Development of a Parallel Geomechanics Code Based on the Message-Passing-Interface (MPI) Approach and Iterative Coupling with a Parallelized Flow and Thermal Simulator for the Analysis of System Behavior in Hydrate-Bearing Geologic Media

The Reservoir GeoMechanics Simulator (RGMS), 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 stand-alone, or coupled with flow and transport models. pT+H V1.5, a parallel MPI-based version of the serial 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. The code development and testing process involve evaluation of the parallelization and of the coupling method, as well as verification and validation of the results. The parallel performance of the codes is tested on the Texas A&M University Ada Linux cluster using up to 512 processors, and on a Mac Pro computer with 12 processors. 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 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 code parallel performance is monitored. Using 512 processors, 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 (a) the necessity of using full geomechanics simulators in marine hydrate-related studies because of the associated pronounced geomechanical effects on production and displacements, (b) the importance of fine discretization, and (c) 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