High-strength amphoteric hydrogel that can realize self-repairing of cement microcracks triggered by CO2 gas

Abstract

During the completion of a natural gas well, the annular gas migration of the cement paste significantly damages the cement quality. Thus, the cement with self-repairing property has great significance in oil well applications. In this work, chemically cross-linked hydrogels were synthesized by the solution polymerization of acrylamide, acrylic acid, and 2-(dimethylamino)ethyl methacrylate (DMAEMA) with NMBA as cross linker to plug the CO2-triggered microcracks in the cement paste. The mechanical strength of the hydrogel (Cu-PMAD) was significantly enhanced by complexation between Cu2+ and the carboxyl group of the hydrogel network. As a self-healing plugging material, Cu-PMAD hydrogel powder was mixed with cement to prepare self-repairing cement slurry. The amphoteric structure of hydrogel was triggered by CO2 due to the DMAEMA unit of the hydrogel was protonated, and the hydrogel can swell further by the anti-polyelectrolyte effect under CO2 of nature gas and formation salt-bearing fluid. The good swelling ability and mechanical properties endowed the Cu-PMAD hydrogel with excellent plugging ability for cement microcracks triggered by CO2.