Occurrence Characteristics of Saline-Lacustrine Shale-Oil in the Qianjiang Depression, Jianghan Basin, Central China

Abstract

The amount of shale oil and its characterization are key issues in the study of shale oil. At present, many scholars use a variety of methods to evaluate the amount of shale oil, and use the calculated amount of hydrocarbons to analyze its influencing factors; however, there is lack of detailed research on the storage space for shale-oil and it’s influencing factors. In view of this issue, gas chromatography (GC), gas chromatography-mass spectrometry (GC-MS), soxhlet extraction (SE), fieldemission scanning electron microscopy (FE-SEM), low-temperature nitrogen adsorption (LTNA), high-pressure mercury intrusion (HPMI), and X-ray diffraction (XRD) were used to analyze and compare samples from two wells located in different deposition locations. The unconventional Well BYY2 and BX7s were drilled in the depocenter and distal area of the Qianjiang Formation, respectively. Controlled by differences in the organic matter type and sedimentary environment, the organic matter in Well BYY2, which was found to be characterized by laminar shale, mainly originated from aquatic algae. The results showed that as the total organic carbon (TOC) content increased, the amount of shale-oil in the pores increased. Shale-oil was mostly stored in mesopores and macropores that had been preserved by dolomite minerals of a biogenic origin and also occurred in pores sized 5–200 nm and >1 µm. Dolomite minerals of a biogenic origin and clay minerals contributed to the occurrence of shale-oil. In comparison, the organic matter in Well BX7 has been greatly influenced by terrestrial organic matter. Pores in the massive mudstones from Well BX7 were determined to be mainly mesopores preserved by clay minerals and quartz, and the shale-oil was mostly stored within the pores of < 40 nm. When the TOC content was ∼2.5 wt.%, the generated shale-oil reached saturation. Clay minerals contributed to the occurrence of shale-oil, whereas quartz only contributed to the occurrence of shale-oil in macropores.

Keywords

shale oil / reservoir / storage space of shale oil / saline lacustrine / Jianghan Basin

References

Cao Q, Zhou W, Chen W L, . Analysis of Pore Types, Sizes and Genesis in Continental Shale Gas Resevoir of Chang 7 of Yanchagn Formation, Odros Basin. Journal of Mineralogy and Petrology, 2015, 35(2): 90-97. (in Chinese with English Abstract)

Carroll A R, Bohacs K M. Lake-Type Controls on Petroleum Source Rock Potential in Nonmarine Basins. AAPG Bulletin, 2001, 85: 1033-1053.

Chen X H, Chen L, Jiang S, . Evaluation of Shale Reservoir Quality by Geophysical Logging for Shuijingtuo Formation of Lower Cambrian in Yichang Area, Central Yangtze. Journal of Earth Science, 2021, 32(4): 766-777.

Chen Z H, Li M W, Cao T T, . Hydrocarbon Generation Kinetics of a Heterogeneous Source Rock System: Example from the Lacsutrine Eocene-Oligocene Shahejie Formation, Bohai Bay Basin, China. Energy & Fuels, 2017, 31(12): 13291-13304.

Couch E L. Calculation of Paleosalinities from Boron and Clay Mineral Data. AAPG Bulletin, 1971, 55: 1829-1837.

Deng S C, Dong H L, Lv G, . Microbial Dolomite Precipitation Using Sulfate Reducing and Halophilic Bacteria: Results from Qinghai Lake, Tibetan Plateau, NW China. Chemical Geology, 2010, 278(3): 151-159. 4

Ewing T E. Mississippian Barnett Shale, Fort Worth Basin, North-Central Texas: Gas-Shale Play with Multi-Trillion Cubic Foot Potential: Discussion. AAPG Bulletin, 2006, 90(6): 963-966.

Fang Z X. Main Controlling Factors and Exploration Direction of Subtle Oil Reservoirs in Qianjiang Depression. Oil & Gas Geology, 2006, 27(6): 804-812. (in Chinese with English Abstract)

Feng G Q, Li J J, Liu J W, . Discussion on the Enrichment and Mobility of Continental Shale Oil in Biyang Depression. Oil & Gas Geology, 2019, 40(6): 1236-1245. (in Chinese with English Abstract)

Gao Z Y, Xiong S L. Methane Adsorption Capacity Reduction Process of Water-Bearing Shale Samples and Its Influencing Factors: One Example of Silurian Longmaxi Formation Shale from the Southern Sichuan Basin in China. Journal of Earth Science, 2021, 32(4): 946-959.

