A parallel coupled hydro-mechanical numerical simulator, TOUGH-GeoFEM has been developed. The simulator couples two parallel simulators proven on several massively parallel supercomputers: TOUGH2-MP is a non-isothermal multiphase and multicomponent fluid flow simulator for porous and fractured media; GeoFEM is a mechanical deformation simulator of solids. In this paper, formulations and coupling schemes of the simulator are firstly presented. Then numerical examples from a core-scale laboratory experiment and a field-scale CO2 injection are illustrated, in which the simulator well describes observed deformation behaviours of rocks under multiphase flow conditions. Additionally, we investigated the parallel performance of TOUGH-GeoFEM using a two million grid model, and obtained a reasonable scalability up to several tens of CPU cores.
As a promising measure against global warming, CCS (Carbon dioxide capture and storage) has been extensively studied over recent decades, and some large-scale projects are currently in operation worldwide. Carbon dioxide is captured from flue gases emitted from large sources such as coal-fired power plant, and injected and kept stored in a deep geologic formation for a long-term. Injection of carbon dioxide into geologic formations can cause some geomechanical impacts including uplift of ground surface, reactivation of faults, and failure of caprocks. Numerical simulation is an effective approach to predict such coupled hydro-geomechanical behaviors during the geologic storage of carbon dioxide. In recent years, coupled hydro-mechanical simulators have been developed for studying ground deformation (Rutqvist et al., 2009), seismic events (Rutqvist et al., 2016), caprock stability (Rutqvist et al., 2008).
However, for evaluating these impacts in practical CCS projects, the modeling works can be often computationally demanding. The size of numerical model may need to be large for representing spatial heterogeneity of reservoirs, covering a large geologic domain of storage complexes, investigating for detailed processes around injection wells, and so on. History matching study of hydro-geomechanical behaviors can give rise to further requirement of computational power (e.g. Rinaldi et al., 2017). To meet computational demands in such modeling works, numerical simulators capable of massively parallel computations serves a reasonable option.
In this paper, we first describe a coupled hydro-geomechanics simulator for massively parallel computation, TOUGH-GeoFEM (Taisei Corporation, 2010). The simulator couples fluid flow simulator, TOUGH2-MP with a mechanical simulator, GeoFEM. Both codes are designed for massively parallel computing. Then some numerical examples for validation of TOUGH-GeoFEM are presented. First example is from a core-scale laboratory experiments that investigated small strain deformation of sandstone in elastic range under two phase flow condition during air-injection test by Goto et al. (2014). Second example is from a numerical simulation of uplift of land surface observed at In Salah CO2 storage project. Finally, the parallel performance of the TOUGH-GeoFEM measured for a simulation of CO2 injection with a few millions gridblock model is presented.