al, 2007), is geographically located in the western G\QDPLFHYDOXDWLRQ$SHUVSHFWLYHRISDOHRÀXLGJHRFKHPLVWU\ +XEHL3URYLQFHDQGHDVWHUQ&KRQJTLQJ&LW\7KLVDUHDLV can be conducted for the preservation condition of the areas that have experienced multi-phase tectonic activities. The front in the eastern margin of the Sichuan Basin, covering following three typical structures that differ significantly in DQ[LDQ:6KL]KXDQG/LFKXDQV\QFOLQRULXPV)DQJGRXVKDQ H[SORUDWLRQIHFWLYHQHVVHI;LQFKDQJ/RQJMXEDDQG-LDQQDQ and Qiyueshan anticlinoriums, and other tectonic units ZHUHFKRVHQDVFDVHVWRDQDO\]HRLODQGJDVVRXUFHVLQWKH )LJ 7KHVWXG\UHJLRQKDVDQDUHDRINP , and PDULQHVWUDWDRIZHVWHUQ+XEHL±HDVWHUQ&KRQJTLQJDUHDDQG VHFRQGDU\VWUXFWXUHVXSL]HDUHGHYHORSHGZKLFKLQFOXGH<WKH WRWUDFHÀXLGPLJUDWLRQSDWKV7KLVLVH[SHFWHGWRVKHGOLJKW /LDQJTLDR&L]KX\D*DRIHQJFKDQJ0DFDRED'DFKLJDQMLQJ RQWKHIRUPDWLRQHYROXWLRQGHVWUXFWLRQDQGPRGL¿FDWLRQRI +XDQJMLQWDLDQMLQJ<&KD\XDQSLQJ;LQFKDQJ-LDQQDQDQG IHUHQWVWUXFWXUHVDQGWRSURYLGHDVFLHQWL¿FEDVLVIRUIXUWKGLI HU /RQJMXEDVWUXFWXUHV1XPHURXVJDV¿HOGVLQFOXGLQJ-LDQQDQ exploration for oil and gas in this area. Gaofengchang, and Dachiganjing, and gas-bearing structures DQMLQJDQG/RQJMXED<DQJGX[L&L]KX\D<XSL]H<LQFOXGLQJ 2 Geological setting have already been discovered. 7KHZHVWHUQ+XEHL±HDVWHUQ&KRQJTLQJDUHDZKLFK 0DULQHEDVLQVZHUHGHYHORSHGLQWKHFHQWUDODQJW]H< Fengjie The Yangtze River Yunyang 0 10 20 km Wanxian Xinchang2 Well Xinchang Tuxiangba Gaofengchang Cizhuya Longjuba Synclinorium Long 8 well of Wanxian Liangqiao Ma’ancao Jian 44 well Yupize Dachiganjing Jiannan Sujiachang Jian well 38 Lichuan Zhongxian Synclinorium Synclinorium Yangduxi of Shizhu of Lichuan Yanjing Chayuanping Shizhu Huangjintai Boundary line Reverse fault The Yangtze River Fengdu Anticlinorium Anticlinorium of Qiyueshan of Fangdoushan Shuangliuba Anticlinorium Typical structure Secondary structure Fig. 1KRQJTLQJDUHDDQGORFDWLRQGLDJUDPRIW\SLFDOVWUXFWXUHV&ODVVL¿FDWLRQRIWHFWRQLFXQLWVLQWKHZHVWHUQ+XEHL±HDVWHUQ& DUHDIURPWKHHDUO\6LQLDQSHULRGRIWKH/DWH3URWHUR]RLF X)HWDO/LXHWDOX;DQG/LQ&KHQ WRWKHODWH(DUO\ULDVVLF7 RIWKH0HVR]RLFHUD7KHVWXG\ et al, 2007). The area west of the Qiyueshan anticlinorium to area experienced Caledonian and Indo-Sinian closure and WKH)DQJGRXVKDQDQWLFOLQRULXPDQGWKH6KL]KXV\QFOLQRULXP orogeny in the South China and Paleo-Qinling oceans, LVFKDUDFWHUL]HGE\IDYRUDEOHSUHVHUYDWLRQFRQGLWLRQV where two stages of mass marine regression occurred, and with a high degree of trap identification. In addition, the marine strata were developed mainly as deep-water basin area is situated in a beneficial paleo-tectonic position for DQGVKDOORZSODWIRUPIDFLHV )LJ 0XOWLSOHVHWVRIVRXUFH K\GURFDUERQPLJUDWLRQDQGDFFXPXODWLRQZKLFKPDNHVLWD reservoir-seal assemblages were developed vertically. Two IDYRUDEOHH[SORUDWLRQ]RQH *XRHWDO 7KH4L\XHVKDQ sets of large source-reservoir-seal assemblages (i.e., upper anticlinorium and its eastern part as well as the Lichuan DQGORZHUDVVHPEODJHV ZHUHGLYLGHGE\H[WUHPHO\WKLFN V\QFOLQRULXPDUHFRPSDUDWLYHO\SURVSHFWLYH]RQHV 'DLHWDO Silurian shale as the boundary, constituting the two major 2001). In the Longjuba-Jiannan structure echeloned in the exploration regions in this study area (Wu, 1997; Yang et al, FHQWUDO6KL]KXV\QFOLQRULXPDK\GURFDUERQDFFXPXODWLRQ JHRWHFWRQLFDOO\FODVVL¿HGDVDGHSUHVVLRQEHOWRIWKH'DEDVKDQ Variscan Caledonian Jinning Indo-Sinian tectonic cycle Variscan tectonic cycle tectonic cycle tectonic cycle tectonic cycle Jialingjiang Hanjiadian Longmaxi Lower Upper Lower Middle Lower Triassic Permian Silurian Ordovician Cambrian Sinian Mesozoic Palaeozoic Feixianguan Pet.Sci.(2013)10:1-18 3 FRPSRVLWLRQVRIK\GURFDUERQVIURPWKHVDPHVRXUFHURFNV Stratigraphy Code Lithology Age, Ma Tectonic cycle while large differences are evident in those from different ErathemSystem Series Formation VRXUFHURFNV6XFKVLPLODULWLHVVHUYHDVDEDVLVIRURLO T j 1 5 T j source correlation. Currently, gas chromatography and mass 1 4 T j VSHFWURPHWU\ *&06 SURYLGHZLGHO\XVHGELRPDUNHUVIRU 1 3 RLOVRXUFHFRUUHODWLRQ $O0HVKDULHWDO +\GURFDUERQV T j are altered during biodegradation processes (Rowe and T j 0XHKOHQEDFKV0DVWHUVRQ DQGJURXQGZDWHU T f scouring, resulting in incorrect oil-source correlation. +RZHYHUWKHLQIOXHQFHVRIH[WHUQDOVHFRQGDU\IDFWRUVDUH T f effectively reduced in the correlation processes through the T f XVHRIVXFKWHFKQLTXHVDVELRPDUNHUVDQGFRPSUHKHQVLYH FRPSDULVRQRIYDULRXVSDUDPHWHUV$OWKRXJKLVRWRSHVDUH T f WKHPRVWLPSRUWDQWLQGLFDWRUVLQRLOJDVFRPSDULVRQV +DR 251.0 Dalong P d et al, 2000), fractionation will occur in isotopes during Changxing P ch hydrocarbon migration (Galimov et al, 1973; Karlsen et al, Longtan P l %RUHKDPHWDO ZKLFKFUHDWHVGLI¿FXOWLHVLQJDV source correlation. Maokou P m $QPRGHOWRHVWLPDWHRUJDQLFPDWXULW\RQWKHEDVLV of vitrinite reflectance was first completed by the time- Qixia P q temperature index (TTI) method (Waples, 1980) and this was Liangshan P l 299.0 Carboni- WKHQUHSODFHGE\DPRGHOWKDWFDOFXODWHVYLWULQLWHUHÀHFWLYLW\ Middle Huanglong C hl ferous (R PRUHHI¿FLHQWO\NQRZQDVWKH(DV\ R dynamic model o o 359.2 6ZHHQH\DQG%XUQKDP $WKHUPDOUHODWHGELRPDUNHU S h UDWLRZDVSURSRVHGE\0DFNHQ]LHHWDO 0DFNHQ]LHHWDO 0DFNHQ]LHDQG0FNHQ]LH IRUEDVLQ 416.0 Xiaoheba S x 1 modeling, so that the paleotemperature could be calculated more accurately (Welte and Yalcin, 1988; Ungerer, 1990). WKH(DV\+RZHYHU R FKHPLFDONLQHWLFPRGHOODWHUSURSRVHG by Sweeney and Burnham (1990) is the most commonly S l used model in current studies on paleotemperature. On the EDVLVRIYLWULQLWHUHÀHFWDQFHPHDVXUHGIURPGULOOLQJFRUHVD EHWWHU(DV\ R dynamic simulation method with a broader 433.7 application scope was used in this study to reconstruct the WKHUPDOKLVWRU\RIVRXUFHURFNVDQGWKHHYROXWLRQDU\KLVWRU\ of hydrocarbon generation. The previous R YDOXHZDV 488.3 $VHFRQGDU\K\GURFDUERQPLJUDWLRQDQGUHVHUYRLUJHFKDU principle was described by England et al (1987; 1995), 5FNKHLPDQG(QJODQG  DQG(QJODQGDQG0DFNHQ]LH 542.0 (1989), in which the component, phases, temperature, and other information on inclusions were used to calibrate the history of hydrocarbon charge and time of hydrocarbon accumulation. In addition, fluid inclusion stratigraphy was Fig. 2 Synthetic column map of Z-T in the western applied to fluid source and migration pathway research +XEHL±HDVWHUQ&KRQJTLQJDUHDVKRZLQJWHFWRQLFF\FOHV by some scholars (Barclay et al, 2000). The inclusion KRPRJHQL]DWLRQWHPSHUDWXUHGLVFXVVHGKHUHLQJHQHUDOO\ belt was formed with Jiannan as the center. The Jiannan gas refers to that of hydrocarbon-bearing saline inclusion, rather field was discovered in the central syncline, proving that WKDQWKDWRIK\GURFDUERQLQFOXVLRQV7KHKRPRJHQL]DWLRQ the Longjuba-Jiannan structure had favorable preservation temperature of hydrocarbon inclusions is often lower than that conditions for gas reservoirs in addition to a tectonic setting of saline inclusions of the same period (Lu and Guo, 2000). for hydrocarbon accumulation (Chen, 2003; Gao, 2004). Inclusions are able to reflect the essential characteristics of ore-forming fluids and provide a series of original data on 3 Sample analysis such mineral formation parameters as temperature, elemental $VLVZLGHO\DFFHSWHGNHURJHQLQVRXUFHURFNVLV FRPSRVLWLRQDQGVDOLQLW\$IOXLGJHRFKHPLFDOWUDFHUZDV FUDFNHGLQWRSHWUROHXPDQGQDWXUDOJDVXQGHUFHUWDLQ combined with the inclusion test and analysis methods in this FRQGLWLRQVDQGK\GURFDUERQLQVRXUFHURFNVKDVDJHQHWLF JHGXUDWLRQVSDSHUWRVWXG\ÀXLGPLJUDWLRQSDWKDQGFKDU relationship with bitumen in addition to oil and gas in the URFNUHVHUYRLUV7KXVVLPLODULWLHVH[LVWLQWKHFKHPLFDO of natural gas, inclusions, carbon, oxygen, and strontium in HWKHQGHWHUPLQHGELRPDUNHUVDQGVWDEOHFDUERQLVRWRSHV 4 Pet.Sci.