Molecular dynamics study of methane hydrate formation at a water/methane interface

Area of Science:

• Thermodynamics and physical chemistry of interfaces.
• Computational materials science.
• Chemical engineering and process safety.

Background:

• Methane hydrate formation poses significant challenges in oil and gas operations.
• Low Dosage Hydrate Inhibitors (LDHIs) are crucial for mitigating these risks.
• Poly(methylaminoethylmethacrylate) (PMAEMA) is an active component in commercial LDHIs.

Purpose of the Study:

• To investigate the effect of PMAEMA on methane hydrate nucleation and growth at the water-liquid interface using molecular dynamics simulations.
• To understand the role of temperature and inhibitor presence on hydrate formation kinetics and hydrogen bonding.
• To elucidate the mechanism by which PMAEMA influences hydrate inhibition.

Main Methods:

• Constant NPT ensemble molecular dynamics simulations were conducted for liquid water/methane interfaces.
• Simulations were performed at various temperatures (220-250 K) and a pressure of 300 bar, with and without PMAEMA oligomers.
• Analysis included calculation of hydrate content, hydrogen bond propensity, and induction times for hydrate growth.

Main Results:

• Methane hydrate growth was observed below 245 K in pure water/methane systems, with immediate growth at lower temperatures.
• Increasing temperature decreased both hydrogen bond numbers and hydrate content.
• The presence of PMAEMA lowered the temperature threshold for sustained methane hydrate growth.

Conclusions:

• PMAEMA effectively inhibits methane hydrate formation by altering the nucleation and growth kinetics.
• The study provides molecular-level insights into the mechanism of LDHI action at the interface.
• Findings support the use of PMAEMA-based LDHIs for preventing hydrate plugging in subsea pipelines.