Patent EA-001035-B1 (EA)
Title: Seismic survey vessel
Inventor: JOHNSEN BAARD
IPC: B63B35/00
Filed: 1998-06-23
Abstract: 1. A seismic survey vessel having a displacement monohull, and powered drum means and cooperating guide means for deploying and recovering seismic streamers over the stern of the vessel via a streamer deck disposed at a substantial height above the waterline of the vessel, wherein the drum means are mounted substantially amidships in the vessel, the streamer deck at the stem of the vessel projects laterally outwardly from the hull of the vessel on both sides of the centre line of the vessel and is wider than the remainder of the vessel, and the guide means includes guide devices distributed across substantially the whole width of the streamer deck to facilitate the lateral spreading of the streamers. 2. A vessel as claimed in claim 1, wherein the streamer deck of the vessel is an upper deck (although not necessarily the uppermost deck), at a height such that when the vessel is normally docked, the deck is well above the dock. 3. A vessel as claimed in claim 1 or claim 2, wherein the width of the streamer deck decreases progressively from the stern of the vessel until it becomes substantially equal to the width of the vessel amidships. 4. A vessel as claimed in any preceding claim, wherein at least parts of the drum means are mounted in the vessel at a level lower than the streamer deck. 5. A vessel as claimed in any preceding claim, further comprising a further deck below the streamer deck at the stern of the vessel, said further deck being provided with means for deploying and recovering seismic source means over the stem of the vessel. 6. A vessel as claimed in any preceding claim, wherein the guide means comprises a respective streamer handling apparatus associated with each of a plurality of the streamers, each such apparatus comprising  a beam; means for mounting the beam above normal head height above the streamer deck of the vessel, such that the beam extends generally longitudinally of the vessel, the mounting means including a pivotal connection to the sternmost end of the beam permitting said end to pivot about a horizontal axis extending generally transversely of the beam, and extendable support means for lowering and raising the other end of the beam towards and away from the streamer deck; and a respective one of said guide devices, each such guide device comprising pulley means secured to and movable along the beam. 7. A vessel as claimed in claim 6, wherein the pulley means is pivotable about an axis which extends generally longitudinally of the beam. 8. A vessel as claimed in claim 6, wherein the pulley means comprises carriage means movable along the beam, a pulley device, and means for suspending the pulley device beneath the carriage means. 9. A vessel as claimed in claim 8, wherein the suspension means comprises a collar which is rotatably supported on the carriage means and which is rotatable about the longitudinal axis of the beam. 10. A vessel as claimed in claim 8 or claim 9, wherein the carriage means includes at least one hydraulic motor arranged to move the carriage means in both directions along the beam. 11. A vessel as claimed in any one of claims 8 to 10, wherein the carriage means is provided at its sternmost end with winch means. 12. A vessel as claimed in any one of claims 8 to 11, wherein the pulley device is pivotable about an axis which extends generally transversely of the beam. 13. A vessel as claimed in any one of claims 6 to 12, wherein the support means comprises a telescopic member which is pivotally connected at one end to the mounting means and at the other end to said other end of the beam. 14. A vessel as claimed in any one of claims 6 to 13, wherein the support means is hydraulically operable. 15. A vessel as claimed in any one of claims 6 to 14, further comprising downwardly projecting guidance means which is positioned at said other end of the beam and which engages and pushes down the streamer when said other end of the beam is lowered. 16. A vessel as claimed in any one of claims 6 to 15, said vessel having a further deck above the streamer deck, wherein the mounting means is secured to the underside of the further deck.