Simulation of carbon dioxide mineralization and its effect on fault leakage rates in the South Georgia rift basin, southeastern U.S.

Over the past few decades, measured levels of atmospheric carbon dioxide have substantially increased. One of the ways to limit the adverse impacts of increased carbon dioxide concentrations is to capture and store it inside Earth's subsurface, a process known as CO sequestration. The success of this method is critically dependent on the ability to confine injected CO for up to thousands of years. Establishing effective maintenance of sealing systems of reservoirs is of importance to prevent CO leakage. In addition, understanding the nature and rate of potential CO leakage related to this injection process is essential to evaluating seal effectiveness and ultimately mitigating global warming. In this study, we evaluated the impact of common chemical reactions between CO and subsurface materials in situ as well as the relationship between CO plume distribution and the CO leakage within the seal zone that cause mineralization. Using subsurface seismic data and well log information, a three-dimensional model consisting of a reservoir and seal zones was created and evaluated for the South Georgia Rift (SGR) basin in the southeastern U.S. The Computer Modeling Group (CMG, 2017), was used to model the effect of CO mineralization on the optimal values of fault permeability permeabilitydue to fluid substitution between the formation water and CO. The model simulated the chemical reactions between carbon dioxide and mafic minerals to produce stable minerals of carbonate rock that form in the fault. Preliminary results show that CO migration can be controlled effectively for fault permeability values between 0.1-1 mD. Within this range, mineralization effectively reduced CO leakage within the seal zone.