Model of Tight Conglomerate Oil Accumulation in the Mahu Sag, Junggar Basin, Northwest China

Abstract

Research based on oil accumulation models is essential for exploring the hydrocarbon accumulation theory further. Studies on tight oil accumulation models focused on fan delta depositional systems, and in particular, systems involving source-reservoir separated type are scarce. To explore the accumulation model of tight oil in conglomerate, this study focused on the Permian–Triassic tight conglomerate oil in Mahu sag, Junggar Basin, using well drilling, well logging, seismic profiling, oil testing, and laboratory data, and analyzed the formation conditions, formation types, and distribution patterns of conglomerate reservoirs. The results show that, the conglomerate reservoirs are predominantly lithologic reservoirs and partly fault-lithologic reservoirs; there is no water evident at the edge or bottom around the reservoirs. The tight conglomerate layer in the delta plain subfacies of each fan exhibits high clay content and intense diagenesis, and the argillaceous rocks in the pro-fan delta subfacies and shallow lacustrine facies form the sealing and floor conditions. The sandy conglomerate of fan delta front subfacies is the main reservoir body. Additionally, strike-slip faulting in the Indosinian-Himalayan period formed an efficient faulting system for trans-stratal migration with Hercynian-Indosinian inverse faulting. Oil migration is driven by the overpressure caused by hydrocarbon generation from alkali lacustrine source rocks. The distribution of reservoirs is primarily controlled by the large fan bodies, namely the Zhongguai, Baijiantan, Karamay, Huangyangquan, Xiazijie, Xiayan, and Dabasong fans. Each fan body forms a group of reservoirs or oilfields, resulting in a widely distributed pattern, according to which reservoir and sealing constitute one whole body—i.e., patterns of “one sand and one reservoir, one fan and one field.” This results in a quasi-continuous accumulation model, which includes strong oil charging, efficient faulting transportation, trans-stratal migration, and lithologic trapped accumulation. The proposed model is an important supplement to the existing model of quasi-continuous oil and gas accumulation. Overall, this study enriches unconventional oil and gas accumulation theories.

Keywords

tight conglomerate oil / fan delta facies / quasi-continuous accumulation / accumulation model / Mahu sag / Junggar Basin / hydrocarbons / petroleum geology

References

[1] CaoJ, LeiD W, LiY W, et al.. Ancient High-Quality Alkaline Lacustrine Source Rocks Discovered in the Lower Permian Fengcheng Formation, Junggar Basin. Acta Petrolei Sinica, 2015, 36(7): 781-790 (in Chinese with English Abstract)

[2] CaoJ, XiaL W, WangT T, et al.. An Alkaline Lake in the Late Paleozoic Ice Age (LPIA): A Review and New Insights into Paleoenvironment and Petroleum Geology. Earth-Science Reviews, 2020, 202: 103091

[3] ChenL, YangH B, QianY X, et al.. Favorable Conditions for Forming Permian Gas Reservoirs in Zhongguai 158 Area in Northwestern Margin of Junggar Basin and Their Main Controlling Factors. China Petroleum Exploration, 2007, 12(5): 22-25 78 (in Chinese with English Abstract)

[4] ChenX F, YangX W, XueX K, et al. Theory and Fine Exploration Practice of Composite Oil & Gas Accumulation in Northwestern Margin of Junggar Basin, 2014 Beijing Petroleum Industry Press 203-230 (in Chinese)

[5] ChenY B, ChengX G, ZhangH, et al.. Fault Characteristics and Control on Hydrocarbon Accumulation of Middle-Shallow Layers in the Slope Zone of Mahu Sag, Junggar Basin, NW China. Petroleum Exploration and Development, 2018, 45(6): 1050-1060

[6] ChenZ L, LiuG D, WangX L, et al.. Origin and Mixing of Crude Oils in Triassic Reservoirs of Mahu Slope Area in Junggar Basin, NW China: Implication for Control on Oil Distribution in Basin Having Multiple Source Rocks. Marine and Petroleum Geology, 2016, 78: 373-389

