Method and device for determining a driving signal for vibroseis marine sources

Abstract

Controller and method for determining a driving signal of a vibro-acoustic source element that is configured to generate acoustic waves in water. The method includes estimating at least one physical constraint of the vibro-acoustic source element; modeling a ghost function determined by a surface of the water; setting a target energy spectrum density to be emitted by the vibro-acoustic source element during the driving signal; and determining the driving signal in a controller based on at least one physical constraint, the ghost function, and the target energy spectrum density.

What is claimed is: 
     
         1 . A method for determining a driving signal of a vibro-acoustic source element that is configured to generate acoustic waves in water, the method comprising:
 estimating at least one physical constraint of the vibro-acoustic source element;   modeling a ghost function determined by a surface of the water;   setting a target energy spectrum density to be emitted by the vibro-acoustic source element during the driving signal; and   determining the driving signal in a controller based on the at least one physical constraint, the ghost function, and the target energy spectrum density.   
     
     
         2 . The method of  claim 1 , wherein the vibro-acoustic source element has an electro-magnetic actuator configured to actuate a piston. 
     
     
         3 . The method of  claim 2 , wherein the at least one physical constraint includes a combination of one or more of a maximum displacement of the piston, a maximum speed of the piston, a maximum current of a driving mechanism that drives the electro-magnetic actuator, and a maximum voltage of the driving mechanism. 
     
     
         4 . The method of  claim 2 , wherein the at least one physical constraint includes a maximum displacement of the piston, a maximum speed of the piston, a maximum current of a driving mechanism that drives the electro-magnetic actuator, and a maximum voltage of the driving mechanism. 
     
     
         5 . The method of  claim 4 , further comprising:
 determining a domain of operation of the vibro-acoustic source element as an intersection of the maximum displacement, the maximum speed, the maximum current and the maximum voltage curves.   
     
     
         6 . The method of  claim 1 , wherein the ghost function takes into account a reflection of a wave from the surface of the water. 
     
     
         7 . The method of  claim 1 , wherein the target energy spectrum density is flat. 
     
     
         8 . The method of  claim 1 , wherein a majority of time corresponding to the driving signal corresponds to a low frequency range. 
     
     
         9 . A controller configured to determine a driving signal of a vibro-acoustic source element that is configured to generate acoustic waves in water, the controller comprising:
 a processor configured to,   estimate at least one physical constraint of the vibro-acoustic source element;   receive a ghost function determined by a surface of the water;   receive a target energy spectrum density to be emitted by the vibro-acoustic source element during the driving signal; and   calculate the driving signal based on the at least one physical constraint, the ghost function, and the target energy spectrum density.   
     
     
         10 . The controller of  claim 9 , wherein the at least one physical constraint includes a combination of one or more of a maximum displacement of a piston of the vibro-acoustic source element, a maximum speed of the piston, a maximum current of a driving mechanism that drives the electro-magnetic actuator, and a maximum voltage of the driving mechanism. 
     
     
         11 . The controller of  claim 9 , wherein the at least one physical constraint includes a maximum displacement of a piston of the vibro-acoustic source element, a maximum speed of the piston, a maximum current of a driving mechanism that drives the electro-magnetic actuator, and a maximum voltage of the driving mechanism. 
     
     
         12 . The controller of  claim 11 , further comprising:
 determining a domain of operation of the vibro-acoustic source element as an intersection of the maximum displacement, the maximum speed, the maximum current and the maximum voltage curves.   
     
     
         13 . The controller of  claim 9 , wherein the ghost function takes into account a reflection of a wave from the surface of the water. 
     
     
         14 . The controller of  claim 9 , wherein the target energy spectrum density is flat. 
     
     
         15 . The controller of  claim 9 , wherein a majority of time corresponding to the driving signal corresponds to a low frequency range. 
     
     
         16 . A seismic survey system comprising:
 at least one vibro-acoustic source element configured to generate acoustic waves by moving a piston with an electro-magnetic actuator;   a driving mechanism connected to the electro-magnetic actuator and configured to drive the electro-magnetic actuator to generate the acoustic waves; and   a controller configured to generate a driving signal for the driving mechanism for generating acoustic waves in water,   wherein the controller is configured to   estimate at least one physical constraint of the vibro-acoustic source element;   receive a ghost function determined by a surface of the water;   receive a target energy spectrum density to be emitted by the vibro-acoustic source element during the driving signal; and   calculate the driving signal based on the at least one physical constraint, the ghost function, and the target energy spectrum density.   
     
     
         17 . The system of  claim 16 , wherein the at least one physical constraint includes a combination of one or more of a maximum displacement of a piston of the vibro-acoustic source element, a maximum speed of the piston, a maximum current of a driving mechanism that drives the electro-magnetic actuator, and a maximum voltage of the driving mechanism. 
     
     
         18 . A computer readable medium including computer executable instructions, wherein the instructions, when executed, implement a method for determining a driving signal of a vibro-acoustic source element that is configured to generate acoustic waves in water, the method comprising:
 estimating at least one physical constraint of the vibro-acoustic source element;   modeling a ghost function determined by a surface of the water;   setting a target energy spectrum density to be emitted by the vibro-acoustic source element during the driving signal; and   determining the driving signal in a controller based on the at least one physical constraint, the ghost function, and the target energy spectrum density.   
     
     
         19 . A method for determining a driving signal of a vibro-acoustic source element that is configured to generate acoustic waves in water, the method comprising:
 estimating at least one physical constraint of the vibro-acoustic source element;   setting a target energy spectrum density to be emitted by the vibro-acoustic source element during the driving signal; and   determining the driving signal in a controller based on the at least one physical constraint, and the target energy spectrum density.   
     
     
         20 . A seismic survey system comprising:
 at least one vibro-acoustic source element configured to generate acoustic waves by moving a piston with an actuator;   a driving mechanism connected to the actuator and configured to drive the actuator to generate the acoustic waves; and   a controller configured to generate a driving signal for the driving mechanism for generating the acoustic waves in water,   wherein the controller is configured to   estimate at least one physical constraint of the vibro-acoustic source element;   receive a target energy spectrum density to be emitted by the vibro-acoustic source element during the driving signal; and   calculate the driving signal based on the at least one physical constraint, and the target energy spectrum density.