多孔介质内甲烷水合物生成动力学研究

天然气水合物作为一种潜在的新型潜在替代能源,分布广泛、储量巨大。水合物生成动力学特性对于了解自然界天然气水合物形成规律与水合物相关技术应用具有重大意义。针对甲烷水合物生成动力学特性进行研究,设计开发了甲烷水合物生成测试系统,研究了不同温度和不同孔隙粒径的多孔介质对于水合物生成动力学的影响。结果表明,随着温度的降低以及多孔介质孔隙粒径的减小,甲烷水合物生成过程中的气体消耗速率越快,生成结束时消耗的气体的量越多。同时,利用水合物生成多步骤机制模型,获得了甲烷水合物生成过程各中间产物的变化规律。     

含甲烷水合物多孔介质渗透性的实验研究

为研究多孔介质中甲烷水合物对其渗透性的影响,开发了一套适合在该条件下测量渗透性的实验装置。研究了多孔介质孔隙度与渗透率的关系;用BZ-01、BZ-02玻璃砂模拟多孔介质进行了渗透率测量实验,测试了不同甲烷水合物饱和度下多孔介质渗透率的变化情况。结果表明,多孔介质中甲烷水合物的存在会导致其渗透率急剧下降,饱和度-渗透率曲线呈指数分布。根据实验数据拟合出了渗透率随饱和度变化的经验公式,并将实验数据与渗透率模型进行了比较,发现在实验条件下生成的甲烷水合物符合平行毛细管模型,水合物占据毛细管中心,多孔介质中的流动形成环状流。     

天然气在渐变型多孔介质中的预混燃烧

设计了孔径沿程变化的渐变型多孔介质(GVPM)燃烧器，为了解天然气在其中的预混燃烧特性，对燃烧室气体、固体温度分布和CO、NO；污染物排放进行了测量．试验研究了渐变型多孔介质中燃烧的温度场分布、火焰移动、污染物排放、稳定性及多孔介质孔径结构对燃烧特性的影响规律．将研究结果与几种均匀型多孔介质(HPM)中的燃烧进行比较，发现渐变型多孔介质中的燃烧可以有更多的优点，包括均匀温度场分布、极低污染物排放、高火焰速度、高稳定性、宽燃烧极限和有很大的负荷调节范围等．     

海底天然气水合物成因影响因素探讨

自然界中的天然气水合物资源主要存在于海洋中,海底的自然条件是形成天然气水合物的基础.文章探讨了多孔沉积物、孔隙水成分等因素对天然气水合物形成条件的影响,分析了海底天然气水合物的成藏特性.     

天然气水合物的资源与环境意义

天然气水合物是在低温高压环境下由水分子和气体分子构成的结晶状特殊固体化和物,它主要分布于永久冻土带及浅海大陆架及深海平原沉积物中。天然气水合物的开发利用涉及两个方面的问题:①从资源方面考虑,天然气储量巨大,能够满足人类未来清洁能源的需求;②从环境方面考虑,甲烷的释放将引发全球气候变化和一系列的海洋地质灾害。因此,在开发利用天然气水合物之前,必须有超前的防范措施,以防止天然气水合物对环境造成的不良影响。     

羧甲基纤维素钠对CH4水合物形成过程的影响

羧甲基纤维素钠（CMC-Na）是水基钻井液中的重要组分,为研究CMC-Na对天然气水合物热力学和动力学的影响,实验测量了质量浓度介于0.5%～1.5%的CMC-Na溶液中甲烷水合物的相平衡条件,以及275.2 K、6 MPa的初始条件下CMC-Na溶液中甲烷水合物的形成过程。研究结果表明,CMC-Na对甲烷水合物的热力学稳定性具有微弱的抑制作用,相同压力下相平衡温度降低了0.1～0.2 K。CMC-Na溶液中形成的甲烷水合物为Ⅰ型,水合物数为5.84～5.90。在CMC-Na溶液中,甲烷水合物形成所需的诱导时间大大缩短,表明CMC-Na对甲烷水合物的形成过程具有促进作用。在CMC-Na溶液中水合物生成所需气体消耗量呈阶段式增长。水合物转化率低于35%的情况下,已经生成的水合物没有对搅拌器叶片形成持续附着进而卡住搅拌器。因此,CMC-Na对甲烷水合物的热力学稳定性具有一定的负面影响,对水合物的形成具有一定的促进作用。另外,CMC-Na能够降低水合物生成过程中搅拌扭矩的波动,对维持搅拌的正常运行具有重要作用。     

