Differential accumulation characteristics and production of coalbed methane/coal-rock gas: A case study of the No. 8 coal seam of the Carboniferous Benxi Formation in the Daji block, Ordos Basin, NW China

作者：Lihong Zhou, Yong Li, Yong Li, Rong Ding, Xianyue Xiong, Wei Hou, Yunguo Li, Yunguo Li, Hui Ma, Haijiao Fu, Yi Du, Weiqi Zhang, Zhitong Zhu, Zhuangsen Wang · 发表于：Petroleum Exploration and Development · 年份：2025 · DOI：10.1016/s1876-3804(25)60609-4 · 被引用次数：14 · 研究领域：Hydrocarbon exploration and reservoir analysis、Coal Properties and Utilization、Methane Hydrates and Related Phenomena

Based on the coalbed methane (CBM)/coal-rock gas (CRG) geological, geophysical, and experimental testing data from the Daji block in the Ordos Basin, the coal-forming and hydrocarbon generation & accumulation characteristics across different zones were dissected, and the key factors controlling the differential CBM/CRG enrichment were identified. The No. 8 coal seam of the Carboniferous Benxi Formation in the Daji block is 8–10 m thick, typically overlain by limestone. The primary hydrocarbon generation phase occurred during the Early Cretaceous. Based on the differences in tectonic evolution and CRG occurrence, and with the maximum vitrinite reflectance of 2.0% and burial depth of 1 800 m as boundaries, the study area is divided into deeply buried and deeply preserved, deeply buried and shallowly preserved, and shallowly buried and shallowly preserved zones. The deeply buried and deeply preserved zone contains gas content of 22–35 m 3 /t, adsorbed gas saturation of 95%–100%, and formation water with total dissolved solid (TDS) higher than 50 000 mg/L. This zone features structural stability and strong sealing capacity, with high gas production rates. The deeply buried and shallowly preserved zone contains gas content of 16–20 m 3 /t, adsorbed gas saturation of 80%–95%, and formation water with TDS of 5 000–50 000 mg/L. This zone exhibits localized structural modification and hydrodynamic sealing, with moderate gas production rate. The shallowly buried and shallowly preserved...