EP0134804A1 - Dispositif dans un cable d'hydrophone pour des releves sismiques marins - Google Patents

Dispositif dans un cable d'hydrophone pour des releves sismiques marins

Info

Publication number
EP0134804A1
EP0134804A1 EP84900648A EP84900648A EP0134804A1 EP 0134804 A1 EP0134804 A1 EP 0134804A1 EP 84900648 A EP84900648 A EP 84900648A EP 84900648 A EP84900648 A EP 84900648A EP 0134804 A1 EP0134804 A1 EP 0134804A1
Authority
EP
European Patent Office
Prior art keywords
cable
hydrophone cable
vessel
hydrophone
transmission elements
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP84900648A
Other languages
German (de)
English (en)
Inventor
Borre B. Ulrichsen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Kongsberg Gruppen ASA
Original Assignee
Kongsberg Vapenfabrikk AS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Kongsberg Vapenfabrikk AS filed Critical Kongsberg Vapenfabrikk AS
Publication of EP0134804A1 publication Critical patent/EP0134804A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
    • G01V1/38—Seismology; Seismic or acoustic prospecting or detecting specially adapted for water-covered areas
    • G01V1/3817—Positioning of seismic devices
    • G01V1/3835—Positioning of seismic devices measuring position, e.g. by GPS or acoustically

