Study On Geology Modeling Of Coalbed Methane Development Upon OpenGL

Based on the geological conditions and production characteristics of CBM wellsin Fanzhuang block, this paper discussed the cause for coal reservoir permeability’sdynamic change and the influence of drainage rate on permeability, then revised anexisting prediction model on dynamic change of permeability, analyzed permeability’sdynamic change characteristics among CBM wells with different capacity type on thebasis of model calculation’s results, established the models on permeability ofdynamic change and development geological theory about different capacity of CBMwells, and realized the visualization model using OpenGL programming interface.The research has achieved the following results:In the process of drainage and recovering, the coupled action of effective stressand coal matrix shrinkage is the cause for dynamic change of permeability and hasobvious stages. In water production stage, effective stress increases and coalreservoir’s absolute permeability declines along with the output of coal seam water; ingas phase, effect of coal matrix shrinkage occurs and permeability is improved alongwith the desorption of CBM in great quantities. Drainage system effects permeabilitydynamic’s change by adjusting effective stress and coal matrix shrinkage and also hasstages.Considering stage characteristics of coupling effects of effective stress and coalmatrix shrinkage, bounded with critical desorption pressure, this paper correctedexisting prediction model on the dynamic change of permeability, making it more inline with the phased characteristics. Verification results show that the revised forecastmodel has higher reliability.Based on calculation of revised prediction model, permeability’s dynamic changecharacteristics is analyzed contrastively for CBM wells of different capacity. Analyzesbelieved that permeability of high yield gas and the middle gas wells reduce first andincrease then, while permeability of producing water wells keep decrease; in differentstages of drainage, permeability of different capacity types change in different levels:in water production stage, the permeability of lower producing water wells declinesgenerally higher; in gas production stage, The permeability of high yield gas wellrecovery significantly higher than that of the middle gas wells and water productionwells.Five different capacity type model on permeability’s dynamic change for CBM wells were put forward, including permeability change model’s of high yield gas andhigh yield water wells, high yield gas and low water production wells, middle-lowyield gas and high yield water wells, middle-low gas and low water production wellsand water prodution wells. With the coupled time and reciprocal relationship betweeneffective stress and coal matrix shrinkage as the basis, the process of dynamic changeis divided into stages of rapid decline, slow down, rising and equilibrium phase for thefirst four, and single continuous decline for the last.Theoretical model of CBM development geology was set up for coalbed methanewells of different capacity type in FanZhuang block, and realize the visual model withOpenGL. The model includes basis geological model of3#coal reservoir and modelsof dynamic change of permeability for CBM wells of different capacity. Visualizationof geological model is expressed as a macroscopic crack, showing the process ofdynamic change characteristics of coal reservoir permeability.