| Popis: |
A deep volcanic reservoir has high geostress, and the rock in the reservoir exhibits strong heterogeneity. Moreover, extensive natural fractures are distributed in the reservoir, and the hydraulic fracture propagation mode is unclear. A high-stress true triaxial hydraulic fracturing test was carried out on volcanic rock to study the influence of vertical stress difference under different maximum horizontal principal stresses on the fracture propagation characteristics. We studied the fracture characteristics using image processing and fracture characterization methods. The high-stress hydraulic fracturing test showed that the vertical stress difference mainly affected the direction of fracture propagation and fracture roughness. Less vertical stress difference implied chaotic fracture propagation, complex fracture network, and rough fracture surface. Hydraulic fracture interface characteristics indicated that the peak pump pressure linearly increased with an increase in the vertical stress difference. Moreover, the overall fractal dimension and crack width decreased and increased, respectively, with the increase of vertical stress difference, which were verified from the decreased fractal dimension of cracks and increased crack width at different positions, respectively. |
