Effects of Salt on the Crystal Growth and Adhesion Force of Clathrate Hydrates

Abstract

In the offshore oil and gas developments, the problems in relation to hydrate flow assurance are always influenced by the existence of salt in the pipeline systems. Even though the salt effects are essential factors associated with the adhesion force between clathrate hydrate and aqueous solutions, the roles of salt in hydrate adhesion behaviors have rarely been considered. This study aims at understanding the effects of salt on not only the adhesion force variations but also the transformation of hydrate growth morphology. The presence of salt did not profoundly influence the change in the adhesion force of the hydrate probe with surfactant-free solutions, whereas it drastically reduced the adhesion force of the hydrate system with surfactantdissolving aqueous solutions. The experimental results also revealed the inhibition effect of salt on the hydrate crystal growth through the observation of microscopic images. Furthermore, dynamic adhesion behaviors were unprecedentedly captured in terms of gradual increases in adhesion force because of wetting of aqueous solution on the hydrate probe surface and additional hydrate formation. The present work related to the salt effects on the adhesion behaviors could provide novel insights into the dynamic adhesion during the crystal growth of hydrates in the offshore oil and gas production systems.

Surface morphology effects on clathrate hydrate wettability

“…We found that our estimates for the work of adhesion are consistent with experimental measurements [93], suggesting that simulations such as those presented here could be useful for the estimation of adhesion force interactions between hydrate particles and water droplets. To our knowledge, this is the first determination of the hydrate-water adhesive forces achieved by employing molecular simulations under realistic conditions, as most previous experimental studies were performed using hydrates stable at atmospheric pressure, such as cyclopentane [93,[95][96][97]. Our work contributes to closing the gap between experimental and realistic models of clathrate hydrates.…”

Interaction Between the Cyclopentane Hydrate Particle and Water Droplet in Hydrocarbon Oil

“…(6) Step 5 was repeated until the colorless solvent dripped through the filter paper, meanwhile the filter needed to be replaced after a few rounds for better results. (7) The precipitates were dissolved into toluene with a mass ratio of 1:20 after collecting from the filter paper. (8) To remove solid particles, the mixture was shaken for 20 min and divided equally into Teflon tubes before centrifuging at 20,000g for 20 min.…”

“…1,5,6 However, thermodynamic inhibitors are economically and environmentally unacceptable. 1,7 Another strategy proposed to reduce the plugging tendency of conventional production systems is the addition of kinetic inhibitors.…”

“…One strategy to counter this flow assurance challenge is to introduce thermodynamic inhibitors so that the stable state of the hydrate can be shifted toward higher pressures or lower temperatures. ,, However, thermodynamic inhibitors are economically and environmentally unacceptable. , Another strategy proposed to reduce the plugging tendency of conventional production systems is the addition of kinetic inhibitors.…”

Anti-gas hydrate surfaces: perspectives, progress and prospects

“…Nevertheless, the above results clearly illustrated that hydrate adhesion strength on surfaces at the microscale were affected by the surfaces' chemical properties in general. 184 The above-mentioned studies carried out by Das et al supported such a conclusion. 163 Although the OTS-coated surface had higher surface energy than the FS-coated surface, the hydrate adhesion force on the OTS-coated surface was lower.…”