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Geochemical studies of the Silurian oil reservoir in the Well Shun-9 prospect area, Tarim Basin, NW China

Geochemical studies of the Silurian oil reservoir in the Well Shun-9 prospect area, Tarim Basin,... 432 Pet.Sci.(2013)10:432-441 DOI 10.1007/s12182-013-0293-2 Geochemical studies of the Silurian oil reservoir in the Well Shun-9 prospect area, Tarim Basin, NW China Song Daofu, Li Meijun and Wang T.–G 6WDWH.H\/DERUDWRU\RI3HWUROHXP5HVRXUFHVDQG3URVSHFWLQJ&KLQD8QLYHUVLW\RI3HWUROHXP%HLMLQJ&KLQD © China University of Petroleum (Beijing) and Springer-Verlag Berlin Heidelberg 2013 Abstract: &RPPHUFLDORLOÀRZKDVEHHQREWDLQHGIURPWKHVDQGVWRQHUHVHUYRLURIWKH/RZHU6LOXULDQ Kelpintag Formation in the Well Shun-9 prospect area. In the present studies, 10 Silurian oil and oil sand samples from six wells in the area were analyzed for their molecular and carbon isotopic compositions, oil DOWHUDWLRQ ELRGHJUDGDWLRQ RLOíVRXUFHURFNFRUUHODWLRQDQGRL oils and oil sands are characterized by low Pr/Ph and C /C tricyclic terpane (<1.0) ratios, “V”-pattern 21 23 C -C steranes distribution, low C VWHUDQHDQGWULDURPDWLFGLQRVWHUDQHDEXQGDQFHVDQGOLJKWį C 27 29 28 values, which can be correlated well with the carbonate source rock of the O l/LDQJOLWDJH)RUPDWLRQ IHUHQWRLOELRGHJUDGDWLRQ'LILWKOHYHOVKDYHDOVREHHQFRQ¿UPHGIHUHQWIRURLOVRLO:WKHVDQGVGLILQWHUYDOV 2 1 the S k seal, oils and oil sands from the S k interval of the Kelpintag Formation have only suffered light 1 1 3-1 ELRGHJUDGDWLRQDVFRQ¿UPHGE\WKHSUHVHQFHRI³8&0´DQGDEVHQFHRIQRUKRSDQHVZKHUHDVWKH6 k RLOVDQGVZHUHKHDYLO\ELRGHJUDGHG SURYHGE\WKHSUHVHQFHRIQRUKRSDQHV GXHWRWKHODFNRIWKH6 k VHDOZKLFKVXJJHVWVDVLJQL¿FDQWUROHRIWKH6 k seal in the protection of the Silurian oil reservoir. Based RQV7P V 7WKHDQG70'%7UDWLRVDVUHVHUYRLU¿OOLQJWUDFHUVDJHQHUDORLO¿OOLQJGLUHFWLRQIURP NW to SE has been also estimated for the Silurian oil reservoir in the Well Shun-9 prospect area. Key words:HOORLOíVRXUFH6KXQURFNSURVSHFWFRUUHODWLRQDUHD\JHRFKHPLVWU:6LOXULDQRLOUHVHUYRLU DOWHUDWLRQRLOUHVHUYRLU¿OLQJGLUHFWLRQ FRPSRVLWLRQV$OWHUDWLRQ ELRGHJUDGDWLRQ RLOíVRXUFHURFN 1 Introduction FRUUHODWLRQDQGRLO¿OOLQJRULHQWDWLRQZHUHGHGXFHGIURPWKH The Well Shun-9 prospect area is located at the south of results. WKH6KXQWXRJXROHDULP/RZ$IWHU%DVLQJRLQJ8SOLIWXQGHU7 several years exploration and after sand fracturing operations, 2 Geological setting FRPPHUFLDORLOÀRZVKDYHEHHQREWDLQHGIURPWKHVDQGVWRQH 7KH6KXQWXRJXROH/RZ8SOLIWLVLQIDFWVWLOODQHJDWLYH structure, being a relative uplift within a huge depression Shun-9, -901, -902H in the area in the last two years. zone. The depression zone is composed of the Manjiaer and Silurian sandstones are widely distributed in the ZDWL$'HSUHVVLRQVDVZHOODVWKH6KXQWXRJXROH/RZ8SOLIW 6KXQWXRJXROH/RZ8SOLIWDQGLWVDGMDFHQWUHJLRQV$VHDUO\ LQEHWZHHQ7KH6KXQWXRJXROH/RZ8SOLIWLVDOVRORFDWHG as 1994, Silurian commercial oil was discovered in Well TZ- between the Tabei Uplift on the north and the Tazhong Uplift 11, in the Tazhong Uplift on the south of the Shuntuoguole on the south (Fig. 1). /RZ8SOLIW =KDLDQGDQJ: 6LQFHWKHQWKH6LOXULDQ 7KH6KXQWXRJXROH/RZ8SOLIWRFFXUUHGGXULQJHDUO\ interval became one of the most important exploration targets Paleozoic time and subsequently underwent multi-stage =KDQJHWDO-LDHWDO $VWKHILUVWGLVFRYHUHG tectonic transformation. Compared with surrounding uplifts 6LOXULDQRLOUHVHUYRLULQ6KXQWXRJXROH/RZ8SOLIWVWXGLHVRQ and depressions, however, the geological setting of the LWDUHVLJQL¿FDQWIRURLOH[SORUDWLRQLQWKHDUHD 6KXQWXRJXROH/RZ8SOLIWLVPRUHVWDEOHWHFWRQLFDOO\DQG In the present study, three oil and seven oil sand samples more favorable for crude oil preservation (Xiong et al, 2013). from the Silurian oil reservoir were collected from six 5HJLRQDOO\WKH/RZHU0LGGOH6LOXULDQVWUDWDDUHZLGH exploration wells (sampling well location see Fig. 1) and spread and comprised of the S k Kelpintag, S t Tataertag 1 1 analyzed in the laboratory for oil molecular and isotopic and S yLPXJDQWDZX<)RUPDWLRQVLQWKH6KXQWXRJXROH/RZ 8SOLIW =KXHWDO-LDHWDO)LJ$V DSULQFLSDO *Corresponding author. email: wwttgg@aliyun.com reservoir interval, the S k Kelpintag Formation can be divided Received August 8, 2013 UHVHUYRLUVRIWKH/RZHU6LOXULDQ.HOSLQWDJ)RUPDWLRQDWHOOV 6LOXULDQWKHGLUHFWLRQ$OO¿OOLQJUHVHUYRLUO Belt No.1 Fault Tazhong Tazhong Uplift Kunlun Mountains S k pinchout boundary Pet.Sci.(2013)10:432-441 433 1 2 3-1 LQWRWKUHHPHPEHUVWKH6 k lower sandstone, S k middle the S k lower sandstone section (Ma et al, 2012). 1 1 1 3 3 1 mudstone and S k upper sandstone members, while the S k The overlying S t lower red mudstone member of the 1 1 1 upper member also can be subdivided into three sections, Tataertag Formation, S k middle mudstone member and 3-1 3-2 3-3 3-2 i.e., S k lower sandstone, S k middle mudstone and S k S k middle mudstone section of the Kelpintag Formation 1 1 1 1 upper sandstone sections (Fig. 2). So far, however, the major constitute three sets of effective regional seals for Silurian oil Silurian reservoirs for movable oil production are only UHVHUYRLUVZLWKLQWKH6KXQWXRJXROH/RZ8SOLIW 4XDQHWDO discovered within the S k lower sandstone member and also -LDQJHWDO)LJ Legend Tabei Uplift Town YM206 Well location MN1 YJ1X Tectonic units YJ2X HD2 border Major fault YN1 Minor fault S8 HD5 Alaer Shuntuoguole Low Uplift AM1 YN2 Awati Well Shun-9 prospect area Depression Mc1 AM2 S9 S903H Manjiaer Sx2 S905H Ad1 S904H S902H Mx2 Depression S901 SX1 S1 S7 S5 TZ45 Tianshan Mountains SN3 TZ32 TZ31 TZ54 Tarim Basin TZ12 SN1 TZ19 SN2 Guchengxu Uplift Fig. 1*HRORJLFDOPDSRIWKH6KXQWXRJXROH/RZ8SOLIW 7KHVWDEOHFDUERQLVRWRSLFFRPSRVLWLRQV į C) of oils/ 3 Experimental extracts and their fractions were analyzed on a Thermoscience Oil sands were Soxhlet-extracted with chloroform 70RGHO,5060$7KHRLOVH[WUDFWVDQGWKHLUIUDFWLRQV (CHCl ). The oil sand/source rock extracts and oils were were burned to produce individual CO peaks on a Flash HT o 13 deasphalted using n-hexane, and then fractionated using copper oxide reaction furnace at 980 &7KHLUį C values column chromatography (silica gel vs. alumina 3:1) into ZHUHPHDVXUHGE\LQWHJUDWLRQRIWKHPDVVHVDQGLRQ saturate, aromatic and NSO fractions by sequential elution current counts of CO peaks. A CO reference gas with known 2 2 13 13 with n-hexane, toluene and chloroform. į C C PDB Gas chromatography (GC) of the saturate fractions was values of the oils/extracts and their fractions were reported performed using an Agilent Model 6890 gas chromatograph LQWKHįQRWDWLRQUHODWLYHWRWKHUHIHUHQFHJDV7KHDYHUDJH HTXLSSHGZLWKDIXVHGVLOLFDFROXPQ +3PîPP values of at least two runs for each sample were reported and i.d.). The oven temperature program was from 100 C (1 min) only results with a standard deviation of less than 0.3‰ were o o to 300 C (held 10 min) at 4 C/min. Helium was used as used. carrier gas. GC–mass spectrometry (GC–MS) analysis of saturated 4 Results and discussion and aromatic fractions were conducted using an Agilent 0RGHOJDVFKURPDWRJUDSKILWWHGZLWKD'%06 4.1 Oil physical properties and gross composition capillary. The GC temperature operating conditions for the o o o The Silurian oil reservoir in the Well Shun-9 prospect saturated fraction were: 100 C (1 min) to 220 C at 4 C/ o o area has a regular variation in oil physical properties and min and, then to 300 & KHOGPLQ DW &PLQIRUWKH o o gross composition as follows. From Well Shun-9, via Well aromatic fraction were: 80 C (1 min) to 300 & KHOGPLQ Shun-901, to Well Shun-902H, the oil density, viscosity, at 3 C/min. Saturated and aromatic hydrocarbon biomarker sulfur content as well as aromatic and asphaltene contents parameters were calculated from integrated peak areas on the are gradually increasing, whereas their saturate contents and mass chromatograms. YDOXHZDVSXOVHGLQWRWKHPDVVVSHFWURPHWHU7KHį 434 Pet.Sci.