The major gas-paying formation of Gas Field A,which is located in Qaidam Basin,shows apparently higher resistivity than the host. With MT method, we can detect the contrast of these phenomena. Usually there are many factors increasing resistivity of formations. Since MT method can not definitely determine which factor increased formations' resistivity, we have to make a test about induced polarization effects. Considering the local geological targets,we use Cole-Cole model of spectrum induced polarization to simulate induced polarization effects of ground and abstract information related to IP effect. The test shows that gas reservoir appears both high resistivity and IP effect. So we can use IP effect to further evaluate targets which have high resistivity, and predictwith more evidences if they contain gas.%柴达木盆地A气田主要产气层段因与其上、下段电性差异大,呈现明显的高电阻率特征,应用大地电磁测深方法能够反映这种电性变化.但影响地层电阻率升高的因素较多,通常应用大地电磁测深也不能准确确定引起高电阻率异常的原因.为此,本文开展大地电磁激电效应试验.结合试验区的地质目标,在电磁法中引入频谱激电法中的柯尔-柯尔模型模拟大地激发极化特性,提取激发极化信息.试验结果表明,气田区呈现高电阻率、高极化异常模式,由此可利用极化异常对高电阻率异常的含油气性进行检测评价,有可能指示油气的存在.
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