Long-term propagation of CO2 plume below the seal accounting for chemical reactions and water counter-flow

TL;DR

This paper presents a new analytical model for long-term CO2 plume migration beneath geological seals, explicitly considering chemical reactions and water counterflow, which enhances prediction accuracy for CO2 storage safety.

Contribution

It introduces an exact self-similar solution framework that incorporates chemical reactions and water counterflow into CO2 plume migration modeling, addressing limitations of previous models.

Findings

Chemical reaction coefficient delays CO2 arrival but accelerates final breakthrough.

Higher water velocity reduces CO2 trapping time.

Model improves long-term CO2 storage prediction accuracy.

Abstract

Accurate prediction of long-term CO2 plume migration beneath seals is crucial for the viability of CO2 storage in deep saline aquifers. Groundwater counterflow and chemical reactions between CO2, brine, and rock significantly influence plume dynamics, dispersion, and boundary evolution. This study develops a novel analytical framework by deriving governing equations for gravity-driven gas migration and obtaining exact self-similar solutions for both pulse and continuous injection. The approach explicitly incorporates chemical reactions and water counterflow, addressing factors often neglected in existing analytical models. A sensitivity analysis is conducted to evaluate the effects of key parameters on CO2 migration. The results show that increasing the chemical reaction coefficient delays the first arrival of CO2 while accelerating its final arrival, highlighting the impact of geochemical reactions on plume migration. Additionally, higher up-dip water velocity shortens the accumulation period, thereby reducing the time required for CO2 to become trapped in geological formations. These findings improve predictive capabilities for long-term CO2 storage and provide insights for optimising sequestration strategies.