Risk of Hydrate Formation during the Processing and Transport of Troll Gas from the North Sea

Abstract

The North Sea is covered by close to 8000 km of pipelines transporting hydrocarbons. Pressures are high, and temperatures are generally low. Temperatures can be as low as 272 K in the north, due to seawater salinity, and rarely exceed 279 K for the southernmost pipelines. The most common procedure for hydrate risk analysis involves the calculation of the water dew point for a gas mixture containing water. Pipelines are normally covered by rust even before they are put in place. Rust is a mixture of iron oxide, and one of the most stable is hematite, Fe2O3. Because of the distribution of partial charges on the hematite surface, adsorbed water will be highly structured, resulting in low chemical potentials and a low adsorption energy for the water molecules. The adsorbed water on the walls is thermodynamically cold in terms of the functional derivative of the internal energy of the adsorbed layer with respect to the entropy of the adsorbed layer. This fact adds on top of the walls being the coldest region o...