113*‘255
`
`31.13/88
`
`‘4 0 7 2 ‘I! 9 u 3 I5
`
`Umted States Patent [19]
`Kirby et al.
`
`[11] Patent Number:
`[45] Date of Patent:
`
`4,729,333
`Mar. 8, 1988
`
`[54] REMOTELY CONTRO.LLABLE PARAVANE
`[75] Im'emms' 522:1?’ gggfs’eih?itfs'égex"
`'
`Denmark
`[73] Assignee: Exxon Production Research
`Company’ Houston’ Tex‘
`
`’
`
`’
`
`FOREIGN PATENT DOCUMENTS
`2047406B 9/1983 United Ktngdom .
`
`2l22562A l/ 1984 Umted Kingdom .
`
`zggzgt?rzggrélllgsglaigoTmcza
`Attorney. Agent, or Firm-Keith A. Bell
`
`Jul‘ 9’ 1986
`[22] F ‘led:
`[51] Int. (31.4 ............................................ .. B63B 21/66
`[52] US. Cl, . . . . . . , . _ , _ . . .
`. . . ._ 114/244; 114/246;
`114/253
`[58] Field of Search ........................... .. 367/16, 17, 18;
`114/242, 244, 245, 246, 253
`References Cited
`
`[56]
`
`A remotely-controllable, surface-referenced paravane
`for use in towing an Object in a body of water at a con
`trolled lateral offset from the pathway of the towing
`vessel is disclosed. The principal components of the
`paravane are a buoyant hull, a cambered hydrofoil
`shaped keel attached to the bottom of the hull and ex
`tending generally downwardly into the body of water,
`a remotely-controllable steering means, and a tow cable
`which connects the paravane to the towing vessel. Pas
`U-S- PATENT DOCUMENTS
`Sage Of the cambered hydrofoil Shaped keel through the
`2,ss9,312 3/1952 Wilcoxon .......................... .. 114/235
`water generates a lateral force, similar to the lift gener
`2,960,960 1l/1960 Fehlner
`114/235
`ated by an airfoil, which causes the paravane to move
`2,981,220 4/1961 Fehlner
`114/235
`laterally away from the pathway of the towing vessel in
`3,434,451 3/1969 Brainard, II
`114/235
`the direction of the lateral force. The remotely-control
`31605574 9/1971 weese """""" "
`" 114/235 B
`lable steering means is used to compensate for changes
`2’611975 10/1971 Ashbrook "" "
`114/235 B
`.
`.
`.
`.
`.
`.
`,6l3,629 10/1971 Rhyne et al. ..
`114/235 B
`3,921,124 11/1975 Payton ............... .. 340/7 R m the Speed °f the mwmg "@5561 9r vanatms 1“ “"nd’
`4,027,616 6/1977 Guemher et a1_ '
`114/244
`waves, or currents so as to maintain the lateral offset of
`4,033,273 7/1977 Waters . . . . . . . . . 1
`. . . . .. 114/245
`the paravane Within Certain limits- The paravane may be
`4,063,213 12/1977 Itria et al. ..
`340/7 PC
`constructed so as to move laterally to the left (a “port”
`4,087,780 5/1978 ltria etal. ..
`---- ~- 340/ 7 R
`paravane) or to the right (a “starboard” paravane). The
`4,130,073 12/1978 ch01?‘
`114/244
`only difference between a port paravane and a star
`4’193’366 3/1980 salmme“ """""" "
`[14/274
`board paravane is in the cross section of the cambered
`4,323,989 4/1982 Hackabee et al.
`367/17
`h drof -l h ed k l
`ith 0 e b -
`the “mirror im_
`4,350,111 9/1982 Boyce, 11 ........ ..
`.. 114/245
`y ,, O‘ 5 ap
`ee’ W ‘1 emg
`4,463,701 8/1984 Pickett et al. ........... ..
