Optimize carbon dioxide sequestration, enhance oil recovery

(Phys.org) —Los Alamos researchers and collaborators from the University of Utah have created a generic integrated framework simulation to optimize carbon dioxide (CO₂) sequestration and enhance oil recovery (CO₂-EOR) based on known parameter distributions for a depleted oil reservoir in Texas. CO₂-EOR is a technique in use for over 40 years to produce 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. The simulation provides an important approach to estimate the potential of storing CO₂ in depleted oil fields while simultaneously maximizing oil production. The journal Environmental Science & Technology Letters published the research.

Significance of the research

CO₂-EOR provides about 5 percent of the total U.S. current crude oil production. Due to carbon capture and storage technology advances, prolonged high oil prices and the potential availability of large anthropogenic CO₂ sources, CO₂-EOR could expand in the next few decades. The technology uses water-alternating-with-gas cycles to control CO₂ mobility and CO₂ flood conformance and to tackle the clogging and scale issues in the depleted reservoir.

However, there are a few operational and technical issues to be resolved for CO₂-EOR expansion to commercial scales: 1) uncertainty in characterizing CO₂-water-oil systems in depleted reservoirs, 2) lack of robust guidelines for determining injection and production well distances, 3) difficulty in determining the time ratio for water alternating CO₂ gas injection, and 4) difficulty in controlling the CO₂ flood conformance and monitoring the flood performance. If the first three issues can be quantitatively evaluated and solved, the results will indirectly help solve the fourth issue of CO₂ flood conformance and performance evaluation.

The LANL and University of Utah researchers developed a generic integrated framework simulation to optimize CO₂ sequestration and enhance oil recovery based on known parameter distributions for a depleted oil reservoir. The framework consists of a multi-phase reservoir simulator coupled with geologic and statistical models. The results from this study provide insights to understand the potential and uncertainty of commercial-scale CO₂-EOR.

Research achievements

The team conducted an integrated simulation of CO₂-water-oil flow and reactive transport, followed by a global sensitivity and response surface analysis. The source of CO₂ used by the test came from a fertilizer plant in Borger, TX, and an ethanol plant in Liberal, KS. The results optimized the CO₂-EOR process. The scientists found that the reservoir permeability, porosity, thickness, and depth are the major 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 to design a five-spot CO₂-EOR pattern that efficiently produces oil while storing CO₂.