中文摘要：

天然气水合物顶界的确定对于其资源评价十分重要,但目前还没有很好的方法来确定.本文利用在甲烷-硫酸根（SMI）界面硫酸根与甲烷所消耗的量相等和水-天然气水合物二相体系甲烷溶解度模型,建立了水合物顶界埋深计算的数学模型,并考虑硫酸根氧化有机质和微生物原位甲烷生成的影响.计算的ODP1245和IODP1327站位水合物顶界埋深分别为53mbsf和83mbsf,与钻探获得的水合物顶界埋深相吻合.

英文摘要：

A major problem in evaluation of gas hydrate resources is lack of a reliable technique to constrain the top occurrence of gas hydrates.We have developed a numerical model of the top occurrence of gas hydrates based on that the depleted quantity of sulfate diffusion downward equals to that of methane flux upward at sulfate-methane interface（SMI）and the methane solubility in the water-hydrate system,using steady state and analytical expressions.In situ methane production and sulfate depletion associated with the oxidation of sedimentary organic matter were considered in the model.We applied this model to ODP site 1245and IODP site1327,and calculated the top of gas hydrate occurrence at these two sites,yielding 53mbsf,83mbsf,respectively,which are consistent with the top depth estimated by drilling.