低渗储油层水力压裂裂缝延伸过程及成缝机理

Extension Process and Fracture Mechanism of Hydraulic Fractures in Low Permeability Reservoir

为了评价花古6井低渗储油层的压裂效果,在该井地表建立了微震监测系统.基于微震监测结果,利用裂纹延伸路径分析方法及矩张量分析方法对压裂过程中裂缝延伸的时空过程及成缝机理进行了分析.分析结果表明:不同黏度液体注入时,裂纹的空间展布具有不同的特征,注入高黏液时储层中形成了裂缝密度较低的缝网,注入低黏液时储层中形成的缝网具有延伸路径短、分叉明显、密度高、范围大等特征,注入中黏液会在储层形成一些始于分支裂缝端部的裂纹;裂缝的破裂类型以剪切破裂为主(占比89. 5%),并且破裂类型占比不受液体黏性的影响.

In order to evaluate the hydraulic fracturing effect in the low permeability reservoir of Huagu 6 well,a microseismic monitoring system was established on the surface of the well.Based on microseismic data,the spatio-temporal extension process and fracture mechanism of hydraulic fractures are analyzed by means of crack extension path and moment tensor inversion.The results show that the spatial distribution characteristics of fractures changed with the liquid viscosity.The injection of high viscosity liquid formed a fracture network with low fracture density.The injection of low viscosity liquid formed a large-ranged dense fracture network with short extension path,and many crack branches.The injection of medium viscosity liquid formed some fractures that initiated from the branching fracture ends.The fracture type was mainly shear fracture(89.5 %),and was not affected by the viscosity of the liquid.