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

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.