驱油用聚合物溶液的流变模型应用优化研究

Application and optimization of rheological model of polymer solution for oil displacement

流变测试手段的进步推进了研究人员在较广的测试区间内对黏弹性流体的认识。驱油用聚合物溶液呈现“三段式”的流变曲线特征(零剪切段、剪切变稀、极限剪切段),极其需要一个更为准确的描述模型和限定条件。以部分水解聚丙烯酰胺和疏水缔合聚合物为研究对象,通过分析较广范围(0.01~10000 s^(-1))的流变曲线,结合黏弹性模量变化进行研究。结果表明:在实验条件下,两种聚合物的流变曲线可以用Carreau流变模型进行描述;疏水缔合作用形成的结构黏度,大幅度增强了溶液的弹性作用,使聚合物溶液AP-P4的弹性模量占据主导。考虑弹性特征对流变曲线的影响,应用小幅振荡实验数据推导的松弛时间谱,限制特征松弛时间(λ)的取值范围,最后通过Carreau流变模型的非线性回归拟合曲线高度匹配了实验数据。研究黏弹性溶液流变本构方程时,需充分考虑溶液特性,搭建不同测试参数间的相互关系,建立合理的限制条件,是优化和改进黏弹性流体流变本构方程的有效手段。

The progress of rheological testing methods has promoted the researchers’ understanding of viscoelastic fluids in a wider testing range. The polymer solution used for oil displacement has the characteristics of“Three-stage”rheological curve(zero shear section, shear thinning section, and ultimate shear section), so a more accurate description model and limiting conditions are extremely needed. Taking partially hydrolyzed polyacrylamide and hydrophobically associating polymer as the research objects, the rheological curves in a wide range(0.01 ~ 10 000 s)have been analyzed, and the changes of viscoelastic modulus have been studied. The results show that under the experimental conditions, the rheological curves of the two polymers can be described by Carreau rheological model. The structural viscosity formed by hydrophobic association greatly enhances the elasticity of the solution, and makes the elastic modulus of the polymer P-P4 dominant. Considering the influence of elastic characteristics on the rheological curve, the relaxation time spectrum derived from the experimental data of small amplitude oscillation is used to limit the characteristic relaxation time(λ). Finally, the experimental data are highly matched by the nonlinear regression fitting curve of Carreau rheological model. When studying the rheological constitutive equation of viscoelastic solution, it is necessary to fully consider the solution characteristics, establish the relationship between different test parameters, and establish reasonable limiting conditions, which are effective means to optimize and improve the rheological constitutive equation of viscoelastic fluid.