`114/245
`age °f the Other
`4,484,534 ll/ 1984 Thillaye du Boullay
`.. 114/244
`4,574,723 3/1986 Chiles et al. ...................... .. 114/253
`
`10 Claims, 8 Drawing Figures
`
`PGS v. WESTERNGECO (IPR2014-00689)
`WESTERNGECO Exhibit 2057, pg. 1
`
`

`
`US. Patent Mar. 8, 1988
`
`Sheet 1 of4
`
`4,729,333
`
`PGS v. WESTERNGECO (IPR2014-00689)
`WESTERNGECO Exhibit 2057, pg. 2
`
`

`
`U.S. Patent Mar. 8, 1988
`
`Sheet 2 of4
`
`4,729,333
`
`STA RBOAPD
`
`PGS v. WESTERNGECO (IPR2014-00689)
`WESTERNGECO Exhibit 2057, pg. 3
`
`

`
`US. Patent Mar. 8, 1988
`
`Sheet 3 of4
`
`4,729,333
`
`FIGS
`
`STARBOARD
`
`15
`
`' A
`47
`1
`
`TRANSM/TTER/
`
`23
`
`=
`
`L 20
`
`I8
`
`FIG. 7
`
`10 __
`
`RECE/VER/____
`L'ONTROLLER
`
`56
`
`,54
`
`$1
`
`52
`
`P
`
`1'
`
`J.
`
`PGS v. WESTERNGECO (IPR2014-00689)
`WESTERNGECO Exhibit 2057, pg. 4
`
`

`
`US. Patent Mar. 8, 1988
`
`Sheet 4 of4
`
`4,729,333
`
`FIG. 6
`
`2'
`2’ -
`'
`I, ‘11% 74
`
`I
`
`FIG. 8
`
`STARBOART
`
`PORT
`
`70a 93
`
`54
`
`54
`
`PGS v. WESTERNGECO (IPR2014-00689)
`WESTERNGECO Exhibit 2057, pg. 5
`
`

`
`1
`
`REMOTELY-CONTROLLABLE PARAVANE
`
`5
`
`15
`
`_ FIELD OF THE INVENTION
`The invention relates to the ?eld of marine towing.
`More particularly, but not by way of limitation, the
`invention pertains to a remotely-controllable, surface
`referenced paravane for use in towing an object at a
`controlled lateral offset from the pathway of the towing
`vessel. In the ?eld of marine geophysical prospecting,
`the invention may be used to tow seismic sources and
`/or seismic receiver cables along discrete pathways
`parallel to but laterally spaced from the pathway of the
`towing vessel.
`BACKGROUND OF THE INVENTION
`In recent years the search for oil and gas has moved
`offshore. In order to locate potential offshore oil and
`gas reservoirs, it has been necessary to develop new
`20
`devices and techniques for conducting marine geophys
`ical prospecting operations. Due to the hostile environ
`ment in which they are conducted, such operations are
`typically quite difficult and costly to perform.
`The primary method for conducting marine geophys
`25
`ical prospecting operations involves the use of towable
`marine seismic sources and seismic receiver cables. The
`basic principles of this prospecting method are well
`known to those skilled in the art. The seismic source(s)
`introduce seismic signals into the body of water. These
`signals propagate down through the water, across the
`30
`water-?oor interface, and into the subterranean geologi- '
`cal formations, and are, to some extent, re?ected by the
`interfaces between adjacent formations. The re?ected
`signals travel upwardly through the geological forma
`tions and the body of water to a seismic receiver cable
`located near the surface of the body of water. The seis
`mic receiver cable typically contains a number of hy
`drophones spaced along its length which record the
`re?ected signals. Analysis of the signals recorded by the
`hydrophones can provide valuable information con
`cerning the structure of the subterranean geological
`formations and possible oil and gas accumulation
`therein.
`Early marine geophysical prospecting operations
`were generally conducted “in-line”. In other words, the
`seismic source(s) and the seismic receiver cable were
`towed substantially directly behind the seismic vessel,
`and the resulting geophysical data was valid only for a
`relatively narrow band along the pathway of the vessel.
`Thus, the seismic vessel was required to make a number
`of passes along relatively closely spaced pathways in
`order to collect the necessary geophysical data for a
`given survey area. This requirement contributed di
`rectly to the cost and difficulty of conducting marine
`geophysical prospecting operations.
