The paper focuses on the vertical wells in the Fanzhuang Block of Qinshui Basin.By compre-hensively considering the dynamic changes in permeability caused by variations in drainage pressure,a gas-water flow model suitable for high-rank coal seams is constructed by establishing the relationship be-tween stress,compressibility,and permeability.Meanwhile,the pressure drop expansion law during both the single-phase water production stage and the two-phase gas-water production stage is quantitatively an-alyzed,clarifying the pressure drop expansion patterns of the coalbed methane wells in Fanzhuang block,and optimizing the field drainage system for single wells.The results indicate that there is an optimal gas extraction rate during the gas extraction stage.Additionally,six main control factors affecting the pressure drop expansion in coal reservoirs are determined,and a prediction formula for the optimal gas extraction rate during the gas extraction stage is developed,guiding the drainage management and control of coalbed methane wells in Fanzhuang Bock and similar areas.
Qinshui Basinhigh-rank coal reservoirpermeability dynamic variationquantitative pres-sure drop indicatoroptimal gas extraction rate
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