U.S. patent application number 11/055169 was filed with the patent office on 2006-08-10 for apparatus and methods for controlling position of marine seismic sources.
Invention is credited to Rune Toennessen.
Application Number | 20060176774 11/055169 |
Document ID | / |
Family ID | 36119727 |
Filed Date | 2006-08-10 |
United States Patent
Application |
20060176774 |
Kind Code |
A1 |
Toennessen; Rune |
August 10, 2006 |
Apparatus and methods for controlling position of marine seismic
sources
Abstract
Apparatus and methods are described for remotely controlling
position of marine seismic equipment. One apparatus comprises a
source connected to a tow member; and an adjustment mechanism
connected to the source and the tow member, the adjustment
mechanism adapted to actively manipulate an angle of attack of the
source. It is emphasized that this abstract is provided to comply
with the rules requiring an abstract, which will allow a searcher
or other reader to quickly ascertain the subject matter of the
technical disclosure. It is submitted with the understanding that
it will not be used to interpret or limit the scope or meaning of
the claims. 37 CFR 1.72(b).
Inventors: |
Toennessen; Rune; (Oslo,
NO) |
Correspondence
Address: |
WESTERNGECO L.L.C.
10001 RICHMOND AVENUE
(P.O. BOX 2469, HOUSTON, TX 77252-2469, U.S.A.)
HOUSTON
TX
77042
US
|
Family ID: |
36119727 |
Appl. No.: |
11/055169 |
Filed: |
February 10, 2005 |
Current U.S.
Class: |
367/16 |
Current CPC
Class: |
G01V 1/3861
20130101 |
Class at
Publication: |
367/016 |
International
Class: |
G01V 1/38 20060101
G01V001/38 |
Claims
1. An apparatus comprising: a seismic source array connected to a
source tow member; and an adjustment mechanism connected to the
source array and the source tow member, the adjustment mechanism
adapted to actively manipulate an angle of attack of the source
array.
2. The apparatus of claim 1 wherein the adjustment mechanism is
connected to the source array at one or more tow points located on
the source array.
3. (canceled)
4. The apparatus of claim 1, wherein the source array comprises a
float and one or more source members attached to the float.
5. The apparatus of claim 4, wherein the adjustment mechanism
comprises a deflecting member able to create lift by changing its
angle of attack, wherein the angle of attack of the deflecting
member may be the same or different than the angle of attack of the
source array.
6. The apparatus of claim 5, wherein the adjustment mechanism
further comprises a rigid moment-transfer member having first and
second portions, the first portion connected to the source tow
member, the second portion connected to a tow point on the
deflecting member through a swivel joint.
7. The apparatus of claim 6, wherein the adjustment mechanism
further comprises an actuator mounted on the deflecting member near
the tow point and adapted to actuate the rigid moment-transfer
member.
8. The apparatus of claim 1, further comprising a local controller
mounted on the source array, the local controller adapted to
receive a signal from a remote controller comprising a desired
angle of attack, inform the adjustment mechanism of the desired
angle of attack, and signal an actuator to move the adjustment
mechanism accordingly.
9. The apparatus of claim 8, wherein the adjustment mechanism
further comprises a sensor able to measure the angle of attack.
10. The apparatus of claim 6 wherein the deflecting member is
selected from a low aspect ratio member and a high aspect ratio
member.
11. (canceled)
12. The apparatus of claim 10 wherein the deflecting member is
positioned at a position selected from (1) suspended between the
float and one or more of the source members and (2) rigidly
attached to the float.
13-16. (canceled)
17. The apparatus of claim 1 wherein the adjustment mechanism
includes a towing harness.
18. The apparatus of claim 6 wherein the rigid moment-transfer
member is selected from solid members, telescope members, I-beam
members and hollow members.
19. The apparatus of claim 18 wherein the solid member is selected
from cylindrical members and parallelepiped members.
20-27. (canceled)
28. The apparatus of claim 1 further comprising: the adjustment
mechanism comprising a deflecting member, a bridle system, and an
actuator mounted on the deflecting member and operatively connected
with the bridle system.
29. The apparatus of claim 28 wherein the actuator is positioned on
the deflecting member approximately at a mid-section of the
deflecting member.
30. The apparatus of claim 28 further comprising a local controller
mounted on the apparatus, the local controller adapted to receive a
signal from a remote controller and send a signal to a motor and
the actuator.
31. The apparatus of claim 28 wherein the bridle system is remotely
adjustable.
32. The apparatus of claim 28 wherein the bridle system comprises a
front bridle leg attached to a front end of the deflecting member,
and an aft bridle leg operatively coupled to the actuator.
33. The apparatus of claim 28 wherein the bridle system comprises a
frame that is connected to a front end of the deflecting member via
a swivel joint, the deflecting member adapted to pivot about the
swivel joint, the frame also attached to an aft bridle leg
operatively coupled to the actuator.
34-36. (canceled)
37. The apparatus of claim 28 wherein the actuator is selected from
linear and rotatable actuators.
38-39. (canceled)
40. The apparatus of claim 1 further comprising: the adjustment
mechanism comprising a deflecting member, a frame, and an actuator
mounted on the deflecting member and operatively connected with the
frame.
41. The apparatus of claim 40 wherein the actuator comprises two
linear actuators.
42. The apparatus of claim 41 wherein the two linear actuators are
remotely controllable.
43. The apparatus of claim 42 wherein the adjustment mechanism is
devoid of a bridle system.
44. A system comprising: a tow vessel; and the source tow member of
the apparatus of claim 1 connected to the tow vessel.
45. The system of claim 44 wherein the adjustment mechanism has or
has not a direct mechanical connection with the tow vessel.
46. The system of claim 45 wherein the direct mechanical connection
comprises a passive, strength-taking tow member and an
umbilical.