`In order to reduce the number of passes of the seismic
`vessel necessary for any given survey area, and hence
`the cost of conducting the survey, the offshore geo
`physical industry has developed various devices and
`techniques for increasing the width of the “swath” of 60
`geophysical data collected during each pass of the seis
`mic vessel. Generally such devices and techniques in
`volve the use of multiple seismic sources and/ or seismic
`receiver cables, each of which is towed by the seismic
`vessel along a discrete pathway which is parallel to but
`laterally spaced from the pathways of the other sources
`and receiver cables. Typically, the lateral spacing of the
`sources and receiver cables is symmetric about the path
`
`4,729,333
`2
`way of the seismic vessel. See, for example, the wide
`seismic source disclosed in U.S. Pat. No. 4,323,989 is
`sued Apr. 6, 1982 to Huckabee et al.
`In addition to reducing the number of passes neces
`sary for a particular survey area, the use of multiple
`seismic sources and/or seismic receiver cables may
`improve the quality of the resulting geophysical data.
`For example, the use of an array of seismic sources can
`increase the signal to noise ratio of the signal recorded
`by the hydrophones, thereby resulting in higher quality
`geophysical data. Further, the use of a plurality of seis
`mic sources which are activated or ?red simultaneously
`can increase the amount of energy in the seismic pulse,
`thereby permitting data to be gathered from very deep
`subterranean formations.
`In order for a single vessel to tow multiple seismic
`sources and/or seismic receiver cables along laterally
`spaced parallel pathways, means must be provided for
`causing the objects being towed to move laterally away
`from the pathway of the towing vessel. One such means
`is disclosed in U.S. Pat. No. 4,130,078 issued Dec. 19,
`1978 to Cholet. Cholet discloses a device comprising at
`least two parallel de?ectors secured to a ?oating mem
`ber. Each of the de?ectors consists of a series of parallel
`paddles which are oriented obliquely to the trajectory
`of the device so that hydrodynamic pressure on the
`paddles forces the device in a lateral direction. The
`paddles may be either curved or ?at sheets. The amount
`of lateral offset produced by this device is dependent on
`the speed that it is towed through the water, and the
`device cannot be remotely controlled.
`Another device for laterally shifting the trajectory of
`a towed object is disclosed in U.S. Pat. No. 3,613,629
`issued Oct. 19, 1971 to Rhyne et al. The Rhyne et al.
`device consists of a streamlined ?oat with a diverter
`arrangement rigidly suspended below the ?oat. Hydro
`dynamic pressure on the diverter causes the device to
`move laterally away from the pathway of the towing
`vessel. As with the Cholet device, the amount of lateral
`offset produced by the Rhyne et al. device is dependent
`on' its speed through the water, and it cannot be re
`motely controlled.
`Still another device for laterally shifting the trajec
`tory of a towed object is disclosed in the above refer
`enced patent to Huckabee et al. That device comprises
`an elongated ?oat equipped with a remotely-adjustable
`rudder. The only lateral force generated by the Hucka
`bee et al. device is the force resulting from hydrody
`namic pressure on the rudder. Accordingly, the device
`is not capable of achieving large lateral offsets. Outrig
`gers on the vessel are used to increase the maximum
`lateral offset produced by the device.
`Submerged paravanes have been used heretofore in
`marine operations for a variety of purposes. For exam
`ple, in commercial fishing operations submerged para
`vanes have been used to hold open a fishing net being
`towed by a vessel. Submerged paravanes have also been
`used in minesweeping operations to laterally shift the
`trajectory of the minesweeping equipment away from
`the pathway of the towing vessel. An example of one
`such submerged paravane is disclosed in U.S. Pat. No.