(2013)10:432-441 Petroleum Depth PGHHS DSSHDUORZHUVDWXUDWHFRQWHQW Series Formation Member Section Lithology system and saturates to aromatics ratio (1.1-1.9) as well as higher DVSKDOWHQHFRQWHQW  2QWKHFRQWUDU\WKH 1 deeper S k ORZHUVDQGVWRQHPHPEHURLOVDQGV DURXQG S t 1 Tataertage and saturates to aromatics ratio (2.2-3.0) as well as lower DEOH 7DVSKDOWHQHFRQWHQWV 4.2 Hydrocarbon composition 3-3 S k 4.2.1 Acyclics The n-alkane series of the Silurian oils in the S k lower sandstone member reservoir occur with a unimodal distribution pattern, with maximum carbon number at nC or 3-2 S k 1 nC and an nC -/nC + ratio of 1.71-3.23, suggesting a high 21 22 maturity level. In addition, all their GC traces have a baseline S k “hump” resulting from unresolved complex mixture (UCM) in the oil, but only the heavy oil of Well Shun-902H shows a more obvious UCM “hump”, indicating the disparity of the biodegradation effect (Fig. 3(a)-(c)). Lower As for the oil sand extracts in the deeper S k lower Silurian sandstone member reservoir, their n-alkane series almost have 3-1 S k a similar unimodal distribution pattern with the oils, with an Kelpintag average nC -/nC + ratio of 1.72, while the maximum carbon 21 22 number has been transferred to nC or nC , showing an 17 19 adsorption effect of reservoir rock (Fig. 3(d)-(f), Table 2). In the oil sand extracts for the reservoir rocks of 3-1 the shallower S k sandstone section, however, most n-alkanes have been moved out and all their GC traces 2 show a predominant UCM “hump” as expected for severely S k ELRGHJUDGHGRLOV &RQQDQ)LJ J  K Besides n-alkanes, pristine (Pr) and phytane (Ph) are also detected in both oils and oil sand extracts in the Well Shun-9 prospect area (Fig. 3), all of which show an equal S k abundance tendency with the Pr/Ph ratio ranging from 0.84 to 0.98 (Table 2), revealing similar sedimentary and diagenesis environments of the oil source bed. Moreover, as shown in Fig. 4, the Pr/Ph ratios of our analyzed samples fall into the ratio range of Tahe oils, which are derived from Upper Sandstone Siltstone Argillaceous Silty Mudstone Seal Reservoir Ordovician source rocks (Wang et al, 2006). siltstone mudstone 4.2.2 Terpanoids *HQHUDOL]HG/RZHU6LOXULDQVWUDWLJUDSK\ Fig. 2 As predominant terpanoid components of the Silurian LQWKH6KXQWXRJXROH/RZ8SOLIW oils and oil sands in the well Shun-9 prospect area, tricyclic saturates to aromatics ratios seem to be decreasing, so that terpane series have a much higher abundance than the the reservoir oils vary from regular black oil in Wells Shun- pentacyclic hopane series, with the tricyclics to hopanes 9 and Shun-901 to heavy oil in Well Shun-902H. Moreover, UDWLRV 77+ IURPDEOH 7 ,QWULF\FOLFVWKH& the wax content also shows a wide range in different samples, tricyclic terpane is predominant over C tricyclic terpane, varying from 3.0% to 16.1% (Table 1). The gradual variations resulting in C /C tricyclic terpane ratio <1.0 (C /C TT, 21 23 21 23 in oil physical properties and gross compositions support an DEOH7 )LJ ZKLFKFDQEHZHOOFRUUHODWHGZLWKWKH increased biodegradation degree from the oil in Well Shun-9, previously analyzed oil source rock of the O l/LDQJOLWDJH via Well Shun-901, to Well Shun-902H. Formation instead of the Cambrian source rock in the Tarim As a whole, all the gross compositions of oil sands show %DVLQ )LJ L  M relatively low saturate contents as well as high aromatic, C to C (no C ) hopane series and gammacerane are 27  28 NSO-compound and asphaltene contents owing to the detected, showing a regular distribution pattern and low adsorptive effect in the sandstone reservoir (Table 1). gammacerane/C hopane ratio 0.19 in average, in the Silurian Due to the disparity in total seal thickness and secondary RLOVDQGRLOVDQGV )LJ alteration (biodegradation), the gross composition of oil A distinct feature between the samples from different sands from different intervals is also varied. Oil sands in LQWHUYDOVLVWKHUHODWLYHDEXQGDQFHRIQRUKRSDQHV 3-1 the shallower S k ORZHUVDQGVWRQHVHFWLRQ DERXW QRUKRSDQHVDUHDEVHQWLQWKHRLOVDQGRLOVDQGVIURPWKH PLQGHSWK KDYHKLJKHUVDWXUDWHFRQWHQW   Pet.Sci.(2013)10:432-441 Table 1 Basic geochemical data for the Silurian oils and oil sands in the Well Shun-9 prospect area Physical properties Gross composition ,VRWRSLFFRPSRVLWLRQį C, ‰ PDB Depth Mem./ No. Well Sample Density Viscosity Sulfur Wax Sat Aro NSO Asp Oil/ m Sect. Sat/Aro Sat Aro NSO Asp g/cm mPa s % % % % % % Extract 1 Shun-9  0.868  0.46 16.1 76.3  4.9 2.9 4.8 -32.3 -32.3 -31.8 -31.9 -32.1 Regular oil 2 Shun-901  0.876 22.8 0.46 2.98 67.2 18.6 6.8 7.4 3.6 -31.9 -31.9 -31.8  -32.1 S k Heavy 3 Shun-902H   871.9    24.6 3.0 17.4 2.2 -31.6  -31.8 -31.3 -32.2 oil 4 Shun-1  -- -- -- -- 28.6 24.8 14.3 32.3 1.1 -31.8 -31.7 -31.8 -32.0 -32.3 3-1 S k Shun-902H  -- -- -- -- 31.8  6.0  1.9 -32.2 -32.2 -32.2 -32.1 -32.9 Oil 6 Shun-901  -- -- -- --   9.1 7.9 2.2 -31.7 -32.2 -31.9 -31.4 -31.2 sand 7 Shun-902H  S k -- -- -- --  23.0 11.1 11.1 2.4 -32.1 -31.3 -32.2 -32.2 -32.6 8 Shun-904H  -- -- -- -- 62.6 21.0 9.9  3.0 -31.7  -31.3 -31.4 -31.8 $VSDVSKDOWHQHIUDFWLRQ$URDURPDWLFIUDFWLRQ162162FRPSRXQGIUDFWLRQ1RWHV6DWVDWXUDWHGIUDFWLRQ nC nC 14 (a) (b) 1 1 Shun-9, S k , 5560-5589 m, regular oil Shun-901, S k , 5496-5504 m, regular oil 1 1 Pr Ph Pr Ph UCM UCM nC (c) nC (d) 15 17 Shun-902H, S k , 5513-5530 m, heavy oil 1 Shun-901, S k , 5500 m, oil sand Ph Pr Ph Pr UCM UCM nC nC 17 19 (f) (e) Ph 1 1 Pr Shun-902H, S k , 5517 m, oil sand Shun-904H, S k , 5568 m, oil sand 1 1 Ph Pr UCM UCM (g) (h) 3-1 3-1 Shun-1, S k , 5316 m, oil sand Shun-902H, S k , 5303 m, oil sand 1 1 Fig. 3 Gas chromatograms of saturated hydrocarbon fraction SULVWDQH3KSK\WDQH1RWHV3U nCQRUPDODONDQHV iPROHFXODUFDUERQQXPEHU8&0XQUHVROYHGFRPSOH[PL[WXUH LQWHUQDOVWDQGDUG S k member, while they are abundant in the oil sands from the C QRUKRSDQHDQG& ELVQRUKRSDQHDUHWKH 1 29 28 3-1 S k interval, with the ratio of C QRUKRSDQH& -hopane GRPLQDQWGHPHWK\ODWHGFRPSRXQGLQWKHRLOVDQGVIURP 1 29 30 3-1 from 0.36 to 0.41. As shown in m/z 177 mass chromatograms, the S k LQWHUYDOEXWDZKROHGLVWULEXWLRQRIQRUKRSDQHV 1 436 Pet.Sci.