47. The system of claim 44 wherein the adjustment mechanism
comprises a deflector, the deflector comprising a principal
wing-shaped body shaped to produce in use a lateral force which
urges the source laterally with respect to the direction of
movement of the tow vessel, a boom extending rearward from the
principal wing-shaped body, and an auxiliary wing-shaped body,
smaller than the principal wing-shaped body, secured to an end of
the boom remote from the principal wing-shaped body and shaped so
as to produce in use a lateral force in a general direction
opposite to that produced by the principal wing-shaped body, and
comprising a remotely operable means for adjusting an angle between
the boom and the auxiliary wing-shaped body to vary the lateral
force produced by the principal wing-shaped body.
48. The system of claim 44 wherein the adjustment mechanism
comprises a deflector, the deflector comprising a principal
wing-shaped body shaped to produce in use a lateral force which
urges the source laterally with respect to the direction of
movement of the tow vessel, a boom extending rearward from the
principal wing-shaped body, and an auxiliary wing-shaped body,
smaller than the principal wing-shaped body, secured to an end of
the boom remote from the principal wing-shaped body and shaped so
as to produce in use a lateral force in a general direction
opposite to that produced by the principal wing-shaped body, and
comprising a remotely operable means for adjusting an angle between
the boom and the principal wing-shaped body to vary the lateral
force produced by the principal wing-shaped body.
49. The system of claim 44 wherein the adjustment mechanism
comprises a deflector, the deflector comprising a plurality of
passive hydrofoils suspended between a pair of plates, and at least
one active hydrofoil mounted aft of the passive hydrofoils.
50-63. (canceled)
64. A seismic deflector comprising a plurality of passive
hydrofoils suspended between a pair of plates, and at least one
active hydrofoil mounted aft of the passive hydrofoils.
65. The deflector of claim 64 wherein the active hydrofoil is
adapted to be moved and change an angle of attack of the
deflector.
66. The deflector of claim 65 wherein the active hydrofoil is
adapted to be moved using an actuator.
67. The deflector of claim 66 wherein the actuator is adapted to be
actuated using a local controller and through remote communication
between the local controller and a tow vessel.
68. A method comprising actively controlling an angle of attack of
a marine seismic source using the apparatus of claim 1.
69-98. (canceled)
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of Invention
[0002] The present invention relates to the field of marine seismic
instruments and methods of controlling same. More specifically, the
invention relates to apparatus and methods for remotely controlling
position marine seismic instrumentation, as well as related
systems, methods, and devices.
[0003] 2. Related Art
[0004] Marine seismic exploration investigates and maps the
structure and character of subsurface geological formations
underlying a body of water. For large survey areas, a single vessel
may tow one or more seismic sources and one or more seismic
streamer cables through the water. Alternatively, a tow vessel may
either be a "pure" source vessel (meaning it only tows seismic
sources) or a "pure" streamer (receiver) vessel, in which case two
or more vessels may be used. In any case the seismic sources may
comprise compressed air guns or other means for generating acoustic
pulses in the water. The energy from these pulses propagates
downwardly into the geological formations and is reflected upwardly
from the interfaces between subsurface geological formations. The
reflected energy is sensed with hydrophones attached to the seismic
streamers, and data representing such energy is recorded and
processed to provide information about the underlying geological
features.
[0005] Three-dimensional (3-D) seismic surveys of a grid provide
more information regarding the subsurface formations than
two-dimensional seismic surveys. 3-D surveys may be conducted with
up to twelve or more streamers that form an array covering a large
area behind the vessel. The streamers typically vary in length
between three and twelve kilometers. Tail buoys attached at the
streamer distal ends carry radar reflectors, navigation equipment,
and acoustic transponders. Hydrophones are positioned along each
streamer. The in-line interval between each receiver, or receiver
group, ranges between about 3 and 25 meters, with 12.5 meters
comprising typical interval spacing.
[0006] Since the grid is often much wider than the array, the tow
vessel must turn around and tow the array in laps across the grid,
being careful not to overlap or leave large gaps between the laps
across the grid.
[0007] A multiple streamer array requires deflectors near the
vessel to pull the streamers outwardly from the direct path behind
the seismic tow vessel and to maintain the transverse or crossline
spacing between individual streamers. The same is true for multiple
sources being towed behind a tow vessel when no streamers are
present. Deflectors rely on hydrodynamic lift created by forward
motion through the water to pull the streamers and/or sources
outwardly and to maintain the transverse position relative to the
vessel path.
[0008] In 4-D geophysical imaging, a 3-D seismic survey is repeated
over a grid that has been previously surveyed. This series of
surveys taken at different times may show changes to the
geophysical image over time caused, for example, by extraction of
oil and gas from a deposit.
[0009] It is important that the source members being used to
generate the acoustical pulses be located as closely as possible to
the same location as in previous surveys over the same grid. This
has been difficult to accomplish in a marine survey because the
acoustical source members are typically towed behind the tow vessel
in source arrays, which are subject to wave and current
movement.
[0010] In addition to the deployment and operation difficulties
associated with towing multiple streamers and/or multiple source
arrays, conventional techniques limit the ability to position
source arrays and streamers in different relative positions and
orientations. Source array design is limited by the tow
configuration. Each towed source array is also subject to
crosscurrents, wind, waves, shallow water, and navigation obstacles
that limit the coverage provided by the survey system.
[0011] Attempts to control the location of seismic sources and
source arrays have included attaching distance ropes running to
lateral passive deflectors and tow cables; use of active
(steerable) deflecting members attached to the source tow cables in
front of the source arrays, or mid-way or at the aft end of the
source arrays; and use of passive lateral deflectors equipped with
a winch located near the front of the source. WO2004092771 A2,
published Oct. 28, 2004, (the '771 application) discloses the
latter two options. By attaching one or more steerable deflecting
members to the front, rear, or mid-section of one or more source
arrays, or a winch to the front of the source that acts on a
passive lateral deflector, the source array locations may be
controlled. Another method and device employs a source array
comprising a rigid bar mounted under a rigid or semi-rigid float
member, with the seismic source members, for example air-guns,
hanging below the rigid bar. FIGS. 1A and 1B illustrate plan and
side-elevation views, respectively, of this source array 100.
