Inference of pattern-based geological CO2 sequestration and oil recovery potential in a commingled main pay and residual oil zone CO2-EOR flood
Geoenergy Science and Engineering
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Abstract
everal detailed studies have shown that residual oil zones (ROZs) can present significant resources for additional hydrocarbon recovery as well as subsurface carbon dioxide (CO2) sequestration via enhanced oil recovery by injecting CO2 (CO2-EOR). Field development strategies included new wells drilled dedicated to main pay zones (MPZ) and ROZs, or existing wells in MPZs deepened to ROZs for commingled injection-production using different well patterns. The latter presented a challenge when discerning the injection and production from each of the zones, and for subsequent quantification of CO2 sequestration and EOR potential from different patterns and from the field.
In this paper, an innovative method for analyzing commingled injections and productions from MPZs and ROZs, with application to pattern-based data from four staggered line drive patterns in Wasson Field's Denver Unit, Texas, USA, was developed. Decline curve and ratio-trend methods were used as means of history-matching and forecasting. Cumulative production-time and cumulative production-rate data for oil, gas, and water, as well as water-oil ratio (WOR) and gas-oil ratio (GOR), were analyzed along with injection data for time intervals covering major injection events in MPZ, or MPZ and ROZ combined. A combined analysis enabled inference of allocation of fluids into different zones during WAG (water alternating gas) injection and thereby estimation of CO2 storage, utilization, and retention in different zones as a function of total injection. Results show that ROZs generally present higher CO2 sequestration potential compared to MPZs, and a comparable incremental oil recovery factor of ∼20%, on average. Results based on ratio analysis further show that while the WOR trend of the pattern production is mostly dominated and controlled by ROZ, GOR is controlled by both intervals. Although the method relying on decline curves and the approach used in zonal fluid allocations are subject to their limitations, this study presents a practical and innovative well-pattern-based method to infer and forecast CO2 sequestration and oil recovery quantities and fluid ratios from MPZs and ROZs in commingled operations and highlight the added potential offered by ROZs.
Suggested Citation
Karacan, C.O., Attanasi, E., Brennan, S., Warwick, P., 2026, Inference of pattern-based geological CO2 sequestration and oil recovery potential in a commingled main pay and residual oil zone CO2-EOR flood: Geoenergy Science and Engineering, v. 260, 214414, 15 p., https://doi.org/10.1016/j.geoen.2026.214414.
Study Area
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Inference of pattern-based geological CO2 sequestration and oil recovery potential in a commingled main pay and residual oil zone CO2-EOR flood |
| Series title | Geoenergy Science and Engineering |
| DOI | 10.1016/j.geoen.2026.214414 |
| Volume | 260 |
| Publication Date | February 12, 2026 |
| Year Published | 2026 |
| Language | English |
| Publisher | Elsevier |
| Contributing office(s) | Geology, Energy & Minerals Science Center |
| Description | 214414, 15 p. |
| Country | United States |
| State | Texas |
| Other Geospatial | Denver unit, Wasson field |