Direct Numerical Simulation of Pore Scale Flow and Reactive Transport of CO2 in Porous Media.

Abstract:

Recently, the need to decrease CO₂ concentration in the atmosphere has been recognized because of the role of CO₂ as a greenhouse gas that contributes to global warming. Carbon Capture and Sequestration (CCS) is one of the most promising long term solutions for the reduction of CO₂ in the atmosphere. To this end, injection of CO₂ into deep geological formations has been proposed and investigated theoretically and experimentally in the last years. The fracture permeability, an important parameter controlling CO₂ migration throughout sequestration, affects the amount of mineralization trapping of CO₂ which enhances the long-term CO₂ storage. A long-term geochemical modeling of subsurface CO₂ storage is carried out in a single fracture to investigate its impact on CO₂ transport and storage capacity. We model the fracture by considering flow of CO₂ between finite plates. CO₂ is initially dissolved in the brine and then precipitates during the geochemical reactions between H₂O-CO₂ and minerals. We study the physics and the critical time of blockage for a fracture to interpret the results. We employ direct numerical simulation tools and algorithms to simulate incompressible flow along with necessary transport equations that capture the kinetics of relevant chemical reactions. The numerical model is based on a finite difference method using a sequential non-iterative approach. It is found that mineral precipitation has an important effect on reservoir porosity and permeability. The fracture ceases to be a fluid channel because of the precipitation of minerals.