Main factors controlling marine shale gas enrichment and high-yield wells in South China: A case study of the Fuling shale gas field

The marine shale in South China is characterized by multiple layers, a wide distribution, and a large amount of resources. However, the characterization of the enrichment degree of marine shale gas and the main factors affecting the enrichment and high-yield wells are still unclear, which seriously affects the process of shale gas exploration and development in South China. We integrated a large amount of drilling data, core analysis data, seismic data as well as gas testing results from Fuling shale gas field to study the shale gas-bearing properties. The results suggest that any single parameter is insufficient to accurately characterize the gas-bearing properties. Consequently, we propose to integrate multiple parameters, including total hydrocarbon values, gas content, gas saturation, porosity/pore diameters, formation pressure coefficient and resistivity, to comprehensively evaluate shale gas content and determine the origins of shale gas enrichment for the lower section of Wufeng-Longmaxi Formation in the Fuling shale gas field. We infer that the depositional environment and shale reservoir characteristic are the major factors affecting the stratigraphic variation of shale gas enrichment. The differences of structural deformation and uplift and erosion in the later period are the main factors leading to differential enrichment in the lateral direction. In factors affecting high-yield well, the completion parameters such as the lateral placement and lateral length of horizontal wells are the major factors affecting the test production.