(2013)10:432-441 Table 2 Basic geochemical parameters for the Silurian oils and oil sands in the Well Shun-9 prospect area Acyclic alkanes Terpanoids Steroids Polyaromatic hydrocarbons Depth Mem./ Regular C  (C +C )P/ 29 21 22 No. Well Sample '%))/'%7 nC -/ Pr/ Ph/ C /C Ts/ TT/ G/ 4-/1- 21 21 23 m Sect. steranes, % Pr/Ph NH/ Dia/RS (C -C ) 27 29 nC + nC nC TT (Ts+Tm) H C H MDBT 22 17 18 30 C C C )/ DBT DBF C H RS 30 27 28 29 1 Shun-9   0.84 0.3 0.43 0.43  1.84  -- 0.34 0.2 0.46 0.28 0.2 16.6 20.7 62.7 6.99 Regular oil 2 Shun-901  3.23   0.63  0.46   -- 0.47 0.2 0.33 0.28 0.34  24.7 18.0 S k Heavy 3 Shun-902H  1.71 0.92 0.44   0.44 2.86 0.18 -- 0.36 0.2 0.44 0.34 0.3 64.9 21.7 13.4 3.08 oil 4 Shun-1  1.48  0.69 1.01   1.84 0.16 0.41 0.2 0.41 0.39  0.21 77.3 13.9 8.80 -- 3-1 S k Shun-902H  2.34 0.86  0.86  0.37  0.17 0.36 0.39 0.19 0.43 0.24 0.31  4.30 4.20 -- Oil 6 Shun-901  1.86 0.94   0.48   0.29 -- 0.31 0.23 0.46 0.22 0.19 92.1 4.66 3.24 -- sand 7 Shun-902H  S k 1.38 0.98 0.44  0.49 0.38 2.62  -- 0.43 0.21 0.36 0.27 0.22 87.8 7.10  -- 8 Shun-904H  1.39 0.91 1.07 1.12 0.49 0.46 2.68 0.12 --  0.21 0.44 0.3 0.32 74.2 17.2 8.60 -- Notes: nC -/nC +, C -n-alkanes/C +nDONDQHV3U3KSULVWDQHSK\WDQH3U nC , pristane/C nDONDQH3K nC , phytane/C nDONDQH& /C 21 21 21 21 17 17 18 18 21 23 TT, C tricyclic terpane/C WULF\FOLFWHUSDQHV7P V 7&7 18Į (H)-trisnor-neohopane/C [18Į (H)-trisnor-neohopane+17Į + WULVQRUKRSDQH@ 21 23 27 27 77+WULF\FOLFWHUSDQHVKRSDQHV*& H, gammacerane/C KRSDQH& 1+& H, C QRUKRSDQH& KRSDQH'LD56GLDVWHUDQHVUHJXODU 30 30 29 30 29 30 VWHUDQHV & +C )P/(C -C )RS, C +C pregnanes/C -C UHJXODUGLEHQ]RIXUDQVWHUDQHV0'%7GLEHQ]RWKLRSKHQH)/'%)ÀXRUHQH'%7 21 22 27 29 21 22 27 29 4-/1-methyldibenzothiophene -0U 025 C VWHUDQHVZRXOGEHOHVVWKDQLQUHODWLYHDEXQGDQFH Oils /oil s ands fr om s tudy ar ea and diasterane has a relatively high abundance (Fig. 7). The 2.0 Oils fr om Tahe field characteristics of “V” pattern C -C steranes distributions 27 29 and low relative abundance of C 5VWHUDQH  DUH correlated well with the previously analyzed O l/LDQJOLWDJH Formation source rocks and are markedly different from the 1.3 Cambrian source rocks (Fig. 7(i), (j)). Furthermore, as shown in Fig. 8, all the Silurian oils and 1.0 oil sands fall into a tight cluster and have a similar C -C 27 29 regular steranes distribution to the Ordovician source rocks previously analyzed. 0.5 0.5 4.2.4 Triaromatic steroids 7KHP]PDVVFKURPDWRJUDPVRIDURPDWLF hydrocarbon fractions are shown in Fig. 9, exhibiting the 03 . 04 . 05 . -0. 3 -0. 2 -0.1 0 01 . 0.2 distribution of triaromatic dinosteranes and triaromatic steroids. In all the Silurian oils and oil sands, methyl- Pr/nC -Ph/nC 17 18 triaromatic steroids are only present in low concentration, Plot of Pr/Ph ratios vs. (Pr/nC -Ph/nC ) values Fig. 4 17 18 especially triaromatic dinosteroids are absent or only present 1RWHV3USULVWDQH3KSK\WDQH nCQRUPDODONDQHV i, molecular in trace amount, which can also be well correlated with the carbon number previously analyzed O l/LDQJOLWDJH)RUPDWLRQVRXUFHURFNV and apparently different from the Cambrian source rocks paralleling the 17Į(H), 21ȕ(H)-hopanes (from C up to C ) 29 33 in which the triaromatic steroids are abundant especially LVSUHVHQWLQORZFRQFHQWUDWLRQ )LJ 1RUKRSDQHVDUH triaromatic dinosteranes (Fig. 9(i), (j)). produced when all straight-chain and isoprenoid alkanes, and 4.2.5 Polyaromatic hydrocarbons most of the bicyclic alkanes have already been removed (Philp Various polyaromatic hydrocarbons have been HWDO VRWKH\DUHWDNHQDVHYLGHQFHRIH[WHQVLYH detected, especially the fluorenes, dibenzothiophenes, and bacterial activity. GLEHQ]RIXUDQV)OXRUHQH )/ GLEHQ]RWKLRSKHQH '%7 DQG 4.2.3 Steroids dibenzofuran (DBF) share a similar molecular structure, Usually steroids consist of C -C regular sterane series 27 29 so they are considered to have originated from the same and C -C pregnanes. In the Silurian oils and oil sands, 21 22 precursor and their relative compositions can indicate the the steroids show a relatively high abundance of C -C 21 22 SULPDU\VHGLPHQWDU\HQYLURQPHQW +XDQJ/LQHWDO pregnanes in comparison with C -C regular steranes, and 27 29 1987). Abundant benzothiophenes in oils have been proposed the C -C pregnanes to C -C steranes ratio [(C +C )P/ 21 22 27 29 21 22 to indicate an anoxic sedimentary environment, whereas, (C -C )Rs] ranges from 0.19 to 0.34 with 0.27 in average. 27 29 dominant dibenzofuran represents an oxidative environment Moreover, the distribution of C -C regular steranes 27 29 (Hughes, 1984). abundance appears a C >C <C “V” pattern, in which the 27 28 29 As shown in Fig. 10, all the analyzed samples, except Pr/Ph Pet.Sci.(2013)10:432-441 437 (a) C TT (b) C TT 1 1 Shun-901, S k , 5496-5504 m, regular oil Shun-9, S k , 5560-5589 m, regular oil C /C TT=0.55 C /C TT=0.43 21 23 21 23 C H C TT C TT 21 C H C H C H C H (c) (d) Shun-902H, S k , 5513-5530 m, heavy oil Shun-901, S k ,5500 m, oil sand 1 1 C /C TT=0.50 C /C TT=0.48 21 23 21 23 (e) (f) Shun-902H, S k , 5517 m, oil sand 1 Shun-904H, S k , 5568 m, oil sand C /C TT=0.49 C /C TT=0.49 21 23 21 23 (g) (h) 3-1 3-1 Shun-1, S k , 5316 m, oil sand Shun-902H, S k , 5503 m, oil sand C /C TT=0.51 C /C TT=0.58 21 23 21 23 (j) (i) Lunnan-46, 5 l, 6164 m, grey limestone 3 He-4,ɚ , 4598-4599 m, grey marl C /C TT=0.51 21 23 C /C TT=1.66 21 23 m/z 191 mass chromatograms of saturated hydrocarbon fraction, showing the distribution of tricyclic terpane Fig. 5 series and hopane series WULF\FOLFWHUSDQH+KRSDQH&771RWHV PROHFXODUFDUERQQXPEHU**DPPDFHUDQH C DNH C DNH 28 3-1 Shun-902H, S k , 5303 m, oil sand 3-1 1 Shun-1, S k , 5316 m, oil sand C NH 29 C NH C NH C NH C NH C NH 33 Fig. 6P]PDVVFKURPDWRJUDPVRIVDWXUDWHGK\GURFDUERQIUDFWLRQVKRZLQJWKHKRPRORJRXVVHULHVRIQRUKRSDQHV 1RWHV'1+ELVQRUKRSDQH1+QRUKRSDQH& : molecular carbon number i 438 Pet.Sci.(2013)10:432-441 1 (a) 1 (b) Shun-9, S k , 5560-5589 m, regular oil Shun-901, S k , 5496-5504 m, regular oil 1 1 C RS C P C %=19.9% C %=20.1% 28 28 C RS C P Dia C RS C RS C RS Dia C P C RS C P 1 (c) 1 (d) Shun-902H, S k , 5513-5530 m, heavy oil Shun-901, S k , 5500 m, oil sand 1 1 C %=20.4% C %=23.0% 28 28 1 (e) 1 (f) Shun-902H, S k , 5517 m, oil sand Shun-904H, S k , 5568 m, oil sand 1 1 C %=20.9% C %=20.9% 28 28 3-1 (g) 3-1 (h) Shun-1, S k , 5316 m, oil sand Shun-902H, S k , 5303 m, oil sand 1 1 C %=20.0% C %=18.9% 28 28 Lunnan-46, O l, 6164 m, grey limestone (i) He-4,ɚ , 4598-4599 m, grey marl (j) C %=20.5% C %=35.0% 28 28 Fig. 7 m/z 217 mass chromatograms of saturated hydrocarbon fraction, showing the distribution of sterane series SUHJQDQH'LDGLDVWHUDQH5VUHJXODUVWHUDQH&1RWHV3 , molecular carbon number C%C % 28 28 (a) (b) Crude oils Oil sands 25 75 25 75 50 50 50 50 75 25 75 25 20 50 75 20 50 75 C%C C%C % % 27 29 27 29 Fig. 8 Ternary plots showing the relative content of C -C regular steranes 27 29 DULP%DVLQ7HOO6KXQSURVSHFWDUHD E SUHYLRXVO\DQDO\]HGRLOVRXUFHURFNVLQWKH: D 6LOXULDQRLOVDQGRLOVDQGVIURPWKH Pet.Sci.(2013)10:432-441 439 1 1 Shun-9, S k , 5560-5589 m, regular oil (a) Shun-901, S k , 5496-5504 m, regular oil (b) 1 1 9 9 7,8 7,8 9 4,6 4,6 6 3 6 1 1 Shun-902H, S k , 5513-5530 m, heavy oil (c) Shun-901, S k , 5500 m, oil sand (d) 1 1 7,8 4,6 9 7,8 7 4,6 6 6 8 8 1 1 Shun-902H, S k , 5517 m, oil sand (e) Shun-904H, S k , 5568 m, oil sand (f) 1 1 4,6 7,8 4,6 7,8 7 6 6 3 8 8 3 8 3-1 3-1 Shun-1, S k , 5316 m, oil sand (g) Shun-902H, S k , 5503 m, oil sand (h) 1 1 6 7,8 7,8 4,6 4 4,6 8 3 Tazhong-30, O l, 4918 m, grey marl (i) (j) Tadong-2,ɨ , 4918 m, grey-dark mudstone 4,6 7,8 4,6 6 6 7,8 8 3 Fig. 9 P]PDVVFKURPDWRJUDPVRIDURPDWLFK\GURFDUERQIUDFWLRQVKRZLQJWKHGLVWULEXWLRQRIWULDURPDWLFVWHURLGV 1RWHV WULDURPDWLFGLQRVWHURLGVPHWK\OHW\OWULDURPDWLFVWHURLGVĮPHWK\OHWK\OWULDURPDWLFVWHURLGVPHWK\O 24-ethyl-triaromatic steroids the oil from S9 well, are characterized by dominant GLEHQ]RIXUDQDFFRXQWHGIRU!RIWRWDO)/DQG'%7'%) GLEHQ]RWKLRSKHQH DFFRXQWLQJIRURIWRWDO The reason was probably due to contamination by chemical )/'%7DQG'%)DEOH7 LQGLFDWLQJDVWURQJO\DQR[LF additives added in Well Shun-9 during oil test operation, PDULQHHQYLURQPHQW$QDEQRUPDOLW\RIWKH)/'%7'%) especially asphaltene dispersants with dominant dibenzofuran composition occurred in the oil from Well Shun-9, in which (Fig. 10). 440 Pet.Sci.