Exploration potential of middle jurassic shale gas in the Yabulai Basin, Northwest China

The Jurassic continental shale strata are widely distributed across several small- to medium-sized sedimentary basins in northwest China. Currently, shale gas exploration and development in China are primarily concentrated in large basins, while long-term exploration and evaluation of small- and medium-sized basins with unique geological characteristics remain insufficient. Focusing on the J 2 x and J 2 q shales of the Middle Jurassic in the Yabulai Basin in northwestern China, this study examines their gas generation potential, gas genesis, reservoir properties, and gas content, ultimately identifying favorable areas for shale gas exploration. The findings indicate that the J 2 x and J 2 q shales have high organic matter abundance, favorable organic types, and moderate maturity, thereby possessing significant potential for gas generation. The adsorbed gas from these shales is classified as low-maturity gas of organic origin. Both the J 2 x and J 2 q shales exhibit significant potential for hydraulic fracturing. Their pores structures are primarily composed of mesopores and macropores, with comparable permeability and gas adsorption capacities. Under in-situ temperature and pressure conditions, the total gas content of the J 2 x shale ranges from 1.52 to 3.43 m 3 /t, while that of the J 2 q shale ranges from 1.84 to 2.60 m 3 /t. Vertically, the shale gas exploration potential of the J 2 x formation is generally higher than that of the J 2 q formation. Horizontally, the exploration potential is highest in the western and eastern regions and lower in the central region. These results provide a geological reference for shale gas exploration and development in other similar small- to medium-sized basins, both domestically and internationally.