Abstract: In order to expose the cracks propagation law induced by hydraulic fracturing in deep low-permeability reservoir stratum, a series of hydraulic fracturing physical tests of low-permeability core samples collected in situ are carried out. Using CT scanning technology and self-developed three-dimensional reconstruction algorithm, the cracks propagation and special distribution laws are featured in low-permeability rock subjected to triaxial stress and hydraulic pressure. The effects of lithology and crustal stress on cracks growth distribution features are exposed. The results show that the lithology of rock and ratios of horizontal crustal stress have great influences on initiation stress and geometric distribution features of cracks growth. The initiation pressure is always greater than the confining pressure. When the minimum horizontal crustal stress is similar, the bigger ratio of horizontal crustal stress induces more fractured cracks and small initiation stress. The direction of failure main cracks is consistent with the direction of maximum horizontal crustal stress. The main cracks appear in the middle of samples accompanied by noticeable interruption, distortion and bifurcation.

Key words: hydraulic fracturing, low permeability, CT scanning, crack propagation