`2,960,960 issued Nov. 22, 1960 to Fehlner. The Fehlner
`paravane consists of a cambered hydrofoil shaped para
`vane wing containing a depth control mechanism. As
`the paravane wing is towed through the water, the
`cambered hydrofoil shape generates a substantially lat
`eral hydrodynamic force similar to the “lift” generated
`
`40
`
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`50
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`55
`
`65
`
`PGS v. WESTERNGECO (IPR2014-00689)
`WESTERNGECO Exhibit 2057, pg. 6
`
`

`
`4,729,333
`4
`3
`The amount of lateral force generated by the cam
`by an airfoil. This lateral hydrodynamic force causes
`bered hydrofoil shaped keel may be increased by attach~
`the paravane wing to move laterally away from the
`pathway of the towing vessel. As with the surface
`ing the keel to the buoyant hull so that the chord line of
`the cambered hydrofoil shaped cross section forms a
`referenced devices described above, the amount of lat
`positive angle of attack with the longitudinal centerline
`eral movement is dependent on the speed of the towing
`of the hull. This will cause a hydrodynamic pressure
`vessel, and the paravane wing cannot be remotely con
`trolled. Further, unless the paravane wing is maintained
`force on the pressure side of the keel as it passes through
`in a substantially vertical orientation, the lateral hydro
`the water which will be in substantially the same direc
`tion as, and will be supplementary to, the lateral hydro
`dynamic force will have a vertical component which
`dynamic force generated by the cambered hydrofoil
`will cause the depth of the paravane wing to ?uctuate.
`shaped keel. Additionally, as more fully described be
`As described above, the use of multiple seismic
`low, the effective angle of attack may be varied by
`sources and/or multiple seismic receiver cables towed
`along discrete pathways parallel to but laterally spaced
`changing the point(s) at which the tow cable is attached
`from the pathway of the seismic vessel may be highly
`to the keel.
`The remotely-controllable steering means typically
`bene?cial in conducting marine geophysical prospect
`ing operations, both from the standpoint of reducing the
`would comprise a conventional rudder, the angular
`position of which may be controlled and adjusted from
`cost of conducting the survey and from the standpoint
`of improving the quality of the resulting geophysical
`a remote location such as the towing vessel. Alterna
`tively, other steering means, such as the powered pro
`data. However, the accuracy and reliability of the re
`sulting geophysical data is dependent on precisely main
`peller nozzle described below, may be used if desired.
`20
`taining the lateral spacing of the various components of
`Preferably, the steering means would be controlled and
`the system throughout the time during which the seis
`adjusted by a rudder control means located on board
`mic vessel is traversing the survey area. Thus, the bene
`the paravane. A radio wave link having a transmitter
`?ts resulting from the use of multiple sources and/or
`located on board the towing vessel and a receiver/con
`multiple receiver cables may be lost if the towing sys~
`troller tuned to the same frequency channel as the trans
`25
`tem is not capable of being remotely controlled and
`mitter located on board the paravane typically would
`adjusted to compensate for changes in the speed of the
`be used to remotely activate and control the rudder
`control means. Any suitable rudder control means may
`towing vessel or variations in wind, waves, or currents.
`Accordingly, the need exists for a remotely-controlla
`be used.
`ble device capable of maintaining the lateral offset of a
`The paravane of the present invention may include
`30
`additional peripheral equipment such as rudder position
`towed object within certain limits over a broad range of
`operating conditions.
`sensors, range and azimuth measuring instrumentation,
`and additional radio wave links for communicating
`SUMMARY OF THE INVENTION
`between the seismic vessel and the paravane. Data from
`The present invention is a remotely-controllable,
`these sensors and instruments may be continuously fed
`surface-referenced paravane for use in towing an object
`into a computer located on board the seismic vessel
`along a pathway parallel to but laterally spaced from
`which would continuously monitor the precise location
`the pathway of the towing vessel. As used herein, “sur
`of the paravane and initiate any necessary corrective
`actions to precisely maintain the lateral offset of the
`face-referenced” means that the paravane is buoyant
`and that it remains substantially on the surface of the
`paravane.
`body of water during operation. The inventive para
`vane satis?es the need described above for a device
`capable of maintaining the lateral offset of a towed
`object within certain limits over a broad range of oper
`ating conditions. Further, due to its unique design, the
`paravane is capable of attaining and maintaining larger
`lateral offsets than have heretofore been possible using
`conventional surface-referenced devices.
