ELF-EM signal processing while drilling based on human-computer interaction combined algorithm

Abstract

In the electromagnetic wave measurement while drilling (EM MWD), the extra low frequency electromagnetic wave (ELF-EM) below 20Hz was usually chosen as the carrier because of its transmission characteristics in the formation. However, as the drilling depth increases, the electromagnetic wave signals received on the ground gradually weaken, becoming lower than a certain signal-to-noise ratio (SNR) and making it impossible to be decoded or transmitted. The attenuation of electromagnetic wave in the formation is definitely one of the causes, but what matters more is the influence of environment noise at the well site, especially the in-band interference noise and random noise. Targeting at the out-of-band noise, the bandpass filter, which is invalid to the in-band noise, can be used to eliminate the noise out of the carrier's main band. To cope with the question, an algorithm based on the human-computer interaction detection (HCID) was proposed in this paper that improves the SNR of ELF-EM signals, with the effective transmission distance of EM MWD increased. In this paper, the validity of the proposed HCID algorithm was verified through communication processing performance simulation and field data comparison, thus providing a reference for engineers and technicians in this field. Theoretical analysis and experimental data verification show that the combined algorithm decodes effectively under the in-band interference noise of − 80dB SNR and in-band random noise of − 17dB SNR.