García del Cura M A, Calvo J P, Ordóñez S, . Petrographic and Geochemical Evidence for the Formation of Primary, Bacterially Induced Lacustrine Dolomite: La Roda ‘White Earth’ (Pliocene, Central Spain). Sedimentology, 2001, 48(4): 897-915.

Grice K, Schouten S, Peters K E, . Molecular Isotopic Characterisation of Hydrocarbon Biomarkers in Palaeocene-Eocene Evaporitic, Lacustrine Source Rocks from the Jianghan Basin, China. Organic Geochemistry, 1998, 29(5): 1745-1764. 6/7

Hammes U, Hamlin H S, Ewing T E. Geologic Analysis of the Upper Jurassic Haynesville Shale in East Texas and West Louisiana. AAPG Bulletin, 2011, 95(10): 1643-1666.

Han Y J, Mahlstedt N, Horsfield B. The Barnett Shale: Compositional Fractionation Associated with Intraformational Petroleum Migration, Retention and Expulsion. AAPG Bulletin, 2015, 99: 2173-2202.

Hou Y G, Wang F R, He S, . Properties and Shale Oil Potential of Saline Lacustrine Shales in the Qianjiang Depression, Jianghan Basin, China. Marine and Petroleum Geology, 2017, 86: 1173-1190.

Hu Q H, Zhang Y X, Meng X H, . Characterization of Micro-Nano Pore Networks in Shale Oil Reservoirs of Paleogene Shahejie Formation in Dongying Sag of Bohai Bay Basin, East China. Petroleum Exploration and Development, 2017, 44(5): 720-730.

Huang Z K, Chen J P, Wang Y J, . Characteristics of Micropores in Mudstones of the Cretaceous Qingshankou Formation, Songliao Basin. Acta Petrolei Sinica, 2013, 34(1): 30-36. (in Chinese with English Abstract)

Jarvie D M. Components and Processes Affecting Producibility and Commerciality of Shale Resource Systems. Geologica Acta, 2014, 12(4): 307-325

Jiang Q G, Li M W, Qian M H, . Quantitative Characterization of Shale Oil in Different Occurrence States and Its Application. Petroleum Geology & Experiment, 2016, 38(6): 842-849. (in Chinese with English Abstract)

Jiang Z X. Sedimentology, 2010, Beijing: Petroleum Industry Press (in Chinese)

Katz B, Lin F. Lacustrine Basin Unconventional Resource Plays: Key Differences. Marine and Petroleum Geology, 2014, 56: 255-265.

Kong X X, Jiang Z X, Zheng Y H, . Organic Geochemical Characteristics and Organic Matter Enrichment of Mudstones in an Eocene Saline Lake, Qianjiang Depression, Hubei Province, China. Marine and Petroleum Geology, 2020, 114: 104194

Li J B, Huang W B, Lu S F, . Nuclear Magnetic Resonance T ₁ — T ₂ Map Division Method for Hydrogen-Bearing Components in Continental Shale. Energy & Fuels, 2018, 32(9): 9043-9054.

Li J Q, Zhang P F, Lu S F, . Scale-Dependent Nature of Porosity and Pore Size Distribution in Lacustrine Shales: An Investigation by BIB-SEM and X-Ray CT Methods. Journal of Earth Science, 2019, 30(4): 823-833.

Li L, Liu A W, Qi Z X, . Pore Structure Characteristics of Shale Reservoir of the Lower Qian 4 Member in the Wangchang Anticline of the Qianjiang Sag. Earth Science, 2020, 45(2): 602-616. (in Chinese with English Abstract)

Li Z, Jiang Z X, Tang X L, . Lithofacies Characteristics and Its Effect on Pore Structure of the Marine Shale in the Low Silurian Longmaxi Formation, Southeastern Chongqing. Earth Science, 2017, 42(7): 1116-1123. (in Chinese with English Abstract)

Liang C, Cao Y C, Liu K Y, . Diagenetic Variation at the Lamina Scale in Lacustrine Organic-Rich Shales: Implications for Hydrocarbon Migration and Accumulation. Geochimica et Cosmochimica Acta, 2018, 229 112-128.

Lin H X, Wang S Z, Li Y L, . Hydrocarbon Generation Simulation of Different Carboniferous Source Rocks in the Junggar Basin. Natural Gas Industry, 2014, 34(10): 27-32. (in Chinese with English Abstract)

Liu Y, Yao Y B, Liu D M, . Shale Pore Size Classification: an NMR Fluid Typing Method. Marine and Petroleum Geology, 2018, 96: 591-601.

