元坝高含硫气田水合物实验研究

元坝气田天然气为高含硫过成熟干气,在采集输过程中容易形成水合物,而井筒、集输管线属于水合物形成的高发部位,一旦形成将严重影响正常生产。为此,开展元坝气田长兴组水合物生成及抑制剂实验,结果表明：压力小于20MPa下元坝气田长兴组含硫天然气水合物生成温度随压力增加明显,压力高于20MPa时水合物生成温度增加相对平缓。即在低压情况下水合物形成温度对压力的变化越敏感。天然气水合物生成温度随着甲醇和乙二醇在浓度增加逐步降低,压力较低时水合物生成温度较低,说叫甲醇和乙二醇对水合物生成有明显的抑制作用。     

SDS溶液与树脂复配体系下天然气水合物生成分析

使用3种不同极性的大孔吸附树脂与不同质量浓度SDS溶液复配的体系进行天然气水合物生成实验,探究极性作用与毛细作用对天然气水合物生成的影响。结果表明:树脂极性吸附能力能够导致体系压强的变化,极性越强,压降曲线的斜率也就越大,水合物生成速率也就越快。影响水分子迁移方向的主要因素是毛细作用与树脂极性,溶液表面张力越大,体系内产生的毛细作用也就越强,对水分子的驱动也就越强;极性越强,水分子与天然气气体分子越容易在树脂周围聚集,也就越容易生成水合物。天然气水合物在反应釜壁面处产生的毛细作用大于溶液内部颗粒之间的毛细作用和树脂极性作用之和,水分子的迁移主要发生在反应釜壁面处。同时树脂的极性与颗粒间的毛细力共同作用会产生棒状水合物,极性作用越强棒状水合物的生成量也就越多。     

天然气水合物生成条件的测定和计算

利用全透明蓝宝石水合物静力学实验装置，测定了4种塔里木油田天然气在纯水中的水合物生成条件.将Chen-Guo 水合物模型应用于天然气水合物生成条件的计算，实验测定的4种天然气水合物生成条件的计算结果和实验结果符合得很好.     

操作工况对酸性天然气水合物生成动力学的影响分析

水合物的快速生成受诸多因素的影响,操作工况是其主要的影响因素之一。以67.7%CH4+32.3%CO2（摩尔分数）混合气为例模拟酸性天然气,采用自行设计的水合物动力学实验装置,分别对初始压力为3.0 MPa、3.5 MPa、4.2 MPa、5.0 MPa和实验温度分别为1.42 ℃、3.27 ℃、5.48 ℃、7.45 ℃时的水合物生成动力学进行实验研究。定义诱导期、平衡总耗时、生长速率为水合物动力学评价指标,指标通过分析水合物生成过程中的压力及气相组成变化得到,进而综合分析了操作工况对酸性天然气水合物生成动力学的影响。实验结果表明：初始压力越高,实验温度越低,水合物平衡时气相CO2的浓度越低,水合物的生成量和生长速率越大;此外,初始压力对体系诱导期影响不够显著,而操作温度的降低可以明显缩短体系诱导期。     

长输天然气管道水合物生成预测及影响因素分析

在管道输送天然气中,准确预测水合物生成位置及其影响因素分析,对管道安全运行十分重要。为此,基于长输管线温度、压力计算与水合物生成条件预测模型,建立了长输管线水合物生成位置预测程序,并对具体实例进行分析,结果表明,管径越小、输量越大、保温材料导热系数越小、天然气中H2S含量越低、CO2含量越高,水合物生成范围缩小。该程序对长输天然气管道设计、安全管理、天然气脱硫处理提供了技术支持。     

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...     

