Effect of cocoamidopropyl betaine on CH4 hydrate formation and agglomeration in waxy oil-water systems

Hydrates and waxes are the two major factors that provoke flow assurance issues in deep-water multi-phase transport units in the energy industry, and the application of eco-friendly and efficient anti-agglomerants is one of the key strategies for addressing this problem. The present work investigates the anti-aggregation performance of an environment-friendly amphoteric surfactant, Cocamidopropyl betaine (CAPB), in wax-containing oil-water systems. It is found that the anti-aggregation performance of CAPB in wax-containing oil-water systems is synergistically influenced by the concentration of CAPB and the wax content. The addition of 1.5 wt% CAPB can effectively inhibit hydrate formation and improve the flow of hydrate slurry in oil-water systems without wax. The addition of 2.0 wt% CAPB slows the growth rate of hydrates and reduces inter-particle aggregation in waxy oil-water systems containing 2.5 wt% n-Pentadecane. The wax content does not affect the amount of hydrate formation but influences the induction time and growth rate of hydrate formation. Additionally, the microscopic analysis further reveals that the addition of surfactant CAPB does not affect the crystal structure of hydrate, but has a significant influence on the distribution of methane molecules in the crystal cavities, particularly in wax-containing oil-water systems.