青岛建成天然气水合物模拟实验室

不久前 ,我国第一个拥有自主知识产权的天然气水合物模拟实验室在青岛建成 .天然气水合物作为重要的未来能源而越来越受到人们的重视。它是继煤炭和石油之后贮量巨大的战略性环保能源 .我国已在南海西沙海槽和东海冲绳海槽发现了水合物赋存的地球物理标志———ＢＳＲ .由于对水合物的调查研究尚处于初级阶段 ,对其物理化学性质缺乏了解 ,因此 ,建立天然气水合物模拟实验研究是非常及时和必要的 .该实验室模拟实验研究拟解决的问题包括 :含天然气的水溶液中能否形成水合物的晶核 ,水合物是在什么条件下生成及如何生成 ,沉积物对水合物生成的…     

气体处理装置中天然气水合物的研究

介绍了天然气水合物物化性质、天然气水合物在气体处理装置中的生成条件。指出脱除天然气中的水分、加注化学注剂等方法能有效防止天然气水合物的形成。     

基于LS-SVM的天然气水合物生成条件预测模型建立

在天然气管线内生成的水合物会严重影响天然气的开采、运输,因而天然气水合物的预测方法和防治措施备受重视。针对天然气水合物生成条件,考虑天然气组分对水合物生成的影响,为简化计算、提高预测精度,引入一种能够很好解决复杂物理问题的最小二乘支持向量机(LS-SVM),并且通过Matlab语言编程,建立了一种包含CH4浓度、CO2浓度、H2S浓度以及水合物生成温度为输入,水合物生成压强为输出的天然气水合物生成条件预测模型,同时将实验数据作为最小二乘支持向量机训练数据并进行预测分析。结果表明,该预测模型不仅拥有较高的预测精度,而且方法简单、可行,为天然气水合物生成条件预测提供了一种新的解决方法。     

水基钻井液中天然气水合物形成的研究进展

依据水基钻井液中天然气水合物生成的相关研究,结合理论与实践,介绍了一些钻井液处理剂对水合物生成的影响,重点概述了水基钻井液对天然气水合物生成的抑制效应,并简要说明了水合物抑制剂在钻井液中应用的相关研究。     

气体水合物生成机理和热力学模型的建立

提出了一个双过程水合物成核动力学机理模型 :(1 )拟化学过程生成基础水合物 ;(2 )小分子气体在基础水合物中的拟Langmuir吸附形成化学组成不恒定的水合物 .以此机理模型为基础建立了水合物热力学模型 .大量检验结果表明 ,新模型在预测气体水合物 (特别是由很复杂的天然气、凝析气和原油生成的水合物 )生成条件方面优于传统的vanderWaals -Platteeuw(vdW -P)模型及其改进型 ,且计算方法更简单 .     

促进天然气水合物生成因素的研究进展

介绍了几种促进天然气水合物形成的方法,综合阐述了吸附材料、添加表面活性剂、构造多孔结构、外加磁场、水合物记忆效应等方法对水合物生成的影响。通过分析不同促进天然气水合物生成方法的特点,如:纳米材料可以加快传热传质、增大气液接触面积,使用表面活性剂可以减小水分子表面张力、增大气体溶解率,盐类离子和合适的表面活性剂搭配使用可以促进水合物晶核形成,微波等外加磁场可以加快晶核形成等,为进一步研究天然气水合物开发和生成提供理论基础。     

天然气水合物的防治方法综述

随着油气田开发的不断深入和深海油气田的不断发展,天然气水合物的生成对油气田开发和管道运输均有很大危害。介绍了天然气水合物的形成机理和基本过程,概述了四种抑制天然气水合物生成的方法,分为干燥法,如干空气干燥法;压力控制法,如逐级节流法;加热法,如水套炉加热法、热水管加热法、电磁加热法;注入化学抑制剂法,如热力学抑制剂法、动力学抑制剂法和几种新型抑制剂法,并分析了各自的适用范围和作用机理,提出了国内今后的水合物抑止技术的发展方向。     

促进天然气水合物生成因素的研究进展

介绍了几种促进天然气水合物形成的方法,综合阐述了吸附材料、添加表面活性剂、构造多孔结构、外加磁场、水合物记忆效应等方法对水合物生成的影响。通过分析不同促进天然气水合物生成方法的特点,如:纳米材料可以加快传热传质、增大气液接触面积,使用表面活性剂可以减小水分子表面张力、增大气体溶解率,盐类离子和合适的表面活性剂搭配使用可以促进水合物晶核形成,微波等外加磁场可以加快晶核形成等,为进一步研究天然气水合物开发和生成提供理论基础。     

