Pilot to Full-Field Polymer Application in One of the Largest Onshore Field in India

Abstract

Abstract The paper discusses the full-field polymer flood implementation plan post successful pilot result in one of the largest onshore fields in India. Mangala field contains multi-Darcy sandstones that have high porosity and very low connate water saturation and low temperature (65 degC). The connate water salinity is low (~6500 total dissolved solids), The crude is waxy and viscous, which results in unfavorable mobility for water-flooding, Chemical flood was identified as a potential EOR method during a screening study. A normal 5 spot polymer flooding pilot has been conducted and results are encouraging in terms of additional oil recovery and reduction of water cut. Additionally much has been learnt about how to optimize the surface facility, polymer preparation, and polymer quality monitoring. Following the successful completion of the pilot, it is planned to implement a polymer flood for the fullfield. All the lab results and pilot learnings have been incorporated to minimize the uncertainty and risks. Different subsurface injection pattern concepts have been evaluated based on the reservoir characteristics. Various parameters like pattern and number of wells, polymer viscosity, tapered vs. fixed concentration, polymer slug sizes and other variables have been optimized and are discussed in the paper. Sensitivities to capture the impact of polymer adsorption, implementation schedule, conformance in injectors, visco-elastic effect of polymer, polymer shear thinning characteristics etc. on recovery have been studied. Learning from pilot has been used in selecting the surface facility, well design, pumping facility, selective completion for conformance control, surface pressure requirement, and designing to minimize the viscosity loss across the completion and sand face. Surface facilities concepts have been finalized to prepare concentrated polymer at a single location and pumping it to each well for injection. Polymer flooding has the potential to significantly improve the sweep efficiency in the field and to increase expected ultimate recovery (EUR). The project is one of the largest in the world in terms of scale, polymer usage, and related facility and logistics.