杭州地铁储气砂土的渗气性试验研究

Experimental research on gas permeability of shallow gassy sand in Hangzhou Metro Project

浅层气地质灾害对工程的影响日益受到重视,认清储气土层的气渗透特性是采取积极有效工程措施防治灾害影响的基础。以杭州地铁所遇的储气砂为研究对象,利用自制的渗气性量测装置对其进行了系统的试验研究。结果表明:地铁工程所遇的浅层气储气砂层属渗透性极好储层,渗透率达2960×10-3μm2;砂土中气渗透规律符合达西定律;饱和度较低时,含水率的增加对砂土的渗气性影响很小;随着饱和度的增加,气渗透性逐渐减弱,在饱和度大于80%后,渗气系数急剧减小直至完全不透气;饱和度的变化相对于干密度对储气砂土的渗气性影响更为显著。

More attentions are paid to effects of geological disaster of shallow gas on engineering construction. Recognizing the characteristics of gas permeability in reservoirs is the basis of taking effective measures to control the hazards. A homemade device to measure gas permeability is used to study the gassy sand encountered in Hangzhou Metro Project. Results show that the shallow gassy sand has excellent permeability, and its permeability can reach 2 960×10^-3μm^-2. The Darcy law can be used to describe gas permeability law in sand. The increasing water content of gassy sand has little effects on its permeability in lower saturation degree. With the increase of saturation, gas permeability gradually weakens; and gas permeability coefficient sharply reduces until completely tight when the saturation degree is more than 80 %. Comparing with the dry density, influence ofthe saturation degree on gas permeability of shallow gassy sand is more significant.