Abstract: The permeability of mudstne determines its sealing ability.Mud content,mined composition,grain texture and formation fluid properties are the main factors influencing permeability and sealing ability.The distribution and continuity of mudston are controlled by sedimentary facies.The data of displa.cement pressure,thickness and area distribution have Shawn that mudston of permeability less then 0.003 and and thickness large than 3m may provide an effective sealing for mid-law gas reservoir.Mudston of low permeability and high sealing ability characteristic resistivity response on well logging curves.Thus resistivity log is an effective Method to determine cover thickness and correlate horizontal continuity.The mudston in upper Palaeozoic group in Share-Gan-Ning Basin has the characteristics of huge thickness,good continuity and high sealing ability,and is an ideal cover of gas reservoir.

摘要： 泥质岩的渗透性决定着封闭能力,泥质含量、矿物成分、颗粒结构和岩石含流体的性质是影响响渗透性和封闭能力的主要因素.泥质岩的展布范围和连续性受沉积相控制.从排替压力、厚度和展布范围等方面分析,渗透率低于10^-3md*且厚度大于3m.的泥质岩可作为中、低压夭然气藏有效盖层的下限值.渗透性低封闭能力强的泥质岩在地球物理测井曲线上特征明显,因而,利呢电测曲线是划分盖层厚度和对比横向连续性的一种有效方法.陕甘宁盆地_仁古生界泥质岩只有军度大,连续性好和封闭能力强的特点,是形成天然气藏的理想盖层.