Subdivision of Gas-Bearing Systems and Sequence Stratigraphic Analysis in the Eastern Pingdingshan Mining District

To investigate the gas-bearing systems in the eastern Pingdingshan mining district, this study focuses on the Paleozoic succession and integrates sedimentology, sequence stratigraphy, well-log analysis, and organic geochemistry to delineate the sequence framework and partition the gas-bearing systems within the Shanxi and Xiashihezi formations. Distinct segmental variations in reservoir pressure gradient, gas content, and methane carbon isotopes reveal three independent gas-bearing systems: System I, extending from the base of the Shanxi Formation to the base of the Xiashihezi Formation; System II, hosted by the No. 3 and No. 4 coal seams of the Xiashihezi Formation; and System III, associated with the No. 5 and No. 6 seams of the same formation. System I is linked chiefly to delta plain and tidal flat environments, whereas Systems II and III are related to distributary channel and distributary bay settings on the delta plain. Within the established sequence stratigraphic framework, we evaluate the controls exerted by sequence architecture and depositional environment on coal accumulation and summarize the coal-forming patterns characteristic of each depositional setting in the study area.