The formation of gas hydrates in oil and gas industries have been the subject of long-standing problems. For example, the hydrate formation may occur and block gas pipelines, which can lead to safety hazards. It may also occur in the drilling fluids that are used in deep offshore drilling operations, resulting in severe threats towards the operation safety. All of these also lead to catastrophic economic losses and ecological risks.

Various methods have been developed to control and mitigate the formation of gas hydrate. The techniques include heating, depressurization, water removal, and inhibition. In many cases, however, the hydrate inhibition by adding inhibitors is the only viable option. Two types of inhibitors are used nowadays: thermodynamic and kinetic inhibitors. Since exploration and production moves to deeper seas, the temperature and pressure in the field become in favor of hydrate formation and the addition of thermodynamic inhibitor becomes expensive and environmentally prohibitive; thermodynamic inhibitors need to be used at high concentration up to 50 wt%. The shortcomings of the thermodynamic inhibitors stimulated the search for kinetic inhibitors, which retard the hydrate formation by slowing down the hydrate nucleation rate, growth rate, and/or agglomeration rate. Kinetic inhibitors can be effective at low dosage (<1%) and therefore have significant economic and environmental advantages. The existing kinetic inhibitors, however, are still not believed to give an economic solution especially at high pressure and large degree of supercooling. It has also been identified for some cases that the combination of thermodynamic and kinetic inhibitors is still needed to give better results. Therefore, there is still a need to discover inhibitors that are more effective than the existing inhibitors.

The goals of this work are therefore to discover a new class of novel inhibitors. The performance of imidazolium-based ionic liquids as a new class of gas hydrate inhibitors has been investigated. Their effects on the equilibrium hydrate dissociation curve in a pressure range of 30 to 110 bar and the induction time of hydrate formation at 106 bar and a high degree of supercooling, i.e., about 25oC, are measured in a high-pressure micro differential scanning calorimeter. It is found that these ionic liquids, due to their strong electrostatic charges and hydrogen bond with water, could shift the equilibrium hydrate dissociation/stability curve to a lower temperature and, at the same time, retard the hydrate formation by slowing down the hydrate nucleation rate, thus are able to act as both thermodynamic and kinetic inhibitors. This dual function is expected to make this type of inhibitors perform more effectively than the existing inhibitors.