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Incised valley filling deposits: an important pathway system for long-distance hydrocarbon migration—a case study of the Fulaerji Oilfield in the Songliao Basin

Incised valley filling deposits: an important pathway system for long-distance hydrocarbon... for long-distance hydrocarbon migration, are discussed in detail based on core and logging data. The sequence SQ of the Cretaceous Yaojia Formation is the main hydrocarbon-bearing layer in the Fulaerji y23 Oilfield. The hydrocarbon source of the oilfield is the Qijia-Gulong Sag which is about 80 km away from the Fulaerji Oilfi eld. The transport layer of long-distance hydrocarbon migration is the overlapped sandstone complex which fi lls the incised valley. The incised valley developed during the depositional period from the late Qingshankou Formation to the early Yaojia Formation of Cretaceous (SQ -SQ ) qn4 y1 was about 70 km long and 20 km wide, and extended in the NW-SE direction. The overlapped filling of the incised valley mainly occurred in the expanding system tract of the third-order sequence SQ (EST ). y23 y23 Towards the basin, incised valley fi lling deposits overlapped on the delta developed in the early period, and towards the basin margin, incised valley fi lling deposits were covered by the shore-shallow lacustrine sandy beach bar developed in the maximum fl ooding period. All of the delta, the incised valley fi lling and the shore-shallow sandy beach bar are sandstone-rich, and have high porosity and permeability, and can form an effective hydrocarbon migration and accumulation system. Deltaic sand bodies collected and pumped hydrocarbon from the active source, incised valley filling depositional system completed the long-distance hydrocarbon migration, and lithological traps of shore-shallow lacustrine sandy beach bar accumulated hydrocarbon. The incised valley fi lling sequences are multi-cycle: an integrated short- term filling cycle was developed on the erosion surface, and the sequences upward were mud-gravel stone, medium-fi ne sandstone containing terrigenous gravels and muddy pebbles with cross bedding, silty mudstone with ripple bedding, and mudstone. The incised valley fi lling deposits are characterized by a strong heterogeneity and the main hydrocarbon migration pathway is the medium-fi ne sandstone interval. Songliao Basin, Fulaerji Oilfield, Yaojia Formation, incised valley filling, migration Key words: pathway system pathway system for long-distance hydrocarbon migration, 1 Introduction incised valley fi lling deposits have not yet received adequate Migration pathway systems are an important link between attention. source rocks and traps, and they are generally composed of As sea level fell, fluvial depositional systems spread faults, unconformities, and permeable skeleton sandbodies towards the basin and eroded the underlying strata, thus (Ghisetti and Vezzani, 2000; Nie et al, 2001; Chen and formed incised valleys (Van Wagoner et al, 1990; Ghinassi, Kinzelbach, 2002; Hao et al, 2000). Previous research 2007; Wescott, 1997). A great deal of research has been including litho-geochemistry (Lynch, 1996; Chowdhury carried out on the formation and filling of incised valleys, and Noble, 1996), isotope geochemistry (Worden et al, which were controlled by relative change of sea level. 1999), fluid inclusion analysis (Kelly et al, 2000), and Incised valleys formed during the early-middle period of sea basin modeling methods (Hindle, 1997; Welte et al, 2001) level falling, and were gradually filled when sea level rose focused on the main migration pathways of basin fluids, (Ferguson and Davis, 2003; Paola et al, 1992; Zaitlin et al, especially those of hydrocarbon. However, as an important 1994; Allen and Posamentier, 1993; Zhang and Li, 1995; Li and Zhang, 1996). Research about incised valleys controlling hydrocarbon accumulation mainly focused on the control of *Corresponding author. email: xinrenchen@163.com lowstand lithologic traps (Sui et al, 2005; Xian et al, 2001; Received October 24, 2008 Pet.Sci.(2009)6:230-238 231 231 Huang et al, 2007). Whether traps without an effective large in scale and its petroleum reserve is 1,575×10 kg. The hydrocarbon source can form oil and gas fields depends on structural map of the top surface of the oil-bearing intervals the existence of a migration pathway system that links the indicates a slope inclining from west to east with a structural effective hydrocarbon source and the traps, and incised valley angle of 1.192°, and the structural lines are parallel with one filling deposits are a most important migration pathway another in the south-north direction. Faults are not developed system. The Fulaerji Oilfield of Songliao Basin is a typical in the oilfi eld and subtle nose-structures are developed in local reservoir formed by long-distance hydrocarbon migration areas. Effective hydrocarbon sources are scarce in the western through an incised valley fi lling deposit. slope area. The Qijia-Gulong Sag provided hydrocarbon for The Fulaerji Oilfi eld is located in the northern overlapping the Fulaerji Oilfi eld and the migration distance is longer than belt of the western slope area of the Songliao Basin. It is 80 km (Fig. 1). Study area Ⅳ Qiqihar I 2 Fulaerji F718 Oilfield J62 J55 Min. lake J53 strandline of SQ y1 J41 D82 J38 J39 J34 D72 I1 P2 D62 0 10 20 30km Taikang D65 D12 D71 Max. lake strandline D412 of SQ qn3 P1 Ⅱ2 Ⅱ1 12 D71 Active source kitchen Tailai 5 6 Fig. 1 Tectonic setting of the study area and distribution of the Fulaerji Oilfi eld and effective hydrocarbon sources : Western Clinoform; 1: Tailai Overlap Zone; 2: Taikang Mole-track; : Central Depression; 1: Longhupao Terrace; 2: Ⅰ Ⅰ Ⅰ Ⅱ Ⅱ Ⅱ Qijia Sag; Ⅲ: Northern Clinoform; Ⅳ: Northeastern Uplift; Ⅴ: Southeastern Uplift; Ⅵ: Southwestern Uplift; 1: city or town; 2: well mentioned in the paper; 3: well site; 4: boundary of the basin; 5: Ro≥0.7%, active source kitchen; 6: borderlines of second- order structural unit; 7: borderlines of third-order structural unit; A: migration pathway recognized by Fu et al (2007); B: migration pathway recognized by Xiang et al (2004) Much attention has been paid to the pathway system for different (Fig. 1). Based on detailed analysis of over 300 long-distance hydrocarbon migration of the Fulaerji Oilfi eld drilling wells by using sedimentology and petroleum geology for a long time. Xiang et al (2004) and Fu et al (2007) methods, it is concluded that incised valley fi lling deposits are both proposed that structural ridges were the hydrocarbon the hydrocarbon migration pathway of the Fulaerji Oilfi eld, migration pathway system of the Fulaerji Oilfield, but the and the sedimentary facies linkage and architecture of the locations of the migration pathways determined by them were incised valley pathway system were also discussed in depth. 232 Pet.Sci.