`
`
`Ex. PGS 1004
`
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`
`EX. PGS 1004
`
`
`
`
`
`

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`O
`Umted States Patent
`
`[19]
`
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`
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`‘
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`1
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`
`1
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`U8005790472A
`
`[11] Patent Number:
`
`5,790,472
`
`Workman et a1.
`[45] Date of Patent:
`Aug. 4, 1998
`
`
`[54] ADAPTIVE CONTROL OF MARINE SEISMIC
`STREANIERS
`
`[75]
`
`Inventors: Ricky L. Workman; Ronald Edward
`Chambers. both of Houston. Tex.
`.
`'
`[73] Asngnce: Western Atlas International, Inc-.
`Houston. Tex.
`
`[21] Appl. No.: 771,949
`.
`_
`Dec. 20, 1996
`F1led.
`Int. Cl.6 ....................................................... G01V 1/38
`
`..
`.. 3157/19; 367/16
`13.3. C1.
`................
`
`field of Search .....
`367/10613337176112/22;
`‘
`‘
`’
`
`[22]
`[5 1]
`[52]
`[58]
`
`[55]
`
`References Cited
`U.s. PATENT DOCUMENTS
`1/1976 Cole ...................................... 340,7 PC
`3,931,608
`7/1977 waters
`..... 144/245
`4,033,273
`5/1978 Inja et 31. ........... 340/7
`4,087,780
`4,1814% 2/1980 Delignieres
`367/19
`4,404,664
`9/1983 Zachafiadis
`367/19
`:figggg;
`3513:: 221-106“ ital“.
`- 112%:
`1
`y e
`.
`.....
`4,309,005
`2/1989 Connselman
`...... 342/352
`
`.. 114/246
`4,890,568
`1/1990 Dolengowski
`
`4,912,682
`3/1990 Norton, Jr. et a].
`367/19
`7/1991 Rouquene ............................... 367/130
`5,031,159
`
`
`
`'-
`...
`
`5,353,223
`5,443,027
`5,532,975
`
`
`.......................... 364/421
`10/1994 Norton et a1.
`..
`114/244
`8/1995 Owsley et a1.
`7/1996 Elholm ...................................... 367/16
`
`OTHER PUBLICATIONS
`M. Schoenberger and J. F. Misfud, “Hydrophone Streamer
`Noise”, Geophysics. vol. 39. No. 6, pp. 731—793.
`Franklyn K. Levin in “Short Note: The Efiect of Binning on
`Data from a Feathered Streamer”. Geophysics. vol. 49. No.
`8. pp. 1386—1387.
`Mamdouh R. Gadallah. “Reservoir Seismology”. Pennwell,
`1994. pp. 209437.
`Manin et a1.. “Recent Developments in Source and Streamer
`Positioning" First Break vol- 6. pp- 183—188. Jun. 1981.
`Primary Examiner—Ian J. Lobo
`Attorney, Agent, or Firm—James Randall Allen; Charles R.
`SChwePPC
`ABSTRACT
`[57]
`A IHCEhOd for wnmflfing the P0990n and $112113: 0f mafine
`seismic streamer cables, whereby a plurahty of real tune
`signals from a marine seismic data acquisition system and a
`plurality of threshold parameters from an input device are
`received. The real time signals are compared to the threshold
`parameters to determine if the streamer cables should be
`-
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`.
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`'
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`10 Claims, 3 Drawing Sheets
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`Ex. PGS 1004
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`Ex. PGS 1004
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`

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`Compare real
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`
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`
`Ex. PGS 1004
`
`

`

`5,790,472
`
`1
`ADAPTIVE CONTROL OF MARINE SEISMIC
`STREAMERS
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`The present invention generally relates to an improved
`system for contolling the position and shape of marine
`seismic steamers.
`
`2. Description of the Related Art
`During a typical marine seismic survey a seismic vessel
`taverses programmed tacks towing arrays of seismic
`sources and seismic streamer cables. A seismic steamer
`cable normally contains a plurality of hydrophones which
`convert seismic pressure waves. initiated by the sources and
`reflected from the subsurface geologic formations.
`into
`electrical signals which are recorded on a marine seismic
`data acquisition system located on the vessel. Due to the
`increasing use of marine 3-D seismic data. multi—cable
`marine surveys are now commonplace. During a typical
`marine 3-D seismic survey. a vessel may tow as many as ten
`streamer cables. each cable ranging in length between three
`to eight kilometers. As reported by Gadallah in “Reservoir
`Seismology” 1994. pp. 209—237.
