Abstract:

An in-situ spiral separator was designed to sand removal and purification NGH to solve the problems of equipment wear, reservoir collapse and so on, based on the solid fluidization method and combined with the physical properties of mixed slurry. Then the effects of inlet velocity and inlet NGH volume fraction on the flow field and performance of the spiral separator were studied by CFD. It is obtained that as the inlet velocity increases, the velocity of the fluid in the flow field increases dramatically, especially the tangential velocity, and separation efficiency also increases, and the all separation efficiencies are more than 70%. At the same time, the pressure drop also increased sharply which leaded to sharply increase energy consumption in separator. As the increase of inlet NGH volume fraction, the flow field in the spiral separator hardly changed, the separation efficiency of NGH reduces, the sand separation efficiency increases, and the all separation efficiencies are above 70%. The pressure drop also gradually reduces. The results indicates that the separator has excellent sand removal performance. The tangential velocity is the critical velocity that determined the separation performance of the separators, which demonstrated that the increase of separator capacity is beneficial to the purification of NGH. The NGH concentration in gas hydrate reservoir has a certain influence on the efficiency of the separator. However, the separator also has some adaptability of the NGH concentration changes. The results also reveal the separation mechanism of NGH downhole spiral separation and provide a certain basis for the design of the spiral separator, and a novel technology and equipment for sand control in the exploitation of marine hydrate reservoirs is proposed.

Key words: natural gas hydrate, purification, downhole in-situ, spiral separation, flow field, performance, numerical simulation-CFD

摘要：

基于海洋天然气水合物固态流化开采方法的井下原位除砂提纯回填工艺，本文结合试采所得水合物浆体特征，设计用于解决设备磨损、储层坍塌等问题的井下除砂螺旋分离器，利用CFD数值模拟方法研究了入口速度和水合物体饱和度对井下除砂螺旋分离器流场和性能的影响，得到了随着入口速度增加，流场中流体的速度急剧增大，特别是切向速度、分离效率增加。当分离效率为70%以上，分离器内压降急剧增大，表明分离器内部的能量损耗不断增加；随着入口水合物体积分数的增加，螺旋分离器内流场变化微小，水合物分离效率降低，砂分离效率增加；分离效率为80%以上，压降逐渐降低。说明该分离器的最佳操作区为入口速度范围为3～5m/s，水合物入口体积分数15%以下。研究结果表明：本螺旋分离器具有极佳的除砂效果；切向速度是决定分离器分离性能的关键速度，处理量的增大有利于水合物的提纯；海底水合物储层中水合物饱和度变化对螺旋分离器分离效率具有一定的影响，但螺旋分离器对其具有一定的适应能力；揭示了水合物井下螺旋分离器除砂的分离机理，为其设计提供了一定的依据，为海洋水合物储层开采防砂提了一种新的技术及装备。

关键词: 天然气水合物, 纯化, 井下原位, 螺旋分离, 流场, 性能, 数值模拟-计算流体力学