SDS溶液与APG溶液对天然气水合物生成的协同作用

天然气是一种潜力巨大的清洁能源,但是其工业化生成技术仍面临较大的困难。表面活性剂作为一种工业催化剂能对天然气水合物的生成有着明显的促进作用。为研究不同表面活性剂下天然气水合物生成特点,采用静态条件下天然气水合物的实验方法,对SDS表面活性剂溶液与APG表面活性剂溶液以及他们的混合溶液进行天然气水合物生成实验。结果表明:APG与SDS混合溶液中生成的天然气水合物稳定性介于纯SDS溶液中生成的天然气水合物和纯APG溶液中生成的天然气水合物之间;APG与SDS溶液的协同作用能够明显地改变溶液表面张力,并且3种溶液下水合物生成的动力学数据与3种溶液的表面张力数据有着类似的变化规律。     

水合物在静态脂肪醇聚氧乙烯醚硫酸钠溶液与纯水搅拌条件下生成分析

促进天然气水合物快速大量生成是天然气水合物技术产业化的关键,因此,对其动力学促进方法进行研究是十分必要的。本文在温度为(2±0.1)℃,压力为(6.6±0.1)MPa条件下研究了不同浓度(60~1350mg/L)脂肪醇聚氧乙烯醚硫酸钠(AES)以及不同搅拌转速0~800r/min对水合物生成的影响,对两种方式的促进效果进行了对比,并从水合物生成动力学角度对AES及搅拌的促进机理进行分析。实验结果表明:AES与搅拌都可以促进液相气过饱和,加速单核生长和多核聚结过程,显著缩短诱导期,提高水合物生成速率及气体消耗量,但不同的是在水合物生长阶段搅拌仅能促进气相向液相单向移动,AES能够使气液交叉移动,显著降低了气液传质阻力,增加了成核位置,因此AES比搅拌进一步提高了水合物生成速率及气体消耗量。     

十六烷基三甲基溴化铵促进CO2水合物生成的实验研究

针对CO2水合物自然生成速度慢这一技术难题,利用实验室自制的水合物实验系统,开展了十六烷基三甲基溴化铵(CTAB)体系下CO2水合物生成促进实验研究。考察了CTAB质量分数为200、300、500、700、900 mg/kg下对水合反应体系表面张力及CO2水合物生成特性影响规律,分析了CTAB对CO2水合物生成促进作用机理。实验结果表明,5种浓度下CTAB添加剂均能够有效降低CO2水合物相平衡点,温度越高,生成压力降低幅度越大,在最优用量为300 mg/kg下降幅可达27.7%。水合反应体系的压力越低,CTAB促进CO2水合物生成的诱导时间降低越大,促进效果越明显。该研究对于提高水合物生成速率具有一定的意义。     

油包水乳液体系水合物的形成对多相流动摩阻的影响

水合物浆液输送作为流动安全保障主要措施和天然气新型运输方法之一,其复杂的流动特性引起了学者的广泛关注。以国内首套水合物高压实验环路为依托,基于水合物生成后管路压降明显增加的现象,分析了4.5 MPa压力下,0.4、0.5、0.9、1.1 m/s四个流速下压降变化幅度,对比水合物生成前后体系摩阻系数的变化,定量表示了各个流速下颗粒存在对摩阻系数的影响。实验结果表明,流速越大,颗粒存在对于体系摩阻系数的影响越小;并且通过对比0.4和0.5 m/s的实验结果可知,在水合物浆液流动过程中,不同的流速对应着不同的液固流型,存在临界悬浮流速的概念。     

Thermodynamic consistency test for experimental data of water content of methane

Accurate knowledge of the water content of natural gases is an important factor to estimate the gas hydrate, ice, and condensed water formation conditions. However, the experimental data regarding the water content of gases in equilibrium with the gas hydrate, ice, or liquid water (near gas hydrate or ice formation region) are limited. This is partly because of the fact that concentration of water in the gaseous phase in equilibrium with gas hydrate, ice or liquid water (near gas hydrate or ice formation region) is very low considering that reaching the equilibrium conditions near and inside gas hydrate or ice formation region is time consuming process. The measurement difficulties may consequently result in generating unreliable experimental data. This work aims at performing a thermodynamic consistency test based on area approach to study the reliability of some experimental data reported in the literature on the water content of methane (the main component of natural gases) in equilibrium with the gas hydrate, ice, or liquid water (near gas hydrate or ice formation region). A discussion is made on the studied experimental data according to the performed consistency test. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

STUDY FOR NATURAL GAS HYDRATE CONVERSED FROM ICE

Natural gas hydrates are crystalline clathrate compounds composed of water and gases of small molecular diameters that can be used for storage and transport of natural gas as a novel method. In the paper a series of experiments of aspects and kinetics for hydrate formed from natural gas and ice were carried out on the industrial small scale production apparatus. The experimental results show that formation conditions of hydrate conversed from ice are independent of induction time, and bigger degrees of supersaturation and supercooling improved the driving force and advanced the hydrate formation. Superpressure is also favorable for ice particle conversion to hydrate. In addition, it was found there have an optimal reaction time during hydrate formation.     