含甲烷水合物的石英砂渗透率实验和分形模型对比研究

含水合物的多孔介质渗透率是影响水合物开采的关键参数,多孔介质渗透率与水合物的饱和度密切相关。定量研究多孔介质渗透率随水合物饱和度的变化,对自然界中天然气水合物藏内渗流场的研究具有重要的理论价值。本文以平均粒径为139.612 μm的石英砂为多孔介质,采用稳态注水法测量在不同甲烷水合物饱和度（0 ~ 28.56%）下的石英砂渗透率,将实验数据与两种不同水合物赋存形式（颗粒包裹、孔隙填充）下的石英砂渗透率二维分形模型进行了对比。结果表明,石英砂渗透率比K_r随甲烷水合物饱和度S_h的增大呈现指数减小的趋势。当水合物饱和度低于11.83%时,渗透率比下降缓慢。而当水合物饱和度高于11.83%时,渗透率比下降迅速;当饱和度指数n = 12时,渗透率分形模型与实验数据吻合良好。通过分形模型与实验数据对比,发现当水合物饱和度低于11.83%时,甲烷水合物的赋存形式为颗粒包裹型。在11.83% ~ 28.56%水合物饱和度范围内,甲烷水合物的赋存形式为孔隙填充型。本研究成果量化了石英砂渗透率与甲烷水合物饱和度的关系,确定了含甲烷水合物的石英砂的渗透率分形模型的参数取值。     

天然气水合物储层渗透率研究进展

天然气水合物是清洁、高效、储量巨大的未来最具潜力资源之一,而储层的渗透率是影响水合物资源开采时产气效率的重要参数。目前,国内外对天然气水合物储层的渗透率进行了大量的研究并取得一定进展,本文从数值模拟、储层现场探井、实验研究等方面全面回溯,分析总结了孔隙度、饱和度、应力应变情况等对储层渗透率的影响,讨论目前储层渗透率研究存在人工合成水合物沉积物与自然储层存在差异,不同多孔介质形成的水合物沉积物应力敏感性不同,多相渗流研究不够充分,储层渗透率改造研究不足等问题,对未来的研究方向提出了展望。     

可燃冰生成过程的晶体形态及气体分子传输机理研究

可燃冰是国际公认的21世纪最具应用前景的一种新能源。开采天然气水合物资源对缓解能源危机、解决我国能源短缺、降低CO_2排放等问题有重要的现实意义。国内外对天然气水合物的特性研究主要集中在宏观尺度,对微观尺度的研究较少。通过实验手段从微观尺度研究可燃冰生成过程的晶体形态特征及分子传输机理。研究发现可燃冰在纯水体系和表面活性剂溶液中的结晶特征存在明显的差异,且在形成过程中甲烷分子先进入水合物的小孔穴,再进入水合物大孔穴,可燃冰在表面活性剂溶液和纯水中形成的均为结构I型气体水合物。研究结果对进一步深入认识天然气水合物的形成和分解特性具有重要的研究价值。     

