CO2-Brine Displacement in Geological CO2 Sequestration: Microfluidic Flow Model Study

Tuesday, 16 December 2014
Shuang Cindy Cao and Jongwon Jung, Louisiana State University, Baton Rouge, LA, United States
Geological CO2 sequestration is a promising method to reduce atmospheric CO2 and deep saline aquifers is one of the most important options due to their capacity for CO2 storage. Thus, a better understanding of two immiscible brine-CO2 mobility and its saturation, including invading patterns in deep saline aquifers as CO2 storage sites is required. Lenormand (1990) explored the invading patterns of two immiscible fluids in porous media with a transition region and three dominant regions: capillary fingering, viscous fingering, and stable displacement. These are determined by two main aspect ratios Nm and Nc through experimental studies using micromodel. Micromodel provides the opportunity to discover unrecognized processes, and test existing theories and assumptions in fluid flow through porous media. In this study, the micromodel was used to explore the effects of the scCO2 injecting velocity and ionic strength on invading patterns in geological CO2 sequestration. When scCO2 was injected into the micromodel that has already saturated with brine, the brine in the micromodel was displaced by injected scCO2. Continuous scCO2 injection into the micromodel leaded the scCO2 to pass through the micromodel. And the scCO2-brine displacement distribution in the micromodel remained constant during additional 100 PV scCO2 injection after injecting scCO2 passed through micromodel. When scCO2 passed through the porous media, the scCO2-brine displacement distribution represented the maximum displacement ratio. Results showed that scCO2-brine displacement ratios increased with: elevated pressures in the range of 3MPa~8MPa, decreased ionic strength from 5M to 1M NaCl, and increased scCO2 injecting velocity up to 40 μL/min. Also, Nm and Nc obtained in this study are located in transition region of the invading patterns suggested by Lenormand (1990).