Compatibility Study Of Polymer Flooding In Bohai Conventional Heavy Oil Reservoirs

The heavy oil reserves in Bohai oilfield are abundant,field polymer flooding test shows that the increase of oil recovery is about 6%,which shows great application value.The average viscosity of underground crude oil in polymer flooding is 70mPa s,and the viscosity range of crude oil in conventional heavy oil in Bohai is 50-350mPa s.The crude oil with viscosity exceeding 70Pa s occupies more than 40%of the conventional heavy oil reserves.If polymer flooding can be carried out at higher viscosity,it will have great potential for development.Therefore,it is necessary to establish the matching relationship between the polymer performance and the viscosity of the crude oil,so as to provide guidance for heavy oil polymer flooding.Through the experiment of artificial homogeneous core flooding,it is found that the displacement effect of polymer with different properties is different,and the effect of polymer flooding is getting worse with the increase of viscosity of crude oil.Because the effect of polymer flooding is affected by both the performance of polymer and the viscosity of crude oil,it is difficult to evaluate the matching relationship between the viscosity of crude oil and the properties of the polymer by simply relying on the physical experiment.Therefore,based on the result of the oil displacement experiment of the heterogeneous core,a numerical simulation water flooding model is established for the heterogeneous core of the SZ36-1 oilfield.On the basis of the water flooding model,we fit the simulation results of polymer flooding with the experimental results by adjusting the effective viscosity and the adsorption amount of the polymer solution reasonably.Because the residual resistance coefficient of the polymer is a function related to the adsorption amount,the simulation test of 2 factors(effective viscosity and residual resistance coefficient)of the 7 kinds of crude oil viscosity is reasonably arranged by uniform design method,and 77 numerical simulations have been completed.Through mathematical analysis of numerical simulation results,a prediction model of polymer flooding effect is established.By using this model,we get the following understanding.(1)According to the effective viscosity and the residual resistance coefficient of the polymer,the maximum injection pressure and the final recovery of polymer flooding can be predicted,so the matching relationship between the performance of polymer and the effect of oil displacement can be evaluated efficiently.(2)Under the same injection pressure,the recovery rate obtained by different polymer properties is different.To obtain higher oil recovery,polymer should have higher residual resistance coefficient When the viscosity of crude oil is large,polymer should also have a certain viscosity.(3)Under the condition of inhomogeneous,the main function of high viscosity polymer is to stabilize the water flooding front during the displacement process.and reduce the difference of water absorption between different layers.Polymer with high residual resistance coefficient increased the water absorption of high permeability layer and increased the recovery of high permeability layer based on the higher resistance capability.At the same time,the final recovery and maximum injection pressure calculated by the prediction model of polymer flooding effect are in good agreement with the numerical simulation results.Therefore,the model can be used to establish the matching relationship between the polymer performance and the viscosity of the crude oil.