Field Implementation of Polymer EOR Technique - A Successful Experiment in India

ONGC has implemented a large scale polymer flood project in Sanand oil field which lies in Ahmedabad-Mehsana block of Cambay Basin in India. The project is well under way and is designed to improve the mobility and sweep efficiency in highly heterogeneous sandstone reservoir. Adverse water flood characteristics were identified and extensive laboratory work was undertaken to demonstrate the benefits of reducing water mobility by increasing viscosity with PHPA polymers. Displacement experiments on long cores and sand packs were used to design the polymer flood slug size and the graded polymer concentrations. On the basis of laboratory work, a pilot was designed and implemented which was followed by an expanded pilot. Encouraging results in both the phases led to the fieldwide commercial application of the process. Facilities have been developed to ensure proper testing of chemicals before use, low-shear polymer injection, optimum use of biocides, oxygen scavengers and monitoring of injection fluid quality. This paper aims to present main features of laboratory work, pilot, expanded pilot and fieldwide commercial application of polymer flood in Sanand field. The data generated and presented in this paper shows that a properly designed polymer flood is economically attractive as it significantly improves sweep efficiency therby improving ultimate recovery.