Continual refined isothermal adsorption of pure illite in shale with gravimetric method

Conventional isothermal adsorption measurement (CM) and continual refined isothermal adsorption measurement (CRM) were used to investigate the methane adsorption of illite. The main differences between these two measurements are the repeated pressure during the buoyancy measurement and adsorption measurement in CRM. The results show that the adsorption isotherms of illite with CM and CRM were different, depending mainly on sample volumes calculated with various maximum buoyancy measurement pressures. The dynamic of sample volumes during the buoyancy measurement can be divided into 3 different stages. The rapid filling of helium at lower pressure stages results in an initial increase of the sample volume. With increasing test pressure, the shrinking interlayer space and decreased interparticle void volume in illite that can be compressed leading to the subsequent reduction in sample volume. Finally, when the test pressure exceeds to 5MPa, the sample volume presents stable. Combined with the volume of adsorbed phase CH4, the absolute volume that would be used to calculate the methane adsorption can be acquired. According to the mass balance equation, the modified and believable methane adsorption of illite was calculated.