Source array 100 comprises a rigid steel or aluminum member 8
rigidly mounted to a rigid or semi-rigid float 10, which floats
near surface 12 of the ocean or other water body. Multiple source
members 14 are hung by chains or other means 16 from member 8, and
source array 100 is towed behind a seismic vessel (not shown) by a
strength-taking source umbilical 2 that is attached to a tow bridle
having two elements, a front element 4 attached to a front 5 of
member 8, while a second bridle element 6 is attached proximate a
mid-section 7 of member 8. The lengths of bridle elements 4 and 6
determines the orientation, or so-called angle of attack of member
8 and float 10 toward the incoming flow, F. Therefore, member 8 and
float 10 function as a low aspect ratio hydrofoil creating lateral
lift that enables source array 100 to be laterally deflected.
However, this method and apparatus offers no possibilities for
remotely adjusting the angle of attack.
[0012] The previous attempts have not provided optimal control of
the location of the source arrays under towing conditions. While
these techniques are improvements in the art, further improvement
is desired.
SUMMARY OF THE INVENTION
[0013] In accordance with the present invention, apparatus, systems
and methods are described for actively controlling position of
marine seismic sources and source arrays that reduce or overcome
problems with previous apparatus and methods. Apparatus and systems
of the invention comprise a source array, sometimes referred to
herein as a gun-array, the source array comprising one or more
source members, sometimes referred to herein as air-guns. As used
herein the term "source array" is meant to be broader than the term
gun-array, which those skilled in the art will recognize as meaning
one or more air-guns. The term "source member" is meant to be
broader than the term air-gun, and is meant to include all acoustic
sources, including, but not limited to, air-guns, oscillating
members, vibration members, explosive charges, percussion devices,
and the like. Thus, in the same way that a gun-array includes one
or more air-guns, a source array comprises one or more source
members. The terms gun-array, gun-string and sub-array are also
often used interchangeably in the art to call out an assembly of
components, including an array of air-guns, one or more floats,
chains, hang plates, everything required to position the gun-array
and have it functioning. The term source array will be used herein
for this assembly. Finally, the terms "source", "seismic source",
and "marine seismic source" are used interchangeably herein, unless
a specific embodiment requires a different meaning, and means one
or more source arrays comprising some or all source members (e.g.,
air-guns) fired at the same time. A source may comprise from one to
ten source arrays, more typically one to four source arrays. In
this regard, the art distinguishes between dual source and single
source. Dual source systems comprise two sources, each of say three
source arrays, where each source is located offset to the
centerline. A single source may comprise three source arrays where
the center of the source is located at the centerline.
[0014] A first aspect of the invention is an active, position
controllable marine seismic apparatus comprising: [0015] a source
array connected to a source tow member; and [0016] an adjustment
mechanism connected to the source array and source tow member, the
adjustment mechanism adapted to actively manipulate an angle of
attack of the source array. As used herein, "actively manipulate"
means controlling the angle of attack either directly or indirectly
in response to, and/or in anticipation of, an undesirable change in
movement of the source array. "Controlling" may be performed
locally on the source array, or remotely through any type of
communication system. "Angle of attack" means, when referring to a
seismic source array, the angle that the body of the source array
makes relative to the direction of flow of water past it, sometimes
referred to as the flow vector. This may also be described as the
angle that the body of the source array makes relative to its
direction of travel through the water. The flow vector may or may
not be parallel to the tow member.
[0017] The adjustment mechanism may be connected to the source
array at one or a plurality of tow points located on the source
array, and may include a towing harness. The tow point may be
located at a front end of the source array, or at a position
between the front end of the source array and a rear end of the
source array. The adjustment mechanism may comprise a deflecting
member positioned between the float and one or more of the source
members, and may further comprise a rigid moment-transfer member
having first and second portions, which may or may not be ends, the
first portion connected to the source tow member, the second
portion connected to a tow point on the deflecting member through a
swivel joint, where the swivel joint may be a hinged joint, ball
joint, or equivalent function joint. The adjustment mechanism may
further comprise an actuator mounted on the deflecting member near
the tow point and adapted to actuate the rigid moment-transfer
member. The rigid moment-transfer member may be a solid member or
hollow, and the solid and hollow members may be cylindrical
members, parallelepiped members, or equivalent functional members.
The rigid moment-transfer member may also be a telescoping member,
an I-beam, or other equivalent functional configuration.
[0018] The adjustment mechanism may comprise either a low or high
aspect ratio deflecting member positioned between, or in front of a
float and one or more source members. In this arrangement, the
adjustment mechanism may include a bridle system, and a rotatable
connector may be operatively connected to the deflecting member and
adapted to function with the bridle system. The rotatable connector
may be positioned on the deflecting member approximately at a
mid-section of the deflecting member. A local controller may be
mounted on the apparatus, the local controller adapted to receive a
signal from an on-board controller on a tow vessel or other remote
controller and send a signal to the local controller, which then
operates an actuator and rotatable connector. The bridle system may
comprise a front bridle leg attached to a front end of the
deflecting member, and an aft bridle leg comprising a loop that
passes through the rotatable connector, and thus the bridle system
may be remotely controllable. The bridle system may include a frame
that is connected to a front end of the deflecting member via a
swivel joint and adapted to pivot about the swivel joint, and the
frame may attach to an aft bridle leg comprising a loop that passes
through the rotatable connector. The frame may be a triangular
frame, or any other shaped frame that performs the equivalent
function of moving the bridle legs when actuated. Another
alternative is to replace all or substantial portions of the bridle
legs with linear actuators. In this latter embodiment, the
adjustment mechanism may be a combination of a frame, linear
actuators, and a high aspect ratio deflecting member, as further
explained herein.
[0019] The source array may comprise a float and one or more source
members attached to the float.
[0020] Apparatus of the invention may further comprise a local
controller mounted on the source array, the local controller
adapted to receive a signal comprising a desired angle of attack
from a remote controller, inform the adjustment mechanism of the
desired angle of attack, and signal an actuator to move the
adjustment mechanism accordingly. The adjustment mechanism may
further comprise a sensor able to measure the actual, or "real"
angle of attack of the source array and report this data to the
remote controller. Alternatively, rather than sensing and using the
real angle of attack of the source array, which may be difficult to
measure, the orientation of a component of the source array may be
sensed, for example the orientation of the source tow member, the
position of an actuator, or the like, and this data used to control
the adjustment mechanism.