天然气水合物导热性能研究现状

天然气水合物导热系数的研究对于模拟自然界天然气水合物的成藏和天然气水合物勘探、开采具有重要意义。本文介绍了获取天然气水合物导热系数的实验测试和模拟计算方法,分析了气体水合物导热特性、导热机理以及水合物复合体系导热。总结了水合物导热规律,即外界温压条件和晶穴占有率对水合物的导热产生影响,且水合物的导热具有相似的温度压力依赖关系,并呈玻璃体的导热特性。水合物玻璃体导热特性由水合物笼型结构决定,而客体分子的存在强化了水合物导热的玻璃体属性。指出非稳态下天然气水合物导热性能变化研究对分析天然气水合物在常压下的稳定性、确定甲烷水合物等最佳储存温度、从导热角度探讨自保护效应机理等具有重要意义。     

Investigations on the formation kinetics of semiclathrate hydrate of methane in an aqueous solution of tetra-n-butyl ammonium bromide and sodium dodecyl sulfate in porous media

Natural gas hydrate is considered to be an attractive sustainable energy resource for the world. Hydrate as a technology can be of immense importance for various industrial processes, such as multicomponent natural gas separation, gas storage and transportation, and carbon dioxide capture from flue gases and sequestration. A variety of hydrate additives, which includes promoters (thermodynamics and kinetics) and porous media, are being researched to improve the hydrate formation kinetics. However, studies involving the combinations of these are rare in the open literature. In this work, the formation kinetics of methane hydrate/semiclathrate hydrate using tetra-n-butyl ammonium bromide (TBAB) and sodium dodecyl sulfate (SDS) aqueous solutions at various concentrations in a porous medium containing silica sand at initial hydrate formation pressures (7.5 and 5.5 MPa) and temperatures (273.65 and 276.15 K) have been investigated. All the experiments were conducted using 75% water saturation. Various kinetics parameters, such as gas uptake, gas-to-hydrate conversion, and induction time, have been reported. It was found that the combination of TBAB+ SDS showed favorable hydrate formation kinetics in porous media than the TBAB system. This work provides information for further studies involving semiclathrate hydrate applications for various industrial processes.     

Enhancement of methane hydrate formation using a mixture of tetrahydrofuran and oxidized multi‐wall carbon nanotubes

Methane hydrate is a kind of gas hydrate formed by physical binding between water molecules and methane gas, which is captured in the cavities of water molecules under a specific temperature and pressure. Pure methane hydrate of 1 m³ can be decomposed into methane gas of 172 m³ and water of 0.8 m³ at standard conditions. Methane hydrate has many practical applications such as separation processes, natural gas storage transportation, and carbon dioxide sequestration. For the industrial utilization of this substance, it is essential to find a rapid method of manufacturing it. This work studies the formation of methane hydrates by using tetrahydrofuran (THF) and oxidized carbon nanotubes (OMWCNTs) by testing different fluid mixtures of THF and carbon nanotubes. The results show that when the mixed fluid contained THF, the OMWCNTs showed the gas consumption 5.2 times that of distilled water at 3.4 K subcooling. Also, THF's effects as a thermodynamic phase equilibrium promoter were preserved when it was used with OMWCNTs. Therefore, it can be expected that when OMWCNTs are used with an aqueous mixture of THF, both the favorable phase equilibrium of THF and the high gas consumption of the carbon nanotubes can be obtained. Copyright © 2013 John Wiley & Sons, Ltd.     

含水合物沉积物的渗透率实验研究

天然气水合物储层的渗透率是影响水合物开采时气、水运移的关键,也是水合物开采潜力评价、资源评价、开采工艺选择等需要了解的关键参数.目前,国内外学者对天然气水合物储层的渗透率进行了一定的研究并有了初步认识.但是,对于围压、轴向压力、水合物饱和度、赋存模式等对水合物沉积物渗透率的影响机制和机理还不清楚.本文在自主设计的水合物...     

