低频含水岩石介电高值成因及改进测量方法

含水岩石在低频下常常呈现高达104以上的介电常数值,数值模拟和实测结果都表明这是由于岩石中存在着传导电流,其具有与外场同相和正交的实、虚部,这二者通过与频率成反比的关系叠加在介电常数上.提出在平行板电容器一极板与被测岩石样品间夹入不导电薄膜的办法来消除传导电流的不利影响.对标准件的测量表明该方法的最大误差在4%以内.用该方法测量淡水饱和岩石样品,结果得到合理适中的介电常数值及清晰明了的介电极化谱.除湿岩石外,该方法还适用于冰、生物肌体等固态导电介质的介电谱研究.

Cause for dielectric highs measured on wet rocks at low frequencies and an improved measurement

Wet rocks exhibit relative dielectric values as high as 10⁴ and above which are elusive to explanation. Numerical modeling and measurements show that conduction current exists in rocks. Both quadrature and in-phase components of the conduction current, via inverse proportion to frequency, superimpose on permittivity. We propose to eliminate the influence of the conduction current by inserting an insulating thin film between one polar plate of the parallel capacitor and the rock sample. The measurement on standard sample shows the method has a maximum error within 4%. Measurements on fresh-water saturated rock samples obtain reasonable and moderate permittivity values and clear polarization spectra. The method can also be used to measure dielectric spectra of other solid conductive media such as ice, organic bodies and etc.