[7] FengC, LiT, HeW J, et al.. Organic Geochemical Traits and Paleo-Depositional Conditions of Source Rocks from the Carboniferous to Permian Sediments of the Northern Mahu Sag, Junggar Basin, China. Journal of Petroleum Science and Engineering, 2020, 191: 107117

[8] GaoG, WangX L, LiuG D, et al.. Analyses of the Genesis and Potential of Natural Gas in Kebai Area of Northwest Margin, Junggar Basin. Geological Journal of China Universities, 2012, 18(2): 307-317 (in Chinese with English Abstract)

[9] HuangY F, ZhangC M, ZhuR, et al.. Palaeoclimatology, Provenance and Tectonic Setting during Late Permian to Middle Triassic in Mahu Sag, Junggar Basin, China. Earth Science, 2017, 42(10): 1736-1749 (in Chinese with English Abstract)

[10] IminA, TangY, CaoJ, et al.. Accumulation Mechanism and Enrichment Rules of the Continuous Hydrocarbon Plays in the Lower Triassic Baikouquan Formation of the Mahu Sag, Junggar Basin. Natural Gas Geoscience, 2016, 27(2): 241-250 (in Chinese with English Abstract)

[11] IminA, ZhaM, DingX J, et al.. Identification of a Permian Foreland Basin in the Western Junggar Basin (NW China) and Its Impact on Hydrocarbon Accumulation. Journal of Petroleum Science and Engineering, 2020, 187: 106810

[12] JiaH B, JiH C, WangL S, et al.. Reservoir Quality Variations within a Conglomeratic Fan-Delta System in the Mahu Sag, Northwestern Junggar Basin: Characteristics and Controlling Factors. Journal of Petroleum Science and Engineering, 2017, 152: 165-181

[13] JiangW L, IminA, WangX Y, et al.. Geochemical Characterization and Quantitative Identification of Mixed-Source Oils from the Baikouquan and Lower Wuerhe Formations in the Eastern Slope of the Mahu Sag, Junggar Basin, NW China. Journal of Petroleum Science and Engineering, 2020, 191: 107175

[14] KangX, HuW X, CaoJ, et al.. Controls on Reservoir Quality in Fan-Deltaic Conglomerates: Insight from the Lower Triassic Baikouquan Formation, Junggar Basin, China. Marine and Petroleum Geology, 2019, 103: 55-75

[15] KuangL C, ZhiD M, WangX J, et al.. Hydrocarbon Accumulation Conditions and Exploration Directions of large-Scale Lithologic-Stratigraphic Oil and Gas Reservoirs in Upper Wuerhe Formation of Upper Permian in Junggar Basin. Acta Petrolei Sinica, 2022, 43(3): 325-340 (in Chinese with English Abstract)

[16] LiJ, TangY, WuT, et al.. Overpressure Origin and Its Effects on Petroleum Accumulation in the Conglomerate Oil Province in Mahu Sag, Junggar Basin, NW China. Petroleum Exploration and Development, 2020, 47(4): 726-739

[17] LiangY Y, ZhangY Y, ChenS, et al.. Controls of a Strike-Slip Fault System on the Tectonic Inversion of the Mahu Depression at the Northwestern Margin of the Junggar Basin, NW China. Journal of Asian Earth Sciences, 2020, 198: 104229

[18] LiuG D, ChenZ L, WangX L, et al.. Migration and Accumulation of Crude Oils from Permian Lacustrine Source Rocks to Triassic Reservoirs in the Mahu Depression of Junggar Basin, NW China: Constraints from Pyrrolic Nitrogen Compounds and Fluid Inclusion Analysis. Organic Geochemistry, 2016, 101: 82-98