`The principal components of the inventive paravane
`are a buoyant hull, a cambered hydrofoil shaped keel
`which is attached to the bottom of the hull and extends
`generally downwardly into the body of water, a
`remotely-controllable steering means, and a tow cable
`which connects the paravane to the towing vessel. Pas
`sage of the cambered hydrofoil shaped keel through the
`water generates a lateral hydrodynamic force similar to
`the lift generated by an airfoil. This lateral hydrody
`namic force causes the paravane to move laterally away
`from the pathway of the towing vessel in the direction
`of the lateral force.
`For marine geophysical prospecting operations, both
`port and starboard (left and right) paravanes would
`typically be used to provide a symmetrical pattern of
`sources and receiver cables. As more fully described
`below, the only difference between a port paravane and
`a starboard paravane is in the cross sectional shape of
`the keel, with one being the “mirror image” of the
`other.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`The actual operation and advantages of the present
`invention will be better understood by referring to the
`following detailed description and the attached draw
`ings in which:
`FIG. 1 is a perspective view illustrating the principal
`components of a ?rst embodiment of the paravane of
`the present invention;
`FIG. 2 is a perspective view illustrating the principal
`components of a second embodiment of the paravane;
`FIG. 3 is a side elevational view of the embodiment
`of the paravane illustrated in FIG. 1;
`FIG. 4 is a bottom plan view, in partial section, of the
`paravane taken along line 4—4 of FIG. 3 and showing
`the cambered hydrofoil shaped cross section of a “port”
`paravane keel;
`FIG. Sis a bottom plan view, in partial section, show
`ing the cambered hydrofoil shaped cross section of a
`“starboard” paravane keel;
`FIG. 6 is a bottom plan view taken along line 6—6 of
`FIG. 3 showing one embodiment of the tow point ad
`justment block;
`FIG. 7 is a partial schematic plan view showing the
`paravane of the present invention being used to tow
`multiple seismic sources; and
`FIG. 8 is a schematic plan view showing the para
`vane being used to tow multiple seismic receiver cables.
`
`65
`
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`40
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`
`PGS v. WESTERNGECO (IPR2014-00689)
`WESTERNGECO Exhibit 2057, pg. 7
`
`

`
`4,729,333
`5
`6
`While the invention will be described in connection
`foam ?lled as a protection against leaking. As with hull
`with the preferred embodiments, it will be understood
`12, keel 14 would typically be made of a light-weight
`that the invention is not limited thereto. On the con
`material such as ?berglass or aluminum.
`As illustrated in FIGS. 1, 2, and 3, keel 14 is shown as
`trary, it is intended to cover all alternatives, modi?ca- »
`tions, and equivalents which may be included within the
`having a backward slant from top to bottom. This back
`spirit and scope of the invention.
`ward slant is known as the “rake aft” of the keel 14.
`Although not necessary for the invention, a certain
`amount of rake aft tends to improve the hydrodynamic
`handling characteristics of the paravane 10. As illus
`trated, the rake aft of keel 14 is approximately 10° from
`the vertical; however, as much as 45° or more of rake
`aft may be used if desired.
`Preferably, keel 14 should be con?gured and
`mounted so as to substantially maximize the lateral hy
`drodynamic force F generated by the passage of the
`keel through the surrounding water. As illustrated in
`FIG. 4, the cambered hydrofoil shaped cross section of
`keel 14 has an almost flat pressure side 14a and a highly
`cambered reduced-pressure side 14b; however, other
`cambered hydrofoil shapes may be used if desired. Typ
`ically, keel 14 would be attached to flange plate 24 so
`that the chord line 28 of its cross section forms a posi
`tive angle of attack “a” with the longitudinal centerline
`30 of buoyant hull 12. (As used herein and in the claims,
`“chord line” means a straight line connecting the lead
`ing edge 14c and the trailing edge 14d of the hydrofoil
`cross section and a “positive angel of attack” means that
`the leading edge 14c of the hydrofoil has been rotated
`away from the longitudinal centerline 30 of buoyant
`hull 12 in the direction of lateral force F, as illustrated
`in FIG. 4). The angle of attack a may be as small as one
`or two degrees or as large as ten to ?fteen degrees;
`however, beyond a certain angle (the “critical” angle)
`the hydrodynamic ?ow characteristics of the keel are
`lost, similarly to the stalling angle of an airfoil.
