CO2 Foam Pilot in a Heterogeneous Carbonate Reservoir: Analysis and Results

Abstract

A CO2 foam pilot was conducted in a heterogeneous carbonate reservoir in East Seminole Field, Permian Basin USA. The primary objective was to achieve in-depth CO2 mobility control to increase CO2 sweep efficiency and improve oil recovery in an inverted 40 acre 5-spot pattern. Foam was injected in a rapid surfactant-alternating-gas (SAG) strategy with 10 days of surfactant solution injection followed by 20 days of CO2 injection. We implemented a laboratory to field upscaling approach which included foam formulation screening, numerical modeling, and field monitoring to verify foam generation and CO2 mobility reduction. The monitoring campaign obtained baseline before the pilot and monitored reservoir response to foam injection. This included conducting baseline and pilot phase CO2 and water injection profile logs, interwell CO2 tracer tests and collecting injection bottom hole pressure data and flow rates. Transient analysis was also conducted to assess foam development at reservoir conditions. The effectiveness of foam in improving overall recovery was also evaluated. Results indicate that foam was generated and CO2 mobility was reduced during the pilot based upon higher differential pressures during the SAG cycles compared to an identical water-alternating-gas (WAG) cycle. CO2 breakthrough was also delayed with foam compared to the baseline test without foam. Injection profile logs from the foam injector showed that flow increased into unswept reservoir intervals and was diverted from a high permeability streak. The effectiveness of foam in improving the overall oil recovery revealed that the foam pilot produced 30% more oil than the pattern's projected performance without foam, despite injecting at half of the historical rate during the pilot. This work presents the complete field results and analysis from the successful implementation of CO2 foam mobility control.