天然气水合物浆体流变性与安全流动边界研究进展

水合物安全流动技术作为一种新型的天然气运输管理方法具有广阔的发展前景,本文在综述国内外天然气水合物安全流动研究的基础上,分析了管道流动天然气水合物生成机理、特点和对油气管道的不利影响以及现有水合物安全流动研究存在的问题,包括实验管道长度较短、着重流动规律的研究而缺乏对流动边界的拓展等。进而对国内外天然气水合物低剂量抑制剂(low dosage hydrate inhibitor,LDHI)在保障天然气水合物安全流动、拓展天然气水合物安全流动边界以及螺旋流携带研究进行了总结评述;随后提出了利用螺旋流悬浮输送技术保障天然气水合物安全流动、拓展流动边界的新型方法。结合实验结果分析表明:螺旋流动从宏观上改变水合物浆体流动特点、有效提高水合物浆液的输送浓度并可拓展水合物安全流动边界。     

天然气水合物储运技术中水合物反应器的研究进展

可观的储气率与自保效应的存在使得天然气水合物能作为一种天然气储运的方式,并且在与其他如液化天然气、压缩天然气储运方式比较时有着自己独到的优势。但由于针对水合物储运的研究起步较晚,利用水合物储运天然气的技术尚未成熟。尤其是在水合物反应器的研究上,生成水合物的速率较低,无法达到工业生产所需要的水平。本文通过调研国内外文献与专利等资料,介绍了国内外天然气水合物储运技术发展状况,简述了水合物生成强化的物理化学手段与机械手段,详述了搅拌式等传统天然气水合物反应器与管式、超重力式等新型天然气水合物反应器的结构与工作原理。根据现有水合物反应器的特点与存在的问题,对水合物反应器的研究方向提出建议：未来应当加快对喷淋式、超重力式与流化床式反应器的放大研究,加快针对不同物理强化手段与机械强化手段的协同作用研究,建立起以天然气储运为目的的水合物反应器评价体系。     

Fundamental challenges to methane recovery from gas hydrates

The growing use of natural gas, cleanest of all available fossils fuels, is already raising concern regarding the long-term supply of this precious resource. The amount of methane in gas hydrates is much greater than all other presently known sources of methane. This paper describes some fundamental challenges, the location, magnitude, and feasibility of recovery, which must be addressed to recover methane from dispersed hydrate sources. For methane recovery, we briefly describe kinetic models of methane hydrate decomposition for temperature and pressure conditions that mimic in situ methane hydrate stability. We also propose the catalytic role of sediment impurities, if any, in inducing nucleation sites for hydrate formation. The availability of plentiful methane is important to avoid future energy crises, such as that which crippled the world economy three decades ago.     

Progress of Gas Hydrate Studies in China

A brief overview is given on the gas hydrate-related research activities carried out by Chinese researchers in the past 15 years. The content involves: (1) Historical review. Introducing the gas hydrate research history in China; (2) Gas hydrate research groups in China. There are nearly 20 groups engaged in gas hydrate research now; (3) Present studies. Including fundamental studies, status of the exploration of natural gas hydrate resources in the South China Sea region, and development of hydrate-based new techniques; (4) Future development.     

Clathrate‐hydrate formation by water spraying onto a porous metal plate exuding a hydrophobic liquid coolant

A novel technique for producing a clathrate hydrate from a gaseous guest substance was devised and experimentally tested. This technique employs a horizontally oriented spray nozzle and a vertically oriented porous metal plate placed in opposition to each other in a guest‐gas phase. Water is sprayed onto the plate while a precooled hydrophobic liquid coolant is seeping out of the plate to form a continuous film flowing down the plate surface. The coolant film is expected to sweep the heat released by hydrate formation away from the plate surface and, at the same time, to prevent the hydrate crystals from agglomerating on the surface thereby hindering the successive contact of the water spray with the coolant. A series of experiments has been performed to reveal the behavior of hydrate formation in the above scheme of guest‐gas/water/coolant contact operations. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

甲烷水合物分解实验

在体积10 L的静态反应器中研究了水合物分解动力学,考察了储存温度和水合物量等因素对水合物分解的影响。实验结果表明,水合物在273.15 K以下时存在一种异常的自我保护效应,其在268.05 K时分解速度最慢;而水合物的储运压力与储罐中的水合物量有关,当储罐容积一定时,分解压力随着储罐中水合物量的增加而增加,但水合物的分解百分比随着水合物量的增加而减少;最后提出了在一定压力下储运水合物的方法。以期为水合物法固态储存气体技术的工业化应用提供实验数据和理论依据。     

