An innovative computationally efficient hydromechanical coupling approach for fault reactivation in geological subsurface utilization

Abstract

Estimating the efficiency and sustainability of geological subsurface utilization, i.e., Carbon Capture and Storage (CCS) requires an integrated risk assessment approach, considering the occurring coupled processes, beside others, the potential reactivation of existing faults. In this context, hydraulic and mechanical parameter uncertainties as well as different injection rates have to be considered and quantified to elaborate reliable environmental impact assessments. Consequently, the required sensitivity analyses consume significant computational time due to the high number of realizations that have to be carried out. Due to the high computational costs of two-way coupled simulations in large-scale 3D multiphase fluid flow systems, these are not applicable for the purpose of uncertainty and risk assessments. Hence, an innovative semi-analytical hydromechanical coupling approach for hydraulic fault reactivation will be introduced. This approach determines the void ratio evolution in representative fault elements using one preliminary base simulation, considering one model geometry and one set of hydromechanical parameters. The void ratio development is then approximated and related to one reference pressure at the base of the fault. The parametrization of the resulting functions is then directly implemented into a multiphase fluid flow simulator to carry out the semi-analytical coupling for the simulation of hydromechanical processes. Hereby, the iterative parameter exchange between the multiphase and mechanical simulators is omitted, since the update of porosity and permeability is controlled by one reference pore pressure at the fault base. The suggested procedure is capable to reduce the computational time required by coupled hydromechanical simulations of a multitude of injection rates by a factor of up to 15. P is transferred to the geomechanical simulator. An additional coupling parameter for non-isothermal studies is the temperature T. If this data transfer is occurring only in one direction (one-way), the resulting volumetric strain v will not be fed back to the multiphase flow simulator for updating porosity and permeability (Fig. 1 (a)). In case of large volumetric strains V occurring during the simulation, a one-way coupling may lead to inaccurate results (Cappa and Rutqvist, 2011; Chabab

Analytical Model to Detect Fault Permeability Alteration Induced by Fault Reactivation in Compartmentalized Reservoirs

“…Later research modified Yaxley's solution to account for fluid flow along the fault and fault storage capacity (Abbaszadeh & Cinco‐Ley, ; Rahman et al, ). More recently, Adams et al () introduced a semianalytical hydromechanical model for hydraulic fault reactivation considering multiphase flow. However, none of the analytical models for fluid flow across and along faults account for the possibility of fault reactivation caused by fault slip.…”