Evaluation of the Impact of Geomechanical and Geochemical Variability on Offshore CO₂ Storage in the South Georgia Embayment

Adil Alshammari¹, Venkataraman Lakshmi², Camelia Knapp³, and James H. Knapp³

1. School of the Earth, Ocean, and Environment, University of South Carolina, United States

2. Department of Engineering Systems and Environment, University of Virginia, United States

3. School of Geology, Noble Research Center, Oklahoma State University, United States

Abstract: CO₂ sequestration, Mineralization, Geomechanics, Geochemical, porosity, tensile failure, fracturing pressure. Sequestration of carbon dioxide is an essential method to address carbon dioxide emissions resulting from anthropogenic activities. When this method is implemented, a potential location for CO₂ injection must meet the storage capacity demand for commercial CO₂ sequestration. This is because large-scale injection can result in leakage, which undermines the efforts to combat global warming. Tensile failure and mineralization are among many expected issues that need to be studied for such large-scale storage. In this study, we evaluated the relationship between the tensile failure of a reservoir seal and mineralization to maintain effective CO₂ storage. CO₂ injection in a reservoir at high rates rapidly increases pore pressure around the injection well. In the case that this happens under constant total stress, the effective normal stress begins to decrease due to the increased hydraulic injection pressure. When the hydraulic pressure exceeded the effective normal stress, tensile failure occurred. This created various tiny channels, and their resulting conductivity allowed the CO₂ plume, particularly the portion in the gas phase, to pass through these channels into the upper part of the seal. The tensile failure then temporarily increased the permeability values until mineralization fixed the increase in permeability. The Barton-Bandis fracture permeability model was applied to study the tensile failure in the seal. Through this model, mineralization combined with tension failure caused changes in the porosity network upon CO₂ plume migration.

Key words: impact, geomechanical and geochemical variability, offshore CO₂ storage, South Georgia Embayment