含甲烷水合物多孔介质的复电阻率频散特性与模型

摘要

在获得3.5%NaCl溶液-海砂-甲烷水合物体系阻抗谱参数的基础下,通过计算得到了该体系的复电阻率数据,分析了复电阻率参数的频散特性以及水合物饱和度对其频散特性的影响,进而建立了复电阻率模型.结果表明:在0.1~1 MHz测试频率范围内,含甲烷水合物多孔介质的复电阻率存在明显频散现象;甲烷水合物饱和度与复电阻率频散特征参数密切相关,饱和度越小复电阻率频散特性越显著.当测试频率范围为0.1~10 Hz时,复电阻率幅值、实部和虚部与测试频率在双对数坐标系下呈线性关系,其斜率的绝对值与水合物饱和度之间成递减的近似线性关系;而当测试频率范围为10~1 MHz时,复电阻率幅值和实部的频散度与水合物饱和度符合递减的近似线性关系.测试条件下,含水合物多孔介质体系的阻抗谱可以用电阻和电容的串联等效电路模型来拟合,基于此建立的复电阻率模型可用来计算水合物饱和度.%The complex resistivity parameter was obtained based on the measured impedance spectroscopy of the methane hydrate-porous medium-brine of 3.5%.The frequency dispersion characteristics of complex resistivity and the effects of hydrate saturation were analyzed.Finally, a model of complex resistivity was proposed for hydrate saturation estimation.It has been demonstrated that the complex resistivity of porous medium containing methane hydrate exhibits remarkable frequency dispersion characteristics within the range of 0.1~1 MHz.There is a close relationship between the methane hydrate saturation and characteristic parameters of frequency dispersion.The frequency dispersion characteristics of complex resistivity becomes more significant with the decrease of hydrate saturation.The amplitude, real part and imaginary part of complex resistivity vary linearly with the test frequency in the double logarithmic coordinate within the range of 0.1~10 Hz, and there is a nearly linear relationship between the absolute values of slope and hydrate saturation.The percent frequency effect of the amplitude and real part of complex resistivity decreases linearly with an increasing hydrate saturation within the range of 10 Hz~1 MHz.Under the test conditions in this study the impedance spectroscopy of porous medium containing hydrate can be fitted through an equivalent circuit model with a resistor and capacitor in series, and the resultant complex resistivity model can be used to calculate the gas hydrate saturation.