Geological characteristics and exploration breakthroughs of coal rock gas in Carboniferous Benxi Formation, Ordos Basin, NW China

作者：Zhe Zhao, Wanglin Xu, Zhenyu Zhao, Shiwei Yi, Wei Yang, Yueqiao ZHANG, Yuanshi SUN, Weibo ZHAO, Yunhe SHI, Chunlin ZHANG, Jianrong Gao · 发表于：Petroleum Exploration and Development · 年份：2024 · DOI：10.1016/s1876-3804(24)60022-4 · 被引用次数：77 · 研究领域：Hydrocarbon exploration and reservoir analysis、Methane Hydrates and Related Phenomena、Coal Properties and Utilization

To explore the geological characteristics and exploration potential of the Carboniferous Benxi Formation coal rock gas in the Ordos Basin, this paper presents a systematic research on the coal rock distribution, coal rock reservoirs, coal rock quality, and coal rock gas features, resources and enrichment. Coal rock gas is a high-quality resource distinct from coalbed methane, and it has unique features in terms of burial depth, gas source, reservoir, gas content, and carbon isotopic composition. The Benxi Formation coal rocks cover an area of 16×104 km², with thicknesses ranging from 2 m to 25 m, primarily consisting of bright and semi-bright coals with primitive structures and low volatile and ash contents, indicating a good coal quality. The medium-to-high rank coal rocks have the total organic carbon (TOC) content ranging from 33.49% to 86.11%, averaging 75.16%. They have a high degree of thermal evolution (Ro of 1.2%–2.8%), and a high gas-generating capacity. They also have high stable carbon isotopic values (δ13C1 of –37.6‰ to –16‰; δ13C2 of –21.7‰ to –14.3‰). Deep coal rocks develop matrix pores such as gas bubble pores, organic pores, and inorganic mineral pores, which, together with cleats and fractures, form good reservoir spaces. The coal rock reservoirs exhibit the porosity of 0.54%–10.67% (averaging 5.42%) and the permeability of (0.001–14.600)×10−3 μm2 (averaging 2.32×10−3 μm2). Vertically, there are five types of coal rock gas accumulation and dissipation combin...