中文摘要：

杭州湾地区晚第四纪浅层生物气藏盖层存在孔隙水压力封闭和烃浓度封闭机理，但其是否存在物性封闭机理目前尚存在较大争议。研究区浅层生物气藏盖层埋藏浅、时代新、结构松散，对其物性封闭能力的评价不能直接套用深部成岩盖层的评价参数和方法。通过变水头渗透实验测定盖层和储层样品渗透率数值，以渗透率作为评价浅层生物气盖层物性封闭能力的参数，对研究区浅层生物气藏盖层的物性封闭特征及其影响因素进行了详细研究。结果表明盖层渗透率数值比储层小3个数量级，具有较强的物性封闭能力，有利于浅层生物气藏的保存。研究区浅层生物气盖层物性封闭能力的影响因素包括黏土含量及黏土矿物成分、含水饱和度和盖层厚度，黏土含量及黏土矿物成分对盖层物性封闭能力起决定性作用，较高的含水饱和度促进了盖层物性封闭能力的增强，盖层厚度对物性封闭能力起到了极为重要的补偿作用。

英文摘要：

Pore-water pressure sealing mechanism and hydrocarbon concentration sealing mechanism have been proved to exist in the shallow biogenic gas cap beds of Late Quaternary in Hangzhou Bay Area. At present, the dispute over the existance of capillary sealing mechanism still exists. The cap beds of shallow biogenic gas res- ervoirs of Late Quaternary in Hangzhou Bay Area are shallow buried, with the characteristics of new age and loose construction. Therefore, we can＇ t apply mechanically the evaluation parameters and methods of deep diagenetie cap beds to evaluating capillary sealing mechanism in the study area. In this study, we measure the permeabilities of samples from cap beds and the reservoirs by falling-head permeability test, and we set the permeability as the e- valuation parameter on the capillary sealing capacity of the shallow biogenic gas cap beds in order to study the char- acteristics and influencing factors of capillary sealing mechanism in shallow biogenic gas cap beds of the study area in detail. The difference of three orders of magnitude in permeability measured by falling-head permeability test be- tween cap beds and reservoirs shows that there has been strong capillary sealing ability in cap beds, which leads to the formation of shallow biogenic gas pools. The capillary sealing mechanism of shallow biogenic cap beds are main- ly influenced by the amount of clay and clay mineral, water saturation and thickness of cap beds. The amount of clay and clay mineral play a decisive role in the capillary sealing capacity and the high water saturation enhances the capacity of capillary sealing. In addition, the thickness of cap beds plays a compensation role on the capacity of capillary sealing.