(2013)10:1-18 YHLQVDQGVXUURXQGLQJURFNVLQDGGLWLRQWRRWKHUJHRFKHPLFDO well is of high maturity, only methane and small amounts of analysis data and their sources. ethane and propane were detected; thus, light hydrocarbon )LYHQHZVDPSOHVRISRWHQWLDOVRXUFHURFNVDQGILYH DQDO\VLVFRXOGQRWEHSHUIRUPHG$VDUHVXOWWKHJDVLVRWRSLF samples of residual organic material in reservoirs were PDVVVSHFWURPHWHU70$ZDVXVHGWRGHWHUPLQHVWDEOH REWDLQHGIURPHOOZ;LQFKDQJLQWKHHVWHUQZ+XEHL±HDVWHUQ carbon isotopes of natural gas. &KRQJTLQJDUHD$JDVFKURPDWRJUDSK +3+HZOHWW The collected samples of calcite and gypsum veins that 3DFNDUG DQGJDVFKURPDWRJUDSKPDVVVSHFWURPHWHU *& ¿OOHGIUDFWXUHVLQUHVHUYRLUURFNVHUHZWHVWHGE\WKH*XL\DQJ 068063 ZHUHXVHGWRPHDVXUHWRWDOK\GURFDUERQJDV ,QVWLWXWHRI*HRFKHPLVWU\&KLQHVH$FDGHP\RI6FLHQFHV FKURPDWRJDSK\ELRPDUNHUVDQGYLWULQLWHUHIOHFWDQFHZDV It was determined that hydrocarbon gases were contained measured with a microphotometer (Tables 1-3). Due to the LQIOXLGLQFOXVLRQV+RZHYHUIHZK\GURFDUERQEHDULQJ high maturity of residual organic matter in the study area, the organic extract was too limited to permit the analysis of group ,QFOXVLRQ 0&,Œ DQDO\VLVFRXOGQRWEHSHUIRUPHG,QVWHDG components and their isotopes. ODVHU5DPDQTXDQWLWDWLYHDQDO\VLVZDVXVHGRQLQFOXVLRQ The analysis data of 17 natural gas samples in 16 wells components. In addition, carbon, oxygen, and strontium were used in this study (Table 4 and Table 5), including one isotopic values were obtained with the UK VG354 isotope Permian natural gas sample from the well Long 8 in the PDVVVSHFWURPHWHU 7,06 E\WKH,VRWRSH0DVV/DERUDWRU\RI Longjuba structure. Because the Permian natural gas in this DEOH 1DQMLQJ8QLYHUVLW\ 7$QDO\VLV&HQWHU0RGHUQ Table 1WDVDPSOHVIURPZHOO;LQFKDQJ6DWXUDWHGK\GURFDUERQFKURPDWRJUDSK\SDUDPHWHUVRIPDULQHVWUD C +C 21 22 Sample No. Depth, m +RUL]RQ Lithologic description ™& ™& Pr/nC Ph/nC Pr/Ph 21 22 17 18 /C +C 28 29 ;& 2824.42 T f 'DUNJUD\OLPHVWRQHSRWHQWLDOVRXUFHURFNV 1.33 0.95 0.64 0.86 0.53 ;& 2828.22 T f %ODFNOLPHVWRQHSRWHQWLDOVRXUFHURFNV / 3.16 1.05 1.42 0.55 'DUNJUD\OLPHVWRQHRUJDQLFPDWWHUILOOHGDORQJVXWXUH ;& 2848.22 T f 4.90 2.49 0.29 0.75 0.48 ]RQHV *UD\GDUNJUD\OLPHVWRQHRUJDQLFPDWWHUILOOHGDORQJ ;& 2853.83 T f 3.21 2.01 0.63 1.06 0.50 VXWXUH]RQHV /LJKWJUD\OLPHVWRQHEODFNRUJDQLFPDWWHUILOOHGDORQJ ;& 2862.90 T f 12.75 1.99 0.75 0.96 0.60 VXWXUH]RQHV ;&V 3338.35 P c %ODFNOLPHVWRQHSRWHQWLDOVRXUFHURFNV 1.82 1.34 0.43 0.74 0.51 ;& 3376.04 P c JDQLFPDWWHU'DUNJUD\OLPHVWRQH¿OOHGZLWKPDVVLYHRU 4.00 1.37 1.50 1.82 0.23 ;&V 4607.54 P T %ODFNFRDOURFNSRWHQWLDOVRXUFHURFNV / 2.22 0.83 1.10 0.59 ;&V 4608.54 P T %ODFNFRDOURFNSRWHQWLDOVRXUFHURFNV 10.00 1.56 1.11 1.25 0.40 *UD\GRORPLWHELWXPHQDORQJVXWXUH]RQHVDQG¿OOHGLQ ;& 4623.04 C c 0.53 0.67 0.70 1.03 0.61 factures Table 2HUSDQHDQGVWHUDQHELRPDUNHUSDUDPHWHUVRIPDULQHVWUDWDVDPS7 OHVIURPWKHZHOO;LQFKDQJ C Ts/ C 22S/ Gammacerane / Tricyclic-terpane/ C ĮĮĮ 6  C +C -pregnane Diasterane/ 29 32 29 21 22 Sample No. +RUL]RQ Ts/Tm (C Ts+C ) (22S+22R) C hopane C hopane /(20S+20R) /C ĮĮĮ 5 regular sterane 29 29 30 30 29 ;& T f 0.69 0.21 0.59 0.26 1.06 0.38 0.44 0.14 ;& T f 0.95 0.29 0.62 0.17 3.67 0.30 2.61 0.22 ;& T f 0.56 0.25 0.59 0.26 0.49 0.41 0.23 0.07 ;& T f 0.73 0.14 0.59 0.26 2.02 0.36 1.15 0.14 ;& T f 1.61 0.18 0.62 0.34 0.58 0.35 1.14 0.26 ;&V P c 0.50 0.09 0.59 0.29 0.26 0.46 0.09 0.06 ;& P c 0.93 0.28 0.57 0.19 1.71 0.34 1.03 0.20 ;&V P T 1.07 0.21 0.60 0.23 2.50 0.31 3.15 0.23 ;&V P T 0.90 0.18 0.60 0.19 3.33 0.29 2.62 0.28 ;& C c 0.98 0.18 0.60 0.29 1.26 0.37 0.58 0.41 LQFOXVLRQVZHUHGHWHFWHG7KXV0ROHFXODU&RPSRVLWLRQRI2LO Pet.Sci.(2013)10:1-18 5 Table 3URPDWLFFKDUDFWHULVWLFSDUDPHWHUVRIVDPSOHVIURPZHOO;LQFKD$ QJ 5HODWLYHFRQWHQW 5HODWLYHFRQWHQW Sample 'LEHQ]RWKLRSKHQH +RUL]RQ SF/P No. Phenanthrene Chrysene GLEHQ]RIXUDQDQG 'LEHQ]RWKLRSKHQH Fluorene 'LEHQ]RIXUDQ ÀXRUHQH ;& T f 94.34 / 5.66 0.978 0.244 / 0.047 78.50 / 21.50 ;& T f 87.52 / 12.48 1.050 0.624 0.279 0.033 23.00 67.38 9.62 ;& T f 93.90 / 6.10 3.222 0.993 0.547 0.003 5.38 80.52 14.10 ;& T f 99.45 / 0.55 2.388 0.332 0.021 / / 100.00 / ;& T f 84.16 / 15.84 1.162 2.225 / 0.032 16.94 67.56 15.50 ;&V P c 93.46 / 6.54 2.851 0.751 0.368 0.006 8.23 84.58 7.19 ;& P c 89.86 / 10.14 1.842 4.408 1.345 0.014 12.80 75.29 11.91 ;&V P T 77.81 / 22.19 1.397 1.845 0.603 0.029 10.15 67.13 22.72 ;&V P T 80.63 / 19.37 1.310 2.250 0.544 0.030 12.57 65.53 21.91 ;& C c 89.57 / 10.43 0.894 0.716 0.110 0.031 26.93 47.67 25.40 Table 4 Conventional components of natural gas in C -T j formations in the Jiannan-Longjuba structure and characteristics of carbon isotopes in well Long 8, 2 1 VWUXFWXUHLVLQDFFRUGDQFHZLWKWKDWUHSRUWHGE\0D  7KHGDWDIRUWKH-LDQQDQ-LDQQDQJDV¿HOGDQGDGMDFHQWDUHDV Well No. Formation Depth, m C , C  C  N  CO  + C /C -C 1 2 3 2 2 2 1 1 5 Long 8 P m 98.35 0.14 / 0.28 1.2 / 99.85 Jian 32 T j 2494.05-2531 94.70 0.17 — 1.67 3.07 0.40 99.82 Jian 3 T f 2709-2762 96.04 0.20 — 0.31 2.93 0.52 99.79 Jian 10 T f 2927-2941 9652 0.12 — 1.15 1.94 0.27 99.88 Jian 45 T f 3061-3089 94.93 0.21 — 1.87 2.81 0.18 99.78 Jian 15 T f 3110-3161.1 96.55 0.12 — 1.51 1.72 0.105 99.88 Jian 41 T f 3343.6-3402 92.00 0.14 — 0.84 4.51 2.48 99.85 Jian 47 T f 3614.4-3642.6 95.93 0.09 — 1.72 1.98 0.28 99.91 Jian 16 P c 3109.9-3229.6 86.73 0.17 — 1.19 8.56 3.36 99.80 Jian 40 P c 3329.6-3348.4 87.04 0.07 — 0.77 8.87 3.24 99.92 Jian 43 P c 3456-3483 92.05 0.19 — 0.26 5.70 1.80 99.72 Jian 44 P c 3738.11-3760.18 88.37 0.06 — 1.30 7.39 2.88 99.93 Jian 13 C 3728.59-3748.15 94.31 1.22 0.24 3.39 0.68 0.162 98.72 Jian 37 C 3836.4-3860.0 94.71 1.24 0.15 3.24 0.66 0 98.70 Jian 28 C 3943-3950 94.57 1.23 0.13 3.51 0.56 0 98.72 Table 5 QJMXEDVWUXFWXUHLVLQ7KHGDWDIRUWKH/R$QDO\VLVUHVXOWVRIWKHFDUERQLVRWRSHVRIWKHQDWXUDOJDVLQWKH/RQJMXEDVWUXFWXUHDQG-LDQQDQJDV¿HOG K,QVWLWXWHRI-LDQJKDQ2LO¿HOGDFFRUGDQFHZLWKWKDWRIWKH([SORUDWLRQDQG'HYHORSPHQW5HVHDUF 13 13 13 13 Structure location Well No. Formation Depth, m į C , ‰ į C , ‰ į C į C , ‰ 1 2 2 1 Longjuba Long 8 P m -29.9 -32.7 -2.8 Jian 31 T j 2777.5-2856 -32.2 -37.8 -5.6 The northern high point Jian 31 T j 2777.5-2856 -32.4 -36.4 -4.0 Jian 35 T f 3066.4-3114 -32.1 -38.4 -6.3 The southern high point Jian 27 Ceping1 T f 3680.78-4506.33 -31.0 -38.0 -7.0 Jian 61 T f -33.1 -41.4 -8.3 Jian 10 T f 2927-2941 -32.1 -37.4 -5.3 The northern high point Jian 10 T f 2927-2941 -31.4 -33.3 -1.9 Jian 51 T f -30.8 -28.5 2.3 Jian 43 P ch 3456-3483 -32.0 -38.9 -6.9 Southern high point Jian 43 P ch 3456-3483 -32.2 -37.2 -5.0 Jian 16 P ch 3109.9-3229.6 -31.7 -33.6 -1.9 Northern high point Jian 44 Yuan1 P ch 3145.94-3600 -33.5 -35.6 -2.1 Jian 34 C 3770-3784 -37.2 -41.4 -4.2 Northern high point Jian 28 C 3941-3950 -35.2 -40.0 -4.8 Jian 28 C 3943-3950 -37.9 -41.4 -3.5 '0)'2)6) )'0) )0) )0)2) 6 Pet.Sci.(2013)10:1-18 Table 6IHUHQWURFNVDQGP,VRWRSLFJHRFKHPLFDODQDO\VLVUHVXOWVRIGLI LQHUDOVLQZHOOV;LQFKDQJ/RQJDQG-LDQ 13 18 87 86 Well Sample No. Lithology Well depth, m +RUL]RQ į C (PDB), ‰ į O (PDB), ‰ Sr/ Sr ;F9 Grayish-white megacryst gypsum 3340.5 íí 0.71 ;F9 Calcite veins 4.708 -5.647 0.7075 ;F& 'DUNJUH\PLFULWH 4.632 -4.43 0.7071 ;LQFKDQJ P ch Grayish-white fine-medium grained calcite ;F9 4.946 -6.98 0.7074 vein patch 3375.64 ;F& Grey micrite 4.742 -4.19 0.707 Grayish-white fine-medium grained calcite Bao 10V 3.747 -6.263 0.7071 veins 2 4314.67 P ch Bao 10C Grey micrite 4.086 -6.081 í Grayish-white fine-medium grained calcite Bao 19V 4.111 -5.908 0.7071 veins Long 8 4557.84 P m Bao 19C 'DUNJUH\PLFULWH 3.873 -5.182 í Bao 22V :KLWH¿QHJUDLQHGFDOFLWHYHLQV 4.108 -5.146 0.7071 4784.48 P m Bao 22C 'DUNJUH\PLFULWH 3.817 -4.727 í J38-6V Grayish-white calcite veins 4.07 -7.113 0.7075 3151.42 J38-6C 'DUNJUH\PLFULWH 4.497 -5.105 í Jian 38 T f Grayish-white fine-medium grained calcite J38-9V 3.748 -6.611 0.7075 veins 3153.2 J38-9C Grey calcarenite 3.956 -6.401 0.7076 DFFRXQWIRURIDOOVDPSOHVWKRVHRIPHGLXPJRRG 4 Organic geochemical tracers in marine VRXUFHURFNZLWKD72&EHWZHHQDQGDFFRXQW strata IRURIDOOVDPSOHVDQGWKRVHRIH[FHOOHQWVRXUFHURFN ZLWKD72&DERYHDFFRXQWIRURIWKHVDPSOHV 7KHZHVWHUQ+XEHL±HDVWHUQ&KRQJTLQJDUHDKDVIRXUVHWV ,QWKH6KL]KX/LFKXDQDUHDWKH R RIWKHVKDOHVRXUFHURFN RI7KH\DUHWKHORZHUVRXUFHURFNVLOXULDQORZHU6&DPEULDQ o LVJHQHUDOO\DERYHLQGLFDWLQJDGU\JDVVWDJH7KH Permian coal-measures, and Permian carbonate. The lower 3HUPLDQFDUERQDWHVRXUFHURFNVKDYHEHHQVHOGRPVWXGLHG &DPEULDQVRXUFHURFNVRIWKH4LRQJ]KXVL)RUPDWLRQLQ DQGDUHFRQVLGHUHGDVPLQRUVRXUFHURFNV WKHHDVW6LFKXDQ%DVLQDUHPDLQO\JUD\LVKEODFNVKDOHZLWK $IWHUDQDO\]LQJWKHFKDUDFWHULVWLFVRIWKHIRXUVHWVRI maximum, minimum and average total organic carbon (TOC) VRXUFHURFNVLQWKHVWXG\DUHDZHZHUHDEOHWRGHILQHWKH YDOXHVRI,QDGGLWLRQDQGUHVSHFWLYHO\ origin of the hydrocarbon in the main production formations VDPSOHV RIWKHWRWDOVDPSOHV KDYHD72& E\VWXG\LQJWKHELRPDUNHUFKDUDFWHULVWLFVRIWKHRUJDQLF YDOXHDERYH7KHK\GURFDUERQJHQHUDWLRQSRWHQWLDO PDWWHU¿OOLQJWKHIUDFWXUHV,QDGGLWLRQZHWUDFHGWKHRULJLQ YDOXHRIWKH&DPEULDQVRXUFHURFNVLQLPPDWXUHDQGORZHU of the fluid by studying the strontium, carbon, and oxygen mature stage is between 0.5 mg/g and 20 mg/g. In the lower LVRWRSHVRIWKHYHLQVRIFDOFLWHGRORPLWHDQGJ\SVXPOOLQJ¿ SDUWKLJKTXDOLW\RXUFHVURFNV&KDYH2YDOXHD7DERYH fractures. We also identified the hydrocarbon accumulation and a hydrocarbon generation potential value between 2 mg/g period and the reservoir forming time through examination of and 35 mg/g. The R RIWKHVRXUFHURFNVLVEHWZHHQDQG inclusions. ZLWKDQDYHUDJHDWUHDFKLQJWKHRYHUPDWXUHVWDJH 7KH6LOXULDQVRXUFHURFNVRIWKH/RQJPD[L)RUPDWLRQLQ 4.1 Organic geochemical tracer in the marine strata WKH6KL]KX;LDQIHQJ/DLIHQJDUHDDUHZHOOGHYHORSHGZLWK of Xinchang structure DQDEXQGDQFHRIRUJDQLFPDWWHU0RVW  RIWKHVDPSOHV KDYH2&D7YDOXHDERYHWKH2&DYHUDJH7YDOXHRIWKH &RULQJZDVSHUIRUPHGRQO\LQZHOO;LQFKDQJRIWKH VRXUFHURFNVLV7KHVRXUFHURFNVKDYHDK\GURFDUERQ ;LQFKDQJVWUXFWXUHVRGULOOFRUHIURPWKLVZHOOZDVWKHRQO\ generation potential value between 2 mg/g and 35 mg/g, intact samples available. Tables 1 and 2 demonstrate the which is higher in the northern part than in the southern part. distribution of the residual organic matter from the source The R LQ6LOXULDQURFNVLQWKHVWXG\DUHDLVEHWZHHQ URFNVDQGUHVHUYRLUV DQG &KURPDWRJUDSK\IURPWKHWKUHHVDPSOHV ;&V;& 7KH3HUPLDQVRXUFHURFNVLQFOXGHWKHFRDOPHDVXUHVDQG V;&V RI3HUPLDQVRXUFHURFNVVKRZHGDXQLPRGDO FDUERQDWHVVKDOHVDPSOHVLQWKHZHVWHUQ+XEHL±HDVWHUQ distribution of saturated hydrocarbons from high to low, of &KRQJTLQJDUHDKDYHDQDYHUDJH2&7YDOXHRI7KH which the ratio between low nDONDQHVDQGKLJK nDONDQHV VDPSOHVRISRRUVRXUFHURFNZLWKD2&7EHWZHHQDQG was 1.34, 2.22, and 1.56, respectively (Fig. 3, Table 1). The Pet.Sci.(2013)10:1-18 7 ratio between isoprenoid hydrocarbon and the corresponding showed two different types of characteristics (Fig. 4, Table nDONDQHZDVHLWKHUGRPLQDWHGE\ nDONDQHRULVRSUHQRLG  ,Q;&IRUV7PH[DPSOH7ZDV& Ts/(C Ts + 29 29 K\GURFDUERQ,Q;&VWKHVDPSOHRIFRDOPHDVXUH C ) was 0.25; gammacerane/C hopane was 0.26; tricyclic 29 30 VRXUFHURFNVLQWKH4L[LD7PV)RUPDWLRQZDV7& Ts/ terpane/C hopane was 0.49; relative content of C and C 29 30 21 22 (C Ts+C ) was 0.18; gammacerane/C hopane was 0.19; pregnane was 0.23; and the ratio of diasterane and regular 29 29 30 tricyclic terpane/C hopane was 3.33; relative content of C sterane was 0.07, showing a similar trend to that of the 30 21 and C pregnane was 2.62; and the ratio between diasterane 3HUPLDQFDUERQDWHVRXUFHURFNV+RZHYHUWKHELRPDUNHU DQGUHJXODUVWHUDQHZDV,Q;&VDVDPSOHRI SDUDPHWHUVRI;&VKRZHGFKDUDFWHULVWLFVLPLODUVWRWKRVH FDUERQDWHVRXUFHURFNVLQWKH&KDQJ[LQJ)RUPDWLRQV7 RI3HUPLDQFRDOPHDVXUHVRXUFHURFNVRIZKLFKV7P7ZDV Tm was 0.50; C Ts/(C Ts+C ) was 0.18; gammacerane/ 0.73; C Ts/(C Ts + C ) was 0.14; gammacerane/C hopane 29 29 29 29 29 29 30 C hopane was 0.29; tricyclic terpane/C hopane was 0.26; was 0.26; tricyclic terpane/C hopane was 2.02; relative 30 30 30 relative content of C and C pregnane was 0.09; and the content of C and C pregnane was 1.15; and the ratio of 21 22 21 22 ratio between diasterane and regular sterane was 0.06 (Table GLDVWHUDQHDQGUHJXODUWHUDQHVZDVDEOH 7 0RUHRYHU 2). Therefore there are at least two different sets of Permian VRPHELRPDUNHUSDUDPHWHUVRIWKLVUHVLGXDORUJDQLFPDWWHU VRXUFHURFNV7KHVHDUHWKH3HUPLDQFRDOPHDVXUHVRXUFH also showed similar characteristics to those from Permian URFNVLQWKH4L[LD)RUPDWLRQDQG3HUPLDQFDUERQDWHVRXUFH FDUERQDWHVRXUFHURFNV7PVVXFKDQGDV7GLDVWHUDQHUHJXODU URFNVLQWKH&KDQJ[LQJ)RUPDWLRQ7KHUHVLGXDORUJDQLF sterane. PDWWHULQWKHSRUHVRIWKH3HUPLDQUHVHUYRLUV;& $QDO\VLVRIDURPDWLFELRPDUNHUVLQZHOO;LQFKDQJ showed a unimodal distribution in saturated hydrocarbon  7DEOH VKRZHGWKDW3HUPLDQFRDOURFNVLQWKH chromatography with a ratio of low-n to high-n carbon of 4L[LD)RUPDWLRQDQGFDUERQDWHURFNVLQWKH&KDQJ[LQJ 1.37, significantly dominated by low-n carbon. In addition, )RUPDWLRQKDGDSKHQDQWKUHQHFRQWHQWRI the sample was dominated by nDONDQHDFFRUGLQJWRWKHUDWLR approaching that of organic matter in the Triassic reservoirs of isoprenoid hydrocarbon and nDONDQH,QWKLVVDPSOHV7 RIWKH)HL[LDQJXDQ)RUPDWLRQZKLFKZDV Tm was 0.93; C Ts/(C Ts+C ) was 0.28; gammacerane/ $PRQJGLEHQ]RWKLRSKHQHGLEHQ]RIXUDQIOXRUHQHDQG 29 29 29 C hopane was 0.19; tricyclic terpane/C hopane was 1.71; their homologues, the fluorene content was similar, while 30 30 relative content of C and C pregnane was 1.02; and the GLIIHUHQFHVH[LVWLQWKHFRQWHQWVRIGLEHQ]RWKLRSKHQHDQG 21 22 ratio between diasterane and regular sterane was 0.20 (Table GLEHQ]RIXUDQ+RZHYHUQRJUHDWGLIIHUHQFHVH[LVWLQ) 7KHELRPDUNHUGLVWULEXWLRQRIWHUSDQHDQGVWHUDQHVKRZHG '0) IOXRUHQHGLPHWK\OIOXRUHQH 6)3 GLEHQ]RWKLRSKHQH that the residual organic matter in the pores of the Permian SKHQDQWKUHQH RU)0)2)'0)'2)6) ÀXRUHQH reservoirs was sourced from Permian coal-measure source PHWK\OIOXRUHQHGLEHQ]RIXUDQ  GLPHWK\OIOXRUHQH URFNV GLPHWK\OGLEHQ]RIXUDQGLEHQ]RWKLRSKHQH UDWLRVRIWKH RUJDQLFPDWWHULQ3HUPLDQVRXUFHURFNVDQG7ULDVVLF XC2 reservoirs, while the organic matter in the Triassic reservoirs XC2-1 H[KLELWHGFKDUDFWHULVWLFVRI3HUPLDQVRXUFHURFNV XC2-2 XC2-11 Therefore, the hydrocarbon sources of residual organic XC2-12 matter in the Triassic reservoirs of the Feixianguan Formation XC2-13 XC2-14s ZHUHIURP3HUPLDQFDUERQDWHURFNVDQGPL[HGFRDO XC2-20 PHDVXUHVRXUFHURFNV+RZHYHUVDWXUDWHGK\GURFDUERQ XC2-23s XC2-22s chromatography proved that the three samples underwent XC2-25 a certain degree of biodegradation, indicating that the preservation conditions of these samples had been damaged in the geological history. 7KHRUJDQLFVDPSOH;&IURPD&DUERQLIHURXV reservoir showed a bimodal distribution in saturated Carbon number hydrocarbon chromatography, of which the ratio of low-n and Fig. 3 nDONDQHGLVWULEXWLRQFKDUDFWHULVWLFVRIPDULQHVWUDWDVDPSOHV high-n carbon was 0.67, indicating high-nDONDQHVGRPLQDWH IURPZHOO;LQFKDQJ The pristane/nC ratio was 0.7 with dominant nC ; the 17 17 &KURPDWRJUDSK\RIJDQLFRUPDWWHUOOLQJ¿WKHVXWXUH]RQH phytane/nC ratio was 1.03 with dominant phytane; and the LQWKH)HL[LDQJXDQ)RUPDWLRQLQZHOO;LQFKDQJ ;& pristane/phytane ratio was 0.61 with dominant phytane. The 11, 12, 13) showed a unimodal distribution in saturated saturated hydrocarbon chromatography of this sample showed hydrocarbon. The ratio between low-n and high-n carbon was FKDUDFWHULVWLFVLPLODUVWRWKDWRI6LOXULDQRXUFHVURFNV ;XHW DQGLQWKHWKUHHVDPSOHVVKRZLQJVLJQL¿FDQW DO EXWFHUWDLQIHUHQFHVGLIH[LVW6LOXULDQVRXUFHURFNV FKDUDFWHULVWLFVRIOLJKWHUDONDQHVD 7EOH  nDONDQHZDV are dominated by high-nDONDQHVLWKZVDWXUDWHGK\GURFDUERQ essentially dominant in the ratio between isoprenoid and FKURPDWRJUDSK\IURPORZWRKLJKZKLOHWKDWRI;& nDONDQHDQGSK\WDQHZDVGRPLQDQWLQWKHUDWLREHWZHHQ was from high to low with characteristics similar to that of pristane and phytane, which is a similar trend to that of the &DPEULDQVRXUFHURFNV7KHWHUSDQHDQGVWHUDQHELRPDUNHU 3HUPLDQFDUERQDWHVRXUFHURFNV+RZHYHUWKHWHUSDQHDQG parameters of this sample, including tricyclic terpane/ VWHUDQHELRPDUNHUSDUDPHWHUVRIWKHUHVLGXDOJDQLFRUPDWWHU C hopane, relative content of C and C pregnane, and 30 21 22 from the three samples from the Feixianguan Formation GLDVWHUDQHUHJXODUVWHUDQHVGLIIHUHGVLJQL¿FDQWO\IURPWKRVH Relative mass fraction, % 8 Pet.Sci.