Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
  • G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
  • G01V1/16—Receiving elements for seismic signals; Arrangements or adaptations of receiving elements
  • G01V1/20—Arrangements of receiving elements, e.g. geophone pattern
  • G01V1/201—Constructional details of seismic cables, e.g. streamers

Definitions

• This invention relates to arrays of filamantary form.
• the invention is particularly but not exclusively concerned with towable arrays whereby water-bome sound waves generated for geophysical survey purposes may be sensed.
• One object of the invention is to provide an array of filamentary form which is of substantially IBSS lateral cross-section than presently known arrays.
• an array of filamentary form comprises a body housing a central, longitudinally-extending reinforcement member and a plurality of sensors distributed within the body of the array, in the proximity of the outer surface thereof,wherein said centrally-disposed reinforcement member serves to convey signals emitted by the sensors.
• the centrally-disposed reinforcement member may also serve to conduct electrical power to the sensors.
• the central member may be formed and constructed 90 as to accept towing loads applied to the array.
• Figure 2 is a fragmentary side view, in medial section, of the array
• Figure 3 is a view similar to that illustrated by Figure 2 and shows a modification.
• a water-borne sound-wave sensing array 1 of filamentary form is shown being towed through water 2 by a marine craft comprising a surface vessel 3.
• the array 1 is towed through the water for geophysical survey purposes, being used to sense sound waves resulting from applying shock loads to the sea bed.
• the array 1 is connected to a towing cable 4 by way of a vibration isolation coupling 5.
• a rope tail 6, which reduces any tendency for the array to "snake”, is normally (but not necessarily) connected to the rear end of the array 1 by way of another vibration isolation coupling 5.
• the array 1 comprises a cylindrical body 10 housing a central, longitudinally-extending reinforcement member 11, which, in this example, is formed and constructed as a strain member so as to accept towing loads 16 applied to the array.
• a plurality of sensors 12 is distributed within the body 10 of the array, in the proximity of the external surface 13 thereof. (As used herein, the term "proximity" is intended to mean near or at the external surface of the array).
• the sensors 12 comprise hydrophones, although alternatively, or in addition, the array may carry devices whereby, for example, water depth of the array, ambient water temperature and towing loads may be sensed.
• the array body 10 is of circular cross-section, viewed normal to its central axis, which axis is coicident with the longitudinal axis 17 of the central member 11, which is also of circular cross-section.
• the central, tow-load accepting reinforcement/strain member 11 of this example comprises a copper-clad, multi-strand wire rope, enclosed within a sheath 14 of dielectric material. (Polyethylene).
• the dielectric sheath 14 is enclosed within a screening structure, comprising a copper braid 15.
• the braid 15 is enclosed by a first inner sheath 20, which is itself enclosed by a second inner sheath 21.
• P.T.F.E. tape 22 is wound around the sheath 21 and the sheaths 20, 21 and tape 22 are enclosed within first and second sheaths 23, 24.
• the sheaths 20, 21, 23, 24 are all of plastics material, sheaths 20, 21 being of polyurethane and sheaths 23, 24 of polyethylene.
• Buoyancy tubes 25 of NYLON are disposed in grooves formed in the bore of the sheath 23.
• the sheath 14, braid 15 and sheaths 20, 21, 23, 24 are all of circular cross-section, viewed normal to the central axis of the array body 10, and are thus all co-axially disposed.
• the sensors 12 are set in modules or beds 30 of polyurethane material, which material serves as an acoustic coupling medium with the ambient sea water.
• Decoupling material 31 acoustically isolates the beds 30 from surrounding portions of sheaths 21, 23, 24 of array body 10.
• the outer surfaces 32 of the sensors 12 are near (say 2.0mm) to the external surface 13 of the body 10.
• Conductor leads 33 connect the sensors 12 and/or associated electronic equipment with the central reinforcement/strain member 11 which also serves as a databus whereby output signals emitted by the sensors are conveyed (via the copper cladding of the member 11, and/or the member 11 itself, the towing cable 4 and slip rings 34) to monitoring and power supply equipment 35 carried by the towing vessel 3.
• the centrally disposed member 11 is also used to convey electrical power to the array 1.
• the central member 11 can be clad with an alternative to copper.
• a silver coating can be used.
• Figure 3 illustrates a modification wherein the array is provided with a copper braid 40 co-axially disposed between the centrally-disposed member 11 and the surrounding dielectric sheath 14, thus embracing the member 11 closely.
• the braid 40 which can be considered part of the central member 11, is also used to convey output signals from the sensors 12 and/or to convey electrical power within the array.
• the invention provides a compact array of substantially reduced lateral cross-section (say 30.0mm diameter), compared with presently known arrays, thus, for example, reducing drag forces, weight, volume and cost.
• the invention is not, however, confined to arrays intended to be towed through water by marine craft, or even towed at all.
• Arrays according to the invention may be carried by various forms of transport. They may also be used in static modes, for example in moored, upright attitudes, or horizontally disposed, resting on, and secured to, the sea bed.

Landscapes

• Physics & Mathematics (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Environmental & Geological Engineering (AREA)
• Geology (AREA)
• Remote Sensing (AREA)
• General Life Sciences & Earth Sciences (AREA)
• General Physics & Mathematics (AREA)
• Geophysics (AREA)
• Geophysics And Detection Of Objects (AREA)
• Transducers For Ultrasonic Waves (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=10632288

Family Applications (1)

Country Status (4)

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Family Cites Families (7)

• 1988
  • 1988-02-24 GB GB8804314A patent/GB2215461B/en not_active Expired - Lifetime
• 1989
  • 1989-02-23 AU AU33551/89A patent/AU3355189A/en not_active Abandoned
  • 1989-02-23 WO PCT/GB1989/000186 patent/WO1989008270A1/en not_active Application Discontinuation
  • 1989-02-23 EP EP19890904152 patent/EP0409863A1/de not_active Withdrawn

Non-Patent Citations (1)

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