(2009)6:230-238 led to a large-scale lowering of the lake level in the Songliao 2 Formation and fi lling of the incised valley Basin and a decrease in the lake area, as shown in Fig. 2 (Gao in the north of western slope and Cai, 1997; Xin et al, 2004; Xin and Wang, 2004). In the A great deal of research indicates that during the depositional period of Member 1 of Yaojia Formation, the deposition of the Qingshankou and Nenjiang Formations, smallest lake area was less than 10,000 km (Gao and Cai, large-scale transgression occurred twice in the Songliao Basin 1997), and the second-order sequence boundary between the (Gao and Xiao, 1995; Ye and Wei, 1996; Wei et al, 1996; Cretaceous SSQ and SSQ was formed. This sequence q-qn y-n Gao and Cai, 1997), which made the Songliao Basin develop boundary showed obvious characteristics in seismic, logging, into a deep-water depressional lacustrine basin. During this lithologic and paleontological data (Gao and Xiao, 1995; Wei period, the lake was characterized by two periods of rising et al, 1996; Gao and Cai, 1997; Xin et al, 2004; Gao et al, level and one of falling level and the lake area changed 1994; Ye et al, 2002; Liu et al, 2002; Wei, 1996; Wang et al, greatly. In the early depositional period of the Qingshankou 2005). During the depositional period of Members 2 and 3 of Formation, the lake area was about 90,000 km . During the Yaojia Formation, the lacustrine basin expanded again. In the late depositional period of the Qingshankou Formation and the early depositional period of the Yaojia Formation, local early depositional period of the Nenjiang Formation, the lake tectonism uplifted the Songliao Basin and the global sea level level of the basin reached its second peak and the lake area fell greatly in the upper Cretaceous (Haq et al, 1987), which was over 120,000 km . Fig. 2 The sequence stratigraphic framework from the Qingshankou Formation to the Member 1 of Nenjiang Formation of the central Songliao Basin A: coarse sandstone; B: medium sandstone; C: fi ne sandstone; D: siltstone; E: muddy sandstone; F: mudstone; G: muddy siltstone; H: silt mudstone; I: Ostracoda layer; J: oil shale; 0: light grey; 8: dark green; 12: black; 13: dark grey; 14: grey; 15: dark purple Pet.Sci.(2009)6:230-238 233 From Member 1 of Qingshankou Formation to Member The planar distribution map of the expanding system tract of 1 of Nenjiang Formation, the strata were divided into seven sequence SQ was compiled based on the data of over 300 y23 third-order sequences and two second-order sequences drilling wells, which indicated the spatial distribution of the according to detailed analysis of paleontological, lithologic, incised valley fi lling depositional system (Fig. 3). logging and seismic data. Sequences SQ , SQ , SQ , q4-qn1 qn2 qn3 and SQ belonged to the second-order sequence SSQ , and qn4 q-qn 0 10 20 30km SQ , SQ , and SQ belonged to the second-order sequence y1 y23 n1 SSQ (Fig. 2). y-n N During the depositional period from late Qingshankou Formation to early Yaojia Formation, the lake shrank and Qiqihar the shoreline of the western slope area shifted towards the central sag area on a large scale (Fig. 1). Most of the western F718 slope area was exposed, which led to cessation of deposition. J62 Compared with the complete stratigraphic sequences of the J55 J53 Songliao Basin (Fig. 2), the third-order sequences SQ and qn4 D82 J41 J38 SQ were not developed in most of the western slope area y1 J39 D72 J34 (Fig. 5). D62 During the depositional period from the Qingshankou D65 D12 Formation to the Yaojia Formation, the Qiqihar stream system was well developed in the western slope of the Songliao D71 Basin (Gao and Cai, 1997). During the depositional period from late Qingshankou Formation to early Yaojia Formation D412 (from SQ to SQ ), an incised valley was formed in the qn4 y1 western slope area due to the infl uence of the Qiqihar stream system. Its length was 70 km and width was 20 km, and extended in the NW-SE direction. The filling of the incised D71 valley mainly occurred in the expanding system tract of the Tailai third-order sequence SQ . 3 4 y23 AB C D E F 3 Linkage of the depositional system related to incised valley fi lling Fig. 3 Depositional system of EST in the north of the western slope of the y23 Songliao Basin The complete depositional system linkage related to 1: city or town; 2: key well; 3: drilling well; 4: pinchout line; A: mud and incised valley filling is delta—incised valley filling— sand mixture beach of shore-shallow lacustrine; B: relic erosion highland; C: shoreline sandy beach bar. sand beach of shore-shallow lacustrine; D: incised valley fi lling; E: mouth bar of delta front; F: distal bar of delta front The incised valley was gradually fi lled during the rising of lake (sea) level. In the lower lake (sea) level period, the incised valley, as the transport passage for sands, transported During the early period of expanding system tract of a great deal of clasts to the deep-water area, which led to the SQ (EST ), the incised valley, as a passage for sand y23 y23 development of sublacustrine fan or delta deposits, later it transportation, carried large quantities of clasts to the deep lake was mainly dominated by delta deposits. During the period of basin area southeast of Well D71 and formed a sand-rich delta rising lake levels, the incised valley was gradually drowned, depositional system along the area from Well D71 to Well and a lot of riverine sediments deposited. The incised valley D412. In the rising lake level stage of SQ , the incised valley y23 was gradually filled due to river-lake (sea) interaction in was gradually drowned by lake water. The river carrying clasts the incised valley. In the maximum lake (sea) level stage, was influenced by lake water, and the clasts deposited and the shoreline reached the top of the incised valley in the fi lled the incised valley in the river-lake interaction area. The adjacent provenance area. The clasts from the provenance incised valley fi lling deposit with length of 70 km and width area were mainly infl uenced by lake (sea) waves and formed of 20 km was formed along the area from Well J55 to D71. shore-shallow lacustrine (marine) sandy beach bar deposits In the incised valley filling system, a relic erosion highland near the shoreline. The linkages of the incised valley fi lling was developed near Well J53 whose sediments were mainly depositional system are as follows: towards the central mudstones depositing from suspended load. When the lake basin, the incised valley fi lling deposit is connected with the level rose to the maximum, the shoreline reached the top of delta developed in the early period, and towards the basin the incised valley in the adjacent provenance area. Clasts margin, the incised valley filling deposit is connected with coming from the provenance area were mainly controlled by the shore-shallow lacustrine sandy beach bar developed in the the lake waves and formed sand-rich sandy beach bar deposits maximum fl ooding period. in shore-shallow lacustrine areas. The Cretaceous incised valley filling in the north of the The delta depositional system, incised valley filling western slope of the Songliao Basin mainly occurred during depositional system, and shore sandy beach bar in the the expanding system tract of the third-order sequence SQ . depositional system linkage related to incised valley filling y23 234 Pet.Sci.