Study On Prediction Of Coal Powder In The Production Mechanism Of CBM

CBM production is a process of drainage gas recovery and decreasing pressure continuously. At the beginning of CBM production, the reservoir pressure is mainly decreased by drainage. The drawdown pressure and fluid action during CBM production can damage coal bed and make coal powder occur because of its poor cementation, frangibility, and collapsibility. During transporting with fluid flow, coal powder can subside and stop in the fissure, which lower permeability of coal bed and influence the decrease of overall pressure. The coal powder in pump barrel can wear down pump barrel and plunger piston, the pump efficiency will be reduced. In the stable production period and the production decline stage, the sedimentation of coal powder in the well hole can seriously impact the pump efficiency for the decrease of water yield and power. Coal powder can even bury pipe column and stuck pump. Therefore, the production of coal powder can seriously influence the whole mining benefit, and the study on production mechanism of coal powder in the cbm production is significant to the CBM developmentFirst, through the study of the mechanism of pulverized coal output of each stage in the process of coalbed methane drainage and gas. Build the coal bed methane dual medium mathematical model based on the basic physical properties of the coal reservoir and mechanical properties.Then choose the appropriate application of raw coal seams of rock failure criterion to calculate the critical pressure of wells wall, combined with quantitative drainage and gas pressure drop calculated the discharge time of borehole wall pulverized coal, Meanwhile based on the theory of elastic deformation and plastic deformation calculate the stress distribution of coal seam, According to the size of the plastic deformation of coalbed methane wells launch a pulverized coal reservoir radius. By the time of the pulverized coal and coal-bed methane radius theory using MATLAB prepared pulverized coal bed methane recovery discharge prediction software for subsequent us. Finally, using the ABAQUS finite element analysis software for pulverized coal out of time and pulverized coal seam radius simulation then compare with theoretical calculation. The prediction of the pulverized CBM wells has a positive effect on developing appropriate row on different production systems,improving the operating life of the pump, extending the inspection of the pump cycle, ensuring continuous preduction, reducing the number of workover. At the same time it can reduce the cost of development of coalbed methane and increase economic efficiency,and has important significance to enhance the large-scale commercial exploitation of coalbed methane.