天然气水合物沉积层渗流特性的模拟

天然气水合物开采过程中水合物饱和度的变化会引起储层渗透率的相应变化,对开采过程造成影响。为研究天然气水合物对多孔介质渗流特性的影响,本文基于孔隙网络模型模拟研究了水合物生成于壁面与中心两种方式下,多孔介质渗流特性变化,并与相关模型进行比较。结果表明,水合物生成于中心时绝对渗透率小于生成于壁面时;水合物饱和度相同时多孔介质孔径越大,渗透率越大;水合物生成于中心时两相相对渗透率等渗点小于生成于壁面时;当水合物饱和度变化时两相相对渗透率几乎不变。说明了储层渗透率与水合物饱和度之间有相对应的关系。     

干水固化甲烷过程及反应特性研究

利用天然气水合物合成实验系统,采用5%纳米SiO2与纯净水配制的干水和纯甲烷为原料,获得了水合物生成过程中温度、压力、反应速率以及最终的储气密度之间的关系。通过以温度和压力值作为变量进行实验结果表明：在高压条件下,反应温度接近0℃,反应的速率较快,生成的水合物中甲烷含量也较高。在低温条件下,压力接近8 MPa时,干水固化甲烷效果较好。     

南海天然气水合物沉积物样本重塑研究

天然气水合物是一种理想的替代能源.目前,对天然气水合物生成的研究,大多以玻璃砂、石英砂等为多孔介质,而很少应用实际的水合物储层沉积物进行实验,本文应用未保压的我国南海天然气水合物沉积物进行水合物生成实验,研究不同孔隙度、注入气体量及初始水饱和度对天然气水合物生成的影响,实验结果显示:注入气体量对生成天然气水合物饱和度影...     

低温常压条件下水合物法储存甲烷的实验研究

利用水合物法实现对天然气的工业储运,需要提高水合物的储气量并解决水合物的分解速度问题。为此,文章研究了在十二烷基硫酸钠（SDS）体系中,甲烷水合物的储气量和在冰点以下的常压分解规律。研究发现,SDS浓度为650 mg/L时甲烷水合物储气量达到最高值,约为170 V/V。分解温度为268.2~272.2 K区域内,甲烷水合物的分解速率随温度的降低而降低;在268.2 K时,甲烷水合物分解速率最低。     

甲烷水合物生成和分解的实验研究

利用水合物法实现对天然气的工业储运,需要提高水合物的储气量并解决水合物的分解速度问题。为此,文章研究了在十二烷基硫酸钠(SDS)体系中,甲烷水合物的储气量和在冰点以下的常压分解规律。研究发现,SDS浓度为650 mg/L时甲烷水合物储气量达到最高值,约为170 V/V。分解温度为268.2~272.2 K区域内,甲烷水合物的分解速率随温度的降低而降低;在268.2 K时,甲烷水合物分解速率最低。     

不同饱和度的天然气水合物降压分解实验

天然气水合物作为一种新能源已得到世界各国的关注,降压是水合物藏的一种有效开采方式。采用自制的天然气水合物开采模拟实验装置,在多孔介质中生成不同饱和度的天然气水合物,之后进行缓慢降压开采实验。结果表明:降压开采可分为自由气产出、水合物降压分解产气和最后降压产出已分解气三个阶段。在降压分解阶段,当水合物饱和度从16%增加到48%时,平均产气速率先增加后减小,说明水合物饱和度对降压分解产气速率的影响是非线性的。降压分解时,水合物饱和度越大,温度下降幅度越大。实验研究范围内,中等饱和度(32%)的水合物藏降压分解产气速率比较大,降压开采效果较好。     