(2013)10:1-18 Abundance Abundance Sample number: XC2-11 M/Z 191 M/Z 217 450000 Depth 2848.22m Formation: T f 50000 10000 34.00 38.00 42.00 46.00 50.00 54.00 58.00 62.00 66.00 70.00 74.00 Time Time 38.00 40.00 42.00 44.00 46.00 48.00 50.00 52.00 54.00 56.00 Abundance Abundance Sample number: XC2-12 Depth: 2853.83m Formation: T f Time Time 38.00 40.00 42.00 44.00 46.00 48.00 50.00 52.00 54.00 56.00 34.00 38.00 42.00 46.00 50.00 54.00 58.00 62.00 66.00 70.00 74.00 Abundance Abundance Sample number: XC2-20 Depth: 3376.04m Formation: P c Time 34.00 38.00 42.00 46.00 50.00 54.00 58.00 62.00 66.00 70.00 Time 37.00 39.00 41.00 43.00 45.00 47.00 49.00 51.00 53.00 55.00 57.00 59.00 Abundance Abundance Sample number: XC2-23S Depth: 4607.54m Formation: P q Time Time 34.00 38.00 42.00 46.00 50.00 54.00 58.00 62.00 66.00 70.00 74.00 38.00 40.00 42.00 44.00 46.00 48.00 50.00 52.00 54.00 56.00 Sample number: XC2-25 Abundance Abundance Depth: 4623.04m Formation: C c Time 34.00 38.00 42.00 46.00 50.00 54.00 58.00 62.00 66.00 70.00 74.00 Time 38.00 40.00 42.00 44.00 46.00 48.00 50.00 52.00 54.00 56.00 Fig. 4 HUSDQHDQGVWHUDQHELRPDUNHUGLDJUDPRIVDPSOHVIURPZHOO;LQF7 KDQJ REVHUYHGLQ3HUPLDQVRXUFHURFNV geochemical characteristics evident in the sample show We consider that the main hydrocarbon sources of WKDWWKH&DUERQLIHURXVDQG3HUPLDQURFNVRQFHZHUHSDUWRI WKH&DUERQLIHURXVUHVHUYRLUVLQZHOO;LQFKDQJZHUH WZRGLIIHUHQWIOXLGV\VWHPVWKDWLV3HUPLDQURFNVDQGWKH 6LOXULDQDQG&DPEULDQVRXUFHURFNV6HYHUHELRGHJUDGDWLRQ underlying strata were completely disconnected before the occurred in the sample; thus, preservation conditions of K\GURFDUERQJHQHUDWHGLQ&DPEULDQRXUFHVURFNVPLJUDWHGWR the petroleum system were damaged. The present organic WKH&DUERQLIHURXVURFNV Pet.Sci.(2013)10:1-18 9 4.2 Organic geochemical tracers in the marine strata The carbon isotope analysis of the natural gas from the of the Longjuba structure well Long 8 in P m Formation indicates that the natural gas is overmatured dry and sapropelic gas (Table 5), with a high 0HWKDQHLVWKHGRPLQDQWQDWXUDOJDVFRPSRQHQWRIWKH PHWKDQHFDUERQLVRWRSHUDWLR)URPWKHFURVVSORWRIį C and 3HUPLDQ0DRNRX)RUPDWLRQLQWKHZHOO/RQJ/RQJMXED į C (Fig. 5), it can be seen that the natural gas from the well VWUXFWXUHDFFRXQWLQJIRU1 and CO were second 2 2 Long 8 P m Formation and the natural gas from P m, P ch and 1 1 2 and third, respectively. The content of ethane was lower at T f formations in eastern Sichuan are basically distributed QR+ S was detected (Table 4). in the same area in the cross-plot, which indicates that the 7KHFDUERQLVRWRSHVRIWKH&+ LVLQÀXHQFHGE\WKHW\SHV 3HUPLDQVRXUFHURFNVKDYHDOVRPDGHVRPHFRQWULEXWLRQWR ZKLFKUHVXOWVLQDQRIWKHVRXUFHURFNVLQDGGLWLRQWRPDWXULW\ the formation of natural gas from the P m Formation in well RYHUODSRIWKHį C distribution interval of coal-type and oil- Long 8. The cause of the reversal of methane and ethane W\SHJDVHVFODVVL¿HGDVKXPLFDQGVDSURSHOLFUHVSHFWLYHO\ ratios might be the mixing of different natural gases from $VDUHVXOWLWLVGLI¿FXOWWRGHWHUPLQHWKHIHUHQFHGLIEHWZHHQ IHUHQWVRXUFHURFNVGLI WKHVHJDVW\SHVXVLQJį C . The carbon isotope ratio in heavy hydrocarbons of natural gas, such as ethane, is more Table 77KHFODVVL¿FDWLRQRIFDUERQLVRWRSHVLQPDULQHQDWXUDOJDV VWDEOH7KLVFDQDFFXUDWHO\UHÀHFWWKHW\SHVRIJDVJHQHUDWLQJ 13 13 materials. By examining criteria based on the carbon isotope Types į C , ‰ į C , ‰ 2 1 analysis of 283 continental and marine samples from 8 basins mature <-40 Sapropelic <-34.0 LQ&KLQD 6KLHWDO;XHWDO'DL=KDQJ overmature >-40 et al, 1987; 1988) in addition to research data of the natural mature <-40 +XPLFEHDULQJ -34.0 - -29.5 sapropelic overmature >-40 gas in marine sediments in the Tarim Basin (Zhao et al, 2001; mature <-32 /LDQJHWDOLH;HWDO ZHHVWLPDWHGWKHJHQHWLF +XPLF >-29.5 overmature >-32 types of natural gas (Table 7). -26 East Sichuan Basin, T f Humic East Sichuan Basin, P ch -28 gas (North) Jian 51 East Sichuan Basin, P m -30 East Sichuan Basin, C hl T f 2 Pch P ch Feixianguan Feix Changxing Changxing 1 Humic bearing Jiannan gas field, T j Formation Fo Formation Formation sapropelic gas -32 Jiannan gas field, T f L Longjuba Lo Jiannan gas field, P ch P m -34 Jiannan gas field, C Jian Jian an 44 44 44 4 4 Longjuba structure, P m -36 1 P m Maokou Formation Jian Jian Jian Jian 43 43 43 43 Jian Jian Jian Jian 10 10 10 10 Sapropelic gas -38 Jian 27 C C Jian Jian Jian 25 25 25 Carboniferous T f, T j, P ch 1 1 2 Jian 43 -40 Jian 28 28 Jian Jian 28 (South) -42 Jian 61 Jian 34 -44 -39 -38 -37 -36 -35 -34 -33 -32 -31 -30 -29 į C1, ‰ /RQJMXEDVWUXFWXUH-LDQQDQJDV¿HOG0HWKDQHDQGHWKDQHFDUERQLVRWRSHUDWLRVRIQDWXUDOJDVLQWKH Fig. 5 and eastern Sichuan Basin Through the matrix-source-judging formula proposed FDOFXODWLRQWKHPDWXULW\RIWKHVRXUFHURFNVLV by Pang et al (2000), with the methane carbon isotopes and ZLWKDQDYHUDJHYDOXHRI7KHDVSKDOWUHIOHFWDQFHRI the components of the natural gas from the well Long 8, WKHGDUNJUH\ELRFODVWLFOLPHVWRQHVDWDGHSWKRIP st WKHJDVW\SHLQGH[ *7, DQGNHURJHQW\SHLQGH[ .7, DUH in the well Long 8 of the 1 HFWLRQVRIWKH3HUPLDQDRNRX0 obtained and listed as follows: the GTI is 0.339; the KTI is )RUPDWLRQLV$IWHUFRQYHUVLRQLWVYLWULQLWHUHÀHFWDQFH $OOWKHGDWDLQGLFDWHWKDWWKHQDWXUDOJDVRULJLQDWHGIUR P LV7KHFDOFXODWHGPDWXULW\RIWKHVRXUFHURFNVZKLFK WKHUHODWLYHO\KLJKTXDOLW\VRXUFHURFNV2QWKHEDVLVRIRXU formed the methane found in the well is not in agreement C ,‰ 2 10 Pet.Sci.(2013)10:1-18 ZLWKWKHPHDVXUHGPDWXULW\RIWKHVRXUFHURFNVIURPWKH such a reversal is due to a higher degree of maturity. Instead, 3HUPLDQ0DRNRX)RUPDWLRQEXWLWLVFORVHUWRWKHPDWXULW\ we consider it is due to the mixing of sources. RIWKHVRXUFHURFNVIURPWKHLOXULDQ6PXGURFNV7KHYLWULQLWH The carbon isotopes of the natural gas generated from UHÀHFWDQFHRIWKHVRXUFHURFNVIURPWKHLOXULDQ6LQWKHVWXG\ Carboniferous of Jiannan gas field are lighter. The average 13 13 DUHDLV /LXHWDO 7KHQDWXUDOJDVIURPWKH C C 1 2 Long 8 well in P m Formation is a mixed product from both HTXDOVWRRULVOHVVWKDQÅZKLFKLVREYLRXVO\OLJKWHU Silurian mudstones and Permian carbonates sources. than those of the natural gas samples from the Permian, the Triassic and the Carboniferous of eastern Sichuan. The 4.3 Organic geochemical tracers in marine strata of natural gas in eastern Sichuan is mainly generated from the Jiannan structure 6LOXULDQRXUFHVURFNV =KXHWDO 7KHQDWXUDOJDVIURP the Carboniferous of Jiannan might be the product of the 7KHQDWXUDOJDVGU\LQJFRHI¿FLHQW & /C -C ) of the four 1 1 5 PL[LQJRIJDVIURPRWKHURXUFHVURFNVVXFKDVWKH&DPEULDQ production formations (Jialingjiang, Feixianguan, Changxing VRXUFHURFNVDWWKHGHHSHUSDUWRUWKHRWKHUSDUWVRIWKH DQG+XDQJORQJ LQ-LDQQDQJDVILHOGLVDERYHZLWKD formation. The reversal of the carbon isotope of the natural PD[LPXPYDOXHRILQGLFDWLQJDQRYHUPDWXUHGU\JDV gas also occurs. 