Fluctuation Characteristics of Pipe-to-soil Potential under Tidal Interference

Abstract As a natural telluric current interference, tidal interference severely compromises the corrosion protection effectiveness of coastal oil and gas pipelines, posing a serious threat to their safe operation. To study the regularity of tidal interference on coastal pipelines, the monitoring data of pipe-to-soil potentials (PSP) from 3 pipelines in the coastal region of Shandong and Liaoning, China were analyzed systematically. The fluctuation characteristics of PSP under tidal interference and tidal interference frequency were obtained by spectrum analysis and waveform comparison techniques. The results show that the tidal interference is a localized phenomenon whose intensity progressively decays from the coastal towards the inland of the pipeline. The range of tidal interference exceeds 30 kilometers, causing the ON potential to shift positively to +3.28V and the instant-OFF potential to shift positively to -0.4V. The intensity of tidal interference between different pipelines is obviously different, but the variation trend of the ON potential and instant-OFF potential is basically consistent with the tidal fluctuation curve. Additionally, tidal interference has a typical feature of "double peaks and double valleys" and 12-hour interference period. The established pattern of PSP fluctuations in coastal pipelines under tidal interference provides a critical foundation for corrosion protection strategies in coastal regions.