石英砂中甲烷溶解运移体系水合物生成与聚集实验分析

建立了可模拟海底天然气水合物形成环境的大型三维成藏实验模拟装置,其主体高压反应釜内径500 mm,高1000 mm。在此基础上,采用填砂模型,进行了甲烷溶解运移体系下甲烷水合物生成与聚集过程的实验模拟分析。实验流程为：甲烷溶解于NaCl溶液中,再泵送进入高压反应釜,在沉积层中渗流并生成甲烷水合物。通过30个电阻率传感器监测甲烷水合物的生成和聚集过程。实验结果表明,甲烷溶解运移体系下甲烷水合物生成之后首先分散在溶液中,当溶液的总甲烷浓度（溶解的甲烷及水合物分散相中的甲烷）达到操作条件下盐溶液体系甲烷饱和溶解度后,甲烷水合物从溶液中析出。电阻率分布实验结果表明,析出甲烷水合物的聚集区域受溶液流动控制。     

Phenomenological diffusion theory of formation of gas hydrate from ice powder

The diffusion theory of the formation of gas hydrate from ice powder is stated. The theory takes into account that a gas hydrate has a pore structure that can change during formation of gas hydrate. The parameters of the theoretical model that are responsible for the kinetics of methane hydrate formation are estimated using a comparison between experimental and calculated data.     

0℃以下含SDS的甲烷水合物生成方式及过程对其分解速率的影响

The dissociation rates of methane hydrates formed with and without the presence of sodium dodecyl sulfate(methane-SDS hydrates),were measured under atmospheric pressure and temperatures below ice point to investigate the influence of the hydrate production conditions and manners upon its dissociation kinetic behavior.The experimental results demonstrated that the dissociation rate of methane hydrate below ice point is strongly dependent on the manners of hydrate formation and processing.The dissociation rate of hydrate formed quiescently was lower than that of hydrate formed with stirring;the dissociation rate of hydrate formed at lower pressure was higher than that of hydrate formed at higher pressure;the compaction of hydrate after its formation lowered its stability,i.e.,increased its dissociation rate.The stability of hydrate could be increased by prolonging the time period for which hydrate was held at formation temperature and pressure before it was cooled down,or by prolonging the time period for which hydrate was held at dissociation temperature and formation pressure before it was depressurized to atmospheric pressure.It was found that the dissociation rate of methane hydrate varied with the temperature(ranging from 245.2 to 272.2 K) anomalously as reported on the dissociation of methane hydrate without the presence of surfactant as kinetic promoter.The dissociation rate at 268 K was found to be the lowest when the manners and conditions at which hydrates were formed and processed were fixed.     

Stability and growth of gas hydrates below the ice–hydrate–gas equilibrium line on the P–T phase diagram

Using a previously developed experimental technique, the behavior of small methane and propane hydrate samples formed from water droplets between 0.25 and 2.5 mm in size has been studied in the pressure–temperature area between the ice–hydrate–gas equilibrium line and the supercooled water–hydrate–gas metastable equilibrium line, where ice is a stable phase. The unusual persistence of the hydrates within the area bounded by these lines and the isotherms at T=253 K for methane hydrate or at T=263 K for propane hydrates was observed. This behavior has not previously been reported. For example, in the experiment carried out at 1.9 MPa and 268 K, the methane hydrates existed in a metastable state (the equilibrium pressure at 268 K is 2.17 MPa) for 2 weeks, then immediately dissociated into liquid supercooled water and gas after the pressure was isothermally decreased slightly below the supercooled water–hydrate–gas metastable equilibrium pressure. It was found that dissociation of metastable hydrate into supercooled water and gas was reversible. The lateral hydrate film growth rates of metastable methane and propane hydrates on the surface of supercooled water at a pressure below the ice–hydrate–gas equilibrium pressure were measured. The temperature range within which supercooled water formed during hydrate dissociation can exist and a role of supercooled water in hydrate self-preservation is discussed.     

