Research On Geological Conditions Of Coal And Coalbed Methane In Late Permian,Shunan And Peripheral Areas

Shunan has rich resource of coal and CBM.It has good prospects for coalbed methane exploration and development in Shunan area.Base on analysing the existing geological data in Shunan,the coal seam and the ancient environment of the late Permian were detailed analyzed in Shunan Area through observing outcrops,identifying the thin sections,drawing single well phases and connected well phases.The study area can be divided into three sedimentary zones from west to east.The western part around Yanjin mainly consists of continental deposit.The western part around Junlian mainly consists of continental-marine deposit.The eastern part around Gulin-Xuyong mainly consists of marine deposit.The characteristics of coal seam mainly controlled by coal-forming environment.Coal-forming environment not only control the thickness and distribution of the coal seam,but also affect the physical properties of coal reservoirs by controlling coal macerals,coal type,mineral content,coal structure,coal phase and other aspect.The coal developed from delta environment is always thicker and have better continuity.With the increasing of vitrinite content,the coal cleat density and porosity gradually increased,coal reservoir was better.In the plane direction,sulfur content of marine sedimentary is higher than continental sedimentary.In the vertical direction,sulfur content of coal in the same area is positively correlated to the environmental background index.CBM reservoir and cap combination of the study area is divided into 4 types,such as beneficial combination,sub-beneficial combination,general combination and unfavorable combination.Gas content is positively correlated to the depth of coal seam.As the depth of coal seam get deeper,the gas content increases higher.The tectonic status of coal seam have impact on the gas content.It can be divided into 4 categories,such as Syncline,Anticline,Fold-overthrust structure,Extensional tectonics.It can be subdivided into 8 types.Controlled characteristics of hydrogeological conditions can be summarized as 3 types,the hydraulic sealed,the hydraulic jam-up and the hydraulic migration-escape.The hydraulic sealed and the hydraulic jam-up process are favorable of the coalbed methane accumulation.Conversely,the pattern of the hydraulic migration-escape leads to the coalbed methane escape and is unfavorable of the coalbed methane accumulation.Weak runoff–stranded hydrodynamic conditions with high salinity contributes to the preservation of coalbed methane.