Oil displacement efficiency evaluation of variable viscosity polymer slug alternative injection

Aiming at the issues caused by polymer single-slug injection, to improve the oil displacement efficiency in heterogeneous layers through variable viscosity polymer slug alternative injection technique was addressed in this paper. Successive injecting the polymer slugs with different viscosities into the anisotropy reservoirs make the high viscosity polymer flow into high permeability layers to decrease the velocity of fluid, and then make sure the following low viscosity fluid drain to zones with low permeability, which could narrow the mobility differences between reservoirs of high and low permeability. The experimental results show that alternative injection raises the amount of fluid absorption in layers of low permeability, and the diversion ration carves in these layer transfers from shape “∧”to “∩” . The increase of EOR by alternative injection method is higher than that by single slug injection, and the former technique also reduce the polymer consumption by a quarter. This research provides a reference for optimizing the injection method of polymer flooding technique.