Comparison of Temperature-Dependent Gas Adsorption Models and Their Application to Shale Gas Reservoirs

Significant quantities of gas are adsorbed onto the rock matrix in shale gas reservoirs. Accounting for this adsorbed gas in reservoir calculations is key for realistic estimations of gas in place and overall gas production, and later as a target for enhanced gas recovery methods like thermal stimulation. The classical Langmuir isotherm fails to represent gas adsorption at multiple temperatures, thereby making its application in thermal stimulation strategies limited. In this work, several temperature-dependent gas adsorption models were reviewed and grouped further into both temperature-dependent and -independent Langmuir volume. Application of the models to several shale gas data sets obtained from different regions shows minimal differences in the successful prediction of gas adsorption using either the temperature-dependent or -independent Langmuir volume models. However, caution is to be exercised in the choice of models for use in numerical simulation studies when extrapolating to temperatures that might be outside laboratory conditions and for which no data exist. For such cases, use of the models might result in an under- or over-estimation of the volume of adsorbed gas.