Study on the Formation Mechanism of Shale Roof, Floor Sealing, and Shale Self-Sealing: A Case of Member I of the Upper Ordovician Wufeng Formation–Lower Silurian Longmaxi Formation in the Yangtze Region
Year: 2021
Type: article
Abstract: Similar to North America, China has abundant shale resources. Significant progress has been made in the exploration and exploitation of shale gas in China since 2009. As the geological theory of unconventional oil and gas was proposed, scientists have started researching conditions for shale gas preservation. The shale roof and floor sealing and the shale self-sealing are the critical objects of such research, which, however, are still in the initial stage. This article studies the formation mechanism of shale roof and floor sealing and shale self-sealing by taking marine shales from Member I of the upper Ordovician Wufeng Formation–lower Longmaxi Formation in the upper Yangtze region as the research object. Analyses were performed on the TOC content, mineral composition, and porosity, as well as the FIB-SEM, FIB-HIM, and gas permeability experiments on the core samples collected from the marine shales mentioned above. The conclusions are as follows: for the sealings of shale roof and floor, the regional cap rocks, roof, and floor provide sealing for shales due to physical property differences. For the self-sealing of shales, the second and third sub-members of Member I of the Wufeng Formation–Longmaxi Formation mainly develop clay mineral pores which are dominated by macropores with poor connectivity, while the first sub-member of Member I of the Wufeng Formation–Longmaxi Formation mainly develops organic-matter pores, which are dominated by micropores and mesopores with good connectivity. Owing to the connectivity difference, the second and third sub-members provide sealing for the first sub-member, while the methane adsorption effect of shales can inhibit large-scale shale gas migration as it decreases the gas permeability; thus, the organic-rich shales from the first sub-member of Member I of the Wufeng Formation–Longmaxi Formation provides sealing for itself.
Source: Frontiers in Earth Science
Institutions: China University of Petroleum, Beijing, Chinese Academy of Geological Sciences, Southwest Petroleum University, University of Utah, China University of Geosciences, State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, China Geological Survey, Research Institute of Petroleum Exploration and Development, Exploration and Development Research Institute of PetroChina Southwest Oil & Gas Field Company (China), PetroChina Southwest Oil and Gas Field Company (China), China National Petroleum Corporation (China), Southwest University of Science and Technology
Language: English
Subfield: Mechanics of Materials
Field: Engineering
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,950
OpenAlex ID: W4200208458