Gas hydrates are inclusion compounds that form when water and natural gas come into contact at high pressure and low temperature. In hydrocarbon production, these conditions can be reached in cold areas (artic zones) or in subsea pipelines where hydrates formation can block production facilities. For a few years, a lot of work has been done to develop a new class of low dosage additives called kinetic inhibitors. These hydrosoluble additives are crystallization inhibitors : they delay nucleation and/or slow down crystal growth and/or agglomeration.

In this work, we have studied methane hydrate inhibition using AA/AMPS copolymers.

To study methane hydrate crystallization, we use a semibatch reactor equipped with a turbidimetric sensor allowing to measure the turbidity spectrum in the reactor. From turbidity measurements, it is possible to calculate the particles size distribution. This set up allows us to obtain mascroscopic results (induction time, gas consumption) and microscopic results (hydrate particles granulometry). With this set up, we have studied methane hydrate crystallization without additive at macroscopic and microscopic scale and at different pressures and stirring rates. Copolymers have then been tested in the same experimental conditions. Influence of copolymer composition, molecular mass and concentration have been studied. These copolymers have an inhibiting effect on crystals formation kinetics. Optimal performances are obtained for an AMPS molar ration of 50%. Futhermore, minimum additive concentration and minimum mean molecular mass are needed to obtain a kinetic effect on crystals. The higher the pressure (driving force) and the higher the stirring rate (gas transfer), the higher these minimum values.

To understand results with or without additives, we have used a model. Relating gas consumption rate to crystal growth, it seems that the copolymer inhibits crystal growth by mean of a dead zone. Then using a model based on a population balance equation, we have established a first identification of the crystal source with and without additives.

Finally, the last part of this work is related to the study of a model formulation from AA/AMPS copolymers. The formulation presents an enhancement of the kinetic inhibition compared to the copolymer performance alone. The particular behavior of tetrabutylammonium bromide contained in the formulation has been underlined.