Formation of Methane Hydrate in Oil–Water Emulsion Governed by the Hydrophilic and Hydrophobic Properties of Non-Ionic Surfactants

As oil and gas production moves into deep water, the formation of gas hydrate has been a primary flow assurance challenge in the deep water pipelines. Because of the complex composition of crude oil and various additives, the objective of this work is to study the effect of additive hydrophilic–hydrophobic property on hydrate formation in the emulsion, which usually occurs in pipelines. The formation experiments of methane hydrate in emulsion with the same water cut but surfactants of different hydrophilic lipophilic balance (HLB) values were conducted. The emulsion was prepared with mineral oil, deionized water, and two types of non-ionic surfactants (Span 80 and Tween 80). The experimental results indicate that with the HLB value increasing, the emulsion was divided into relatively stable water-in-oil, the phase transition region, and stable oil-in-water; meanwhile, the effect of the hydrophobic surfactant on hydrate formation also changed from inhibition to promotion to inhibition. In addition, hydrate...