页岩气藏水平井分段多簇压裂与流动数值模拟

摘要

To discover the effect of fracturing parameters on gas production in horizontal wells of shale gas reser-voirs, numerical simulation of staged cluster fracturing and gas flow have been carried out. The model of fracture propagation has taken the effect of stress shadowing into account. The model solved stress and displacement discon-tinuity with displacement discontinuity method, coupled fluid flow in the wellbore and fractures have been solved by Newton iteration method. Taking viscous flow, Knudsen diffusion and adsorption-desorption, shale gas flow after fracturing has been solved by using discrete fracture model. Simulation results show: As to simultaneous propaga-tion of multiple cluster fractures, when fractures spacing become smaller, the deviation angles of side fractures from maximum horizontal principle stress direction become larger, and the width of middle fracture becomes smaller. When fracturing stage number of horizontal well increases, cumulative gas production increases with a decreasing rate. As to a fracturing stage, cumulative gas production of three clusters is larger than that of two clusters. The lar-ger fractures spacing is, the larger cumulative gas production is.%为探究页岩气藏水平井压裂参数对产气量的影响，开展了分段多簇压裂与流动的数值模拟研究。裂缝扩展模型考虑应力阴影作用，利用位移不连续方法求解应力与位移不连续量。耦合井筒和裂缝中流体流动，并采用牛顿迭代法求解；考虑页岩气的黏性流、Knudsen扩散和吸附解吸，采用离散裂缝模型对压裂后页岩气的流动进行了求解。模拟结果表明：多簇裂缝同步扩展时裂缝间距越小，两侧裂缝偏离最大水平主地应力方向角度越大，中间裂缝宽度越小；随着水平井压裂段数增加，累积产气量增加，但增加幅度逐步降低；至于压裂段，三簇压裂比两簇压裂累积产气量高；裂缝间距越大时，累积产气量越高。