Abstract The Mangala field in the Rajasthan state of western India was the first major oil discovery in the Barmer Basin. It contains over 1 billion bbls of paraffinic oil with average viscosity of ~15cp and wax appearance temperature only ~5°C less than reservoir temperature. The initial development plan is a hot waterflood to prevent in situ wax deposition; however, chemical EOR methods are expected to play an important role in the ultimate field development strategy.
EOR assessment was part of the initial field development planning process. Screening studies were conducted soon after discovery followed by comprehensive laboratory evaluations of chemical flood potential which had been identified as the most suitable process. The laboratory evaluation along with parametric simulation studies indicated significant chemical EOR potential. A closely spaced normal 5-spot pilot was designed to test chemical EOR processes in the early part of the field development. Logging observation wells are strategically placed in the pilot to periodically monitor changes in oil saturation.
The initial waterflood phase in the pilot has been completed and injection of the polymer slug is in progress. Comprehensive monitoring and quality control procedures are being followed to ensure smooth operations. Extensive PLTs, time-lapse saturation and resistivity logs, pressure surveys, tracer surveys, detailed produced fluid analyses and tests for monitoring the quality of injected fluids are all performed routinely. Dynamic reservoir modeling has been a critical part of the analysis to understand polymer flood behavior. The initial polymer flood phase in the pilot will be followed by ASP (alkaline-surfactant-polymer) injection for further evaluation of chemical EOR potential.
This paper discusses the operational aspects of polymer flood facilities, quality control and monitoring program followed, challenges faced, polymer injection results and plans for future ASP injection.