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BACKGROUND
TECHNICAL FIELD
[0001] Embodiments of the subject matter disclosed herein generally relate to
methods and systems and, more particularly, to mechanisms and techniques for
5 improving and making more efficient a maintenance task associated with a headbuoy.
DISCUSSION OF THE BACKGROUND
[0002] Seismic data acquisition and processing generate a profile (image) of
10 geophysical structures under seafloor or subsoil. While this profile does not provide
an accurate location for oil and gas reservoirs, it suggests, to those trained in the
field, the presence or absence of them. Thus, providing a high-resolution image of
the structures under the seafloor/subsoil is an ongoing process.
[0003] To construct images of the subsoil (or subsurface), geologists or
15 geophysicists conventionally use, for example, wave emitters (sources) placed on
the surface. For the case of marine seismic surveys, the wave emitters are towed by
a vessel at or under the surface of the water. Such emitters emit waves (e.g.,
^ p acoustic waves) which propagate through the water (and subsoil for the land
seismic) and which are reflected on the surfaces of the various layers thereof
20 (reflectors). Waves reflected to the surface are recorded as a function of time by
receivers (which are towed by the same vessel or another vessel for the marine
seismic or lay on the ocean bottom). The signals received and recorded by the
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receivers are known as seismic traces. Based on the seismic traces, an image of
the surveyed subsurface is generated.
[0004] When performing a marine seismic survey, the receivers are placed
along a cable to form a streamer, and plural streamers are towed by a vessel. Such
5 a marine seismic survey having a towing vessel 10 is shown in Figure 1. Streamers
12 are shown in Figure 1 spreading over a predetermined area. This is called the
seismic spread. In order to maintain the plural streamers 12 substantially parallel
with each other, various front-end gears are used. Streamers 12 are spread out to a
desired width to provide measurements of the geological conditions over an
10 acquisition area.
[0005] An example of a front-end gear 30 is provided between the vessel 10
and the various streamers 12, and this gear is configured to achieve the desired
positioning for the streamer heads. Figure 1 shows the front-end gear 30 to include
lead-in cables 32 connected between the vessel 10 and deflectors 34. A deflector
15 34 is a structure capable of generating the necessary lift when towed to keep the
streamers deployed in the transverse direction with respect to the sailing line of the
towing vessel 10. Spacer lines 36 are provided between the streamers 12 for
obtaining a substantially linear profile for the position of the streamer heads.
^ p [0006] For maintaining the streamers 12 substantially parallel relative to a
20 reference plane (e.g., the water surface), as shown in Figure 2, traditionally, a headbuoy
40 is connected to a head portion 12A of the streamer 12 and a tail-float 42 is
connected at a tail portion 12B of the streamer 12. The head-buoy and tail-float
provide flotation to the streamer even if the streamer is buoyant neutral. The headbuoy
and tail-float are configured to float at the water surface 50 and corresponding
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cables 40A and 42A (for mechanical purposes) connect these elements to the
streamer to maintain the streamer at the desired depth H.
[0007] The head-buoy 40 is equipped with various equipment, e.g., acoustic
equipment for detecting positions of neighboring streamers and global positioning
5 system (GPS) equipment for determining an absolute position of the streamer. In
order to power the equipment, electric power generated on the towing vessel may be
transferred through an electric cable 52 to the head-float 40. The electric cable 52
and the cable 40A connect to the streamer 12 through a connection device 54.
[0008] From time to time, maintenance is required on the head-float because
10 its equipment requires constant checks. Such maintenance may be performed while
the head-buoy is deployed in the water, i.e., during a seismic survey. Such
environment makes the working conditions difficult for the maintenance personnel
due to, e.g., large waves, moving equipment, humid environment, etc. Also, the
maintenance may be time-consuming because the environmental conditions are not
15 appropriate.
[0009] Having the streamer spread deployed underwater and the seismic
survey stopped for head-buoy maintenance is highly undesirable because the cost of
the streamer spread is high. Thus, it would be desirable to provide systems and
^ P methods that avoid the afore-described problems and drawbacks, i.e., simplify
20 and/or expedite the maintenance of the head-float.
