APPLICATION OF SUPERCRITICAL GAS ADSORPTION THEORIES IN ASSESSMENT OF ADSORBED GAS IN SHALES UNDER GEOLOGICAL CONDITIONS
Three independent data sets were utilized for nitrogen and methane adsorption isotherms at different temperatures. We demonstrate that adsorption predicted by the SDR model is comparable or lower than that predicted by the SBET model, but higher than the amounts predicted by Langmuir and OK models. The nitrogen BET method tends to underestimate the accessible SSA for methane. Measurement of isosteric heat of adsorption is suggested instead of the experimental fitting method, due to the significant difference between the calculated results by two commonly used methods. Experimental fitting and simulation methods are also briefly reviewed to guide future research on shale gas adsorption.
This work improves prediction of subsurface natural gas adsorption under supercritical conditions and assessment of shale gas-in-place for decision of production strategy in petroleum industry.