Geochemical and geological characteristics of Permian Lucaogou Formation shale of the well Ji174, Jimusar Sag, Junggar Basin, China: Implications for shale oil exploration

Abstract

Abundant shale oil resources were recently found in the organic‐rich Permian Lucaogou (P2l) Formation shale, Jimusar Sag, Junggar Basin. Although some scholars have conducted some researches on the basic geochemical characteristics of the Lucaogou Formation shale, it is not enough to effectively guide the shale oil exploration in the area. This is because during the exploration process of shale oil, besides the basic geochemical characteristics of shale, its mineral composition, physical properties, and oil‐bearing characteristics are all very important evaluation parameters. To systematically evaluate the favourable shale oil exploration sections in the Lucaogou Formation, 265 pieces of shale cores were sampled from well Ji174 in this study. Besides the basic geochemical characteristics of the 265 pieces of cores, the mineralogical, petrophysical, and oil‐bearing characteristics were also analysed. Results show that the shale has abundant organic matter (average total organic carbon 3.51%, average petroleum generation potential 15.67 mg/g), dominated by Type II1 and Type II2 kerogen, and has entered the early‐mature to mature stage. The Upper Member of the Lucaogou Formation has relatively higher organic matter and organic matter type is relatively more oil prone compared to the Lower Member; however, organic matter thermal maturity is lower. The P2l Formation shale is characterized by high carbonate minerals and low clay minerals, and when considering mineralogical brittleness, both the Upper and Lower members are ideally fracturable in shale oil development. The P2l Formation shale has a wide porosity range (1.1–13.9%), and the Lower Member's porosity is slightly greater. The inversion of shale porosity in the P2l Formation is controlled by the differentiated mineral composition. The oil saturation index values of the Lower Member shale are significantly greater than the Upper Member shale. From the above, the Lower Member of the P2l Formation shale is ideally suited and has greater shale oil potential in the Jimusar Sag, Junggar Basin, especially in the depth intervals of 3,255–3,272, 3,282–3,298, and 3,317–3,334 m in the well Ji174.

Geochemical and geological characteristics of the Jurassic continental black shale in the Southwestern Depression of Tarim Basin

“…Results of the former show that porosity is between 3.72% and 8.39% (average 5.22%) and permeability between 0.002 and 5.68 mD (average 1.43 mD). The results of gas testing porosity are higher than the results obtained by mercury injection analysis, and this is mainly related to the mineral composition and pore throat distribution of shale (T. Hu et al, ; H. Tian, Zhang, Liu, & Zhang, ).…”

“…Although a certain amount of progress had been made, large‐scale industrial production of shale gas has not yet begun in China because of delays in development and the need to determine particular geological issues. Most of the shale in the USA is marine deposits, whereas the main type in the Eastern and Northwestern China is continental deposits (Gao et al, ; T. Hu, Pang, Wang, & Jiang, ; T. Hu, Pang, Yu, Wang, & Pang, ; T. Hu, Pang, Wang, et al, ; W. H. Li, ; J. J. Li, Wang, et al, ; J. J. Li, Yin, et al, ; M. Wang, Sherwood, et al, ; M. Wang, Wilkins, et al, ; W. Wang, Xue, Tian, Wilkins, & Wang, ). Therefore, large differences exist between the geological and geochemical characteristics of the shale in both countries, and it is not possible for China to completely copy the exploration experiences associated with shale gas in the USA.…”

“…Although a certain amount of progress had been made, large-scale industrial production of shale gas has not yet begun in China because of delays in development and the need to determine particular geological issues. Most of the shale in the USA is marine deposits, whereas the main type in the Eastern and Northwestern China is continental deposits (Gao et al, 2013;T. Hu, Pang, Wang, & Jiang, 2017;T.…”

Quality, hydrocarbon generation, and expulsion of the Eocene Enping Formation source rocks in the Wenchang Depression, western Pearl River Mouth Basin, South China Sea

“…When oil and gas are not expelled, the greatest value is considered as the maximum hydrocarbon generation potential HCI o (Guo et al., 2013; Hu et al., 2017b). The Ro value at the beginning of reduction represents the hydrocarbon expulsion threshold of source rocks, and the subsequent hydrocarbon generation potential can be called the residual hydrocarbon generation potential HCI p (Hu et al., 2017a).…”

Effects of diagenesis on natural fractures in tight oil reservoirs: A case study of the Permian Lucaogou Formation in Jimusar Sag, Junggar Basin, NW China

“…The Lucaogou Formation is characterized by its wide span in the horizontal direction and extensive depth in the vertical direction. Semideep and deep lacustrine mudstone are the major hydrocarbon source rocks with a high abundance of total organic matter (TOC ≥2%) and a considerable hydrocarbon generation potential (S 1 + S 2 ≥ 20 mg/g), which guarantee continuous hydrocarbon generation from source rocks (Hu et al, 2018;Hu et al, 2017;Kuang et al, 2014;Kuang, Hu, Wang, Wu, & Wu, 2013;. The tight reservoirs, dominated by dolomitic siltstone/fine sandstone, argillaceous siltstone/fine sandstone, and sandy dolomite, are continuously distributed over a large area (Kuang et al, 2012;Z.…”