宽频带多偏移距电磁测深的几个电性参数  

SEVERAL ELECTRICAL PARAMETER EXTRACTED FROM WIDE BAND MULTI-OFFSETS ELECTROMAGNETIC SOUNDING

作　　者：汤井田[1] 罗维斌[1] 刘长生[1] 

机构地区：[1]中南大学信息物理工程学院,湖南长沙410083

出　　处：《物探化探计算技术》2008年第2期145-153,共9页Computing Techniques For Geophysical and Geochemical Exploration

摘　　要：计算了宽频带多偏移距层状大地电偶极-偶极装置的复电阻率，用高频和低频二个频率的复电阻率计算了频散率，并用各道最低频的复电阻率（频率相同），计算了道间复电阻率变化率。计算结果表明，采用诸如逆重复m序列等宽频带信号激励，多偏移距同线偶极-偶极同时观测，计算的频散率及相邻道间低频复电阻率的变化率，可作为物性参数来检测大埋深高阻或低阻薄层的存在。低频接地偶极产生的传导电流，有利于检测到埋深较大的高阻薄层。多偏移距同时观测方法是一种几何测深法，如果有高阻极化体存在，在适当的收发距上，道间低频复电阻率道间变化率或频散率的变化率，就会出现极大值。它所对应的收发距可用来估计极化体埋深，约为极化体埋深的2．2倍-3．5倍。The complex resistivity (CR) of the layered earth model surveying with wide band source and multi offsets electrical dipole-dipole configuration was computed. The percent frequency effect (PFE) was computed using both complex resistivities with high and low frequencies, and differentiation of low frequency CR with offset was computed. The numerical result implies that when exciting source is a wide band signal such as inverted-repeat m binary sequence and simultaneous observation with multi offsets inline dipole-dipole configuration, the differentiation of percent frequency effect with offset(DPFE) and differentiation of low frequency CR with offset as property parameters can indicate whether a high or a low resistor induced polarization thin abnormality is present. The low frequency grounded dipole can generate galvanic current which is effective for detecting the deeply buried thin resistor. Simultaneous observation with multi offsets inline dipole-dipole is a geometry sounding method. If a high resistor induced polarization (IP) body is present, the differentiation of low frequency CR with offset or the differentiation of percent frequency effect with offset(DPEF) will have a peak value at appropriate offset, and this offset can be used to estimate the buried depth of the resistor IP body, which is empirically about 2.2 to 3.5 times of the buried depth.

关 键 词：同线偶极-偶极 多偏移距 视幅频率道间变化率 低频复电阻率道间变化率 

分 类 号：P631[天文地球—地质矿产勘探]