[0021] The term "deflecting member" is to be distinguished from the
term "deflector." As used herein a "deflecting member" is a member
that is a component of and deflects a source. Deflecting members
useful in the invention may comprise a low aspect ratio member or a
high aspect ratio member. The deflecting member may be suspended
between the float and one or more of the source guns, or the
deflecting member may be rigidly attached to the float. In any
case, the deflecting member may be positioned between the float and
some or all of the source members, in front of the source array, or
at the aft end of a source array. The term "deflector" means a
discrete device or apparatus connected to the source via an active
or passive tow cable. Systems of the invention may include
deflecting members but not deflectors, deflectors but not
deflecting members, or both deflecting members and deflectors.
[0022] Another aspect of the invention are systems comprising a tow
vessel, a seismic source connected to the tow vessel by a source
tow member, and a remotely controllable deflector. Systems of the
invention may comprise many alternative arrangements for connecting
the tow vessel, source, and deflector, and all are considered
within the scope of the invention. As used herein the terms
"active" and "passive" refer to the ability and non-ability to
communicate, respectively, of a connection between a tow vessel and
a source, between a tow vessel and a deflector (with or with out
streamers), and between a source and a deflector (with and without
streamers). "Tow member", as used herein, may be an active or
passive connection device, and may be a strength-taking component
or non-strength-taking component. A strength-taking component is
one that is intended to pull, or help pull any of a source array, a
deflector, and/or a streamer. The term "umbilical" when used
without qualification means an active, power and/or data
transmitting tow member that is substantially non-strength-taking;
in other words an umbilical can withstand some tension, but is not
meant to pull a source array or deflector, unless it is a
strength-taking umbilical. Any combination of remotely controllable
deflector being connected to and towed by the tow vessel, or towed
by the source with and without connection to the tow vessel, and
any practical combination of passive tow member with an umbilical,
using both wherein at least one is a strength-talking tow member,
or using only a strength-taking umbilical if desired, are intended
to be within the invention. For example, the following non-limiting
embodiments are considered within the invention, wherein the
deflector is remotely controllable (wire or wireless) in each:
[0023] deflector connected to and towed by the tow vessel with a
passive strength-taking tow member, and either 1) a strength-taking
umbilical connecting the deflector to the source, or 2) a
combination of a passive, strength-taking tow member and an
umbilical; [0024] deflector connected to and towed by the tow
vessel with a strength-taking umbilical, and a passive tow member
extending from the deflector to the source; [0025] deflector
connected to and towed by the source by a strength-taking
umbilical, with no direct connection to the tow vessel; [0026]
deflector connected to and towed by the source by a combination of
a strength-taking passive tow member and an umbilical; and [0027]
deflector connected to and towed by the source by a passive,
strength-taking tow member, with an umbilical connecting the
deflector to the tow vessel. Notice that embodiments wherein the
remotely controllable deflector is not directly mechanically
connected to the tow vessel are considered within the invention.
There may be wireless or other non-mechanical transmission between
the deflector and tow vessel in such embodiments, and the
mechanical connection between deflector and source could be two
fold, either a combination of passive, strength-taking tow member
(for example chain, or rope) and an umbilical for transmitting
electrical power and/or signals, or a single strength-taking
umbilical able to take the loads and to transmit electrical power
and/or signals. Data transmission and electrical power could go
from vessel to source via umbilical and further to deflector via
umbilical.
[0028] The remotely controllable deflector may be any type of
deflector, including wing and boom arrangements, and door-type
deflectors, both of which are known in the art, as long as the
deflector is, or is modified to be, remotely controllable. One
useable deflector comprises a principal wing-shaped body shaped to
produce in use a sideways force which urges the marine seismic
source laterally with respect to the direction of movement of the
towing vessel, a boom extending rearward from the principal
wing-shaped body, and an auxiliary wing-shaped body, smaller than
the principal wing-shaped body, secured to an end of the boom
remote from the principal wing-shaped body and shaped so as to
produce in use a sideways force in generally direction opposite to
that produced by the principal wing-shaped body, and comprising a
remotely operable means for adjusting an angle between the boom and
the principal wing-shaped body to vary the sideways force produced
by the principal wing-shaped body. Another deflector useful in the
invention is a modified "door" type deflector, comprising a
plurality of passive hydrofoils mounted within a frame, and at
least one active hydrofoil mounted in the frame aft of the passive
hydrofoils, the active hydrofoil adapted to be moved and change an
angle of attack of the deflector using an actuator and controller
positioned in the frame, and through remote communication between
the controller and the tow vessel via an umbilical.
[0029] Another aspect of the invention comprises methods of
remotely controlling position of marine seismic sources, one method
comprising actively controlling an angle of attack of a marine
seismic apparatus relative to a reference using an adjustment
mechanism connected to the apparatus and a tow member. One method
of the invention includes sensing the angle of attack (or sensing a
parameter indicative of the angle of attack, such as an actuator
position) to obtain an acquired value, comparing the acquired value
to a desired value and adjusting the adjustment mechanism
accordingly. As with the apparatus of the invention, rather than
sensing and using the real angle of attack of the source array,
which may be difficult to measure, the orientation of a component
of the source array may be sensed, for example the orientation of
the source tow member, and this data used to control the adjustment
mechanism. In other methods of the invention, where the apparatus
is a source array comprising a float and one or more source members
generally below the float, the method further comprises providing a
deflecting member positioned between, in front, or behind the float
and one or more of the seismic signal guns, towing the apparatus
with a tow vessel using a tow member, and transferring moment from
a rigid moment-transfer member having first and second portions to
the deflecting member, the first portion connected to the tow
member, the second portion connected to a tow point on the
deflecting member through a swivel joint. Further methods of the
invention include actuating the rigid moment-transfer member using
an actuator mounted on the deflecting member near the tow point;
controlling the actuator using a local controller mounted on the
apparatus; and sending a signal from the tow vessel to the local
controller and sending a signal from the local controller to the
actuator. Other methods of the invention include towing the
apparatus with a tow vessel using a tow member wherein the tow
member comprises a bridle system, and transferring moment from the
bridle system to the deflecting member. Further methods of the
invention include actuating the bridle system using one or more
actuators mounted on the deflecting member near a tow point on the
deflecting member. Actuators may be rotatable or linear, for
example hydraulic or pneumatic cylinders connecting each bridle
member to the deflecting member. Actuators may be actuated using a
local controller mounted on the apparatus. A local sensor may sense
the position or status of an actuator and feed this information
back to the local and/or remote controllers. The local controller
may receive a signal from the tow vessel and send a signal to the
actuator.
