摘要
深海含蜡油气混输管道在低温、高压的输送环境下,容易引发蜡晶与天然气水合物(以下简称水合物)共存的现象并相互影响,加重管道堵塞。为了探明蜡晶析出对水合物生成动力学特性的影响情况,采用正庚烷(n-C_7)与正二十八烷(n-C_(28))混合液模拟含蜡输送体系,应用高压可视化反应釜观察水合物生成动力学实验,结合水合物生成过程中的可视化图像,研究不同蜡含量对水合物成核时间、耗气量和耗气速率的影响规律。实验结果表明:(1)在274.15 K、3.5 MPa的实验条件下,蜡晶析出加快了水合物的成核和生长过程,在蜡晶浓度(ω)为3.3%的体系中,水合物诱导时间最快缩短了56.9%;(2)同一温度、压力条件下,蜡晶析出增大了气体消耗量,并且蜡晶析出量越多累计耗气量就越大,在ω为3.3%的体系中,最大气体耗气率增加了2.15倍;(3)同一温度、压力条件下,含蜡体系中水合物的生长速率远远高于不含蜡体系。结论认为,蜡的存在会加速水合物的生成,增加水合物的沉积量,加大管道堵塞风险;为了确保深水油气混输管道的输送安全,应及时清理管道内析出的蜡晶。
In the transportation environment of low temperature and high pressure, wax crystal and hydrate tend to coexist and influence each other in the subsea multiphase pipelines of waxy oil and gas. Thus, pipeline blockage gets serious. In order to investigate the influ- ence of wax crystal precipitation on the kinetic characteristics of hydrate formation, we adopted a mixture of n-heptane （n-C7） and n-oc- tacosane （n-C28） to simulate a wax-containing transportation system, and a high-pressure visual reactor was used to observe the kinetic experiment of hydrate formation. Then, based on the visible image in the process of hydrate formation, the influence rules of wax content on nucleation time, gas consumption and gas consumption rate of hydrate were investigated. And the following experimental results were obtained. First, under the experimental conditions of 274.15 K and 3.5 MPa, the nucleation and growth process of hydrate accelerates due to the precipitation of wax crystal. In the system with wax crystal concentration （co） of 3.3%, the hydrate induction time is shortened by 56.9% in the maximum degree. Second, under the same temperature and pressure, gas consumption increases due to the precipitation of wax crystal, and the cumulative gas consumption increases with the rise of the precipitation amount of wax crystal. In the system with wax crystal concentration （co） of 3.3%, the maximum gas consumption rate increases by 2.15 times. Third, under the same temperature and pressure, the growth rate of hydrate in a waxy system is much higher than that in a non-waxy system. In conclusion, the existence of wax speeds up the formation of hydrate, and increases the hydrate deposit and the pipeline blockage risk. To ensure the transportation safety of subsea .oil/gas multiphase pipelines, therefore, it is necessary to remove in time the wax crystal precipitated in the pipelines.
出处
《天然气工业》
EI
CAS
CSCD
北大核心
2018年第3期103-109,共7页
Natural Gas Industry
基金
中国石油科技创新基金"水合物脱除天然气中CO2工艺与设备研究"(编号:2016D-5007-0607)
国家自然科学基金项目"基于螺旋流的天然气管道水合物堵塞风险边界拓展机制研究"(编号:51574045)
关键词
天然气水合物
正庚烷
正二十八烷
蜡晶
动力学特性
成核时间
耗气量
耗气速率
管道堵塞风险
Hydrate
n-heptane
n-octacosane
Wax crystal
Kinetic characteristics
Nucleation time
Gas consumption
Gas consumptionrate
Risk of pipeline blockage
