ABSTRACT:

In this paper we demonstrate our attempts to model fluid injection induced fault movement using the Cohesive Zone Method (CZM) within the framework of the Finite Element Method (FEM). We build a concept model with stress state similar to that of Western Canadian Sedimentary Basin. In our concept model, a strike-slip fault is represented by a thin layer of cohesive elements. The constitutive equations of the cohesive elements are prescribed to represent the rheology of the fault. Our benchmark test with changing stress states shows that our approach can effectively model the stick-slip process of an earthquake. We further apply this method on a transient test with the injection/extraction histories similar to a hydraulic fracturing operation. The simulation results show that the increase in pore pressure due to fluid injection leads to the reduction of the fault’s shear strength which is represented using a damage factor D in our model. The fault’s slip rate is highest while the bonding between two sides of the fault plane is being broken down. After the bonding is completely broken, the fault will continue to slip but at a smoother and slower rate.

1. INTRODUCTION
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