ABSTRACT:

The characteristics of a natural fracture system (NFs) play an important role in the hydraulic fracturing treatment. Open fractures form intercommunicated channels of high permeability while sealed fractures act as weakness planes and can be activated during the hydraulic fracture treatments. The final geometry of the hydraulic fracture (HF) can be different when interacting with these two types of natural fractures (NF). This work proposes a numerical approach using finite element method to study the hydraulic fracture propagation and its interaction with sealed and open natural fractures. An intrinsic mesh fragmentation is used to simulate hydraulic fracture propagation with arbitrary paths. The hydraulic fracture behavior is represented by coupled cohesive zone model. Mohr coulomb criterion with tension cutoff and an empirical contact model are incorporated to simulate the shear and closure behavior of natural fractures, respectively. The effect of some initial field conditions such as in situ stress and initial opening of the NF – on the hydraulic fracture propagation has been studied. A fracture network of a real reservoir is also studied, assuming open and sealed natural fracture configurations. The study considers different initial apertures and their effects on the final induced-natural fracture network. The numerical results show that hydraulic fracture branches into open fractures. On the other hand, sealed fractures may result in different types of hydraulic fracture propagation (opening, crossing and arresting).

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