Competitive adsorption phenomenon in shale gas displacement processes

Area of Science:

• Earth Sciences
• Chemical Engineering
• Materials Science

Background:

• Shale gas exploitation and carbon dioxide sequestration are critical global challenges.
• Simultaneous displacement of methane (CH4) by injection gas offers a dual solution.
• Understanding competitive adsorption in shale is key to optimizing this process.

Purpose of the Study:

• To develop a simplified shale composition model for studying gas injection displacement.
• To investigate the mechanisms of methane displacement and competitive adsorption.
• To determine optimal operating conditions for enhanced shale gas recovery and CO2 sequestration.

Main Methods:

• Developed a simplified shale model incorporating organic matter and brittle silica.
• Employed grand canonical Monte Carlo (GCMC) simulations for displacement analysis.
• Utilized molecular dynamics (MD) for studying competitive adsorption behaviors.

Main Results:

• Carbon dioxide exhibits higher methane displacement efficiency due to strong shale interaction.
• Optimal pore width for CO2 and N2 displacing methane was found to be 30 Å.
• Displacement efficiency exceeded 50% for all tested gases at injection pressures above 30 MPa.

Conclusions:

• The study elucidates the competitive adsorption mechanisms between shale gas and injection gases.
• Findings provide valuable insights for optimizing shale gas exploitation via gas injection.
• This research offers guidance for effective carbon dioxide sequestration in shale formations.