Hydrodynamic Modeling of CO₂-Saturated Brine Injection in Geologic Formations for Carbon Sequestration Using the Lattice Boltzmann Method

We present the implementation of the conventional lattice Boltzmann method (LBM) with single-relaxation time (SRT) to model the injection of CO₂-saturated brine into underground porous rocks. The aim is to describe the “surface dissolution” technique of carbon sequestration, whereby CO₂ is dissolved in brine extracted from the designated storage site and this CO₂-brine solution is pumped back into underground formations. In the two-dimensional numerical model here, a small subsection of underground porous rock formation is represented as a staggered periodic array of disks. From a single unit cell of the porous structure, we have determined the domain size and lattice spacing required to reach a stable solution. By modeling single-phase flow, the permeability k could be calculated and compared over various lattice sizes to determine a mesh size-independent solution. A constant pressure gradient was imposed across the length of the domain to simulate the injection of the incompressible CO₂-saturated brine solution into the domain. From these simulations, velocity fields within the pore structure were obtained, and the effects of porosity on the permeability were explored. Such porosity effects may prove important at the transition between different rock layers within a storage site.