Numerical investigation of slippage characteristics of normal and reverse faults under fluid injection and production

Nowadays, a great deal of petroleum geology and engineering projects associated with underground fluid injection and production (FIP) are widely conducted around the world. The FIP engineering may cause complex stress perturbation and trigger seismicity, which have been extensively reported and studied. In this paper, we investigated the fault slippage characteristics influenced by FIP. It reveals that for a fault (normal or reverse) that penetrating through the reservoir into the caprock and underburden, the footwall reservoir is the relatively stable one for fluid injection in a fluid FIP engineering. No matter it is a normal or a reverse fault, injecting fluid into footwall reservoir and producing fluid from the hanging wall reservoir can induce smaller fault slippage. After having determined the better fluid injection–production pattern, we studied the influence of three key factors of fault, i.e., dip, offset and depth, on fault stability. We found that, in our range of study, the influence of single action of fault dip, offset or depth on fault slippage in a FIP engineering was small. However, the influence of the combined effects of the factors may be large. Finally, we studied the effect of different pressure management scenarios on fault responses based on the specific fluid injection–production pattern. The results revealed that appropriate pressure management could effectively reduce fault slippage in a FIP engineering. However, inappropriate pressure management may cause much larger fault slippage. Given these concerns, it is therefore vital that the effect of pressure management scenario to be modeled prior to FIP.