STEERING OF MARINE EQUIPMENT TOWED BY A VESSEL BY FLOAT WITH WINGS

Abstract

The present invention relates to the field of marine towing operations for marine seismic survey systems and seismic data gathering. More specifically, the present invention relates to seismic sources and receiver sensor cables, streamers, floats etc., that have means for adjusting and keeping a desired position in an array during a tow behind a vessel. The apparatus comprises a body (10) with means for being towed behind a vessel, means for connecting with and supporting and steering submerged marine seismic equipment laterally in the water and means for remote control from vessel. The body (10) of the apparatus has a forward positioned float unit (16) with an elongated rear float (12) hinged at the rear of the forward float. The forward float unit has vertical wings (18, 18′) with means for adjusting angle of attack in water.

Claims

1. An apparatus and system for guiding marine seismic equipment when towed behind a vessel at sea, the apparatus comprising; a body (10) with means for being towed by a vessel (2), means for connecting with and supporting submerged marine equipment (14), means for steering said marine seismic equipment laterally in the water, means for remote control from vessel, the apparatus characterized by; having a body comprising of a forward positioned float unit (10/16) with an elongated rear float (12) hinged at the rear of the said forward float, said forward float unit having vertical wings (18, 18′) submerged in the water, having means for adjusting angle of attack in water of forward float unit.

2. An apparatus according to claim 1, whereas means for adjusting angle of attack comprise one or a combination of; wire (30) and motorized reel (34), wire (30, 38) connected with reel on vessel, wire (30) connected with a hydraulic or electric actuator 42.

3. An apparatus according to claim 2, whereas said wire (30) is connected between forward float (16) and point on extension of tow bar (11), the length of wire dictates angle of attack of forward float.

4. An apparatus according to claim 1, whereas means for adjusting angle of attack comprise of a hydraulic or electric actuator (42) connected between forward float and point on a tow bar (11), the length of the actuator arm dictates angle of attack of forward float.

5. An apparatus according to claim 1, whereas the rear float (12) is of a tubular design and flexible in lateral direction.

6. An apparatus according to claim 1, whereas said forward float unit (16) has means for connecting to and steering an array of seismic equipment within a tow.

7. An apparatus according to claim 1, designed to position seismic source equipment relative to other seismic equipment being towed by the vessel such as a streamer array (14).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The foregoing aspects and many of the advantages of the present invention will be more appreciated and better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

[0023] FIG. 1 shows overview of float with source towed behind a vessel.

[0024] FIG. 2 shows overview of the float and head unit according to the invention.

[0025] FIG. 3 shows a side view of the float and head unit and supported seismic gun set up.

[0026] FIG. 4 shows a perspective view of the head unit of float.

[0027] FIGS. 5a-5b illustrate means for steering of invention.

[0028] FIG. 6 illustrate another embodiment for steering of the invention.

[0029] FIG. 7 illustrate by block schematic, remote control of float and head float unit.

DETAILED DESCRIPTION OF THE INVENTION

[0030] Disclosed in FIG. 1 is shown an embodiment of the invention, representing a type float and deflector device 1 for use in marine seismic survey systems and seismic data gathering, wherein the inventive head float unit is part of a float for seismic sources (seismic guns) towed behind a vessel 2 as part of a seismic survey array. There will be typically at least three of these sources on either side of centreline 3, each of the outer having means for steering according to the invention. Seismic receiver sensor cables, streamers, are deflected and towed further behind the source array, not shown but in a manner as known from prior art. Numeral 4 is lead cable lateral deflected for spread of streamer array, not shown. Denoted number 3 is a centreline, whereas everything is mirrored.

[0031] FIG. 2 shows an overview of the float 1 which has a head 10 linked to an air-filled tube 12 which supports the submerged seismic guns 14. The tube is flexible in the lateral direction. Numeral 8 denotes the tow cable and umbilical 9, whereas the tow cable is fixed at end 11 of bar 13. As further disclosed in FIGS. 3 and 4, the head 10 has a float unit 16 with deflector wings 18, 18′ underneath. The tube 12 is fixed on a hinge 20 at the rear of float unit 10.

[0032] Adjusting the head of float 10 angle of attack in the water is performed by adjusting the length 7 between 11 and fixing point 15. FIG. 5a shows a wire 30 fixed at bar 11/13 running on wheel 32 to a reel 34 which in one embodiment can be motorized, controlled from vessel. Another solution is that the wire runs on wheel 36 and further to the vessel as indicated by numeral 38, pulled from the vessel 2 by an on-board winch 39.

[0033] The wire 30 may in another embodiment, be pulled by a hydraulic or electric actuator 42 as indicated in FIG. 5b.

[0034] Outward lateral force, illustrated by arrow 50, and movement of deflector head 10 is created by force of the water from forward pull through the water. Moving the deflector head laterally inward, illustrated by arrow 51, is done by pull of wire 30 by any of the shown embodiments.

[0035] FIG. 6 shows an embodiment utilizing an actuator 43 without use of wire. A bar 23 is hinged at point 21 to head float and deflector unit 10 and to tow 8. An actuator 43 is connected to bar 23 and unit 10. Powering the actuator 43, changes the distance 7′ between unit 10 and bar 23 and the angle of head float 10 and attack of deflector wings.

[0036] FIG. 7 illustrates the remote control system of the invention. Float unit 1(10/12) as illustrated by FIGS. 5a and 5b, show embodiments using a reel 34 or actuator 42/43 for steering of the float head 10. The reel 34 and actuator 42/43 are connected to a local control unit (relay) 60 and sensor 61, the latter for reading of angle of attack. Power 64 is provided directly from vessel or locally from battery 66. Master control unit 68 of the system is placed on vessel and connected with float 1 by cable or a wireless radio system. Also, a position detector 70 is placed on float 1, for the positioning of float within the towed array.

[0037] With reference to FIGS. 5a and 7, it is understood that the float steering mechanism using remote wire pull from vessel, also will have a sensor and position detector.

[0038] An embodiment using a hydraulic system will have a similar set up, the electric power system exchanged with hydraulic hoses, as will be obvious for anyone familiar with this art.

[0039] The invention therefor by these disclosures enables adjusting and keeping a desired position of a source array during the tow and operation.

[0040] The invention described can be subject to modifications and variations without thereby departing from the scope of the inventive concept as disclosed with reference to the drawings and further stated in the claims. To the extent that certain functional elements can be replaced by other elements to enable the same function to be performed by the various embodiments disclosed, such technical equivalents are included within the scope of the invention.