Physical experiments and numerical simulations of viscosity reducer flooding for ordinary heavy oil

Highlights

• Water-soluble viscosity reducer flooding for ordinary heavy oil reservoirs was put forward.

• Oil displacement performance and the mechanisms of enhancing oil recovery of viscosity reducer flooding was studied.

• The non-linear mixing rule can describe the relationship between oil viscosity and viscosity reducer concertation.

• The pilot tests show that viscosity reducer flooding has a significant effect oil increase.

Abstract

In order to overcome disadvantages of thermal recovery technologies such as high cost and air pollution, chemical flooding for ordinary heavy oil by viscosity reducer flooding was studied. The EOR mechanisms of viscosity reducer flooding to improve heavy oil recovery were studied by physical experiments and numerical simulation methods. First, the performance of the viscosity reducer was evaluated, then the injection characteristics and oil displacement performance were studied through core oil displacement experiments, the mechanism of oil recovery improvement by the viscosity reducer was studied through microscopic visualization experiments, and finally a comparison was made between indoor physical experimental results and numerical simulations. The results showed that the process of viscosity reducer flooding can form a stable oil-in-water emulsion. The process of water flooding can be divided into three stages: the starting pressure breakthrough stage, the rapid pressure decline stage, and the low pressure operation stage. Viscosity reducer flooding reduced the starting pressure gradient and the displacement pressure, while the oil recovery factor was increased by 12.4%, and the total recovery reached 46.6%. The main mechanism of improving oil recovery by a viscosity reducer is to reduce the crude oil viscosity and the residual oil saturation. By using the nonlinear mixing rule, the variation rule of crude oil viscosity with the viscosity reducer concentration was obtained, which can be directly applied to reservoir numerical simulations. A pilot test showed that the water cut was decreased and oil production was increased, which also reduced the injection pressure and gave all the production wells improved oil production.