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`Ulllted States Patent [19]
`Workman et al.
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`‘
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`US005790472A
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`[11] Patent Number:
`[45] Date of Patent:
`
`5,790,472
`Aug. 4, 1998
`
`[54] ADAPTIVE CONTROL OF MARINE SEISMIC
`STREAMERS
`
`[75] Inventors: Ricky L. Workman; Ronald Edward
`Chambers. both of Houston. Tex.
`
`['13] Assignw Western Atlas International, Inc-_
`HOuston- TCX-
`
`[21] Appl. No.: ‘771,049
`.
`_
`Dec. 20, 1996
`[22] Filed.
`[5 1]
`Int. Cl.° ..................................................... .. G01V 1/38
`[52] us. c1. ............................................... .. 367/19; 367/16
`[58] Field of Search ................................ .. 367/16. 19. 20.
`367/106. 130. 17; 114/253
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`1/1976 CD16 ............. ..
`3,931,608
`7/1977 waters
`4,033,273
`4,037,730 5/1973 {Ma et a1,
`4,1814% 2/1980 Delignieres
`4,404,664
`9/ 1933 Zachariadis
`4,463,701
`3/1934 Pickett 6‘ al
`472933?’ 3/1988 Kirby e‘ 31'
`4,809,005
`2/1989 Counselman
`4,890,568
`1/1990 Dolengowski ............ .. 114/246
`4,912,682
`3/1990 Norton, Jr. eta],
`367/19
`5,031,159
`7/1991 Rouqueue ............................. .. 367/130
`
`340/7 PC
`144/245
`340/7
`367/19
`367/19
`-~ 114/245
`
`5,353,223 10/1994 Norton et a1. ................... .. 364/421
`5,443,027
`8/1995 Owsley etal.
`.. 114/244
`5,532,975
`7/1996 101161111 .................................... .. 367/16
`OTHER PUBLICATIONS
`
`M. Schoenberger and J. F. Misfud. “Hydrophone Streamer
`Noise”. Geophysics. V01. 39. N0. 6. pp. 781-793.
`Franklyn K. Levin in “Short Note: The Eifect of Binniug on
`Data from a Feathered Streamer”. Geophysics. vol. 49. N0.
`8. pp. 1386-1387.
`Mamdouh R. Gadallah. “Reservoir Seismology”. Pennwell.
`1994. pp. 209437.
`Manin et 111.. “Recent Developments in Source and Streamer
`Positioning” First Break v91- 6- PP- 183-188. Jun- 1981.
`
`Primary Examiner-Ian J. Lobo
`Attorney, Agent, or Firm—James Randall Allen; Charles R.
`Schweppe
`[57]
`
`ABSTRACT
`
`A mC'hOd f°r wm‘??ng the WW0" and shill"a °f marine
`seismic streamer cables. whereby 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. The real time signals are compared to the threshold
`parameters to determine if the streamer cables should be
`repositioned. The streamer cables are repositioned when the
`.
`-
`real “I” “gm” exceed ‘he threshdd Parameters‘
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`10 Claims, 3 Drawing Sheets
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`Ex. PGS 1031
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`US. Patent
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`Aug. 4, 1998
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`Sheet 1 0f 3
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`5,790,472
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`1
`ADAPTIVE CONTROL OF MARINE SEISMIC
`STREAMERS
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`5,790,472
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`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 Kalman ?lter. 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 uni?ed into a single system for
`controlling 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 streamer cables operates as a constraint on the control
`of the position and shape of marine seismic streamer 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 streamer cables.
`
`45
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`SUMMARY OF THE INVENTION
`The present invention is an improved system for control
`ling the position and shape of marine seismic streamer
`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 streamer cables should be repositioned
`Finally. the streamer 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 controlling
`the position and shape of marine seismic streamer cables.
`FIG. 3 shows a ?ow chart illustrating certain steps of a
`streamer control processor
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`FIG. 1 illustrates a generalized schematic of a type of
`marine seismic survey system 01. This system 01 has a
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`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`The present invention generally relates to an improved
`system for controlling the position and shape of marine
`seismic streamers.
`2. Description of the Related Art
`During a typical marine seismic survey a seismic vessel
`traverses programmed tracks towing arrays of seismic
`sources and seismic streamer cables. A seismic streamer
`cable normally contains a plurality of hydrophones which
`convert seismic pressure waves. initiated by the sources and
`re?ected 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 streamer cables to record a highly sampled grid
`of “bins" of subsurface seismic coverage.
`A natural consequence of towing such streamer cable
`con?gurations in a marine environment is that currents.
`wind. and wave action will de?ect the streamer cables from
`their intended paths. Streamer cable dii? 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 streamer 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 e?ect of
`binning on data from a feathered streamer." Geophysics.
`Vol. 49. No. 8. pp. 1386-1387.
`Streamer 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 streamer cables for the
`purpose of maintaining them at a lateral o?’set 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 control the lateral
`positioning of streamer cables by using camber-adjustable
`hydrofoils or angled wings are disclosed in US. 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 control 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
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`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 steamer cable 13. contols 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 steamer cables 13 for adjust
`ing the vertical and lateral positions of the streamer cables
`13. The steamer 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 steamer cables 13
`or by radio transmitter means.
`Referring now to FIG. 2. the interrelationship of the
`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 steamer cable controller 16 for
`controlling the steamer 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 ?lter 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 steamer 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 steamer 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 steamer cables
`13 should be repositioned and for calculating a position
`correction to reposition the steamer 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 steamer cables 13. minimum allowable subsurface
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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 steamer control processor 40 before or
`contemporaneously with the acquisition of a marine seismic
`survey.
`The streamer contol processor 40 is connected to the
`network solution system 10. the seismic binning system 30.
`the streamer positioning contol 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 steamer
`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 steamer device contoller 16.
`When the steamer cables 13 need to be repositioned. the
`position correction is used by the streamer device contoller
`16 to adjust the steamer 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 prevent the repo
`sitioning of the streamer cable 13. Occasionally. towed
`steamer 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 imple
`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 steamer position correction is sent to the streamer
`device contoller 16 for adjusting the streamer positioning
`devices 14 to reposition the steamer 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 steamer device
`contoller 16 for adjusting the steamer positioning devices
`14 to reposition the steamer cables 13.
`‘It is well known in the art of marine seismic data
`acquisition that hydrophone noise limits the resolution of
`marine seismic sln'veys. The preferred embodiment of the
`present invention constains the repositioning of the
`streamer cables 13 by evaluating the hydrophcne noise level
`of the steamer cables 13 when the steamer 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
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`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 spectrum 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 streamer 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:
`l. 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
`repositioning the streamer cables when the real time
`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
`streamer cables within the threshold parameters; and
`sending the position correction to a streamer device
`controller 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
`65
`receiving threshold parameters including minimum
`allowable separations between streamer cables. mini
`
`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 streamer 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:
`determining if the streamer cables are in use for recording
`seismic data; and
`sending the position correction to the streamer 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 streamer 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. streamer 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
`streamer cables within the threshold parameters;
`determining if the streamer 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 streamer cables are in an at risk
`situation;
`determining if the streamer cables are in use for recording
`seismic data;
`sending the position correction to the streamer device
`controller when the streamer 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 streamer device
`controller when the real time hydrophone noise is
`within the maximum allowable hydrophone noise
`threshold.
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