Liu Z X, Yan D T, Niu X. Insights into Pore Structure and Fractal Characteristics of the Lower Cambrian Niutitang Formation Shale on the Yangtze Platform, South China. Journal of Earth Science, 2020, 31(1): 169-180.

Long Y M, Chen M F, Chen F L, . Characteristics and Influencing Factors of Inter-Salt Shale Oil Reservoirs in Qianjiang Formation, Qianjiang Sag. Petroleum Geology and Recovery Efficiency, 2019, 26(1): 59-64. (in Chinese with English Abstract)

Loucks R G, Reed R M, Ruppel S C, . Morphology, Genesis, and Distribution of Nanometer-Scale Pores in Siliceous Mudstones of the Mississippian Barnett Shale. Journal of Sedimentary Research, 2009, 79(12): 848-861.

Lu S F, Huang W B, Chen F W, . Classification and Evaluation Criteria of Shale Oil and Gas Resources: Discussion and Application. Petroleum Exploration and Development, 2012, 39(2): 268-276.

Ma X X, Li M W, Pang X Q, . Paradox in Bulk and Molecular Geochemical Data and Implications for Hydrocarbon Migration in the Inter-Salt Lacustrine Shale Oil Reservoir, Qianjiang Formation, Jianghan Basin, Central China. International Journal of Coal Geology, 2019, 209: 72-88.

Mastandrea A, Perri E, Russo F, . Microbial Primary Dolomite from a Norian Carbonate Platform: Northern Calabria, Southern Italy. Sedimentology, 2006, 53(3): 465-480.

Milliken K L, Rudnicki M, Awwiller D N, . Organic Matter-Hosted Pore System, Marcellus Formation (Devonian), Pennsylvania. AAPG Bulletin, 2013, 97(2): 177-200.

Murray A P, Sosrowidjojo I B, Alexander R, . Oleananes in Oils and Sediments: Evidence of Marine Influence during Early Diagenesis?. Geochimica et Cosmochimica Acta, 1997, 61(6): 1261-1276.

Nie H K, Ma X, Yu C, . Shale Gas Reservoir Characteristics and Its Exploration Potential-Analysis on the Lower Jurassic Shale in the Eastern Sichuan Basin. Oil & Gas Geology, 2017, 38(3): 438-447. (in Chinese with English Abstract)

Nie H K, Zhang P X, Bian R K, . Oil Accumulation Characteristics of China Continental Shale. Earth Science Frontiers, 2016, 23(2): 55-62. (in Chinese with English Abstract)

Pang F, Zhang Z H, Zhang J F, . Progress and Prospect on Exploration and Development of Shale Gas in the Yangtze River Economic Belt. Earth Science, 2020, 45(6): 2152-2159. (in Chinese with English Abstract)

Peters K E, Cunningham A E, Walters C C, . Petroleum Systems in the Jiangling-Dangyang Area, Jianghan Basin, China. Organic Geochemistry, 1996, 24(10): 1035-1060. 11

Qian M H, Jiang Q G, Li M W, . Quantitative Characterization of Extractable Organic Matter in Lacustrine Shale with Different Occurrences. Petroleum Geology & Experiment, 2017, 39(2): 278-286. (in Chinese with English Abstract)

Shen J J. Mechanism for Rormation of Lacustrine Dolomites of the Lower Xingouzui Formation in the Southern Part of the Qianjiang Depression and Its Petroleum Geologic Implication, 2013, Wuhan: Yangtze University (in Chinese with English Abstract)

Sing K S W, Everett D W, Haul R A W, . Reporting Physisorption Data for Gas/Solid Systems with Special Reference to the Determination of Surface Area and Porosity (Recommendations 1984). Pure and Applied Chemistry, 1985, 57(4): 603-619.

Sinninghe Damsté J S, Kenig F, Koopmans M P, . Evidence for Gammacerane as an Indicator of Water Column Stratification. Geochimica et Cosmochimica Acta, 1995, 59(9): 1895-1900.