天然气水合物资源开采方法研究

自然界中存在大量的水合物,这些水合物已经被认为是将来重要的能源,本文分析了天然气水合物资源的特点,并综合介绍了现阶段提出的天然气水合物开采方法及模型,对比分析了典型开采方法,如热激发、降压和注抑制剂等的优缺点和经济性,评述了研究中存在的问题,并提出了今后研究的重点。     

The gas-adsorption mechanism of kinetic hydrate inhibitors

Molecular dynamics was employed to study the inhibition mechanism of vinyl lactam-based kinetic hydrate inhibitors (KHIs). By comparing the inhibition functions of the same KHIs at different initial locations, we found that the KHI molecules on the surface of hydrate nuclei could obviously prolong the hydrate induction time and exhibited the best inhibition effect. The impacts of KHIs on the methane migration and the arrangement of H₂O molecules were analyzed at the molecular level. A gas-adsorbing mechanism for KHIs (i.e., the KHIs with an excellent gas adsorption ability could reduce the supersaturation of methane in the aqueous solution, reinforce the migration resistance of methane to the nucleus, and further inhibit the hydrate growth) was proposed. In addition, the conformations of KHI polymer molecules in the aqueous solution are closely related to their inhibitory effect, that is, stretched skeletons and well-organized structures would maximize their inhibitory effect.     

Gas hydrate concentration measurements on sucrose solutions using a new pilot test rig

A new 750 cm³ pilot test rig based on the “isochoric pressure method” was designed and commissioned for the hydrate measurements to concentrate sucrose solutions. The reactor included an improved agitation system and enabled sampling of the sucrose solutions. The experimental method was validated be performing dissociation measurements for the CO₂ + water system. Gas hydrate kinetic and sampling data were measured for the CO₂ + sucrose solutions at sucrose concentrations between (12–60) ^oBrix, within the temperature range of (274.65–276.15) K and at pressures up to 3.70 MPa. Results showed that sucrose is a kinetic inhibitor. The data were modeled to obtain hydrate formation rate, storage capacity, gas consumption and apparent rate constant. Stage-wise concentration measurements were performed with reactor conditions at 274.65 K, 3.70 MPa and 130 rpm mixer speed with liquid sample withdrawal. A final sucrose product of approximately 60 ^oBrix was obtained.     

New approach for evaluating the risk of hydrate formation during transport of hydrocarbon hydrate formers of sI and sII

Classical industrial hydrate risk evaluation schemes are commonly based on water dew-point calculation. This method ignores another (new) route to hydrate formation based on adsorption of water onto rusty surfaces. Maximum allowable water contents in pure and mixtures of hydrate formers of Structures I and II hydrocarbons to avoid the risk of hydrate nucleation during pipeline transport have been studied using both the dew-point method and the new approach of adsorption of water onto hematite (rust). The estimates from this study suggest that the new approach (adsorption of water onto the rusty internal walls of pipelines and equipment) dominates. Thus, this approach could have an impact on designing natural gas dehydration systems. Free energy analysis has also been performed to show which molecule forms hydrate first based on the combined first and second laws of thermodynamics in terms of Gibbs free energy. © 2018 American Institute of Chemical Engineers AIChE J, 65: 1097–1110, 2019     

An investigation into the laboratory method for the evaluation of the performance of kinetic hydrate inhibitors using superheated gas hydrates

Kinetic hydrate inhibitors (KHIs) are used to prevent gas hydrate formation in gas and oilfield operations. Recently, a new KHI test method was reported in which hydrates are formed and re-melted just above the equilibrium temperature, before the fluids are re-cooled and the performance of the chemical as a KHI is determined. The method, which we have called the superheated hydrate test method, is claimed to be more reliable for KHI ranking in small equipment, giving less scattering in the hold time data due to avoiding the stochastic nature of the first hydrate formation. We have independently investigated this superheated hydrate test method in steel and sapphire autoclave tests using a gas mixture forming Structure II hydrates and a liquid hydrocarbon phase, which was necessary for satisfactory results. Our results indicate that hold times are shorter than using non-superheated hydrate test methods, but they are more reproducible with less scattering. The reduced scattering occurs in isothermal or slow ramping experiments even when the hydrates are melted at more than 10 °C above the equilibrium temperature (T_eq). However, if a rapid cooling method is used, the improved reproducibility is retained when melting hydrate at 2.4 °C above T_eq but lost when warming to 8.4 °C above T_eq. Using the ramping test method, most, but not all the KHIs tested agreed with the same performance ranking obtained using traditional non-superheated hydrate test methods. This may be related to the variation in the dissociation temperature of gas hydrates with different KHIs and different KHI inhibition mechanisms. Results also varied between different size autoclave equipments.