[19] LiuS J, GaoG, GangW Z, et al.. Comparison of Formation Conditions of Source Rocks of Fengcheng and Lucaogou Formations in the Junggar Basin, NW China: Implications for Organic Matter Enrichment and Hydrocarbon Potential. Journal of Earth Science, 2023, 34(4): 1026-1040

[20] MaL, ZhangY, ZhangZ H, et al.. The Geochemical Characteristics of the Fengcheng Formation Source Rocks from the Halaalate Area, Junggar Basin, China. Journal of Petroleum Science and Engineering, 2020, 184: 106561

[21] MengX C, ChenN G, SuJ, et al.. Reservoir Property Diversity of Different Lithofacies in Sandy Conglomerate during Oil-Gas Injection Period and Reservoir-Formation Significance: A Case from Baikouquan Formation in West Slope of Mahu Depression, Junggar Basin. Acta Sedimentologica Sinica, 2016, 34(3): 606-614 (in Chinese with English Abstract)

[22] PanJ G, WangG D, QuY Q, et al.. Formation Mechanism and Characteristic of Sandy Conglomerate Diagenetic Trip: A Case Study of the Triassic Baikouquan Formation in the Mahu Sag, Junggar Basin. Natural Gas Geoscience, 2015, 26(S1): 41-48 (in Chinese with English Abstract)

[23] QiW, PanJ G, WangG D, et al.. Fluid Inclusion and Hydrocarbon Charge History for the Reservoir of Baikouquan Formation in the Mahu Sag, Junggar Basin. Natural Gas Geoscience, 2015, 26(S1): 64-71 (in Chinese with English Abstract)

[24] QuJ H, YangR R, TangY. Large-Area Petroleum Accumulation Model of the Triassic Glutenite Reservoirs in the Mahu Sag, Junggar Basin: Triple Controls of Fan, Fault and Overpressure. Acta Geologica Sinica, 2019, 93(4): 915-927 (in Chinese with English Abstract)

[25] SchmokerJ W, et al. GautierD L, DoltonG L, TakahashiK I, et al.. Method for Assessing Continuous-Type (Unconventional) Hydrocarbon Accumulations. National Assessment of United States Oil and Gas Resources Results, Methodology, and Supporting Data, 1995 30

[26] SchmokerJ W. Resource-Assessment Perspectives for Unconventional Gas Systems. AAPG Bulletin, 2002, 86(11): 1993-1999

[27] ShaoY, WangR F, ZhangY Q, et al.. Strike-Slip Structures and Oil-Gas Exploration in the NW Margin of the Junggar Basin, China. Acta Petrolei Sinica, 2011, 32(6): 976-984 (in Chinese with English Abstract)

[28] SunL D, ZouC N, JiaA L, et al.. Development Characteristics and Orientation of Tight Oil and Gas in China. Petroleum Exploration and Development, 2019, 46(6): 1073-1087

[29] TanC P, YuX H, LiuB B, et al.. Conglomerate Categories in Coarse-Grained Deltas and Their Controls on Hydrocarbon Reservoir Distribution: A Case Study of the Triassic Baikouquan Formation, Mahu Depression, NW China. Petroleum Geoscience, 2017, 23(4): 403-414

[30] TangW B, ZhangY Y, Pe-PiperG, et al.. Permian to Early Triassic Tectono-Sedimentary Evolution of the Mahu Sag, Junggar Basin, Western China: Sedimentological Implications of the Transition from Rifting to Tectonic Inversion. Marine and Petroleum Geology, 2021, 123: 104730

[31] TangY, GuoW J, WangX T, et al.. New Breakthroughs in Exploration of Conglomerate Large Oil Area in Mahu Sag and Its Enlightenment. Xinjiang Petroleum Geology, 2019, 40(2): 127-137 (in Chinese with English Abstract)

[32] TangY, XuY, LiY Z, et al.. Sedimentation Model and Exploration Significance of Large-Scaled Shallow Retrogradation Fan Delta in Mahu Sag. Xinjiang Petroleum Geology, 2018, 39(1): 16-22 (in Chinese with English Abstract)