Definitions

  • the present invention relates to a device in a hydrophone cable which is adapted for marine seismic surveys and is towed through the water behind a vessel, the cable comprising means for detecting echo signals from the sea bed and various layers therebelow.
  • Such hydrophone cables which are used in connection with seismic methods for mapping possible hydrocarbon sources below the sea bed, can be approx. 3000 meters long and be towed at a depth of approx. 10 meters. At a distance of approx. 100 meters behind the vessel there are also towed so-called air guns, the air guns firing shots according to an appropriate programme.
  • the sound waves which are transmitted from the air guns are reflected from the obstacles against which they may impinge below the water surface, as well as from the sea bed and various layers therebelow.
  • the echo signals which return to the hydrophone cable are detected by a series of hydrophones which are arranged along the cable, and which after a suitable conversion transfer the echo signals via the cable to an appropriate processing device on the towing vessel.
  • the seismic methods can be carried out by firing lines having a mutual distance of approx. 50 meters, and the inter ⁇ vals between the shots from the air guns correspond to a distance of approx. 25 meters, for thereby achieving a very fine net of squares.
  • the hydrophone cable also comprises a plurality of compasses which indicate the form of the cable during the towing operation, and which thus constitute reference points for the line to which a sweep operation is to be referred.
  • compasses suffer from some disadvantages, the direction indication of the compasses being apt to give significant errors, since the hydrophone cable has a substantial extension.
  • the compass section of the cable is often signi ⁇ ficantly larger in diameter than the cable itself, and will therefore in itself be prone to generate noise.
  • the compasses necessitate a substantial number of surplus connections in the cable, which in itself is unfavourable.
  • the calibrating routine for the compasses is very sophisticated, and it is not unusual that several days are used for effecting the calibration and making all of the compass sections operable. In case magnet compasses are used, these may easily be disturbed by the magnetic fields occurring during the measuring work itself.
  • the object of the present invention is to arrive at a device in a hydrophone cable which with simpler and less expensive means can determine the position of the hydrophone cable, the detection of the hydrophone cable's position being of importance not only during the sailing of the measuring lines itself, but also during the turning programmes after a terminated line, in connection with which significant extra distances have to be sailed before a new line is entered for thereby ensuring that the cable has a shape as straight as possible.
  • the object is achieved according to the invention in a device which is characterized in that it comprises a trans ⁇ mission system which is adapted to determine the position of the hydrophone cable, and which comprises transmission elements provided outside the hydrophone cable itself.
  • a trans ⁇ mission system which is adapted to determine the position of the hydrophone cable, and which comprises transmission elements provided outside the hydrophone cable itself.
  • the transmission elements which are included in the proposed transmission system can either be stationarily anchored, or they may be provided on bodies floating more or less freely in the water. In the latter case the bodies carrying the transmission elements can then be connected to a continuous connection means facilitating the collection of the bodies after a measuring period.
  • the transmission elements serving to transfer the position signals to or from the hydrophone cable can be provided on one or more bodies which are towed behind the vessel, the bodies being towed separately or in groups, and the bodies substantially being arranged along a straight line.
  • the bodies carrying the transmission elements can be affixed to or be constituted by a separate towing line having a relatively small diameter, the towing line being provided with stretching means for achieving an approximately straight run.
  • the towing line with the transmission element carrying bodies can then extend at least along the overall length of the hydrophone cable.
  • the towing line itself can be adapted for transmission of substantially longitudinal acoustic waves which are received by the hydrophone cable.
  • the transmission elements can comprise means for receiving position signals which are transmitted from signal elements in the hydrophone cable.
  • the transmission of position pulses can take place to or from the vessel, for example via radio or radar, and it is thereby achieved an electromagnetic positioning system which works independently of the seismic hydrophone system.
  • the transmission elements indicating the position of the cable can for example be con ⁇ stituted by for example reflectors which are attached to the towing line, or with a suitable spacing are attached to the hydrophone cable and glide thereabove in or close to the surface by means of appropriate buoyancy means.
  • the position of the reflectors can .then be determined by means of antennas mounted for example on the vessel itself or on paravans towed at a distance from the vessel.
  • the position.of the reflectors can be determined by a system gliding above the hydrophone cable, for example wire controlled from the vessel.
  • the above described embodiments for determining the position of the hydrophone cable can in a simple manner be adapted to an adaptive regulating system for manoeuvring both the vessel and the hydrophone cable for thereby achieving a most favourable overall position at any time for covering the measuring area and complete measuring accuracy.
  • the signals from the transmission system can suitably be used for influencing the manoeuvring of the vessel and/or influencing a means on the vessel which can move relative thereto, or influencing means which are provided along the hydrophone cable and in this way aligne the position of the cable relative to the vessel.
  • these means may appropriately be influenced during time intervals in which the hydrophone cable is close to inactive as regards the detection of echo signals.
  • Figure 1 illustrates diagrammatically a plurality of embodiments of the device according to the present invention.
  • Figure 2 is similarly a sketch illustrating further embodiments of the device according to the present invention.
  • FIG. 3 illustrates diagrammatically further embodiments of the device according to the present invention.
  • Figure 4 is a sketch illustrating further embodiments of the present invention.
  • Figure 5 is a sketch illustrating how the hydrophone cable can be influenced in co-operation with the present device.
  • a vessel which is designated by 1 moves along the surface of a larger body of water for surveying the bottom of the body of water and areas there ⁇ below, the vessel 1 towing a hydrophone cable 2 which can have an overall extension of for example 3000 meters.
  • the towing of the cable 2 takes place preferably at a depth of 10 meters, and an even depth is sought maintained by means of for example active fins controlling the height direction of the cable, the specific weight of the cable being adjustable on the one hand by means of the paraffin type which is used for filling the cable, and on the other hand by ballast, for example in the form of lead plates arranged therearound.
  • a couple of air guns 3a, 3b said guns being adapted for firing in accordance with a predetermined programme for the transmission of sound waves, which are scattered towards the sea bed and are re ⁇ flected therefrom and from various geological layers there ⁇ below.