SUMMARY
[0010] According to one exemplary embodiment, there is a streamer headfloat
system connected to a head portion of a streamer or to a lead-in. The system
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includes: (A) a head-buoy configured to float in water and connected through a cable
to the head portion of the streamer or to the lead-in, (B) a head-float configured to
float in water, (C) a connector connecting the head-float to the head-buoy, and, (D)
positioning equipment on the head-float and configured to determine a position of the
5 streamer.
[0011] According to another exemplary embodiment, there is a head-float
associated with a head portion of a streamer or a lead-in towed underwater. The
head-float includes (A) a body configured to float in water, (B) a connector
connecting the head-float to a head-buoy, and (C) positioning equipment attached to
10 the head-float and configured to determine a position of the streamer or a position of
a source. The head-float does not provide floatation to the streamer.
[0012] According to another exemplary embodiment, there is a method for
performing a seismic survey. The method includes (A) towing a streamer, (B)
connecting a head-buoy to a head portion of the streamer or to a lead-in, and (C)
15 towing with the head-buoy a head-float configured to float in water. The method
further includes determining a position of the streamer with positioning equipment
attached to the head-float.
BRIEF DESCRIPTION OF THE DRAWINGS
20 [0013] The accompanying drawings, which are incorporated in and constitute
a part of the specification, illustrate one or more embodiments and, together with the
description, explain these embodiments. In the drawings:
[0014] Figure 1 is a schematic diagram of a traditional seismic survey;
[0015] Figure 2 is a side view of a streamer when deployed underwater;
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[0016] Figure 3 is a schematic diagram of a head-float system that includes
primary and head-floats according to an exemplary embodiment;
[0017] Figure 4 is a cross-section of a cable;
[0018] Figure 5 is a schematic diagram of primary and head-floats according
5 to an exemplary embodiment;
[0019] Figure 6 is a schematic diagram of a connector between primary and
head-floats according to an exemplary embodiment;
[0020] Figure 7 is a schematic diagram of another connector between primary
and head-floats according to an exemplary embodiment;
10 [0021] Figure 8 is a schematic diagram of a spread having one or more headbuoys
according to an exemplary embodiment;
[0022] Figure 9 is a flowchart of a method for towing primary and head-floats
according to an exemplary embodiment;
[0023] Figure 10 is a flowchart of a method for replacing a head-float
15 according to an exemplary embodiment;
[0024] Figure 11 is a schematic diagram of a head-buoy connected to a
seismic source;
[0025] Figure 12 is a schematic diagram of a head-buoy having a hydro-
^ p generator and a protective grid according to an exemplary embodiment;
20 [0026] Figure 13 is a schematic diagram of another head-buoy having a
hydro-generator and a protective grid according to an exemplary embodiment;
[0027] Figure 14 is a schematic diagram of still another head-buoy having a
hydro-generator and a protective grid according to an exemplary embodiment;
^
[0028] Figure 15 is a schematic diagram of a head-buoy having a rotatable
hydro-generator according to an exemplary embodiment; and
[0029] Figure 16 is a schematic diagram of a computing device.
5 DETAILED DESCRIPTION
[0030] The following description of the exemplary embodiments refers to the
accompanying drawings. The same reference numbers in different drawings identify
the same or similar elements. The following detailed description does not limit the
invention. Instead, the scope of the invention is defined by the appended claims. The
10 following embodiments are discussed, for simplicity, with regard to the terminology and
structure of a head-float that is connected to a head-buoy.
[0031] Reference throughout the specification to "one embodiment" or "an
embodiment" means that a particular feature, structure or characteristic described in
connection with an embodiment is included in at least one embodiment of the subject
15 matter disclosed. Thus, the appearance of the phrases "in one embodiment" or "in an
embodiment" in various places throughout the specification is not necessarily referring
to the same embodiment. Further, the particular features, structures or characteristics
may be combined in any suitable manner in one or more embodiments.
1 ^ [0032] According to an exemplary embodiment, a head portion of a streamer
20 is attached by a cable to a head-buoy for providing floatability. A head-float is
detachably attached to the head-buoy. The head-float is not intended to provide
floatability to the streamer. In one application, there is no direct connection between
the head-float and the streamer. Various equipment (e.g., acoustic, GPS, etc.) that
is traditionally on the head-buoy is now moved in the head-float. The head-buoy still
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provides floatability for the streamer. When maintenance of the equipment is
necessary, because the equipment is now on the head-float and not on the headbuoy,
the head-float may be disconnected from the head-buoy and replaced with a
working head-float.
