Inhibiting hydrate formation and agglomeration in water-in-waxy oil systems by combined anti-agglomerant: The synergistic effect between surfactants

•Combined anti-agglomerant (CAA) exhibited good hydrate agglomeration inhibition ability.•The cyclopentane hydrate nucleation time was prolonged with the addition of CAA.•The use of CAA resulted in great reduction in the maximum viscosity and steady viscosity of hydrate slurry.•The CAA adapted to wax-containing environments. Developing and screening economical, efficient, and environmentally friendly anti-agglomerants (AAs) to address obstructions caused by hydrate formation and agglomeration in complex multiphase systems (such as waxy and asphaltene-containing crude oil) has become one of the focal points in the flow assurance industry. In this study, a rheometer was utilized to investigate the formation characteristics of cyclopentane hydrates and the slurry rheological properties in water-in-oil systems with varying wax contents, different compositions of combined AA (CAA), and CAAs’ concentrations. This was done to examine the performance of CAAs in both wax-free and wax-containing environments. The results showed that, compared to systems using Span 80 as a standalone anti-agglomerant, CAA exhibited better nucleation inhibition at a high subcooling degree of around 15 °C. That can be attributed to lower diffusion coefficient of water molecules according to molecular dynamic simulation. In the presence of wax crystals, the kinetic inhibition ability of the CAA would be affected. CAA at low dosage (≤1 wt%) effectively reduced the maximum viscosity and steady viscosity of the slurry during hydrate formation (by 89.7 % and 94.5 %, respectively), demonstrating good anti-agglomeration performance. Additionally, the shear-thinning behavior and yield stress of hydrate slurries demonstrated the effective and stable ability of CAA to control hydrate blockages. In a wax-containing environment, the anti-agglomeration efficacy of CAA was weakened, requiring a minimum effective dosage of 1.5 wt%. CAAs exhibit synergism in promoting emulsification, inhibiting hydrate formation, and providing steric repulsion between hydrate particles, which possess the ability to inhibit hydrate formation and agglomeration for our 20 % water cut waxy oil–water systems.