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Gas hydrate formation is considered one of the major challenges in the flow assurance of deepwater oil and gas pipelines, as their blockage by hydrate can lead to significant production/economic loss and safety risk. Understanding the hydrate formation and deposition processes can improve the management methods in field development and production. This study used a high-pressure rocking cell to simulate multiphase flow conditions to visually investigate the hydrate formation and deposition from an oil-gas-water system. The changing hydrate morphologies, flow pattern and particle distribution during hydrate formation were studied and a conceptual model was proposed. The relative motion of hydrates to the cell wall and the final morphology of the hydrate chunks are found to be two critical parameters for evaluating hydrate deposition characteristics in the flow system. Five types of hydrate deposition morphologies are observed and these are correlated to the hydrate porosity. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4136–4146, 2017

The CH4 Raman ν1 symmetric stretching band position was measured at various temperatures and pressures over the range 1–600 bars and 0.3–22 °C. The ν1 symmetric stretching band shifts to lower wavenumbers with increasing pressure and/or decreasing temperature, and shows a systematic correlation with density over this same range. Ab initio calculations (MP2/aug-cc-pVTZ) show that the changes in peak shape and position reflect fundamental distortion of the methane structure as the density increases. Copyright © 2007 John Wiley & Sons, Ltd.

Molecular simulations were performed for phospholipid bilayers as model cell membranes to understand their dynamic and structural properties, in particular how those are affected in the presence of the cell-preservation agents trehalose and DMSO. Simulations covered a large range of temperatures and concentrations of trehalose and DMSO. A number of properties were examined, including the area per head group, lipid-tail order parameter, density profile, conformation, and binding of trehalose. Our results indicate that trehalose specifically interacts with the phospholipid bilayer by binding to the polar head groups (H-bonds). This binding serves as a bridge between the lipids and prevents their aggregation. The hydrophilic nature of trehalose also makes it a water substitute when binding to the phospholipids. At high trehalose concentrations, trehalose forms a glassy matrix and preserves the bilayer structure by 'freezing' it in its natured state, as the core of the bilayer is found to remain fluid. Simulations with DMSO revealed that DMSO can penetrate and freely diffuse through the bilayer, which is attributed to its unique characteristic of interacting favorably with both hydrophilic and hydrophobic domains.