[0030] Another method of the invention is used to remotely control
position of a marine seismic source, one method comprising towing a
source using a first strength-taking umbilical connected to a tow
vessel, and remotely controlling an angle of attack of a deflector
connected to the source by a second umbilical, and connected to the
tow vessel by a passive, strength-taking tow member, the deflector
positioned laterally from the source during seismic shooting.
Alternatively, a method of remotely controlling position of a
marine seismic source comprises towing a marine seismic source
array using a strength-taking umbilical connected to a tow vessel,
and remotely controlling position of a deflector connected to the
tow vessel by a second umbilical, and connected to the marine
seismic source array via a passive, strength-taking tow member, the
deflector positioned laterally from the source array during seismic
shooting. In these methods one may sense the angle of attack to
obtain an acquired a value, compare the acquired value to a desired
value, and adjust the deflector accordingly, or sense a parameter
indicative of the angle of attack, such as an actuator position
known by experience or experiments to indicate the relationship
between the actuator position and the resulting angle of attack.
The deflector may be adjusted by using an actuator mounted on the
deflector. The actuator may be actuated using a local controller
mounted on the deflector, which can send a signal from the tow
vessel to the local controller and send a signal from the local
controller to the actuator.
[0031] Further advantages and features of the invention will be
apparent upon review of the brief description of the drawings, the
detailed description of the invention, and the claims which
follow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] The manner in which the objectives of the invention and
other desirable characteristics can be obtained is explained in the
following description and attached drawings in which:
[0033] FIGS. 1A and 1B illustrate schematic plan and side-elevation
views, respectively, of a prior art marine seismic steering
apparatus and method;
[0034] FIGS. 2A and 2B illustrate schematic plan and side-elevation
views, respectively, of a first position controllable marine
seismic apparatus and method of the invention;
[0035] FIG. 3 illustrates a schematic side-elevation view of a
second position controllable marine seismic apparatus and method of
the invention;
[0036] FIG. 4 is a schematic diagram of a process control scheme
useful in the present invention for controlling position of seismic
sources using the apparatus and systems of the invention;
[0037] FIGS. 5A-C illustrate schematic plan views of position
controllable marine seismic apparatus and methods of the invention
employing bridle systems as part of the adjustment mechanism;
[0038] FIGS. 6A-C illustrate schematic plan views of position
controllable marine seismic apparatus and methods of the invention
employing frames as part of the adjustment mechanism;
[0039] FIG. 7 illustrates a schematic aerial plan view of a system
of the invention;
[0040] FIG. 8 illustrates a prior art wing-type deflector useful in
the invention;
[0041] FIG. 9 illustrates a schematic plan view, with portions cut
away, of a prior art door-type deflector;
[0042] FIG. 10 illustrates a schematic plan view, with portions cut
away, of the door-type deflector of FIG. 9 modified in accordance
with the invention; and
[0043] FIGS. 11A-F are simplified schematic diagrams illustrating
six non-limiting alternative tow member arrangements.
[0044] It is to be noted, however, that the appended drawings are
not to scale and illustrate only typical embodiments of this
invention, and are therefore not to be considered limiting of its
scope, for the invention may admit to other equally effective
embodiments.
DETAILED DESCRIPTION OF THE INVENTION
[0045] In the following description, numerous details are set forth
to provide an understanding of the present invention. However, it
will be understood by those skilled in the art that the present
invention may be practiced without these details and that numerous
variations or modifications from the described embodiments may be
possible.
[0046] The present invention relates to various apparatus, systems
and methods for controlling position of one or more marine seismic
components. The terms "controlling position", "position
controllable", "remotely controlling position", "remotely
adjustable", and "steering" are generally used interchangeably
herein, although it will be recognized by those of skill in the art
that "steering" usually refers to following a defined path, while
"controlling position", "position controllable", and "remotely
controlling position" could mean steering, but also could mean
merely maintaining a relative position, for example relative to one
or more reference points, such as natural or man-made objects, or
merely deflecting an object. As "position controllable" and
"controlling position" are somewhat broader terms than "steering",
these terms are used herein, except when specific instances demand
using more specific words. One aspect of the present invention
relates to position controllable apparatus. Other aspects of the
present invention, which are further explained below, relate to
methods for remotely controlling or adjusting position of marine
seismic sources.
