CO Sequestration in Shale with Enhanced Gas Recovery

Shale is an important geological media for carbon capture utilization and storage. On one hand it can be regarded as impermeable caprock to prevent CO migration from reservoir, and on the other hand it can also treated as both natural gas and CO storage reservoir. CO-shale reactions within caprock can interfere with the integrity of the rock integrity and compromise the long-term carbon storage safety and stability; however this interaction can also improve the conductivity of the rock to enhance the shale gas recovery from the organic-rich shale. This chapter presents a review of the current state of knowledge regarding CO and shale interactions and their potential impacts on shale properties and groundwater quality in the context of CO enhanced shale gas recovery. The characterization of shale and CO which is critical to the understanding of various interactions between CO and shale is first summarized. The major interaction mechanisms between CO and shale including CO-shale-water geochemical reactions, CO adsorption induced clay swelling and organic matter extraction with supercritical CO and their impact on rock porosity and permeability, and mechanical properties, gas adsorption capacity and groundwater quality are surveyed. Finally, the open questions in this field are emphasized and new research needs are highlighted.