Experimental Study On Optimization Of Multilayer Composite Polymer Flooding Parameters In Daqing G Block

At present,Daqing G block is in the dual high stage of high water cut and high recovery,and the conventional water drive effect is not obvious,requiring the implementation of polymer oil increase measures.The Daqing G block belongs to a narrow and small channel sand body with significant vertical geological differences.The polymer injection plan determined in the early experiments of the Daqing G block has poor adaptability to the"salt resistant"polymer system,and the production effect is limited according to the original local polymer injection plan,which affects the oil increase effect of polymer flooding development.In order to improve the development effect of Daqing G block,this article takes physical chemistry and reservoir engineering as theoretical guidance,chemical analysis,instrument detection,and physical simulation as technical means,and takes simulated core and fluid of Daqing G block reservoir as research objects to carry out experimental research on parameter optimization of multi-layer composite polymer flooding in Daqing G block.The main achievements and understanding achieved:（1）The shear resistance of"salt resistant"polymers is worse than that of ordinary polymers.The viscosity of polymer solution increases with increasing concentration,and the viscosity retention rate decreases with increasing shear time.（2）Shear action will reduce the apparent viscosity of polymer solutions,and the higher the shear rate,the greater the viscosity loss rate.The higher the polymer concentration,the higher the apparent viscosity of the polymer solution.After shearing,the retention rate of polymer viscosity:"medium"polymer<"salt resistant"polymer<"ultra high"polymer of 25million.（3）The energy storage and loss modulus increase with the increase of polymer concentration and oscillation frequency,and with the increase of relative molecular weight.All three polymer solutions exhibit better elasticity than viscosity.（4）The size of core pores increases with the increase of core permeability,while the resistance coefficient and residual resistance coefficient decrease with the increase of core permeability.The resistance coefficient and residual resistance coefficient of"salt resistant"polymer solution are greater than two types of ordinary polymers.Permeability limit of"salt resistant"polymer and"Ultra high resolution 25 million"polymer K≈500×10^-3,"mid range"polymer K≈238×10^-3。（5）The increase in oil recovery rate under different influencing factors:"ultra high content 25million"polymer>"ultra high content"polymer>"salt resistant"polymer;Step by step opening"for each small layer of polymer injection>"simultaneously opening"for each small layer of polymer injection;Multiple rounds of alternating injection>general overall injection method of profile control and displacement agent;Multiple rounds of alternating injection of"ultra high concentration 25 million"polymer solution and"medium concentration"polymer solution>Multiple rounds of alternating injection of"medium concentration"polymer solution and water>Multiple rounds of alternating injection of"high concentration"and"low concentration"polymer solution.（6）The earlier the opening time of the"heterogeneous smooth plate"core,the less the"ultra high content 25 million"polymer remains in the high permeability layer of the"separate injection and separate production"core,the smaller the seepage resistance,the worse the fluid flow diversion effect,and the smaller the increase in total recovery rate.The later the opening time of the"heterogeneous light plate"core,the more the suction amount in the middle permeable layer,and the more severe the phenomenon of"inversion of suction profile".（7）The larger the concentration and slug size of the injected polymer,the greater the increase in oil recovery,but the poorer the technical and economic benefits.Cr³⁺polymer gel has poor injectivity,which is easy to cause damage to non target layers,leading to poor effect of subsequent polymer flooding for oil increase and water reduction.