Shale Oil Enrichment Mechanism of the Paleogene Xingouzui Formation, Jianghan Basin, China

Qiqi Li, Shang Xu, Liang Zhang, Fengling Chen, Shiqiang Wu and Nan Bai
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Qiqi Li: Key Laboratory of Tectonics and Petroleum Resources, Ministry of Education, China University of Geosciences, Wuhan 430074, China
Shang Xu: Shandong Provincial Key Laboratory of Deep Oil & Gas, China University of Petroleum (East China), Qingdao 266580, China
Liang Zhang: Exploration and Development Research Institute, Sinopec Jianghan Oilfield Company, Wuhan 430074, China
Fengling Chen: Exploration and Development Research Institute, Sinopec Jianghan Oilfield Company, Wuhan 430074, China
Shiqiang Wu: Exploration and Development Research Institute, Sinopec Jianghan Oilfield Company, Wuhan 430074, China
Nan Bai: Key Laboratory of Tectonics and Petroleum Resources, Ministry of Education, China University of Geosciences, Wuhan 430074, China

Energies, 2022, vol. 15, issue 11, 1-18

Abstract: Organic-rich lacustrine shales are widely developed in China, and they have long been simply regarded as homogeneous source rocks, which restricts the understanding of intrasource oil accumulation. At present, the study of the LXF (Lower Member of the Xingouzui Formation) in the Jianghan Basin as an unconventional oil reservoir is still in its infancy, and the hydrocarbon accumulation mechanism is still unclear. Geochemical and mineralogical studies were carried out on a suite of samples from the 100-m-thick sequence, i.e., LXF II Oil Bed, by using XRD, SEM, MICP, and Rock-Eval pyrolysis. The results show that the II Oil Bed is rich in carbonate and poor in clay, so it shows a good fracturing tendency. The high degree of heterogeneity in mineral composition leads to frequent interbedding of different lithofacies. In the II Oil Bed, intercrystalline pores, interparticle pores, and intraparticle pores are developed, and micro-fractures are often observed. However, the main pore types, pore size distribution, and connectivity are quite different among lithofacies, and the carbonate-rich lithofacies have better reservoir capacity. The OM (organic matter) abundance of the II Oil Bed varies greatly and generally ranges from fair to very good. Coupled with its early-mature to mature Type II OM, it is considered to have the characteristics required for oil generation. Comprehensive analysis shows that the II Oil Bed has good shale oil exploration prospects, and the enrichment of shale oil in the sequence is the result of multiple factors matching. Firstly, high organic matter abundance is the material basis for shale oil enrichment. Secondly, thermal maturity is a prerequisite, and the difference in burial depth leads to the differential enrichment of shale oil in different areas. Thirdly, pores and micro-fractures developed in shale not only provide space for hydrocarbon storage, but also form a flow-path network. Finally, multi-scale intrasource migrations are key processes ranging from the scale of lithofacies to the intervals, which further results in the differential shale oil enrichment in different lithofacies and intervals. Considering the hydrocarbon generation capacity and reservoir quality, the prospective depth for shale oil exploration in the study area is >1350 m. The findings of this study can help in the better-understanding of the shale oil enrichment mechanism, and the optimization of future exploration strategies.

Keywords: shale oil; enrichment mechanism; lacustrine source rocks; Jianghan 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: 2022
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (4)

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