Computational simulation of coupled poromechanical processes in deformable fractured and porous media

Abstract:

Prediction of flow, reactive transport, and deformation in fractured porous media is critical to improving our scientific understanding of coupled thermal-hydrological-mechanical-chemical (THMC) processes related to many subsurface energy activities and storage. With the existing numerical simulators an iterative coupling method of different physical principles such as fluid and solid mechanics is a viable approach to improve our simulation capabilities. It is now well-known that a certain class of iteration schemes such as the fixed stress scheme can provide an accurate approach compared to the fully coupled monolithic approach. In this work we implemented the fixed stress scheme into an existing Sandia Sierra Multiphysics toolkit where thermal/fluid mechanics module is coupled with the solid mechanics module. First, we rigorously compared the fixed stress scheme with the fully coupled method implemented in the Sierra fluid mechanics module for poroelastic problems such as one-dimensional (Terzaghi), two-dimensional (Mandel), and three-dimensional (Cryer Sphere) problems. For these three benchmark problems, both methods are also compared with analytical solutions. The effect of convergence criteria is examined to investigate the trade-off between accuracy and computational demand. Further, the sensitivity of the benchmark problems to material parameters of the porous media is evaluated. After model verification with the fixed stress scheme, the model is validated against well-controlled laboratory experimental data where flow and transport processes as a function of confined pressure have been investigated with different morphological geomaterials. We will evaluate the dependency of permeability and diffusion processes on the response of fracture aperture and pore structures given the confined pressure. This comparison will reveal the importance of coupled poromechanics on permeability evolution and diffusion processes in deformable porous media. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.