Response Characteristics and Mechanisms of Dynamic Fluid Field for Well Interference of Coal Bed Methane Group Wells in Production Block

Abstract

According to production data and reservoir data of 16 coal bed methane (CBM) wells in southern Qinshui Basin, this paper draws the contour map of groundwater fluid potential at 8 moments in the production monitoring area and establishes three-dimensional visualization model of superimposed pressure drop funnel in CBM well with Matlab mathematical software; discusses the response relationship between well interference and dynamic fluid field on the basis of analyzing dynamic change features of groundwater fluid potential and evolution features of superimposed pressure drop funnel and puts forward an evaluation program of dynamic fluid field for well interference. The research result shows that dynamic fluid field has a good response relationship with well interference of CBM well and is manifested by the corresponding relation between evolutionary phase and space distribution. Evolution features of dynamic fluid field can be used to judge the phase and degree of well interference. The stage when well interference does not form is corresponding to the failure stage of original groundwater fluid potential and evolutionary phase of single-well pressure drop funnel. CBM wells do not have well interference and pressure drop funnel exists in the form of independent funnel. The space distribution of groundwater fluid potential is balanced. Due to the influence of groundwater fluid potential distribution, formation water flows to the shaft from the scope of pressure drop funnel. The stage when well interference forms preliminarily is corresponding to the stage of differentiation and reconstruction of groundwater fluid potential and formation stage of local superimposed pressure drop funnel. CBM wells start to have well interference and the degree of superposition of pressure drop funnel increases in local areas. “Low-lying” collecting area of groundwater fluid potential forms in superimposed area. Coal bed water flows to this area. The stabilization stage of well interference is corresponding to the formation and stabilization stage of new groundwater fluid potential and formation stage of regional superimposed pressure drop funnel. Regional superimposed pressure drop funnel is basically mature. New groundwater fluid potential centering on superimposed pressure drop funnel basically forms and coal bed water flows to the center of well network from surrounding areas.