(2013)10:432-441 4.3 Stable carbon isotopic composition DBT, % 7KHį C compositions of oils or extracts can help to Crude oils Oil sands determine oil–oil and oil–source rock relationships (Sofer, 20 80 *DOLPRY 7KHį C values for the Silurian oils and oil sand extracts range from -31.6‰ to -32.3‰ (Table 1) and differ by less than 1‰, suggesting that they may have 40 60 WKHVDPHJHQHWLFRULJLQ7KHDYHUDJHį C value for saturate, aromatic, resin and asphaltene fractions is -31.8‰, -31.9‰, 60 40 -31.8‰ and -32.2‰, respectively (Fig. 11). All the Silurian oils/extracts and their fractions are characterized by relative light carbon isotopic composition, which corresponds well 80 20 Shun-9 oil 13 ZLWKWKHį C values of the oil source rocks from the O l /LDQJOLWDJH)RUPDWLRQDQGLVPXFKOLJKWHUWKDQWKRVHRIWKH asphaltene dispersants Cambrian source rocks (Fig. 11). 20 40 60 80 FL, % DBF, % 4.4 Direction of oil charge Fig. 10'%)HUQDU\SORWVKRZLQJWKHUHODWLYHFRPSRVLWLRQRI)/'%77 GLEHQ]RIXUDQGLEHQ]RWKLRSKHQH'%)1RWHV)/ÀXRUHQH'%7 As discussed above, the Silurian oils from Wells Shun-9, (a) (b) -23 -23 Crude oils -24 -24 Oil sands P q -25 -25 -26 -26 J y -27 -27 C kl J k -28 -28 -29 -29 1+2 -30‰ ę 1y -30‰ -30 -30 į į C b -31 -31 O l -32 -32 -33 -33 -34 -34 -35 -35 -36 -36 Sat Oil Aro NSO Asp Sat Extract Aro NSO Asp Fig. 116WDEOHį C values for oils/extracts and their fractions (a) Silurian oils and oil sands from the Well Shun-9 DULP%DVLQ7SURVSHFWDUHD E SUHYLRXVO\DQDO\]HGRLOVRXUFHURFNVLQWKH $VSDVSKDOWHQHIUDFWLRQ$URDURPDWLFIUDFWLRQ162162FRPSRXQG1RWHV6DWVDWXUDWHGIUDFWLRQ -901 and -902H in the prospect area have similar hydrocarbon 5 Conclusions and stable carbon isotopic compositions and can be assumed 1) All the Silurian oils and oil sands from the Well Shun- WREHIURPWKHVDPHRLOVRIDPLO\WKDWWKHRLOUHVHUYRLU¿OOLQJ 9 prospect area share similar biomarker distributions and direction can be estimated. į C values, indicating that they belong to the same oil family Two commonly used reservoir filling tracers are shown and originated from a single source rock. The molecular in Fig. 12(a), (b), i.e., Ts/(Ts+Tm) and 4-/1-MDBT ratios composition features can be summarized as follows: low (Table 2), which can be successfully applied in the Tarim Pr/Ph and C /C tricyclic terpane (<1.0) ratios, “V” shape Basin (Wang et al, 2008). Their values all decreased markedly 21 23 C -C steranes distributions, low C -sterane and triaromatic from Well Shun-9, via Well Shun-901, to Well Shun-902H, 27 29 28 GLQRVWHURLGDEXQGDQFHVDQGOLJKWį C values. These are VXSSRUWLQJDJHQHUDORLO¿OOLQJRULHQWDWLRQIURPQRUWKZHVWWR correlated well to those of the previously analyzed O l southeast in Well Shun-9 prospect area (Fig. 12). Based on 3 source rocks and are suggested to be indicative of the Upper that, we can also conclude that oil source faults should be 2UGRYLFLDQJHQHWLFDI¿QLW\ present to the northwest of our study area. C, ‰ C, ‰ Pet.Sci.(2013)10:432-441 441 (a) (b) Shun-9/0.56 4.0 Shun-9/0.56 4.0 Well/Ts/(Ts+Tm) value Isometric line Well/(4-/1-MDBT) value Isometric line Fault Oil filling orientation Fault Oil filling orientation Shun-9/0.56 Shun-9/6.99 0.52 6.0 0.50 5.0 4.0 0.48 0.46 0.44 Shun-902H/3.08 Shun-902H/0.44 Shun-901/0.46 Shun-901/4.57 Fig. 12 The oil charging orientation determined by Ts/(Ts+Tm) (a) and 4-/1-methyldibenzothiophene (4-/1-MDBT) ratios (b) DULP7%DVLQ-RXUQDORI3DODHRJHRJUDSK\   LQ 2) Different levels of biodegradation occurred in the oils/ Chinese) oil sands from different intervals. The oil sands from the 3-1 QJ=;3DQJ-LD;4/LX/HW)DO4XDQWL¿FDWLRQRIWKHK\GURFDUERQ S k interval of the Kelpintag Formation have been heavily destroyed by Silurian bituminous sandstone in the Tarim Basin. affected by biodegradation. This was evidenced by removal Science in China (Series D: Earth Sciences). 2008. 38(S1): 89-94 (in of the most n-alkanes, high proportion of NSO+Asp fractions, Chinese) WKHPDJQLWXGHRIWKH³8&0´DQGSUHVHQFHRIQRUKRSDQHV DQJ535=:'DL<-HWDO3HWUROHXP/LQ*HRFKHPLFDO6LJQL ¿FDQFH Comparatively, the oils and oil sands from the S k member of PAH in Fossil Fuel. Beijing: Geological Publishing House. 1987: only suffered light biodegradation. The evidence includes the 129-140 (in Chinese) presence of intact n-alkanes with slight-moderate “UCM” and 46KD<;*0D/L</HWDO&KDUDFWHULVWLFVRIVWULNHVOLSIDXOWDQG DEVHQFHRIQRUKRSDQHV its controlling on oil in Shuntuoguole region, middle Tarim Basin. 3-1 The two oil sands from the S k section are devoid of the Petroleum Geology and Experiment. 2012. 34(2): 120-124 (in Chinese) protection of the S k seal, which may be the principal reason OS533KL *LOEHUW7'DQG)ULHGULFK-%LF\FOLFVHVTXLWHUSHQRLGVDQG why they suffered heavy biodegradation, while the other 1 2 diterpenoids in Australian crude oils. Geochimica et Cosmochimica samples from the S k member with an S k seal were only 1 1 2 $FWD lightly biodegraded. It suggests that the S k middle mudstone OS53KL3 *LOEHUW7'DQG)ULHGULFK-*HRFKHPLFDOFRUUHODWLRQRI member of the Kelpintag Formation is significant in the -$3($$XVWUDOLDQFUXGHRLOV protection of Silurian hydrocarbons. Q<.+4XD RX+%4L/;HWDO$QDO\VLVRIJHRORJLFDOFRQGLWLRQV 3) A general oil filling orientation from northwest to DQGH[SORUDWLRQSRWHQWLDORI6LOXULDQSRROVLQWKH/LDQJVKXQUHJLRQ southeast was deduced, based on the decreased Ts/(Ts+Tm) QRUWKHUQVORSHRID]KRQJ7-RXUQDORI0LQHUDORJ\DQG3HWURORJ\ and 4-/1-MDBT ratios in the oils from Well Shun-9, via Well 2008. 28(4): 100-108 (in Chinese) Shun-901, to Well Shun 902H. Sof er Z. Stable isotopes in petroleum exploration. In: Merrill R K (ed.), Source and Migration Processes and Evaluation Techniques. AAPG, Acknowledgements Tulsa. 1991: 103-106 Wan g C G, Wang T G, Zhang W B, et al. Molecular geochemistry and We would like to thank the Northwest Branch Company, classifications of genetic types of petroleum from Tahe Oilfield SINOPEC for access to samples and grant support. We also of the Northern Tarim Basin. Acta Sedimentologica Sinica. 2006. WKDQN6KL6KHQJEDR=KX'DQDQG=KX/HLIRUDVVLVWDQFHZLWK 24(6): 900-907 (in Chinese) GC and GC-MS analysis. DQJJ7*&+H-)HW4:DO2LO¿OOLQJKLVWRU\RIWKH2DQ: UGRYLFLDQ DULP%DVLQ1:7DKH2LO¿HOGRLOUHVHUYRLULQWKHPDMRUSDUW7RIWKH References China. Organic Geochemistry. 2008. 39(11): 1637-1646 QJ:;LR/&KHQ++XQ</HWDO +\GURFDUERQFKDUJLQJKLVWRU\ QDQ-%LRGHJUDGDWLRQ&RQRIF UXGHRLOVLQUHVHUYRLUV,Q%URR NV-DQG for Silurian reservoirs of Shuntuoguole block in the north slope of HOWH:'+ HGV $GYDQFHVLQ3HWUROHXP*HRFKHPLVWU\/RQGRQ Tazhone Uplift, Tarim Basin: Constraints from fluid inclusion of $FDGHPLF3UHVV Well Shun 9. Acta Petrolei Sinica. 2013. 34(2): 239-246 (in Chinese) Gal imov E M. Isotope organic geochemistry. Organic Geochemistry. L*0=KDDQGDQJ:--$QDO\VLVRISHWUROHXPJHRORJ\LQD]KRQ7J 2006. 37: 1200-1262 region. Acta Petrolei Sinica. 1999. 20(4): 1- 6 (in Chinese) QJ*+7KH+XD2ULJLQDQG*HRFKHPLFDO6LJQL¿FDQFHRI)OXRUHQHDQG DQJ=QJ0+=KDQJ/:5+HWDO&RQWUROOLQJIDFWRUVRI6LOXULDQ=KD its Derivatives in Fossil Fuels. Beijing: Science Press. 1987. 211-220 high-quality reservoirs in Tarim Basin and selection of exploration (in Chinese) GLUHFWLRQ&KLQD3HWUROHXP([SORUDWLRQ   LQ Hug hes W B. Use of thiophenic organosulfur compounds in Chinese) characterizing crude oils derived from carbonate versus siliciclastic 5.=KX/XR+H3' %HWDO6HGLPHQWDU\IDFLHVDQGPRGHOVRIWKH sources. American Association of Petroleum Geologists, Tulsa. Kepingtage Formation of Silurian in Tazhong area, Tarim Basin. 1984. 18: 181-196 LQ&KLQHVH -RXUQDORI3DODHRJHRJUDSK\ --LD+ =KDQJ%0=KX6+HWDO6WUDWLJUDSK\VHGLPHQWDU\ characteristics and lithofacies palaeogeography of the Silurian in (Edited by Hao Jie) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Petroleum Science Springer Journals

Geochemical studies of the Silurian oil reservoir in the Well Shun-9 prospect area, Tarim Basin, NW China

Song, Daofu; Li, Meijun; Wang, T.-G.