(2009)6:230-238 are all characterized by the development of sandstones and D412 and Well D71 in the dip direction profile. Sequences a high sand content, generally over 40% (Fig. 4). The sand of Well D412 below the slope break are complete, while content of sandy shore beach bar is usually over 60% and sequences SQ and SQ are not developed above the slope qn4 y1 in local areas over 80%. Sandstone layers with sand content break. Erosion and incision occurred above the slope break higher than 60% which means relatively high porosity and during the deposition of sequences SQ and SQ , and the qn4 y1 permeability are favorable for hydrocarbon migration and incised valley was formed. Incised valley filling occurred accumulation. during the expanding system tract of sequence SQ and y23 formed incised valley fi lling deposits which could be divided into fi ve short-term cycles (A, B, C, D, and E in Fig. 5). The incised valley fi lling sand bodies formed during the 0 20 30km initial short-term cycle (A in Fig. 5) were developed along the area from Well D71 to D412, and had an erosion contact with the underlying delta sand bodies of highstand system tract of sequence SQ . Sand bodies adjacent to the Well D71 slope Qiqihar y1 break had the largest thickness, and overlapped and pinched out in the up-dip direction to the east of Well D65, while F718 gradually thinning towards the basin. The sand bodies were J5 5 J6 2 covered by muddy intervals which thinned and pinched out J5 3 towards the basin margin. D82 J4 1 J38 The incised valley filling sand bodies formed during J3 9 D72 J3 4 D62 the second short-term cycle (B in Fig. 5) were developed along the area from Well D65 to D412. The sand bodies D65 D12 were characterized by stable thickness and directly covered the sand bodies of the first short-term cycle to the west of D71 Well D71. In the up-dip direction of slope, the sand bodies overlapped and pinched out to the east of Well D62 and were D412 covered by muddy intervals which thinned and pinched out towards the basin margin. The incised valley fi lling sand bodies formed during the third short-term cycle (C in Fig. 5) were developed on the D71 2 slope along the area from Well D62 to D65 and in the deeply Tailai 3 4 incised valley adjacent to Well J41. Sand bodies in the former area directly covered the sand bodies of the second short- AB D E term cycle to the west of Well D65, overlapped and pinched out in the up-dip direction of the slope to the east of Well J39, Fig. 4 Sandstone percentage of EST in the north of the western y23 and split and pinched out towards the basin. The sand bodies slope of the Songliao Basin 1: city or town; 2: key well; 3: drilling well; 4: pinchout line were covered by muddy intervals which thinned and pinched percentage of sandstones A: 0%-20%; B: 20%-40%; C: 40%-60%; out towards the basin margin. The deeply incised valley sand D: 60%-80%; E: 80%-100% bodies adjacent to Well J41 were sand lenses and directly contacted with the sand bodies of the short-term cycles in later periods. 4 Architecture of the incised valley filling The incised valley fi lling sand bodies formed during the fourth short-term cycle (D in Fig. 5) were developed along depositional system and hydrocarbon the area from Well J41 to D62. Sand bodies near the Well migration and accumulation J39 had the largest thickness, and directly covered the sand bodies of the third short-term cycle to the west of Well D62. The incised valley filling depositional system is The sand bodies overlapped and pinched out in the up-dip characterized by its multi-cycle architecture. In the dip profi le direction of the slope to the east of Well J55, and thinned and of incised valley, tracing the source from the slope break, pinched out towards the basin. The sand bodies were covered sand bodies overlap layer by layer along the bottom surface by muddy intervals which thinned and pinched out towards of the incised valley, and split and pinch out into mudstones the basin margin. towards the basin. The sandstones, which overlap along the The fi fth short-term cycle was developed during the period bottom surface of incised valley whose slope gradient is a of maximum lake level. Shore-shallow sandy beach bar sand little more than 8.5 m/km nowadays, are transport layers for bodies were formed near the maximum lake shoreline along hydrocarbon migration and accumulation. the area from Well F718 to J55 (E in Fig. 5) and directly Fig. 5 is the cross section in the dip direction of the covered the sand bodies of the fourth short-term cycle to the incised valley (the location of the section is shown as P1 in west of Well J41. The sandstones were developed with stable Fig. 1) and in the strike direction of the incised valley (the thickness along the area from Well F718 to J55, quickly location of the section is shown as P2 in Fig. 1). pinched out towards the basin, changed into lacustrine Obvious slope breaks appeared in the area between Well F718 J55 J3 9 D6 5 D7 1 D 62 R0.5 R0.5 L Ls(Ω m) LLs(Ω m) D412 mv) R0.5(Ωm) SP( R0.5(Ωm) R0.5 (Ω m) S P (mv) L Ld (Ω m) m) SP(mv) LLd (Ω SP(mv) R0.5(Ωm) -10 10 20 0 10 -40 40 10 -20 20 020 1 1 10 -20 20 SQ n1 SQ y23 SQ y1 SQ qn4 SQ qn3 SP SP SP(mv) (mv)(Ωm)(mv)(Ωm) -20 0 100 10 20 0 10 50 40 0 10 05 10 15km Pet.Sci.(2009)6:230-238 235 J41 12 3 8 9 Fig. 5 Cross section in the dip direction and in the strike direction of incised valley (the position of the section is shown as P1 and P2 in Fig. 1) nd rd 1: 2 sequence boundary; 2: 3 sequence boundary; 3: lithologic surface; 4: maximum fl ooding surface of lake; 5: mudstone; 6: muddy siltstone; 7: siltstone; 8: medium-fi ne sandstone; 9: oil transport direction mudstones, and were covered by mudstones. Songliao Basin. They are distributed in a “string of beads” In the strike profile, the sand bodies are present lens shape and the hydrocarbon transport is probably also related shaped with staggered overlap, the early sand bodies were to the accumulation system of the incised valley filling developed at relatively lower levels in the valley, such as near depositional system. the Well J41 and near the Well J62 in Fig. 6, while the higher Incised valley fi lling depositional system is characterized levels in the valley are dominated by mudstones, such as near by the multi-stage fi lling of sandstones and mudstones. The the Well J53 in Fig. 5, and the later sand bodies were not lower part of incised valley filling depositional system is limited by the bottom of the valley. In the period of maximum dominated by sandstones and has lower content of mudstones, lake level of SQ , the incised valley is filled mainly by while there is a higher content of mudstones and lower y23 muddy sediments (Fig. 5). content of sandstones in the upper part. Incised valley fi lling A complete hydrocarbon accumulation system was formed deposits have different hydrocarbon transport capability due by the depositional system linkage related to incised valley to their different lithology which is shown as the obvious fi lling as follows: deltaic sand bodies collected and pumped heterogeneity. Medium-fi ne sandstones with higher porosity hydrocarbon from the active source, incised valley filling and permeability are the main transport layers and constitute depositional system completed the long-distance hydrocarbon the dominant migration passages (Fig. 6). migration, and lithological traps of shore-shallow lacustrine The core data of Well D71 indicate two short-term fi lling sandy beach bar accumulated hydrocarbon. Besides, other cycles of the incised valley and the oil-bearing properties traps in this hydrocarbon accumulation system can also form of different lithological intervals, which clearly reflect the reservoirs. Oil and gas fields including Talahong Gasfield, main intervals for hydrocarbon transport (Fig. 6). The lower Baiyinnuole Gasfi eld, Erzhan Gasfi eld, Alaxin Gasfi eld, and part is a complete short-term cycle with an erosion surface Jiangqiao Oilfi eld were discovered in the western slope of the as its bottom boundary. Above the erosion surface, the 02 4 6km J34 J53 J62 J38 SP(mv)R0.5(Ωm) SP(mv) SP(mv) SP(mv)R05( . Ωm)SP(mv) R0.5(Ωm) R0.5(Ωm) 0 40 -10+1 0 0 20 10 20 010 -10 +1 0 0 20 -10 +10 SQ n1 SQ y23 SQ qn3 -10 -20 236 Pet.Sci.