Study On Optimization Of Polymer Flooding Control In Heavy Oil Reservoirs

Polymers establish the filtrational resistance in the process of percolation by two ways:?by increasing water phase viscosity;?by establishing residual resistance factor.Polymers with high viscosity will weaken injectivity,and the high residual resistance factor will cause blockage in low permeability layer,which is not conducive to the sweep of low permeability layer.Therefore,optimizing the matching relation between the viscosity and the residual resistance factor is great significant for the selection of polymer types and development of new polymers under different types of reservoir conditions.In this paper,taking polymer AP-P4 as an example.Firstly,by testing the rheological properties of polymer solution,the functional relationship between apparent viscosity and polymer concentration and shear rate was established.On this basis,the effective viscosity of the solution in porous media was calculated based on the variable cross-section pore throat model.Then,by measuring the pressure transmission characteristics of polymer AP-P4 in porous media,the main factors causing the decrease of water permeability in polymer flooding process were analyzed.Thus,the residual resistance factor model and mathematical model of adsorption concentration of polymer solution was established separately.According to the above,the effective viscosity of polymer solution and the coefficient of permeability reduction were introduced into the motion equation of water phase,and the mathematical model of polymer flooding was established.In order to match the mathematical model with the indoor experiment,the influence factors of the apparent viscosity and permeability reduction coefficient were added in this paper.Therefore,the relative error between the experimental value and the finally calculated water cut,and both between the recovery value was within 5%.In the meanwhile,the pressure change trend was consistent.Based on the numerical simulation of polymer flooding,The effect of injection time and polymer properties on the displacement efficiency in heavy oil reservoirs was studied.(1)With the delay of the timing of injection,the ultimate recovery is reduced,but this change is not obvious.On the other hand,Early polymer flooding is more conducive to controling polymer flooding,and to inhibiting the low efficiency of water flooding cycle.(2)By using a novel alternating conditional expectation(ACE)transform nonlinear regression method,the relationship between the ultimate recovery,the maximum injection pressure and the apparent viscosity of polymer solution and the residual resistance coefficient were established to provide a significant guide for current polymer selection,even the development of new polymer.