Knowledge Management System Of Guangzhou Institute of Energy Conversion, CAS
| 管道中水合物浆安全流动研究 | |
| Alternative Title | Flow assurance of hydrate slurries in pipeline |
| 王武昌 | |
| Thesis Advisor | 樊栓狮 |
| 2008-05-30 | |
| Degree Grantor | 中国科学院广州能源研究所 |
| Place of Conferral | 广州能源研究所 |
| Degree Name | 博士 |
| Keyword | 水合物浆 安全流动 堵塞 管道 |
| Abstract | 为了确保油气输送的安全，石油工业一直在寻求各种方法来防止水合物可能带来的危害，然而随着一些环境恶劣的油田以及一些深海油田投入开发，传统的水合物抑制方法逐渐难以经济有效地应用。因此新型的低剂量抑制剂及其伴随产生的风险管理逐渐得到重视和应用。作为风险管理的基础，如何保证水合物在管道中的安全流动已经成为了全世界水合物研究的一个焦点。 目前对于不同形态水合物的流动特性，国内外的研究都不系统，缺乏可靠的水合物流动数据，而且对于水合物在管道中流动时会不会形成堵塞及能否安全流动目前还没有一个明确的判断方法，而这恰恰正是工业应用最需要的。与此同时，管道中水合物堵塞的形成过程和机理仍然不明确，水合物堵塞的过程会影响堵塞体的结构和特性，是事故出现后堵塞定位和解堵等补救措施有效实施的基础。因此本文通过研究三种低压水合物在管道中的流动，提出了判断管道中水合物流动安全性的模型，可以为油气管道中水合物的安全流动判断提供有效地指导。 本研究设计并建造了一套环道系统，管道为不锈钢管，内径42mm、长30m。整个环道系统置于环境控制室中，系统可以模拟水平管道、地形低凹段以及立管内的正常流动、停输及停输后再启动等不同工况下的水合物流动情况。利用此环道进行了HCFC-141b、THF及TBAB三种水合物在管道中的生成以及水合物浆的流动实验，并以实验数据为基础分析了管道中水合物的安全流动，得到了一些重要的结论： HCFC-141b和THF在管道中流动时，水合物的生成几乎不存在诱导时间，都存在一个临界体积分数，分别为37.5％和50.6％，当体积分数大于临界体积分数时，水合物颗粒聚集加剧，管道中形成泥状水合物，压降梯度会急剧增加，并最终造成管道堵塞。二者的泥状水合物都为Bingham流体，通过分析两种水合物的物性数据提出了两种水合物浆流动的压降计算模型。 与HCFC-141b和THF水合物颗粒几乎不黏附在管壁上不同，TBAB水合物，尤其是其Ⅱ型水合物颗粒很容易黏附在管壁上，造成管道截面积逐渐减小，最终堵塞管道。而阻聚剂Span80可以有效的减缓TBAB水合物颗粒在管壁上的黏附。初步分析，TBAB水合物的黏附过程中分子扩散起主要作用。 通过三种水合物实验发现水合物浆在管道中流动时，造成管道处于不安全状态甚至堵塞主要有两种机理：即形成泥状水合物或者在管壁上严重黏附，这两种现象都会使管道处于危险状态，而这两种情况都是由管道中水合物颗粒的聚集造成的。因此提出并推导了一个反映水合物颗粒聚积能力的无因次数Ch，指出可以用Ch来判断管道中水合物浆流动的安全性，从而建立了水合物在管道中安全流动的判断模型。并利用实验数据对THF和HCFC-141b两种水合物浆的安全流动进行判断，结果表明提出的安全流动判断模型是有效的。 本研究得到的THF、HCFC-141b及TBAB三种水合物浆的流动特性可以为实际工程中水合物浆的流动提供有效的数据，而且提出的水合物在管道中形成及堵塞的机理及管道中水合物浆流动安全性的判断模型，可以为制冷系统的安全运行提供判断标准，同时可以为油气混输管道水合物流动安全的判断提供指导，具有一定的工程意义。 |
| Other Abstract | Hydrates are ice-like crystalline compounds and are likely to form in offshore condensate pipeline running at high pressure and relative low temperature, which has resulted in great effects on the petroleum industry. In order to keep the pipeline in the safe region many kinds of methods have been studied throughout the world. However, since 1970s as oil companies have been producing in more and more unusual environments, the limitation of traditional methods by preventing the formation of hydrates is more and more obvious. So, new methods for hydrate prevention have been developed and the main strategies on hydrate are changing from avoiding the formation of hydrate to risk management with hydrates in pipelines, the keys of which are to develop new kinds of economical low dosage hydrate inhibitors (LDHI) and prevent the formation of hydrate plugs in pipelines. However, at present there are very few conclusions on the formation and blockage of hydrates in pipeline. Moreover, there are no effective methods to judge the pipeline is running safely or not. So experiments on three kinds of hydrate slurries were conducted and a model to judge the safety of the pipeline was proposed, which can give some introductions to the further studying on natural gas hydrate slurries and to judge if the pipeline can be run safely or not. A new flow loop with a diameter of 42.0mm and length of 30.0m was designed and constructed in an environmentally controlled room, which can be used to study the flow characters of hydrate slurries in different flow conditions. Experiments on three kinds of hydrates slurries including HCFC-141b, THF and TBAB were conducted, which give rises to a series of important conclusions as follows: All these three kinds of hydrates formed very easily in pipeline with the help of flow turbulence and there is almost no inducting time in the forming processes. According to the experiments, both HCFC-141b and THF slushlike hydrates are Bingham fluids. There are critical hydrate volume concentrations of 37.5% for HCFC-141b hydrate slurry and 50.6% for THF hydrate slurry respectively. The slushlike hydrates occur and the pressure drops of the flowing hydrates in pipeline increase substantially when the volume concentrations of hydrates in pipeline are larger than the critical ones. At last, relations to estimate the pressure drop of these two kinds of hydrate slurry in pipeline were presented and verified. Experimental results were compared to the estimated results, which showed a good agreement. Aggregations of hydrate particles are obvious with the increase of the hydrate volume concentration in pipelines. Both HCFC-141b and THF hydrate particles don’t adhere to the wall of the pipeline and pastes including hydrates and water occur when the volume concentrations is close to 70%, which results the whole blockage of the pipeline. On the contrary, hydrate particles of TBAB hydrate are inclined to adhere to the wall of pipeline, which attribute to the molecular diffuseness and results in the decrease of the pipe section piece by piece. A kind of AA named Span80 with a concentration of 3.5wt% can weaken the adherence of TBAB hydrate on pipeline effectively. According to the experiments, occurrence of slushlike hydrates or badly adherence of hydrates on pipeline may result in the blockage of hydrates in pipeline because of the aggregation of hydrate particles. So, a non-dimensional parameter Ch is proposed, which shows the agglomerating probability of hydrate particles in pipeline and can be used to judge the safety of the pipeline. Moreover, a safe model based on Ch to judge the safety of flow hydrate slurries was presented and verified with the experimental data of HCFC-141b and THF hydrates, which shows that the model is effective to judge if the pipeline can be run safely or not. And the model will be great helpful to judge the safety of hydrates flow in oil and gas pipeline. |
| Pages | 115 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.giec.ac.cn/handle/344007/4065 |
| Collection | 中国科学院广州能源研究所 |
| Recommended Citation GB/T 7714 | 王武昌. 管道中水合物浆安全流动研究[D]. 广州能源研究所. 中国科学院广州能源研究所,2008. |
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