The Laboratory Study of Cementing Effect of Natural Fracture on Hydraulic Fracture Propagation in Unconventional Oil and Gas Reservoirs

In this study, a series of laboratory tests using a hydraulic fracturing system were conducted to examine the behavior of an induced hydraulic fracture as it approached a cemented natural fracture. To achieve this, sheet-like test specimens were cast with natural fractures of varied mechanical properties, thickness, and relative position to a fluid injection port.  A tendency for the induced hydraulic fracture was shown to cross thick natural fractures filled with softer materials than the host rock and to be diverted by thick natural fractures with harder filling materials. The induced hydraulic fracture also tends to cross hard natural fractures when the natural fractures are relatively thin. In addition, the induced hydraulic fracture from the injection port was shown to be diverted by a thin, hard natural fracture that was placed relatively close to the injection port but crosses the same natural fracture when placed farther away from the injection port. Finally, the results provide a novel evidence of the impact of natural fracture filling materials on the outcome of hydraulic fracture propagation at its interaction with natural fractures.