7KHQDWXUDOJDVLQ&DUERQLIHURXVURFNVKDVDUHODWLYHO\KLJK R7VWXG\WKHVRXUFHURFNVLQJUHDWHUGHWDLOZHXVHGWKH C FRQWHQWZLWKDVPDOOTXDQWLW\RI&   DQG 2 3 FDUERQLVRWRSHYDOXHVRIWKHNHURJHQLQYDULRXVVHWVRIVRXUFH its CO DQG+ 6FRQWHQWVDUHERWKEHORZDEOH 7 2 2 URFNVLQWKHHDVW6LFKXDQ%DVLQDQGFRPSDUHGWKHPZLWK 7KHFRPSRVLWLRQVRIQDWXUDOJDVLQYDULRXVKRUL]RQVRIWKH WKHį C RIQDWXUDOJDVLQWKH-LDQQDQJDV¿HOG )LJ 7KH -LDQQDQJDV¿HOGHUHZEDVLFDOO\WKHDPHVZLWKDKLJKFRQWHQW 1 NHURJHQLQOLPHVWRQHVDPSOHVRI3 l, P T3 m, and P w was of methane and low contents of ethane, propane, and other 1 1 1 2 DPL[HGW\SHZLWKWKHDYHUDJHį C between -26.8‰ heavy hydrocarbon components, showing it is post-mature NHURJHQ DQGÅZKLFKLVÅÅKHDYLHUWKDQWKHį C value S\URO\VLVJDV+RZHYHUVXFKFRPSRQHQWFKDUDFWHULVWLFVDUH 1 in T f in the northern high point (-30.8‰ - -32.1‰), which IHUHQFHVLQJHQHVLVXQDEOHWRUHÀHFWGLI 1 corresponds to the fractionation during the alteration from The isotope ratios of methane in the natural gas from NHURJHQWR&+ . The natural gas of the T f Formation in the the P m, P ch and T f formations in the Jiannan gas field 4 1 1 2 1 QRUWKHUQKLJKSRLQWRULJLQDWHGIURPPL[HGW\SHRXUFHVURFNV DUHKLJKEHWZHHQDQGZKLFKLQGLFDWHVWKDWWKH classified as mainly sapropelic. The shale in P l, P w, and evolutionary degree of the natural gas is high. In comparison, 2 2 P d and the bioclastic limestone in P ch were humic with a WKHLUHWKDQHLVRWRSHVDUHZLGHO\GLVWULEXWHGZLWKVWULNLQJ 2 2 VLJQL¿FDQWO\KHDY\į C value, the average of which was differences being displayed in the high points of the south and NHURJHQ betweenÅDQGÅ7KHį C value in these WKHQRUWK7KHį C in the high point of the north is heavier, NHURJHQ IRXUIRUPDWLRQVZDVÅÅKHDYLHUWKDQWKHį C value in ZLWKDQDYHUDJHYDOXHRIZKLFKXJJHVWVVWKDWPRVWRI 1 the Permian and Triassic natural gas with the maximum at the natural gas is from humus-bearing sapropels, with only a 10‰, indicating that these four formations are not the source few exceptions, some of which might be sapropelic gas. The of the Permian and Triassic natural gas in the Jiannan gas į C in the high point of the south is lighter, with an average ¿HOG)RUWKLVUHDVRQLWFDQEHDVVXPHGWKDWWKHQDWXUDOJDV YDOXHRIZKLFKVXJJHVWVWKDWWKHQDWXUDOJDVLV from the Permian and the Triassic in the Jiannan gas field VDSURSHOLFJDV )LJDEOHDQG 7$OOWKHGDWDLQGLFDWHWKDW the genesis and the sources of the natural gas are complicated. 13 13 )URPWKHFURVVSORWRIį C DQGį C (Fig. 5), it can be seen 1 2 that the distribution of carbon isotopes of the natural gas T j 3 1 T f from the P ch and T f IRUPDWLRQVLQWKH-LDQQDQJDV¿HOGDQG 2 1 III -31.8 the distribution of carbon isotopes of the natural gas from -32.3 P d P ch -32.4 the Carboniferous in eastern Sichuan basically overlap but -25.2 P ch 2 II some differences are shown in the distribution of the carbon P w P m -32.7 isotopes of the natural gas from T f and P ch formations in the 1 2 -25.1 -23.2 -26.8 P l LQHDVWHUQ6LFKXDQLVPDLQO\IURPVDSURSHOLFVRXUFHURFNV -24.2 -23.5 P l P q-P m from the lower part of the Silurian system (Dai et al, 2010), 2 1 1 the natural gas from the P ch and T f formations in the -28.3 2 1 -27.5 -36.8 O -S 3 1 -29.5 SDUWRIWKH6LOXULDQV\VWHP+RZHYHUWKHFRQWULEXWLRQRI VRXUFHURFNVIURPWKH3HUPLDQV\VWHPFDQQRWEHLJQRUHG7KH -31.6 higher ethane carbon isotope ratios of the gas samples from the north points of P ch and T f formations indicate a greater 2 1 -40 -38 -36 -34 -32 -30 -28 -26 -24 -22 -20 FRQWULEXWLRQIURPWKH3HUPLDQVRXUFHURFNV+XPLFJDVLV į C, ‰ even found in the well No.51 in T f Formation of Jiannan gas Natural gas Kerogen type Type I Type II Type III Coal methane ¿HOG7KHUHYHUVDORIWKHFDUERQLVRWRSHVRIWKHJDVIURP3 ch and T f formations of Jiannan gas field mostly occurs, the Fig. 6&RPSDULVRQRIį C of the natural gas in the Longjuba structure and 1 1 -LDQQDQJDV¿HOGDQGį C LQVRXUFHURFNVLQWKHHDVWHUQ6LFKXDQ%DVLQ only difference being the degree. Some scholars maintain that NHURJHQ LVDOVRPDLQO\IURPVRXUFHURFNVRIWKHORZHU -LDQQDQJDV¿HOG RWKHUSDUWVRIWKHDUHD$VWKHQDWXUDOJDVLQWKH&DUERQLIHURXV LVÅDQGWKHDYHUDJHYDOXHRIWKHį YDOXHRIWKHį Pet.Sci.(2013)10:1-18 11 LVJHQHUDWHGPDLQO\IURP6LOXULDQVRXUFHURFNVDQGSDUWRI bearing series. The natural gas from the Carboniferous LWLVJHQHUDWHGIURP3HUPLDQPL[HGVRXUFHURFNVPDLQO\ IRUPDWLRQVZDVPDLQO\JHQHUDWHGLQWKHVRXUFHURFNVRIWKH VDSURSHOLFVRXUFHURFNV7KH3HUPLDQKXPXVEHDULQJVRXUFH 6LOXULDQV\VWHPDQGWKH&DPEULDQVRXUFHURFNVKDYHDOVR URFNVKDYHPDGHOHVVFRQWULEXWLRQWRWKHIRUPDWLRQRIWKH contributed to it. QDWXUDOJDVRIWKHDUHD7KHDYHUDJHį C values of the NHURJHQ 5 Fluid migration paths UHVSHFWLYHO\VRFODVVL¿HGDVVDSURSHOLFNHURJHQ7KHQDWXUDO To more accurately trace the fluid migration paths, a gas in the Carboniferous is typical sapropelic natural gas with SUR¿OHZDVVHOHFWHGIURPDQ[LDQ:QRUWKZHVWWR;LDRTLQJ\D LWVį C value below -40‰; its gas sources are the sapropelic southeast that essentially includes the Fangdoushan and VRXUFHURFNVLQWKH&DPEULDQDQGWKH6LOXULDQ 4L\XHVKDQIDXOW]RQHVWKH-LDQQDQVWUXFWXUHDQGRWKHU Comprehensive analysis shows that the natural gas in WHFWRQLF]RQHV7KURXJK )LJDQDO\VLV D RIÀXLGPLJUDWLRQ the Jiannan gas field is mainly sapropelic; that the natural SDWKVRIWKUHHW\SLFDOVWUXFWXUHV²;LQFKDQJ/RQJDQG gas from P ch and T f formations was mainly generated in Jian 38 wells, hydrocarbon accumulation and migration 2 1 were examined, the formation, evolution, destruction and VRXUFHURFNVDVLWVHFRQGDU\VVRXUFH$SHFL¿FVVDPSOHIURP modification of different structures were studied, and well No. 51 in T f Formation of Jiannan gas field displays hydrocarbon preservation conditions were evaluated in this VRPHUHODWLRQZLWKWKH3HUPLDQVRXUFHURFNVRIWKHFRDO area. (a) Regional cross-section Jiannan Xinchang Longjuba structure structure structure SE 0 10km Jian3 well Xinchang2 well Long8 well Depth, m J-T 5000 P Fangdoushan fault belt Qiyueshan fault belt Decollement fold zone of baffle structure in East Sichuan (c) Pathways of fluid movement in Longjuba structure (d) Pathways of fluid movement in Jiannan structure (b) Pathways of fluid movement in Xinchang structure Elevation, m Xinchang2 well Elevation, m Long8 well Elevation, m Jian38 well 0 0 1000 T T C 6000 O 4000 O C 8000 D+C Formation and Fluid charge Fluid charge Reverse fault in early period stratigraphic unit in late period )OXLGPLJUDWLRQSDWKVLQPDULQHVWUDWDRIWKHZHVWHUQ+XEHL±HD VWHUQ&KRQJTLQJDUHD Fig. 7 5.1 Fluid migration path in Xinchang structure of strontium isotopic ratio used in this study is applicable to rRFNVLQVRXWKHUQ&KLQD 87 86 The Sr/ Sr value of normal paleo-seawater in the $FFRUGLQJWRVWXGLHVRQFDUERQR[\JHQDQGVWURQWLXP Early Triassic (the similar sedimentary age of Jialingjiang isotopes in the Permian Changxing Formation of well )RUPDWLRQ VLPXODWHGE\0F$UWKXU  DQG.RUWHHW ;LQFKDQJDEOH 7 VLJQL¿FDQWIHUHQFHVGLIZHUHREVHUYHG al (2005a; 2005b) ranged from 0.7076 to 0.7082; that of LQWKHR[\JHQLVRWRSHVDQGZHDNGLIIHUHQFHVZHUHREVHUYHG seawater (the similar sedimentary age of Daye Formation) in carbon isotopes. These studies implied that the fluids VLPXODWHGE\5HLQKDUGWHWDO  HL]HUDQG9HWDO leading to vein formation were not sourced from the products ranged from 0.7076 to 0.7078; and that of Early Permian RIDGMDFHQWVXUURXQGLQJURFNVDIWHUUHGLVVROXWLRQ+RZHYHU 87 86 QRUPDOVHDZDWHUUDQJHGIURPWR$QDO\VLVZDV the Sr/ Sr value of gypsum filling spaces in the Permian performed on strontium isotopic composition and evolution Changxing Formation (0.7100) was close to the strontium RI/DWHULDVVLF3HUPLDQí(DUO\7VHDZDWHULQPDULQHFDUERQDWH isotope of Early Cambrian seawater, which was reported as URFNVLQ=KRQJOLDQJVKDQ&KRQJTLQJUHSRUWHGE\+XDQJHWDO %XUNHHWDOHQLVRQ'HWDOKL6HW (2008). The conclusions were consistent with those published DORUWH.HWDO 7KHVHUHVXOWVLQGLFDWHWKDWÀXLGV by Korte et al (2003; 2005a; 2005b), proving that the criterion leading to the formation of gypsum were sourced from lower 6LOXULDQVRXUFHURFNVZLWK3HUPLDQKXPXVEHDULQJVDSURSHOLF NHURJHQLQWKH&DPEULDQDQG6LOXULDQDUHÅDQGÅ 12 Pet.Sci.(2013)10:1-18 Cambrian strata. 5.2 Fluid migration path in Longjuba structure Previously accumulated calcium-carbonate-rich fluids $QDO\VLVRIFDUERQDQGR[\JHQLVRWRSHVIURPWKH3HUPLDQ ZHUHVRXUFHGIURP3HUPLDQURFNVZLWKDEXQGDQWRUJDQLF in the well Long 8, indicated that although carbon and inclusions (Fig. 9(a)), indicating that the Permian source URFNVUHDFKHGWKHSHDNRIK\GURFDUERQJHQHUDWLRQDWWKLV Bitumen VWDJH7KHKRPRJHQL]DWLRQWHPSHUDWXUHSHDNVRIFRH[LVWLQJ saline inclusions were 120-130 °C and 160-190 °C (Fig. 9(b)), corresponding to the depths of hydrocarbon migration and accumulation at 3,333-3,667 m and 4,666-5,667 m, UHVSHFWLYHO\$FFRUGLQJWRWKHK\GURFDUERQJHQHUDWLRQ KLVWRU\RI8SSHU3HUPLDQVRXUFHURFNVVLPXODWHGE\WKH (DV\ R FKHPLFDONLQHWLFPRGHO )LJ D WKH R value o o RIVRXUFHURFNVUDQJHGIURPWRLQWKHPLGGOH /DWHULDVVLF7WKHURFNVZHUHEXULHGPLQWKLVVWDJH of abundant hydrocarbon generation. In the initial Early -XUDVVLFWKHPDWXULW\RIWKHVRXUFHURFNVZDVDERXW Calcite DWZKLFKVWDJHK\GURFDUERQJHQHUDWLRQUHDFKHGLWVSHDN,Q (a) WKHPLGGOH(DUO\-XUDVVLFWKHPDWXULW\RIVRXUFHURFNVZDV DWZKLFKVWDJHJDVJHQHUDWLRQRFFXUUHG,QWKHODWH Early Jurassic, R YDOXHZDVDWZKLFKWDJHVVLJQL¿FDQW JDVJHQHUDWLRQRFFXUUHGLQHUPLDQ3RXUFHVURFNV0HDQZKLOH Gypsum LQFOXVLRQFKDUDFWHULVWLFVDQGKRPRJHQL]DWLRQWHPSHUDWXUHV also show that two-stage hydrocarbons were captured in Permian reservoirs (P ch ) in the initial and the late epochs of the Early Jurassic. 