Hydrate anti-agglomeration and synergy effect in normal octane at varying water cuts and salt concentrations

Abstract

Abstract Anti-agglomeration is a promising approach to address hydrate risks in oil and gas flowlines from the deep sea. Salt concentration of the coproduced water with hydrocarbons is known to affect anti-agglomeration. Most studies report improvement in efficiency of anti-agglomeration but some authors report a decrease from salts. In this work, the effect of water cut (ratio of aqueous phase to total liquid) and NaCl concentration on the effectiveness of the cocamidopropyl dimethylamine anti-agglomerant (AA) are investigated in normal octane and methane systems. We also investigate the synergic effect of a cosurfactant (Span 80) in improving the performance of the AA at water cuts of 10%–30%. A likely mechanism of the synergism is suggested: the co-surfactant (Span 80) promotes the dispersion of water droplets in the oil phase and the AA prevents the agglomeration of the hydrate particles. We investigate emulsion formation and the phase behaviour of octane/brine/AA/Span 80 emulsion to shed light on the mechanisms at play. A solid-like fluid which hardly moves under gravity is observed when the normal octane and water/brine and the anti-agglomerant are mixed at a water cut of 95%. The solid-like behaviour which is attributed to flocculation can be remedied by the introduction of alcohols in the solution. There are similarities in emulsion formation and hydrate anti-agglomeration of normal octane and a condensate liquid which was investigated recently and there are also major differences.