Analysis of Productivity Controlling for Adjacent CBM Wells in Mining Subsidence Area: a Case in the Fanzhuang Block, Southern Qinshui Basin, China

In order to analyze the productivity influence of mining subsidence area to adjacent coal seam gas wells, the paper studied physical properties and production characteristics of CBM wells in southwest Fanzhuang block. With changes of distance to mining subsidence area, distribution characteristics of gas content and permeability were expounded, variation character of gas production, water production of CBM wells were also analyzed. The mining subsidence area increased permeability of adjacent coal seam, meantime, reduced the gas content of coal seams, the coupling of positive and negative effects were main reasons for CBM production variability. The results indicates that with the increasing distance to mining subsidence area, the gas content increased gradually, and permeability decreased afterwards stable, the permeability achieved maximum value in depressurized zone; according to the production characteristics of CBM wells and permeability variation characteristics of adjacent coal seam, the around area of goaf was divided into zone I (pressure relief zone), zone II (intense interface area), zone III (weak interface area), zone IV (original coal district). Zone II and zone III are the most favorable area for high efficient development of CBM wells.