Investigation for CO2 Adsorption and Wettability of Reservoir Rocks

CO2 adsorption under pressure and temperature conditions for geological storage of CO2 is evaluated for two non-shale reservoirs in Canada. One is the Weyburn carbonate reservoir, where the world's largest CO2 storage project is carrying on, and the other is a tight sandstone reservoir. Wettability of reservoir rock under high-pressure CO2 is also evaluated. Rocks from both reservoirs show a significant mass increase as a result of CO2 adsorption but distinctly different behaviors. A method for estimating the density of the adsorbed CO2 phase from gravimetric adsorption data is developed, and the result is in fair agreement with the expectation from analogy of adsorption with liquid condensation. A formula is proposed to predict CO2 storage capacity of reservoir rocks based on directly measured adsorption data. It is shown that CO2 adsorption could substantially increase the storage capacity and decrease leaking potential by decreasing overpressure to the reservoir caprock. Nearly 30 and 40% more CO(2 )could be stored by adsorption in the carbonate and tight sandstone rocks, respectively. Rock wettability reflected by the water contact angle suggests that CO2 could enter small rock pores to increase adsorption and utilization of reservoir capacity. The results can contribute to the evaluation of the impact of adsorption on CO2 storage.

Automated summary

This study evaluates CO2 adsorption under pressure and temperature conditions for geological storage in two non-shale reservoirs in Canada. The results show that CO2 adsorption can substantially increase storage capacity and decrease leaking potential by reducing overpressure in the reservoir caprock. The adsorption behaviors of rocks from different reservoirs are distinct, and CO2 can enter small rock pores to enhance adsorption and utilization of reservoir capacity.