[0047] As an example, FIGS. 2A and 2B illustrate plan and
side-elevation views, respectively, of a first position
controllable marine seismic source array 200 and method of the
invention. (The same numerals are used throughout the drawing
figures for the same parts unless otherwise indicated.) Source
array 200 comprises a plurality 202 of source members 14, for
example compressed air guns, which are fired to generate acoustical
waves that are reflected from the subsurface geological features
back to receivers (not shown) during a seismic exploration. Source
members 14 may be other acoustical-wave generation device, such as
explosives, percussion devices, and the like. Source array 200 is
towed after a seismic vessel (not illustrated) with a
strength-taking umbilical 2. Source members 14 may be suspended
from chains or other means 16 beneath a plate, beam or similar
member 8 that is rigid in at least the lateral plane. Member 8 is
in turn suspended from chains or other means 18 beneath a float 10,
or alternatively fixed tightly to float 10. Float 10 may be
flexible, semi-flexible or rigid. A rigid body 204, illustrated in
FIGS. 2A and 2B as a solid cylindrical rod (although other shapes
are possible), is fixed to member 8 by a swivel connection 206,
which may be a hinge, ball joint, or other type of equivalent
function joint. Swivel connection 206 allows rigid body 204 to
swing side-to-side as illustrated by double-headed arrow, S, in
FIG. 2A. Alternatively, rigid body 204 may comprise a frame (as
depicted in and further explained in relation to FIG. 6) or some
other structure able to swing and able to transfer moment from
umbilical 2 to member 8. An actuator 208 may be actuated by a
motor, 209, which is in turn controlled by a local controller 210
to ensure that swivel connection 206 comprises a stiff connection
and adjusts swing position, S, of rigid body 204 based on one or
more signals given from a vessel or other signal source (not
illustrated) through strength-taking umbilical 2. As rigid body 204
swings, the orientation of a tow-point 210 changes. The tension
from strength-taking umbilical 2 is transferred into a moment on
member 8 that causes source array 200 to position itself with an
angle of attack (.alpha.) with respect to incoming flow, F. This
positioning, and change of position, causes source array 200 to
position or re-position itself, typically laterally, although other
movements are possible.
[0048] FIG. 3 illustrates a schematic side-elevation view of a
second position controllable marine seismic source array 300 and
method of the invention. Comparing embodiment 300 with embodiment
200 of FIG. 2, note that member 8 in FIG. 2 is replaced with a
plate or hydrofoil-shaped body 302 having a higher aspect ratio
(ratio between height and length) that may result in better
deflection performance. However, note that deflection of member 302
need not be identical to the deflection of the source array it is
associated with, that is, the angle of attack of plate or hydrofoil
302 may be different than the angle of attack of the source array.
This is true whenever a deflection member has a length different
than the length of the source member. Plate or hydrofoil-shaped
body 302 is illustrated as suspended between float 10 and a hang
plate 304, however, body 302 could also be in front of or behind
float 10 and source members 14. Swivel connection 206 is provided,
as in embodiment 200 of FIG. 2, as are actuator 208, motor 209,
local controller 210, and rigid body 204, which may be mounted onto
plate or hydrofoil-shaped body 302 using any suitable means, such
as bolts, screws, weldments, and the like. A towing harness 306
connects strength-taking umbilical 2 and rigid body 204.
[0049] FIG. 4 is a schematic diagram of a control scheme useful
with all apparatus and methods of the present invention, for
example those depicted in FIGS. 2, 3, 5, 6, 8, 10, and 11, and is
not limited to any particular apparatus or method of the invention.
A positioning unit 11, mounted for example on source array 200
(FIG. 2A) transmits position of source array 200 to a navigation
system 17 located on the tow vessel (not illustrated). Navigation
system 17 provides the location information received from
positioning unit 11 to an on-board controller 32. On-board
controller 32 may be a computer, a distributed control system, an
analog control system or other control device known to those having
ordinary skill in the art. On-board controller 32 may communicate
with a local controller 210 through umbilical 2, but may
alternatively communicate through a wireless transmission.
Umbilical 2 contains conductors for providing power and control
signals to and from plate or hydrofoil-shaped body 302. Local
controller 210 sends a signal to an electric motor 31 that moves
actuator 208, which in turn moves plate or hydrofoil-shaped body
302. When plate or hydrofoil-shaped body 302 moves, the lateral
force imparted against it by the water steers source array 200 to
the desired position. Sensors 28 may detect the angular position of
plate or hydrofoil-shaped body 302 and send this information back
to local controller 210 and, optionally, to on-board controller 32
where it may be displayed for an operator to read.
[0050] FIGS. 5A and 5B illustrate schematic plan views of a third
position controllable marine seismic apparatus 500 and method of
the invention. Apparatus 500 builds on prior art apparatus 100
depicted schematically in FIG. 1, modified to make the bridle
system remotely adjustable. A source array, illustrated by member 8
only, is towed behind a seismic vessel (not illustrated) by
strength-taking umbilical 2. A bridle system comprised of a front
bridle leg 4 and aft bridle legs 6a and 6b is used in order to
achieve the desired angle of attack of member 8. Bridle legs 4, 6a,
and 6b may be the same or different in composition and may be
wires, cables, ropes, or any other material that can function as
described. Each of bridle legs 4, 6a, and 6b are connected to
strength-taking umbilical 2 at a point 9. Front bridle leg 4
connects to member 8 at a front point 5 and is substantially always
taught. Aft bridle legs 6a and 6b are routed through member 8 in a
loop as illustrated in FIGS. 5A and 5B. Position control (starboard
or port, as illustrated by the labeled arrows) is achieved by
maintaining one of bridle legs 6a and 6b taught (6a is taught in
port position, 6b is taught in starboard) while its complement
bridle leg is slack. Positioned on member 8 approximately at its
mid-section (could be anywhere along member 8) is a rotatable
member 207, for example a motor- or winch-driven pulley or
equivalent functioning means, that acts on bridle legs 6a and 6b so
as to rotate member 8 as illustrated by double-headed arrow S in
order to achieve the desired angle of attack. A local controller
210 that communicates with an on-board controller 32 (FIG. 4) on
the seismic vessel through umbilical 2 controls a motor 209, which
in turn moves actuator 208, and rotatable member 207.
Alternatively, rather than a motor- or winch-driven rotatable
actuator, one may simply employ a linear actuator, for example an
electric, hydraulic or pneumatic jack connected to a point between
bridle legs 6a and 6b to maintain one leg taught. Another
alternative to using a rotatable actuator would be to use a pair
linear actuators, for example a pair of hydraulic or pneumatic
piston/cylinder actuators, one each directly on bridle legs 6a and
6b, similar to the arrangement illustrated in and discussed below
in relation to FIG. 6C, which illustrates a high aspect ratio plate
or hydrofoil. The arrangement of embodiment 500 of FIG. 5A may be
employed as well with a high aspect ratio plate or hydrofoil as
depicted schematically in FIG. 5C. This figure illustrates
embodiment 500', including a high aspect ration plate or hydrofoil
302 moved to starboard deflecting position. All other elements in
embodiment 500' of FIG. 5C are equivalent to those of embodiment
500 depicted in FIG. 5A except that bridle legs 6a and 6b may be
shorter in embodiment 500' than in embodiment 500. The same
alternative arrangements may be employed in embodiment 500' as were
discussed in relation to embodiment 500 of FIGS. 5A and 5B,
including replacing the rotatable actuator with a linear actuator,
employing a frame, and employing a pair of linear actuators.
