Control mechanisms of water production and gas production divergences ofCBM wells in southern Qinshui basin

Recognizing the major controlling factors of water production and gas production divergences between CBM wells can promote the benefits in the process of CBM development.The divergences of water and gas production between CBM wells were analyzed, and then the geological control mechanisms of those divergences were further discussed, based on the dynamic data of exploration and development collected from 144 wells drilled in a high-rank coalbed methane well area in the south part of Qinshui basin.The results show that, various water wells and gas wells are belts distributed on the plane in the study area, showing the characteristics of high water yield and low gas production.Moreover, the production of CBM wells is mainly controlled by groundwater and tectonic styles, which is mainly reflected in two aspects.First, the water source of CBM wells mainly comes from fracturing water, coal seam water and surrounding rock make-up water which is mainly derived from adjacent sandstone.Second, the high-productivity wells in the study area are usually distributed over the wings of the sublevel anticline on axis and the wings of local synclinorium; the medium-productivity wells predominantly distributed over local synclinoria relief wing and secondary syncline wings; besides the low-productivity wells are primarily distributed over the axis of the secondary syncline and the high point of structures in the eastern part of the study area.Finally, it is suggested that the scale of fracturing should be controlled in well areas with high water productivity and the long term effective operation of the pump should also be guaranteed.However the scale of fracturing in well areas with low water productivity should be increased, and special attention should be paid to the control of early groundwater production.