Nearly all fracturing literature attributes the productivity of unconventional reservoirs to the presence of a distributed fracture network within the body of the reservoir. The hydraulic fracture is assumed to be the main conduit connecting these natural fractures to each other and to the wellbore.
Based on a rigorous analytical solution, this presentation reviews the conditions required to activate natural fractures that lie within the body of the formation and away from the propagating hydraulic fracture. It will show that the most likely cause of the activation of these natural fractures is by tensile extension, which occurs when the natural fracture falls within the influence zone of the tip of the growing hydraulic fracture. This causes an increase in the effective formation permeability around the main fracture, which ultimately results in increased well productivity. This presentation will show that single fractures are more likely to cause natural fracture activation than multiple fractures created in plug and perf completions. Furthermore, natural fractures closer to the hydraulic fracture are more likely to become activated by it. Some of the findings in this presentation differ from commonly-held beliefs in the fracturing community.