Actively controlled buoy based marine seismic survey system and method

Abstract

A buoy for recording seismic signals while underwater. The buoy includes a body; a buoyancy system configured to control a buoyancy of the body to descend to a predetermined depth (H 1 ), a propulsion system configured to actively adjust a position of the body at a given position (X, Y); a seismic sensor located on the body and configured to record the seismic signals; and a control device configured to control the buoyancy system to maintain the body substantially at the predetermined depth (H 1 ) and to control the propulsion system to maintain the body substantially at the given position (X, Y) while the buoy records seismic data, and also to instruct the seismic sensor when to record seismic signals.

What is claimed is: 
     
         1 . A seismic survey system for recording seismic data underwater in the presence of underwater currents, the system comprising:
 a first buoy configured to descend in water at a given location, which is characterized by a depth (H 1 ) and a horizontal position in a horizontal XY plane, the first buoy having a seismic receiver for recording the seismic data, a buoyancy system for maintaining the predetermined depth (H 1 ), and a propulsion system for adjusting its horizontal position; and   a first vessel configured to launch the first buoy,   wherein the first buoy is configured to record the seismic data underwater while maintaining the horizontal position in the horizontal XY plane by compensating with the propulsion system a motion due to the underwater currents so that the first buoy is substantially motionless.   
     
     
         2 . The system of  claim 1 , wherein the first vessel launches additional first buoys, along a first line, to record seismic data while underwater and in a substantially motionless position. 
     
     
         3 . The system of  claim 2 , wherein the first vessel is configured to launch second plural buoys along the first line, later in time than the first plural buoys. 
     
     
         4 . The system of  claim 3 , wherein the first vessel is configured to launch waves of buoys to cover a desired area for collecting the seismic data. 
     
     
         5 . The system of  claim 2 , further comprising:
 a second vessel configured to recover the first buoy at a second line, wherein there is a predetermined distance between the first and second lines.   
     
     
         6 . The system of  claim 1 , further comprising:
 a computer system configured to calculate the underwater currents prior to launching the first buoy,   wherein the computer system calculates the underwater currents based on historic data.   
     
     
         7 . The system of  claim 6 , wherein the computer system is configured to receive current positions of the first buoy and additional first buoys, and to calculate new trajectories of the underwater currents based on the current positions of the first buoy and the additional first buoys. 
     
     
         8 . The system of  claim 1 , further comprising:
 second plural buoys configured to descend to a second predetermined depth in water.   
     
     
         9 . The system of  claim 1 , further comprising:
 second plural buoys configured to descend in water to form a variable-depth profile.   
     
     
         10 . A seismic survey system for recording seismic data underwater, the system comprising:
 first plural buoys configured to descend to a first predetermined depth (H 1 ) in water and at corresponding given positions (X,Y) in a plane (XY) substantially parallel with a water surface, each of the first plural buoys having a seismic receiver for recording the seismic data;   a first vessel configured to launch the first plural buoys; and   a first acoustic system attached to the first vessel and configured to detect a position of at least one buoy of the first plural buoys while underwater,   wherein the at least one buoy has an active propulsion system that maintains the given position (X,Y) underwater while recording the seismic data, and   wherein the active propulsion system compensates for a motion of the at least one buoy due to water currents for maintaining the at least one buoy substantially motionless at the given position (X,Y).   
     
     
         11 . The system of  claim 10 , wherein a set of buoys are launched underwater, along a distance (D) between the first vessel and a second vessel, which recovers the first plural buoys. 
     
     
         12 . The system of  claim 11 , wherein a horizontal distance (d) between two adjacent buoys of the set of buoys is between 10 m and 200 m and the distance (D) is about 10 km. 
     
     
         13 . The system of  claim 11 , wherein the set of buoys forms the equivalent of a traditional streamer. 
     
     
         14 . The system of  claim 10 , wherein the first predetermined depth (H 1 ) is larger than a depth of a traditional streamer. 
     
     
         15 . The system of  claim 10 , wherein the first predetermined depth (H 1 ) is about 200 m or more. 
     
     
         16 . The system of  claim 10 , further comprising:
 second plural buoys configured to descend at a second predetermined depth (H 2 ) in water.   
     
     
         17 . The system of  claim 10 , further comprising:
 second plural buoys configured to descend in water to form a variable-depth profile.   
     
     
         18 . The system of  claim 10 , wherein the first acoustic system includes at least two acoustic pingers, each pinger being configured to emit an acoustic wave with a unique frequency. 
     
     
         19 . The system of  claim 10 , wherein the at least one buoy further comprises:
 an acoustic system for determining a position of the at least one buoy.   
     
     
         20 . A buoy for recording seismic data while underwater, the buoy comprising:
 a body;   a buoyancy system configured to control a buoyancy of the body to descend to a predetermined depth (H 1 ),   a propulsion system configured to actively adjust a position of the body in a given plane (XY);   a seismic sensor located on the body and configured to record the seismic data; and   a control device configured to control the buoyancy system to maintain the body substantially at the predetermined depth (H 1 ) and to control the propulsion system to maintain the body substantially motionless at a given position (X, Y) in the given plane (XY) while the buoy records seismic data,   wherein the propulsion system compensates for a motion of the body due to water currents for maintaining the body substantially motionless at the given position (X, Y).