Different stress sensitivity of different coal rank reservoir permeability and its effect on the coalbed methane output

According to the east Ordos Basin coal rank of different water saturation of coal reservoir stress sensitivity lab experiments,the influence of coal reservoir permeability dynamic change rules on the coalbed methane production was studied. Experimental results confirm that medium high rank coal reservoir permeability decreases in the rule of negative exponent function along with the increasing effective stress. Once the effective stress less than 5 MPa,the coal reservoir permeability with the increasing effective stress quickly fells by 73% ~ 95%,average 87%,indicating strongest stress sensitivity; the effective stress ranges from 5 to 10 MPa,permeability rapidly decreases by 5% ~ 18% along with increasing effective stress,average 10. 4%,showing strong stress sensitivity; When the effective stress is higher than 10 MPa,the decline in permeability with the increase of effective stress representing weak stress sensitivity. The stress sensitivity in effective stress of high rank coal is lower than that of low rank coal. With increasing of water saturation of coal samples,coal reservoir permeability in stress sensitivity enhances gradually,the production rules of CBMWells was proposed in processing of slowly depressurizing-continuous producing work flow,based on the reservoir permeability dynamic change law,in order to attain coalbed methane the maxumum output.