As oil and gas exploration continues to expand into deepwater areas,the low temperature and high pressure transmission environment during multiphase mixed flow in deepwater pipelines is highly prone to causing problems such as hydrate and wax deposition and pipeline blockage.Especially when wax and hydrate coexist,the gathering and transmission pipelines will face higher risks of pipeline blockage.To this end,the rheological properties of cyclopentane hydrate formation and hydrate slurry rheology in oil-water systems containing wax and surfactant(Span 80)were investigated using a rheometer.The effects of factors such as wax content(mass fraction,the same below)and surfactant concentration(mass fraction,the same below)on the critical time and shear dilution of wax-hydrate coexistence systems were clarified.The results show that when Span 80 concentration is 1.0%,the wax content increases from 0.00%to 1.00%and the critical time of hydrate formation increases from 25.8 min to 49.8 min,an increase of about 93%.When the concentration of Span 80 is 1.5%,2.0%and 3.0%,the critical time of hydrate formation also increases with the increase of wax content by 113%,93%and 241%,respectively.For the low-to-medium wax content systems(≤0.75%),the critical time of hydrate formation shortens with the increase of Span 80 concentration.For the high wax content systems(≥1.00%),the critical time of hydrate formation fluctuates with the increase of Span 80 concentration.In addition,with the hydrate formation,the viscosity of both wax-containing and wax-free systems first increases sharply,then gradually decreases and tends to be stable.Both the peak viscosity and final equilibrium viscosity of wax-containing hydrate slurry are significantly higher than those of the wax-free system.By comparing the consistency coefficient and flow characteristic index,it is found that the value of characteristic index for wax-containing hydrate slurry increases with the increase of wax content and Span 80 concentration.The wax-containing oil-water emulsion,hydrate slurry and wax-containing hydrate slurry systems all exhibit shear-thinning behavior,and the wax-containing hydrate slurry exhibits a stronger shear-thinning behavior.
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