Microscopic and rheometric study on cyclopentane hydrate agglomeration and slurry viscosity characteristics in the presence of amide-based surfactants

Addressing the blockage issues arising from hydrate formation and aggregation in complex multiphase systems has long been a significant focus in the field of flow assurance for oil and gas pipelines. There is an urgent need to develop and identify cost-effective, efficient, and environmentally friendly hydrate anti-agglomerants. A micro-mechanical force device and a rheometer were employed to investigate the anti-agglomeration effects of Span80 and amide-based surfactants (DPLA and DPCA) in gas–water and oil–water systems. The results indicated that in the gas–water system, compared to the surfactant-free system, the addition of varying concentrations of surfactants lead to a reduction in cohesive force of hydrate particles by 70.39 % to 84.10 % (1 wt% Span 80). The amide-based surfactant, DPLA, reaches a maximum reduction of 82.38 % (from 21.51 ± 0.78 mN/m to 3.79 ± 0.29 mN/m) with a concentration of 0.5 wt%. The cohesive force between hydrate particles and wall droplets was reduced by 40.35 % to 54.59 %, with the maximum reduction of 54.59 % (from 484.28 ± 26.28 mN/m to 219.88 ± 21.36 mN/m at 0.3 wt% DPCA). Compared to Span80, amide-based surfactants demonstrated similarly excellent performance in reducing cohesive forces. Considering the significant changes in the surface morphology of hydrate particles upon the addition of surfactants, this study also revealed a strong positive correlation between both liquid bridge width and circularity with cohesive force (r 1  = 0.8233, r 2  = 0.6066), while surface roughness exhibited a weak negative correlation (r 3  =  − 0.3821). In the oil–water system, although the critical time for hydrate formation in DPLA or DPCA-containing emulsions was markedly shortened compared to the base emulsion, both peak viscosity and steady viscosity of hydrate slurries were significantly reduced at medium to high concentrations of DPLA or DPCA. The maximum reductions in steady viscosity and peak viscosity for the DPLA-containing system were 93.94 % (0.6 wt%) and 78.59 % (0.4 wt%), respectively, while for the DPCA system, they were 89.55 % (0.8 wt%) and 55.95 % (0.8 wt%). Although DPCA and DPLA promoted hydrate formation, they still demonstrated excellent anti-agglomeration efficacy and potential for synergistic effects. The anti-agglomeration capability of DPCA was slightly weaker than that of DPLA, with both exhibiting comparable effects at medium to high concentrations.