Experimental Research On Sweep Coefficient And Oil Displacement Efficiency Of Polymer Flooding

Nowadays, we have gained various important fruits and cognitions on oil-water displacement efficiency and sweep efficiency. However there are some different cognitions on accurate evaluation indexes of displacement efficiency and sweep efficiency, the displacement mechanism of polymer flooding is not very clearly, so we need some thoroughly study on it. By the numerical simulation and core flooding tests with three-dimensional heterogeneous physical model and parallel natural core, we thoroughly studied on the flow mechanism of polymer flooding and variation characteristic of displacement efficiency and sweep efficiency. And provide the increasing extent of displacement efficiency and sweep efficiency quantitatively.The core flooding test and numerical simulation results shows, the main effect of polymer flooding is to increase the sweep coefficient, especially the sweep coefficient of middle and low-permeability layers. The mechanisms of polymer flooding are:(1)The decrease of mobility ratio improves the sweep coefficient of polymer flooding;(2)The shear stress of the polymer solution increase so it can displace the island and flim remaining oil;(3)The visco-elasity of he polymer solution can reduce the amount of the"dead-ends"remaining oil. The increasing of oil recovery is differently in different layers, it increased about 17.74%, 22.21% and 8.20 at the low, middle and high-permeability layer. As to the contribution of polymer flooding enhanced oil recovery, the contribution is about 30.86%, 48.35% and 20.79% at low, middle and high-permeability layer. Polymer flooding can improve the oil displacement efficiency by about 8%. In a heterogeneous model with interlayer, the sweep coefficient can be increased about 21.9%, 10.1% and 7.1% at the low, middle and high-permeability layer respectively;while in a heterogeneous model without interlayer the sweep coefficient can be increased about 42.2% and 23.4% at the low and middle-permeability layer respectively. The sweep coefficient of the model without interlayer is a little lower than that of the model with interlayer, however, the increase of the sweep coefficient is inverse.