Effect of micro‐aggregation behavior on the salt tolerance of polymer solutions

Abstract

Polymer solution for oil displacement is mostly used in the middle and late stage of water flooding reservoir development, and reservoir groundwater conditions are often one of the main conditions restricting polymer application. Therefore, it is necessary to develop salt tolerance of polymer solutions with different aggregation behaviors, so as to facilitate the synthesis and optimization of suitable polymer systems. The differences in the micro‐aggregation behavior of three polymers with different molecular structures were explored. On this basis, the effects of divalent metal cations on the properties of the polymer solutions were analyzed by assessing the micro‐aggregation behavior, apparent viscosity, hydrodynamic size, and shear rheological characteristics. The results showed that the linear partially hydrolyzed polyacrylamide (HPAM) was seriously affected by divalent cations, and the viscosity decreased obviously. The aggregation behavior of the polymer changed by hydrophobic association can enhance the salt tolerance of the solution. The hydrophobically modified partially hydrolyzed polyacrylamide (HMPAM) with “chain beam” aggregation behavior has strong intermolecular connection, which enables it to withstand the content of calcium and magnesium ions of 1100 mg l−1. When the content of calcium and magnesium ions exceeds 600 mg l−1, dendritic hydrophobically associating polymer (DHAP) will destroy the interaction between molecular chains, resulting in the decrease of apparent viscosity and hydrodynamic size. For polymer flooding in high‐salinity reservoir, salt tolerant polymer system can be constructed by optimizing molecular weight and hydrophobic group content.

Adsorption Characteristics of Polymer Solutions on Media Surfaces and Their Main Influencing Factors

“…DHAP has a relative molecular weight of 6 million and a hydrophobic group content of 0.6 mol %. The specific synthesis steps have been reported in previous literature [ 11 , 25 , 26 ], and its molecular formula is shown in Figure 3 .…”

“…Currently, the most widely used polymer solutions for oil displacement in oilfields are partially hydrolyzed polyacrylamide (HPAM) and the hydrophobically associating polymer AP-P4 [ 21 , 22 , 23 , 24 ]. The use of dendrimer hydrophobically associating polymers (DHAPs) is one of the leading research methods to improve complex reservoir conditions [ 25 , 26 ]. Among them, the adsorption mechanism and influencing factors of HPAM are more prominent.…”

The Effect of Shear on the Properties of an Associated Polymer Solution for Oil Displacement

“…Furthermore, 1000 mg/L and 2000 mg/L concentrations were selected to prepare the AP-P4 polymer solution. The polymer solution was prepared in the sampling section using a Waring stirrer to simulate different shear strengths of 5 s, 20 s, and 40 s and then was kept on standby after defoaming (First gear = Speed: 3500 rpm) [ 18 , 19 ]. An RS600 rheometer was used to test the rheology and viscoelasticity of the polymer solution after shearing and without shearing.…”

Application and Optimization of the Rheological Model for a Hydrophobically Associating Dendrimer Polymer

“…This paper obtains the rheology and viscoelasticity of dendritic polymer solution (DHAP) through indoor experiments [9,21]. Using the Carreau-Yasuda model, our goal is to apply the viscoelastic modulus experimental data, establish the characteristic relaxation time constraints of the polymer solution, conduct nonlinear regression of the polymer rheological curves of different concentrations, and establish the characteristic parameters with a regular gradient to ensure the accuracy of the fitting.…”

“…Polymers used for the experiment: partially hydrolysed polyacrylamide (HPAM) [22], with a relative molecular weight of 20,000 kg/mol, hydrolysis degree of 26.3%, and solid content of 88.9% (Refining and Chemical Company, Daqing, China), as shown in Figure 2; and dendrimer hydrophobically associating polymer (DHAP), with a relative molecular weight of 6000 kg/mol, hydrolysis degree of 25%, hydrophobic group content of 0.6 mol%, and branching degree of 1, the molecular formula of which is shown in Figure 3 (State Key Laboratory of Southwest Petroleum University independent synthesis) [21]. A polymer solution will encounter strong shear in the process of field application, resulting in its ultimate shear section.…”