(2009)6:230-238 Porosity Permeability -3 2 Lithologic columnar of core % ×10 μm 10 20 30 1 100 MTL -6.5 6.5 MTL MTL 6.0 -6.5 1 -6.5 6.0 1 2 3 4 56 7 81 9 0 11 12 Fig. 6 Core data of the incised valley fi lling of Well D71 (the well location is shown in Fig. 1) 1: mudstones; 2: silty mudstones; 3: fine sandstones; 4: medium sandstones; 5: fine sandstones with muddy pebbles; 6: medium sandstones with muddy pebbles; 7: pebbly medium sandstones; 8: mud-gravel stone; 9: scour surface; 10: oil-rich layer; 11: oil-soaked layer; 12: oil spot layer; Color code: 0 white; 5 green; 6 grey; + dark color; - light color; MTL: main transport layer depositional sequences are as follows: (1) 30 cm thick light with development of wavy cross-bedding with muddy bands gray green muddy conglomerates with no oil or gas shows; and with no oil or gas shows; (12) 10 cm thick gray green (2) 10 cm thick light gray white medium sandstones with no silty mudstones with sandy bands, with development of wavy oil or gas shows; (3) 1.5 m thick gray white fi ne sandstones bedding and with no oil or gas shows; (13) 1 m thick gray with development of wavy cross-bedding, muddy pebbles, green silty mudstones with no oil or gas shows. calcareous nodule and with no oil or gas shows; (4) 30 cm The upper short-term fi lling cycle was an incomplete one, thick gray white conglomerate-bearing medium sandstones which indicated the erosion of the bottom part, and above the with no oil or gas shows; (5) oil-soaked layer, 1.7 m thick erosional surface, muddy conglomerates and petroliferous gray white medium sandstones with development of low- fi ne-grained sandstones with cross-bedding were respectively angle cross-bedding and muddy pebbles; (6) 10 cm thick developed. gray white medium sandstones with development of muddy The results indicate that incised valley filling deposits pebbles and pyrite and with no oil or gas shows; (7) 25 are characterized by obvious heterogeneity. The medium cm thick gray white fine sandstones with development of sandstones of (5), (8), and (9) of the lower short-term cycle wavy cross-bedding and low-angle cross-bedding and with are the main transport layers for hydrocarbon migration. The no oil or gas shows; (8) oil-soaked layer, 25 cm thick gray thickness of the transport layers is about 2.05 m, and that of white medium sandstones with development of wavy cross- the lower short-term cycle is a little more than 6 m, so the bedding, muddy pebbles, carbonaceous clasts, and pyrite; (9) transport layers account for about 33% of the lower short- oil-soaked layer, 10 cm thick gray white medium sandstones term cycle of incised valley fi lling. with development of wavy bedding, and carbonaceous clasts; (10) 10 cm thick gray white medium sandstones with thin- 5 Conclusions layer mudstones interbedded, wavy bedding and with no oil or gas shows; (11) 10 cm thick gray white fine sandstones 1) The hydrocarbon of the Fulaerji Oilfi eld is derived from SQ qn2 Depth, m Color Layer number Cycle Sequence SQ y23 Pet.Sci.(2009)6:230-238 237 13(7): 837-846 the Qijia-Gulong Sag (Feng et al, 2003) and the hydrocarbon Dem bicki H and Anderson M J. Secondary migration of oil: experiments migration distance is over 80 km. This study clarified supporting effi cient movement of separate, buoyant oil phase along that incised valley filling deposits were the hydrocarbon limited conduits. AAPG Bulletin. 1989. 73(8): 1018-1021 transport layer systems, and the structural ridge passages for Fen g Z H, Liao G Z, Fang W, et al. Formation of heavy oil and hydrocarbon migration proposed by Xiang et al (2004) were correlation of oil-source in the western slope of the northern situated in the incised valley fi lling deposits. Songliao Basin. Petroleum Exploration and Development. 2003. 2) Towards the basin, incised valley fi lling deposits joined 30(4): 25-28 (in Chinese) with the delta formed in the early period, while towards the Fer guson T W and Davis R A. Post-Miocene stratigraphy and basin margin, they joined with the shore-shallow lacustrine depositional environments of valley-fill sequences at the mouth of beach bar sandbodies developed during the maximum lake Tampa Bay, Florida. Marine Geology. 2003. 200(1): 157-170 level in the basin margin area. Consequently, a complete Fu X F , Wang P Y, Lü Y F, et al. Tectonic features and control of oil-gas accumulation in the west slope of Songliao Basin. Chinese Journal of sedimentary system is formed, i.e., delta system—incised Geology. 2007. 42(2): 209-222 (in Chinese) valley fi lling system—shore facies sandy beach bar system, Gao R Q and Cai X Y. The Formation Conditions and Distribution Rules which are all characterized by the development of sandstones of Oil and Gas Pools of Songliao Basin. Beijing: Petroleum Industry with high sand content, high porosity, and high permeability. 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The effects of differential subsidence and coastal topography on high-order transgressive-regressive cycles: Pliocene incised valley, and split and pinch out into mudstones towards nearshore deposits of the Val d’Orcia Basin, Northern Apennines, the basin. The sandstones, which overlap along the bottom Italy. Sedimentary Geology. 2007. 202(4): 677-701 surface of incised valley, are transport layers for hydrocarbon Ghi setti F and Vezzani L. Detachments and normal faulting in the migration and accumulation. A complete hydrocarbon Marche fold-and-thrust belt (central Apennines, Italy): inferences on accumulation system was formed by the depositional system fl uid migration paths. Journal of Geodynamics. 2000. 29(3-5): 345- linkage related to incised valley filling as follows: deltaic sand bodies collected and pumped hydrocarbon from the Hao F, Zou H Y and Jiang J Q. Dynamics of petroleum accumulation and active source, incised valley filling depositional system its advances. 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Medium-fi ne sandstones Acta Sedimentologica Sinica. 2007. 25(3): 386-391 (in Chinese) with higher porosity and permeability are the main transport Kel ly J, Parnell J and Chen H H. Application of fluid inclusions to layers and constitute the dominant migration passages. The studies of fractured sandstone reservoirs. Journal of Geochemical actual transport layers account for about 33% of the lower Exploration. 2000. 69-70: 705-709 short-term cycles of incised valley filling deposits based on Li C X and Zhang G J. Progress on high resolution sequence stratigraphy the core data of Well D71. Dembicki and Anderson (1989), in incised paleovalley. Advance in Earth Sciences. 1996. 11(2): 216- Thomas and Clouse (1995) and Xin et al (2002) carried out 219 (in Chinese) experiments about hydrocarbon migration and obtained Liu Z J, Dong Q S, Wang S M, et al. Introduction and Application of Continental Sequence Stratigraphy. 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Geochimica et of incised valley systems associated with relative sea-level changes. Cosmochimica Acta. 1999. 63(17): 2513-2528 In: Incised Valley Systems: Origin and Sedimentary Sequence Xia n B Z, Jiang Z X, Cao Y C, et al. Discovery of incised valley in (edited by Dalrymple R W, Boyd R and Zaitlin B A). SEPM Special southeast of Biyang Depression and its significance. Oil & Gas Publication. 1994. 51: 45-60 Geology. 2001. 22(4): 304-308 (in Chinese) Zha ng G J and Li C X. The infilling of the incised Qiantang River Xia ng C F, Xia B, Xie X N, et al. Major hydrocarbon migration pathway paleovalley and its sequence stratigraphic characteristics. Marine system in western slope zone of Songliao Basin. Oil & Gas Geology. Geology & Quaternary Geology. 1995. 15(4): 57-67 (in Chinese) (Edited by Hao Jie) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Petroleum Science Springer Journals

