NOVEL LOW-CONCENTRATION AMPHIPHILIC INHIBITORS AND THEIR APPLICATION TO FLOW ASSURANCE

Surfactants and other low molecular weight compounds are known to affect natural gas hydrate (NGH) formation, mainly intervening on their kinetics of formation. Although the underlying supramolecular mechanisms of those effects are not completely clear, as a rule of thumb, anionic surfactants (such as., e.g., sodium dodecyl sulfate, linear alkyl benzene sulfonate, etc.) tend to behave as promoters of hydrate formation, by increasing its kinetics by some orders of magnitude. Notably, this effect is best shown well under a surfactant critical micellar concentration (cmc). On the other hand, several cationic surfactants have been reported as NGH inhibitors, and some of them proved to inhibit hydrate formation completely in over-pressurized, dilute water solutions. The present work reports on the design and modeling of novel cationic surfactants that have been tested as NGH inhibitors into a laboratory setting. Some of these molecules were designed in such a way as to satisfy two major requirements: (i) the presence of a cationic moiety at their hydrophilic head; and (ii) the presence of a particular head group geometry that could possibly fit into a forming hydrate cage. The latter feature should provide the molecule with the ability of acting as a "termination point" of hydrate nucleation and growth, by hindering the water molecules in the process of closing hydrate cages. An experimental field test facility is being realized by Italfluid Geoenergy s.r.l., an Italian well testing company which is the sponsor of this work. It is comprised by a by-pass pipeline to a NG production well with a production output of ca. 106 m3/day, and a pressure drop from ca. 280 to 70 bar. The by-pass pipeline will be provided with a fiber-optic camera for visual monitoring, pressure and temperature probes, and a inhibitor solution-injection port/pump.