Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
  • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
  • B63B21/00—Tying-up; Shifting, towing, or pushing equipment; Anchoring
  • B63B21/56—Towing or pushing equipment
  • B63B21/66—Equipment specially adapted for towing underwater objects or vessels, e.g. fairings for tow-cables
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
  • G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
  • G01V1/02—Generating seismic energy
  • G01V1/04—Details
• • 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
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
  • G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
  • G01V1/38—Seismology; Seismic or acoustic prospecting or detecting specially adapted for water-covered areas
  • G01V1/3817—Positioning of seismic devices
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
  • G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
  • G01V1/38—Seismology; Seismic or acoustic prospecting or detecting specially adapted for water-covered areas
  • G01V1/3817—Positioning of seismic devices
  • G01V1/3826—Positioning of seismic devices dynamic steering, e.g. by paravanes or birds
• • 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
  • G01V2001/207—Buoyancy

Definitions

• the present invention relates to a marine seisnnic source. More specifically the invention relates to a marine seismic source comprising one or more seismic signal transmitters that are suspended from a float buoy.
• seismic sources such as acoustic sources
• shock waves transmitters are used to produce shock waves under water.
• the shock waves propagate through the water and into the subsea formations.
• Changes in density, composition etc. of the subsea formation causes reflection of Shockwaves which are detected and used as a basis for analysing rock formations to see if the formations may include oil or gas.
• a common way of producing the necessary shock waves is to use air guns to produce the shock waves.
• the air guns are normally arranged as an array suspended below a
• the seismic transmitter source system is towed by specialized vessels, and are connected to the vessel by a towing cable and an umbilical or combined towing cable and umbilical.
• the umbilical comprises one or more pneumatic supply line(s) for providing pressurized air to the air guns and for any additional use of pressurized air for the towed units comprising a float connected to gun arrays.
• the umbilical may additionally comprise control lines and/ or power lines, for controlling the seismic transmitter source system and/ or for providing power for the operation of the seismic transmitter source system.
• the gun array is suspended below the float in suspension lines at a depth below the float, the depth being determined by means of suspension lines connecting the float and the gun array.
• the suspension lines may have a predeternnined length, or the length may be adjusted during operation.
• US 5144588 relates to a seismic transmitter system having lines that are not adjustable, whereas US 4831599 relates to a system where the lines are adjustable during operation.
• US 4831599 relates to a system comprising a float that is not flexible, whereas the floater according to US 5144588 is flexible.
• US 4831599 is an example of a floater connected to gun arrays, where the distance between the floater and the gun array may be adjusted by means of winch drums connected to a common axis operated by a pneumatic motor.
• US5144588 relates to a flexible float comprising a plurality of air tight chambers where pressurized air is continuously introduced into an end chamber and is allowed to pass to the remaining chambers via one way check valves to ascertain that the required air pressure is kept in case of an air leak in any of the chambers.
• One object according to the present invention is to provide flexible float for gun arrays, which allows for adjusting the line lengths for a flexible float without recovery of the array.
• a further object is to provide a flexible float for gun arrays allowing individual control of the line length.
• Yet an object is to provide a solution for draining water from such a flexible float for gun arrays. It is also an object to provide means for safer handling of flexible arrays during deployment and recovery of the float and gun array. Assure no manual handling of pressurized air guns on back deck needed (today air gun must be pressurized during recovery to avoid flooding of air guns, and recovery involves manual handling in slipway). [0009] It is also an object to reduce down time by reducing the risk of damage to sensitive equipment especially during deployment and recovery of the float and gun array.
• the present invention relates to a flexible float for a marine seismic source, the flexible float comprising a head member, a plurality of connection members and a tail member, where the head member, connection members and tail member are connected by tubular flexible float members to make a flexible elongated float, where
• suspension lines and a steering line are connected to the connection members and head member, wherein a pneumatic cable for providing pressurized air to the flexible float is connected to the tail member, where air hoses and air tubes are arranged to deliver pressurized air to each of the connection members and the head member, and where each of the connection members and head member comprises one or more air operated winch for adjusting the length of the suspension lines and the steering line.
• a flexible float including means for adjusting the length of the suspension lines gives both the advantages for the flexible floats, and of the adjustability of the lines earlier known from rigid floats, allowing both adjustment of the length of the lines during operation, but most important allowing adjusting the length of the lines in connection with deployment and rescue of the float and gun arrays.
• the lines are shortened to control the float and gun array as a single body which makes it easier to handle and to lift the body out of water before bringing the array onboard.
• air gun pressure may be released away from personnel before bringing the gun array onboard.
• the float and gun array may be lifted and away from personnel so that the air guns may be pressurized before deploying the float and gun array.
