Adsorption Equilibrium of CO₂ and CH₄ and Their Mixture on Sichuan Basin Shale

Abstract

Adsorption equilibrium isotherms of CO2, CH4, and mixtures of CO2/CH4 on shale sampled from Nanchuan, southeastern Sichuan Basin, were measured at 278, 298, and 318 K by an accurate gravimetric method. The adsorption equilibrium data of CO2 and CH4 were fitted using both the virial model and the Brunauer–Emmett–Teller (BET) model, and the isotherms of CO2/CH4 mixtures were fitted by an extended BET model. On the basis of adsorption data, the adsorption selectivity factors for CO2 over CH4 (αCO2/CH4 ) and thermodynamic parameters were estimated. Nanchuan shale was characterized with a high total organic carbon (TOC), having inorganic minerals and wide pore size distribution ranges. The adsorption heat, negative Gibbs free energy change, and negative surface potential of CO2 are larger than those of CH4, and the entropy loss of CO2 is larger than that of CH4, suggesting that adsorbed CO2 is in a more highly ordered arrangement than CH4 on shale. αCO2/CH4 values at different temperatures are all larger than 2.5.

Using Capillary Condensation and Evaporation Isotherms to Investigate Confined Fluid Phase Behavior in Shales

“…[3] The primary reason for this is misinterpretation of isotherms measured in shale. Throughout the literature, isotherms measured for both hydrocarbons and gases, such as CO2, do not exhibit the distinct capillary condensation step defined in the IUPAC Type IV isotherm [4] or the continuous filling step that has recently been elucidated by Tan et al [5] and Barsotti et al [6] Instead, they appear similar to IUPAC Type I and II isotherms, [7], [8] which are attributed to mono-layer and multi-layer adsorption, respectively. [4] Therefore, they are given the same interpretation even though the IUPAC isotherms rely on fundamental assumptions about the adsorbate and adsorbent that are not true of shale rock.…”

Study on the Adsorption, Diffusion and Permeation Selectivity of Shale Gas in Organics

“…Gas injection is considered an effective way to enhance oil and gas recovery and it has been widely used worldwide [12,13]. According to the adsorption capacity difference between CO 2 and CH 4 on shale [14][15][16], using CO 2 displacement to enhance the shale gas recovery has become one of the most promoted ways [17][18][19]. As the insoluble organics in shale, MD method to choose carbon nanotubes in place of the shale organics.…”

Structure and Dynamics of Confined C-O-H Fluids Relevant to the Subsurface: Application of Magnetic Resonance, Neutron Scattering, and Molecular Dynamics Simulations

“…Contributions on the behavior of confined fluids include adsorption equilibrium of CO 2 and CH 4 into different confined systems, such as shale. Duan et al (2016) studied the adsorption equilibrium isotherm data of CO 2 and CH 4 at 278, 298, and 318 K on rock samples from southeastern Sichuan Basin of China with a total organic carbon (TOC) of 2.58 wt%, inorganic components of quartz and orthoclase, and a wide pore size distribution. They demonstrated that the adsorption capacity of CO 2 is higher than that of CH 4 on shale.…”