含蜡及表面活性剂环戊烷水合物浆液生成及黏度特性

Formation and viscosity characteristics of cyclopentane hydrate slurry with wax and surfactant

随着油气资源开采不断向深水领域发展,在深水管道多相混输过程中,低温高压的输送环境极易导致水合物和蜡等固相沉积堵塞管道的问题产生,尤其当蜡和水合物同时存在时,集输管道将面临更高的堵管风险。为此,使用流变仪研究了含蜡和表面活性剂(Span 80)的油水体系中环戊烷水合物的生成规律及水合物浆液流变性,明确了含蜡量(质量分数,下同)、Span 80浓度(质量分数,下同)等因素对蜡-水合物共存体系临界时间及浆液剪切稀释性的影响规律。结果表明,Span 80浓度为1.0%时,含蜡量由0.00%增大至1.00%,水合物生成临界时间由25.8 min延长至49.8 min,增幅约93%。在Span 80浓度为1.5%、2.0%及3.0%时,水合物生成临界时间同样随含蜡量增大而延长,增幅分别为113%、93%及241%。对中低含蜡量体系(≤0.75%),水合物生成临界时间随Span 80浓度的增大而缩短;对高含蜡量体系(≥1.00%),水合物生成临界时间则随着Span 80浓度的增大呈现波动变化。此外,随着水合物的生成,含蜡与不含蜡体系水合物浆液的黏度均先快速增大再逐渐减小并趋于稳定,含蜡体系水合物浆液的黏度峰值与最终平衡黏度均显著大于不含蜡体系的对应值。通过比较稠度系数和流动特性指数,发现含蜡体系水合物浆液的流动特性指数随着含蜡量、Span 80浓度的增大而增大,含蜡油水乳状液、水合物浆液及含蜡水合物浆液均具有剪切稀释性,含蜡水合物浆液则具有更强的剪切稀释性。

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 oilwater 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.