5 [0033] Thus, the maintenance operations are essentially moved from the sea
to the vessel because the head-float may be towed to the vessel and there the
maintenance may be performed while the seismic survey is not interrupted. Thus,
the down-time of the seismic survey is reduced by using the novel embodiment. The
reduced down-time may include the time for sending a boat with maintenance
10 personnel to the head-float, disconnecting the head-float from the head-buoy,
attaching a new head-float to the head-buoy, and retrieving the head-float on the
vessel. However, the reduced down-time does not include the time necessary for
replacing or fixing the equipment in the head-float.
[0034] The novel features are now discussed in more detail with regard to a
15 few exemplary embodiments. According to an exemplary embodiment illustrated in
Figure 3, a seismic survey system 100 includes a towing vessel 102 and at least one
streamer 104. The streamer 104 is connected to the towing vessel 102 with a frontend
gear 106 (e.g., a lead-in that connects the streamer to the vessel). A head-buoy
110 is attached with a cable 112 (that may include both a cable or chain to provide
20 mechanical strength and a cable to provide electrical and/or data transfer) to a
connecting part 113 at a front portion 104A of the streamer 104, and a tail float 114
is attached with a cable 116 to a tail portion 104B of the streamer. Cable 112 may
be attached to the lead-in 106 instead of the front portion 104A of the streamer and
thus, the connecting part 113 may be between the streamer and the lead-in 106. In
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addition, a head-float 120 is attached through a connection 122 to the head-buoy
110. The connection 122 may be a detachable connection, as discussed later, so
that maintenance personnel may easily detach the head-float from the head-buoy
while on the sea. In one application, the connection may be remotely controlled from
5 a maintenance boat 130 so that by simply pressing a button on the remote control,
the head-float detaches by itself from the head-buoy. In another application, the
connection is not detachable, i.e., it is fixed.
[0035] As illustrated in Figure 4, the connection 122 may include a cable 122A
configured to withstand the tension present in the connection 122. Cable 122A may
10 be distributed as a single cable as shown in Figure 4 or it may be distributed inside
or outside the connection 122 in various strands. A data communication cable 122B
may also be provided through the connection 122 for supporting data transmission
between the head-float and the head-buoy or the streamer. An electric power cable
122C may also be provided through the connection 122 for transmitting electric
15 power between the head-float and the head-buoy.
[0036] In one exemplary embodiment illustrated in Figure 5, a streamer headfloat
system 135 includes a head-buoy 110 connected to a head-float 120. It is
noted that the head-float 120 is discussed herein in the context of being attached to
^ p the head-buoy 110 of a streamer. However, the novel features of the head-float may
20 also be applied to a head-float attached to a seismic source or another seismic
device or element, for example, a tail buoy, a deflector or a lead-in. The head-buoy
110 has no GPS or acoustic equipment because this equipment is moved onto the
head-float 120. However, in another exemplary embodiment, the head-buoy 110
may include one or more of this equipment. The head-buoy 110 may have an
^
actuator 112A for adjusting a length of the cable 112 (connected to the streamer)
and no other equipment. This is a minimal equipment configuration for the headbuoy
110. In another application, the head-buoy 110 may include a battery 140 for
powering the actuator 112A. The actuator 112A may be, for example, a winch. The
5 actuator 112A is used to control the length of the cable 112, and thus, to control a
depth of the streamer (not shown) attached to the cable 112.
[0037] Further, in another application, a control device 142 may be provided
inside the head-buoy. The control device 142 may be configured to receive data
from the streamer 104, through the cable 112, or wireless from the towing vessel
10 102, for controlling a depth position of the streamer. Thus, in this last exemplary
embodiment, the head-buoy 110 is capable of adjusting a depth position of the
streamer or lead-in independent of the presence or not of the head-float.
