Charles M. Stone

A Comparison of Techniques for Coupling Porous Flow and Geomechanics

Summary This paper compares three techniques for coupling multiphase porous flow and geomechanics. Sample simulations are presented to highlight the similarities and differences in the techniques. One technique uses an explicit algorithm to couple porous flow and displacements in which flow calculations are performed every timestep and displacements are calculated only during selected timesteps. A second technique uses an iteratively coupled algorithm in which flow calculations and displacement calculations are performed sequentially for the nonlinear iterations during each timestep. The third technique uses a fully coupled approach in which the program’s linear solver must solve simultaneously for fluid-flow variables and displacement variables. The techniques for coupling porous flow with displacements are described and comparison problems are presented for single-phase and threephase flow problems involving poroelastic deformations. All problems in this paper are described in detail, so the results presented here may be used for comparison with other geomechanical/ porous-flow simulators.

Staggered In Time Coupling of Reservoir Flow Simulation and Geomechanical Deformation: Step 1 - One-Way Coupling

An isothermal, implicit, mixed finite element black oil reservoir simulator from the University of Texas is coupled to an explicit, quasistatic, nonlinear finite element solid mechanics code from Sandia National Laboratories. Both codes are 3d and parallel. The former models (in a locally conservative manner) the flow of oil, gas, and water fluid phases in the reservoir while the latter has been specialized to solve large-scale geomechanics problems involving significant inelastic deformations. In this paper we illustrate a uni-directional coupling of the two codes in which flow simulation output (pore pressures) from a 10-year test case based on the Belridge Field in California drives the geomechanics simulation for the same time period. The highporosity, low-permeability Belridge diatomite undergoes significant compaction including 6 feet of vertical displacement at the top of the reservoir.

Two-way coupling of a nonlinear geomechanics code with several porous flow simulators

Publisher Summary This chapter discusses a general approach for two-way coupling between an existing geomechanics code and two different porous flow simulators. The geomechanics code is a quasi-static finite element code developed specifically for problems characterized by large deformation and nonlinear material response. The coupling algorithm is based on a staggered-in-time loose coupling scheme in which each code solves its own set of equations and information is passed, at designated intervals, between the two codes. The approach incorporates a data mapping and transfer utility that allows different mesh discretizations for the porous flow model and the geomechanics model. The chapter presents an example of a two-way coupled calculation that demonstrates a class of problem where two-way coupling is necessary. Furthermore, this approach is a cost-effective alternative to the manpower investment required to write a fully coupled code because it takes advantage of the sophisticated capabilities already built into the geomechanics and porous flow codes.