Novel two-step filtering scheme for a logging-while-drilling system

A logging-while-drilling (LWD) system is usually deployed in the oil drilling process in order to provide real-time monitoring of the position and orientation of a hole. Encoded signals including the data coming from down-hole sensors are inevitably contaminated during their collection and transmission to the surface. Before decoding the signals into different physical parameters, the noise should be filtered out to guarantee that correct parameter values could be acquired. In this paper, according to the characteristics of LWD signals, we propose a novel two-step filtering scheme in which a dynamic part mean filtering algorithm is proposed to separate the direct current components and a windowed limited impulse response (FIR) algorithm is deployed to filter out the high-frequency noise. The scheme has been integrated into the surface processing software and the whole LWD system for the horizontal well drilling. Some experimental results are presented to show the feasibility and good performance of the proposed two-step filtering scheme.