Injection and Storage of CO_2 in Deep Saline Aquifers: Analytical Solution for CO_2 Plume Evolution During Injection

摘要

Injection of fluids into deep saline aquifers is practiced in several industrial activities, and is being considered as part of a possible mitigation strategy to reduce anthropogenic emissions of carbon dioxide into the atmosphere. Injection of CO_2 into deep saline aquifers involves CO_2 as a supercritical fluid that is less dense and less viscous than the resident formation water. These fluid properties lead to gravity override and possible viscous fingering. With relatively mild assumptions regarding fluid properties and displacement patterns, an analytical solution may be derived to describe the space-time evolution of the CO_2 plume. The solution uses arguments of energy minimization, and reduces to a simple radial form of the Buckley-Leverett solution for conditions of viscous domination. In order to test the applicability of the analytical solution to the CO_2 injection problem, we consider a wide range of subsurface conditions, characteristic of sedimentary basins around the world, that are expected to apply to possible CO_2 injection scenarios. For comparison, we run numerical simulations with an industry standard simulator, and show that the new analytical solution matches a full numerical solution for the entire range of CO_2 injection scenarios considered. The analytical solution provides a tool to estimate practical quantities associated with CO_2 injection, including maximum spatial extent of a plume and the shape of the overriding less-dense CO_2 front.