Experimental study on the hydraulic fracture propagation in shale

To realize the control on geometry of fracture network and improve the individual well production of shale gas reservoirs, hydraulic fracturing simulation tests of shale outcrops for horizontal well were carried out. This was based on an established true triaxial hydraulic fracturing simulation test system, to analyse the propagation and formation of a complex fracture network. The results show that the typical severe fluctuation of pump pressure during extension, is an obvious feature of hydraulic fracturing by Stimulated Reservoir Volume (SRV). Due to the large size and abundant natural fractures in shale specimens, the acoustic emission (AE) energy is weak during propagation of hydraulic fractures. However, fracture propagation can still be effectively determined to some extent, although relatively few AE events are detected. Hydraulic fractures from horizontal well initiate approximately along the maximal in situ stress. But the fractures gradually deviate from the orientation when extending. Branching, re-orientation or penetrating bedding planes and then interconnecting with natural fractures or weak beddings are the main mechanisms of the formation of complicated fracture networks.