Adaptive Noise Cancellation for Electromagnetic-while-Drilling System
Keman Liu · 2016
An electromagnetic telemetry system is a real time data transmission system for drill string telemetry, which is detected the electromagnetic signal between the wellhead and dipole on the surface. The well-site noise is an important factor that affects the electromagnetic MWD system transmission performance. An adaptive noise cancellation method was studied to enhance the EM-MWD receiver's ability to extract very weak signals from large amounts of well site noise. Firstly, the principle of MWD is introduced, and then the characteristic of well site noise is described briefly. Thirdly, step-size parameter μ is modified based on the noise characteristics of the well site. Finally, experimental results show that the modified LMS algorithm can suppress the well site noise 3-9dB compared with LMS algorithm. And the modified LMS algorithm has faster convergence speed, smaller steady and lower excess mean square error.