Dynamic evolution characteristics of the “source-reservoir” integration of gray marl and its geological significance to unconventional gas: Insights from pyrolysis experiments

作     者：Zhang-Hu Wang Zhong-Liang Ma Lun-Ju Zheng Jun-Yu Wang Zhi-Gang Wen Chen-Yang Si 

作者机构：Cooperative Innovation Center of Unconventional Oil and GasYangtze UniversityWuhanHubei430100China Key Laboratory of Oil and Gas Resources and Exploration TechnologyMinistry of EducationCollege of Resources and EnvironmentYangtze UniversityWuhanHubei430100China Wuxi Research Institute of Petroleum GeologySinopec Exploration and Production Research InstituteWuxiJiangsu214126China State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective DevelopmentWuxiJiangsu214126China School of Metallurgy and EnvironmentCentral South UniversityChangshaHunan410083China 

出 版 物：《Petroleum Science》 (石油科学（英文版）)

年 卷 期：2023年第20卷第2期

页      面：705-720页

核心收录：

学科分类：0820[工学-石油与天然气工程] 070902[理学-地球化学] 081803[工学-地质工程] 0709[理学-地质学] 07[理学] 0817[工学-化学工程与技术] 0828[工学-农业工程] 08[工学] 0818[工学-地质资源与地质工程] 0903[农学-农业资源与环境] 0703[理学-化学] 

基　　金：supported by the National Natural Science Foundation of China(42072156,U19B6003) the Open Foundation of Cooperative Innovation Center of Unconventional Oil and Gas,Yangtze University,China(No.UOG2022-18) 

主　　题：Residual oil Organic pores Porosity Sepiolite Hydrocarbon generation 

摘      要：The marl–limestone rhythmic strata of the Permian Maokou Formation have been identified as hosts of unconventional gas reservoirs with “source–reservoir integration. The lack of research on the pore structure evolution of organic-rich carbonate rock restricts gas exploration of these strata. Here, pyrolysis experiments were performed on the Mao-1 carbonate to simulate hydrocarbon generation, expulsion and diagenesis in gray marl from low maturity to overmaturity. The pore structure of this marl is dominated by mesopores and macropores, and the proportion of macropores increases gradually with temperature. The macropores are mainly pores in the organic matter and shrinkage microcracks. Additionally, micropores and mesopores, dominated by clay mineral interlayer pores and pyrite intergranular pores, are developed in the high mature stage and subsequently compressed in the overmature stage. The main contributors to the specific surface area are micropores and mesopores, which are conducive to natural gas adsorption. After the same pyrolysis treatment, the available porosity of grey marl is higher than that of marine/lacustrine shales, and exhibits an obvious decrease in the low mature–mature stage. These suggest that the abundant residual oil generated blocked the organic and inorganic pores in the gray marl, providing a pivotal material foundation for the gas generation. Micropores and mesopores developed during the high mature stage ensure the gas accumulation and preservation. The above indicate the organic-rich carbonate at the high mature–overmature stage (Ro = 1.7%–2.5%) in the Sichuan Basin may be a favorable exploration horizon for unconventional oil and gas.