Does impure CO2 impede or accelerate the onset of convective mixing in geological storage?

- Linear stability analysis of impure CO2 storage in deep saline aquifers is presented.
- Role of impurities on the onset of convective mixing is characterized.
- H2S has a potential to accelerate the onset of convective mixing.
- Composition of impurity can be engineered to accelerate the onset of mixing.

We have conducted a linear stability analysis to investigate the effect of impurity in CO2 stream on the onset of convective mixing associated with impure carbon dioxide (CO2) storage in deep saline aquifers. It has been generally thought that injecting impurities such as hydrogen sulphide (H2S) and nitrogen (N2) along with carbon dioxide impedes the buoyancy-driven instabilities resulting in less efficient CO2 solubility trapping. In this work, we have for the first time shown that in contrary to the original thought informed inclusion of an impurity such as H2S has a potential to accelerate the onset of buoyancy-driven instabilities and possibly leading to more effective solubility trapping. This result improves our understanding of the storage of impure CO2 streams in deep saline aquifers and uncovers a new area for further research.

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