Incised valley filling deposits: an important pathway system for long-distance hydrocarbon migration—a case study of the Fulaerji Oilfield in the Songliao Basin

Petroleum Science , Volume 6 (3) – Jul 23, 2009

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Springer Journals
Copyright
Copyright © 2009 by China University of Petroleum (Beijing) and Springer-Verlag GmbH
Subject
Earth Sciences; Mineral Resources; Industrial Chemistry/Chemical Engineering; Industrial and Production Engineering; Energy Economics
ISSN
1672-5107
eISSN
1995-8226
DOI
10.1007/s12182-009-0037-5
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See Article on Publisher Site

Abstract

for long-distance hydrocarbon migration, are discussed in detail based on core and logging data. The sequence SQ of the Cretaceous Yaojia Formation is the main hydrocarbon-bearing layer in the Fulaerji y23 Oilfield. The hydrocarbon source of the oilfield is the Qijia-Gulong Sag which is about 80 km away from the Fulaerji Oilfi eld. The transport layer of long-distance hydrocarbon migration is the overlapped sandstone complex which fi lls the incised valley. The incised valley developed during the depositional period from the late Qingshankou Formation to the early Yaojia Formation of Cretaceous (SQ -SQ ) qn4 y1 was about 70 km long and 20 km wide, and extended in the NW-SE direction. The overlapped filling of the incised valley mainly occurred in the expanding system tract of the third-order sequence SQ (EST ). y23 y23 Towards the basin, incised valley fi lling deposits overlapped on the delta developed in the early period, and towards the basin margin, incised valley fi lling deposits were covered by the shore-shallow lacustrine sandy beach bar developed in the maximum fl ooding period. All of the delta, the incised valley fi lling and the shore-shallow sandy beach bar are sandstone-rich, and have high porosity and permeability, and can form an effective hydrocarbon migration and accumulation system. Deltaic sand bodies collected and pumped hydrocarbon from the active source, incised valley filling depositional system completed the long-distance hydrocarbon migration, and lithological traps of shore-shallow lacustrine sandy beach bar accumulated hydrocarbon. The incised valley fi lling sequences are multi-cycle: an integrated short- term filling cycle was developed on the erosion surface, and the sequences upward were mud-gravel stone, medium-fi ne sandstone containing terrigenous gravels and muddy pebbles with cross bedding, silty mudstone with ripple bedding, and mudstone. The incised valley fi lling deposits are characterized by a strong heterogeneity and the main hydrocarbon migration pathway is the medium-fi ne sandstone interval. Songliao Basin, Fulaerji Oilfield, Yaojia Formation, incised valley filling, migration Key words: pathway system pathway system for long-distance hydrocarbon migration, 1 Introduction incised valley fi lling deposits have not yet received adequate Migration pathway systems are an important link between attention. source rocks and traps, and they are generally composed of As sea level fell, fluvial depositional systems spread faults, unconformities, and permeable skeleton sandbodies towards the basin and eroded the underlying strata, thus (Ghisetti and Vezzani, 2000; Nie et al, 2001; Chen and formed incised valleys (Van Wagoner et al, 1990; Ghinassi, Kinzelbach, 2002; Hao et al, 2000). Previous research 2007; Wescott, 1997). A great deal of research has been including litho-geochemistry (Lynch, 1996; Chowdhury carried out on the formation and filling of incised valleys, and Noble, 1996), isotope geochemistry (Worden et al, which were controlled by relative change of sea level. 1999), fluid inclusion analysis (Kelly et al, 2000), and Incised valleys formed during the early-middle period of sea basin modeling methods (Hindle, 1997; Welte et al, 2001) level falling, and were gradually filled when sea level rose focused on the main migration pathways of basin fluids, (Ferguson and Davis, 2003; Paola et al, 1992; Zaitlin et al, especially those of hydrocarbon. However, as an important 1994; Allen and Posamentier, 1993; Zhang and Li, 1995; Li and Zhang, 1996). Research about incised valleys controlling hydrocarbon accumulation mainly focused on the control of *Corresponding author. email: xinrenchen@163.com lowstand lithologic traps (Sui et al, 2005; Xian et al, 2001; Received October 24, 2008 Pet.Sci.(2009)6:230-238 231 231 Huang et al, 2007). Whether traps without an effective large in scale and its petroleum reserve is 1,575×10 kg. The hydrocarbon source can form oil and gas fields depends on structural map of the top surface of the oil-bearing intervals the existence of a migration pathway system that links the indicates a slope inclining from west to east with a structural effective hydrocarbon source and the traps, and incised valley angle of 1.192°, and the structural lines are parallel with one filling deposits are a most important migration pathway another in the south-north direction. Faults are not developed system. The Fulaerji Oilfield of Songliao Basin is a typical in the oilfi eld and subtle nose-structures are developed in local reservoir formed by long-distance hydrocarbon migration areas. Effective hydrocarbon sources are scarce in the western through an incised valley fi lling deposit. slope area. The Qijia-Gulong Sag provided hydrocarbon for The Fulaerji Oilfi eld is located in the northern overlapping the Fulaerji Oilfi eld and the migration distance is longer than belt of the western slope area of the Songliao Basin. It is 80 km (Fig. 1). Study area Ⅳ Qiqihar I 2 Fulaerji F718 Oilfield J62 J55 Min. lake J53 strandline of SQ y1 J41 D82 J38 J39 J34 D72 I1 P2 D62 0 10 20 30km Taikang D65 D12 D71 Max. lake strandline D412 of SQ qn3 P1 Ⅱ2 Ⅱ1 12 D71 Active source kitchen Tailai 5 6 Fig. 1 Tectonic setting of the study area and distribution of the Fulaerji Oilfi eld and effective hydrocarbon sources : Western Clinoform; 1: Tailai Overlap Zone; 2: Taikang Mole-track; : Central Depression; 1: Longhupao Terrace; 2: Ⅰ Ⅰ Ⅰ Ⅱ Ⅱ Ⅱ Qijia Sag; Ⅲ: Northern Clinoform; Ⅳ: Northeastern Uplift; Ⅴ: Southeastern Uplift; Ⅵ: Southwestern Uplift; 1: city or town; 2: well mentioned in the paper; 3: well site; 4: boundary of the basin; 5: Ro≥0.7%, active source kitchen; 6: borderlines of second- order structural unit; 7: borderlines of third-order structural unit; A: migration pathway recognized by Fu et al (2007); B: migration pathway recognized by Xiang et al (2004) Much attention has been paid to the pathway system for different (Fig. 1). Based on detailed analysis of over 300 long-distance hydrocarbon migration of the Fulaerji Oilfi eld drilling wells by using sedimentology and petroleum geology for a long time. Xiang et al (2004) and Fu et al (2007) methods, it is concluded that incised valley fi lling deposits are both proposed that structural ridges were the hydrocarbon the hydrocarbon migration pathway of the Fulaerji Oilfi eld, migration pathway system of the Fulaerji Oilfield, but the and the sedimentary facies linkage and architecture of the locations of the migration pathways determined by them were incised valley pathway system were also discussed in depth. 