  • the reflected sound waves or echo signals are received by the hydrophones which are mounted in the hydrophone cable
  • FIG. 1 there is as a first embodiment of a trans ⁇ mission system for supervising the position of the hydrophone cable 2 depicted a relatively thin steel wire 4 which pre ⁇ ferably has a somewhat longer extension than the hydrophone cable 2 itself.
  • the steel wire 4 can be equipped with a braking plate 5 or a suitable form of a controlled braking device serving to keep the wire in an as straight as possible shape during the towing operation.
  • this may constitute a carrier means for substantially longitudinal mechanical sound waves which are generated at the attachment points at the vessel 1 , the acoustic waves or pulses which follow the wire 4 being registered by the hydrophones in the hydrophone cable 2, since the distance between the wire and the hydrophone cable in the utmost case usually runs to approx. 100 meters.
  • the braking device or the plate 5 at the free end of the wire 4 can be controlled in such a way that it not necessarily finds itself in an extension of the centre line of the ship, but can be swung out in the proximity of the microphone cable, so that the signal communication between the wire 4 and the hydrophone cable 2 is amplified.
  • the wire 4 is relatively thin and is kept under tension, the drift of the wire can be made very small, but it should in connection with the use of acoustic transmission signals be towed in a position below the water surface, so that signal communication with the microphone cable is made as favourable as possible, while at the same time reducing wave noise.
  • the distance between the wire 4 and the cable 2 should be adjusted so that no interference occurs between the means being included in the present transmission system and the hydrophone cable.
  • the acoustic signal generators can also be arranged in the hydrophone cable at the same time as signals therefrom are registered in suitable receivers in elements provided on the wire 4.
  • Still another embodiment of the device comprising a transmission system which is adapted for determining the position of the hydrophone cable and which comprises trans ⁇ mission elements provided outside the hydrophone cable 2 itself, is illustrated in Figure 1 and takes the form of transponders 7a, 7b, which are towed on paravans located approx. 200-300 meters behind the ship and defining an angle of approx. 45°.
  • the signals from the transponders 7a, 7b will at suitable intervals be picked up by the hydrophones in the hydrophone cable 2 and the relative strength and the shape of the signals received by the hydrophone cable 2, will give a picture of the shape and the position of the cable relative to the towing vessel • .
  • the length of the paravan lines must here be adjusted so as to achieve a best possible signal/noise ratio, since longer paravan lines can give a shorter signal path to the hydrophones in the hydrophone cable, but bring the sources of noise closer thereto.
  • the buoys 8a-8n are also equipped with radar reflectors.
  • the buoys are dropped from the vessel when this passes the area to be investigated, and the buoys will of course drift off by stream, wind and waves, but they will not give rise to noise.
  • the transponders in the floating buoys can be adapted for transmission of hydroacoustic signals during given periods of times, preferably during period of times in which the registration of the echo signals is not critical.
  • buoys are dropped at a distance of approx. 500 meters, a number of twenty buoys could cover a sailing line of approx. 10 km in a seismic surveying net.
  • the buoys can preferably be connected by means of a rope 8' which appropriately can slide through an eye in the stem of the bouy until the hydrophone cable has passed by. Thereafter the buoys can be collected in a group and be hauled in during the turning operation for another seismic line. In this period of turning the signal means in the buoys can possibly be reenergized if required.
  • a corresponding system can comprise transponders which instead of floating on the surface of the water are dropped to the sea bed to known bottom positions for therefrom transmitting signals to the hydrophone cable. After use the transponders can be collected by means of a line and be brought to the towing vessel.
  • FIG 3 Still another variant of the transmission system according to the present invention is illustrated in Figure 3, in which reflectors for example in the form of light gass-filled balloons 9a-9n are attached to the hydrophone cable 2 which also in this case is towed behind a vessel 1.
  • the balloons 9a-9n are attached to the hydrophone cable 2 by means of thin, light lines, so that the balloons can be towed at surface positions or at a fair height above the water surface, if required.
  • Such a system including floating or gliding balloons can be made very economically and can be contemplated used as a supplemental system to another transmission and measuring system.
  • the radar equipment on the vessel the position of the various balloon reflectors can be detected, and the detected echo signals from the reflectors will form a picture of the shape and position of the cable behind the towing vessel 1.
  • the radar antenna can be arranged gliding in the air above the vessel 1 , as this appears from Figure 3, the radar antenna here being attached to a gliding drone 11 which is located at a suitable distance and height, behind
  • the drone 11 can suitably be controlled from the vessel 1.
  • the reflector elements can co-operate with means forming a basis line established outside the vessel for thereby avoiding the uncertainty in the angular determi ⁇ nation from a vessel in moving sea.
  • the determination of the position of the buoys or reflec ⁇ tors can also be carried out by means of for example con ⁇ ventional radio and navigation systems, possibly by the system used by the ship itself for the positioning thereof. These systems can be used in addition to the distance and angular determination of the buoys by means of the radar system of the ship.
  • the vessel can be steered automatically in relation thereto, since this steering is also based on an adaptive control system.
  • Such systems render dynamic compensation for wind, current and sea, as well as for the influences to which the vessel and the hydrophone cable ohterwise are subjected.
  • Contrary to steering the vessel substantially along straight heading lines it is possible by co-operating the shape of the hydrophone cable and the heading of the vessel to obtain a most favourable shape and position of the hydrophone cable relative to the desired surveying line in the sailing pro ⁇ gramme.
  • FIG 5 there are diagrammatically illustrated embodi ⁇ ments wherein the vessel 1 towing the hydrophone cable 2 therebeind, is equipped with a suspension 12 which is adapted to influence the cable 2 for thereby either cancelling or resisting the deflections which at any time can occur during the towing operation.
  • the hydrophone cable 2 can be equipped with actuators, for example in the form of a steerable end rudder 13 or steerable fins provided in the longitudinal direction of the cable.
  • steerable fins can pave the way for undesired acoustic noise, since in connection with seismic reflections 'one operates with signal levels in the magnitude range of + 5 microbar.
  • the steering fins or the actuators can be in ⁇ serted in such a way that they are active during given time intervals between the shots from the air guns, in which the accuracy, as regards the measuring technique, is of less importance.
  • the control of the fins or the actuators will be excluded in the periods in which the feeble reflexes from the deep formations below the seabed are re ⁇ ceived, since during these periods of time a strongest possible reduction of all possible sources of noise is desired for the achievement of a most favourable signal/noise ratio.

