Systems and methods for removal of swell noise in marine electromagnetic surveys

摘要

Methods and systems for determining and removing swell noise from electric field data collected from streamers towed at different are disclosed. In one aspect, a first set of streamers called upper streamers is towed at a shallow depth, and the second set of streamers called lower streamers is towed below the upper streamers. Receivers located along the streamers measure surrounding electric fields and produce electric field signals. A proportionality parameter is calculated as a function of the electric field signals generated by vertically aligned receivers. The proportionality parameter can be used to calculate an approximate swell noise that is used to remove swell noise from electric field data measured by the receivers.

主权项

1. A method for determining swell noise, the method comprising:
towing substantially vertically aligned receivers and an electromagnetic source along a survey track; adjusting an electromagnetic field to be output from the electromagnetic source during a conditioning period of the survey track; receiving signals that encode electromagnetic field data measured by the vertically aligned receivers in the conditioning period; calculating a proportionality parameter as a function of the signals; calculating swell noise as a function of the proportionality parameter and signals that encode electromagnetic field data measured by the vertically aligned receivers during a survey period; subtracting swell noise from the signals that encode electromagnetic field data to obtain swell-noise corrected signals; and generating a geophysical image based at least in part on the swell-noise corrected signals.