钻柱内孔变径结构条件下微波传播衰减规律研究

Analysis of the Attenuation Law of Microwave Propagation with the Drill String Bore Variable Diameter Structure

为掌握钻柱內孔微波传输的最佳频点,获取微波信道的衰减规律及有效传输距离,将钻柱内孔视为超长不规则有耗圆波导,采用微波耦合理论计算了其微波最佳传输频点,分析了信道中的微波模式。采用微波传输等效电路法建立了信道模型,研究并建立了钻柱内孔微波信道信号衰减规律模型。同时针对超长钻柱,提出单位长度平均功率损耗系数对有效传输距离进行简化分析。研究结果表明,钻柱内孔沿轴向存在内径渐变段和突变点,微波传输存在大量反射过程,信道的阻抗变化是影响传输质量的主要因素。建立的衰减模型比仅考虑表面电阻涡流损耗的模型更准确,更具有现场指导意义。

In this paper,the drill string bore is regarded as an irregular lossy cylindrical waveguide,in order to obtain the best frequency point,the attenuation law and the effective transmission distance of the microwave channel. The best transmission frequency point of microwave is calculated by the electromagnetic wave coupling theory,and the microwave mode in the channel is analyzed. Furthermore,the channel model is established by microwave transmission equivalent circuit method and the signal attenuation rule of drill string bore microwave channel is established. In addition,in view of the ultra-long drill string channel,this paper proposes a simplified analysis method of effective transmission distance using average loss coefficient of unit length. The test results show that the pipe bore of drill string has several inner diameter gradual change sections and sudden change points along the axial direction,and there are a lot of reflection processes in the microwave transmission,therefore the channel impedance changes is the main factors affecting the transmission quality. The attenuation model established in this paper is more accurate than the model considering only the eddy current loss of surface resistance,which is more helpful for on-site guidance.