• each connection member is closed at one end and open in the opposite end, so that one connection member and one adjacent flexible float member form a fluid tight section. Separation of the inside of the float in a plurality of fluid tight sections results in a float that is less vulnerable to damage, as the float will still float even if one section is damaged and water leaks into the section.
• the winches in each of the connection and head members are individually controlled. Individually controllable winches makes it possible to adjust the length of the individual lines independent of each other, depending on the demand.
• connection members and the head member additionally comprise overpressure valves to release
• the pneumatic motors are preferably arranged into the inner of the head or connection bodies to protect the pneumatic motors from the seawater and exposure to physical damage.
• the exhaust gas form the pneumatic motors is then released inside the one of the individual sections into which the inner of the float is sectioned.
• overpressure valves are arranged.
• a draining tube is connected to the
• overpressure valve at a first end and where the other end of the draining tube is arranged to drain water from the members in question.
• Connecting the overpressure valve to a draining tube arranged to drain water collected inside the individual sections of the float is forced out of the overpressure valve in front of any air to be released from the overpressure valve, and will cause draining of the section.
• the present invention relates to a marine seismic source comprising a series of seismic signal transmitters or groups of transmitters in a gun array that are connected to each other in a relative spaced relationship arranged to be towed by a vessel in a submerged position via a tow line or a combined umbilical and towline, where the seismic signal transmitters are pneumatic operated and receive pressurized air from the vessel through the umbilical, and where depth lines are arranged between the gun array and a longitudinal flexible float body so that the gun array is suspended in the depth lines from the float body when the seismic source is in use, wherein the float is a flexible float as described above.
• Figure 1 is a side view of marine seismic source including flexible floats according to the present invention
• Figure 2 is a length section through a head section of the flexible float in fig. 1 ;
• Figure 3 is a length section through a mid-section of the flexible float in fig. 1 ;
• Figure 4 is a length section through a tail section of the flexible float in fig. 1.
• Figure 1 is a side view of a seismic source system 1 according to the
• a flexible float 2 connected to a gun array 3 comprising a series of seismic signal transmitters or groups of transmitters connected to each other in a relative spaced relationship by means of connecting elements 15.
• the gun array 3 is connected to the flexible float 2 by means of suspension lines 4, a steering line 5 and a pneumatic cable 6.
• the seismic source system 1 is connected to a not illustrated seismic
• the umbilical or combined umbilical and towing cable comprises a pneumatic tube for providing compressed air from the seismic vessel for operation of air guns 8 arranged in the gun array 3, and additional air operated equipment as will be further described below.
• the umbilical may also comprise power lines and/or signal lines for providing electrical power and/or control signals, respectively, from the seismic vessel to the seismic source system.
• the flexible float 2 comprises a plurality of flexible float sections 1 1
• the flexible float sections 1 1 are tubular elements made of a flexible polymer material.
• a presently preferred material is polyester reinforced rubber, e.g. a seismic tube delivered by Trelleborg (Sweden).
• the head member 10, the connector members 12 and the tail part 13 may be produced of hard plastic materials, such as polyethylene (PE) or other convenient plastic material, metal or a combination of metal and plastic materials.
• PE is the preferred material for the head member 10, connector member 12 and tail member 13.
• the head member 10, connector members 12, and tail part 13 are connected to the flexible float sections by means of connectors 20, 30, 31 , 40 being designed to be connected to the adjacent flexible float section 1 1.
• the connectors 20, 30, 31 , 40 are preferably designed as hose nipples being adopted to put into an open end of the tubular flexible float section 1 1 , and to be fasten thereto by means of a not shown clamp.
• connection members 12 are preferably closed at one end to divide the flexible float into separate fluid-tight compartments as will be described in detail below.
• the head and tail members 10 and 13 are open into the flexible float section. I.e. each flexible float section 1 1 is open into either a head member, a tail member or a connection member as will be described further below.
• the tail member 13 is connected to one end of a flexible float section 1 1 in that the connector 40 is inserted into one end of the flexible float section 1 1.
• a clamp is arranged to secure the connection and to avoid that the connection is loosened unintentionally.
• the tail member comprises preferably a mainly tubular main body 41 that may be partly filled with shock absorbing foam 47 surrounding a battery 42 and any other vulnerable equipment.
• the battery is provided to provide necessary power for operation of a radio-link, and valves and other controlling equipment in the flexible float 2.
• a sealable access hatch 44 is arranged at an aft end wall 48 of the tail member for getting access to equipment inside the tail member, such as a battery 42 and a radio link 43 for wireless remote control of the winches in the flexible float 2.
• equipment inside the tail member such as a battery 42 and a radio link 43 for wireless remote control of the winches in the flexible float 2.
• the skilled person will understand which electrical connections / cables etc., that are necessary for controlling the winches in the flexible float 2 and the control means described herein.
• a hose connector 46 is arranged to the tail member 13 for connection to the pneumatic cable 6 mentioned above.
• the pneumatic cable 6 is connected to the umbilical to provide pressurized air to the flexible float.
• the hose connector also provides a weak link for the pneumatic cable that will break in an accident to avoid damaging equipment that is more valuable.
• the connector is connected to an internal pneumatic hose 49 for internal distribution of the pressurized air.