[33] TangY, XuY, QuJ H, et al.. Fan-Delta Group Characteristics and Its Distribution of the Triassic Baikouquan Reservoirs in Mahu Sag of Junggar Basin. Xinjiang Petroleum Geology, 2014, 35(6): 628-635 (in Chinese with English Abstract)

[34] TangY, YinT J, QinJ H, et al.. Development of Large-Scale Shallow-Water Fan Delta: Sedimentary Laboratory Simulation and Experiments. Xinjiang Petroleum Geology, 2017, 38(3): 253-263 (in Chinese with English Abstract)

[35] TangY, CaoJ, HeW J, et al.. Development Tendency of Geological Theory of Total Petroleum System: Insights from the Discovery of Mahu Large Oil Province. Xinjiang Petroleum Geology, 2021, 42(1): 1-9 (in Chinese with English Abstract)

[36] TangY, SongY, GuoX G, et al.. Main Controlling Factors of Tight Conglomerate Oil Enrichment above Source Kitchen in Mahu Sag, Junggar Basin. Acta Petrolei Sinica, 2022, 43(2): 192-206 (in Chinese with English Abstract)

[37] TaoK Y, CaoJ, WangY C, et al.. Geochemistry and Origin of Natural Gas in the Petroliferous Mahu Sag, Northwestern Junggar Basin, NW China: Carboniferous Marine and Permian Lacustrine Gas Systems. Organic Geochemistry, 2016, 100: 62-79

[38] WangA G, WangZ L, LiL, et al.. Hydrocarbon Migration in the Multiple-Sourced Petroleum System in the Northwestern Junggar Basin (Northwestern China): Constraint from Geochemical and Phase Fractionation Analysis. AAPG Bulletin, 2019, 103(9): 2247-2284

[39] WangT T, CaoJ, JinJ, et al.. Spatiotemporal Evolution of a Late Paleozoic Alkaline Lake in the Junggar Basin, China. Marine and Petroleum Geology, 2021, 124: 104799

[40] WangX L, ZhiD M, WangY T, et al. Source Rocks and Oil-Gas Geochemistry in Junggar Basin, 2013 Beijing Petroleum Industry Press 30-62 (in Chinese)

[41] WangY J, JiaD, PanJ G, et al.. Multiple-Phase Tectonic Superposition and Reworking in the Junggar Basin of Northwestern China—Implications for Deep-Seated Petroleum Exploration. AAPG Bulletin, 2018, 102(8): 1489-1521

[42] WuK Y, QuJ H, WangH H, et al.. Strike-Slip Characteristics, Forming Mechanisms and Controlling Reservoirs of Dazhuluogou Fault in Junggar Basin. Journal of China University of Petroleum (Natural Science Edition), 2014, 38(5): 41-47 (in Chinese with English Abstract)

[43] WuK Y, LiuB, LiuY, et al.. Characteristics, Formation and Evolution of Fault System in Zhongguai Uplift of Junggar Basin, China. Journal of Earth Science and Environment, 2017, 39(3): 406-418 (in Chinese with English Abstract)

[44] XiK L, CaoY C, HaileB G, et al.. Diagenetic Variations with Respect to Sediment Composition and Paleo-Fluids Evolution in Conglomerate Reservoirs: A Case Study of the Triassic Baikouquan Formation in Mahu Sag, Junggar Basin, Northwestern China. Journal of Petroleum Science and Engineering, 2021, 197: 107943

[45] XiaoM, WuS T, YuanX J, et al.. Diagenesis Effects on the Conglomerate Reservoir Quality of the Baikouquan Formation, Junggar Basin, China. Journal of Petroleum Science and Engineering, 2020, 195: 107599

[46] XiaoZ L, ChenS J, LiuC W, et al.. Lake Basin Evolution from Early to Middle Permian and Origin of Triassic Baikouquan Oil in the Western Margin of Mahu Sag, Junggar Basin, China: Evidence from Geochemistry. Journal of Petroleum Science and Engineering, 2021, 203: 108612

