金属套管对井下电磁波无线传输的影响

Influence of Metal Casing on Downhole Electromagnetic Wireless Transmission

电磁波无线传输技术可以实现井下数据实时传输至地面,以便地面工作人员及时获取地层参数,但受井下套管的影响,地面接收到的电磁波信号要远弱于裸眼井所传输出的信号。文章通过对电磁波在有套管的井的无线传输信道进行阻抗分析,发现其传输信号受影响的关键机理与电磁波发射器部分阻抗的分布有关。文章在此基础上建立了套管与油管耦合模型,提出了一种新的分布参数的计算方法来计算耦合模型的阻抗分布参数,同时定义了穿透系数,对发射器部分长度、信号频率、管柱物理参数等影响电磁波传输的关键因素进行定量描述,经仿真数据和现场试验验证,理论结果可靠。在有套管的井中,可以通过选择合适的信号频率、提高套管电阻率、降低套管磁导率等方法,来调整阻抗分布参数,对保证信号的稳定性、提升传输的深度具有重要意义。

Electromagnetic wave wireless transmission technology can realize real-time transmission of downhole data to the surface,so that the workers on the surface can obtain formation parameters in time.However,due to the influence of downhole casing,the electromagnetic wave signal received from the surface is much weaker than the signal transmitted from open hole.Through the impedance analysis of the wireless transmission channel of electromagnetic waves in cased wells,it is clarified that the key mechanism of the transmission difficulty of cased wells lies in the impedance distribution of the electromagnetic wave transmitting antenna.On this basis,a coupling model of casing and tubing is established,a new distribution parameter calculation method is proposed to calculate the distribution parameters of the coupling model,and the results are verified by simulation.At the same time,the penetration coefficient is defined to quantitatively describe the influence of the casing on the electromagnetic signal transmission,such as the length of the transmitter,the signal frequency and the physical parameters of the pipe string,and the field test results prove the reliability of the penetration coefficient.The analysis results obtained can be used for the improvement and optimization of electromagnetic wave wireless transmission systems,which are of great significance for enhancing signal stability and increasing transmission depth.