Molecular Dynamics Simulation Study of Polyvinylpyrrolidone as a Kinetic Inhibitor for Natural Gas Hydrates under Ultradeepwater Conditions.

The rapid advancement of ultradeepwater oil and gas exploration has led to the secondary formation of natural gas hydrates under low temperatures and high pressures typical of these environments. Inhibiting secondary hydrate formation is essential for ensuring the safety and efficiency of ultradeepwater drilling operations. This study extends prior molecular dynamics work by elucidating the inhibition mechanism of polyvinylpyrrolidone during the nucleation and formation of natural gas hydrates through molecular dynamics simulations, providing new insights into molecular-level interactions under ultradeepwater conditions. The simulations analyzed the dynamic trajectories of hydrate nucleation, formation, and structural and dynamic properties, including the radial distribution function, coordination number, mean square displacement, diffusion coefficients, hydrogen bonding interactions, interaction energies, and axial concentration distributions. The results indicate that polyvinylpyrrolidone increases methane molecule aggregation, decreases methane solubility in water, and restricts water molecule movement, reducing the likelihood of hydrate nucleation. Additionally, polyvinylpyrrolidone molecules adsorb onto the hydrate crystal surface, altering the distribution of water molecules and inhibiting secondary hydrate formation. This study reveals the microscopic mechanism by which polyvinylpyrrolidone inhibits natural gas hydrate formation under ultradeepwater conditions, providing theoretical support for developing efficient kinetic inhibitors and offering valuable insights for ultradeepwater oil and gas operations.