ROLE OF SUBSURFACE PRESSURE AND TEMPERATURE ON CO2 SEQUESTRATION

Abstract

Concentration of carbon dioxide (CO2) is increasing continuously in the atmosphere due to various anthropogenic activities particularly the burning of fossil fuels such as coal, gas, oil, and deforestation. This causes the greenhouse effect responsible for raising atmospheric temperature resulting in sea level rising, oceanic acidification, increased frequency and intensity of wildfires, smog pollution, floods, droughts, cyclones, tsunami etc. CO2 capturing from point sources and its storage in subsurface geology is a getting wide attention for mitigating high concentration of CO2 in atmosphere. The injected CO2 in deep subsurface undergoes to different evolution patterns under site specific conditions. Amongst various geological conditions, pressure and temperature play crucial role in storage of CO2 in subsurface. Therefore, the main focus of this study is to investigate the role of subsurface pressure and temperature on CO2 sequestrated in saline aquifers using a series of numerical experiments with the help of COMSOL5.2 subsurface modules. Steady state injection of CO2 as a supercritical fluid is simulated using Darcy’s law coupled with mass conservation equation for two phase immiscible flow considering one fluid as a saline water and another fluid as a liquid CO2. To solve the governing equations, finite volume approach is used for discretizing a two dimensional hypothesised homogeneous and isotropic subsurface zone having 2.4 m width and 1.4 m depth. Simulations were performed for a period of 20 years. The results show that storage capacity of CO2 in subsurface increases when a high subsurface pressure is considered while it decreases under high temperature conditions. The sensitivity analysis shows that geological pressure conditions are more sensitive as compared to the temperature conditions. This study may help in predicting CO2 storage and its stability in subsurface particularly in saline aquifers and can also be used in enhancing oil and gas recovery for petroleum reservoirs.