Geological Characteristic Of Coalbed Methane And Evaluation Of Workability In Enhong Block Of Eastern Yunnan Province

As an important basic work,the study of coalbed methane geological characteristics and recoverability is of great significance for the exploration and exploitation of coalbed methane.Based on the characteristics of coalbed methane reservoir and the characteristics of gas bearing,Yunnan enhong area is used as the research object with geological characteristics of special coal bed gas of high stress,multi seam and complex coal body structure,the distribution characteristics of coal structure are analyzed,the partition of coal structure is divided,the prediction method of gas content is determined,the main controlling factors of gas bearing property are revealed,and the geological resources of coal bed gas are calculated.Combined with the current situation of CBM exploration and development in the study area,analogy method,isothermal adsorption method and numerical simulation method are choosed to calculate the recovery rate of different zoning.According to two kinds of CBM production schemes based on different tectonic zoning,the recoverability of CBM resources is evaluated combining recovery efficiency and recoverable resources.It is found that the structural complexity and thickness of coal seam are the main controlling factors of the coal structure in the study area.According to the fractal dimension of the fault and thickness contour map,the plane distribution characteristics of coal body structure in the main coal seam are predicted,and the plane structure partition is divided according to the proportion of type I+II coal.Based on the characteristics of coal ash yield and coal rank change in the study area,the isothermal adsorption gas saturation method is selected to predict the gas content.The abundance of CBM geological resources is 82 million m~3/km~2,the depth of 1000m accounts for 79.67%of shallow geological resources,and the proportion of coal resources of type I+II is about 90.24%.It shows good resource potential and coalbed methane production conditions.The coal seam gas recovery is calculated by analogy method,isothermal adsorption method and numerical simulation method.In the end,the CBM Recovery yield of different structural zoning is determined on the basis of the highest reliability and authenticity.The unfavorable zone is 3.96~6.77%,the favorable area is 16.10~25.33%,and the favorable area is 37.42%.The CBM recoverable resources in the study area are 15 billion 179 million m~3,the main coal seam account for 58.23%,the recoverable resource abundance is 28 million m~3/km~2,and the main coal seam account for 60.71%.Through numerical simulation,new cluster well production is adopted in unfavorable areas,and progressive production is adopted in favorable areas and more favorable areas.The single coal bed gas well has higher daily gas production and longer stable production period.Considering the recoverable resources of coalbed methane,recovery and production conditions of single well,the research area shows a good prospect of coalbed methane exploitation.