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Forward looking systems and methods for positioning marine seismic equipment

a technology of forward looking and seismic equipment, applied in seismology, instruments, seismicology for water-covered areas, etc., can solve the problems of inability to provide the desired precision in positioning marine seismic spread elements, and achieve the effect of accurately controlling the positioning of spread elements and good picture of the vertical water column

Inactive Publication Date: 2006-11-16
WESTERNGECO LLC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0006] In accordance with the present invention, systems and methods are described for positioning one or more marine seismic spread elements, which may include a towing vessel, seismic source, and streamers. The systems and methods of the invention, which employ vessel-mounted acoustic Doppler current meters, reduce or overcome problems with previous systems and methods employing acoustic Doppler current meters. Systems and methods of the invention may be used during seismic data collection, including 3-D and 4-D seismic surveying.
[0020] Another method of the invention comprises estimating a vertical current profile at a predefined distance ahead of a spread element by using a vessel-mounted acoustic Doppler current meter mounted in a mounting and sampling current vertical component data at a defined rate, the mounting either fixing the meter in a single position relative to the vessel or enabling at least the acoustic beam transmitter or transmitters (sometimes referred to herein as “eyes”) to move relative to the vessel, the data sampling rate being at a frequency higher than a frequency of movement of meter or the beam transmitter. If a fixed position mounting is used, the meter will be useful when the vessel pitches. If the vessel is riding in a calm body of water, a pitching motion may be enforced. A mounting having a combination of features may be used, wherein the meter may be locked in a fixed position when the vessel is pitching, and when the seas are calm the locking mechanism released and a controlled pitching motion imposed, for example using a sensor / controller / actuator arrangement. During a pitch cycle the aiming point will the scan through the vertical water column with a depth variation determined by the pitch amplitudes and the distance ahead. The spread elements are located at different depths with the vessel from 0 to maximum draft of the vessel, and the source generally shallower than the streamers, which again are deeper than the vessel, and particularly in over-under streamer configuration and during handling when the streamers are stacked on top of each other. Knowing that the current often changes both in strength and direction in the water column, and in particular close (within 10's of meters) to the sea surface, then it is clear that a good picture of the vertical water column may be helpful for controlling the positioning of the spread elements accurately.

Problems solved by technology

While there have been some efforts to use information regarding environmental conditions, including ocean currents, previous attempts have not provided the desired precision in positioning marine seismic spread elements.

Method used

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  • Forward looking systems and methods for positioning marine seismic equipment
  • Forward looking systems and methods for positioning marine seismic equipment
  • Forward looking systems and methods for positioning marine seismic equipment

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Embodiment Construction

[0032] In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible. For example, in the discussion herein, aspects of the invention are developed within the general context of controlled positioning of seismic spread elements, which may employ computer-executable instructions, such as program modules, being executed by one or more conventional computers. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Moreover, those skilled in the art will appreciate that the invention may be practiced in whole or in part with other computer system configurations, including hand-held devices, personal digita...

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Abstract

Systems and methods for positioning one or more spread elements of a marine seismic spread are described. One system comprises a seismic vessel-mounted acoustic Doppler current meter adapted to ascertain at least the horizontal component of the current velocity vector at a point ahead of the seismic vessel, and one or more controllers adapted to use the ascertained current velocity vector to control position of one or more seismic spread elements. It is emphasized that this abstract is provided to comply with the rules requiring an abstract, which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. 37 CFR 1.72(b).

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of Invention [0002] The present invention relates to the field of marine seismic instrumentation and methods of using same. More specifically, the invention relates to systems and methods for positioning one or more spread elements of a marine seismic spread using information about the ocean current ahead of the towing vessel. [0003] 2. Related Art [0004] Marine seismic exploration investigates and maps the structure and character of subsurface geological formations underlying a body of water. For large survey areas, seismic vessels tow one or more seismic sources and multiple seismic streamer cables through the water. The entire system is typically referred to as a spread, and the elements making up the spread are referred to as spread elements. The seismic sources typically comprise compressed air guns for generating acoustic pulses in the water. The energy from these pulses propagates downwardly into the geological formations and is ref...

Claims

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Application Information

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IPC IPC(8): G01V1/38
CPCG01V1/3826
Inventor TOENNESSEN, RUNEPAULSEN, JENS OLAVWELKER, KENNETH
Owner WESTERNGECO LLC
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