Experimental studies on the occurrence, formation, and dissociation of methane hydrates.

在该项目的第一年，实验仪器被设计、制造并安装在实验室中。首席调查员参加了ODP164次巡航，从大西洋布雷克里奇地区的深海沉积物中回收天然气水合物。因此，大部分实验和分析数据都是在第二年获得的。1.在海平面以下200-450米的沉积物中观察到了布莱克岭的海相天然气水合物。下限很容易由沉积物的温度和压力解释，但上限可能受到该深度矿物学、岩性和物性的剧烈变化的控制。2.分析了甲烷水合物与周围间隙水之间的氧同位素分馏为3-4permil。在pH为3.2-3.3的纯水和pH为3.1和5.2的CH3CO2Na-CH3CO2H缓冲溶液中合成了CO2水合物。缓冲溶液中醋酸和乙酸根的总浓度在0.2M~1M之间。结果表明，pH值的变化对CO2水合物的平衡条件影响最小。平衡条件主要受醋酸根和醋酸根的总浓度控制，Na+阳离子的作用最小。总浓度还控制着在pH缓冲溶液中二氧化碳水合物形成的诱导时间。CO2气体在溶液中的溶解度变化可能是由pH变化引起的，是控制诱导时间的另一个因素。

For the first year of this project, experimental apparatus was designed, manufacutured and installed in the laboratory. Head investigator participated in ODP Led 164 cruise to recover natural gas hydrates from deep sea sediments in the area of Blake Ridge, Atlantic. Therefore, most of experimental and analytical data were obtained for the second year.1, Marine gas hydrates of blake Ridge were observed to occur in sediments between 200 and 450 meters below sealevel. The lower limit is easily explained interms of temperature and pressure of the sediments, but the upper limit is likely to be controled by drastic changes in mineralogy, lithology, and physical roperties at that depth.2, Oxygen isotopic fractionation between methane hydrates and ambient interstitial water was analyzed to be 3-4 permil. These values are similar to the fractionation between ice and water.3, CO_2 hydrates were synthesized in pure water with pH of 3.2-3.3, and in CH3CO2Na-CH3CO2H buffer solutions with pH of 3.1 and 5.2. Total concentration of acetic acid and acetate anion of the buffer solutions range between 0.2M AND 1M.The results imply that change of pH value has minimum influence on the equilibrium condition of CO_2 hydrate. The equilibrium condition are mainly controlled by the total concentration of acetic acid and acetate anion, and Na+ cation plays a minimum role. The total concentration also controls the induction time for the formation of CO_2 hydrate in the pH buffer solutions. The solubility change of CO_2 gas in solutions, which is possibly caused by the pH variation, is another factor controlling the induction time.