Effects of Modified Cellulose on Methane Hydrate Decomposition: Experiments and Molecular Dynamics Simulations

Hydrate dissociation inhibition is essential for maintaining wellbore stability during drilling in hydrate-bearing sediments. In this work, cellulose was modified and evaluated as a hydrate dissociation inhibitor. The structures of cellulose samples modified by aminosilane coupling agents with different chain lengths were determined and compared by Fourier transform infrared spectroscopy and thermogravimetric analysis. The hydrate dissociation inhibition property was evaluated by conducting hydrate dissociation tests in an inhibitor solution and pure water for comparison, and the average dissociation time was increased to 10 h from 6.8 h. To elucidate the inhibition mechanism of the modified cellulose, molecular dynamics simulations were performed. The mean square displacement curve indicated that the aminosilane chain was the adsorption group, and the diffusion coefficient of the modified cellulose was 32.3% smaller. During the stable adsorption stage, the number of intramolecular hydrogen bonds in cellulose decreased after modification, resulting in more potential sites that could adsorb to the hydrate surface. The biodegradability of the modified cellulose was better than that of poly(N-vinylcaprolactam) (PVCap), a commercial kinetic hydrate inhibitor. Therefore, the proposed method for modifying cellulose enhanced its adsorption capacity on the methane hydrate surface. These findings may facilitate the design of effective green hydrate dissociation inhibitors.

Automated summary

Hydrate dissociation inhibition is crucial for drilling in hydrate-bearing sediments, and modified cellulose as an inhibitor showed increased dissociation time and enhanced adsorption capacity on methane hydrate surfaces. Molecular dynamics simulations revealed that the aminosilane chain acted as the adsorption group, leading to a smaller diffusion coefficient of the modified cellulose.