Performance of Polymer Flood in Sanand Field, India-A Case Study

Abstract

Abstract Twenty two years of history of polymer flood in KS-III sand in Sanand field, Gujarat State, India, proves the efficacy of the process in a reservoir of 85°C temperature. KS-III sand of Middle Eocene age, is one of the few successful cases of polymer flooding in such high reservoir temperature. Reservoir is acting under partial edge water drive. Oil viscosity of 20 centi poise led to adverse mobility ratio which resulted in cusping of water in structurally higher wells. Hence polymer flood was considered the best option in this reservoir for improving mobility ratio of oil and overall areal and volumetric sweep efficiency which was also supported by the laboratory studies on native cores of the field. Polyacrylamide polymer was selected for injection. Polymer flood process in Sanand field has undergone many stages of implementation. After initiation of polymer pilot in an inverted five spot pattern in 1985 with one injector, 4 producers and one monitoring well, it was extended to four inverted five spot patterns in 1993 with nine producers and four injectors. Effect of the injection was visible in terms of reduction in water cut, improvement in oil production and increase in reservoir pressure. Success of pilot projects encouraged to full scale field implementation in 1996–97. Polymer injection was done in peripheral pattern in the main part of the field. Subsequent reviews have been carried out from time to time and mid course corrections have been taken accordingly. Current paper discusses different stages of development in polymer flood, the steps taken from time to time, lessons learnt and conclusions drawn on the basis of practical experience and reservoir simulation.