CO₂ 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 CO₂ migration from reservoir, and on the other hand it can also treated as both natural gas and CO₂ storage reservoir. CO₂-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 CO₂ and shale interactions and their potential impacts on shale properties and groundwater quality in the context of CO₂ enhanced shale gas recovery. The characterization of shale and CO₂ which is critical to the understanding of various interactions between CO₂ and shale is first summarized. The major interaction mechanisms between CO₂ and shale including CO₂-shale-water geochemical reactions, CO₂ adsorption induced clay swelling and organic matter extraction with supercritical CO₂ 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.