基于煤岩割理正交各向异性性质的低渗透煤层压力数值模拟研究

考虑煤岩面割理和端割理两个方向不同渗流性质,建立了低渗透性煤层气水固三相流固耦合模型,利用该模型分析了沁水盆地煤层气井在开采过程中压力及解吸半径变化规律,并对影响煤层压力的割理参数进行分析.计算结果表明:非耦合模型比耦合模型的解吸面积要大;随着煤岩割理渗透率正交各向异性系数的增大,煤层面割理方向解吸半径逐渐增大,而煤层端割理方向解吸半径逐渐减小;面割理方向,随着割理渗透率正交各向异性系数和割理宽度的增大,煤层压力先增加后降低;端割理方向,煤层压力随着渗透率正交各向异性系数、割理密度和割理宽度的增大而增大.

Numerical Simulation of Pressure Distribution of Coal Seams Based on the Orthotropic Physical Properties of Coal Cleats

The coupling model of three-phase of gas-water-solid for coal seams was established on the basis of the orthotropic physical properties of coal cleats and different seepage characteristics in the orientation of the face and butt cleats.The comparison between the calculated results based on the coupling model and the uncoupling model indicated their good agreement,which verified the accuracy and rationality of the model.By using the coupling model,the distribution of pressure and desorption radius were obtained and the effect of physical parameters of coal cleats on pressure was analyzed.The results showed that the desorption area of the non-coupling model was larger than that of the coupling model.The desorption radius along the face cleats direction increases with permeability orthotropic coefficient increasing,whereas it decreases along the butt cleats direction.The pressure along the face cleats direction increases first and then decreases with permeability orthotropic coefficient and cleat width increasing,and increases with permeability orthotropic coefficient,cleat density and cleat width increasing.