High Molecular Weight Polymer Injection in Polymer Flood EOR Project South Oman: Achieving More Oil with Less Polymer

Abstract Since commencement, full field polymer flood application in Marmul field located in southern of Oman has been a worldwide successful polymer enhanced oil recovery project. This project was effective in realizing incremental oil volume on top of water flood, with recent realization of the highest polymer oil gain since the beginning of polymer flood project life cycle. Oil daily rate improved to double comparing to previous years with the same well stock. This achievement was a result of many initiatives like data automation, improvements on troubleshooting, increase in polymer viscosity, high sustainable polymer pump uptime and better equipment maintenance to minimize mechanical issues. Integrated team effort and collaboration between petroleum engineers, production chemists and operation team helped to significantly improve polymer flood performance. Partially hydrolyzed polyacrylamide (HPAM) of a molecular weight of around 20 million Daltons has been used in the project since its start date with target viscosity of around 15 cP at relatively low brine salinity (~5000 ppm) and reservoir temperature (46 °C). In the polymer plant, stabilizing package (isopropanol, thiourea and water, (ITW) has been added to the polymer solution to enhance long-term viscosity stability of the polymer at reservoir conditions. Entire polymer mixing facilities are nitrogen blanketed and maintained in an anaerobic condition. Given that polymer projects are OPEX driven (mainly by chemical consumption), the team has successfully piloted an initiative to increase the polymer molecular weight from around 20 to 25 million Daltons, hence, reducing polymer dosage by 20-25% to achieve target viscosity of 15 cP. This led to the implementation of full field injection of the high molecular weight polymer. The new self-stabilized polymer has been selected based on its excellent injectivity performance validated by labs and field pilot trial. This project is expected to yield savings in the opex & improving the overall project UOC attributed to the use of self-stabilized high molecular weight polymer by eliminating ITW package and achieving viscosity with low concentration.