5HVLGXDOELRPDUNHUFKDUDFWHULVWLFVRIRUJDQLFPDWWHU obtained from the fractures of the third member of Feixianguan Formation, show its source was Permian source URFNV7KHWLPHRIIRUPDWLRQRIWKHJDQLFRUPDWWHUOOLQJ¿WKH UHVHUYRLUIUDFWXUHVVKRXOGEHHTXLYDOHQWWRWKHFDSWXUHWLPH Calcite of vein inclusions in reservoir fractures of the lower Triassic Feixianguan Formation because both have the same set of VRXUFHURFNV )LJ D (b) 7KHJ\SVXPOOLQJ¿WKHUHVHUYRLUIUDFWXUHVRIWKH3HUPLDQ Changxing Formation has been proved to be sourced from WKHXQGHUO\LQJ&DPEULDQ$ODUJHDPRXQWRIZDWHUVROXEOH 02cm methane exists in the inclusions along indistinct fractures in J\SVXP )LJ F LQGLFDWLQJWKDW&DPEULDQVRXUFHURFNV evolved to hydrocarbon expulsion with a high maturity or to a generation stage of abundant dry gas. The vein-filling VHTXHQFHVKRZVWKHIRUPDWLRQRIJ\SVXPDVZODWHUWKDQWKDW RIWKHFDOFLWH )LJ E $JHODUDPRXQWRIQDWXUDOJDVDQG calcium-sulfate-rich water generated in Cambrian source URFNVPLJUDWHGWRWKHRYHUO\LQJ3HUPLDQUHVHUYRLUVWKHPDLQ pathway of which was probably faults and fractures generated by Yanshan tectonism. In addition, the residual organic ELRPDUNHUVDORQJ&DUERQLIHURXVUHVHUYRLUIUDFWXUHVKDYH FKDUDFWHULVWLFVRI&DPEULDQDQG6LOXULDQVRXUFHURFNV $WOHDVWWZRVWDJHVRIÀXLGDFFXPXODWLRQRFFXUUHGLQWKH Bitumen Calcite 3HUPLDQUHVHUYRLUVRIWKH;LQFKDQJVWUXFWXUH )LJ E $W (c) WKHHDUO\WDJHVWKHFDOFLXPFDUERQDWHULFKXLGÀZDVVRXUFHG IURPWKH3HUPLDQDQGIRUPHGWKHFDOFLWH$WWKHODWHVWDJH &RUHSKRWRVRIZHOO;LQFKDQJDQGZHOO-LDQ D 7KH Fig. 8 YHLQ¿OOLQJVHTXHQFHRIWKHUHVHUYRLULQULDVVLF/RZHU7HL[LD) QJXDQ WKHFDOFLXPVXOIDWHULFKXLGÀZDVVRXUFHGIURPWKH&DPEULDQ )RUPDWLRQ DWWKHGHSWKRIP RIWKH;LQFKDQJZHOO WKH DQGIRUPHGWKHJ\SVXP0RUHRYHUWKHODWHUDFFXPXODWHG FDOFLWHILOOHGEHIRUHWKHELWXPHQ  E 7KHYHLQILOOLQJVHTXHQ FHRI ÀXLGVPDGHFHUWDLQPRGL¿FDWLRQVWRWKHÀXLGVJHGHDUOLHUFKDU the reservoir in Upper Permian, Changxing Formation (at the depth Earlier hydrocarbon preservation conditions were damaged RIP RIWKH;LQFKDQJZHOO WKHFDOFLWH¿OOHGEHIRUH WKH JHVFDOHFURVVIRUPDWLRQDOÀRZRIE\WKHORQJGLVWDQFHDQGODU J\SVXP  F 7KHYHLQILOOLQJVHTXHQFHRIWKHUHVHUYRLULQ/RZH U ÀXLGVOHDGLQJWRHULRXVVSUREOHPVIRURLODQGJDVH[SORUDWLRQ Triassic, Feixianguan Formation (at the depth of 3,151.42 m) of the LQWKH;LQFKDQJVWUXFWXUH -LDQZHOO WKHFDOFLWH¿OOHGEHIRUHWKHELWXPHQ  Pet.Sci.(2013)10:1-18 13 P m 4784.48 m 140-150 °C V- V- LL (e) 2914.97 (a) 25% 2608.1 20% 2755.77 2637.8 2682.04 2880.05 2775.94 2826.06 2650.07 2741.47 2863.19 2810.9 15% 2650 2700 2750 2800 2850 2900 2950 -1 Raman shift, cm 10% (f) 5% 0% Homogenization temperature, °C (b) 2912.07 (g) 70% 999.762 2604.96 60% 50% 40% 1158.55 30% 20% 1000 1500 2000 2500 3000 -1 10% Raman shift, cm 0% (c) 130-135 135-145 140-145 145-150 Homogenization temperature, °C P ch (h) 4314.67 m 130-170 °C 2914.2 V-L 1086.64 LCH -H S 4 2 1000 1500 2000 2500 3000 LCH 4 -1 Raman shift, cm (d) (i) Fig. 9KRWRV3KRPRJHQL]DWLRQWHPSHUDWXUHDQGODVHU5DPDQSHFWUDVRIÀXLGLQFOXVLRQV D 7KHJDQLFRUÀXLGLQFOXVLRQVRIFDOFLWHVYHLQLQHUPLDQ3UHVHUYRLU IUDFWXUHVRIVDPSOH ;&P3 FK ;LQFKDQJZHOO E +RPRJHQL]DWLRQWHPSHUDWXUHGLVWULEXWLRQGLDJUDPRIÀXLGLQFOXVLRQVLQFDOFLWHYHLQV RI3HUPLDQUHVHUYRLUV DWWKHGHSWKRIP RIWKHDQJ;LQFKZHOO F /DVHU5DPDQSHFWUDVRIJDQLFRULQFOXVLRQVLQHWKVHFRQGPHPEHURIWKH8SSHU Permian Changxing Formation (P ch RIWKH;LQFKDQJZHOO G )OXLGLQFOXVLRQVLQFDOFLWHYHLQV ¿OOLQJUHVHUYRLUIUDFWXUHVRIWKH&KDQJ[LQJ)RUPDWLRQ /RQJZHOO H )OXLGLQFOXVLRQVRIFDOFLWHYHLQV¿OOLQJ3HUPL DQUHVHUYRLUIUDFWXUHVRIWKH0DRNRX)RUPDWLRQZHOO/RQJ /DVHU I5DPDQSHFWUDJDQLFVRIRU LQFOXVLRQVLQWKHYHLQVRIWKH0DRNRX)RUPDWLRQZHOO/RQJ J *DVOLTXLGVDOLQHLQFOXVLRQVFRH[LVWLQJZLWKRUJDQLFLQFOXVLRQVZKLFKDUHGDUNJUD\ VLQJOHSKDVHGDQGLQWKHKDSHVRIUHFWDQJOHDOLQH6LQFOXVLRQVDUHOLTXLGDQGJDVSKDVHGKRUL]RQ7 f GHSWKPHOOZ-LDQ K +RPRJHQL]DWLRQ WHPSHUDWXUHGLVWULEXWLRQGLDJUDPRIÀXLGLQFOXVLRQVLQWKHWKLUGPHPEHURIWKH/RZHUULDVVLF7)HL[LDQJXDQ)RUPDWLRQ 7 f ) of the well Jian 38. (i) Laser 3 -1 -1 Raman spectra of organic inclusions in the third member of Lower Triassic Feixianguan Formation (T f ) of the well Jian 38; 2914.2 cm and 1086.64 cm UHIHUWR&+ LQWKLV¿JXUHDQGFDOFLWHUHVSHFWLYHO\ 90-100 100-110 110-120 120-130 130-140 140-150 150-160 160-170 170-180 180-190 190-200 200-210 Counts Counts Counts 14 Pet.Sci.(2013)10:1-18 400 360 320 280 240 200 160 120 80 40 0 Time, Ma Depth, PALEOZOIC MESOZOIC CENOZOIC Fm Pg Ng SD C P Tr J K T x 1000 3 0.40%R T b 0.60%R T j T f P ch P m P q 0.80%R S h S x 1.20ˁR S l 1.60ˁR 2.00ˁR 2.40ˁR 2.80ˁR (a) 400 360 320 280 240 200 160 120 80 40 0 Time, Ma Depth, CENOZOIC PALEOZOIC MESOZOIC Fm SD C P Tr J K Pg Ng T x T b 0.40%R T j T f 4000 1 0.80%R P ch P m P q 5000 1 S h 1.20%R S x o 1 S l 1.60%R 1 2.00%R 2.40%R 2.80%R 3.20%R (b) %XULDOKLVWRU\DQGK\GURFDUERQJHQHUDWLRQKLVWRU\RIVRXUFHURFNV Fig. 10 R[\JHQLVRWRSHVRIYHLQVDQGVXUURXQGLQJURFNVUDQJHGLQWKH respectively; those of P ch ranged from -1.5‰ to 4.5‰ and VFRSHRIQRUPDOVHDZDWHUGXULQJWKHVDPHSHULRGį C and from -6.5‰ to 0‰, respectively (Korte et al, 2005a; 2005b). į O of P m ranged from -2‰ to 6‰ and from 6‰ to 0‰, +RZHYHUVLJQL¿FDQWIHUHQFHVGLIH[LVWLQFDUERQDQGR[\JHQ 1 Pet.Sci.(2013)10:1-18 15 DEOHLVRWRSHVEHWZHHQ3HUPLDQYHLQVDQGVXUURXQGLQJURFNV 7 through petrography. The accumulation of Permian fluids 6). It was shown that the fluids leading to the formation of was prior to that of hydrocarbons generated in the underlying veins were not directly sourced from the fluids of adjacent 6LOXULDQVRXUFHURFNV,IWKHDFFXPXODWLRQRIK\GURFDUERQV VXUURXQGLQJURFNV7KHIOXLGVILOOLQJWKHIUDFWXUHVRIWKH JHQHUDWHGLQWKHVHVRXUFHURFNVZDVHDUOLHUWKHQWUDFHVRI 0DRNRX)RUPDWLRQ 3 m) and Changxing Formation (P ch ) 6LOXULDQÀXLGVVKRXOGEHUHWDLQHGLQWKH3HUPLDQFDOFLWHYHLQV 1 2 87 86 had Sr/ Sr values of 0.7071, within the strontium isotope 7KHUHIRUHWKHDFFXPXODWLRQRI6LOXULDQXLGVÀDVZODWHUIURP UDQJHRI/DWH3HUPLDQVHDZDWHU %XUNHHWDO'HQLVRQ short-distance cross-formational migration of natural gas to HWDO6KLHWDO.RUWHHWDO 7KLV¿QGLQJ the Permian reservoirs. Tectonism was not very intense, and indicates that the fluids in Lower Permian were sourced the faults and fractures were only able to connect the Silurian from the overlying Upper Permian. The fluids in the Upper DQG3HUPLDQXLGV7KHÀVLJQL¿FDQWO\GHHS3HUPLDQUHVHUYRLUV Permian were not directly sourced from adjacent surrounding DQGWKLFNRYHUO\LQJJ\SVXPKDOLWHEHGVDOORZHGK\GURFDUERQ URFNVEXWIURPRWKHUSDUWVLQ3HUPLDQUHVHUYRLUV preservation conditions to partially remain in this structure. $OOIOXLGVRIYHLQVILOOLQJ3HUPLDQUHVHUYRLUVRIWKHZHOO Exploration results have shown Longjuba to be a gas-bearing Long 8 were sourced from the Late Permian. The inclusions structure. in calcite veins of Changxing Formation samples (4,314.67 5.3 Fluid migration path in the Jiannan structure P FRQVLVWHGRIJDVOLTXLGVDOLQHZDWHUVROXEOH&+ + S, 4 2 DQG&+ inclusions (Fig. 9(d)). These results indicate that 4 'U\EODFNELWXPHQZDVGLVFRYHUHGLQFDOFLWHYHLQV¿OOLQJ ÀXLGDFFXPXODWLRQRFFXUUHGDWWKHSHDNWDJHVRIK\GURFDUERQ micrite fractures adjacent to the third-member Lower Triassic JHQHUDWLRQDWZKLFKWLPHWKHKRPRJHQL]DWLRQWHPSHUDWXUH Feixianguan Formation of the well Jian 38 in the Jiannan of coexisting saline inclusions ranged between 130 °C VWUXFWXUH P 7KHFDOFLWHZDV¿OOHG¿UVWIROORZHG and 170 °C, corresponding to hydrocarbon migration and by bitumen, leading to a significant time order with a vein accumulation depths between 3,667 m and 5,000 m. width of 2-4 mm. Carbon, oxygen, and strontium isotopes The fluid inclusions in calcite veins filling the reservoir RIYHLQVDQGVXUURXQGLQJURFNVLQWKLVIRUPDWLRQZHUHLQWKH fractures of the first member of the Lower Permian UDQJHRI(DUO\ULDVVLF7 