Key geological issues and main controls on accumulation and enrichment of Chinese shale gas

By analyzing geological characteristics of shale gas in Southern China and the United States, main factors controlling the accumulation and key issues in the exploration and development of shale gas in China have been examined. The geological characteristics of shale gas in China include multi-stage tectonic evolution, complex structure types, abundant faults, small continuous distribution area of shale formations, and no corresponding relationship between current thermal evolution degree and current burial depth of two main sets of shale formations (the Cambrian and Silurian). According to the analysis of the factors affecting shale gas enrichment such as fracture, tectonic type, shale gas migration, and gas content etc, the enrichment mechanisms of shale gas in China are: sedimentary facies and preservation condition are the main reservoir-controlling factors affecting the accumulation of shale gas, and structure types and tectonism are the main factors controlling the enrichment of shale gas in China; The former factors define shale gas plays, and the latter ones determine the position of sweet spots. The future research directions of shale gas in China are: firstly, contrary to the shale gas development in the United States, shale gas exploration and development in China should extend from the overpressure to normal pressure, and even low pressure areas; secondly, shale gas exploration in the Sichuan basin should extend from middle-deep to deep formations, studies should be done on the shale gas enrichment mechanism and accumulation models in formations deeper than 4 000 m, and horizontal well fracturing technology for these formations; thirdly, the development of transitional facies and continental facies shale gas should be brought along by drawing on exploration and development experience of marine shale gas.