• a non-return valve 45 is provided to avoid leakage of air from the flexible float 2 in case of loss of pressure in pneumatic cable 6, or breakage of the weak link in the connector.
• connection members 12 comprises a connection member housing 32 having two connectors 30, 31 to connect to the flexible float sections 1 1 in the same way as connector 40 of the tail section.
• the above-mentioned internal pneumatic hose 49 is connected to a connection member pneumatic pipe 33 via an air connector 34.
• the illustrated pneumatic pipe 33 runs substantially axially through the housing 32, and is connected to an outgoing pneumatic hose 49'connected via an outgoing air connector 34'.
• the outgoing pneumatic hose 49' is again connected to the next connection body or to the head member. Accordingly, the pneumatic hoses 49, 49' and the pneumatic tubes 33, are arranged to deliver compressed air to all the connection members 12, and to the head section 1 1.
• a control valve 35 is connected to the pneumatic pipe 33 for taking out a part stream of the compressed air according to the demand for pressurized air in the connection member, as will be further described.
• the control valve is again controlled by control signals received from a remote control via the above described radio link 43, or optionally via a not shown control cable included in the umbilical 7.
• the control valve 35 is arranged to control the flow of compressed air to an air motor 36 connected to a worm gear 37, which again is connected to a gearwheel 39 via a winch chain 38.
• the gearwheel 39 has a common axle with a not shown winch arranged in a winch box 60, for winching in or out the suspension line 4.
• connection members 12 are fluid tight, except for the pneumatic tube running from the tail member to the head member.
• the connector 30 is closed towards the thereto-connected flexible float section, whereas the other connector 31 is open towards the thereto-connected float section.
• the float is separated into a plurality of fluid tight sections
• connection body 12 comprising one connection body 12 and a flexible float section 1 1.
• the connector closest to the head section 10 is closed, whereas the connector closest to the tail section 13 is open.
• the tail section 13 is open into the thereto-connected flexible float member 12. Additionally, the connection member closest to the tail member is open towards the same flexible float member.
• the connect member closest to the tail member and the flexible float member connecting them makes up an aft closed airtight section and the pressure within this aft closed airtight section is controlled by the entry of air into the aft connection section.
• any water leaked into the tail member, the aft connection member, or the flexible float member connecting them may be removed via the described overpressure valve 61 and draining tube 62 in the aft connection member.
• each air motor 36 is released into the inner of such a fluid tight section.
• An overpressure valve 61 is provided in each connection body to release the overpressure thereby created in the fluid tight section.
• An draining tube 62 is preferably provided from the overpressure valve 61 to the lowermost point in the fluid tight section. Any water leaked into the flexible float section 1 1 or the connection body 12 will therefore be withdrawn from the flexible float section and the connection body at the same time as the overpressure is released through the overpressure valve 61. Water that has managed to leak into the floater may therefore be drained. If no action is required by the winch, the winch may be operated to hoist and thereafter lower the suspension lines 4 repeatedly to build up an overpressure to force the water out through the overpressure valves in the connection bodies.
• the head member 10, see figure 2 is designed to reduce the resistance of the floater 2 through water during towing and for steering the floater in the required direction.
• One or more lines 4, 5 are connected to the head member.
• two suspension lines 4, and one steering line 5 are connected to the illustrated head member 10.
• the suspension lines 4 are connected to the gun array 3, se figure 1 , whereas the steering line is connected to the umbilical or a towing cable at a distance to the gun array 3. Adjustment of the length of the steering line 5 may be used to control the direction of the head member relative to the direction of the umbilical or towing cable.
• the head member 10 is connected to a flexible float member 10 by a
• Control valves 22, 22', 22" are connected to respective pneumatic motors 23, 23', 23" for operating winches as described for the connection bodies 12.
• Each control valve is individual controllable to be able to operate the pneumatic motors independent of each other for individual regulation of the length of the respective rope, i.e. suspension lines 4 and steering line 5.
• pneumatic motors 23, 23', 23" are connected to worm gears 24, 24', 24", which again is connected to the respective winches via gearwheels 25, 25', 25" via winch chains 26, 26', 26", in a way corresponding to the description of the operation of the winches with reference to figure 3.
• An overpressure valve 27 is arranged in the head section to release
• the overpressure valve 27 is connected to an draining tube 28 for removing any water leaked into the head member 10 and/or the thereto- connected flexible float member, as described with reference to
• the head member is open towards the thereto-connected
• umbilical and towing cable 7 or to a towing cable and is directed downwards and forwards in the direction towards the seismic vessel to point the floater in the direction of movement.

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• Life Sciences & Earth Sciences (AREA)
• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Remote Sensing (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Environmental & Geological Engineering (AREA)
• Geology (AREA)
• Acoustics & Sound (AREA)
• General Physics & Mathematics (AREA)
• Geophysics (AREA)
• Oceanography (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• Ocean & Marine Engineering (AREA)
• Vibration Prevention Devices (AREA)
• Laying Of Electric Cables Or Lines Outside (AREA)

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Citations (5)

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• 2014
  • 2014-02-27 NO NO20140257A patent/NO337413B1/no not_active IP Right Cessation
• 2015
  • 2015-02-17 WO PCT/EP2015/053295 patent/WO2015128221A1/en active Application Filing

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