Active steering for marine sources
View Patent ↗A seismic survey system includes a winch having a winch cable coupleable to a source array towable between two deflected lead-ins, a positioning system for determining a current position of the source array and a controller for adjusting the winch to modify the current position of the source array to a desired crossline position. The winches may be attached to the deflected lead-ins or mounted on a tow vessel. The winches exert lateral forces on the source array, derived from the deflected lead-ins, to control the inline position of the source array. A method includes positioning a seismic source array in tow behind a vessel comprises determining a current position of the source array and adjusting a lateral force applied to the source array to move the source array to a desired crossline position. Optionally, by adjusting the gun cable winch, the inline position may be controlled.
1. A method for adjusting a seismic source array, comprising:
towing the seismic source array between a first array of seismic streamers and a second array of seismic streamers, the seismic source array having seismic sources for exerting energy to the earth;
receiving a current position of the seismic source array; and
moving the seismic source array in response to the current position toward the first array of seismic streamers and away from the second seismic streamers using a winch disposed on a vessel used to tow the seismic source array, wherein the winch comprises a winch cable having a first segment and a second segment coupled to opposite sides of the seismic source array.
2. The method of claim 1 , wherein moving the seismic source array comprises moving the seismic source array to a desired cross line position.
3. The method of claim 1 , wherein moving the seismic source array comprises:
decreasing the length of the first segment; and
increasing the length of the second segment.
4. The method of claim 1 , wherein moving the seismic source array comprises rotating a first reel around which the first segment is wrapped in a first direction and rotating a second reel around which the second segment is wrapped in a second direction opposite the first direction, wherein the first reel and the second reel are mounted on the vessel.
5. The method of claim 4 , further comprising:
comparing the current position with a desired cross line position; and
rotating the first reel and the second reel to guide the seismic source array toward the desired cross line position.
6. The method of claim 1 , wherein moving the seismic source array comprises rotating a capstan around which the first segment and the second segment are wrapped, wherein the capstan is mounted on the vessel.
7. The method of claim 1 , wherein moving the seismic source array comprises:
taking in the first segment; and
letting out the second segment.
8. The method of claim 1 , wherein the first segment is threaded through a first pulley attached to a first lead-in coupled to the first array of seismic streamers and the second segment is threaded through a second pulley attached to a second lead-in coupled to the second array of seismic streamers.
9. The method of claim 1 , further comprising:
towing the seismic source array substantially along the center line of the vessel; and
towing the first array of seismic streamers and the second array of seismic streamers off the center line of the vessel.
10. The method of claim 1 , wherein moving the seismic source array comprises applying lateral forces to the seismic source array.
11. The method of claim 1 , wherein the current position is determined using a global positioning system.
12. A method for adjusting a seismic source array, comprising:
towing the seismic source array substantially along the center line of a vessel, the seismic source array having seismic sources for exerting energy to the earth;
towing a first array of seismic streamers and a second array of seismic streamers off the center line of the vessel;
receiving a current position of the seismic source array;
comparing the current position with a desired position; and
exerting lateral forces to the seismic source array toward the first array of seismic streamers in response to the comparison using a winch disposed on the vessel, wherein the winch comprises a winch cable having a first segment and a second segment coupled to opposite sides of the seismic source array.
13. The method of claim 12 , wherein exerting the lateral forces comprises:
decreasing the length of the first segment; and
increasing the length of the second segment.