Methane adsorption on shale under high temperature and high pressure of reservoir condition: Experiments and supercritical adsorption modeling

To understand methane adsorption characteristics on shale at high pressures, we conducted experiments of methane adsorption on dry shale up to 50MPa and at 95.6 degrees C, 75.6 degrees C, and 40.6 degrees C. Results show that the amount of excess adsorption on shale at high pressures is not the same as that at low pressures. The amount of adsorption increases with pressure until a peak value is reached and then declines with further pressure increases. Isosteric heat of adsorption is studied to explain the excess adsorption behavior. In addition, a new supercritical adsorption model was developed based on supercritical adsorption. This new model and Langmuir model were both used to fit the adsorption isotherms data. Langmuir model matched well with experiment data only at low pressures but failed at high pressures. The new model can fit the adsorption isotherms well, indicating that it reflects the characteristics of supercritical methane adsorption on shale at high pressure and temperature.