Abstract

Dispositif dans un câble d'hydrophone lequel, en combinaison avec des relevés sismiques, est remorqué dans l'eau derrière un navire, le câble d'hydrophone comprenant un organe permettant de détecter les signaux d'échos qui sont réfléchis par le fond de la mer ainsi que par les différentes couches sous le fond. Afin d'améliorer la détermination de la position du câble d'hydrophone, lequel câble peut mesurer environ 3000 mètres, on propose un système de transmission comprenant des éléments de transmission disposés à l'extérieur du câble d'hydrophone lui-même, les éléments de transmission servant à déterminer la position du câble d'hydrophone par rapport aux éléments. Dans un mode simple de réalisation du dispositif les éléments de transmission sont fixés à une ligne séparée de remorquage (4) ou sont constitués par celle-ci, la ligne (4) possédant un diamètre relativement petit et étant équipé d'un tendeur (5) pour obtenir une course relativement droite. Dans un mode alternatif de réalisation les éléments de transmission peuvent être réalisés sous la forme de réflecteurs (9a-9n) d'ondes de préférence électromagnétiques, par exemple sous la forme de ballons remplis d'un gaz léger et pouvant être fixés au câble d'hydrophone à l'aide de câbles minces et légers, de manière à pouvoir remorquer ces ballons à la surface ou au-dessus de la surface de l'eau. Les éléments de transmission peuvent être également compris dans un système conventionnel radio et de navigation, éventuellement en combinaison avec le système utilisé par le navire de remorquage pour son positionnement, en plus de la détermination de la distance et de l'orientation à l'aide du système radar du navire. Les éléments de transmission peuvent également être compris en tant qu'éléments d'un système adaptatif de commande pour la commande combinée du navire et du câble d'hydrophone.
EP84900648A 1983-02-02 1984-02-01 Dispositif dans un cable d'hydrophone pour des releves sismiques marins Withdrawn EP0134804A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NO830358A NO830358L (no) 1983-02-02 1983-02-02 Anordning ved en hydrofonkabel for marinseismiske undersoekelser
NO830358 1983-02-02

Publications (1)

Publication Number Publication Date
EP0134804A1 true EP0134804A1 (fr) 1985-03-27

Family

ID=19886940

Family Applications (1)

Application Number Title Priority Date Filing Date
EP84900648A Withdrawn EP0134804A1 (fr) 1983-02-02 1984-02-01 Dispositif dans un cable d'hydrophone pour des releves sismiques marins

