The Stress Sensitivity of Coal Bed Methane Wells and Impact on Production

The stress sensitivity of coal bed methane(CBM) has strong influence on the production. During the early stage of production of CBM, with the water drainage from fracture system, the decreased fluid pressure exerted on fractures near wellbore could force the fractures to close, and the permeability would suffer. This stress sensitivity mentioned above is also quite common in conventional gas reservoir with natural fractures. However, in the latter period of production, with the continuous desorption of coal bed gas from the matrix, stronger matrix shrinkage can recover the descending permeability. This unique character of CBM shows the compound effects of fluid pressure and matrix shrinkage. Herein,the relationship of permeability and effective stress was made from the desorption and seepage experiments of actual CBM cores. With the ECLIPSE E 300 CBM simulator, the reasonable discharge rate is discussed by means of simulation, and can be reference for actual production.