In past studies, changes in fluid pressure in natural fractures (planes of weakness) have been ignored for the interaction of hydraulic and natural fractures. To overcome these limitations, in this paper we develop a method to simulate the growth of hydraulic fractures as they interact with natural fractures while accounting for changes in fluid pressure in the network of natural fractures. This simulation can be very computationally expensive and so a computationally efficient, mesh-free, integrated fracturing-production simulator was developed to simulate the creation of fracture networks and simulate fluid flowback.

The integrated fracturing-production simulator has several key advantages. It can: (1) capture the variation of fluid pressure in natural fractures induced by variations in stresses in the rock matrix, (2) eliminate the need to discretize the rock matrix domain by using the displacement discontinuity method for fracture propagation, and (3) use a new and general Green’s function solution for production and flowback . Information about the propagated complex fracture network can be seamlessly used by the fluid production module once the hydraulic fracturing process ends.

The simulator is used to investigate the effect of changes in in-situ stress contrast, and other parameters in the discrete fracture network (DFN) on the geometry of the fracture network and fluid flowback.. The results show that (1) compared to a constant fluid condition in natural fractures, the variation of natural fracture fluid pressure can significantly change the geometry of the created fracture network and subsequent production rate; (2) a larger stress contrast more readily reactivates natural fractures and leads to a shorter fracture network and a lower production rate; and (3) an alternate fracturing sequence generates longer fractures, resulting in better well performance.

The simulator presented here can be used to provide computationally efficient and effective guidance on fracture design and reservoir optimization to enlarge reservoir drainage area and increase well productivity.