Reservoir Simulation of CO2 Storage in Deep Saline Aquifers

TLDR

The study aims to quantify key CO₂ storage mechanisms under realistic physical conditions. Simulations modeled decades of CO₂ injection followed by 10³–10⁵ years of natural gradient flow, varying permeability, anisotropy, residual gas saturation, salinity, temperature, dip angle, and heterogeneity. Residual gas storage can be substantial—sometimes exceeding brine and mineral storage—and permanent CO₂ sequestration is achievable.

Abstract

Summary We present the results of compositional reservoir simulation of a prototypical CO2 sequestration project in a deep saline aquifer. The objective was to better understand and quantify estimates of the most important CO2 storage mechanisms under realistic physical conditions. Simulations of a few decades of CO2 injection followed by 103 to 105 years of natural gradient flow were performed. The impact of several parameters was studied, including average permeability, the ratio of vertical to horizontal permeability, residual gas saturation, salinity, temperature, aquifer dip angle, and permeability heterogeneity. The storage of CO2 in residual gas emerges as a potentially very significant issue meriting further study. Under some circumstances this form of immobile storage can be larger than storage in brine and minerals. Most importantly, we find that permanent storage is feasible. That is, the storage process can be designed to place large volumes of CO2 in forms that will not escape the aquifer any faster than fluids originally present in the aquifer.