Country Status (4)

Country Link
EP (1) EP0134804A1 (fr)
JP (1) JPS60500383A (fr)
NO (1) NO830358L (fr)
WO (1) WO1984003153A1 (fr)

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NO161090C (no) * 1983-04-29 1989-06-28 Norske Stats Oljeselskap Fremgangsmaate til posisjonsbestemmelse av marin seismisk mottagerkabel.
FR2601143B1 (fr) * 1986-07-01 1988-12-02 Geophysique Cie Gle Procede et systeme de localisation et de correction d'orientation d'un objet mobile autonome et d'un objet mobile non autonome
FR2606158B1 (fr) * 1986-10-31 1989-04-07 Inst Francais Du Petrole Procede et dispositif pour determiner la position d'objets immerges par rapport au navire qui les remorque
US5790472A (en) * 1996-12-20 1998-08-04 Western Atlas International, Inc. Adaptive control of marine seismic streamers
NO321016B1 (no) * 2001-01-24 2006-02-27 Petroleum Geo Services As System for styring av kabler i et seismisk slep og hvor noen av kablene har kontrollenheter innrettet for a male og rapportere om sine posisjoner
GB2394045B (en) * 2002-10-11 2006-07-26 Westerngeco Seismic Holdings Method and apparatus for positioning of seismic sensing cables
GB2394049B (en) * 2002-10-12 2006-07-26 Westerngeco Seismic Holdings Method and apparatus for determination of an acoustic receivers position
US7518951B2 (en) * 2005-03-22 2009-04-14 Westerngeco L.L.C. Systems and methods for seismic streamer positioning
US8391102B2 (en) * 2005-08-26 2013-03-05 Westerngeco L.L.C. Automatic systems and methods for positioning marine seismic equipment
US7400552B2 (en) 2006-01-19 2008-07-15 Westerngeco L.L.C. Methods and systems for efficiently acquiring towed streamer seismic surveys
US8488409B2 (en) 2007-05-17 2013-07-16 Westerngeco L.L.C. Acquiring azimuth rich seismic data in the marine environment using a regular sparse pattern of continuously curved sail lines
US8559265B2 (en) 2007-05-17 2013-10-15 Westerngeco L.L.C. Methods for efficiently acquiring wide-azimuth towed streamer seismic data
US9857491B2 (en) 2008-05-15 2018-01-02 Westerngeco L.L.C. Multi-vessel coil shooting acquisition
US8681580B2 (en) 2008-05-15 2014-03-25 Westerngeco L.L.C. Multi-vessel coil shooting acquisition
US9052411B2 (en) 2008-06-13 2015-06-09 Westerngeco L.L.C. Method to determine the deviation of seismic equipment from a planned curved path
US9594181B2 (en) 2008-06-13 2017-03-14 Westerngeco L.L.C. Filtering and presentation of heading observations for coil shooting
US8391101B2 (en) 2008-07-03 2013-03-05 Conocophillips Company Marine seismic acquisition with controlled streamer flaring
US8483008B2 (en) 2008-11-08 2013-07-09 Westerngeco L.L.C. Coil shooting mode
US8681581B2 (en) 2009-12-30 2014-03-25 Westerngeco L.L.C. Randomization of data acquisition in marine seismic and electromagnetic acquisition
US8711654B2 (en) 2009-12-30 2014-04-29 Westerngeco L.L.C. Random sampling for geophysical acquisitions
US8792297B2 (en) 2010-07-02 2014-07-29 Pgs Geophysical As Methods for gathering marine geophysical data
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JP6849999B2 (ja) * 2017-04-25 2021-03-31 国立大学法人東京海洋大学 海底地質探査システム、海底地質探査方法および海底地質探査プログラム
CN112965014B (zh) * 2021-03-04 2022-09-02 哈尔滨工业大学 一种飞机机械结构变化引起磁干扰的补偿方法及装置

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Also Published As

Publication number Publication date
NO830358L (no) 1984-08-03
JPS60500383A (ja) 1985-03-22
WO1984003153A1 (fr) 1984-08-16

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