Pore Characteristics and Influencing Factors of Marine and Lacustrine Shale in the Eastern Sichuan Basin, China

Jianglin He (), Lixia Zhu, Ankun Zhao, Dong Wang, Zhen Qiu and Ping Yang
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Jianglin He: Chengdu Center of Geological Survey, China Geological Survey, Chengdu 610082, China
Lixia Zhu: Chengdu Center of Geological Survey, China Geological Survey, Chengdu 610082, China
Ankun Zhao: Chengdu Center of Geological Survey, China Geological Survey, Chengdu 610082, China
Dong Wang: Chengdu Center of Geological Survey, China Geological Survey, Chengdu 610082, China
Zhen Qiu: PetroChina Research Institute of Petroleum Exploration and Development, China National Petroleum Corporation, Beijing 100083, China
Ping Yang: Chengdu Center of Geological Survey, China Geological Survey, Chengdu 610082, China

Energies, 2022, vol. 15, issue 22, 1-19

Abstract: Although almost all the shale gas in China is exploited from marine shale (Wufeng–Longmaxi Formation) in Sichuan Basin and several prolific wells, it has also been obtained in Jurassic lacustrine shale. However, the reservoir conditions of the lacustrine shale are not well understood, which has impeded a breakthrough regarding lacustrine shale gas in Sichuan Basin. To probe the reservoir conditions of the lacustrine shale in Sichuan Basin, we take the Wufeng–Longmaxi shale and Dongyuemiao shale sampled from wells and outcrops as examples. A series of experiments were conducted, including TOC, XRD, FE-SEM, N 2 adsorption, Micro-CT, vitrinite reflectance and bitumen reflectance. The results show that the pores in marine shale are mainly composed of organic-matter-hosted pores (OM pores). However, in the lacustrine shale, the pores are mainly composed of dissolution pores and intergranular pores. The marine shale is characterized by small-caliber and large-volume pores in which cluster pores are levitated in the shale as kites and connected by past channels. However, in the lacustrine shale, the cluster pores and the past channels are mainly arranged according to the flow channels in the vertical direction. The arrangement of the pores in the marine shale is obviously deformed by compaction. The lacustrine shale is characterized by under-compaction. It can be deduced that the sweet spots for lacustrine shale gas are likely located at the areas characterized by under-compaction resulting from fluid pressure conducted upward, such as the hinge zone of syncline or the core of anticline overlap on the gas reservoirs.

Keywords: shale gas; pore structure; marine shale; lacustrine shale; shale reservoirs (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
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