[47] XuH M, XuZ H, LiZ H, et al.. Characteristics of Strike-Slip Faults in the Northwestern Margin of Junggar Basin and Their Geological Significance for Petroleum. Geological Journal of Universities, 2008, 14(2): 217-222 (in Chinese with English Abstract)

[48] YuK H, CaoY C, QiuL W, et al.. Depositional Environments in an Arid, Closed Basin and Their Implications for Oil and Gas Exploration: The Lower Permian Fengcheng Formation in the Junggar Basin, China. AAPG Bulletin, 2019, 103(9): 2073-2115

[49] YuanG H, CaoY C, QiuL W, et al.. Genetic Mechanism of High-Quality Reservoirs in Permian Tight Fan Delta Conglomerates at the Northwestern Margin of the Junggar Basin, Northwestern China. AAPG Bulletin, 2017, 101(12): 1995-2019

[50] ZhangC M, SongX M, WangX J, et al.. Origin and Depositional Characteristics of Supported Conglomerates. Petroleum Exploration and Development, 2020, 47(2): 292-305

[51] ZhangY Q, WangX, LiuJ S, et al.. Wuerhe-Xiazijie Strike-Slip Structure and Petroleum Exploration Significance in Northwestern Margin of Junggar Basin. Xinjiang Petroleum Geology, 2011, 32: 447-450 (in Chinese with English Abstract)

[52] ZhangZ J, YuanX J, WangM S, et al.. Alkaline-Lacustrine Deposition and Paleoenvironmental Evolution in Permian Fengcheng Formation at the Mahu Sag, Junggar Basin, NW China. Petroleum Exploration and Development, 2018, 45(6): 1036-1049

[53] ZhaoJ Z, CaoQ, BaiY B, et al.. Petroleum Accumulation from Continuous to Discontinuous: Concept, Classification and Distribution. Acta Petrolei Sinica, 2016, 37(2): 145-159 (in Chinese with English Abstract)

[54] ZhaoJ Z, FuJ H, CaoQ, et al. Accumulation Theory and Evaluation Techniques of Tight Oil and Gas, 2017 Beijing Petroleum industry Press 393-415 (in Chinese)

[55] ZhaoJ Z, LiJ, CaoQ, et al.. Hydrocarbon Accumulation Patterns of Large Tight Oil and Gas Fields. Oil & Gas Geology, 2013, 34(5): 573-583 (in Chinese with English Abstract)

[56] ZhaoJ Z, LiJ, CaoQ, et al.. Quasi-Continuous Hydrocarbon Accumulation: An Alternative Model for the Formation of Large Tight Oil and Gas Accumulations. Journal of Petroleum Science and Engineering, 2019, 174: 25-39

[57] ZhaoJ Z, LiJ, WuW T, et al.. The Petroleum System: A New Classification Scheme Based on Reservoir Qualities. Petroleum Science, 2019, 16(2): 229-251

[58] ZhiD M. Discovery and Hydrocarbon Accumulation Mechanism of Quasi-Continuous High-Efficiency Reservoirs of Baikouquan Formation in Mahu Sag, Junggar Basin. Xinjiang Petroleum Geology, 2016, 37(4): 373-382 (in Chinese with English Abstract)

[59] ZouC N, YangZ, ZhangG S, et al.. Theory, Technology and Practice of Unconventional Petroleum Geology. Journal of Earth Science, 2023, 34(4): 951-965

[60] ZouC N, ZhangG S, YangZ, et al.. Concepts, Characteristics, Potential and Technology of Unconventional Hydrocarbons: On Unconventional Petroleum Geology. Petroleum Exploration and Development, 2013, 40(4): 413-428

RIGHTS & PERMISSIONS

China University of Geosciences (Wuhan) and Springer-Verlag GmbH Germany, Part of Springer Nature