[0038] The head-float 120 has a body 121 that is configured to house one or
more positioning devices for determining the position of the streamer relative to other
15 streamers and/or its absolute position. Such positioning devices may include a GPS
(or other similar device that uses the air as medium) system 150, which provides an
absolute position relative to earth, and/or an acoustic system (or other systems for
determining relative positions of other streamers and which uses the water as
^ p medium, a passive acoustic monitoring system) 152, which provides a relative
20 position of the buoy to the streamers or a position of one streamer to another
streamer. In one application, the GPS system 150 is provided on top of the headfloat
while the acoustic system 152 is provided on the bottom of the head-float.
Although Figure 5 shows these devices provided inside the head-float, it is noted that
these devices may be partially or totally provided on the outside of the head-float.
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Further devices and/or systems may be provided on and/or in the head-float as now
discussed.
[0039] For example, a battery 154 may be provided inside the head-float for
powering the GPS and acoustic systems. Optionally, if the head-buoy 110 does not
5 have an electric power source or cannot receive electrical power directly from the
streamer, the battery 154 may provide electrical power to the actuator 112A through
the connection 122. A controller 156 (e.g., a processor and/or a memory) may be
provided for controlling/coordinating the GPS, acoustic systems, battery and other
equipment on the head-float, e.g., for deciding when to recharge the battery. The
10 battery 154 may be charged with a solar panel 158 provided on a top portion of the
float, or a fuel cell 160, or with a generator (or hydro-generator) 162 that has a
propeller 163 that is rotated when the head-float is towed by the vessel, or by a
device that harvests the energy of the ocean waves, or by a combination of these
devices. Therefore, for this exemplary embodiment, no power cable is necessary
15 from the streamer to the head-buoy 110 and through the connection 122 to the headfloat
120. Thus, for this configuration, the cable 112 does not include a cable to
transmit power and/or data. Still for this embodiment, a data transmitting device 161
may be provided for exchanging data with the vessel. The data transmitting device
161 may be an acoustic modem or radio device that communicates with a
20 corresponding device and a server or computing device of the vessel. The data
transmitting device 161 may be used to communicate, in real time, with the vessel to
share the positions of the streamers (absolute and relative positions acquired with
GPS 150 and acoustic system 152). In this way, the streamers may be positioned
as desired. In this regard, it is noted that a central control device on the vessel may
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instruct birds attached to the streamers to position the streamers based on the data
collected by the GPS 150 and/or the acoustic system 152. In another application, a
power/data cable may be connected between the streamer and the head-float.
[0040] The head-float 120 may also include one or more fins 164 for
5 controlling the direction of the head-float. The fin may be connected to an actuator
166, for example, an electric motor, for adjusting an orientation of the fin. The fin
may be disposed vertically or horizontally or to make a desired angle with the body
of the head-float. Other equipment may be added to the head-float as would be
recognized by those skilled in the art.
10 [0041] Returning to the connector 122, it is noted that there are various
possibilities for connecting the head-buoy 110 to the head-float 120. For example,
as illustrated in Figure 6, the connector 122 may have a first portion 122A that is
fixedly attached to the head-float 120, and a second portion 122B that is fixedly
attached to the head-buoy 110. Each portion of the connector 122 may have a
15 corresponding male or female portion 180A and 1808 for achieving the electrical
and/or mechanical connection of the portions 122A and 122B. In one application,
the male and female connection portions 180A and 180B may be provided with
electric devices 182A and 1828 that may be remotely disconnected from each other.
In one application, existing head-buoys are retrofitted with the connection portion
20 180B so that a head-float may be attached to the head-buoy when, for example, the
head-buoy has maintenance problems. As noted above, when the head-float is
attached to the head-buoy, the head-float may provide electrical power or data
communication capabilities to the head-buoy, especially if the head-buoy has failed
with one or more of these functions.
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[0042] In another exemplary embodiment illustrated in Figure 7, the entire
connector 122 is attached to the head-buoy 110, and the free end of the connector
122 has a male or female part 184Athat connects to a corresponding part 184B
attached to the head-float 120. It is also possible that the entire connector 122 is
5 connected to the head-float 120, and the head-buoy 110 has a male or female part
for connecting to the connector 122.
[0043] The body 121 of the head-float may be made of a material that is
resistant to humid and corrosive environments, for example, plastic, composite,
aluminum, stainless steel, etc. The body may be made to have a cavity inside which^
10 all or part of the equipment may be provided. An access door may be provided to
the cavity to access the equipment for maintenance and to protect it from water
droplets.
