Enhanced reservoir connectivity generally requires maximizing the intersection between hydraulic fracture (HF) and preexisting underground natural fractures (NF), while having the hydraulic fracture continue to propagate across the natural fractures. Observations of downhole core samples suggest that these natural fractures are in fact veins filled with minerals such as calcite (Mighani et al., 2016). We study this interaction during the approach of a hydraulic fracture to a smooth saw-cut fracture under triaxial stress conditions. The specimen is Solnhofen limestone, a fine-grained (<5 µm grain), low permeability (<10 nD) carbonate. The differential stress (1-20 MPa) and inclination of the fault which determines the approach angle, ? (30, 60°) are the experimental variables. We conduct the experiments on both bare surface and gouge-filled fault surfaces. The gouge is a 1 mm thick crushed powder of Solnhofen limestone with <106 µm grain size. During the hydraulic fracture, acoustic emissions (AE), inferred slip velocity, axial stress and pore pressure are recorded at a 5 MHz sampling rate.

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