Petroleum Science , Volume 10 (4) – Oct 13, 2013
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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/s12182-013-0293-2
Publisher site
See Article on Publisher Site

Abstract

432 Pet.Sci.(2013)10:432-441 DOI 10.1007/s12182-013-0293-2 Geochemical studies of the Silurian oil reservoir in the Well Shun-9 prospect area, Tarim Basin, NW China Song Daofu, Li Meijun and Wang T.–G 6WDWH.H\/DERUDWRU\RI3HWUROHXP5HVRXUFHVDQG3URVSHFWLQJ&KLQD8QLYHUVLW\RI3HWUROHXP%HLMLQJ&KLQD © China University of Petroleum (Beijing) and Springer-Verlag Berlin Heidelberg 2013 Abstract: &RPPHUFLDORLOÀRZKDVEHHQREWDLQHGIURPWKHVDQGVWRQHUHVHUYRLURIWKH/RZHU6LOXULDQ Kelpintag Formation in the Well Shun-9 prospect area. In the present studies, 10 Silurian oil and oil sand samples from six wells in the area were analyzed for their molecular and carbon isotopic compositions, oil DOWHUDWLRQ ELRGHJUDGDWLRQ RLOíVRXUFHURFNFRUUHODWLRQDQGRL oils and oil sands are characterized by low Pr/Ph and C /C tricyclic terpane (<1.0) ratios, “V”-pattern 21 23 C -C steranes distribution, low C VWHUDQHDQGWULDURPDWLFGLQRVWHUDQHDEXQGDQFHVDQGOLJKWį C 27 29 28 values, which can be correlated well with the carbonate source rock of the O l/LDQJOLWDJH)RUPDWLRQ IHUHQWRLOELRGHJUDGDWLRQ'LILWKOHYHOVKDYHDOVREHHQFRQ¿UPHGIHUHQWIRURLOVRLO:WKHVDQGVGLILQWHUYDOV 2 1 the S k seal, oils and oil sands from the S k interval of the Kelpintag Formation have only suffered light 1 1 3-1 ELRGHJUDGDWLRQDVFRQ¿UPHGE\WKHSUHVHQFHRI³8&0´DQGDEVHQFHRIQRUKRSDQHVZKHUHDVWKH6 k RLOVDQGVZHUHKHDYLO\ELRGHJUDGHG SURYHGE\WKHSUHVHQFHRIQRUKRSDQHV GXHWRWKHODFNRIWKH6 k VHDOZKLFKVXJJHVWVDVLJQL¿FDQWUROHRIWKH6 k seal in the protection of the Silurian oil reservoir. Based RQV7P V 7WKHDQG70'%7UDWLRVDVUHVHUYRLU¿OOLQJWUDFHUVDJHQHUDORLO¿OOLQJGLUHFWLRQIURP NW to SE has been also estimated for the Silurian oil reservoir in the Well Shun-9 prospect area. Key words:HOORLOíVRXUFH6KXQURFNSURVSHFWFRUUHODWLRQDUHD\JHRFKHPLVWU:6LOXULDQRLOUHVHUYRLU DOWHUDWLRQRLOUHVHUYRLU¿OLQJGLUHFWLRQ FRPSRVLWLRQV$OWHUDWLRQ ELRGHJUDGDWLRQ RLOíVRXUFHURFN 1 Introduction FRUUHODWLRQDQGRLO¿OOLQJRULHQWDWLRQZHUHGHGXFHGIURPWKH The Well Shun-9 prospect area is located at the south of results. WKH6KXQWXRJXROHDULP/RZ$IWHU%DVLQJRLQJ8SOLIWXQGHU7 several years exploration and after sand fracturing operations, 2 Geological setting FRPPHUFLDORLOÀRZVKDYHEHHQREWDLQHGIURPWKHVDQGVWRQH 7KH6KXQWXRJXROH/RZ8SOLIWLVLQIDFWVWLOODQHJDWLYH structure, being a relative uplift within a huge depression Shun-9, -901, -902H in the area in the last two years. zone. The depression zone is composed of the Manjiaer and Silurian sandstones are widely distributed in the ZDWL$'HSUHVVLRQVDVZHOODVWKH6KXQWXRJXROH/RZ8SOLIW 6KXQWXRJXROH/RZ8SOLIWDQGLWVDGMDFHQWUHJLRQV$VHDUO\ LQEHWZHHQ7KH6KXQWXRJXROH/RZ8SOLIWLVDOVRORFDWHG as 1994, Silurian commercial oil was discovered in Well TZ- between the Tabei Uplift on the north and the Tazhong Uplift 11, in the Tazhong Uplift on the south of the Shuntuoguole on the south (Fig. 1). /RZ8SOLIW =KDLDQGDQJ: 6LQFHWKHQWKH6LOXULDQ 7KH6KXQWXRJXROH/RZ8SOLIWRFFXUUHGGXULQJHDUO\ interval became one of the most important exploration targets Paleozoic time and subsequently underwent multi-stage =KDQJHWDO-LDHWDO $VWKHILUVWGLVFRYHUHG tectonic transformation. Compared with surrounding uplifts 6LOXULDQRLOUHVHUYRLULQ6KXQWXRJXROH/RZ8SOLIWVWXGLHVRQ and depressions, however, the geological setting of the LWDUHVLJQL¿FDQWIRURLOH[SORUDWLRQLQWKHDUHD 6KXQWXRJXROH/RZ8SOLIWLVPRUHVWDEOHWHFWRQLFDOO\DQG In the present study, three oil and seven oil sand samples more favorable for crude oil preservation (Xiong et al, 2013). from the Silurian oil reservoir were collected from six 5HJLRQDOO\WKH/RZHU0LGGOH6LOXULDQVWUDWDDUHZLGH exploration wells (sampling well location see Fig. 1) and spread and comprised of the S k Kelpintag, S t Tataertag 1 1 analyzed in the laboratory for oil molecular and isotopic and S yLPXJDQWDZX<)RUPDWLRQVLQWKH6KXQWXRJXROH/RZ 8SOLIW =KXHWDO-LDHWDO)LJ$V DSULQFLSDO *Corresponding author. email: wwttgg@aliyun.com reservoir interval, the S k Kelpintag Formation can be divided Received August 8, 2013 UHVHUYRLUVRIWKH/RZHU6LOXULDQ.HOSLQWDJ)RUPDWLRQDWHOOV 6LOXULDQWKHGLUHFWLRQ$OO¿OOLQJUHVHUYRLUO Belt No.1 Fault Tazhong Tazhong Uplift Kunlun Mountains S k pinchout boundary Pet.Sci.(2013)10:432-441 433 1 2 3-1 LQWRWKUHHPHPEHUVWKH6 k lower sandstone, S k middle the S k lower sandstone section (Ma et al, 2012). 1 1 1 3 3 1 mudstone and S k upper sandstone members, while the S k The overlying S t lower red mudstone member of the 1 1 1 upper member also can be subdivided into three sections, Tataertag Formation, S k middle mudstone member and 3-1 3-2 3-3 3-2 i.e., S k lower sandstone, S k middle mudstone and S k S k middle mudstone section of the Kelpintag Formation 1 1 1 1 upper sandstone sections (Fig. 2). So far, however, the major constitute three sets of effective regional seals for Silurian oil Silurian reservoirs for movable oil production are only UHVHUYRLUVZLWKLQWKH6KXQWXRJXROH/RZ8SOLIW 4XDQHWDO discovered within the S k lower sandstone member and also -LDQJHWDO)LJ Legend Tabei Uplift Town YM206 Well location MN1 YJ1X Tectonic units YJ2X HD2 border Major fault YN1 Minor fault S8 HD5 Alaer Shuntuoguole Low Uplift AM1 YN2 Awati Well Shun-9 prospect area Depression Mc1 AM2 S9 S903H Manjiaer Sx2 S905H Ad1 S904H S902H Mx2 Depression S901 SX1 S1 S7 S5 TZ45 Tianshan Mountains SN3 TZ32 TZ31 TZ54 Tarim Basin TZ12 SN1 TZ19 SN2 Guchengxu Uplift Fig. 1*HRORJLFDOPDSRIWKH6KXQWXRJXROH/RZ8SOLIW 7KHVWDEOHFDUERQLVRWRSLFFRPSRVLWLRQV į C) of oils/ 3 Experimental extracts and their fractions were analyzed on a Thermoscience Oil sands were Soxhlet-extracted with chloroform 70RGHO,5060$7KHRLOVH[WUDFWVDQGWKHLUIUDFWLRQV (CHCl ). The oil sand/source rock extracts and oils were were burned to produce individual CO peaks on a Flash HT o 13 deasphalted using n-hexane, and then fractionated using copper oxide reaction furnace at 980 &7KHLUį C values column chromatography (silica gel vs. alumina 3:1) into ZHUHPHDVXUHGE\LQWHJUDWLRQRIWKHPDVVHVDQGLRQ saturate, aromatic and NSO fractions by sequential elution current counts of CO peaks. A CO reference gas with known 2 2 13 13 with n-hexane, toluene and chloroform. į C C PDB Gas chromatography (GC) of the saturate fractions was values of the oils/extracts and their fractions were reported performed using an Agilent Model 6890 gas chromatograph LQWKHįQRWDWLRQUHODWLYHWRWKHUHIHUHQFHJDV7KHDYHUDJH HTXLSSHGZLWKDIXVHGVLOLFDFROXPQ +3PîPP values of at least two runs for each sample were reported and i.d.). The oven temperature program was from 100 C (1 min) only results with a standard deviation of less than 0.3‰ were o o to 300 C (held 10 min) at 4 C/min. Helium was used as used. carrier gas. GC–mass spectrometry (GC–MS) analysis of saturated 4 Results and discussion and aromatic fractions were conducted using an Agilent 0RGHOJDVFKURPDWRJUDSKILWWHGZLWKD'%06 4.1 Oil physical properties and gross composition capillary. The GC temperature operating conditions for the o o o The Silurian oil reservoir in the Well Shun-9 prospect saturated fraction were: 100 C (1 min) to 220 C at 4 C/ o o area has a regular variation in oil physical properties and min and, then to 300 & KHOGPLQ DW &PLQIRUWKH o o gross composition as follows. From Well Shun-9, via Well aromatic fraction were: 80 C (1 min) to 300 & KHOGPLQ Shun-901, to Well Shun-902H, the oil density, viscosity, at 3 C/min. Saturated and aromatic hydrocarbon biomarker sulfur content as well as aromatic and asphaltene contents parameters were calculated from integrated peak areas on the are gradually increasing, whereas their saturate contents and mass chromatograms. YDOXHZDVSXOVHGLQWRWKHPDVVVSHFWURPHWHU7KHį 434 Pet.Sci.