Evaluation of Chromium-Crosslinked AMPS-HPAM Copolymer Gels: Effects of Key Parameters on Gelation Time and Strength

TL;DR

This study evaluates chromium-crosslinked AMPS-HPAM gels for controlling CO2 movement in reservoirs, showing they are durable and adaptable to harsh conditions.

Contribution

The paper provides new insights into the gelation behavior and stability of chromium-crosslinked AMPS-HPAM gels under CO2 exposure.

Findings

Gelation times can be controlled between 5 to 10 hours with minimal dehydration under CO2 exposure.

Gels remain structurally stable for over 10 months at 100 °C.

Key parameters like polymer concentration and pH significantly influence gelation behavior.

Abstract

Controlling CO2 channeling in heterogeneous reservoirs remains a major challenge for both enhanced oil recovery (EOR) and secure geological storage. AMPS-HPAM copolymers exhibit high-temperature resistance and brine tolerance compared with conventional HPAM gels, making them well suited for the harsh environments associated with CO2 injection. Chromium-based crosslinkers (CrAc and CrCl3) were investigated because sulfonic acid groups in AMPS can coordinate with trivalent chromium ions, enabling dual ionic crosslinking and the formation of a robust gel network. While organic crosslinked AMPS-HPAM gels have been widely studied, the behavior of chromium-crosslinked AMPS-containing systems, particularly their gelation kinetics under CO2 exposure, remains less explored. This experimental study evaluates the gelation behavior and stability of chromium-crosslinked AMPS-HPAM gels by examining the effects of the polymer concentration, molecular weight, polymer–crosslinker ratio, temperature, pH, salinity, and dissolved CO2. The results clarify the crosslinking behavior across a range of formulations and environmental conditions and establish criteria for designing robust gel systems. Gelation times can be controlled from 5 to 10 h, and the resulting gels maintained structural integrity under CO2 exposure with less than 3.6% dehydration. Long-term thermal testing has shown that the gel remains stable after 10 months at 100 °C, with evaluation still ongoing. These results demonstrate that chromium-crosslinked AMPS-HPAM gels provide both durability and tunability for diverse subsurface conditions.

Figures