232 Pet.Sci.(2009)6:230-238 led to a large-scale lowering of the lake level in the Songliao 2 Formation and fi lling of the incised valley Basin and a decrease in the lake area, as shown in Fig. 2 (Gao in the north of western slope and Cai, 1997; Xin et al, 2004; Xin and Wang, 2004). In the A great deal of research indicates that during the depositional period of Member 1 of Yaojia Formation, the deposition of the Qingshankou and Nenjiang Formations, smallest lake area was less than 10,000 km (Gao and Cai, large-scale transgression occurred twice in the Songliao Basin 1997), and the second-order sequence boundary between the (Gao and Xiao, 1995; Ye and Wei, 1996; Wei et al, 1996; Cretaceous SSQ and SSQ was formed. This sequence q-qn y-n Gao and Cai, 1997), which made the Songliao Basin develop boundary showed obvious characteristics in seismic, logging, into a deep-water depressional lacustrine basin. During this lithologic and paleontological data (Gao and Xiao, 1995; Wei period, the lake was characterized by two periods of rising et al, 1996; Gao and Cai, 1997; Xin et al, 2004; Gao et al, level and one of falling level and the lake area changed 1994; Ye et al, 2002; Liu et al, 2002; Wei, 1996; Wang et al, greatly. In the early depositional period of the Qingshankou 2005). During the depositional period of Members 2 and 3 of Formation, the lake area was about 90,000 km . During the Yaojia Formation, the lacustrine basin expanded again. In the late depositional period of the Qingshankou Formation and the early depositional period of the Yaojia Formation, local early depositional period of the Nenjiang Formation, the lake tectonism uplifted the Songliao Basin and the global sea level level of the basin reached its second peak and the lake area fell greatly in the upper Cretaceous (Haq et al, 1987), which was over 120,000 km . Fig. 2 The sequence stratigraphic framework from the Qingshankou Formation to the Member 1 of Nenjiang Formation of the central Songliao Basin A: coarse sandstone; B: medium sandstone; C: fi ne sandstone; D: siltstone; E: muddy sandstone; F: mudstone; G: muddy siltstone; H: silt mudstone; I: Ostracoda layer; J: oil shale; 0: light grey; 8: dark green; 12: black; 13: dark grey; 14: grey; 15: dark purple Pet.Sci.(2009)6:230-238 233 From Member 1 of Qingshankou Formation to Member The planar distribution map of the expanding system tract of 1 of Nenjiang Formation, the strata were divided into seven sequence SQ was compiled based on the data of over 300 y23 third-order sequences and two second-order sequences drilling wells, which indicated the spatial distribution of the according to detailed analysis of paleontological, lithologic, incised valley fi lling depositional system (Fig. 3). logging and seismic data. Sequences SQ , SQ , SQ , q4-qn1 qn2 qn3 and SQ belonged to the second-order sequence SSQ , and qn4 q-qn 0 10 20 30km SQ , SQ , and SQ belonged to the second-order sequence y1 y23 n1 SSQ (Fig. 2). y-n N During the depositional period from late Qingshankou Formation to early Yaojia Formation, the lake shrank and Qiqihar the shoreline of the western slope area shifted towards the central sag area on a large scale (Fig. 1). Most of the western F718 slope area was exposed, which led to cessation of deposition. J62 Compared with the complete stratigraphic sequences of the J55 J53 Songliao Basin (Fig. 2), the third-order sequences SQ and qn4 D82 J41 J38 SQ were not developed in most of the western slope area y1 J39 D72 J34 (Fig. 5). D62 During the depositional period from the Qingshankou D65 D12 Formation to the Yaojia Formation, the Qiqihar stream system was well developed in the western slope of the Songliao D71 Basin (Gao and Cai, 1997). During the depositional period from late Qingshankou Formation to early Yaojia Formation D412 (from SQ to SQ ), an incised valley was formed in the qn4 y1 western slope area due to the infl uence of the Qiqihar stream system. Its length was 70 km and width was 20 km, and extended in the NW-SE direction. The filling of the incised D71 valley mainly occurred in the expanding system tract of the Tailai third-order sequence SQ . 3 4 y23 AB C D E F 3 Linkage of the depositional system related to incised valley fi lling Fig. 3 Depositional system of EST in the north of the western slope of the y23 Songliao Basin The complete depositional system linkage related to 1: city or town; 2: key well; 3: drilling well; 4: pinchout line; A: mud and incised valley filling is delta—incised valley filling— sand mixture beach of shore-shallow lacustrine; B: relic erosion highland; C: shoreline sandy beach bar. sand beach of shore-shallow lacustrine; D: incised valley fi lling; E: mouth bar of delta front; F: distal bar of delta front The incised valley was gradually fi lled during the rising of lake (sea) level. In the lower lake (sea) level period, the incised valley, as the transport passage for sands, transported During the early period of expanding system tract of a great deal of clasts to the deep-water area, which led to the SQ (EST ), the incised valley, as a passage for sand y23 y23 development of sublacustrine fan or delta deposits, later it transportation, carried large quantities of clasts to the deep lake was mainly dominated by delta deposits. During the period of basin area southeast of Well D71 and formed a sand-rich delta rising lake levels, the incised valley was gradually drowned, depositional system along the area from Well D71 to Well and a lot of riverine sediments deposited. The incised valley D412. In the rising lake level stage of SQ , the incised valley y23 was gradually filled due to river-lake (sea) interaction in was gradually drowned by lake water. The river carrying clasts the incised valley. In the maximum lake (sea) level stage, was influenced by lake water, and the clasts deposited and the shoreline reached the top of the incised valley in the fi lled the incised valley in the river-lake interaction area. The adjacent provenance area. The clasts from the provenance incised valley fi lling deposit with length of 70 km and width area were mainly infl uenced by lake (sea) waves and formed of 20 km was formed along the area from Well J55 to D71. shore-shallow lacustrine (marine) sandy beach bar deposits In the incised valley filling system, a relic erosion highland near the shoreline. The linkages of the incised valley fi lling was developed near Well J53 whose sediments were mainly depositional system are as follows: towards the central mudstones depositing from suspended load. When the lake basin, the incised valley fi lling deposit is connected with the level rose to the maximum, the shoreline reached the top of delta developed in the early period, and towards the basin the incised valley in the adjacent provenance area. Clasts margin, the incised valley filling deposit is connected with coming from the provenance area were mainly controlled by the shore-shallow lacustrine sandy beach bar developed in the the lake waves and formed sand-rich sandy beach bar deposits maximum fl ooding period. in shore-shallow lacustrine areas. The Cretaceous incised valley filling in the north of the The delta depositional system, incised valley filling western slope of the Songliao Basin mainly occurred during depositional system, and shore sandy beach bar in the the expanding system tract of the third-order sequence SQ . depositional system linkage related to incised valley filling y23 234 Pet.Sci.