Song C Y. Combined Characteristics of the Biomarker in Salt-Lake Facies Carbonate Rock—Taking Bonan of Jiyang Depression as an Example. P. G. O. D. D., 2008, 27(6): 35-38. (in Chinese with English Abstract)

Song G Q, Zhang L Y, Lu S F, . Resource Evaluation Method for Shale Oil and Its Application. Earth Science Frontiers, 2013, 20(4): 221-228. (in Chinese with English Abstract)

Sun Z L, Wang F R, He S, . Study on Pore Structure of Inter-Salt Shale Oil Reservoir about Typical Salt Cyclothem of Qianjiang Depression in Jianghan Basin. Journal of Shenzhen University Science and Engeering, 2019, 36(3): 289-297. (in Chinese with English Abstract)

Sun Z L, Wang F R, Hou Y G, . Spatial Characterization and Influencing Factors of Soluble Organic Matter in Shale of Qianjiang Formation in Qianjiang Depression. Geological Science and Technology Information, 2019, 38(6): 81-90. (in Chinese with English Abstract)

Sun Z L, Wang F R, Hou Y G, . Main Controlling Factors and Modes of Organic Matter Enrichment in Salt Lake Shale. Earth Science, 2020, 45(4): 1375-1387. (in Chinese with English Abstract)

Wang D F, Wang S Z. Oil and Geology of Saline Lake, 1998, Beijing: Petroleum Industry Press

Wang G L, Yang Y Q, Zhang Y S, . Sedimentary Microfacies and Evolution of the Qianjiang Formation of Paleogene at Wangchang Area in Qianjiang Sag, Jianghan Basin. Journal of Palaeogeography, 2004, 6(2): 140-150. (in Chinese with English Abstract)

Wang M, Ma R, Li J B, . Occurrence Mechanism of Lacustrine Shale Oil in the Paleogene Shahejie Formation of Jiyang Depression, Bohai Bay Basin, China. Petroleum Exploration and Development, 2019, 46(4): 833-846.

Wei L, Mastalerz M, Schimmelmann A, . Influence of Soxhlet-Extractable Bitumen and Oil on Porosity in Thermally Maturing Organic-Rich Shales. International Journal of Coal Geology, 2014, 132: 38-50.

Wright D T, Wacey D. Sedimentary Dolomite: a Reality Check. Geological Society, London, Special Publications, 2004, 235(1): 65-74.

Wu H G, Hu W X, Cao J, . A Unique Lacustrine Mixed Dolomitic-Clastic Sequence for Tight Oil Reservoir within the Middle Permian Lucaogou Formation of the Junggar Basin, NW China: Reservoir Characteristics and Origin. Marine and Petroleum Geology, 2016, 76: 115-132.

Wu L G, Li X S, Guo X B, . Diagenetic Evolution and Formation Mechanism of Dissolved Pore of Shale Oil Reservoirs of Lucaogou Formation in Malang Sag. Journal of China University of Petroleum (Edition of Natural Science), 2012, 36(3): 38-43. 53 (in Chinese with English Abstract)

Wu S Q, Tang X S, Du X J, . Geologic Characteristics of Continental Shale Oil in the Qianjiang Depression, Jianghan Salt Lake Basin. Journal of East China Institute of Technology (Natural Science), 2013, 36(3): 282-286. (in Chinese with English Abstract)

Xiao F. Study on the Characteristics of Salt Shale Reservoir in Qianjiang Formation in Qianjiang Sag—A Case Study of the 10th Rhythm of Eq3⁴ and the 5th Rhythm of Middle Eq4⁰, 2017, Wuhan: Yangtze University (in Chinese with English Abstract)

Yang C, Zhang J C, Tang X, . Comparative Study on MicroPore Structure of Marine, Terrestrial, and Transitional Shales in Key Areas, China. International Journal of Coal Geology, 2017, 171: 76-92.

Yang R, Hu Q H, He S, . Pore Structure, Wettability and Tracer Migration in Four Leading Shale Formations in the Middle Yangtze Platform, China. Marine and Petroleum Geology, 2018, 89: 415-427.

Zhang L Y, Bao Y S, Li J Y, . Movability of Lacustrine Shale Oil: A Case Study of Dongying Sag, Jiyang Depression, Bohai Bay Basin. Petroleum Exploration and Development, 2014, 41(6): 703-711.

Zhang Y Q, Li L. Insights into the Formation Mechanism of Low Water Saturation in Longmaxi Shale in the Jiaoshiba Area, Eastern Sichuan Basin. Journal of Earth Science, 2021, 32(4): 863-871.

Zhao Y, Cai J G, Lei T Z, . Quantitative Characterization of Organic Matters with Different Occurrences in Argillaceous Source Rocks: A Case of Shahejie Formation, Dongying Sag. Xinjiang Petroleum Geology, 2018, 39(4): 416-423. (in Chinese with English Abstract)

Zhou W D, Xie S Y, Bao Z Y, . Chemical Compositions and Distribution Characteristics of Cements in Longmaxi Formation Shales, Southwest China. Journal of Earth Science, 2019, 30(5): 879-892.