(85e) Enhanced CO2 Interactions with Shale for Sustainable Extraction of Tight Oil and Gas

According to the International Energy Agency (IEA), fossil fuels continue to supply more than 80% of the world's energy, with natural gas and tight oil extraction as the fastest growing fossil fuel resources. Therefore, there is considerable interest in investigating subsurface gas-liquid-solid interactions, particularly for more efficient and sustainable recovery of oil and gas from shale reserves. One of the current technologies to extract oil and gas is hydraulic fracturing which involves injecting water, chemicals, and proppants at high pressure to form new fractures and to keep them open which involves the use of large quantities of water. Hydrofracking is often accompanied by the mobilization of heavy and radioactive metals such as arsenic, radon, and radium, which is environmentally hazardous. Therefore, the aim of this study is to use CO₂ as an alternative processing fluid. However, considerable uncertainties exist around the reaction rates of shale with CO₂. Shale comprises carbonates, clays, and quartz at varying compositions. The interactions of CO₂ with shales containing variable compositions of carbonates, clays, and quartz are expected to result in significant differences in the rates of dissolution and carbonation, and changes in the pore spaces, depending on the pH, temperature, and partial pressure of CO₂, which have not yet been well characterized in existing literature. Therefore, the aim of this study is determine the effect of variable pH (1-12), temperature (T_max = 90 ^oC), and partial pressure of CO₂ (P_{CO2, max} = 150 atm) on in-situ chemical and morphological changes on clay-rich and carbonate-rich shales, and determine the corresponding reaction mechanisms that result in the alteration of the pore spaces of clay-rich and carbonate-rich shales.