Successful Wettability Alteration Pilot in an Offshore Reservoir: Laboratory Analysis to Support Planning, Implementation and Interpretation

Summary Wettability Alteration from oil-wet to water-wet condition is a very promising EOR technique for producing significant incremental oil recovery from oil-wet carbonate reservoirs. A thorough lab program led to the development of the wettability altering surfactant formulation for a giant offshore carbonate reservoir. The field implementation was done in a systematic step wise manner to mitigate the risk in implementing such a technology field wide. A long term surfactant injection pilot was then conducted to evaluate efficacy of developed solution at field scale. Post surfactant injection, a rigorous Monitoring and Surveillance program was put in place to carefully monitor production data and quantify incremental oil gains. Surfactant injection was done in a continuous mode at 4,000 ppm active concentration in sea water for 7 months followed by sea water injection. Surfactant injection didn’t result in any injectivity loss or formation of any viscous emulsions in the reservoir. An injector where surfactant was injected (Injector-01) gained 8% yearly injectivity as a result of the surfactant injection. Incremental oil response was observed for both producer wells for the pattern. There was no surfactant breakthrough observed from produced water analysis till now.