Influence of water dilution on performance of chromium polymer weak gel in porous medium

Abstract

In order to explore the influence of water dilution on performance of Cr³⁺ polymer weak gel in porous medium, the performances of pure polymer solution and Cr³⁺ polymer weak gel were studied according to the laboratory testing of viscosity, micro-structure performances (polymer molecule aggregate dimension, polymer molecule aggregate configuration and Zeta potential), seepage characteristics and oil displacement effect under the condition of water dilution. The results indicated that, after diluting by water, pure polymer solution and Cr³⁺ polymer weak gel had an almost same viscosity, but there were obvious differences in micro-structure performance and seepage characteristics. Different with pure polymer solution, with the decrease of polymer concentration, on the one hand, the influence of free Cr³⁺ on electric double layer and shielding effect on electrostatic exclusion got weaker, on the other hand, water molecules were attracted by hydrophilic groups on the Cr³⁺ polymer weak gel molecular chains and then entered into the three-dimensional spatial structure of Cr³⁺ polymer weak gel, producing hydration and expansion. Therefore, the polymer molecule aggregate dimension of Cr³⁺ polymer weak gel presented a trend of continuous increasing. This characteristic was good for keeping the injection pressure at a higher value during diluting in the porous medium, which could be used to improve oil recovery in offshore oilfield through conducting injection of water-alternating- Cr³⁺ polymer weak gel.

Graphical Abstract

Keywords:

• Cr3+ polymer weak gel
• water dilution
• porous medium
• micro-structure performance
• experiment researches

Disclosure statement

The authors declare no competing financial interest.

Additional information

Funding

This work was supported by the SPE Nico van Wingen Memorial Fellowship, Natural Science Foundation of China (No.51574086), Natural Science Foundation of China (No. 51834005), National science and technology major projects (2016 ZX05058-003-010), Northeast Petroleum University Innovation Foundation For Postgraduate (No. YJSCX2017-007NEPU), and Postdoctoral Innovative Talents Support Program of China (BX20190065).