Abstract: In the Lianyuan Sag of the Xiangzhong Depression, Well Xiangye 1 was deployed and implemented to evaluate the geological conditions for accumulation of shale gas in the Permian Dalong Formation. It was the first shale gas parameter well with the Dalong Formation as the target layer. In this study, the geological conditions of shale targets in the Dalong Formation are
analyzed using data from drilling, cores, well logging, and lab test results from Well Xiangye 1, including the sedimentary characteristics,rock minerals composition, organic geochemical characteristics, reservoir physical properties, and gas-bearing properties of the Dalong Formation. The results show that the Dalong Formation shale in Well Xiangye 1 is developed in an anoxic and deep-water platform-basin sedimentary environment, which is conducive to the development of shale and the preservation of organic matter. The thickness of high-quality shale is great (shale thickness is 92.8 m with TOC greater than 2%), there is a high
abundance of organic matter (TOC ranges from 0.41% to 10.47%, with an average of 3.91%), and the thermal evolution degree is moderate (Ro ranges from 1.50% to 1.72%, with an average of 1.58%). The pore structure of the shale reservoir is dominated by mesopores and macropores, with micro-fractures developed. The brittleness index of the shale is high, and the difference in
two-dimensional principal stress is small, which is conducive to the formation of a complex fracture network by hydraulic fracturing.The combination of these parameters indicates that the basic geological conditions are favorable for accumulation of shale gas. However, the preservation conditions are the key factor affecting the gas-bearing properties of the shale. After entering the period of hydrocarbon generation, the Dalong Formation shale in Well Xiangye 1 experienced three distinct phases of tectonic uplift and denudation, which resulted in the current shallow burial depth of the shale and its proximity to the denudation area. Shale gas in synclinal structures was easily able to escape laterally, and the hydrocarbon generation rate of humic kerogen was relatively low; both factors affected the gas-bearing properties of shale in the Dalong Formation. The area far away from the denudation zone, with a wide and gentle structure and great burial depth, and with reverse faults developed in the wings, is more favorable for the accumulation of residual syncline type shale gas.