CO2 STORAGE AND ADSORPTION KINETICS IN SHALES

The main objective of this project is to determine the behavior of intact and fractured caprocks when exposed to supercritical CO2 at elevated pressures, including the characterization of the physical, chemical and geomechanical processes associated with fluid flow and storage in these systems. Hereby, an envisioned experimental setup allows high pressure, super-critical CO2 adsorption and desorption isotherm measurements on powdered rock samples is designed.

The experimental setup is a manometric setup, which can be used to study both the equilibrium and kinetics of adsorption. The study of equilibrium of adsorption gives insight on the storage capacity of these systems, and the study of the kinetics of adsorption is essential in understanding the resistance to fluid flow. The first part of this paper discusses the study of both equilibrium and kinetics of the CO2 adsorption on dry shale experiment.

The second part of this report discusses CO2 sorption experiment performed on water immersed organic rich shale and illite clay samples. The purpose of this study is to determine the possibility of supercritical sorption in water-immersed shales and to understand the mechanism of sorption in such cases. It is observed that organic matter (OM) plays a critical role in facilitating sorption in water immersed shales, while the water immersed illite samples do not sorb supercritical CO2. On the basis of our finding we concluded that water does not fill the potentially hydrophobic OM pores of shales and they serve as facilitators to CO2 sorption. The mechanism of sorption in such cases includes dissolution of CO2 in water and its diffusive transportation in liquid water to the OM pores. After reaching the OM pores, CO2 molecules get subsequently released from the solution and later become sorbed in the OM pores. The findings of this study bear significant implication on the nature of sorption in a more realistic and natural state of shale reservoirs because water is often present in the subsurface porous formations. Therefore, the study will help in understanding the fluid storage potential in shale pores for hydrocarbon production and CO2 sequestration applications.