The Study Of The Best Polymer Displacement Way On The Second Reservoir

The oil displacement efficiency of polymer solution in porous media is decided by the ratio of viscous liquid by displacement pressure gradient and residual oil retention force.The viscoelasticity changes of polymer solution in different Seepage environment in the reservoir is the key to affect the oil displacement efficiency and oil displacement mechanism,is also the basis for polymer flooding reservoir engineering calculation,analysis and guidance for the field application.In this paper,by using the data of conventional mercury injection and constant speed mercury injection,the pore structure characteristics of different permeability class ii reservoirs was analysed,and pore structure differences between the main reservoirs and the class ii reservoirs was studied by the CT scan technology.By the use of polymer seepage experiment,study the change rule of the polymer solution viscoelasticity in different seepage velocities.By using the simplified pore model seepage calculation,analysis the seepage characteristics of different viscoelastic polymer solution.By the use of visual core model and the indoor displacement experiment,study the change rule of the microscopic oil displacement efficiency in the change process of viscoelastic system with different pore throat ratio.By carrying out the indoor experiment of polymer injection,study the injectivity of different polymer solution in class ii reservoirs.By carrying out polymer oil displacement experiment,study the oil displacement efficiency of different viscoelastic polymer in class ii reservoirs.The resutls show that,based on the analysis of the pore structure data of conventional mercury injection and constant pressure mercury,with the combination of class ii reservoirs pore structure of CT scan results,average pore throat ratio distribution of class ii reservoirs is 6.68?22.65,with the increase of permeability,average pore throat ratio decreases.Using the high seepage experiment simulates the seepage process of polymer solution near the bottom of injection-production well.With the increase of polymer molecular weight and concentration,viscosity retention rate reduces,the experimental system of polymer viscosity retention rate is 48.15?74.08%.During the seepage in the middle distance,viscosity retention rate is 83.45%,and the average molecular weight retention rate is 90.97%,this shows that in the middle of reservoir seepage process,shearing has little effect on the properties of polymer solution.In the same condition of throat radius,with the entrance flow rate increases or the pore throat ratio decreases,microscopic displacement efficiency of the polymer solution decreases.Under the same pressure gradient conditions,with the increase of polymer We and relaxation time,the micro sweep efficiency increases,microscopic displacement efficiency increases gradually.Visual model of oil displacement experiment shows that:in the same pore throat ratio conditions,with the increase of polymer viscoelasticity,residual oil in the simulation of pore model is gradually reduced.With the increase of the pore throat ratio,incremental oil effect of viscoelastic polymer become worse.In the core seepage experiment of different permeability,with the increasing of injection rate,injection pressure does not rise continually,this shows that blocking does not occur in the seepage process of polymer.With the increase of the polymer concentration and molecular weight,resistance coefficient and residual resistance factor increase.Polymer solution injectivity can be improved by means of reducing the average molecular weight of polymer injection system,mass concentration,or injection rate.Base on the oil displacement experimental results indoor and numerical simulation results,to the class ii reservoirs with the permeability is 500×10-3?m2,the best oil displacement effect can be received,when the polymer system composition is the relative molecular mass of 25 million,concentration 1.5g/L,and the injection speed is 0.125 PV/a.To the class ii reservoirs with the permeability is 300×10-3?m2,the best oil displacement effect can be received,when the polymer system composition is the relative molecular mass of 16 million,concentration 1.5g/L,and the injection speed is 0.25 Pore volume per year.