Mechanism of Cohesive Forces of Cyclopentane Hydrates with and without Thermodynamic Inhibitors

Abstract

Gas hydrates are commonly formed in oil and gas pipelines. One approach in their prevention is the injection of thermodynamic inhibitors (e.g., methanol, ethanol, monoethylene glycol (MEG)), so that the hydrate stability phase equilibrium can be moved into the fluid stable region. In this study, we directly measure cohesive forces of cyclopentane hydrates with thermodynamic inhibitors (2 wt % MEG, methanol, ethanol, and 1 and 3.5 wt % sodium chloride) to understand the effects of thermodynamic inhibitors (THIs) on the cohesive forces of hydrates. The cohesive forces are measured as a function of annealing time and temperature and determined from pull-off measurements based on the principle of Hooke’s law (F = Kspring × ΔD, where Kspring is the spring constant of the cantilever fiber, and ΔD is the displacement of the cantilever). A mechanism for the cohesive force of partially and fully converted hydrate particles is inferred and partially demonstrated by differential scanning calorimetry (DSC) measuremen...