`the goal of a normal
`marine 3-D seismic survey is to use these arrays of seismic
`sources and steamer cables to record a highly sampled grid
`of “bins" of subsurface seismic coverage.
`A natural consequence of towing such streamer cable
`configurations in a marine environment is that currents.
`wind. and wave action will deflect the streamer cables from
`their intended paths. Streamer cable drifi is a continuing
`problem for marine seismic surveys. See. for example. US.
`Pat. No. 5.532.975. The ability to control the position and
`shape of the streamer cables is desirable for preventing the
`entanglement of the streamer cables and for avoiding colli—
`sions with offshore hazards such as marine drilling rigs and
`platforms. It is also desirable to have the ability to control
`the position and shape of the steamer cables during marine
`3-D seismic surveys because the 3-D seismic binning pro—
`cess acquires subsurface seismic coverage by combining
`seismic data from different lines. The need for this ability is
`taught by Franklyn K. Levin in "Short Note: The efiect of
`binning on data from a feathered steamer." Geophysics.
`Vol. 49. No. 8. pp. 1386—1387.
`Steamer positioning devices are well known in the art.
`Apparatus. such as those disclosed in US. Pat. Nos. 5.532.
`975. 4.729.333. and 4.463.701. have been devised for
`attachment
`to the front end of steamer cables for the
`purpose of maintaining them at a lateral ofiset
`to the
`pathway of the towing vessel. Steerable tail buoys. as
`described in US. Pat. No. 4.890.568. have also been
`designed for controlling the position of the tail end of towed
`seismic streamer cables. The prior art also discloses streamer
`positioning devices that may be attached externally to the
`streamer cables. For example. devices to contol the lateral
`positioning of steamer cables by using camber-adjustable
`hydrofoils or angled wings are disclosed in U.S. Pat. Nos.
`4.033.278 and 5.443.027. US. Pat No. 3.931.608 describes
`an apparatus. typically known as a “bird”. to control the
`vertical positioning of streamer cables with diving planes
`and a preset depth contol means.
`The use of streamer positioning devices comes at the price
`of introducing increased noise onto the seismic streamer and
`hence into the hydrophones. The areas of greatest noise are
`from those hydrophones which are adjacent to externally
`attached streamer positioning devices. such as depth con-
`trolling birds. This problem has been described by Schoe—
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`65
`
`2
`
`nberger and Misfud. “Hydrophone Streamer Noise"
`Geophysics. Vol. 39. No. 6. pp. 782—784. It is well known
`in the art that noise limits the resolution of a seismic survey.
`Consequently. a maximum allowable hydrophone noise
`level is typically established for each marine seismic sur—
`veying project. When this noise level is exceeded. seismic
`acquisition is usually suspended. resulting in lost time and
`additional cost. Data acquired under such conditions may
`need to be reshot.
`
`Location sensing devices and methods for determining the
`positions of the seismic sources and seismic streamer cables
`are also well known in the art. For example. both a Global
`Positioning System. as described in US. Pat. No. 4.809.005.
`and a network of acoustic elements. as described in US. Pat.
`No. 4.912.682 may be deployed on the vessel. streamer
`cables. and tail buoy. These devices and methods may then
`be used to determine the real time position of the seismic
`sources and seismic streamer cables by computing a network
`solution to a Kalrnan filter. as disclosed by US. Pat. No.
`5.353.223.
`As is known to those familiar with the art of marine
`seismic surveying. during a typical survey a human operator
`monitors the survey’s operational conditions. such as the
`extent of the subsurface seismic coverage. the adequacy of
`the separations between streamer cables. and the proximity
`of the streamer cables to obstructive hazards. When these
`conditions indicate the need to reposition the streamer
`cables. the operator may manually issue commands to the
`various individual streamer positioning devices in order to
`adjust the position and shape of the streamer cable. or order
`the helmsman to redirect the vessel. or suspend data acqui-
`sition.
`
`While the prior art discloses a series of discrete devices
`for locating and controlling the positions of streamer cables.
`it does not teach any method or system wherein these
`individual devices are unified into a single system for
`contolling the position and shape of marine seismic
`streamer cables. Also. the prior art fails to disclose any
`method or system wherein the real time hydrophone noise
`on the steamer cables operates as a constraint on the control
`of the position and shape of marine seismic steamer cables.
`The present invention overcomes the limitations of the
`prior art by providing an improved system for controlling
`the position and shape of marine seismic steamer cables.
