Microscopic molecular insights into methane hydrate growth on the surfaces of clay minerals: Experiments and molecular dynamics simulations

Clay is widely present in hydrate reservoirs and drilling and completion fluids. A quantitative understanding of hydrate growth characteristics on clay solid phase surfaces is vital for predicting hydrate formation and preventing secondary hydrate generation in solid-phase-containing drilling fluid systems. The experiments and nonequilibrium molecular dynamics simulations are performed to investigate the characteristics of methane hydrate growth on the surfaces of kaolinite and montmorillonite. The experiments and dynamics simulated results demonstrate that a large number of bound waters is absorbed on the clay surface. However, the bound water does not participate in hydrate formation. The mechanisms by which clay minerals influence the formation of hydrates are different. Kaolinite reduces the induction time of hydrate formation, but the massive amount of bound water on the kaolinite surface reduces the total amount of free water molecules, which hinders the formation of hydrates, and the inhibition effect on hydrates is more significant than that with montmorillonite. Significantly, the hydrolysis of interlayer cations on the montmorillonite surface inhibits the formation of hydrates. This study will help us to understand the mechanism for gas hydrates formation on reservoir clay minerals, and to predict the amount of hydrate reservoir reserves, which will further aid hydrate resource drilling and exploration.