不同饱和度的天然气水合物降压分解实验

天然气水合物作为一种新能源已得到世界各国的关注,降压是水合物藏的一种有效开采方式。采用自制的天然气水合物开采模拟实验装置,在多孔介质中生成不同饱和度的天然气水合物,之后进行缓慢降压开采实验。结果表明：降压开采可分为自由气产出、水合物降压分解产气和最后降压产出已分解气三个阶段。在降压分解阶段,当水合物饱和度从16%增加到48%时,平均产气速率先增加后减小,说明水合物饱和度对降压分解产气速率的影响是非线性的。降压分解时,水合物饱和度越大,温度下降幅度越大。实验研究范围内,中等饱和度（32%）的水合物藏降压分解产气速率比较大,降压开采效果较好。     

撞击流反应器内快速生成甲烷水合物

为了快速制备甲烷水合物以利于天然气水合物法储运,在自行搭建的液相连续撞击流反应器内考察了纯水和纯水+十二烷基硫酸钠(SDS)2种体系中撞击强度、反应器内温度、初始压力对甲烷水合物快速生成的影响.实验结果表明:2种体系内撞击强度的增加可明显加快甲烷水合物的生成,在撞击强度为0.38、反应的前30 min,水合速率达到最大...     

热力法开采天然气水合物的模拟实验研究

在天然气水合物一维开采模拟系统上进行了模拟热力法开采天然气水合物的实验研究. 使用甲烷气体与NaCl溶液在一定温度和压力条件下形成水合物. 通过以不同速率注入不同温度的热水,研究了热力法开采水合物过程中含水合物沉积物的温度分布以及甲烷气体、水生产规律. 结果表明,在整个分解过程中,气体生产速率随时间增加而增加,直到达到最大值后开始下降,而水生产的速率几乎保持恒定. 通过对实验结果的能量分析表明,热力开采的能量效率在0.38~2.59之间. 注入热水的温度、速率以及沉积物中水合物的饱和度对热力法开采水合物的能量效率有重要影响.     

甲烷水合物生成分解的实验研究

海底存在着大量可燃冰,1 m3可燃冰能够储存160 m3的天然气。因此,可燃冰的开采与利用可燃冰储存与运输天然气具有重要意义。在改变搅拌、过冷度及低浓度动力学抑制剂的条件下,对甲烷水合物生成量与生成速率进行了实验研究。将甲烷水合物进行升温分解,分析水合物分解时的压力变化情况。结果表明:搅拌对甲烷水合物生成的促进效果最好,其次是过冷度,最后是超低浓度动力学抑制剂;水合物生成的传质过程最终被阻碍,采取将水与天然气的上下位置交换的方法,可以生成更多水合物。水合物升温可以得到相平衡曲线;改变初始时刻压力,可以得到不同温度区间的相平衡曲线;降低水合物分解时的升温速度,可以得到更长温度区间的相平衡曲线。     

量热法多孔沉积物内CH4水合物生成过程中的放热行为

掌握天然气水合物在多孔沉积物生成过程中的放热规律对于天然气水合物的资源开发和了解水合物的成藏规律都具有重要意义。本研究通过高压微量热仪考察了石英砂粒径、初始含水率、温度及含盐条件对CH₄水合物在多孔沉积物内生成过程中放热行为的影响。实验结果表明,随着石英砂粒径的减小,水合物生成的放热速率随之增加。随着初始含水率的降低,水合物的放热峰明显增大,但在实验考察时间内,最终的累积放热量和含水率并没有呈现出明显的相关性。当温度在263.15K时,CH₄水合物生成过程中不存在明显的放热。对于在3.35% NaCl盐溶液体系中进行的甲烷水合物生长放热实验,发现其放热规律与在纯水体系下的放热规律具有较高的一致性,但其总体放热速率和累积放热量较纯水体系更低。实验结果呈现了良好的规律性,对进一步开发量热仪在水合物生成动力学方面的应用具有一定的参考价值。     

