Analysis of shale gas resource exploration potential of Yan'an Formation in northern Huangling mining area of Ordos basin

Ordos basin is one of the important energy resource basins in China. The second and third members of Jurassic Yan'an Formation in northern Huangling mining area of the south-central Ordos basin contain a thick succession of continental dark mudstone. The minerals of the mudstone are dominated by quartz and clay minerals, with quartz content 43%~56%, clay content ranging 29%~33%. The total organic carbon (TOC) content of the mudstone is 1.63%~3.89%, the organic maturity is characterized by R_o of 0.59%~0.60%, and gas (CH₄) content is 0.25~0.85 m³/t. The isothermal adsorption test showed that gas adsorption capacity of the mudstones in Yan'an Formation had a positive correlation with TOC. The gas is biogenic and possessed the basic geological conditions of shale gas formation. The characteristics of the mudstone can be compared with New Albany Shale in Michigan basin and Antrim Shale in Illinois basin of America. In order to assess the shale gas resource potential of Yan'an Formation in northern Huangling mining area, the exploration data and laboratory experiment data were analyzed. A preliminary assessment of gas resources demonstrated that the mudstone in Yan'an Formation in northern Huangling mining area has broad distribution and big thickness, and is characterized by high TOC content and high gas production potential. On the whole, the shale gas potential is very good.