[0051] FIGS. 6A and 6B illustrate schematic plan views of a fourth
position controllable marine seismic apparatus 600 and method of
the invention. An adjustable bridle system comprising bridle legs
6a and 6b, rotating member 207, actuator 208, motor 209, and local
controller 210 are illustrated, with both bridle legs 6a and 6b
remaining substantially taught. Bridle legs 6a and 6b are connected
to a stiff frame 602 at points 608 and 606, respectively, and to
strength-taking umbilical 2 at point 604, so that frame 602 may
pivot about a swivel joint 610, which may be a hinge, ball joint,
or other equivalent function joint, positioned at front end of
member 8. An alternative (not shown) is to replace the combination
of rotating member 207, actuator 208, and motor 209 with a linear
actuator as discussed above in relation to FIGS. 5A and 5B. Another
alternative is to replace bridle legs 6a and 6b with linear
actuators, but closer to the frame 602, as illustrated in schematic
plan view in embodiment 600' of FIG. 6C. Embodiment 600' includes a
pair of piston/cylinder actuators 208a and 208b. Cylinder 208a is
attached to plate or hydrofoil 302, while its corresponding piston
208c is attached to frame 602 at point 606. Similarly, cylinder
208b is attached to plate or hydrofoil 302 and piston 208d is
attached to frame 602 at point 608.
[0052] Referring now to FIG. 7 there is illustrated a schematic
plan view of a marine seismic system 700 and method of the
invention. Illustrated schematically is a tow vessel 702 following
a desired path, which may be straight or curved, and one seismic
source 703 of a dual seismic source (the other source not shown)
showing a line of symmetry 705 between the two sources. Source 703
comprises three passive, non-steerable source arrays 707, each
source array 707 connected to tow vessel 702 through its own
strength-taking umbilical 2, and a deflector 704 that is connected
to seismic source 703 through an umbilical 706. Alternatively
umbilical 706 may be a passive, strength-taking member such as a
rope, wire, or equivalent passive connector, while deflector 704 is
towed by use of a separate strength-taking umbilical 3. Many
arrangements are possible, and are discussed separately and in
detail in reference to FIGS. 11A-F. By adjusting its angle of
attack, deflector 704 changes its lateral position, and this change
in position deflects seismic source 703 away from or back to a path
701 (shown as straight but could be curved), as desired by the
seismic survey team. In case of a dual source system, there would
be one source/deflector system as shown in FIG. 7 on each side of
the symmetry line 705. In case of a single source system (see FIGS.
11A-F) the source is positioned with its center at the symmetry
line 705 and with one deflector on each side enabling positioning
to either side of the symmetry line.
[0053] Deflectors useful in the invention may be any type of
deflector able to adjust its angle of attack, including so-called
free-flying deflectors, and non-free-flying deflectors that have
streamers or other trailing, drag-producing means. As used herein
the term "free-flying" means a deflector that is towed but does not
have suspended to its tail end a streamer or other drag-producing
device. In some situations it might be desired to include a
stabilizing tow member to an otherwise free-flying deflector.
[0054] FIG. 8 illustrates a schematic cross-section view of a prior
art free flying deflector 800 useful in the invention known under
the trade designation "MONOWING", available from WesternGeco
L.L.C., Houston, Tex. This particular embodiment of the deflector
includes a main hydrofoil 810, a boom 812 rigidly fixed to main
hydrofoil 810, and a so-called boom-wing 814 mounted near a rear
end 815 of boom 812. By rotating boom-wing 814 as depicted by
double-headed arrow R, it creates lift force in either positive or
negative direction. As illustrated in FIG. 8 a negative lift force
816 is achieved. However, this lift translates into a moment that
translates into a change of the orientation of main hydrofoil 810.
The orientation, or angle of attack .alpha., of main hydrofoil 810
is important, as the lift force 818 of main hydrofoil 810 is
directly proportional to .alpha., and proportional to the square of
the magnitude of the inflow velocity (indicated by arrow F). An
actuator 820 that communicates with a local controller 210 may
adjust the orientation of boom-wing 814. Communication with tow
vessel 702 (FIG. 7) is available through any of the combinations of
strength-taking umbilicals and non-strength-taking umbilicals
discussed herein (see discussion of FIGS. 11A-F). Local controller
210 may also communicate with on-board controller 32 (FIG. 4)
and/or other remote controller(s) via wireless transmission.
Deflectors useful in the invention may be suspended from or
attached rigidly to a float on the sea surface.
[0055] FIG. 9 illustrates a schematic plan view, with portions cut
away, of a prior art, so-called "door" deflector 900. This
deflector is often used to deflect a marine seismic source to a
nominal position. Three passive hydrofoils 910 (only the top ends
of which are viewable in this view) are suspended between a pair of
plates, a top plate 912 and a bottom plate 911, the latter of which
is viewable through the portions of top plate 912 that are cut
away. In three dimensions this comprises an array of hydrofoils
with end plates 912 and 911 at the top and bottom of each hydrofoil
910. A towing bridle or harness comprising four legs is required: a
front leg 930 and an aft leg 931 are illustrated attached to top
plate 912. Two additional bridle legs 930' and 931', one forward
and one aft, attach to bottom plate 911 but are not shown in this
view. All four bridle legs come together in one point 913. Attached
to bridle legs 930/931/930'/931' is a passive, strength-taking tow
member 3, from which door 900 is towed by a tow vessel. The angle
of attack .alpha. of door 900 is referenced to the inflow water
velocity vector, F, approaching door 900 and the relative lengths
between the front and aft bridle legs determine the angle .alpha..
