An Integrated Framework for Optimizing CO₂ Sequestration and Enhanced Oil Recovery

TLDR

CO2‑EOR injects CO₂ and water to recover oil, and because much of the CO₂ remains in the reservoir, it also provides a means of permanent CO₂ sequestration. The study proposes a generic integrated framework to jointly optimize CO₂ sequestration and enhanced oil recovery for a depleted Texas reservoir using known parameter distributions. The framework couples a multiphase reservoir simulator with geological and statistical models, performing CO₂‑water‑oil flow and reactive‑transport simulations followed by global sensitivity and response‑surface analysis to guide process optimization. Permeability, porosity, thickness, and depth dominate the net CO₂ storage and oil/gas recovery, while well spacing and alternating CO₂‑water injection sequences are key operational controls for an efficient five‑spot pattern that simultaneously produces oil and stores CO₂, offering insights into commercial‑scale CO₂ sequestration uncertainty.

Abstract

CO2-enhanced oil recovery (CO2-EOR) is a technique for commercially producing oil from depleted reservoirs by injecting CO2 along with water. Because a large portion of the injected CO2 remains in place, CO2-EOR is an option for permanently sequestering CO2. This study develops a generic integrated framework for optimizing CO2 sequestration and enhanced oil recovery based on known parameter distributions for a depleted oil reservoir in Texas. The framework consists of a multiphase reservoir simulator coupled with geologic and statistical models. An integrated simulation of CO2–water–oil flow and reactive transport is conducted, followed by a global sensitivity and response surface analysis, for optimizing the CO2-EOR process. The results indicate that the reservoir permeability, porosity, thickness, and depth are the major intrinsic reservoir parameters that control net CO2 injection/storage and oil/gas recovery rates. The distance between injection and production wells and the sequence of alternating CO2 and water injection are the significant operational parameters for designing a five-spot CO2-EOR pattern that efficiently produces oil while storing CO2. The results from this study provide useful insights for understanding the potential and uncertainty of commercial-scale CO2 sequestrations with a utilization component.