(2013)10:432-441 Petroleum Depth PGHHS DSSHDUORZHUVDWXUDWHFRQWHQW Series Formation Member Section Lithology system and saturates to aromatics ratio (1.1-1.9) as well as higher DVSKDOWHQHFRQWHQW  2QWKHFRQWUDU\WKH 1 deeper S k ORZHUVDQGVWRQHPHPEHURLOVDQGV DURXQG S t 1 Tataertage and saturates to aromatics ratio (2.2-3.0) as well as lower DEOH 7DVSKDOWHQHFRQWHQWV 4.2 Hydrocarbon composition 3-3 S k 4.2.1 Acyclics The n-alkane series of the Silurian oils in the S k lower sandstone member reservoir occur with a unimodal distribution pattern, with maximum carbon number at nC or 3-2 S k 1 nC and an nC -/nC + ratio of 1.71-3.23, suggesting a high 21 22 maturity level. In addition, all their GC traces have a baseline S k “hump” resulting from unresolved complex mixture (UCM) in the oil, but only the heavy oil of Well Shun-902H shows a more obvious UCM “hump”, indicating the disparity of the biodegradation effect (Fig. 3(a)-(c)). Lower As for the oil sand extracts in the deeper S k lower Silurian sandstone member reservoir, their n-alkane series almost have 3-1 S k a similar unimodal distribution pattern with the oils, with an Kelpintag average nC -/nC + ratio of 1.72, while the maximum carbon 21 22 number has been transferred to nC or nC , showing an 17 19 adsorption effect of reservoir rock (Fig. 3(d)-(f), Table 2). In the oil sand extracts for the reservoir rocks of 3-1 the shallower S k sandstone section, however, most n-alkanes have been moved out and all their GC traces 2 show a predominant UCM “hump” as expected for severely S k ELRGHJUDGHGRLOV &RQQDQ)LJ J  K Besides n-alkanes, pristine (Pr) and phytane (Ph) are also detected in both oils and oil sand extracts in the Well Shun-9 prospect area (Fig. 3), all of which show an equal S k abundance tendency with the Pr/Ph ratio ranging from 0.84 to 0.98 (Table 2), revealing similar sedimentary and diagenesis environments of the oil source bed. Moreover, as shown in Fig. 4, the Pr/Ph ratios of our analyzed samples fall into the ratio range of Tahe oils, which are derived from Upper Sandstone Siltstone Argillaceous Silty Mudstone Seal Reservoir Ordovician source rocks (Wang et al, 2006). siltstone mudstone 4.2.2 Terpanoids *HQHUDOL]HG/RZHU6LOXULDQVWUDWLJUDSK\ Fig. 2 As predominant terpanoid components of the Silurian LQWKH6KXQWXRJXROH/RZ8SOLIW oils and oil sands in the well Shun-9 prospect area, tricyclic saturates to aromatics ratios seem to be decreasing, so that terpane series have a much higher abundance than the the reservoir oils vary from regular black oil in Wells Shun- pentacyclic hopane series, with the tricyclics to hopanes 9 and Shun-901 to heavy oil in Well Shun-902H. Moreover, UDWLRV 77+ IURPDEOH 7 ,QWULF\FOLFVWKH& the wax content also shows a wide range in different samples, tricyclic terpane is predominant over C tricyclic terpane, varying from 3.0% to 16.1% (Table 1). The gradual variations resulting in C /C tricyclic terpane ratio <1.0 (C /C TT, 21 23 21 23 in oil physical properties and gross compositions support an DEOH7 )LJ ZKLFKFDQEHZHOOFRUUHODWHGZLWKWKH increased biodegradation degree from the oil in Well Shun-9, previously analyzed oil source rock of the O l/LDQJOLWDJH via Well Shun-901, to Well Shun-902H. Formation instead of the Cambrian source rock in the Tarim As a whole, all the gross compositions of oil sands show %DVLQ )LJ L  M relatively low saturate contents as well as high aromatic, C to C (no C ) hopane series and gammacerane are 27  28 NSO-compound and asphaltene contents owing to the detected, showing a regular distribution pattern and low adsorptive effect in the sandstone reservoir (Table 1). gammacerane/C hopane ratio 0.19 in average, in the Silurian Due to the disparity in total seal thickness and secondary RLOVDQGRLOVDQGV )LJ alteration (biodegradation), the gross composition of oil A distinct feature between the samples from different sands from different intervals is also varied. Oil sands in LQWHUYDOVLVWKHUHODWLYHDEXQGDQFHRIQRUKRSDQHV 3-1 the shallower S k ORZHUVDQGVWRQHVHFWLRQ DERXW QRUKRSDQHVDUHDEVHQWLQWKHRLOVDQGRLOVDQGVIURPWKH PLQGHSWK KDYHKLJKHUVDWXUDWHFRQWHQW   Pet.Sci.(2013)10:432-441 Table 1 Basic geochemical data for the Silurian oils and oil sands in the Well Shun-9 prospect area Physical properties Gross composition ,VRWRSLFFRPSRVLWLRQį C, ‰ PDB Depth Mem./ No. Well Sample Density Viscosity Sulfur Wax Sat Aro NSO Asp Oil/ m Sect. Sat/Aro Sat Aro NSO Asp g/cm mPa s % % % % % % Extract 1 Shun-9  0.868  0.46 16.1 76.3  4.9 2.9 4.8 -32.3 -32.3 -31.8 -31.9 -32.1 Regular oil 2 Shun-901  0.876 22.8 0.46 2.98 67.2 18.6 6.8 7.4 3.6 -31.9 -31.9 -31.8  -32.1 S k Heavy 3 Shun-902H   871.9    24.6 3.0 17.4 2.2 -31.6  -31.8 -31.3 -32.2 oil 4 Shun-1  -- -- -- -- 28.6 24.8 14.3 32.3 1.1 -31.8 -31.7 -31.8 -32.0 -32.3 3-1 S k Shun-902H  -- -- -- -- 31.8  6.0  1.9 -32.2 -32.2 -32.2 -32.1 -32.9 Oil 6 Shun-901  -- -- -- --   9.1 7.9 2.2 -31.7 -32.2 -31.9 -31.4 -31.2 sand 7 Shun-902H  S k -- -- -- --  23.0 11.1 11.1 2.4 -32.1 -31.3 -32.2 -32.2 -32.6 8 Shun-904H  -- -- -- -- 62.6 21.0 9.9  3.0 -31.7  -31.3 -31.4 -31.8 $VSDVSKDOWHQHIUDFWLRQ$URDURPDWLFIUDFWLRQ162162FRPSRXQGIUDFWLRQ1RWHV6DWVDWXUDWHGIUDFWLRQ nC nC 14 (a) (b) 1 1 Shun-9, S k , 5560-5589 m, regular oil Shun-901, S k , 5496-5504 m, regular oil 1 1 Pr Ph Pr Ph UCM UCM nC (c) nC (d) 15 17 Shun-902H, S k , 5513-5530 m, heavy oil 1 Shun-901, S k , 5500 m, oil sand Ph Pr Ph Pr UCM UCM nC nC 17 19 (f) (e) Ph 1 1 Pr Shun-902H, S k , 5517 m, oil sand Shun-904H, S k , 5568 m, oil sand 1 1 Ph Pr UCM UCM (g) (h) 3-1 3-1 Shun-1, S k , 5316 m, oil sand Shun-902H, S k , 5303 m, oil sand 1 1 Fig. 3 Gas chromatograms of saturated hydrocarbon fraction SULVWDQH3KSK\WDQH1RWHV3U nCQRUPDODONDQHV iPROHFXODUFDUERQQXPEHU8&0XQUHVROYHGFRPSOH[PL[WXUH LQWHUQDOVWDQGDUG S k member, while they are abundant in the oil sands from the C QRUKRSDQHDQG& ELVQRUKRSDQHDUHWKH 1 29 28 3-1 S k interval, with the ratio of C QRUKRSDQH& -hopane GRPLQDQWGHPHWK\ODWHGFRPSRXQGLQWKHRLOVDQGVIURP 1 29 30 3-1 from 0.36 to 0.41. As shown in m/z 177 mass chromatograms, the S k LQWHUYDOEXWDZKROHGLVWULEXWLRQRIQRUKRSDQHV 1 436 Pet.Sci.