Multi-Fold Increase in Production Through Polymer Flooding Application in Viscous Oil Active Aquifer Driven Reservoir of Mehsana Asset, India

Abstract

Abstract K Sand of Field N is highly permeable and has variation in viscosity ranging from 5cP to 120cP. K sand has been producing since 1969 and has recovered about 34%. It produces with strong edge water drive mechanism. The primary recovery is about 20-22% where viscosity is 50 to 120cP, produces oil with 90% Water cut. The early rise in water cut was because of water fingers due to adverse mobility ratio. The poor areal sweep has affected the primary recovery which necessitated the application of suitable EOR. The Polymer EOR scheme was conceptualised to address adverse mobility ratio and enhance the sweep efficiency to maximize oil production. The project area was selected for polymer flood considering the moderate primary recovery due to poor areal sweep, structurally up dip area to avoid polymer dilution through aquifer, sand continuity and good reservoir facies. In the first phase, 8 inverted five spot polymer patterns were commissioned. Injection rate is 50 m3/d/well and polymer viscosity is 27cP considering the mobility ratio and high dilution effects. The paper explains the efficient planning, monitoring activities, innovative approach to execute the scheme and mid-course correction to improve the performance of the project. The optimised project has resulted in multi-fold increase in production in challenging reservoir conditions. The project is being monitored using pattern balancing based on the production performance monitoring, polymer concentration mapping, historical exploitation, revival of vintage wells, recompletion, and perforation optimization and Injection fluid quality control. The down dip (towards aquifer) loss of polymer is controlled by monitoring liquid rates and polymer presence in the offset wells. Also, to assist the water-cut reduction in updip wells, higher drawdown strategy is implemented for polymer-bank movement in the structural highs. Monitoring of injection fluid through down hole sampling is used to ensure desired quality of polymer. Efficient monitoring of the project has resulted in production enhancement from 100tpd to 260tpd with peak production of 300tpd from targeted area. The innovative approach is to execute the project on fast track through hired injection services. This approach has helped in early realisation of oil and generation of data for preparation of expansion of polymer scheme.