Catalysis of Gas Hydrates by Biosurfactants in Seawater‐Saturated Sand/Clay

Biosurfactants catalyzed natural gas hydrate formation in sand/clay packs saturated with seawater. Representative samples from the five possible biosurfactant classifications enhanced hydrate formation rate and decreased hydrate induction time. Biosurfactants increased rates 96% to 288% and decreased induction times 20% to 71% relative to the control. Micellar‐forming rhamnolipid reached a critical micellar concentration at 13 ppm at hydrate‐forming conditions; these micelles migrated readily through a seawater‐saturated sand pack to catalyze hydrate formation in another zone. The type of biosurfactant, in conjunction with specific porous media, help determine massive, dispersed, nodular, or stratified forms of hydrates. Results suggested that minimal microbial activity in ocean‐floor sands can greatly influence gas hydrate formation.     

初始压力对冰冻石英砂中CO2水合物生成特性的影响

利用冰冻石英砂模拟冻土水合物的赋存条件，研究了压力对二氧化碳水合物生成特性的影响，在300 mL高压水合物反应釜中于271 K下进行了多组CO2液化压力以上及以下的霰状冰粉包裹的石英砂中水合物生成实验。结果表明，充入的CO2未液化时，初始压力越大，水合反应速率越快，压力越早达稳定状态；充入压力达液化压力后，注入的CO2越多，水合反应速率越快。压力作为水合反应的驱动力，压力越高水合物生成越多，冰的最终转化率越高。采用CO2置换冻土区中甲烷水合物时，控制压力低于液化压力或注入过量的CO2，置换效果更好。     

DSC measurements and modelling of the kinetics of methane hydrate formation in water-in-oil emulsion

The kinetics of formation of clathrate hydrates of methane was investigated in a water-in-oil emulsion using high-pressure differential scanning calorimetry in the range 10-40 MPa, at various temperatures. At high driving force, the heat peak related to the formation of hydrates has a regular and symmetric shape, and its height and width depend on the gas pressure and sub cooling degree. At near equilibrium conditions, hydrate formation is delayed by more than 1 h, but is still clearly observable. A model based on crystal growth theory, coupled with a normal distribution of induction times to take into account the germination in a population of micro-sized droplets, is proposed to represent the hydrate formation rate versus time in the particular case of water-in-oil emulsions. It uses four parameters which appear strongly correlated to the experimental conditions: the growth rate constant, the over saturation of gas in the water phase, the average and standard deviation of the induction time distribution.     

Experimental investigation of hydrate formation behaviour of a natural gas bubble in a simulated deep sea environment

A vertically flowing, closed circuit, high pressure water tunnel was designed and constructed for holding individual gas bubbles stationary against an opposing flow for detailed observations. Hydrate formation behavior of natural gas bubbles was studied at constant pressure as well as under conditions of controlled decompression designed to simulate buoyant rise of the bubble.A bubble of simulated natural gas suspended in 3°C salt water formed hydrates when the pressure was 4826 kPa or higher. The simulated decompression accompanying buoyant rise had very little effect on hydrate formation behavior of a bubble starting from a pressure of 5516 kPa or above. At lower starting pressures, a slight increase in the reaction rate was detected in the initial stages of a run. The conversion of the simulated natural gas to hydrates was complete in runs starting from a pressure of 4826 kPa or above.     

Evaluation on the natural gas hydrate formation process

Gas hydrates have endowed with great potential in gas storage, and rapid formation of gas hydrates is critical to use this novel technology. This work evaluated the natural gas hydrate formation process, which was compared from six parameters, including conversion of water to hydrate, storage capacity, the rate of hydrate formation, space velocity (SV) of hydrate reaction, energy consumption and hydrate removal. The literature was selected by analyzing and comparing these six parameters mentioned above, meanwhile placing emphasis on the three parameters of storage capacity, the rate of hydrate formation and space velocity of hydrate reaction. Through analysis and comparison, four conclusions could be obtained as follows. Firstly, the overall performance of the stirring process and the spraying process were better than other processes after analyzing the six parameters. Secondly, the additive types, the reactor structure and the reactor size had influence on the natural gas hydrate formation process. Thirdly, the energy consumption via reciprocating impact in the hydrate formation process was higher than that via stirring, spraying and static higee. Finally, it was one key for hydrate removal to realize the hydrate industrial production.     

