Development of Novel Delayed Swelling Polymer Gel Particles with Salt Resistance for Enhanced In-Depth Permeability Control

Abstract

Prolonged waterflooding or polymer flooding in oil fields often exacerbates reservoir heterogeneity, leading to premature water breakthrough and high water cut, which significantly hinders efficient oilfield development. To address this issue, polymer gel particles have been prescribed to enhance sweep efficiency and augment waterflooding recovery by plugging preferential pathways within the reservoir. However, inherent weaknesses of polymer gel particles, such as fast water absorption and expansion rates in the initial stage and low post-expansion rates, make it difficult to balance in-depth transportation and plugging performance. Additionally, these gel particles are sensitive to ions in the formation water, resulting in reduced expansion rates under high-salinity conditions. Therefore, there are still challenges in the application of polymer gel particles for in-depth permeability control. In this study, a new type of delayed swelling and salt-resistant polymer gel particle was synthesized through inverse emulsion copolymerization. To achieve delayed swelling, we use a degradable crosslinker and hydrophobic monomer to enhance the crosslinked network density and hydrophobicity of gel particles. Our double crosslinked gel particles keep their original size until Day 2, then gradually swell up to 20 days in NaCl solution with a concentration of 15×104 mg·L−1 at 90°C. In comparison, the traditional single crosslinked gel particles show significant disparities in swelling behaviors and quickly swell when just dispersed in a 15×104 mg·L−1 NaCl solution at 90°C, maintaining roughly the same size over the testing period. Coreflooding experiments demonstrate that the residual resistance before and after aging increases from 2.37 to 6.82. The newly synthesized delayed swelling and salt-resistant polymer gel particles exhibit promising potential for overcoming the challenges associated with reservoir heterogeneity and high salinity.