Influencing mechanism of saline sediments on pore system formation and evolution in terrestrial shales

作     者：Yu-Qi Wu Fu-Jie Jiang Di Chen Jing Guo Chen-Xi Zhu Zhao Zhao Zhuo-Yue Yan Tao Hu 

作者机构：State Key Laboratory of Petroleum Resources and ProspectingChina University of PetroleumBeijing102249China College of GeosciencesChina University of PetroleumBeijing102249China Tianjin Branch of CNOOC China LtdTianjin300452China 

出 版 物：《Petroleum Science》 (石油科学（英文版）)

年 卷 期：2023年第20卷第6期

页      面：3280-3300页

核心收录：

学科分类：081803[工学-地质工程] 08[工学] 0818[工学-地质资源与地质工程] 

基　　金：funded by the National Natural Science Foundation of China(41872128) Postdoctoral Foundation of China University of Petroleum(Beijing)(ZX20220102) 

主　　题：Bohai bay basin Dongpu depression Pore evolution Salt-associated shale Halite mineral 

摘      要：The majority of oil and gas resources in the world are related to saline sediments, which mainly occur in sedimentary strata in the form of cap rocks or salt-associated shales. A large number of shale oil resources have been discovered in the saline shale sediments of the Cenozoic terrestrial lake basin in China. The hydrocarbon generation ability and the reservoir capacity of shale control the oil and gas generation. The reservoir capacity is mainly characterized by pore type, structure and porosity. Most of China’s shale oil and gas resources belong to salt-bearing formations. The role of gypsum-salt rocks in the formation and evolution of organic matter (OM) in such formations has received extensive attention. However, systematic understanding is lacking. Research on the pore formation and evolution in shale under the action of gypsum-salt rock sediments is especially weak. Taking the shales in the third member of the Shahejie Formation (Es_(3)) of the Bohai Bay Basin as an example, the influence of halite on the formation and evolution process of pores was studied in this paper. The results show that halite and gypsum minerals were associated with OM, which made them more likely to develop OM pores. The samples with a high halite mineral content (HC) are more developed regarding the pore volume and specific surface area than those with a low HC. The formation of thick salt rocks is influenced by factors of deep thermal brine upwelling, sea erosion and arid environments. The frequent alternation between humid and arid environments led to the outbreak and death of organisms and the precipitation of gypsum-salt rock, which formed the simultaneous deposition of OM and halite minerals. Finally, we have established a model of shale pore evolution under the participation of the gypsum-salt rock, and halite minerals contribute to pore development in both Stage II and Stage IV. This study provides strong microscopic evidence for the pore system formation and evolution in