QRUPDOVHDZDWHUDEOH 7  %XUNH 0DRNRX)RUPDWLRQ P PDLQO\FRQVLVWHGRIJDV HWDO'HQLVRQHWDO LQGLFDWLQJQRLQÀXHQFHRQ OLTXLGRUJDQLFLQFOXVLRQV )LJ H  I DWZKLFKWLPHWKH WKHVHLVRWRSHVLQVXUURXQGLQJURFNVDQGYHLQV+RZHYHU KRPRJHQL]DWLRQWHPSHUDWXUHSHDNUDQJHGEHWZHHQƒ& VLJQL¿FDQWIHUHQFHVGLIH[LVWHGLQFDUERQDQGR[\JHQLVRWRSHV and 150 °C and the hydrocarbon accumulation depth was EHWZHHQYHLQVDQGVXUURXQGLQJURFNV7KHIOXLGVOHDGLQJWR estimated at between 4,000 m and 4,330 m. The hydrocarbon the formation of veins were probably sourced from external 87 86 JHQHUDWLRQKLVWRU\RI3HUPLDQVRXUFHURFNVLQWKH/RQJ IOXLGVUDWKHUWKDQIURPWKHVXUURXQGLQJURFNV7KH Sr/ Sr well (Fig. 10(b)), indicates that hydrocarbon generation YDOXHRIWKHVXUURXQGLQJURFNV  ZDVFRQVLVWHQW RFFXUUHGLQHUPLDQ3RXUFHVURFNVLQWKHODWH0LGGOHULDVVLF7 with that of Early Triassic normal seawater (0.7076), which DQGUHDFKHGWKHSHDNVWDJHLQWKHHDUO\/DWHULDVVLF7ZLWKD LQGLFDWHVWKDWWKHVXUURXQGLQJURFNVZHUHQRWLQIOXHQFHGE\ corresponding R YDOXHRI*DVJHQHUDWLRQEHJDQLQWKH o H[WHUQDOÀXLGVZKLOHPRUHVWURQWLXPLVRWRSLFFKDUDFWHULVWLFV ODWH0LGGOH-XUDVVLFZLWKDFRUUHVSRQGLQJ R YDOXHRI o of seawater in the original sedimentation were retained. The 87 86 )URPWKHLQFOXVLRQFKDUDFWHULVWLFVDQGKRPRJHQL]DWLRQ Sr/ Sr value of veins (0.7075) was also close to the high 87 86 temperatures, we deduce that hydrocarbons were primarily value of Sr/ Sr in Late Permian seawater (0.7067-0.7076), captured in the Permian reservoirs of the well Long 8 during indicating that the fluids leading to the formation of veins WKHHDUO\0LGGOH-XUDVVLF+RZHYHUWKHFRPSRVLWLRQDQG could be sourced from the Lower Triassic and the Upper isotopic characteristics of natural gas in the Permian in this Permian strata. well suggest that the natural gas is mainly from Silurian and 3HUPLDQVRXUFHURFNV7KHUHIRUHPXOWLVRXUFHDQGPXOWL limestone fractures of the third-member (T f ) Lower Triassic stage hydrocarbons were captured in Permian reservoirs. Feixianguan Formation (3,153.20 m) mainly consisted of gas- The Permian reservoirs of the Longjuba structure were OLTXLGDQGJDQLFRULQFOXVLRQV )LJ J 7KHJDVOLTXLGÀXLG PDLQO\FKDUDFWHUL]HGE\WZRVWDJHIOXLGDFFXPXODWLRQ LQFOXVLRQVZHUHȝPLQVL]HDQGWKHKRPRJHQL]DWLRQ (Fig. 7(c)). One stage was the accumulation process of temperature ranged between 132 °C and 148 °C (the WKH8SSHU3HUPLDQFDOFLXPVXOIDWHULFKIOXLGVDQGOLTXLG KRPRJHQL]DWLRQWHPSHUDWXUHSHDNUDQJHGEHWZHHQƒ& hydrocarbon fluids. Strontium, carbon, and oxygen isotopic and 145 °C (Fig. 9(h))). Temperature measurement and laser characteristics of calcite veins filling the reservoir fractures Raman spectroscopy revealed that the organic inclusions RIWKH&KDQJ[LQJDQG0DRNRXIRUPDWLRQVUHYHDOHGWKDWWKH mainly consisted of water-soluble methane (Fig. 9(i)), while fluids of calcite veins were mainly sourced from the Upper + S was contained in some inclusions. Calcite veins were Permian, and the inclusions in calcite veins mainly consisted ULFKLQZDWHUVROXEOHPHWKDQHLQFOXVLRQVEXWODFNHGOLTXLG RIJDVOLTXLGJH7KHLQFOXVLRQVÀXLGRFFXUUHGFKDUDWWKHSHDN petroleum inclusions. Thus, the charge of fluids leading to of hydrocarbon generation, and hydrocarbons were sourced WKHIRUPDWLRQRIFDOFLWHYHLQVOLNHO\RFFXUUHGDIWHUSHWUROHXP IURPWKH8SSHU3HUPLDQVRXUFHURFNV0RUHRYHUDQDO\VLVRI pyrolysis. Calcite was mainly distributed at the fracture edges, natural gas in Permian reservoirs revealed the other stage of and sparse dry bitumen was distributed in the center of the IOXLGDFFXPXODWLRQZDVPDLQO\IURP6LOXULDQVRXUFHURFNV IUDFWXUHV7KXVWKHELWXPHQLQWKHFHQWHURIIUDFWXUHVOLNHO\ DQGSDUWIURP3HUPLDQVRXUFHURFNV7KHWLPHRUGHURIWKH HQWHUHGWKHIDFWXUHVDWWKHVDPHWLPHDVWKHÀXLGVOHDGLQJWR two-stage fluid accumulation was unable to be determined WKHIRUPDWLRQRIFDOFLWH¿QDOO\VHWWOLQJLQWKHUHVLGXDOVSDFH 7KHÀXLGLQFOXVLRQVRIFDOFLWHYHLQV¿OOLQJWKHVXUURXQGLQJ 16 Pet.Sci.(2013)10:1-18 (Fig. 8(c)). VRXUFHURFNV$IDYRUDEOHVRXUFHUHVHUYRLUDVVHPEODJHZDV $QDO\VLVRIFDUERQR[\JHQDQGVWURQWLXPLVRWRSHV IRUPHGEHWZHHQ6LOXULDQVRXUFHURFNVDQG&DUERQLIHURXV RIYHLQVDQGVXUURXQGLQJURFNVLQWKH/RZHU7ULDVVLF Feixianguan Formation revealed that the original fluids ,QWKH-LDQQDQVWUXFWXUHGXULQJDQVKDQ< DQG+LPDOD\DQ OHDGLQJWRWKHIRUPDWLRQRIYHLQVZHUHPRVWOLNHO\VRXUFHG WHFWRQLVPWKHWUDSVRIYDULRXVKRUL]RQVUHPDLQHGLQWDFWDQG IURPWKH/RZHUULDVVLF7 RU8SSHU3HUPLDQ+RZHYHUWKH no long-distance cross-formational accumulation of Cambrian Lower Triassic Feixianguan had no potential for hydrocarbon IOXLGVRFFXUUHGLQWKH3HUPLDQUHVHUYRLUV$FFRUGLQJO\WKH JHQHUDWLRQLQGLFDWLQJWKDWWKHZDWHUVROXEOHPHWKDQH¿OOLQJ hydrocarbon preservation conditions were excellent, and WKHIUDFWXUHVZHUHOLNHO\VRXUFHGIURPRWKHUVWUDWDEHORZ Jiannan gas field was discovered with vertical development the Feixianguan Formation. Drilling data from the Jianghan RIJDVUHVHUYRLUVLQWKH&DUERQLIHURXV+XDQJORQJ3HUPLDQ Oilfield indicate that natural gas was discovered in both Changxing, and the Triassic Feixianguan and Jialingjiang the underlying Upper Permian and Lower Permian strata, formations. showing that the natural gas in Feixianguan gas reservoirs Through the study of organic geochemical tracers in could have the same hydrocarbon source as that of the marine strata of the three typical structures, the differences underlying Permian reservoirs. RIWKHIOXLGPRYHPHQWKDYHEHHQIXOO\UHFRJQL]HGDQGWKH On the basis of the above analysis, gas sources of the 3HUPLDQDQGULDVVLF7QDWXUDOJDVLQ-LDQQDQJDV¿HOGPDLQO\ VWUXFWXUHVKDYHDOVREHHQDQDO\]HG 7DEOH 7KHODWHU LQFOXGH3HUPLDQFDUERQDWHVRXUFHURFNVDQGFRDOPHDVXUH accumulation of the Silurian and Cambrian fluids occurred Q in the Carboniferous, Permian, and Triassic reservoirs. the case of earlier favorable preservation conditions, vertical In the case of a long-distance and large-scale cross- migration occurred in part of the natural gas generated in the formational migration occurring in deep Cambrian fluids, 6LOXULDQRXUFHVURFNVEXWGLGQRWUHDFKWKHHQWLUH)HL[LDQJXDQ ODWHUDFFXPXODWHGÀXLGVPRGL¿HGH[LVWLQJDFFXPXODWHGÀXLGV DQG-LDOLQJMLDQJIRUPDWLRQVLQWKH/RZHUULDVVLF70RVWRI resulting in the reduction of preservation conditions of earlier WKHÀXLGJHFKDURFFXUUHGRQO\LQWKHRYHUO\LQJ&DUERQLIHURXV accumulated hydrocarbons. This has created major problems +XDQJORQJ)RUPDWLRQ IRUH[SORUDWLRQLQHUPLDQ3VWUDWDLQWKH;LQFKDQJVWUXFWXUH,Q Traces of two-stage fluid migration and accumulation case of a short-distance cross-formational charge of Silurian were observed in the Jiannan gas field (Fig. 7(d)). One ÀXLGVWRWKH&DUERQLIHURXVDQG3HUPLDQUHVHUYRLUVRQO\ORFDO stage of fluid migration was the accumulation of calcium- modification occurred to the earlier closed and complete FDUERQDWHULFKÀXLGVZLWK3HUPLDQURFNVDVWKHLUVRXUFH$W preservation systems, which resulted in favorable hydrocarbon WKHVDPHWLPHDVLJQLILFDQWDPRXQWRIOLTXLGK\GURFDUERQV preservation conditions. Exploration has shown Longjuba JHQHUDWHGLQ3HUPLDQVRXUFHURFNVPLJUDWHGWRWKHULDVVLF7 is a gas-bearing structure. The Silurian and Cambrian fluid UHVHUYRLUV1RREYLRXVDFFXPXODWHGWUDFHVRIÀXLGVH[LVWHGLQ accumulation in the neighboring Carboniferous reservoirs did RWKHUKRUL]RQVZKLOHDIDYRUDEOHVRXUFHUHVHUYRLUDVVHPEODJH not reach the entire Permian reservoir; the Permian-Triassic ZDVIRUPHGDPRQJWKH3HUPLDQRXUFHVURFNVDQGWKH3HUPLDQ and the Silurian-Carboniferous source-reservoir assemblages 7KHRWKHUVWDJHRIÀXLGPLJUDWLRQZDVLDVVLFUHVHUYRLUVU7DQG were classified as two non-interfering fluid systems with shown as the accumulation of hydrocarbons into the overlying excellent hydrocarbon preservation conditions, leading to the Carboniferous reservoirs mainly generated in the Silurian H[SORUDWLRQDQGGLVFRYHU\RIWKH-LDQQDQJDV¿HOG Table 8G-LDQQDQVWUXFWXUHVDQGWKHLUH[SORUDWLRQVLWXDWLRQVIHUHQFHVRIWKHÀXLGPLJUDWLRQLQ;LQFKDQJ/RQJMXEDDQ7KHGLI The relation between the (DUO\ÀXLG /DWHÀXLG Distance between Exploration Structures Preservation hydrocarbon and the source accumulation accumulation the formation achievement 1) The Triassic residual organic