地层对电磁随钻测量信号的影响研究
Study on Strata Affected to Electromagnetic with Drilling Measuring Signal
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摘要: 为了改善电磁波随钻测量系统的信号传输的距离和质量,通过对电磁波在地层中传输特性的分析,研究了地层电导率、磁导率、电磁波发射频率和发射天线长度这4个方面对电磁波信号衰减和传输深度的影响。结果表明:电磁波传输距离随着发射频率减小而增大,高电阻率地层有利于电磁波的传输。当频率在5~20 Hz时,传输距离1 000~2 000 m时,强度信号较强,能很好地满足工程的需要,选用穿孔外接金属环套激励天线的效果最好,而且金属环长度应尽量长,而绝缘段长度为0.5 m时,发射天线的效果最佳。Abstract: In order to improve the electromagnetic wave with the signal transmission distance and quantity of the drilling measuring system, with the analysis on th e transmission features of the electromagnetic wave in the strata, the paper had a study on the electric conductance rate of the rock, magnetic conductance rate, the tr ansmitting frequency of the electromagnetic wave and the length of transmitting antenna affected to the signal attenuation and transmission depth of the electromagneti C wave.The results showed that the transmission distance of the electromagnetic wave would be increased with the transmitting frequency reduced and the high electric resistance strata would be favorable for the transmission of the electromagnetic wave.When the frequency was 520 Hz and transmission distance was 1 0002 000 m, th e signal strength would be high and could meet the requirements of the engineering.The excitation antenna with the metal ring loop connected would have best effect, t he length of the metal ring should be as long as possible.When the length of the insulation section was 0.5 m, the effect of the transmitting antenna would be best.