Abstract

Hydraulic fracturing is an indispensable technique for developing unconventional resources such as shale gas and tight oil. According to micro-seismic data, when hydraulic fractures interact with pre-existing natural fractures, the result can be a complex fracture network. While most simulation studies treat natural fractures as frictional interfaces with cohesion, core observations show that partially cemented and fully cemented natural fractures are widely present. We use semi-circular bending tests to examine propagation paths and strength of samples with pre-existing cemented fractures. In this study, synthetic Hydrostone samples with embedded inclusions of different mechanical properties are used to mimic cemented natural fractures. In a series of experiments, we assess the influence of the fracture approach angle, inclusion strength, and inclusion thickness on fracture propagation. Results show that fractures tend to cross inclusion with high approach angle and divert into the inclusion with low approach angle. The inclusion thickness does not change the crossing/diverting behavior for orthogonal approaching samples, but it changes the jog distance along the interface. Preliminary simulation results are used to explain the experimental observation. The assessments of fracture interaction in this study are in good agreement with previous work and theories.

URTeC 1576910

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