孔隙尺寸、盐度和气体组分对水合物相平衡的影响(英文)

An experimental device was set up to study the hydrate formation conditions. Effects of pore size, salinity, and gas composition on the formation and dissociation of hydrates were investigated. The result indicates that the induction time for the formation of hydrates in porous media is shorter than that in pure water. The decrease in pore size, by decreasing the size of glass beads, increases the equilibrium pressure when the salinity and temperature are kept constant. In addition, higher salinity causes higher equilibrium pressure when the pore size and temperature are kept constant. It is found that the effects of pore size and salinity on the hydrate equilibrium are quite different. At lower methane concentration, the hydrate equilibrium is achieved at lower pressure and higher temperature.     

Effect of multi-walled carbon nanotubes on methane hydrate formation

1 m³ of methane hydrate can be decomposed into a maximum of 216 m³ of methane gas under standard conditions. If these characteristics of hydrates are utilized in the opposite sense, natural gas can be fixed into water in the form of a hydrate solid. Therefore, the use of hydrates is considered to be a great way to transport and store natural gas in large quantities. However, when methane hydrate is formed artificially, the amount of gas that is consumed is relatively low, due to the slow reaction rate between water and methane gas. Therefore, for practical purposes in the application, the present investigation focuses on increasing the rate of formation of the hydrate and the amount of gas consumed by adding multi-walled carbon nanotubes (MWCNTs) to pure water. The results show that when 0.004 wt% of multi-walled carbon nanotubes was added to pure water, the amount of gas consumed was about 300% higher than that in pure water and the hydrate formation time decreased at a low subcooling temperature.     

冰点以下多孔介质中气体水合物的生成动力学研究进展

青藏高原冻土区储存着大量的天然气水合物资源,CO₂置换开采冻土区的天然气水合物可实现天然气水合物的安全开采和温室气体CO₂的地层封存。冰点以下多孔介质中气体水合物的生成动力学,是冻土区天然气水合物置换开采研究领域的难点和热点问题。本文全面综述了冰点以下多孔介质中气体水合物的生成动力学研究进展,讨论了不同体系冰点以下多孔介质中气体水合物的形成机理及其生成特性;详述了冰生成水合物机理及其冰粉/多孔介质体系中气体水合物的生成特性,分析了冰点以下多孔介质中气体水合物生成动力学研究尚待完善和改进的地方。最后本文指出冰点以下多孔介质中水合物的生成过程是由传热、传质等多种因素所控制,揭示不同过程的主导因素及其影响规律是今后研究的重点方向。目前对冰点以下多孔介质中水合物的生成特性及机理的认识尚未成熟,仍需深入研究。     

X射线衍射分析聚乙烯吡咯烷酮对水合物分解过程的影响

深水油气资源的勘探开发以及开采过程中的环保要求,使得天然气水合物动力学抑制剂使用不可避免,含动力学抑制剂的分解研究对水合物生成后的解堵具有重要的指导意义。本文在高压反应釜内采用甲烷和丙烷混合气,合成天然气水合物,并用X射线粉晶衍射仪分析了含动力学抑制剂聚乙烯吡咯烷酮的水合物分解过程。结果显示甲烷和丙烷气体会形成SⅡ型水合物,但伴随有SⅠ型甲烷水合物的生成;添加动力学抑制剂后,水合物的分解速率变慢,在-60℃,添加0.5%的聚乙烯吡咯烷酮后,分解起始的20 min内,无抑制剂体系水合物分解可达69%,而在含抑制剂体系分解约18%;SⅡ型甲烷丙烷混合气水合物分解过程中晶胞各晶面分解速率相同,没有偏好性,水合物笼作为一个整体分解,添加抑制剂不改变这种分解方式,仍以整体分解。