`Towing cable 18 connects the paravane 10 to the
`towing vessel 20 (see FIGS. 7 and 8). Typically, cable
`18 would be connected to the keel 14 of paravane 10;
`however, alternatively it may be attached to hull 12 if
`desired. As illustrated in FIGS. 1 and 2, cable 18 is split
`into two separate strands 18a and 18b near keel 14.
`Strand 18a is attached to tow point adjustment block
`190 located near the top of keel 14 while strand 18b is
`attached to tow point adjustment block 19b located near
`the bottom of keel 14. Since the resultant lateral force F
`generated by keel 14 is directed away from cable 18 and
`is located between the two tow point adjustment blocks,
`this double attachment helps to maintain the paravane
`10 in an upright position during towing.
`As most clearly shown in FIG. 6, each of the tow
`point adjustment blocks 19a and 19b has a series of holes
`21 therethrough. Cable strands 18a and 18b can be at
`tached, respectively, to tow point adjustment blocks
`19a and 19b at any of these holes. It has been found that
`the amount of lateral force generated by keel 14 in
`creases as the connection point moves toward the rear
`of keel 14. This increase in lateral force results from the
`fact that as the connection point moves backward, the
`entire paravane 10 tends to skew or “crab” sideways
`slightly thereby increasing the effective angle of attack.
`As illustrated in FIGS. 1 through 4, paravane 10 is a
`left or “port” paravane. In other words, as it is towed
`through the water, paravane 10 will move laterally to
`the left away from the pathway of the towing vessel.
`For geophysical prospecting operations, a right or
`“starboar ” paravane will typically also be necessary in
`order to provide a symmetric array of sources and/0r
`receiver cables. As will be obvious to those skilled in
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`The two primary embodiments of the paravane are
`illustrated, respectively, in FIGS. 1 and 2. FIG. 1 illus
`trates the “yacht” embodiment of the paravane; FIG. 2
`illustrates the “canard” embodiment. As more fully
`described below, the principal difference between the
`yacht and canard embodiments of the paravane is in the
`placement of the steering means with respect to the
`keel. In the yacht embodiment (FIG. 1) the steering
`means (rudder 16) is located behind the keel. In the
`canard embodiment (FIG. 2) the steering means (pro
`peller nozzle 60) is located in front of the keel.
`In the embodiment illustrated in FIGS. 1, 3, and 4, the
`primary components of the paravane, generally indi
`cated at 10, are buoyant hull 12, keel 14, rudder 16, and
`tow cable 18 (FIG. 1 only) which connects the para
`vane 10 to the towing vessel 20 (see FIGS. 7 and 8).
`Additionally, as more fully described below, paravane
`10 also includes a rudder control means for controlling
`and adjusting the angular position of rudder 16 about a
`substantially vertical axis.
`Buoyant hull 12 provides all of the buoyancy neces
`sary for paravane 10 to ?oat on the surface of the body
`of water. Preferably, buoyant hull 12 is of hollow con
`struction so that the rudder control means and other
`peripheral equipment can be housed therein. Part or all
`of the hull 12 may be ?lled with a closed cell foam as a
`protection against leaking. Hull 12 would typically be
`made of a suitable light-weight material such as ?ber
`glass or aluminum. A removable, water-tight hatch 22
`may be used to provide access to the interior of bull 12,
`as is well known in the art. Buoyant hull 12 should be
`con?gured so as to substantially minimize the towing
`resistance of paravane 10 while maintaining adequate
`hydrodynamic stability. As illustrated herein, hull 12 is
`con?gured similarly to a conventional surfboard; how
`ever other shapes may be used if desired.
