Molecular Configuration and Flow Performance of Al3+ Cross-linked Polymer

Abstract

According to the difference in compositions of Al3+ cross-linked polyacrylamide gel, there are two types of cross-linked reactions. One is the intramolecular cross-linked reaction that takes place in different chains of the same polymer molecule, and the other is the intermolecular cross-linked reaction, which takes place among different polymer molecules. Through changing the compositions of the cross-linked polymer and gelling environment, thorough research on the critical conditions and flow performance of intramolecular cross-linked polymer is carried out. The results show that the viscosity of the intramolecular cross-linked polymer almost remains the same over time, but during the flow performance experiments, the resistance factor and residual resistance factor are higher, and the residual resistance factor is larger than the resistance factor. The higher the salinity of solvent, the easier the intramolecular cross-linked polymer forms. In the scope of concentration of cross-linking agent, the higher the concentration of cross-linking agent, the easier the intramolecular cross-linked polymer forms. The higher the temperature, the easier the intramolecular cross-linked polymer forms. For the minerals that influence the molecular configuration of cross-linked polymer, the influence of Ca2+ is the biggest, then Mg2+, the least being Na+. A pilot test in the Pu I1-4 reservoir of the Daqing oilfield showed that the in-depth profile modification using intermolecular cross-linked polymer solution has characteristics of lower cost and easier injection technique, and can gradually form gel through the process of injection. When the effect of gel forming is at its best state, the injection pressure can reach the highest and retain relatively stable values. Therefore, comprehensive watercut would decrease and oil production rate would increase, which can be used as an important whole profile modification technique.