Thermodynamic Characteristic of Methane Sorption on Shales from Oil, Gas, and Condensate Windows

Abstract

High-pressure methane sorption isotherms at 40–101 °C and pressures up to 25 MPa were measured on Jurassic lacustrine and Silurian marine shales from China. Shale samples span a thermal maturity range from low mature (oil window) to overmature (dry gas window). Low-pressure CO2 and N2 adsorption techniques were used to quantify specific surface area, pore volume, and pore size distributions. The thermodynamic characteristic of methane sorption on shales was assessed based on the experimental multitemperature isotherms. The effects of physical and chemical properties of shales on thermodynamic properties were analyzed and discussed. Finally, standard enthalpy of sorption was first introduced to evaluate the sorption affinity of methane on shales, and a general pattern describing the evolution of methane sorption as a function of thermal maturity was proposed. The Langmuir sorption capacity of these shales varies from 0.09 to 0.16 mmol/g. The low total organic matter carbon, clay-rich lacustrine shales have...