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从各向同性线弹性材料应力应变关系出发,考虑气体解吸引起的基质收缩效应和孔隙压力对储层应力的影响,建立了包含基质压缩系数、裂隙体积压缩系数和流体压力项的渗透率动态变化方程,分析了储层力学参数对渗透率变化的影响。结果表明:排水降压初期,有效应力处于主导地位,裂隙发生压缩变形,渗透率降低;气体解吸后基质收缩占主导地位,裂隙张开幅度增大,渗透率升高;弹性模量、泊松比越大,基质变形程度越大,渗透率呈先降低后升高的回归趋势越明显,弹性模量较泊松比对回归趋势的影响更大;当孔隙压力较高时,低孔低渗煤层渗透率随孔隙压力降低变化的幅度不大;裂隙体积压缩系数变化的起始压力点可以根据不同起变压力下渗透率与储层压力的关系确定。
Based on the stress-strain relationship of isotropic linear elastic material, considering the effect of matrix shrinkage caused by gas desorption and the influence of pore pressure on reservoir stress, a dynamic change of permeability including matrix compressibility coefficient, fracture volume compressibility coefficient and fluid pressure term was established Equation, the influence of reservoir mechanics parameters on permeability change is analyzed. The results show that the effective stress is in the leading position during the initial step of drainage and drainage, the fractures compress and deform, and the permeability decreases. The matrix shrinkage dominates after gas desorption, and the crack opening width increases and the permeability increases. The elastic modulus, Poisson The larger the ratio, the greater the degree of matrix deformation, the more obvious the regression trend of the permeability decreasing firstly and then increasing, and the greater the elastic modulus than the Poisson’s ratio on the regression trend. When the pore pressure is high, the low porosity and low permeability The permeability of coal seam varies little with the decrease of pore pressure. The initial pressure point of the change of compressive coefficient of fracture volume can be determined according to the relationship between permeability and reservoir pressure under different deformation pressures.