摘要
【目的】水合物浆液输送可有效节约药剂使用成本,有望成为一种安全、经济、高效的天然气海管运输模式,目前研究多为限定形状的水合物生成和水合物浆液流变性的实验研究,水合物浆液自发结晶与流动剪切下的结晶研究较少。结晶是影响水合物浆液流变性的关键因素之一,对浆液中水合物结晶生长的研究有助于深入分析与预测海管的流动状态,对海管流动安全保障具有重要意义。【方法】首先通过理论分析了四氢呋喃(THF)水合物自发结晶过程,并利用偏光显微实验验证了该理论;进而使用高精度流变仪,探究动态剪切作用对结晶生长特性的改变及剪切速率、降温速率等因素对水合物浆液流变性的影响。【结果】静态原位THF水合物以棒状结晶生长,晶体的轴向生长速率大于径向生长速率;剪切作用使THF水合物析晶数量增多、单晶尺寸减小,同时促进棒状晶转变为块状晶。浆液黏度随剪切速率增大呈指数型下降,随体系降温速率增大先快速增加后达到稳定,随THF质量分数的提高而快速上升。【结论】THF水合物棒状晶端部更小的界面能与更大的温度梯度促进晶体轴向生长,而剪切作用会强制改变晶间方位,促使棒状晶团簇形成块状晶。研究结果可为流动体系水合物生成及水合物浆液输送等相关研究提供参考。(图9,表1,参21)
[Objective]Hydrate slurry transportation offers an effective way to save on reagent costs and is expected to be utilized as a safe,economical,and efficient mode for transporting natural gas through submarine pipelines.Current research is primarily focused on experimental studies related to hydrate formation in defined shapes and the rheological properties of hydrate slurry.Conversely,there have been few studies conducted on the spontaneous crystallization of hydrate slurry and crystallization under flow shear.Nonetheless,crystallization is one of the key factors influencing the rheological properties of hydrate slurry.Studying the crystal growth of hydrates in slurry aids in analyzing and predicting flow conditions within submarine pipelines,which is essential for ensuring the safe flow through these pipelines.[Methods]First,the theoretical analysis of the spontaneous crystallization process of tetrahydrofuran(THF)hydrates was conducted,and the results were subsequently verified through a polarizing microscopy experiment.Following this,a high-precision rheometer was employed to investigate variations in crystal growth characteristics under dynamic shearing,alongside exploring the impact of shear rates,cooling rates,and other factors on the rheological properties of hydrate slurry.[Results]The static in-situ THF hydrates exhibited growth into rod-shaped crystals,with axial growth rates surpassing radial growth rates.The shear effect induced higher quantities of THF hydrate crystallization,leading to reduced single crystal sizes and a transition in shape from rods to blocks.The viscosity of the slurry showcased an exponential decrease with increasing shear rates,initially rising sharply before stabilizing as the cooling rates of the flow system increased,and surging with higher THF mass fractions.[Conclusion]The smaller interfacial energy and greater temperature gradient at the ends of rod-shaped crystals of THF hydrates enhance axial growth.On the contrary,shear effects contribute significantly to altering intercr
作者
谢振强
李清平
杨硕
姚海元
秦蕊
XIE Zhenqiang;LI Qingping;YANG Shuo;YAO Haiyuan;QIN Rui(CNOOC Research Institute Co.Ltd.//National Key Laboratory of Marine Natural Gas Hydrate;CNOOC Bohai Experimental Center)
出处
《油气储运》
CAS
北大核心
2024年第11期1277-1284,共8页
Oil & Gas Storage and Transportation
基金
国家自然科学基金资助项目“深水油气及水合物开采过程中水合物堵塞监测及控制机理研究”,U21B2065
中海油集团公司“十四五”重大科技项目“深水混输管道堵塞预测及防控关键技术研究”,KJGG2022-0205。
关键词
海管
四氢呋喃水合物
偏光显微
结晶生长
浆液
黏度
submarine pipeline
tetrahydrofuran(THF)hydrate
polarizing microscopy
crystal growth
slurry
viscosity
