【作者】 刘昌岭；

【导师】 业渝光；

【作者基本信息】 中国海洋大学 ， 海洋地质， 2005， 博士

【摘要】 海洋天然气水合物作为一种能量资源已受到各国政府的高度重视,如何准确地探测和估算海底水合物的资源量,是海洋天然气水合物研究的重要问题。本文针对这些问题,利用本实验室开发的低温高压实验技术,探讨了天然气水合物模拟实验的几种探测方法,包括声学法、电阻法和时域反射（TDR）法。本文研制了一套简易的天然气水合物制备装置,重点研究了各种条件下生成的甲烷水合物的含气量,以及海洋天然气水合物生成过程中引起的周围环境元素地球化学异常。主要研究内容如下: 1.简述了海洋天然气水合物的组成、结构、性质、形成的基本条件、分布特点、资源量以及海底水合物的各种探测技术,探讨了目前关于海洋天然气水合物模拟实验研究的现状及其发展趋势,据此提出了本文研究目的,确定了研究内容。 2.在球形高压釜内进行了甲烷水合物的相平衡条件实验。使用光通过率来确定天然气水合物的合成与分解,提高了探测灵敏度。实验测得的水合物相平衡曲线与国内外经典的相图十分吻合,实验结果令人满意。使用温压法探测了沉积物中甲烷水合物的生成和分解过程,得出粒径为0.28-0.9mm的天然砂中纯水-甲烷体系的相平衡条件与不含沉积物的纯水-甲烷体系的相平衡条件基本一致,说明粗颗粒的沉积物对相平衡条件影响不大。 3.水合物超声探测实验表明,在纯水中,声速对体系中天然气水合物的生成/分解过程不敏感;在松散沉积物中,声速的变化灵敏地反映了体系内水合物的生成和分解的变化,但声波幅度的变化不明显。在沉积物岩芯中,纵波和横波速度随着孔隙度的减小而增大,声速灵敏地反应了沉积物岩芯中天然气水合物饱和度的变化。 4.水合物模拟实验的初步结果表明,TDR探测技术和电阻法探测技术可灵敏地探测到反应体系内水合物的生成/分解过程。TDR技术可以灵敏地测出岩芯中的含水量,即可以灵敏地探测岩芯中水合物的饱和度。而电阻法探测技术对反应体系内CO₂水合物的成核-微晶过程十分灵敏,在水合物成核机理的研究中将有十分重要的作用。 5.研制了一套简易的、容易开启的天然气水合物实验装置,采用了高频振动技术,已获得了国家专利。该装置的高压釜内设有内筒,合成的水合物很容易取出,可以直接测定其储气量;也可以将反应后的水合物与水分离,测定其离子更多还原

【Abstract】 Marine gas hydrate is a potential important energy resource attracting the attentions worldwide. Therefore, how to correctly explore and evaluate the resource of marine gas hydrate is an urgent and significant problem to be solved. This paper aims to solve such problems related to marine hydrate research. Based on the low-temperature high-pressure techniques developed in our laboratory, several detection methods are discussed, including acoustic method, impendence method and Time-Domain -Reflector (TDR) method. A simple apparatus is specially developed to form gas hydrate, in basis of this, the gas content in hydrate formed in different conditions and the elemental geochemical anomaly in ambient environment during hydrate formation is studied in this paper. The main ideas are:1. Compositions, structures, properties, formation conditions, distribution feathers and marine gas hydrate resources as well as several detection techniques for marine gas hydrate are discussed concisely. The present situation and research tendency of experimental simulated study on marine gas hydrate is also introduced. Based on these, the aim and content of this study is presented.2. The phase equilibrium conditions of methane hydrate is studied in a spherical high-pressure vessel. The detection sensitivity is improved when the transmittance light strength ratio is used to detect the formation/dissociation of gas hydrate. The stability conditions of methane hydrate in pure water-methane system measured in this paper agree well with the classical phase equilibrium curves from literatures. In sediments, the formation/ dissociation process of gas hydrate is detected by changes of temperature and pressure in the vessel, the results show that the P-T conditions of methane hydrate in natural sand (0.28-0.9mm) is almost the same as those in the pure water-methane hydrate system, suggesting little effect on the stability conditions of gas hydrate by coarse sediments.3. Ultrasonic detection technique indicates that the velocity is not sensitive to the formation/decomposition of hydrate in a pure-water system. In loose sediments, sonic velocity changes sensitively during formation/dissociation processes of hydrate in the system, whereas the variation of wave amplitude is not significant in this case. In the sediment core, the velocity and amplitude of the compressional and shear waves increase as the porosity decrease, the sonic velocity sensitively reflects the variation of hydrate saturation in the marine sediment core.4. The preliminary results show that the TDR detection technique and the impedance detection method can detect the process of formation/dissociation of hydrate in laboratory. The TDR detection technique can determine water contents insediment core sensitively, that is to say that this method is sensitive enough to detect the hydrate saturation in the core. The impedance detection method is sensitive to the nucleation and micro-crystalline process of CO2 hydrate in the vessel, which is supposed to be useful in studying the hydrate nucleic mechanism in the future.5. Another simple experimental apparatus is designed to be easy to open, which uses the high-frequency vibrator and gains the national patent. There is an inner chamber in the high-pressure vessel, so that the synthesized hydrate can be taken out conveniently for direct gas storage determination in the hydrates, and the residual water can also be separated from the hydrate to determinate the ion concentrations. This apparatus is the experimental basis for gas storage determination and geochemical anomaly research for marine gas hydrate.6. Experimental study on gas storage in methane hydrate is carried out in the above apparatus. A new setup and technique is specially devised to measure gas volume during hydrates decomposing in a vacuum system. The results show that the determined E values are different in different conditions such as pressure, temperature, gas content in water and time, indicating gas storage in hydrate vary with its formation conditions. Compared with traditional gravimetric method, the volumetric method has a lot of advantages. It is easy to work and generally not affected by environmental conditions such as temperature and humidity. It is believed that this method is more useful to determine gas storage of natural gas hydrate in sediments, and will be widely used in the assessment of gas hydrate resources and the transport of natural gas.7. The formation process of marine gas hydrates is simulated in laboratory, and variations of ionic and isotopic concentrations in seawater are studied preliminarily. The results show that the effects of gas hydrate formation on the variations of ionic concentrations are not alike in different experimental conditions. The larger the gas consumption, the higher purity the hydrates, therefore, the salt-exclusion efficiency is stronger, resulting higher ionic concentrations in the residual solution, lower in the112hydrate solutions. The 8 O> 5D values in the solution are determined before and after each experiment, and the obtained isotopic fractionation factors of oxygen and hydrogen in natural seawater system are 1.0034 ~ 1.0063 and 1.018 — 1.036, respectively. SDS is an efficient surfactant, which can not only accelerate gas hydrate formation, but also probably affect the isotopic fractionation of oxygen and hydrogen.更多还原