Evaluation of natural polymer for mobility control in carbon utilization and geo-storage applications

Abstract

Underground CO2 injection is susceptible to bypass, viscous fingering, and premature breakthrough which reduces the efficacy of CO2 storage. Hence, this work explores the usage of a natural polymer (Guar Gum) for promising control in mobility of injected CO2 in subsurface. Guar gum solutions of varying concentration (500–4000 ppm) were prepared in deionized (DI) water, and CO2 absorption (by pressure decay method) tests were performed at varying pressure (2–20 bar). CO2 absorption experiments were performed by pressurized CO2 in a stirring pot and kept the confined gas (pressure reduces as gas molecules get entrapped in the body of fluid) till equilibrium pressure (no further decrease in pressure) was reached. Rheological analysis confirmed that increasing polymer concentration yielded an increase in viscosity. This increase in viscosity showed two effects on CO2 absorption; (1): reduced CO2 absorption (in polymer solutions, compared to pure water) and (2): higher retention of entrapped CO2 inside the body of polymer solution. Maximum CO2 retention (≈9 h) was observed in 4000 ppm solution. Furthermore, pH and temperature tolerance tests indicate superior stability of guar gum solutions for pH >3 and temperature <75 °C. This study proposes the use of natural polymer as mobility control agents in geo-sequestration of CO2.