`SUMMARY OF THE INVENTION
`
`The present invention is an improved system for contol—
`ling the position and shape of marine seismic steamer
`cables. First. a plurality of real time signals from a marine
`seismic data acquisition system and a plurality of threshold
`parameters from an input device are received. Second. the
`real time signals are compared to the threshold parameters to
`determine if the steamer cables should be repositioned.
`Finally. the steamer cables are repositioned when the real
`time signals exceed the threshold parameters.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 shows a generalized schematic of a marine seismic
`survey system.
`FIG. 2 shows a block diagram of a marine seismic data
`acquisition system in the improved system for contolling
`the position and shape of marine seismic steamer cables.
`FIG. 3 shows a flow chart illustrating certain steps of a
`streamer control processor
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`
`FIG. 1 illustates a generalized schematic of a type of
`marine seismic survey system 01. This system 01 has a
`
`Ex. PGS 1004
`
`Ex. PGS 1004
`
`

`

`3
`
`4
`
`5,790,472
`
`vessel 11. a plurality of seismic sources 12 and a plurality of
`streamer cables 13 under tow behind the vessel 11. and a
`marine seismic data acquisition system 05. which is onboard
`the vessel 11 and connected to the seismic sources 12 and the
`
`streamer cables 13. The seismic sources 12 generate seismic
`pressure waves. Hydrophones (not shown) in the streamer
`cable 13 receive pressure wave signals and send them to the
`marine seismic data acquisition system 05. The marine
`seismic data acquisition system 05 records pressure wave
`signals received from the streamer cable 13. controls the
`seismic sources 12 and the streamer cables 13. and monitors
`the seismic sources 12. the streamer cables 13. and the
`acquisition of subsurface seismic coverage.
`As known to those skilled in the art. streamer positioning
`devices 14. for example birds and tail buoys. may be
`attached to the exterior of the streamer cables 13 for adjust-
`ing the vertical and lateral positions of the streamer cables
`13. The streamer cables 13 include electrical or optical
`cables for connecting the streamer positioning devices 14 to
`individual control and logging systems. for each type of
`device. in the marine seismic data acquisition system 05.
`Typically.
`location sensing devices 15 may be used for
`observing the position of the streamer cables 13 and seismic
`sources 12. The marine seismic data acquisition system 05
`uses these position observations to determine the position of
`the streamer cables 13 and seismic sources 12. As known to
`those skilled in the art. the location sensing devices 15 are
`connected to the marine seismic data acquisition system 05
`by electrical or optical cables within the streamer cables 13
`or by radio transmitter means.
`the interrelationship of the
`Referring now to FIG. 2.
`devices in the marine seismic data acquisition system 05 of
`the preferred embodiment of the present invention is shown.
`As known to those skilled in the art. components of the
`marine seismic data acquisition system 05. on the vessel 11.
`may include a vessel positioning system 20 for determining
`the position of the vessel 11 by satellite navigation. a seismic
`data recording system 18 for recording signals received from
`hydrophones in the streamer cables 13. a seismic binning
`system 30 for determining the subsurface seismic coverage
`during the seismic survey. a network solution system 10 for
`determining the position of the streamer cables 13 and
`seismic sources 12. and a streamer cable controller 16 for
`controlling the streamer positioning devices 14. (For clarity.
`only one streamer cable 13 and one seismic source 12 are
`shown in FIG. 2).
`Typically. the network solution system 10 implements a
`Kalman filter solution on the signals it receives from the
`vessel positioning system 20 and location sensing devices
`15. The network solution system 10 outputs real
`time
`streamer cable shapes. streamer cable positions. and
`streamer cable separations. The seismic binning system 30
`receives these real time signals from the network solution
`system 10. and utilizes them to determine and output real
`time subsurface seismic coverage. The seismic data record-
`ing system 18 is connected to the streamer cables 13 and
`may output real time signals indicating whether or not the
`streamer cables 13 are recording seismic data and real time
`signals of hydrophone noise on the streamer cable 13.
`In the present embodiment of the invention. the marine
`seismic data acquisition system 05 also includes a streamer
`control processor 40 for deciding when the streamer cables
`13 should be repositioned and for calculating a position
`correction to reposition the streamer cables 13. Also in the
`present embodiment of the invention. threshold parameters
`are established for determining when the streamer cables
`should be repositioned Threshold parameters may include a
`plurality of values for: minimum allowable separations
`between streamer cables 13. minimum allowable subsurface
`
`10
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`15
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`20
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`25
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`30
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`35
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`50
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`55
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`65
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`seismic coverage. maximum allowable hydrophone noise
`levels. and minimum allowable separations between any
`streamer cable 13 and any obstructive hazard. A terminal 32
`for entering threshold parameters is connected to the
`streamer control processor 40. Threshold parameters may be
`entered into the streamer control processor 40 before or
`contemporaneously with the acquisition of a marine seismic
`survey.