As position of door 900 is a function of the angle of attack,
.alpha., the position of the door is not remotely adjustable.
[0056] FIG. 10 illustrates a schematic plan view, with portion cut
away, of a door-type deflector 950 of the invention, which is
similar to deflector 900 of FIG. 9, but modified in accordance with
the invention to make its angle of attack remotely controllable.
Aft bridle legs are not required, and a unit 951 is included that
includes a hydrofoil 814 with similar function as boom-wing 814 of
FIG. 8. The function of hydrofoil 814 is not to produce lift as the
hydrofoils 910 (FIG. 9), but to create a smaller lift force 816
that causes modified door 950 to orient itself with the desired
angle of attack .alpha. relative to incoming water flow velocity
vector, F. As the total lift 952 is a function of angle of attack
.alpha., total lift 952 may be adjusted by adjusting the
orientation and hence the lift of hydrofoil 814. The angle of
attack (orientation) of hydrofoil 814 may be adjusted by an
actuator 208 that is operatively coupled to a motor 209 and local
controller 210. Local controller 210 may communicate with on-board
controller 32 (FIG. 4) on the tow vessel through strength-taking
umbilical 3, or through umbilical 706 and strength-taking
tow-member 2 (not illustrated). Local controller 210 may also
communicate with on-board controller 32 and/or other remote
controller(s) via wireless transmission.
[0057] FIGS. 11A-F illustrate six non-limiting embodiments of how
one may arrange active, strength-taking tow members, passive
strength-taking tow members, and umbilicals (recall as defined
herein an umbilical is non-strength-taking unless indicated
otherwise). In each of FIGS. 11A-F, tow vessel 702 and seismic
source 703 are indicated as being connected by a strength-taking
umbilical 2. It will be understood that the functions of
strength-taking umbilical 2 could be divided into a passive,
strength-taking tow member and an umbilical in each of FIGS.
11A-F.
[0058] FIG. 11A illustrates an embodiment wherein a tow vessel 702
tows a single seismic source 703 and deflectors 704a and 704b. Tow
vessel 702 and each deflector 704a and 704b are connected using
respective passive, strength-taking tow members 3a and 3b. Source
703 is connected with deflectors 704a and 704b using respective
active, strength-taking tow members 706a and 706b.
[0059] FIG. 11B illustrates an embodiment identical to that of FIG.
11A except that active, strength-taking tow members 706a and 706b
are replaced by a combination of a passive, strength-taking tow
members 706a and 706b and umbilicals 706a' and 706b'.
[0060] FIG. 11C illustrates an embodiment that might be viewed as
the reverse of that of FIG. 11A. Tow members 3a and 3b are now
active, strength-taking tow members, while tow members 706a and
706b are passive, strength-taking tow members.
[0061] FIG. 11D illustrates an embodiment where there is no direct
mechanical connection between tow vessel 702 and deflectors 704a
and 704b. In this embodiment active, strength-taking tow members
706a and 706b connect source 703 with deflectors 704a and 704b,
respectively. The deflectors in this case are remote controlled
either through communications links in 706a, 706b, and 2' or
through wireless transmission.
[0062] FIG. 11E illustrates another embodiment where there is no
direct mechanical connection between deflectors and tow vessel.
Passive, strength-taking tow members 706a and 706b connect between
deflectors 704a and source 703, and deflector 704b and source 703,
respectively. Umbilicals 706a' and 706b' provide power and
optionally communication and data transmission links, and may
include other utilities such as compressed air, and the like.
[0063] FIG. 11F illustrates an embodiment where source 703 tows
deflectors 704a and 704b through passive, strength-taking tow
members 706a and 706b, respectively. Umbilicals 3a and 3b function
as power and, optionally, communications links between deflectors
704a, 704b, respectively and tow vessel 702.
[0064] In use the position of a deflecting member on a source, or
deflector associated with a source via umbilicals and/or passive
tow cables, is actively controlled by GPS or other position
detector sensing the position of the source or deflector and
feeding this data to a navigation system. Navigation may be
performed on board a tow vessel, on some other vessel, or indeed a
remote location. By using a communication system, either hardwire
or wireless, information from the remote controller is sent to one
or more local controllers on deflectors and/or deflecting members
of sources. The local controllers in turn are operatively connected
to adjustment mechanisms comprising motors or other motive power
means, and actuators on the deflectors and/or deflecting members,
which function to move a wing, plate or hydrofoil, or a bridle
system, depending on the adjustment mechanism used. This in turn
adjusts the angle of attack of the deflector or deflecting member,
causing it to move the source as desired. Feedback control may be
achieved using local sensors on the deflectors or deflecting
members, which may inform the local and remote controllers of the
position of a swivel connector, a wing or hydrofoil, the angle of
attack of a deflector or wing or hydrofoil of a particular boom
wing, a position of an actuator, the status of a motor or hydraulic
cylinder, the status of a bridle system, and the like. A computer
or human operator can thus access information and control the
entire positioning effort, and thus obtain much better control over
the seismic data acquisition process.
[0065] Although only a few exemplary embodiments of this invention
have been described in detail above, those skilled in the art will
readily appreciate that many modifications are possible in the
exemplary embodiments without materially departing from the novel
teachings and advantages of this invention. Accordingly, all such
modifications are intended to be included within the scope of this
invention as defined in the following claims. In the claims,
means-plus-function clauses are intended to cover the structures
described herein as performing the recited function and not only
structural equivalents, but also equivalent structures. Thus,
although a nail and a screw may not be structural equivalents in
that a nail employs a cylindrical surface to secure wooden parts
together, whereas a screw employs a helical surface, in the
environment of fastening wooden parts, a nail and a screw may be
equivalent structures. It is the express intention of the applicant
not to invoke 35 U.S.C. .sctn. 112, paragraph 6 for any limitations
of any of the claims herein, except for those in which the claim
expressly uses the words `means for` together with an associated
function.
* * * * *