CO2 has been previously utilized to enhance oil recovery (EOR) in numerous reservoirs. These hydrocarbon-depleted CO2-filled reservoirs are a ticking time bomb for potential leaks. Accurate leakage estimation is essential to assess the effectiveness of CO2 sequestration and groundwater protection. We developed reduced-order models to accurately and quickly estimate the CO2 and oil components (e.g., CH4) leakages from the abandoned wells. We conducted a wellbore leakage analysis for the CO2-EOR field. We designed a numerical model with an aquifer, caprock, and reservoir components. We used C1, C4, and C10 to represent the light, intermediate and heavy components of crude oil, respectively. We quantified the CO2/oil components leakage through the wellbore to the aquifer. Then, we performed Monte Carlo simulations to quantify the inherited uncertainty in the model parameters. After that, we developed and compared the performance of a set of reduced-order models (ROMs) to predict CO2/oil component leakages through an abandoned wellbore. In addition to a large amount of CO2 leakage, we observed that hydrocarbons leakage through the wellbore poses a potential risk of groundwater contamination. In addition, we observed that CO2 and hydrocarbons leakage profiles are highly sensitive to the wellbore permeability. Moreover, we reported the performance of three ROM development techniques where we found that the Light Gradient Boosting Machine (LGBM) surpasses both the linear regression and Multivariate Adaptive Regression Splines. This is one of the first studies to quantitatively evaluate leakage profiles from CO2-EOR sites and draws attention to further investigation and analysis.
Geological sequestration and utilization of CO2 is a viable technique to lessen the current emissions levels and provide a solution to the current climate crisis (Yamasaki 2003). Various subsurface systems could be potential storage sites for CO2, including saline aquifers and depleted oil and gas reservoirs (Benson and Cole 2008). On the other hand, CO2 could enhance the hydrocarbon recovery from live hydrocarbon reservoirs by providing pressure maintenance or improving hydrocarbon mobility (Mehana et al. 2018). In addition, CO2 could be utilized to engineer methane production from clathrate hydrate systems.