Shale gas reservoir is a potential sequestration space of excess CO₂ in the atmosphere. This work clarified CO₂ adsorption behavior in Longmaxi shale, and Langmuir, BET (Brunauer-Emmett-Teller), DA (Dubinin-Astakhov), and DR (Dubinin-Radushkevitvh) models presented highly applicable on the fitting process of CO₂ adsorption experimental data. Micropore filling theory was the best model for CO₂ adsorption in the shale samples with the highest average R² (goodness of fit) value, higher than that of monolayer adsorption and multi-layer adsorption theories, which was controlled by the widely developed micropores. Specifically, micropore filling adsorption mainly occurred in micropores, including the closed end of slit pores, capillary pores, and ink-shaped pores. Molecular layer adsorption mainly occurred in mesopores and macropores, including the open end of slit pores, plate pores, capillary pores, and ink-shaped pores. Slit pores are mostly intergranular pores, plate pores are mostly interlayer pores (intragranular pores) of clay minerals and microfractures, capillary pores are mostly intergranular pores, and ink-shaped pores are mostly organic matter pores. Besides, the prediction model of CO₂ storage quantity in deep shale gas reservoirs of China was established, calculated that 91.5 - 388.89 × 10¹² m³ of CO₂ could be sealed in adsorbed state in theory, and CO₂ was mostly sealed by adsorbed state (higher than 95%) and free state with a good security and low leakage risk.

 

CO2 adsorption,Isothermal adsorption model,CO2 sequestration,Longmaxi shale