`The streamer control processor 40 is connected to the
`network solution system 10. the seismic binning system 30.
`the streamer positioning control devices 14. and the seismic
`data recording system 18 and receives the real time signal
`outputs of these systems. The streamer control processor 40
`evaluates these real time signals and the threshold param-
`eters from the terminal 32 to determine when the streamer
`cables 13 need to be repositioned and to calculate the
`position correction required to keep the streamer cables 13
`within the threshold parameters. The streamer control pro—
`cessor 40 is connected to the streamer device controller 16.
`When the streamer cables 13 need to be repositioned. the
`position correction is used by the streamer device controller
`16 to adjust the streamer positioning devices 14 and repo-
`sition the streamer cables 13.
`
`Referring now to FIG. 3 and FIG. 2. the process steps of
`the streamer control processor 40 will now be described. At
`step 41. the streamer control processor 40 determines if the
`streamer cables 13 need to be repositioned by comparing the
`real time signals received from the network solution system
`10. the seismic binning system 30. and the seismic data
`recording system 18 with the threshold parameters received
`from the terminal 32. At step 42. it is determined if any of
`the real
`time signals exceed any threshold parameter
`received from the terminal 32. At step 43. if any such
`threshold parameter is exceeded. a position correction is
`calculated that will reposition the streamer cables 13 back to
`within the threshold parameters. If no signal exceeds any
`threshold parameter. the streamer control processor 40 is
`initialized and restarted at step 44.
`Since streamer positioning devices 14 create noise on
`hydrophones in the streamer cable 13. the present invention
`controls the use of the position correction by determining
`when the hydrophone noise level should lxevent the repo-
`sitioning of the streamer cable 13. Occasionally. towed
`streamer cables encounter “at risk” situations. For example.
`they face the possibility of becoming entangled with each
`other or of colliding with an obstructive hazard. When the
`streamer cables 13 are being repositioned to avoid such at
`risk situations the position correction should be irnple—
`mented without considering the hydrophone noise levels.
`At step 45. it is determined if the position correction is due
`to an at risk situation. If an at risk situation exists. at step 46
`the streamer position correction is sent to the streamer
`device controller 16 for adjusting the streamer positioning
`devices 14 to reposition the streamer cables 13. If an at risk
`situation does not exist. at step 47 it is determined if the
`steamer cables 13 are being used to record seismic data by
`evaluating the real time signals and recorder status from the
`seismic data recording system 18. If the streamers cables 13
`are not being used to record seismic data. at step 46 the
`streamer position correction is sent to the streamer device
`controller 16 for adjusting the streamer positioning devices
`14 to reposition the streamer cables 13.
`.It
`is well known in the art of marine seismic data
`acquisition that hydrophone noise limits the resolution of
`marine seismic surveys. The preferred embodiment of the
`present
`invention constrains the repositioning of the
`streamer cables 13 by evaluating the hydrophone noise level
`of the streamer cables 13 when the streamer cables 13 are
`being used to record seismic data.
`It is also well known in the art of marine seismic data
`acquisition that maximum allowable noise level thresholds
`
`Ex. PGS 1004
`
`Ex. PGS 1004
`
`

`

`5
`
`6
`
`5 .790,472
`
`5
`
`mum allowable separations between any streamer cable
`and an obstructive hazard. and minimum allowable
`subsurface seismic coverage;
`and the sending step further comprises the steps of:
`determining if the steamer cables are in an at risk
`situation; and
`sending the position correction to the streamer device
`controller when the streamer cables are at risk.
`5. The system of claim 4. wherein the receiving step
`10 further comprises the step of:
`receiving real time signals including recorded seismic
`data; and the sending step further comprises the steps
`of:
`
`15
`
`determining if the streamer cables are in use for recording
`seismic data; and
`
`25
`
`may be established for marine seismic surveys and. when
`these thresholds are exceeded. data acquisition may be
`suspended or the atfected portions of the surveys may have
`to be reacquired. Maximum allowable noise thresholds may
`be chosen in several ways. A single noise threshold. which
`is applied across the entire frequency spectrum of the
`seismic survey. may be chosen as the maximum allowable
`noise threshold. A weighted noise threshold. which varies
`and is applied as a function of the frequency spectum of the
`seismic survey. may be chosen as the maximum allowable
`noise threshold. Also. measurements of background noise
`may be made on hydrophones in the streamer cables 13 and
`used to determine either the single noise or weighted noise
`thresholds.
