Volume 57

A composite gel system with CO2 and temperature-responsive for restraining CO2 channeling Chuanhong Kang, Jixiang Guo, Congcong Xu

Abstract

Carbon capture, utilization and storage (CCUS) technology is currently the most promising method for achieving low-carbon development and carbon reduction. The carbon storage and utilization part involves the injection of CO2 into the underground. However, due to the low density and low viscosity of CO2, gas migration often occurs during the migration of CO2 in the formation, so suitable sealing agents are needed to repair the leakage of CO2. A composite gel system for inhibiting CO2 leakage was developed using the one-pot method. In this system, diethylenetriamine acts as the CO2-responsive molecule, forming CO2-responsive worm-like micelles with long-chain anionic surfactants. Acrylamide and a high-temperature crosslinking agent form temperature-responsive underground crosslinked gels. The response mechanism of the CO2-responsive worm-like micelles to CO2 is that the DETA molecules in the system come into contact with CO2 and undergo protonation. The protonated DETA then attracts the anionic surfactant head groups through electrostatic interactions, forming a “pseudo-dipole” surfactant, and subsequently self-assembles to form worm-like micelles. When in contact with CO2, the viscosity of these micelles will increase sharply, thus solving the problem of CO2 channeling. The composite gel undergoes a cross-linking reaction at temperatures above 125℃, forming a non-flowing gel. This gel has excellent temperature resistance and mainly seals the weakly acidic fluid resulting from the dissolution of CO2 in water. The research results show that during the alternating introduction of CO2/N2, the CO2-responsive worm-like micelles can switch between low and high viscosities, and the CO2 gas sealing rate can reach 99.61%. The composite gel can remain stable for 360 days at 140℃, and the water injection sealing rate can reach 98.92%. This dual-response composite gel system based on CO2 and temperature provides technical support for CO2 sequestration and utilization, and has broad application prospects for restraining CO2 channeling.

Keywords CO2 and temperature response, composite gel system, temperature-resistant gel, CO2 channeling, enhanced oil recovery