受地应力调控脉冲注液下钻孔内围岩破裂特征研究

Study on the fracture characteristics of the surrounding rock in boreholes under pulse fluid injection regulated by ground stresses

摘要:

破裂特征研究在非常规能源开采中具有重要意义。利用自研的真三轴水力压裂模拟试验系统，选取湘东北燕山期的花岗岩，在测定基本物理力学参数基础上开展不同地应力条件下的花岗岩水力压裂监测试验，基于水压特征值提取结合三维形貌扫描方法描述花岗岩裂缝演化特征及破裂面破裂效果，分析脉冲注液条件下地应力对水压响应特征参数影响，随着地应力的增加，破裂压力和压降均呈增加趋势。高地应力条件抑制了裂缝的扩展使得主裂缝发生偏转，低地应力条件有利于形成高粗糙度的破裂面，且在该条件下的裂缝面分形值也更高。这对复杂地质条件下钻孔围岩破裂特征研究具有一定意义。

Abstract:

The study of fracture characteristics is of great significance in unconventional energy exploitation. Using the self-developed true triaxial hydraulic fracture simulation system， granite from Yanshan period in northeast Hunan Province was selected to carry out hydraulic fracture monitoring tests under different geopathological stresses based on the determination of basic physico-mechanical parameters. Based on the extraction of hydraulic eigenvalues combined with the method of three-dimensional morphological scanning to describe the characteristics of granite fracture evolution and rupture effect of rupture surfaces， the impacts of the geopathological stress on the characteristic parameters of hydraulic pressure response were analysed under the conditions of pulse fluid injection. The rupture pressure and pressure drop increased with the increase of geostress. The high geostress condition inhibits the fracture extension and makes the main fracture deflected， while the low geostress condition is conducive to the formation of the fracture surface with high roughness， and the fracture surface fractal value is higher under this condition. This is of some significance to the study of fracture characteristics of borehole perimeter rock under complex geological conditions.