Emulsion stability of surfactant and solid stabilized water-in-oil emulsions after hydrate formation and dissociation

Abstract

Hydrates are ice-like crystalline compounds that can cause plugging of crude oil pipelines. Stable water-in-oil emulsions aid in preventing hydrate particle agglomeration and hydrate plug formation in crude oil pipelines. The type of stabilizers present in water-in-crude oil emulsions also influences hydrate formation. Therefore, the effect of hydrate formation and dissociation on the stability of water-in-oil emulsions stabilized using either surfactants or solid particles was investigated. In addition, the difference in the effect of hydrate formation and dissociation on water-in-oil emulsions stabilized using solid particles of varying hydrophobicity was investigated. Furthermore, the effect of hydrate formation and dissociation on droplet size of the water-in-oil emulsions was quantified. The results showed that, the water-in-oil emulsions stabilized using moderately hydrophobic solid particles resisted emulsion destabilization, after hydrate formation and dissociation, unlike water-in-oil emulsions that were stabilized using either surfactants or highly hydrophobic solid particles. Also, after hydrate dissociation, for surfactant stabilized emulsions, the droplet size of water in the residual emulsion increased by more than 85% as compared to the droplet size before hydrate formation. On the contrary, for solid stabilized emulsions, no significant change in the droplet size of the residual emulsion was observed after hydrate dissociation as compared to the water-in-oil emulsion before hydrate formation. A conceptual mechanism was proposed to explain the observed difference in the stability of solid stabilized water-in-oil emulsions when subjected to hydrate formation and dissociation. Additionally, dynamic interfacial tension measurements were carried out to explain the difference in the initial droplet size of solid stabilized and surfactant stabilized water-in-oil emulsions.