Nano-Scale Pore Structure Characterization and Its Controlling Factors in Wufeng and Longmaxi Shale in the Zigong Area, Southwest Sichuan Basin

Zhongcheng Li, Zhidong Bao, Hailong Wang (), Xiaohua Zhu, Hongxue Wang, Zhenchang Jiang and Taohua He
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Zhongcheng Li: Research Institute of Exploration and Development, PetroChina Jilin Oilfield Company, Songyuan 138000, China
Zhidong Bao: College of Geosciences, China University of Petroleum-Beijng, Beijing 102249, China
Hailong Wang: Research Institute of Exploration and Development, PetroChina Jilin Oilfield Company, Songyuan 138000, China
Xiaohua Zhu: Research Institute of Exploration and Development, PetroChina Jilin Oilfield Company, Songyuan 138000, China
Hongxue Wang: Research Institute of Exploration and Development, PetroChina Jilin Oilfield Company, Songyuan 138000, China
Zhenchang Jiang: Research Institute of Exploration and Development, PetroChina Jilin Oilfield Company, Songyuan 138000, China
Taohua He: Hubei Key Laboratory of Petroleum Geochemistry and Environment, Yangtze University, Wuhan 430100, China

Energies, 2023, vol. 16, issue 21, 1-17

Abstract: The nano-scale pore systems in shale reservoirs control shale gas transportation and aggregation, which is of great significance for the resource evaluation of shale oil and gas and the selection of a “sweet spot”. Taking twelve marine shale samples from the Wufeng–Longmaxi Formation in the Zigong area, southwest Sichuan Basin, as the research target, we carried out a series of experiments, including total organic carbon (TOC) analysis, X-ray diffraction (XRD), gas adsorption (CO 2 + N 2 ), and mercury intrusion porosimetry (MIP), to study the full-scale pore structure characterization and controlling factors of pore volume and specific surface area. The results presented the following findings. (1) Marine shale samples from the target area are rich in organic matter, with an average TOC value of 3.86%; additionally, the mineral composition was dominated by quartz and clay minerals, with average contents of 44.1% and 31.4%, respectively. (2) The full-scale pore size distribution curves of pore volume developed multimodally, with the main peaks at 0.5 nm–2 nm, 3 nm–6 nm, and 700 nm–2.2 um; moreover, the full-scale pore size distribution curves of a specific surface area developed unimodally, with the main peak ranging from 0.5 nm to 1.2 nm. (3) Pore volume was mainly contributed by mesopores and macropores, with an average contribution of 46.66% and 42.42%, respectively, while the contribution of micropores was only 10.91%. The specific surface area was mainly contributed by micropores and mesopores, with an average contribution of 64.63% and 29.22%, respectively, whereas the contribution of micropores was only 6.15%. (4) The TOC content mainly controlled the pore volume and specific surface area of micropores and mesopores, while the clay and feldspar content generally controlled the pore volume and specific surface area of macropores. Additionally, the quartz content had an inhibitory effect on the development of all pore types. These results will help researchers understand the laws of gas accumulation and migration.

Keywords: full-scale pore structure; marine shale; low-temperature gas adsorption; mercury intrusion porosimetry; Wufeng–Longmaxi formation (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: 2023
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