Forward looking systems and methods for positioning marine seismic equipment

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).

1 . A system comprising: 
 a marine seismic spread, the spread comprising spread elements including a vessel-mounted acoustic Doppler current meter adapted to measure at least a horizontal component of a current velocity vector at least at one location generally ahead of the seismic spread elements; and    a controller adapted to use at least the horizontal component of the measured current velocity vector to control position of a seismic spread element.    
   
   
       2 . The system of  claim 1  wherein the current velocity vector is one of a plurality of parameters used to control position of the spread element.  
   
   
       3 . The system of  claim 1  wherein the acoustic Doppler current meter is mounted near a front of the vessel.  
   
   
       4 . The system of  claim 1  wherein the acoustic Doppler current meter is mounted near a center of gravity of the vessel.  
   
   
       5 . The system of  claim 1  wherein the acoustic Doppler current meter comprises two acoustic sources.  
   
   
       6 . The system of  claim 1  wherein the acoustic Doppler current meter comprises three or more acoustic sources.  
   
   
       7 . The system of  claim 1  wherein the acoustic Doppler current meter has a single acoustic transducer that is adapted to be aimed and sample at different points and vary its angle of projection in time.  
   
   
       8 . The system of  claim 1  wherein the controller maintains position of the spread element using the measured horizontal component of the velocity vector as the spread element encounters the current.  
   
   
       9 . The system of  claim 1  wherein the controller is adapted to steer the spread element using the measured horizontal component of the velocity vector to return the spread element to a defined path.  
   
   
       10 . The system of  claim 1  wherein the acoustic Doppler current meter comprises a motion compensation sub-system selected from a mechanical motion compensation sub-system, a computational motion compensation sub-system, and combinations thereof.  
   
   
       11 . The system of  claim 10  wherein the motion compensation sub-system is selected from a gimbaling system, a beam weighting system, a motion filtering system, an orientation controller, a local heave compensation system, and combinations thereof.  
   
   
       12 . The system of  claim 8  wherein the spread element is the seismic vessel.  
   
   
       13 . The system of  claim 9  wherein the spread element is the seismic vessel.  
   
   
       14 . The system of  claim 1  wherein the spread element includes the seismic vessel, a seismic source, and a plurality of seismic streamers.  
   
   
       15 . A system for acquiring marine seismic data comprising: 
 (a) a seismic spread comprising a towing vessel, a seismic source, and optionally a plurality of seismic streamers towed by the towing vessel;    (b) a acoustic Doppler current meter mounted on and adapted to measure at least a horizontal component of a current velocity vector at a point ahead of the towing vessel;    (c) a controller adapted to use the measured horizontal component of the current velocity vector to control position of the towing vessel, the seismic source, and optionally the plurality of seismic streamers; and    (d) a plurality of spread control elements associated with the towing vessel, the seismic source, and optionally the plurality of streamers, and controlled by the controller.    
   
   
       16 . The system of  claim 15  wherein the current velocity vector is one of a plurality of parameters used to control the spread control elements.  
   
   
       17 . The system of  claim 15  wherein the acoustic Doppler current meter is mounted near a front of the towing vessel.  
   
   
       18 . The system of  claim 15  wherein the acoustic Doppler current meter is mounted near a center of gravity of the towing vessel.  
   
   
       19 . The system of  claim 15  wherein the acoustic Doppler current meter comprises a motion compensation sub-system selected from a mechanical motion compensation sub-system, a computational motion compensation sub-system, and combinations thereof.  
   
   
       20 . The system of  claim 19  wherein the motion compensation sub-system is selected from a gimbaling system, a beam weighting system, a motion filtering system, an orientation controller, a local heave compensation system, and combinations thereof.  
   
   
       21 . A method comprising: 
 measuring at least a horizontal component of a current velocity vector at least at one location generally ahead of a seismic spread element using a vessel-mounted acoustic Doppler current meter; and    using the horizontal component of the current velocity vector to control position of the seismic spread element.    
   
