ELF-EM Signal Processing While Drilling Based on Human-Computer Interaction Combined Algorithm

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 transmis-sion characteristics in the formation. However, as the drilling depth increases, the electromagnetic wave sig-nals received on the ground gradually weaken, becom-ing 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 for-mation is definitely one of the causes , but what mat-ters 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 transmis-sion distance of EM MWD increased. In this paper, the validity of the proposed HCID algorithm was ver-ified 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.