The stability of a natural gas hydrate during storage at atmospheric pressure and below-freezing temperatures was studied in the laboratory. The gas hydrate was produced in a stirred vessel at 2-to 6-MPa pressure and temperatures from 0 to 20°C. The hydrate was refrigerated and stored in deep freezers at -5, -10, and -18°C for up to 10 days. The natural gas hydrate remained stable when kept frozen at atmospheric pressure.

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In the Prausnitz tradition, molecular and macroscopic evidence of hydrate formation and kinetic inhibition is presented. On the microscopic level, the first Raman spectra are presented for the formation of both uninhibited and inhibited methane hydrates with time. This method has the potential to provide a microscopic-based kinetics model. Three macroscopic aspects of natural gas hydrate kinetic inhibition are also reported:  (1) The effect of hydrate dissociation residual structures was measured, which has application in decreasing the time required for subsequent formation. (2) The performance of a kinetic inhibitor (poly(N-vinylcaprolactam) or PVCap) was measured and correlated as a function of PVCap molecular weight and concentrations of PVCap, methanol, and salt in the aqueous phase. (3) Long-duration test results indicated that the use of PVCap can prevent pipeline blockage for a time exceeding the aqueous phase residence time in some gas pipelines.

Methane gas storage properties of structure H (sH) hydrate were investigated in a Jerguson rocking cell reactor. It was assumed that the methane gas will occupy five small cages (three 512 and two 435663) whereas the largest cage (one 51268) will be occupied by a large (e.g., neohexane) molecule in a unit structure. A theoretical gas storage comparison with this methodology of storing methane in small cages showed that one unit volume of sH hydrate will store 201 volumes of methane gas. Three types of experiments were conducted to measure the methane gas storage in sH hydrate. It was discovered that sH hydrate promotion occurs with 0.1 weight percent solutions of lecithin and polyvinylpyrrolidone (PVP). These promoters also showed hydrates stabilization as hydrates melted at higher temperature compared to pure water hydrate. The heats of dissociation (ΔHdiss) below 0°C were estimated using Clausius‐Clapeyron equation and the experimentally measured equilibrium data for three hydrate structures (sI, sII, sH). Comparison of the estimated and calorimeter measured values (ΔHdiss) showed good agreement.

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