Research On Reservoir Characteristics And Recoverability Of CBM Resources In Songhe Mine Field, Guizhou Province

According to the exploration and development demonstration project of coalbed methane(CBM) in Songhe Mine Field, West Guizhou. Discussed the reservoir and development characteristics, it was summarized on the appropriate recoverability research methods under different geological and development conditions based on the study of the various recovery methods. It is reasonable to choose recoverability research methods according to the geological and development condition in the study area, and then calculated CBM resources recovery and recoverable resources in the study area. From the Angle of the recovery, obtained the development pattern and process with high recovery efficiency through numerical simulation, so as to achieve the aim of optimization process and guiding the production. The main results as follows:(1) CBM resources mainly occured in the longtan multiple coal seams with low permeability and thin to thick features in Songhe Mine Field. Gas content was 6.46~20.99 m3/t, gas saturation was greater than 70%, geothermal gradient was 3.0~5.5℃/hm, and pressure coefficient was 1.08~1.40, the coal reservoir possessed the characterwastics of high gas content, high to supersaturated, high temperature and overpressure, which showed that CBM geology recoverability was well.(2) Songhe Mine Field belonged to the evaluation area with high degree of geological understanding, exploration and low degree of development, so it should be mainly used isothermal adsorption method and numerical simulation method to determine the recovery. The recovery of Songhe Mine Field were 41%~52%, 64.3%~69.8% and 43.5%~44.2% by using analogy method, isothermal adsorption curve method and numerical simulation method. The conclusion after comprehensive analysis was that CBM recovery of the study area should be 45%~50%, and CBM recoverable resources were 1.545~1.717×109 m3. CBM recoverability was well, and the potential of resources development was tremendous.(3) Development mode and process was optimized by the numerical simulation software COMET3. The effect of combining first with second layer to mining was the best, and recovery could reach 45.1%. Well pattern arrangement scheme of 300 m×250 m was optimal, and recovery was 42.7%. The fracture half length of 120 m(displacement 8 m3 / min) was optimal, and recovery was 46.3%. The recommended construction displacement was 8.0 ~ 10.0 m3 / min. The daily gas production was optimal when flow pressure drop speed was 0.025 MPa/d, and recovery could reach 45.8%, compared with the actual flow pressure drop speed 0.022 MPa/d, flow pressure drop speed could be appropriately improved in Songhe Mine Field.