The Influence Of Molecular Structure On The Rheological Properties Of Hydrophobically Associating Polymer And Oil Displacement Efficiency

Since the oil displacement efficiency could be enhanced by the improvement of viscoelasticity of polymer solution, the aim of this paper is to study the viscoelasticity of Hydrophobic Associating Polymer (HAP) in porous medium and the relationship between it and displacement efficiency under actual reservoir. The viscoelasticity and rheological properties of HAP solution in rheometer and porous medium were investigated mainly by experiment means, and the microscopic mechanism of the viscoelasticity of HAP solution on displacement efficiency was discussed. Three main parts of the research contents were shown as follows.1. Viscoelastic properties of polymer solutionViscosity and viscoelastic properties of polymer solution were measured with rheometer and the influence factors were analyzed. It was found that the apparent viscosity of polymer was comprised by structural viscosity and non-structural viscosity.Three kinds of associating polymers with different hydrophobic contents were synthesized and the hydrophobic contents indicated HNT279A>HNT276A>X61A. Shear steady research showed that the first normal-stress difference N1increased with the increasing of shear rate and the higher hydrophobic group content, the bigger N1. At the same time, apparent viscosity increased with the increase of polymer concentration and hydrophobic group content. Under the same apparent viscosity, the HNT279A with higher hydrophobic group content had higher viscosity and first normal-stress difference N1.The expansion of multiples B and Weissenberg Number were tested to evaluate the viscosity and elasticity of three kinds of polymer.The recovery after deformation was proposed to characterize the elastic property of polymer solution. It was found that polymer with higher hydrophobic group content had stronger recovery after deformation in three kinds of polymers with the same shear viscosity.2. The rheology behavior and viscoelasticity of polymer solution in porous mediumThe viscosity changes of polymer solution before and after passing through core were determined by core seepage experiments which indicated that shear action was helpful to the improvement of intermolecular association and the viscosity. The polymer solution was manifested to show the property of shear thinning at low flow rate and shear thickening if the flow rate exceeded a point. The effective viscosity and elastic viscosity increased as the shear rate increased.3. Oil displacement effect of polymer floodingIndoor core flooding results showed that the first normal-stress differenceN1, the recovery after deformation, the expansion of multiples, the effective viscosity were all revealed to be a positive relationship with the oil displacement efficiency. The elasticity of polymer solution had a great effect on oil displacement efficiency: the stronger elasticity, the higher oil displacement efficiency. In summary, the phenomena of polymer flooding in seepage and oil displacement efficiency experiments were perfectly explained by the elastic properties of polymer solution. Also the elastic property could provide basis for the design, synthesis and screening of chemical flooding agents and contribute to the designing optimization, the development of chemical flooding and micro-seepage.