Geochemical Characteristics of Mature to High-Maturity Shale Resources, Occurrence State of Shale Oil, and Sweet Spot Evaluation in the Qingshankou Formation, Gulong Sag, Songliao Basin

Bo Gao, Zihui Feng, Jinglan Luo, Hongmei Shao, Yubin Bai (), Jiping Wang, Yuxuan Zhang, Yongchao Wang and Min Yan
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Bo Gao: State Key Laboratory of Continental Shale Oil, Daqing 163002, China
Zihui Feng: State Key Laboratory of Continental Shale Oil, Daqing 163002, China
Jinglan Luo: State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an 710069, China
Hongmei Shao: State Key Laboratory of Continental Shale Oil, Daqing 163002, China
Yubin Bai: School of Earth Sciences and Engineering, Xi’an Shiyou University, Xi’an 710065, China
Jiping Wang: State Key Laboratory of Continental Shale Oil, Daqing 163002, China
Yuxuan Zhang: School of Earth Sciences and Engineering, Xi’an Shiyou University, Xi’an 710065, China
Yongchao Wang: State Key Laboratory of Continental Shale Oil, Daqing 163002, China
Min Yan: State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an 710069, China

Energies, 2024, vol. 17, issue 12, 1-23

Abstract: The exploration of continental shale oil in China has made a breakthrough in many basins, but the pure shale type has only been found in the Qingshankou Formation, Gulong Sag, Songliao Basin, and the evaluation of shale oil occurrence and sweet spot faces great challenges. Using information about the total organic carbon (TOC), Rock-Eval pyrolysis, vitrinite reflectance (Ro), kerogen elemental composition, carbon isotopes, gas chromatography (GC), bitumen extraction, and component separation, this paper systematically studies the organic geochemical characteristics and shale oil occurrence at the Qingshankou Formation. The G1 well, which was cored through the entire section of the Qingshankou Formation in the Gulong Sag, was the object of this study. On this basis, the favorable sweet spots for shale oil exploration are predicted. It is concluded that the shale of the Qingshankou Formation has high organic heterogeneity in terms of organic matter features. The TOC content of the source rocks in the Qingshankou Formation is enhanced with the increase in the burial depth, and the corresponding organic matter types gradually changed from Ⅱ 2 and Ⅱ 1 types to the Ⅰ type. The distribution of Ro ranges from 1.09% to 1.67%, and it is the mature to high-mature evolution stage that generates a large amount of normal crude oil and gas condensate. The high-quality source rocks of good to excellent grade are mainly distributed in the Qing 1 member and the lower part of the Qing 2 member. After the recovery of light hydrocarbons and the correction of pyrolytic heavy soluble hydrocarbons, it is concluded that the occurrence state of shale oil in the Qingshankou Formation is mainly the free-state form, with an average value of 6.9 mg/g, and there is four times as much free oil as adsorbed oil. The oil saturation index (OSI), mobile hydrocarbon content, Ro, and TOC were selected to establish the geochemical evaluation criteria for shale oil sweet spots in the Qingshankou Formation. The evaluation results show that interval 3 and interval 5 of the Qingshankou Formation in the G1 well are the most favorable sections for shale oil exploration.

Keywords: oil content; organic geochemistry; Qingshankou Formation; Gulong Sag; Songliao Basin (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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