(2009)6:230-238 are all characterized by the development of sandstones and D412 and Well D71 in the dip direction profile. Sequences a high sand content, generally over 40% (Fig. 4). The sand of Well D412 below the slope break are complete, while content of sandy shore beach bar is usually over 60% and sequences SQ and SQ are not developed above the slope qn4 y1 in local areas over 80%. Sandstone layers with sand content break. Erosion and incision occurred above the slope break higher than 60% which means relatively high porosity and during the deposition of sequences SQ and SQ , and the qn4 y1 permeability are favorable for hydrocarbon migration and incised valley was formed. Incised valley filling occurred accumulation. during the expanding system tract of sequence SQ and y23 formed incised valley fi lling deposits which could be divided into fi ve short-term cycles (A, B, C, D, and E in Fig. 5). The incised valley fi lling sand bodies formed during the 0 20 30km initial short-term cycle (A in Fig. 5) were developed along the area from Well D71 to D412, and had an erosion contact with the underlying delta sand bodies of highstand system tract of sequence SQ . Sand bodies adjacent to the Well D71 slope Qiqihar y1 break had the largest thickness, and overlapped and pinched out in the up-dip direction to the east of Well D65, while F718 gradually thinning towards the basin. The sand bodies were J5 5 J6 2 covered by muddy intervals which thinned and pinched out J5 3 towards the basin margin. D82 J4 1 J38 The incised valley filling sand bodies formed during J3 9 D72 J3 4 D62 the second short-term cycle (B in Fig. 5) were developed along the area from Well D65 to D412. The sand bodies D65 D12 were characterized by stable thickness and directly covered the sand bodies of the first short-term cycle to the west of D71 Well D71. In the up-dip direction of slope, the sand bodies overlapped and pinched out to the east of Well D62 and were D412 covered by muddy intervals which thinned and pinched out towards the basin margin. The incised valley fi lling sand bodies formed during the third short-term cycle (C in Fig. 5) were developed on the D71 2 slope along the area from Well D62 to D65 and in the deeply Tailai 3 4 incised valley adjacent to Well J41. Sand bodies in the former area directly covered the sand bodies of the second short- AB D E term cycle to the west of Well D65, overlapped and pinched out in the up-dip direction of the slope to the east of Well J39, Fig. 4 Sandstone percentage of EST in the north of the western y23 and split and pinched out towards the basin. The sand bodies slope of the Songliao Basin 1: city or town; 2: key well; 3: drilling well; 4: pinchout line were covered by muddy intervals which thinned and pinched percentage of sandstones A: 0%-20%; B: 20%-40%; C: 40%-60%; out towards the basin margin. The deeply incised valley sand D: 60%-80%; E: 80%-100% bodies adjacent to Well J41 were sand lenses and directly contacted with the sand bodies of the short-term cycles in later periods. 4 Architecture of the incised valley filling The incised valley fi lling sand bodies formed during the fourth short-term cycle (D in Fig. 5) were developed along depositional system and hydrocarbon the area from Well J41 to D62. Sand bodies near the Well migration and accumulation J39 had the largest thickness, and directly covered the sand bodies of the third short-term cycle to the west of Well D62. The incised valley filling depositional system is The sand bodies overlapped and pinched out in the up-dip characterized by its multi-cycle architecture. In the dip profi le direction of the slope to the east of Well J55, and thinned and of incised valley, tracing the source from the slope break, pinched out towards the basin. The sand bodies were covered sand bodies overlap layer by layer along the bottom surface by muddy intervals which thinned and pinched out towards of the incised valley, and split and pinch out into mudstones the basin margin. towards the basin. The sandstones, which overlap along the The fi fth short-term cycle was developed during the period bottom surface of incised valley whose slope gradient is a of maximum lake level. Shore-shallow sandy beach bar sand little more than 8.5 m/km nowadays, are transport layers for bodies were formed near the maximum lake shoreline along hydrocarbon migration and accumulation. the area from Well F718 to J55 (E in Fig. 5) and directly Fig. 5 is the cross section in the dip direction of the covered the sand bodies of the fourth short-term cycle to the incised valley (the location of the section is shown as P1 in west of Well J41. The sandstones were developed with stable Fig. 1) and in the strike direction of the incised valley (the thickness along the area from Well F718 to J55, quickly location of the section is shown as P2 in Fig. 1). pinched out towards the basin, changed into lacustrine Obvious slope breaks appeared in the area between Well F718 J55 J3 9 D6 5 D7 1 D 62 R0.5 R0.5 L Ls(Ω m) LLs(Ω m) D412 mv) R0.5(Ωm) SP( R0.5(Ωm) R0.5 (Ω m) S P (mv) L Ld (Ω m) m) SP(mv) LLd (Ω SP(mv) R0.5(Ωm) -10 10 20 0 10 -40 40 10 -20 20 020 1 1 10 -20 20 SQ n1 SQ y23 SQ y1 SQ qn4 SQ qn3 SP SP SP(mv) (mv)(Ωm)(mv)(Ωm) -20 0 100 10 20 0 10 50 40 0 10 05 10 15km Pet.Sci.(2009)6:230-238 235 J41 12 3 8 9 Fig. 5 Cross section in the dip direction and in the strike direction of incised valley (the position of the section is shown as P1 and P2 in Fig. 1) nd rd 1: 2 sequence boundary; 2: 3 sequence boundary; 3: lithologic surface; 4: maximum fl ooding surface of lake; 5: mudstone; 6: muddy siltstone; 7: siltstone; 8: medium-fi ne sandstone; 9: oil transport direction mudstones, and were covered by mudstones. Songliao Basin. They are distributed in a “string of beads” In the strike profile, the sand bodies are present lens shape and the hydrocarbon transport is probably also related shaped with staggered overlap, the early sand bodies were to the accumulation system of the incised valley filling developed at relatively lower levels in the valley, such as near depositional system. the Well J41 and near the Well J62 in Fig. 6, while the higher Incised valley fi lling depositional system is characterized levels in the valley are dominated by mudstones, such as near by the multi-stage fi lling of sandstones and mudstones. The the Well J53 in Fig. 5, and the later sand bodies were not lower part of incised valley filling depositional system is limited by the bottom of the valley. In the period of maximum dominated by sandstones and has lower content of mudstones, lake level of SQ , the incised valley is filled mainly by while there is a higher content of mudstones and lower y23 muddy sediments (Fig. 5). content of sandstones in the upper part. Incised valley fi lling A complete hydrocarbon accumulation system was formed deposits have different hydrocarbon transport capability due by the depositional system linkage related to incised valley to their different lithology which is shown as the obvious fi lling as follows: deltaic sand bodies collected and pumped heterogeneity. Medium-fi ne sandstones with higher porosity hydrocarbon from the active source, incised valley filling and permeability are the main transport layers and constitute depositional system completed the long-distance hydrocarbon the dominant migration passages (Fig. 6). migration, and lithological traps of shore-shallow lacustrine The core data of Well D71 indicate two short-term fi lling sandy beach bar accumulated hydrocarbon. Besides, other cycles of the incised valley and the oil-bearing properties traps in this hydrocarbon accumulation system can also form of different lithological intervals, which clearly reflect the reservoirs. Oil and gas fields including Talahong Gasfield, main intervals for hydrocarbon transport (Fig. 6). The lower Baiyinnuole Gasfi eld, Erzhan Gasfi eld, Alaxin Gasfi eld, and part is a complete short-term cycle with an erosion surface Jiangqiao Oilfi eld were discovered in the western slope of the as its bottom boundary. Above the erosion surface, the 02 4 6km J34 J53 J62 J38 SP(mv)R0.5(Ωm) SP(mv) SP(mv) SP(mv)R05( . Ωm)SP(mv) R0.5(Ωm) R0.5(Ωm) 0 40 -10+1 0 0 20 10 20 010 -10 +1 0 0 20 -10 +10 SQ n1 SQ y23 SQ qn3 -10 -20 236 Pet.Sci.