Macro- and Microscale Interaction Properties between Surfactant Solution and Gas-Bearing Coal

Area of Science:

• Geochemistry
• Surface Science
• Materials Science

Background:

• Coal seam water injection is vital for dust suppression and gas control.
• High-gas coal seams exhibit poor wettability due to methane interference.
• Understanding coal wettability at macro and micro scales is crucial.

Purpose of the Study:

• To investigate the effect of dodecyl dimethyl betaine (BS-12) on coal wettability in high-gas conditions.
• To clarify the macroscopic and microscopic wetting mechanisms of BS-12 solutions on gas-bearing coal.
• To provide theoretical guidance for surfactant application in coal-bed methane (CBM) recovery.

Main Methods:

• Macroscopic contact angle measurements on gas-bearing coal with BS-12 solutions.
• Microscopic analysis of BS-12 molecule adsorption and methane displacement.
• Monte Carlo simulations of adsorption behavior and electrostatic potential differences.

Main Results:

• Decreased gas pressure and increased BS-12 concentration reduced contact angles.
• Higher BS-12 concentrations facilitated methane displacement from coal.
• BS-12 adsorption increased with concentration, enhancing wettability by altering electrostatic potentials.

Conclusions:

• BS-12 effectively enhances the wettability of gas-bearing coal.
• The mechanism involves displacing adsorbed methane and modifying surface electrostatic properties.
• Findings support the use of BS-12 as a surfactant for improved coal-bed methane recovery.