MWDにおける掘削管の伝送特性を利用したマッドパルスの信号処理

抄録

Mud-pulse is widely used in MWD systems to transmit bottom hole information to the ground. However, distortion of pulse, which is caused by pulse reflection and damping in drill pipe, limits the transmission rate to several bits per second. This report proposes the following signal processing method to measure the mud-pulse intervals accurately. The mud-pulse transfer function of the drill pipe is measured using reference mud-pulse, which is generated by driving the mud-pulse valve with the reference signal. The distortion of the mud-pulse is compensated by multiplying the inverse transfer function of the drill pipe in frequency domain. Verification experiment on this method is carried out by using a mud-pulse transmitted in the copper pipe of 60 m in total length. As a result, the pulse series of pulse rate over 8 pulses/s is well reproduced with thee pulse interval error less than 3 ms.