matter comes from the Permian carbonate and FRDOPHDVXUHVRXUFHURFNV 2) The Permian residual organic matter Permian &DPEULDQĺ ORQJGLVWDQFH$ Overall ;LQFKDQJ is from the Permian coal-measure source None ULDVVLF7ĺ3HUPLDQ Permian cross-formational destruction URFNV 3) The Carboniferous residual organic matter is from the Silurian and &DPEULDQVRXUFHURFNV Small gas bearing 1) The Permian natural gas is from the VKRUWGLVWDQFH$ Partial Longjuba 3HUPLDQĺ3HUPLDQ 6LOXULDQĺ3HUPLDQ pools such as Longjuba 3HUPLDQDQGWKH6LOXULDQVRXUFHURFNV cross-formational destruction structure 1) The natural gas of the northern high Gas pools in the point comes from the Permian source +XDQJORQJ)RUPDWLRQRI URFNV 7KHÀXLG the Carboniferous, the 2) The Permian and the Triassic natural accumulation Cambrian, Silurian Changxing Formation of the Jiannan gas is derived from the Silurian source ULDVVLF3HUPLDQĺ7 from neighboring No destruction ĺ&DUERQLIHURXV Permian, the Feixianguan URFNV strata and Jialingjiang formations 3) The Carboniferous natural gas is from of the Triassic (Jiannan gas WKH6LOXULDQVRXUFHURFNVZLWKDVPDOO ¿HOG SDUWIURPWKH&DPEULDQVRXUFHURFNV VRXUFHURFNVLQDGGLWLRQWR6LOXULDQVRXUFHURFNV7KHUHIRUHL IRUPDWLRQHYROXWLRQPRGL¿FDWLRQDQGGHVWUXFWLRQRIGLIIHUHQW UHVHUYRLUVUHVXOWLQJLQDQDGGLWLRQDOLQGHSHQGHQWÀXLGV\VWHP Pet.Sci.(2013)10:1-18 17 reservoirs. SPE Reservoir Evaluation and Engineering. 2009. 12(1): 6 Conclusions 88-95 FOD\RUGHQ6$5:+3DUQHOO%DU-HWDO$VVHVVPHQWRIÀXLG FRQWDFWV $W OHDVWIRXUVHWVRIVRXUFHURFNVH[LVWHGLQWKHZHVWHUQ DQGFRPSDUWPHQWDOL]DWLRQLQVDQGVWRQHUHVHUYRLUVXVLQJIOXLG +XEHL±HDVWHUQ&KRQJTLQJDUHD3HUPLDQPDULQHFDUERQDWH LQFOXVLRQV$QH[DPSOHIURPWKH0DJQXV2LO)LHOG1RUWK6HD DQGFRDOPHDVXUHVRXUFHURFNVDQG6LOXULDQDQG&DPEULDQ $$3*%XOOHWLQ DUJLOODFHRXVVRXUFHURFNV7KHQDWXUDOJDVDQGWKHUHVLGXDO organic matter in the Triassic and the Permian strata showed RIJDVLQ$XVWUDOLDQ%RZHQ%DVLQFRDOV2UJDQLF*HRFKHPLVWU\ VLPLODUFKDUDFWHULVWLFVWRWKRVHRIWKH6LOXULDQVRXUFHURFNV 1998. 29(1-3): 347-362 WKH3HUPLDQPDULQHFDUERQDWHVRXUFHURFNVDQGWKHFRDO VHDZDWHUDULDWLRQRI9HWDO$+'HQLVRQ5(+HWKHULQJWRQ(:NH%XU 87 86 PHDVXUHVRXUFHURFNVZKLOHWKHQDWXUDOJDVDQGWKHUHVLGXDO Sr/ 6UWKURXJKRXW3KDQHUR]RLFWLPH*HRORJ\ organic matter in the Carboniferous reservoirs showed similar FKDUDFWHULVWLFVWRWKRVHRIWKH6LOXULDQVRXUFHURFNVZLWKD Q+'&KH3DQJ/1L;)HWDO1HZEULHIUHPDUNVRQK\GURFDUERQ VPDOOSDUWFRPLQJIURPWKH&DPEULDQVRXUFHURFNV DQJW]HSURVSHFWLQJUHRIPDULQHVWUDWDLQWKHPLGGOH<DQGXSSHU JLRQ Petroleum Geology and Experiment. 2007. 29(1): 13-18 (in Chinese) $WOHDVWWZRVWDJHVRIIOXLGDFFXPXODWLRQRFFXUUHG Q0&KH.([SORUDWLRQSRWHQWLDORIQDWXUDOJDVLQZHVWHUQ+XEH L± in Carboniferous-Triassic reservoirs in the study area. HDVWHUQ&KRQJTLQJDUHD-RXUQDORI-LDQJKDQ3HWUROHXP,QVWLWXWH Earlier marine strata above the Permian were shown with 2003. 25(1): 27-29 (in Chinese) DQDFFXPXODWLRQRIOLTXLGK\GURFDUERQVJHQHUDWLQJLQWKH -;'DL7KHLGHQWL¿FDWLRQRIDONDQHJDV6FLHQFHLQ&KLQD 6H ULHV% 3HUPLDQRXUFHVURFNVWRWKH3HUPLDQDQGWKH/RZHUULDVVLF7 1992. 2: 185-193 (in Chinese) reservoirs. This accumulation was considered as internal -;'DL1L<<DQG+XDQJ63'LVFXVVLRQRQWKHFDUERQLVRWRS LF fluid flow within the same relatively complete preservation UHYHUVDORIDONDQHJDVHVIURPWKH+XDQJORQJ)RUPDWLRQLQWKH system. The later accumulation of the Silurian and Cambrian 6LFKXDQ%DVLQ$FWD&KLQD3HWUROHL6LQLFD    LQ fluids occurred in the Carboniferous, Permian, and Triassic Chinese) reservoirs. In the case of a long-distance and large-scale 6'DL:+H=$DQGDQJ: -<7KLQNLQJRI0HVR3DOHR]RLF cross-formational migration occurring in deep Cambrian hydrocarbon exploration in South China. Oil and Gas Geology. 2001. 22(3): 195-202 (in Chinese) ÀXLGVODWHUDFFXPXODWHGÀXLGVPRGL¿HGH[LVWLQJDFFXPXODWHG LVRQ5HQ'(.RHSQLFN5%%XUNH:+HWDO&RQVWUXFWLRQRIWKH fluids, resulting in destruction of preservation conditions 87 86 0LVVLVVLSSLDQ3HQQV\OYDQLDQDQG3HUPLDQVHDZDWHU Sr/ Sr curve. of earlier accumulated hydrocarbons. In case of a short- Chemical Geology. 1994. 112(1-2): 145-167 distance cross-formational charge of Silurian fluids to the ODQG(JQ:$DQG0DFNHQ]LH$66RPHDVSHFWVRIWKHRUJDQLF geochemistry of petroleum fluids. Geologische Rundschau. 1989. occurred to the earlier closed and complete preservation 78(1): 291-303 systems. The Silurian and Cambrian fluid accumulation in ODQG:$(QJ0DFNHQ]LH$60DQQ'0HWDO7KHPRYHPHQWDQG the neighboring Carboniferous reservoirs did not reach the entrapment of petroleum fluids in the subsurface. Journal of the entire Permian reservoir; and the Permian-Triassic and the Geological Society. 1987. 144(2): 327-347 Silurian-Carboniferous source-reservoir assemblages were ODQG:$0XJJHULGJH$(QJ+ Clifford3-HWDO0RGHOOLQJGHQVLW\ FODVVL¿HGDVWZRQRQLQWHUIHULQJÀXLGV\VWHPVLWKZH[FHOOHQW driven mixing rates in petroleum reservoirs on geological time- scales, with application to the detection of barriers in the Forties hydrocarbon preservation conditions. Field (UKCS) (in the Geochemistry of Reservoirs). Geological 3) On the basis of studies of fluid migration paths in Society Special Publications. 1995. 86: 185-201 (in Chinese) marine strata and comparative analysis of the exploration Fu Z R, Li Z J and Zheng D Y. Structural pattern and tectonic evolution results, it was shown that intense late tectonism causing RI11(WUHQGLQJVWULNHVOLSRURJHQLFEHOWLQWKHERUGHUUHJLRQRI long-distance and large-scale cross-formational migration RIGHHS/RZHU3DOHR]RLFIOXLGVZDVFULWLFDOWRK\GURFDUERQ 272 (in Chinese) SUHVHUYDWLRQFRQGLWLRQVLQ8SSHU3DOHR]RLFDQG0HVR]RLF Gal imov (03URNKRURY V S, Fedoseyev'9HWDO+HWHURJHQHRXV PDULQHVWUDWD$FFRUGLQJO\WKH]RQHVZLWKOHVVVHYHUHODWH carbon isotope effects in synthesis of diamond and graphite from gas. WHFWRQLVPLQWKHZHVWHUQ+XEHL±HDVWHUQ&KRQJTLQJDUHDZLWK Geochemistry International. 1973. 10(2): 306-312 no superimposition or modification of Upper and Lower /$QDO\VLV*DR RQSURVSHFWVLQZHVWHUQ+XEHL±HDVWHUQ&KRQJTLQJ 3DOHR]RLFIOXLGVDQGDQ8SSHU3DOHR]RLF]RQHZLWKIOXLG region. Southern China Oil & Gas. 2004. 17(2): 49-52 (in Chinese) =&KHQ)0*XR.)X<;HWDO1DWXUDOJDVUHVHUYRLULQJFRQ GLWLRQV RI6LQLDQDQG&DPEULDQIURPZHVWHUQ+XEHLWRHDVWHUQ&KRQJTLQJ areas for future hydrocarbon exploration. areas. Journal of Southwest Petroleum University (Science & Technology Edition). 2008. 30(4): 39-42 (in Chinese) Acknowledgements )DR+/L67*RQJ=6HWDO7KHUPDOUHJLPHLQWHUUHVHUYRLU 7KLVZRUNZDVVSRQVRUHGE\1DWLRQDO3URJUDPVIRU compositional heterogeneities, and reservoir-filling history of the Dongfang Gas Field, Yinggehai Basin, South China Sea: Evidence Fundamental Research and Development (973 Program, $$3*%XOOHWLQIRUHSLVRGLFÀXLGLQMHFWLRQVLQRYHUSUHVVXUHGEDVLQV 2012CB214805), and the National Natural Science 2000. 84(5): 607-626 Foundation (40930424). 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Palaeogeography, Palaeoclimatology, Palaeoecology. natural gas in the great-medium coal-formed gas fields of China. 2005a. 224(4): 333-351 Experimental Petroleum Geology. 2000. 22(1): 16-21 (in Chinese) 13 18 Kor te C.R]XU+:DQGHL]HU9-į &DQGį O values of Triassic .(YDOXDWLRQRIDVLPSOHPRGHORIYLWULQLWH$HQH\--DQG%XUQKDP6ZH EUDFKLRSRGVDQGFDUERQDWHURFNVDVSUR[LHVIRUFRHYDOVHDZDWHU UHIOHFWDQFHEDVHGRQFKHPLFDONLQHWLFV$$3*%XOOHWLQ and palaeotemperature. Palaeogeography, Palaeoclimatology, 74(10): 1559-1570 Palaeoecology. 2005b. 226(3-4): 287-306Ung erer36WDWHRIWKHDUWRIUHVHDUFKLQNLQHWLFPRGHOLQJRIRLO KHWDOWURQWLXPLVRWRSH6HYRO%UXFNVFKHQ3WH&:.R]XU+RU XWLRQRI formation and expulsion. Organic Geochemistry. 1990. 16(1-3): Late Permian and Triassic seawater. Geochimica et Cosmochimica 1-25 87 86 13 18 $FWD   ]HU-HL$OD9'$]P\.HWDO Sr/ 6Uį &DQGį O evolution of QJ'/LD*=KDQJ6&=KDR0-HWDO7KHK\GURFDUERQIRU PDWLRQ   &KHPLFDO*HRORJ\3KDQHUR]RLFVHDZDWHU period in Kuche Depression. Chinese Science Bulletin. 2002. 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Petroleum Science – Springer Journals

Published: Feb 7, 2013

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