Study of CO₂ EOR in a Sector Model from Mature Oil Field, Cambay Basin, India

Abstract

Among various Enhanced Oil Recovery (EOR) methods, gas injection has been proven to be one of the effective ways of enhancing oil recovery from mature fields. The field under study has approached the economic limit of production under conventional recovery methods (primary and secondary recovery). Since start of production in sixties, the field has produced 48.5 % of the initial oil in place and the water cut has increased to 89 % in April 2011. Responding to the industry needs, initially a comprehensive study was performed to evaluate the potential of immiscible CO₂ injection for the recovery of residual oil after water flooding in this mature field. This paper presents the preliminary results of immiscible CO₂ injection on the basis of laboratory studies and detailed compositional simulations carried out on a sector model of the field. Based on the results obtained from laboratory studies it was found that CO₂ injection yields significant incremental recovery. Simulation results show significant increase in field oil production, essentially from 200 to 1100 m³/day and considerable decrease in water cut were observed. In addition, detailed PVT simulations were carried out to obtain an equation of state (EOS) that would better describe the phase changes in the reservoir. These results would form the basis for carrying out CO₂ EOR simulations on a field scale.