`
`At step 48. the control on the repositioning of the streamer
`cables 13. due to the level of hydrophone noise. is deter-
`mined by comparing the real time signals of hydrophone
`noise from the seismic data recording system 18 with the
`threshold parameters of maximum allowable hydrophone
`noise. At step 49. it is determined if the real time signals of
`hydrophone noise from the seismic data recording system 18
`exceed any threshold parameter of maximum allowable
`noise. If the real time hydrophone noise exceeds any thresh—
`old parameter of maximum allowable noise. at step 44 the
`streamer control processor 40 is initialized and restarted. If
`the real time hydrophone noise does not exceed any thresh—
`old parameter of maximum allowable hydrophone noise. at
`step 46 the steamer position correction is sent
`to the
`streamer device controller 16 for adjusting the streamer
`positioning devices 14 to reposition the streamer cables 13.
`After the position correction is sent to the streamer device
`controller 16 at step 46. the streamer control processor 40 is
`initialized and restarted at step 44.
`What is claimed is:
`
`1. A system for controlling the position and shape of
`marine seismic streamer cables. comprising the steps of:
`receiving a plurality of real time signals. including hydro-
`phone noise. from a marine seismic data acquisition
`system and a plurality of threshold parameters. includ—
`ing maximum allowable hydrophone noise. from an
`input device;
`comparing the real time signals to the threshold param-
`eters to determine if the streamer cables should be
`repositioned; and
`time
`repositioning the streamer cables when the real
`hydrophone noise signal is within the maximum allow-
`able hydrophone noise threshold and when the remain-
`ing real time signals exceed the threshold parameters.
`2. The system of claim 1. wherein the marine seismic data
`acquisition system further comprises:
`a network solution system;
`a seismic binning system; and
`a seismic data recording system.
`3. The system of claim 2. wherein the repositioning step
`further comprises the steps of:
`calculating a position correction that will keep the
`steamer cables within the threshold parameters; and
`sending the position correction to a streamer device
`contoller for adjusting a plurality of streamer position—
`ing devices.
`4. The system of claim 3. wherein the receiving step
`further comprises the steps of:
`receiving real
`time signals including streamer cable
`positions, streamer cable shapes. streamer cable
`separations, obstructive hazard positions. and subsur-
`face seismic coverage; and
`receiving threshold parameters including minimum
`allowable separations between streamer cables, mini-
`
`sending the position correction to the steamer device
`controller when the streamer cables are not in use for
`recording seismic data.
`6. The system of claim 1. wherein the threshold parameter
`20 of maximum allowable hydrophone noise is a single noise
`threshold which is applied across the entire frequency spec-
`trum of the seismic survey.
`7. The system of claim 6. wherein the single noise
`threshold is determined from measurements of background
`noise made on the streamer cable.
`8. The system of claim 1. wherein the threshold parameter
`of maximum allowable hydrophone noise is a weighted
`noise threshold which varies and is applied as a function of
`the frequency spectrum of the seismic survey.
`9. The system of claim 8. wherein the weighted noise
`30 threshold is determined from measurements of background
`noise made on the steamer cable.
`10. A system for controlling the position and shape of
`marine seismic streamer cables. comprising the steps of:
`receiving a plurality of real time signals.
`including
`streamer cable positions. steamer cable shapes.
`streamer cable separations. obstructive hazard
`positions. subsurface seismic coverage. recorded seis-
`mic data and hydrophone noise. from a marine seismic
`data acquisition system;
`receiving a plurality of threshold parameters. including
`minimum allowable separations between streamer
`cables. minimum allowable separations between any
`streamer cable and an obstructive hazard. minimum
`allowable subsurface seismic coverage and maximum
`allowable hydrophone noise. from an input device;
`calculating a position correction that will keep the
`steamer cables within the threshold parameters;
`determining if the steamer cables are in an at risk
`situation;
`sending the position correction to a streamer device
`controller for adjusting a plurality of streamer position-
`ing devices when the steamer cables are in an at risk
`situation;
`determining if the steamer cables are in use for recording
`seismic data;
`sending the position correction to the steamer device
`controller when the steamer cables are not in use for
`recording seismic data;
`determining if the real time signals of hydrophone noise
`are within the threshold parameters of maximum allow-
`able hydrophone noise; and
`sending the position correction to the steamer device
`controller when the real
`time hydrophone noise is
`within the maximum allowable hydrophone noise
`threshold.
`
`35
`
`45
`
`50
`
`55
`
`65
`
`Ex. PGS 1004
`
`Ex. PGS 1004
`
`