Accumulation Conditions and Gas Content Characteristics of the Lower Silurian in Northwestern Hunan, China

Abstract

The Lower Silurian marine shale is widely distributed in Northwestern Hunan and features in a large thickness of dark shale showed at outcrops. However, the accumulation conditions and gas content is unknown. The sedimentary facies, thickness and distribution, organic matter types and content, maturity, reservoir properties and gas content of the Lower Silurian black shale in Northwestern Hunan were investigated by field observation, sampling and experimental analysis. The results show that the black shales sedimentary environment is deep water continental shelf, with featured in abundant fossil. The burial depth of the Lower Silurian black shale is 0-3000 m, and its thickness is 10-40m while the average TOC is 1.0% and average Ro is 2.9%. For the disadvantaged sedimentary facies and shallow depth, the maximum gas content of the Lower Silurian black shale from well site desorption test is 0.59m3/t only, but the result of isothermal adsorption simulate test show that the Lower Silurian black shale have a good adsorption capacity, and can generate a large number of shale gas in Northwestern Hunan where better deposition conditions and suitable depth exist in.