雷达测井数值模拟及电磁波传播特征分析

Numerical Simulations of Radar Logging and the Characteristic Analysis of Electromagnetic Propagation

雷达测井是一种新型的高频电磁波测井方法,实际测井时其信号会受到钻井液、泥浆侵入及井筒结构的影响。建立了泥浆侵入环境下的裸眼井雷达测井模型,采用数值模拟的方法对泥浆侵入环境下的电磁波传播特性进行了研究,分析了井下几个关键参数对雷达接收信号的影响。研究结果表明:储层中传播的电磁波呈现出耳郭状明暗交替的波阵面特征,使得接收波形较为复杂;过大的天线收发间距会影响侵入前缘反射波成分的正确提取,泥浆层的厚度对于电磁信号的衰减有影响,泥浆矿化度对于信号的衰减和相位畸变影响很大。因此建议在实际测井时应合理地设计收发天线间距,并尽量使井下天线靠近井壁,雷达测井的有效使用应该限制在淡水泥浆钻井的储层环境中。

Radar logging is a novel high-frequency electromagnetic（EM）logging method.In the field applications,it is influenced by drilling fluid,mud invasion,and borehole effects.This study established a numerical model of radar logging in an open-hole and invaded reservoir environment.The study investigated the propagation characteristics of EM wave,and analyzed several key downhole parameters that affect receiving signals.The study yields the following results.The EM wave fronts present a character of pinna shape with dim and brighten alternation,complicating the receiving waveforms.A great offset of antennas makes the extraction of reflection signal difficult and a great distance of the standoff between the antennas and the well wall increases EM attenuation.The salinity of mud filtrate has great impact on the EM attenuation and phase distortion.We suggest that the distance of antenna offset should be considered when antennas are designed,the downhole antennas should be as close to the well wall as possible,and the suitable environment for using radar logging is fresh water-base mud with low salinity.