Evidence of liquid water formation during methane hydrates dissociation below the ice point

Dissociation of small methane hydrate samples formed from water droplets of size 0.25-2.5 mm has been investigated below the ice melting point in the temperature range of 240-273 K, where the self-preservation effect is observed for bulk hydrates. The experiments included optical microscopy observations combined with P-T measurements of the dissociation conditions for the methane hydrates. For the first time, the formation of supercooled liquid water during the hydrate dissociation was reliably detected in the temperature range of 253-273 K. The formation of the liquid phase was visually observed. The induction time of the ice nucleation for the metastable liquid water depended from the dissociation temperature and a size of water droplets formed during the hydrate dissociation. It was found that in the temperature range of 253-273 K values of the dissociation pressure for the small hydrate samples fall on the extension of the water-hydrate-gas equilibrium curve into the metastable region where supercooled water exist. The average molar enthalpy of 51.7 kJ/mol for the dissociation of the small methane hydrate samples in the temperature range of 253-273 K was calculated using Clausius-Clapeyron equation. This value agrees with the enthalpy of dissociation of bulk methane hydrates into water and gas at temperatures above 273 K.     

On the Applicability of a Quasi-Stationary Solution of the Diffusion Equation for the Hydrate Layer Formed at the Gas–Ice (Water) Interface

The problem of methane hydrate formation when the process is controlled by gas diffusion in the hydrate layer formed at the gas–ice (or water) interface is solved. It is shown that an approximate quasi-stationary solution of the diffusion equation is in good agreement with its numerical solution over a wide range of the solubility of the gas in the hydrate, which is dependent on pressure. It is found that the time for the complete transition of the water (or ice) phase into the hydrate state decreases with an increase in the saturation concentration of the mobile gas in the hydrate. The kinetic equations derived based on a quasi-stationary solution of the diffusion equation, which are relationships for the intensity of hydrate formation in snow-containing (or water-containing) formations during the filtration of hydrate-forming gases, are used to describe the concentration fields of the diffusing gas and the dynamics of hydrate layer growth.     

气体水合物平衡生成条件的测定及预测

建立了一套气体水合物实验测定装置，采用该装置在温度２６２．６－２８５．２Ｋ范围内分别测定了甲烷，二氧化碳和一种合成天然气在纯水、电解质水溶液以甲醇水溶液中水合物的平衡生成压力，共计９个体系，７８个数据点。     

含盐蒙脱石中甲烷水合物的生成/分解特性及离子分布研究

目前,天然气水合物成藏和开采是新能源开发应用的热点,但海域沉积物中天然气水合物的形成/分解特性,及盐离子对水合物稳定性的影响等关键问题亟待解决。利用天然气水合物原位取样技术对甲烷水合物在含盐多孔介质中生成和分解过程进行原位扫描电镜(Scanning Electron Microscopy, SEM)测试和能谱分析(Energy Dispersive Spectrometry, EDS),系统研究了含0.5 mol/L NaCl溶液的蒙脱石中甲烷水合物生成、分解过程中形貌的变化及离子分布特征。研究发现水合物生成和分解过程元素分布发生明显改变,水合物生成的排盐效应使得NaCl在水合物颗粒与颗粒交结处以水合盐离子的形成存在,并且Na+和Cl-在蒙脱石表面分层排布。水合物生成后蒙脱石表面呈独立颗粒状,水合物分解后蒙脱石表面凹陷并形成微小的气体通道,并且水合物分解后蒙脱石的骨架堆积结构发生改变。研究得出水合物成核、生长、分解过程均在特定基元颗粒间是独立进行的,并且生长与分解过程与水合物晶胞结构有关。