Coupled Fluid Flow and Geomechanical Modeling for Evaluating Unconventional Well Performance and Seismicity Risks
Abstract
The success of unconventional shale applications in the oil and gas industry often require the understanding of pore pressure and stress/strain changes due to both injection and production. In order to evaluate the complex phenomena associated with both pore pressure and stress change, coupled fluid flow and geomechanical models are necessary, especially in unconventional applications that involved fluid extraction and injection. In this dissertation, we utilize coupled fluid flow and geomechanical simulation to reveal the mechanisms of induced seismicity and to understand the characteristics of hydraulic fractures under different completion designs. First, we perform a site-specific study of the mechanics of induced seismicity in the Azle area, North Texas, using a coupled 3-D fluid flow and poroelastic simulation model. The results show no fluid movement or pressure increase in the crystalline basement, although there is plastic strain accumulation for the weaker elements along the fault in the basement. The accumulation of plastic strain change appears to be caused by the unbalanced loading on different sides of the fault due to the differential in fluid injection and production. Even though the low-permeability faults in the basement are not in pressure communication with the Ellenburger formation, the poroelastic stresses transmitted to the basement can trigger seismicity without elevated pore pressure. Second, we extend the first part of the dissertation to include a detailed discontinuous fault to model the natural behavior of fault slips. We develop the workflow to couple the finite difference and finite element simulations to explicitly model fault slips and dissipated energy in the Azle site. The results suggest that the slips can occur at the location where there is no pressure change. The radiated energy from observed seismic events is about 20% of the dissipated energy calculated from the simulation results. Third, we investigate the impact of cluster spacing on hydraulic fracture design using the Eagle Ford field data. We first identify the fracture geometry by history matching the field injection treatment pressure. Then, we history match the well production data using the rapid Fast Marching Method based flow simulation. The results suggest that most fractures are planar in Eagle Ford because of the high stress anisotropy. The well with tighter cluster spacing tends to develop shorter fractures. The well with tighter cluster spacing has better SRV permeability in the Eagle Ford, leading to better drainage volume and production performance. The tighter cluster spacing completion is more favorable in the Eagle Ford formation because there is minimal fracture interference.
Subject
Coupled Flow and GeomechanicsCitation
Chen, Rongqiang (2020). Coupled Fluid Flow and Geomechanical Modeling for Evaluating Unconventional Well Performance and Seismicity Risks. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /191590.