SYSTEMS AND METHODS FOR REMOVAL OF SWELL NOISE IN MARINE ELECTROMAGNETIC SURVEYS
First Claim
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; and
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.
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Abstract
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.
37 Citations
27 Claims
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1. A method for determining swell noise, the method comprising:
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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; and 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for determining swell noise in signal data generated by receivers of upper and lower streamers towed by a survey vessel, the method comprising:
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receiving a first signal associated with an upper receiver of the upper streamer and a second signal associated with a lower receiver of the lower streamer, the first signal and the second signal encode electromagnetic field data measured in a conditioning period of a ship track traveled by the survey vessel; calculating a proportionality parameter as a function of the first signal and the second signal measured in the conditioning period; and calculating swell noise as a function of the proportionality parameter and signals associated with the upper receiver and the lower receiver measured in a survey period. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
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20. A computer-readable medium having machine-readable instruction encoded thereon to enable one or more processors of a computer system to perform the operations of
receiving a first signal associated with an upper receiver of the upper streamer and a second signal associated with a lower receiver of the lower streamer, the first signal and the second signal encode electromagnetic field data measured in a conditioning period of a ship track traveled by the survey vessel; -
calculating a proportionality parameter as a function of the first signal and the second signal measured in the conditioning period; and calculating swell noise as a function of the proportionality parameter and signals associated with the upper receiver and the lower receiver measured in a survey period. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27)
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Specification