(2013)10:432-441 Table 2 Basic geochemical parameters for the Silurian oils and oil sands in the Well Shun-9 prospect area Acyclic alkanes Terpanoids Steroids Polyaromatic hydrocarbons Depth Mem./ Regular C  (C +C )P/ 29 21 22 No. Well Sample '%))/'%7 nC -/ Pr/ Ph/ C /C Ts/ TT/ G/ 4-/1- 21 21 23 m Sect. steranes, % Pr/Ph NH/ Dia/RS (C -C ) 27 29 nC + nC nC TT (Ts+Tm) H C H MDBT 22 17 18 30 C C C )/ DBT DBF C H RS 30 27 28 29 1 Shun-9   0.84 0.3 0.43 0.43  1.84  -- 0.34 0.2 0.46 0.28 0.2 16.6 20.7 62.7 6.99 Regular oil 2 Shun-901  3.23   0.63  0.46   -- 0.47 0.2 0.33 0.28 0.34  24.7 18.0 S k Heavy 3 Shun-902H  1.71 0.92 0.44   0.44 2.86 0.18 -- 0.36 0.2 0.44 0.34 0.3 64.9 21.7 13.4 3.08 oil 4 Shun-1  1.48  0.69 1.01   1.84 0.16 0.41 0.2 0.41 0.39  0.21 77.3 13.9 8.80 -- 3-1 S k Shun-902H  2.34 0.86  0.86  0.37  0.17 0.36 0.39 0.19 0.43 0.24 0.31  4.30 4.20 -- Oil 6 Shun-901  1.86 0.94   0.48   0.29 -- 0.31 0.23 0.46 0.22 0.19 92.1 4.66 3.24 -- sand 7 Shun-902H  S k 1.38 0.98 0.44  0.49 0.38 2.62  -- 0.43 0.21 0.36 0.27 0.22 87.8 7.10  -- 8 Shun-904H  1.39 0.91 1.07 1.12 0.49 0.46 2.68 0.12 --  0.21 0.44 0.3 0.32 74.2 17.2 8.60 -- Notes: nC -/nC +, C -n-alkanes/C +nDONDQHV3U3KSULVWDQHSK\WDQH3U nC , pristane/C nDONDQH3K nC , phytane/C nDONDQH& /C 21 21 21 21 17 17 18 18 21 23 TT, C tricyclic terpane/C WULF\FOLFWHUSDQHV7P V 7&7 18Į (H)-trisnor-neohopane/C [18Į (H)-trisnor-neohopane+17Į + WULVQRUKRSDQH@ 21 23 27 27 77+WULF\FOLFWHUSDQHVKRSDQHV*& H, gammacerane/C KRSDQH& 1+& H, C QRUKRSDQH& KRSDQH'LD56GLDVWHUDQHVUHJXODU 30 30 29 30 29 30 VWHUDQHV & +C )P/(C -C )RS, C +C pregnanes/C -C UHJXODUGLEHQ]RIXUDQVWHUDQHV0'%7GLEHQ]RWKLRSKHQH)/'%)ÀXRUHQH'%7 21 22 27 29 21 22 27 29 4-/1-methyldibenzothiophene -0U 025 C VWHUDQHVZRXOGEHOHVVWKDQLQUHODWLYHDEXQGDQFH Oils /oil s ands fr om s tudy ar ea and diasterane has a relatively high abundance (Fig. 7). The 2.0 Oils fr om Tahe field characteristics of “V” pattern C -C steranes distributions 27 29 and low relative abundance of C 5VWHUDQH  DUH correlated well with the previously analyzed O l/LDQJOLWDJH Formation source rocks and are markedly different from the 1.3 Cambrian source rocks (Fig. 7(i), (j)). Furthermore, as shown in Fig. 8, all the Silurian oils and 1.0 oil sands fall into a tight cluster and have a similar C -C 27 29 regular steranes distribution to the Ordovician source rocks previously analyzed. 0.5 0.5 4.2.4 Triaromatic steroids 7KHP]PDVVFKURPDWRJUDPVRIDURPDWLF hydrocarbon fractions are shown in Fig. 9, exhibiting the 03 . 04 . 05 . -0. 3 -0. 2 -0.1 0 01 . 0.2 distribution of triaromatic dinosteranes and triaromatic steroids. In all the Silurian oils and oil sands, methyl- Pr/nC -Ph/nC 17 18 triaromatic steroids are only present in low concentration, Plot of Pr/Ph ratios vs. (Pr/nC -Ph/nC ) values Fig. 4 17 18 especially triaromatic dinosteroids are absent or only present 1RWHV3USULVWDQH3KSK\WDQH nCQRUPDODONDQHV i, molecular in trace amount, which can also be well correlated with the carbon number previously analyzed O l/LDQJOLWDJH)RUPDWLRQVRXUFHURFNV and apparently different from the Cambrian source rocks paralleling the 17Į(H), 21ȕ(H)-hopanes (from C up to C ) 29 33 in which the triaromatic steroids are abundant especially LVSUHVHQWLQORZFRQFHQWUDWLRQ )LJ 1RUKRSDQHVDUH triaromatic dinosteranes (Fig. 9(i), (j)). produced when all straight-chain and isoprenoid alkanes, and 4.2.5 Polyaromatic hydrocarbons most of the bicyclic alkanes have already been removed (Philp Various polyaromatic hydrocarbons have been HWDO VRWKH\DUHWDNHQDVHYLGHQFHRIH[WHQVLYH detected, especially the fluorenes, dibenzothiophenes, and bacterial activity. GLEHQ]RIXUDQV)OXRUHQH )/ GLEHQ]RWKLRSKHQH '%7 DQG 4.2.3 Steroids dibenzofuran (DBF) share a similar molecular structure, Usually steroids consist of C -C regular sterane series 27 29 so they are considered to have originated from the same and C -C pregnanes. In the Silurian oils and oil sands, 21 22 precursor and their relative compositions can indicate the the steroids show a relatively high abundance of C -C 21 22 SULPDU\VHGLPHQWDU\HQYLURQPHQW +XDQJ/LQHWDO pregnanes in comparison with C -C regular steranes, and 27 29 1987). Abundant benzothiophenes in oils have been proposed the C -C pregnanes to C -C steranes ratio [(C +C )P/ 21 22 27 29 21 22 to indicate an anoxic sedimentary environment, whereas, (C -C )Rs] ranges from 0.19 to 0.34 with 0.27 in average. 27 29 dominant dibenzofuran represents an oxidative environment Moreover, the distribution of C -C regular steranes 27 29 (Hughes, 1984). abundance appears a C >C <C “V” pattern, in which the 27 28 29 As shown in Fig. 10, all the analyzed samples, except Pr/Ph Pet.Sci.(2013)10:432-441 437 (a) C TT (b) C TT 1 1 Shun-901, S k , 5496-5504 m, regular oil Shun-9, S k , 5560-5589 m, regular oil C /C TT=0.55 C /C TT=0.43 21 23 21 23 C H C TT C TT 21 C H C H C H C H (c) (d) Shun-902H, S k , 5513-5530 m, heavy oil Shun-901, S k ,5500 m, oil sand 1 1 C /C TT=0.50 C /C TT=0.48 21 23 21 23 (e) (f) Shun-902H, S k , 5517 m, oil sand 1 Shun-904H, S k , 5568 m, oil sand C /C TT=0.49 C /C TT=0.49 21 23 21 23 (g) (h) 3-1 3-1 Shun-1, S k , 5316 m, oil sand Shun-902H, S k , 5503 m, oil sand C /C TT=0.51 C /C TT=0.58 21 23 21 23 (j) (i) Lunnan-46, 5 l, 6164 m, grey limestone 3 He-4,ɚ , 4598-4599 m, grey marl C /C TT=0.51 21 23 C /C TT=1.66 21 23 m/z 191 mass chromatograms of saturated hydrocarbon fraction, showing the distribution of tricyclic terpane Fig. 5 series and hopane series WULF\FOLFWHUSDQH+KRSDQH&771RWHV PROHFXODUFDUERQQXPEHU**DPPDFHUDQH C DNH C DNH 28 3-1 Shun-902H, S k , 5303 m, oil sand 3-1 1 Shun-1, S k , 5316 m, oil sand C NH 29 C NH C NH C NH C NH C NH 33 Fig. 6P]PDVVFKURPDWRJUDPVRIVDWXUDWHGK\GURFDUERQIUDFWLRQVKRZLQJWKHKRPRORJRXVVHULHVRIQRUKRSDQHV 1RWHV'1+ELVQRUKRSDQH1+QRUKRSDQH& : molecular carbon number i 438 Pet.Sci.(2013)10:432-441 1 (a) 1 (b) Shun-9, S k , 5560-5589 m, regular oil Shun-901, S k , 5496-5504 m, regular oil 1 1 C RS C P C %=19.9% C %=20.1% 28 28 C RS C P Dia C RS C RS C RS Dia C P C RS C P 1 (c) 1 (d) Shun-902H, S k , 5513-5530 m, heavy oil Shun-901, S k , 5500 m, oil sand 1 1 C %=20.4% C %=23.0% 28 28 1 (e) 1 (f) Shun-902H, S k , 5517 m, oil sand Shun-904H, S k , 5568 m, oil sand 1 1 C %=20.9% C %=20.9% 28 28 3-1 (g) 3-1 (h) Shun-1, S k , 5316 m, oil sand Shun-902H, S k , 5303 m, oil sand 1 1 C %=20.0% C %=18.9% 28 28 Lunnan-46, O l, 6164 m, grey limestone (i) He-4,ɚ , 4598-4599 m, grey marl (j) C %=20.5% C %=35.0% 28 28 Fig. 7 m/z 217 mass chromatograms of saturated hydrocarbon fraction, showing the distribution of sterane series SUHJQDQH'LDGLDVWHUDQH5VUHJXODUVWHUDQH&1RWHV3 , molecular carbon number C%C % 28 28 (a) (b) Crude oils Oil sands 25 75 25 75 50 50 50 50 75 25 75 25 20 50 75 20 50 75 C%C C%C % % 27 29 27 29 Fig. 8 Ternary plots showing the relative content of C -C regular steranes 27 29 DULP%DVLQ7HOO6KXQSURVSHFWDUHD E SUHYLRXVO\DQDO\]HGRLOVRXUFHURFNVLQWKH: D 6LOXULDQRLOVDQGRLOVDQGVIURPWKH Pet.Sci.(2013)10:432-441 439 1 1 Shun-9, S k , 5560-5589 m, regular oil (a) Shun-901, S k , 5496-5504 m, regular oil (b) 1 1 9 9 7,8 7,8 9 4,6 4,6 6 3 6 1 1 Shun-902H, S k , 5513-5530 m, heavy oil (c) Shun-901, S k , 5500 m, oil sand (d) 1 1 7,8 4,6 9 7,8 7 4,6 6 6 8 8 1 1 Shun-902H, S k , 5517 m, oil sand (e) Shun-904H, S k , 5568 m, oil sand (f) 1 1 4,6 7,8 4,6 7,8 7 6 6 3 8 8 3 8 3-1 3-1 Shun-1, S k , 5316 m, oil sand (g) Shun-902H, S k , 5503 m, oil sand (h) 1 1 6 7,8 7,8 4,6 4 4,6 8 3 Tazhong-30, O l, 4918 m, grey marl (i) (j) Tadong-2,ɨ , 4918 m, grey-dark mudstone 4,6 7,8 4,6 6 6 7,8 8 3 Fig. 9 P]PDVVFKURPDWRJUDPVRIDURPDWLFK\GURFDUERQIUDFWLRQVKRZLQJWKHGLVWULEXWLRQRIWULDURPDWLFVWHURLGV 1RWHV WULDURPDWLFGLQRVWHURLGVPHWK\OHW\OWULDURPDWLFVWHURLGVĮPHWK\OHWK\OWULDURPDWLFVWHURLGVPHWK\O 24-ethyl-triaromatic steroids the oil from S9 well, are characterized by dominant GLEHQ]RIXUDQDFFRXQWHGIRU!RIWRWDO)/DQG'%7'%) GLEHQ]RWKLRSKHQH DFFRXQWLQJIRURIWRWDO The reason was probably due to contamination by chemical )/'%7DQG'%)DEOH7 LQGLFDWLQJDVWURQJO\DQR[LF additives added in Well Shun-9 during oil test operation, PDULQHHQYLURQPHQW$QDEQRUPDOLW\RIWKH)/'%7'%) especially asphaltene dispersants with dominant dibenzofuran composition occurred in the oil from Well Shun-9, in which (Fig. 10). 440 Pet.Sci.