Modeling High-Pressure Methane Adsorption on Shales with a Simplified Local Density Model

Area of Science:

• Geosciences
• Petroleum Engineering
• Physical Chemistry

Background:

• Shale gas is a vital alternative energy source, with much of its methane content adsorbed.
• Accurate prediction of gas in place and recovery requires understanding supercritical methane adsorption on shale.

Purpose of the Study:

• To experimentally investigate methane adsorption on Longmaxi shale.
• To validate a physical model for supercritical methane adsorption under reservoir conditions.

Main Methods:

• Methane adsorption experiments conducted on Longmaxi shale samples from the Sichuan Basin.
• Pressures up to 30 MPa and temperatures ranging from 40 to 100 °C.
• Fitting experimental and literature data using the simplified local density/Elliott-Suresh-Donohue model.

Main Results:

• The simplified local density/Elliott-Suresh-Donohue model accurately represents methane adsorption data (average absolute deviation < 10%).
• Methane adsorption capacity shows a positive linear correlation with total organic carbon content.
• Adsorption capacity decreases linearly with increasing temperature, with greater sensitivity in samples richer in organic matter.

Conclusions:

• The validated model provides a reliable tool for predicting methane adsorption in shale formations.
• Total organic carbon content and temperature are key factors influencing methane adsorption capacity in shale.
• Organic matter in shale is highly sensitive to temperature variations affecting gas storage.