Stability analysis of CO2 microbubble for CO2 sequestration and mobility control in enhanced oil recovery

Abstract

This study addresses the challenge of CO2 microbubble stability in enhanced oil recovery (EOR), with a focus on the combined effects of surfactant concentration, brine concentration, brine-oil ratio, and gas flow rate. Microbubble destabilization, driven by phase separation and improper brine-oil ratios, is a critical issue in EOR. The novelty of this research lies in the use of Acacia concinna, a natural, non-ionic surfactant, to enhance microbubble stability sustainably. The study systematically investigates foamability, drainage kinetics, surface tension, rheology, and bubble size distribution to assess microbubble stability. The results showed that increasing surfactant concentration and brine-oil ratio significantly impacted foam stability and bubble size distribution, with optimal stability conditions observed at 2 wt% surfactant concentration (53.6 min), 5000 ppm brine concentration (47.6 min), a brine-oil ratio of 1:2 (52.4 min), and a CO2 gas flow rate of 1 lpm. Key findings also indicate that increasing NaCl concentration from 5000 to 20,000 ppm caused an increase in microbubble diameter, while higher gas flow rates reduced bubble size. The work introduces new empirical correlations for predicting bubble size distribution based on column diameter, surfactant and brine concentrations, viscosity, density, and gas superficial velocity. These correlations provide a more accurate means of optimizing EOR processes, improving oil recovery efficiency while enhancing CO2 sequestration, contributing to both energy production and environmental sustainability.