An experimental investigation into the effects of zeolites on the formation of methane hydrates

Methane hydrate is an ice‐like nonstoichiometric compound that forms when methane reacts with water at high pressures and low temperatures. It has a lot of practical applications such as separation processes, natural gas storage transportation, and carbon dioxide sequestration. Especially, the industrial use of hydrates requires large amounts of gas to be formed quickly into hydrates. Porous media significantly influence the rate of hydrate formation by reducing the chemical barrier, where zeolites are microporous minerals. This paper deals with natural and synthetic (5A and 13A) zeolites for hydrate formation and gas storage capacity. The results show that methane hydrates are formed much faster in the three zeolite solutions tested compared with their formation in distilled water at low subcooling temperatures (<7 K). It was also observed that the gas consumption was the greatest in the 0.01 wt.% zeolite 13X solution of distilled water. Its gas consumption was 5.1 times that of distilled water at 0.5 K subcooling. Zeolite 13X demonstrated its effectiveness in enhancing and expediting methane hydrate formation. Copyright © 2014 John Wiley & Sons, Ltd.     

Formation enhancement of methane hydrate for natural gas transport and storage

Methane hydrate is considered an excellent way of transporting and storing natural gas in large quantities. However, when methane hydrate is formed artificially, water/gas ratio is relatively low due to a slow reaction rate between water and methane gas. The major objective of this study is to investigate the mechanics of methane hydrate formation and to explore possible means for rapid production of hydrates and increasing its water/gas ratio. It is found that methane hydrate could be formed rapidly during pressurization if the subcooling is maintained at 8 K or above. In addition, water injection appears to be more effective in hydrate formation compared to gas injection or using a magnetic stirrer. It also gives higher water/gas ratios of 3–4 times for the methane hydrate through a nozzle at the same level of subcooling temperature, when compared to gas injection cases.     

多孔介质中甲烷水合物的微观分布对电阻率的影响

电阻率测井技术是天然气水合物储层资源量估算的重要手段,明确储层电阻率与水合物在沉积物孔隙中微观分布的关系对准确估算水合物饱和度有重要意义。使用自主研发的天然气水合物计算机断层扫描（CT）技术-电阻率测量装置,开展多孔介质中甲烷水合物生成实验,同时进行CT观测与电阻率测试,得到了反应过程中扫描图像和电阻率数据,讨论了孔隙中水合物在不同微观分布模式下电阻率与水合物饱和度的关系。结果表明：水合物饱和度低于10.50%时,水合物以接触分布模式为主,与水合物对孔隙的填充效应相比,排盐效应更加显著,电阻率随水合物饱和度增大略有下降;水合物饱和度为10.50% ~ 22.34%时,水合物为悬浮与接触共存分布模式,悬浮分布模式下的水合物对孔隙水连通截面的阻塞作用较大,电阻率随水合物饱和度的增大急剧升高;水合物饱和度为22.34% ~ 27.50%时,水合物仍然为悬浮与接触共存分布模式,在大部分孔隙已被堵塞的情况下水合物的填充作用对电阻率影响较小,电阻率随水合物饱和度增大而升高的趋势逐渐变缓。可见,电阻率响应特性在不同的水合物饱和度范围下明显不同,与水合物的微观分布有关。     

Efficient promotion of methane hydrate formation and elimination of foam generation using fluorinated surfactants

Methane hydrate preparation is an effective method to store and transport methane. In promoters to facilitate methane hydrate formation, homogeneous surfactant solutions, sodium dodecyl sulfate (SDS) in particular, are more favorable than heterogeneous particles, thanks to their faster reaction rate, more storage capacity, and higher stability. Foaming, however, could not be avoided during hydrate dissociation with the presence of SDS. This paper investigated the ability of five fluorinated surfactants: potassium perfluorobutane sulfonate (PBS), potassium perfluorohexyl sulfonate (PHS), potassium perfluorooctane sulfonate (POS), ammonium perfluorooctane sulfonate (AOS), and tetraethylammonium perfluorooctyl sulfonate (TOS) to promote methane hydrate formation. It was found that both PBS and PHS achieve a storage capacity of 150 (V/V, the volume of methane that can be stored by one volume of water) within 30 min, more than that of SDS. Cationic ions and the carbon chain length were then discussed on their effects during the formation. It was concluded that PBS, PHS, and POS produced no foam during hydrate dissociation, making them promising promoters in large-scale application.