Effect of surface morphology on methane interaction with calcite: a DFT study.

Area of Science:

• Geochemistry
• Materials Science
• Computational Chemistry

Background:

• Natural gas, primarily methane (CH4), is often trapped in complex and heterogeneous carbonate reservoirs.
• Estimating the ultimate recovery of natural gas from these reservoirs is challenging due to their intricate nature.

Purpose of the Study:

• To investigate the influence of calcite (CaCO3) surface morphology on methane adsorption.
• To identify specific calcite surface structures with high methane adsorption capacity for improved gas recovery estimations.

Main Methods:

• Utilized density functional theory (DFT) calculations to model methane adsorption on various calcite surfaces.
• Analyzed 9 different surface symmetries of CaCO3 to determine adsorption strength and capacity.
• Performed structural analysis and charge calculations to explain adsorption behavior.

Main Results:

• Methane adsorption capacity varies significantly across different calcite surface morphologies.
• The 110 surface of calcite demonstrated the strongest methane adsorption, exceeding the capacity of the 104 surface by over an order of magnitude.
• Adsorption behavior was correlated with specific structural and electronic properties of the calcite surfaces.

Conclusions:

• Calcite surface morphology plays a critical role in methane adsorption, impacting gas storage and recovery.
• The 110 calcite surface is identified as a key site for enhanced methane adsorption.
• These findings provide valuable insights for more accurate estimations of ultimate gas recovery in heterogeneous carbonate reservoirs.