(2009)6:230-238 Porosity Permeability -3 2 Lithologic columnar of core % ×10 μm 10 20 30 1 100 MTL -6.5 6.5 MTL MTL 6.0 -6.5 1 -6.5 6.0 1 2 3 4 56 7 81 9 0 11 12 Fig. 6 Core data of the incised valley fi lling of Well D71 (the well location is shown in Fig. 1) 1: mudstones; 2: silty mudstones; 3: fine sandstones; 4: medium sandstones; 5: fine sandstones with muddy pebbles; 6: medium sandstones with muddy pebbles; 7: pebbly medium sandstones; 8: mud-gravel stone; 9: scour surface; 10: oil-rich layer; 11: oil-soaked layer; 12: oil spot layer; Color code: 0 white; 5 green; 6 grey; + dark color; - light color; MTL: main transport layer depositional sequences are as follows: (1) 30 cm thick light with development of wavy cross-bedding with muddy bands gray green muddy conglomerates with no oil or gas shows; and with no oil or gas shows; (12) 10 cm thick gray green (2) 10 cm thick light gray white medium sandstones with no silty mudstones with sandy bands, with development of wavy oil or gas shows; (3) 1.5 m thick gray white fi ne sandstones bedding and with no oil or gas shows; (13) 1 m thick gray with development of wavy cross-bedding, muddy pebbles, green silty mudstones with no oil or gas shows. calcareous nodule and with no oil or gas shows; (4) 30 cm The upper short-term fi lling cycle was an incomplete one, thick gray white conglomerate-bearing medium sandstones which indicated the erosion of the bottom part, and above the with no oil or gas shows; (5) oil-soaked layer, 1.7 m thick erosional surface, muddy conglomerates and petroliferous gray white medium sandstones with development of low- fi ne-grained sandstones with cross-bedding were respectively angle cross-bedding and muddy pebbles; (6) 10 cm thick developed. gray white medium sandstones with development of muddy The results indicate that incised valley filling deposits pebbles and pyrite and with no oil or gas shows; (7) 25 are characterized by obvious heterogeneity. The medium cm thick gray white fine sandstones with development of sandstones of (5), (8), and (9) of the lower short-term cycle wavy cross-bedding and low-angle cross-bedding and with are the main transport layers for hydrocarbon migration. The no oil or gas shows; (8) oil-soaked layer, 25 cm thick gray thickness of the transport layers is about 2.05 m, and that of white medium sandstones with development of wavy cross- the lower short-term cycle is a little more than 6 m, so the bedding, muddy pebbles, carbonaceous clasts, and pyrite; (9) transport layers account for about 33% of the lower short- oil-soaked layer, 10 cm thick gray white medium sandstones term cycle of incised valley fi lling. with development of wavy bedding, and carbonaceous clasts; (10) 10 cm thick gray white medium sandstones with thin- 5 Conclusions layer mudstones interbedded, wavy bedding and with no oil or gas shows; (11) 10 cm thick gray white fine sandstones 1) The hydrocarbon of the Fulaerji Oilfi eld is derived from SQ qn2 Depth, m Color Layer number Cycle Sequence SQ y23 Pet.Sci.(2009)6:230-238 237 13(7): 837-846 the Qijia-Gulong Sag (Feng et al, 2003) and the hydrocarbon Dem bicki H and Anderson M J. Secondary migration of oil: experiments migration distance is over 80 km. This study clarified supporting effi cient movement of separate, buoyant oil phase along that incised valley filling deposits were the hydrocarbon limited conduits. AAPG Bulletin. 1989. 73(8): 1018-1021 transport layer systems, and the structural ridge passages for Fen g Z H, Liao G Z, Fang W, et al. Formation of heavy oil and hydrocarbon migration proposed by Xiang et al (2004) were correlation of oil-source in the western slope of the northern situated in the incised valley fi lling deposits. Songliao Basin. Petroleum Exploration and Development. 2003. 2) Towards the basin, incised valley fi lling deposits joined 30(4): 25-28 (in Chinese) with the delta formed in the early period, while towards the Fer guson T W and Davis R A. Post-Miocene stratigraphy and basin margin, they joined with the shore-shallow lacustrine depositional environments of valley-fill sequences at the mouth of beach bar sandbodies developed during the maximum lake Tampa Bay, Florida. Marine Geology. 2003. 200(1): 157-170 level in the basin margin area. Consequently, a complete Fu X F , Wang P Y, Lü Y F, et al. Tectonic features and control of oil-gas accumulation in the west slope of Songliao Basin. Chinese Journal of sedimentary system is formed, i.e., delta system—incised Geology. 2007. 42(2): 209-222 (in Chinese) valley fi lling system—shore facies sandy beach bar system, Gao R Q and Cai X Y. The Formation Conditions and Distribution Rules which are all characterized by the development of sandstones of Oil and Gas Pools of Songliao Basin. Beijing: Petroleum Industry with high sand content, high porosity, and high permeability. Press. 1997. 47-103 (in Chinese) The porosity is about 26%-30% and the permeability is about Gao R Q and Xiao D M. Advances in Oil and Gas Exploration in the -3 2 -3 2 160×10 μm to 280×10 μm , so these systems have good Songliao Basin and Surrounding Basins. Beijing: Petroleum Industry capability for hydrocarbon transportation and accumulation. Press. 1995. 19-24 (in Chinese) 3) The incised valley filling depositional system is Gao R Q, Zhang Y and Cui T C. Cretaceous Oil and Gas Strata of the characterized by its multi-cycle architecture. In the dip profi le Songliao Basin. Beijing: Petroleum Industry Press. 1994. 6-47 (in of the incised valley, tracing the source from the slope break, Chinese) sand bodies overlap layer by layer along the bottom surface of Ghi nassi M. The effects of differential subsidence and coastal topography on high-order transgressive-regressive cycles: Pliocene incised valley, and split and pinch out into mudstones towards nearshore deposits of the Val d’Orcia Basin, Northern Apennines, the basin. The sandstones, which overlap along the bottom Italy. Sedimentary Geology. 2007. 202(4): 677-701 surface of incised valley, are transport layers for hydrocarbon Ghi setti F and Vezzani L. Detachments and normal faulting in the migration and accumulation. A complete hydrocarbon Marche fold-and-thrust belt (central Apennines, Italy): inferences on accumulation system was formed by the depositional system fl uid migration paths. Journal of Geodynamics. 2000. 29(3-5): 345- linkage related to incised valley filling as follows: deltaic sand bodies collected and pumped hydrocarbon from the Hao F, Zou H Y and Jiang J Q. Dynamics of petroleum accumulation and active source, incised valley filling depositional system its advances. 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Published: Jul 23, 2009

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