Evaluation methods and parameter assignments of shale gas resources: A case study of the Wufeng-Longmaxi Formation in the Middle Yangtze region

Abstract: The evaluation method for shale gas, which is a very important unconventional oil and gas resource, is different from that for conventional oil and gas resources. According to the accumulation mechanism and formation process, the volumetric method seems to be the best method for evaluating shale gas resources in consideration of research status in China. In this paper, based on the analysis of maturity of organic matter, depth, gas content, preservation condition, surface environment of shale of Wufeng-Longmaxi Formation in the Middle Yangtze region, in combination with the definition standard of shale gas by Ministry of Finance, the authors hold that the Enshi-Pengshui area is a favorable area for exploration and development. According to the volume method principle for computing the shale gas resources, the acreage, thickness and density of gas-bearing shale in this area are 5174 km2, 57 m, and 2.71 t/m3 respectively. In accordance with the conditional probability, the authors assigned conditional probabilities to uncertain parameters, which include such factors as organic carbon content, total porosity and gas saturation. Finally, the geological resources of shale gas in favorable areas of Wufeng-Longmaxi Formation are estimated to be at 5434.7×108 m3.