Abstract
Mineral reactive surface area (RSA) is one of the key factors that control mineral reactions, as it describes how much mineral is accessible and can participate in reactions. This work aims to evaluate the impact of mineral RSA on numerical simulations for CO2 storage at depleted oil fields. The Farnsworth Unit (FWU) in northern Texas was chosen as a case study. A simplified model was used to screen representative cases from 87 RSA combinations to reduce the computational cost. Three selected cases with low, mid, and high RSA values were used for the FWU model. Results suggest that the impact of RSA values on CO2 mineral trapping is more complex than it is on individual reactions. While the low RSA case predicted negligible porosity change and an insignificant amount of CO2 mineral trapping for the FWU model, the mid and high RSA cases forecasted up to 1.19% and 5.04% of porosity reduction due to mineral reactions, and 2.46% and 9.44% of total CO2 trapped in minerals by the end of the 600-year simulation, respectively. The presence of hydrocarbons affects geochemical reactions and can lead to net CO2 mineral trapping, whereas mineral dissolution is forecasted when hydrocarbons are removed from the system.
Highlights
Geological carbon sequestration (GCS) is a critical component in accomplishing the goal of net-zero or carbon neutrality set by governments and industries [1,2,3], as it provides an enormous estimated storage capacity, and its efficacy has been successfully demonstrated many times by pilot-scale and field-scale projects worldwide [4]
This study is built upon this previous Farnsworth Unit (FWU) work and focuses on risk assessments associated with reactive transport, in particular mineral reactive surface areas
The 87 combinations were simulated to study the ranges of uncertainty in mineral precipitation/dissolution and CO2 mineral trapping caused by using different mineral reactive surface area (RSA) values
Summary
Geological carbon sequestration (GCS) is a critical component in accomplishing the goal of net-zero or carbon neutrality set by governments and industries [1,2,3], as it provides an enormous estimated storage capacity, and its efficacy has been successfully demonstrated many times by pilot-scale and field-scale projects worldwide [4]. One particular trapping mechanism, the mineral trapping of CO2, is often ignored in storage forecasts for CO2-EOR projects, such as Jia et al, 2016 [6], even though mineral trapping is the most secure mechanism to sequester CO2 in the long term. Due to the lack of geochemical modeling in these forecasts, the processes of CO2 dissolution and its presence in aqueous ions are ignored. Understanding the geochemical interactions between CO2, in situ fluid, and formation, is critical to ensure long term CO2 conformance and to mitigate the risks of groundwater contamination due to CO2 leakage
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