钻铤对随钻电磁波测井电压信号影响分析

Analysis of Effects of Drill Collars on the Voltage of Electromagnetic Wave Logging While Drilling

随钻电磁波测井仪器的发射及接收线圈缠绕在钻铤上,利用圆柱状分层介质模型可以模拟线圈电压信号随井眼参数和地层参数的变化特征,分析钻铤对电压信号的影响规律。针对随钻电磁波测井仪器轴向发射-倾斜接收线圈结构,给出计算倾斜接收线圈电压的解析算法,通过对谱域中背景场与反射场分别积分,增加了算法的稳定性。模拟了倾斜接收线圈的电压信号随源距、发射频率及地层电导率变化特征,对比分析了钻铤、井眼泥浆对电压信号的影响。数值模拟结果表明,钻铤对倾斜接收线圈电压信号强度及曲线形态的影响远大于井眼泥浆的影响,为后期随钻测井资料处理校正或标定提供了理论基础。

The transmitter and receiver coils wrapped around drill collars of the electromagnetic wave logging while drilling tool.By using a cylindrical layered medium model,the characteristics of coil voltage changing with borehole mud and formation parameters can be simulated,and the effects of drill collars on voltage can be analyzed.This paper provides an analytical algorithm of calculating the voltage for the axial transmitting and tilted receiving instrument structure.By integrating the background field and reflection field in the spectral domain individually,the stability of the algorithm is increased.The characteristics of voltage variation with source distance,emission frequency,and formation conductivity are simulated,and the effects of drill collars and borehole mud on voltage are compared and analyzed.Numerical simulation results shows that the effects on voltage strength and its curve shape from drill collars is much greater than that from borehole mud.This provides a theoretical basis for the correction or calibration of logging data processing while drilling in the later stage.