   
       22 . The method of  claim 21  wherein the horizontal component of the current velocity vector is used in conjunction with a plurality of parameters to control position of the seismic spread element.  
   
   
       23 . The method of  claim 21  wherein the spread element is a seismic towing vessel.  
   
   
       24 . The method of  claim 21  including using the horizontal component of the current velocity vector to maintain a position of the spread element.  
   
   
       25 . The method of  claim 24  including using the measured horizontal component of the velocity vector to return the spread element to a defined path by steering the spread element.  
   
   
       26 . The method of  claim 21  including motion compensating the acoustic Doppler current meter by a method selected from mechanical motion compensation, computational motion compensation, and combinations thereof.  
   
   
       27 . The method of  claim 26  wherein the motion compensating is selected from gimbaling, beam weighting, motion filtering, controlling orientation, compensating for local heave, and combinations thereof.  
   
   
       28 . A method for acquiring marine seismic data comprising: 
 (a) towing a seismic spread comprising a towing vessel, a seismic source, and optionally a plurality of seismic streamers;    (b) measuring at least a horizontal component of a current velocity vector at a point ahead of the towing vessel using an acoustic Doppler current meter mounted on the towing vessel;    (c) adjusting the meter to compensate for motion of the towing vessel while measuring the horizontal component of the current velocity vector to form a motion-compensated horizontal component of the current velocity vector; and    (d) using the motion-compensated horizontal component of the current velocity vector to control position of the towing vessel, the seismic source, and the plurality of seismic streamers.    
   
   
       29 . The method of  claim 28  wherein the horizontal component of the current velocity vector is used in conjunction with a plurality of parameters during to control position.  
   
   
       30 . The method of  claim 28  wherein the adjusting the meter is selected from mechanical motion compensation, computational motion compensation, and combinations thereof.  
   
   
       31 . The method of  claim 30  wherein the adjusting the meter is selected from gimbaling, beam weighting, motion filtering, controlling orientation, compensating for local heave, and combinations thereof.  
   
   
       32 . A method comprising: 
 (a) creating a current profile between an acoustic Doppler current meter mounted on a seismic towing vessel and a point distant from the meter and generally in front of the seismic towing vessel during a time period, the vessel moving generally toward the point during the time period; and    (b) using the current profile to continuously estimate at least a horizontal component of a current velocity vector at the point during the time period.    
   
   
       33 . The method of  claim 32  including motion-compensating the acoustic Doppler current meter.  
   
   
       34 . The method of  claim 32  wherein a distance between the acoustic Doppler current meter and the point is continuously decreasing.  
   
   
       35 . The method of  claim 32  wherein the continuously estimating comprises continuously calculating the current velocity vector at the point using a plurality of cell pairs between two acoustic beams of the acoustic Doppler current meter.  
   
   
       36 . The method of  claim 35  wherein the continuously calculating comprises using two or more high-frequency acoustic beams.  
   
   
       37 . The method of  claim 36  wherein all acoustic beams are in one plane and all but two acoustic beams are used for quality control.  
   
   
       38 . The method of  claim 35  wherein the acoustic Doppler current meter comprises three acoustic beams, two beams in a horizontal plane and a third beam not in the horizontal plane.  
   
   
       39 . The method of  claim 32  including relating the estimated current velocity vector to an earth-fixed coordinate system by measuring the current velocity over ground using a positioning system relating to an earth-fixed coordinate system.  
   
   
       40 . A method comprising estimating a vertical current profile at a predefined distance ahead of a spread element using a vessel-mounted acoustic Doppler current meter mounted in a mounting and having one or more acoustic transducers sampling current vertical component data at a defined data sampling rate, the data sampling rate being at a frequency higher than a frequency of movement the beam transmitter.  
   
   
       41 . The method of  claim 40  comprising fixing at least the acoustic transducers in a single position relative to the vessel.  
   
   
       42 . The method of  claim 40  comprising forcing at least the acoustic transducers to move relative to the vessel.