Evaluation Of Viscoelastic Properties And Oil Displacement Effect Of Salt Resistant Polymer

There are many kinds of salt resistant polymers with different structures.At present,they are widely used in high salinity reservoirs,which can make up for the serious viscosity reduction of traditional partially hydrolyzed polyacrylamide(HPAM)in case of high salt.The enhancement of salt resistance of polymers mainly comes from the change of molecular chain structure.Viscoelasticity is the most basic physical and chemical property of polymer.The change of molecular chain structure is bound to affect viscoelasticity.At the same time,the oil displacement effect of polymers with different structures and different salt resistance principles is also different,so there must be a direct or indirect relationship between them.In this paper,three hydrophobically associating polymers DH1,DH2 and dh3 and two high molecular weight polymers GF1 and GF2 were selected as the experimental objects to improve the salt resistance through two principles.The rheology and bulk viscoelasticity of the polymer were evaluated by rheometer,and the power-law characteristics of the polymer and the dynamic viscoelasticity of the whole solution were understood.In the reservoir,there is a interfacial film between polymer and crude oil.The shear viscoelasticity and dilatational viscoelasticity of the interfacial film are experimentally studied to characterize the strength and stability of the interfacial film,and to compare the viscoelastic difference of the interfacial film between different polymers.Finally,the conditions of heterogeneous reservoir with high salinity are set.The oil displacement ability of different polymers is compared by oil displacement experiment,and the relationship between viscoelasticity and oil displacement ability is established.At the same time,the profile control effect of polymers and oil displacement ability in different types of rock cores are studied.The experimental results show that both hydrophobically associating polymers and high molecular weight polymers belong to power-law fluids.The associating polymers have larger composite modulus,stronger bulk viscoelasticity and stronger ability to carry residual oil.For the properties of interfacial film,the interfacial shear viscoelasticity and interfacial dilational viscoelasticity of associative polymers are stronger than those of high polymers.Associative polymers have stronger and more stable oil film.The associated polymer has poor fluidity,poor injection capacity and transmission capacity,but its oil displacement capacity is outstanding.The polymer flooding recovery of DH1 polymer can reach 18.45%,which can play a certain profile control effect.Comparing the oil displacement effect of two types of polymers with similar seepage resistance and profile control effect,it can be basically concluded that the polymer with strong viscoelasticity has stronger oil displacement ability.At the same time,the recovery rate of DH1 polymer in Beret core is 12.85%,and the effect is considerable.Associating polymers and high score polymers have their own advantages and disadvantages in viscoelastic properties and oil displacement capacity.This paper establishes the relationship between the two properties,which provides a new idea for screening polymers for target reservoirs,and also provides a reference for experts and scholars to further develop new salt resistant polymers.