`The primary purpose of keel 14 is to generate the
`lateral force necessary to move paravane 10 laterally
`away from the pathway of the towing vessel. As more
`clearly shown in FIGS. 3 and 4, keel 14 is a cambered
`hydrofoil which is attached to the bottom of buoyant
`hull 12 and extends generally downwardly into the
`body of water. As the paravane 10 is towed through the
`surrounding water, keel 14 generates a lateral hydrody
`namic force F in the same manner as an airfoil generates
`lift. It will be understood that the lateral hydrodynamic
`force generated by keel 14 is actually a small force per
`unit area distributed over the entire surface area of keel
`14, and that force F, as illustrated in the drawings, is the
`resultant obtained by adding together all of these
`smaller forces. For a keel having a uniform cross sec
`tional area from top to bottom, force F will be located
`at the midpoint of the keel’s vertical span.
`Keel 14 is rigidly attached to ?ange plate 24 which is
`removably attached to buoyant hull 12 by bolts 26 or
`the like. Ballast 32 (see FIG. 3), which may be sand,
`concrete, steel, lead, or the like, may be placed in the
`bottom of keel 14 to increase the hydrodynamic stabil
`ity of paravane 10. The remainder of keel 14 may be
`
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`PGS v. WESTERNGECO (IPR2014-00689)
`WESTERNGECO Exhibit 2057, pg. 8
`
`

`
`4,729,333
`
`10
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`30
`
`35
`
`7
`the art, the cross section of the keel of a starboard para
`vane will typically be the “mirror image” of the cross
`section of a port paravane keel. FIG. 5 illustrates a
`bottom plan view of the keel 15 of a starboard paravane.
`The pressure side 15a, reduced-pressure side 15b, and
`angle of attack a. are the mirror images of those shown
`in FIG. 4 for a port paravane keel. Accordingly, the
`lateral force F generated by keel 15 will also be in the
`opposite direction. Preferably, ?ange plate 24 and the
`mounting holes 34 therein are identical for both port
`and starboard keels so that either type of keel may be
`attached to a given hull 12.
`Referring again to FIGS. 1, 3 and 4, the lateral offset
`of paravane 10 as it is being towed through the water
`may be remotely controlled and adjusted through rud
`der 16. Typically, rudder 16 would be a substantially
`vertical plate attached to a shaft 36 which extends up
`wardly into the interior of buoyant hull 12 through a
`suitable water-tight bearing or bushing (not shown).
`As noted above, a rudder control means is used for
`controlling and adjusting the angular position of rudder
`16 about a substantially vertical axis (i.e., shaft 36). One
`suitable rudder control means, generally indicated at 37,
`is illustrated in FIG. 4. A crank arm 38 is ?xedly at
`tached at one of its ends to shaft 36. The other end of 25
`crank arm 38 is pivotally attached to electric push-pull
`actuator 40 by clevis 42 and rod 44. Electrical power to
`operate actuator 40 is provided by battery 46 through
`electrical wires 48. By extending or retracting rod 44,
`actuator 40 is capable of adjusting the angular position
`of rudder 16 up to about :45“ from its neutral position
`(as illustrated). Other suitable rudder control means will
`be obvious to those skilled in the art.
`The rudder control means must be capable of being
`activated and controlled from a remote location such as
`the towing vessel. This might be accomplished through
`an electrical umbilical stretching from the vessel to the
`.paravane. Preferably, however, the rudder control
`means would be activated by a radio wave link. A radio
`wave transmitter 47 (see FIG. 7) is located on board the
`vessel 20 and a receiver/controller 49 (tuned to the
`same frequency channel as the transmitter) is located in
`the interior of hull 12 of paravane 10. Typically, an
`antenna 50 (see FIG. 3) for receiver/controller 49
`would be located in the mast 52 mounted on the rear of 45
`hull 12. Mast 52 may also contain other peripheral
`equipment such as transmitter or receiver antennas for
`rudder position sensors or range and azimuth measuring
`instrumentation. As is well known in the art, transmitter
`47 and receiver/controller 49 may be used to remotely
`activate and control the movement of actuator 40 and
`thereby the angular position of rudder 16.
