Studies on EOR of Sandstone Oilfield with Low Viscosity and High Salinity During High Water Cut Stage—A Case Of Kumkol Oilfield in Kazakhstan

Abstract

Based on Kumkol oilfield in Kazakhstan with low viscosity and high salinity of injected water during high water cut stage, the remaining oil distribution is studied and the EOR method is optimized. Through the numerical reservoir simulation and reservoir engineering theory, the remaining oil distribution pattern of reservoirs with low-viscosity oil ( 30,000 mg/l) during high water cut stage is analyzed, and the simulation experiments evaluated the performance index of different surfactant and polymer, selected the suitable salt-resistant polymer (125 VM) and surfactant (AB), and comprehensively evaluated the displacement effect of the different combination modes of displacement system; then, the suitable EOR method for this oilfield is put forward. According to Buckley-Leverett flooding theory, the reservoirs with high-viscosity oil are compared, under the same degree of recovery; the dimensionless distance of waterflood front in reservoirs with low-viscosity oil is shorter; the oil–water two-phase region is narrower with high oil displacement efficiency; and remaining oil is enriched in the un-swept areas. The result of simulation experiments shows that, under the condition of high salinity of injected water and low-viscosity oil, polymer–surfactant system could significantly improve the oil recovery.A recovery increment of 10.3% could be achieved when the polymer–surfactant system was injected with a slug of 0.167 PV. According to the characteristics of remaining oil distribution in Kumkol oilfield, the research results can greatly increase the oil recovery and improve the development effectiveness of Kumkol oilfield during high water cut stage.