Message Passing Interface (MPI) Parallelization of Iteratively Coupled Fluid Flow and Geomechanics Codes for the Simulation of System Behavior in Hydrate-Bearing Geologic Media. Part 2: Parallel Performance and Application

Abstract

Summary The reservoir geomechanics simulator (RGMS or RGM simulator), a geomechanics simulator based on the finite element method and parallelized using the Message Passing Interface (MPI), is developed in this work to model the stresses and deformations in subsurface systems. RGMS can be used standalone or coupled with flow and transport models. pTOUGH+HYDRATE (pT+H) V1.5, a parallel MPI-based version of the serial TOUGH+HYDRATE (T+H) V1.5 code that describes mass and heat flow in hydrate-bearing porous media, is also developed. Using the fixed-stress split iterative scheme, RGMS is coupled with the pT+H V1.5 to investigate the geomechanical responses associated with gas production from hydrate accumulations. In the second paper of this series, the parallel performance of the codes is tested on the Texas A&M University Ada Linux cluster using up to 512 processes and on a Mac Pro computer with 12 processes. The investigated problems are: Group 1: Geomechanical problems solved by RGMS in 2D Cartesian and cylindrical domains and a 3D problem, involving 4×106 and 3.375×106 elements, respectively; Group 2: Realistic problems of gas production from hydrates using pT+H V1.5 in 2D and 3D systems with 2.45×105 and 3.6×106 elements, respectively; Group 3: The 3D problems in Group 2 solved with the coupled RGMS-pT+H V1.5 simulator, fully accounting for geomechanics. Two domain partitioning options are investigated on the Ada Linux cluster and the Mac Pro, and the code parallel performance is monitored. On the Ada Linux cluster using 512 processes, the simulation speedups (a) of RGMS are 218.89, 188.13, and 284.70 in the Group 1 problems, (b) of pT+H V1.5 are 174.25 and 341.67 in the Group 2 cases, and (c) of the coupled simulators are 134.97 and 331.80 in the Group 3 cases. The results produced in this work show the necessity of using full geomechanics simulators in marine hydrate-related studies because of (a) the associated pronounced geomechanical effects on production and displacements and (b) the effectiveness of the parallel simulators developed in this study, which can be the only realistic option in these complex simulations of large multidimensional domains.