(2013)10:432-441 4.3 Stable carbon isotopic composition DBT, % 7KHį C compositions of oils or extracts can help to Crude oils Oil sands determine oil–oil and oil–source rock relationships (Sofer, 20 80 *DOLPRY 7KHį C values for the Silurian oils and oil sand extracts range from -31.6‰ to -32.3‰ (Table 1) and differ by less than 1‰, suggesting that they may have 40 60 WKHVDPHJHQHWLFRULJLQ7KHDYHUDJHį C value for saturate, aromatic, resin and asphaltene fractions is -31.8‰, -31.9‰, 60 40 -31.8‰ and -32.2‰, respectively (Fig. 11). All the Silurian oils/extracts and their fractions are characterized by relative light carbon isotopic composition, which corresponds well 80 20 Shun-9 oil 13 ZLWKWKHį C values of the oil source rocks from the O l /LDQJOLWDJH)RUPDWLRQDQGLVPXFKOLJKWHUWKDQWKRVHRIWKH asphaltene dispersants Cambrian source rocks (Fig. 11). 20 40 60 80 FL, % DBF, % 4.4 Direction of oil charge Fig. 10'%)HUQDU\SORWVKRZLQJWKHUHODWLYHFRPSRVLWLRQRI)/'%77 GLEHQ]RIXUDQGLEHQ]RWKLRSKHQH'%)1RWHV)/ÀXRUHQH'%7 As discussed above, the Silurian oils from Wells Shun-9, (a) (b) -23 -23 Crude oils -24 -24 Oil sands P q -25 -25 -26 -26 J y -27 -27 C kl J k -28 -28 -29 -29 1+2 -30‰ ę 1y -30‰ -30 -30 į į C b -31 -31 O l -32 -32 -33 -33 -34 -34 -35 -35 -36 -36 Sat Oil Aro NSO Asp Sat Extract Aro NSO Asp Fig. 116WDEOHį C values for oils/extracts and their fractions (a) Silurian oils and oil sands from the Well Shun-9 DULP%DVLQ7SURVSHFWDUHD E SUHYLRXVO\DQDO\]HGRLOVRXUFHURFNVLQWKH $VSDVSKDOWHQHIUDFWLRQ$URDURPDWLFIUDFWLRQ162162FRPSRXQG1RWHV6DWVDWXUDWHGIUDFWLRQ -901 and -902H in the prospect area have similar hydrocarbon 5 Conclusions and stable carbon isotopic compositions and can be assumed 1) All the Silurian oils and oil sands from the Well Shun- WREHIURPWKHVDPHRLOVRIDPLO\WKDWWKHRLOUHVHUYRLU¿OOLQJ 9 prospect area share similar biomarker distributions and direction can be estimated. į C values, indicating that they belong to the same oil family Two commonly used reservoir filling tracers are shown and originated from a single source rock. The molecular in Fig. 12(a), (b), i.e., Ts/(Ts+Tm) and 4-/1-MDBT ratios composition features can be summarized as follows: low (Table 2), which can be successfully applied in the Tarim Pr/Ph and C /C tricyclic terpane (<1.0) ratios, “V” shape Basin (Wang et al, 2008). Their values all decreased markedly 21 23 C -C steranes distributions, low C -sterane and triaromatic from Well Shun-9, via Well Shun-901, to Well Shun-902H, 27 29 28 GLQRVWHURLGDEXQGDQFHVDQGOLJKWį C values. These are VXSSRUWLQJDJHQHUDORLO¿OOLQJRULHQWDWLRQIURPQRUWKZHVWWR correlated well to those of the previously analyzed O l southeast in Well Shun-9 prospect area (Fig. 12). Based on 3 source rocks and are suggested to be indicative of the Upper that, we can also conclude that oil source faults should be 2UGRYLFLDQJHQHWLFDI¿QLW\ present to the northwest of our study area. C, ‰ C, ‰ Pet.Sci.(2013)10:432-441 441 (a) (b) Shun-9/0.56 4.0 Shun-9/0.56 4.0 Well/Ts/(Ts+Tm) value Isometric line Well/(4-/1-MDBT) value Isometric line Fault Oil filling orientation Fault Oil filling orientation Shun-9/0.56 Shun-9/6.99 0.52 6.0 0.50 5.0 4.0 0.48 0.46 0.44 Shun-902H/3.08 Shun-902H/0.44 Shun-901/0.46 Shun-901/4.57 Fig. 12 The oil charging orientation determined by Ts/(Ts+Tm) (a) and 4-/1-methyldibenzothiophene (4-/1-MDBT) ratios (b) DULP7%DVLQ-RXUQDORI3DODHRJHRJUDSK\   LQ 2) Different levels of biodegradation occurred in the oils/ Chinese) oil sands from different intervals. The oil sands from the 3-1 QJ=;3DQJ-LD;4/LX/HW)DO4XDQWL¿FDWLRQRIWKHK\GURFDUERQ S k interval of the Kelpintag Formation have been heavily destroyed by Silurian bituminous sandstone in the Tarim Basin. affected by biodegradation. This was evidenced by removal Science in China (Series D: Earth Sciences). 2008. 38(S1): 89-94 (in of the most n-alkanes, high proportion of NSO+Asp fractions, Chinese) WKHPDJQLWXGHRIWKH³8&0´DQGSUHVHQFHRIQRUKRSDQHV DQJ535=:'DL<-HWDO3HWUROHXP/LQ*HRFKHPLFDO6LJQL ¿FDQFH Comparatively, the oils and oil sands from the S k member of PAH in Fossil Fuel. Beijing: Geological Publishing House. 1987: only suffered light biodegradation. The evidence includes the 129-140 (in Chinese) presence of intact n-alkanes with slight-moderate “UCM” and 46KD<;*0D/L</HWDO&KDUDFWHULVWLFVRIVWULNHVOLSIDXOWDQG DEVHQFHRIQRUKRSDQHV its controlling on oil in Shuntuoguole region, middle Tarim Basin. 3-1 The two oil sands from the S k section are devoid of the Petroleum Geology and Experiment. 2012. 34(2): 120-124 (in Chinese) protection of the S k seal, which may be the principal reason OS533KL *LOEHUW7'DQG)ULHGULFK-%LF\FOLFVHVTXLWHUSHQRLGVDQG why they suffered heavy biodegradation, while the other 1 2 diterpenoids in Australian crude oils. Geochimica et Cosmochimica samples from the S k member with an S k seal were only 1 1 2 $FWD lightly biodegraded. It suggests that the S k middle mudstone OS53KL3 *LOEHUW7'DQG)ULHGULFK-*HRFKHPLFDOFRUUHODWLRQRI member of the Kelpintag Formation is significant in the -$3($$XVWUDOLDQFUXGHRLOV protection of Silurian hydrocarbons. Q<.+4XD RX+%4L/;HWDO$QDO\VLVRIJHRORJLFDOFRQGLWLRQV 3) A general oil filling orientation from northwest to DQGH[SORUDWLRQSRWHQWLDORI6LOXULDQSRROVLQWKH/LDQJVKXQUHJLRQ southeast was deduced, based on the decreased Ts/(Ts+Tm) QRUWKHUQVORSHRID]KRQJ7-RXUQDORI0LQHUDORJ\DQG3HWURORJ\ and 4-/1-MDBT ratios in the oils from Well Shun-9, via Well 2008. 28(4): 100-108 (in Chinese) Shun-901, to Well Shun 902H. Sof er Z. Stable isotopes in petroleum exploration. In: Merrill R K (ed.), Source and Migration Processes and Evaluation Techniques. AAPG, Acknowledgements Tulsa. 1991: 103-106 Wan g C G, Wang T G, Zhang W B, et al. Molecular geochemistry and We would like to thank the Northwest Branch Company, classifications of genetic types of petroleum from Tahe Oilfield SINOPEC for access to samples and grant support. We also of the Northern Tarim Basin. Acta Sedimentologica Sinica. 2006. WKDQN6KL6KHQJEDR=KX'DQDQG=KX/HLIRUDVVLVWDQFHZLWK 24(6): 900-907 (in Chinese) GC and GC-MS analysis. DQJJ7*&+H-)HW4:DO2LO¿OOLQJKLVWRU\RIWKH2DQ: UGRYLFLDQ DULP%DVLQ1:7DKH2LO¿HOGRLOUHVHUYRLULQWKHPDMRUSDUW7RIWKH References China. Organic Geochemistry. 2008. 39(11): 1637-1646 QJ:;LR/&KHQ++XQ</HWDO +\GURFDUERQFKDUJLQJKLVWRU\ QDQ-%LRGHJUDGDWLRQ&RQRIF UXGHRLOVLQUHVHUYRLUV,Q%URR NV-DQG for Silurian reservoirs of Shuntuoguole block in the north slope of HOWH:'+ HGV $GYDQFHVLQ3HWUROHXP*HRFKHPLVWU\/RQGRQ Tazhone Uplift, Tarim Basin: Constraints from fluid inclusion of $FDGHPLF3UHVV Well Shun 9. Acta Petrolei Sinica. 2013. 34(2): 239-246 (in Chinese) Gal imov E M. Isotope organic geochemistry. Organic Geochemistry. L*0=KDDQGDQJ:--$QDO\VLVRISHWUROHXPJHRORJ\LQD]KRQ7J 2006. 37: 1200-1262 region. Acta Petrolei Sinica. 1999. 20(4): 1- 6 (in Chinese) QJ*+7KH+XD2ULJLQDQG*HRFKHPLFDO6LJQL¿FDQFHRI)OXRUHQHDQG DQJ=QJ0+=KDQJ/:5+HWDO&RQWUROOLQJIDFWRUVRI6LOXULDQ=KD its Derivatives in Fossil Fuels. Beijing: Science Press. 1987. 211-220 high-quality reservoirs in Tarim Basin and selection of exploration (in Chinese) GLUHFWLRQ&KLQD3HWUROHXP([SORUDWLRQ   LQ Hug hes W B. Use of thiophenic organosulfur compounds in Chinese) characterizing crude oils derived from carbonate versus siliciclastic 5.=KX/XR+H3' %HWDO6HGLPHQWDU\IDFLHVDQGPRGHOVRIWKH sources. American Association of Petroleum Geologists, Tulsa. Kepingtage Formation of Silurian in Tazhong area, Tarim Basin. 1984. 18: 181-196 LQ&KLQHVH -RXUQDORI3DODHRJHRJUDSK\ --LD+ =KDQJ%0=KX6+HWDO6WUDWLJUDSK\VHGLPHQWDU\ characteristics and lithofacies palaeogeography of the Silurian in (Edited by Hao Jie)

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Petroleum Science – Springer Journals

Published: Oct 13, 2013

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