`Operation of paravane 10 is illustrated in FIG. 7. The
`towing vessel 20 is proceeding in the direction of the
`arrow and is towing one in-line seismic receiver cable
`54 together with port paravane 10. Two seismic sources
`56 are attached to the cable 18 between vessel 20 and
`port paravane 10. Cable 18 may be attached directly to
`vessel 20 or, optionally, to an outrigger 23 so as to
`increase the maximum lateral offset of paravane 10.
`60
`Typically, a starboard paravane (not shown) and two
`additional seismic sources 56 would be used to provide
`symmetry about the pathway of vessel 20. It will be
`understood that additional sources and receiver cables
`could also be used if desired.
`It is desired to maintain the lateral offsets S1 and 5;
`between the pathway of the vessel 20 and the two seis
`mic sources 56 as precisely as possible during the time
`
`55
`
`50
`
`65
`
`8
`.the seismic vessel is traversing the survey area. In order
`to do so, remotely controllable paravane 10 must be
`maintained as nearly as possible at a lateral offset of P.
`This is accomplished by continually monitoring the
`position of paravane 10 with respect to vessel 20 and
`remotely adjusting the angular position of rudder 16 so
`as to compensate for any changes resulting from varia
`tions in wind, waves, currents, or the speed of vessel 20.
`The actual course of paravane 10 will likely vary
`within certain limits as indicated by the dashed line 58 in
`FIG. 7. The amount of variation, AP, will be dependent
`on the sensitivity of the system used to detect and com
`pensate for position changes of paravane 10. For exam
`ple, if detection of position changes is done visually, AP
`may be substantial. On the other hand, AP can be sub
`stantially minimized through the use of electronic range
`and azimuth measuring instrumentation together with
`an automatic computer (not shown) located on board
`vessel 20. Output from the range and azimuth measur
`ing instrumentation would be continuously monitored
`by the computer which would issue appropriate instruc
`tions through the radio wave link to correct for any
`changes in the position of paravane 10. A rudder posi
`tion sensor (not shown) on board paravane 10 might
`also be used to continuously monitor the position of
`rudder 16 and to indicate when the rudder has reached
`its maximum movement.
`FIG. 8 illustrates schematically the use of the present
`invention to tow multiple seismic receiver cables. Ves
`sel 20 is proceeding in the direction of the arrow and is
`towing one or more seismic sources 56 (two shown)
`substantially directly behind the vessel. Port paravane
`10a and starboard paravane 10b are each connected to
`vessel 20 by a cable 18 in the manner previously de
`scribed. One or more seismic receiver cables 54 are
`attached to each of the cables 18. Each of the paravanes
`is remotely controlled by a separate, discrete radio
`channel so as to maintain the lateral spacing of the seis
`mic receiver cables 54 as precisely as possible during the
`time vessel 20 is traversing the survey area.
`As noted above, the canard embodiment of the para
`vane is illustrated in FIG. 2. In the canard embodiment,
`the keel 14 is located behind the steering means which,
`as illustrated, is powered propeller nozzle 60.
`Propeller nozzle 60 is attached to a substantially ver
`tical shaft 62 which extends upwardly into hull 12
`through a suitable water-tight bearing or bushing (not
`shown). The angular position of propeller nozzle 60 is
`remotely-controllable in the same manner as described
`above for rudder 16. Additionally, propeller nozzle 60
`contains a propeller 64 which typically would be pow
`ered by an electric motor (not shown) located in the
`forward housing 66 of propeller nozzle 60. One or more
`batteries located in the interior of hull 12 (not shown) or
`an electrical umbilical (not shown) would be used to
`power the motor. Alternatively, a hydraulic drive sys
`tem could be used to power the propeller 64. Accord
`ingly, in addition to providing an acceptable steering
`means, propeller nozzle 60 also may be used to indepen
`dently drive paravane 10. This may increase the maxi
`mum lateral offset which can be achieved by the para
`vane.
`The paravane of the present invention may be of any
`suitable size. However, for marine geophysical pros
`pecting operations, the length of buoyant hull 12 would