Alternative dissolution-rate controlled model and time adaptive, high resolution scheme for site-scale subsurface carbon sequestration simulation
摘要
Performance assessment and field-development planning for carbon geo-sequestration relies on reservoir simulation. The standard approach is to use regular (corner-point) grids in space and a fully implicit discretisation in time, solving for all primary unknowns at once using Newton’s method. While the former limits the physical realism of the simulation model built from the geomodel, the latter leads to a large ill-conditioned system of equations that is inefficient to solve. We overcome the regularisation issue via a hierarchy of fully unstructured, geobody-conforming, finite element meshes which can be refined until mesh convergence is achieved. To address the time discretisation issue we employ, for the first time, the linearly implicit extrapolation scheme (LIMEX) to solve the highly non-linear coupled two-phase flow and reactive transport equations. To solve the arising large sparse systems of linear equations, we apply the geometric multigrid (GMG) method that demonstrates optimal, linear complexity and allows an efficient parallelization on supercomputers. Another novel feature of our formulation is the consideration of the kinetics of mass transfer between the carbonic and aqueous phases. This approach removes the first-order dependence on mesh refinement of