[0044] Regarding the positioning of the streamer 104 according to the
requirements of the seismic survey, it is shown in Figure 8, a bird view of the plural
15 streamers 104 being towed by the vessel 102. As an example, two head-buoys 110-
1 and 110-2 are shown connected to the head of corresponding streamers. Figure 8
also shows two head-floats 120-1 and 120-2 similar to those discussed with regard
to Figures 3-7. The head-floats may include a GPS system, a local positioning
^ p system, a data transmission system for exchanging data with the vessel and a power
20 source. Figure 8 also shows multiple acoustic transceivers 190; that are configured
to send acoustic signals 191 to other transceivers, located on the streamers and/or
the other head-floats, and to determine the positions of the streamers relative to
each other. Having determined the absolute positions of the two head-floats (using
the GPS system 150) and the positions of the streamers relative to the head-floats
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(using the local positioning system 152), the controller on the vessel can
calculate/determine the actual positions of the streamers and may instruct
accordingly the birds 192; (distributed along one or more streamers) to adjust the
positions of the streamers to follow the predefined path.
5 [0045] It is noted that in one exemplary embodiment, only one head-float may
be used to determine the absolute location of the streamers relative to the earth.
However, with only one head-float, the entire streamer arrangement may turn around
the head-float, thus, making the location of the streamer arrangement inaccurate. To
prevent this situation, at least two head-floats equipped with the GPS system, local
10 positioning system and the data communication system may be used as shown in
Figure 8. For an improved accuracy, one or more tail-floats 120a, similarly equipped
as the head-floats, may be provided toward a tail portion of the streamers.
According to still another exemplary embodiment, instead of, or in addition to, the
local positioning system 152, a ultra short base line (USBL) system 168 (as shown in
15 Figure 5) may be used to determine the position of the streamers relative to each
other and/or to the head-float. A master or base of the USBL may be mounted on
one or more head-buoys (or one the vessel) while the pingers may be mounted on
one or more streamers, on the source, on the deflectors or on any other equipment
^ p at sea, underwater, above water, etc.
20 [0046] The head-float and the head-buoy may be used to perform a seismic
survey as discussed next. According to an exemplary embodiment illustrated in
Figure 9, a method for performing a seismic survey includes a step 900 of towing a
streamer, a step 902 of supporting with a head-buoy a head portion of the streamer
or a lead-in, a step 904 of towing with the head-buoy a head-float configured to float
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in water, and a step 906 of determining a position of the streamer with positioning
equipment attached to the head-float. The head-buoy may be free of any positioning
equipment.
[0047] According to another exemplary embodiment illustrated in Figure 10,
5 there is a method for replacing a head-float while being deployed on the water for a
marine seismic survey. The method includes a step 1000 of towing a streamer, a
step 1002 of supporting with a head-buoy a head portion of the streamer or a lead-in,
a step 1004 of towing with the head-buoy the head-float, wherein the head-float is
configured to float in water, and a step 1006 of detaching the head-float from the
10 head-buoy for maintenance. Alternatively, the step 1006 may include moving the
head-float (if the head-float is small enough) on the maintenance vessel without
detaching it from the head-buoy.
[0048] The above embodiments have been discussed with regard to providing
at least a head-float next to a head-buoy that is connected to a streamer. However,
15 the novel embodiments are equally applicable to a head-buoy connected to a
seismic source, as illustrated in Figure 11. Other possibilities include attaching the
head-float to a deflector (or paravan) to monitor the position of the deflector, thus
helping monitoring the streamers, or adding the head-float to a slider that slides
^ p along a wide-tow or to a prepositioned attachment on the wide-tow. The deflectors
20 are known in the art for being used to, e.g., space the heads of the streamers apart
from each other.
[0049] The system 200 in Figure 11 shows a vessel 202 that tows a seismic
source 204. The seismic source 204 may include multiple sub-arrays, one sub-array
having a float 206 and plural guns 208. A head-float 210, similar to the one
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discussed in the previous embodiments, is attached through a connection 212 to the
float 206. For this embodiment, the head-float 210 may include an acoustic system
214 for providing a more accurate position of the seismic source or other equipment
attached to the source or around the source. The acoustic system 214 may be an
5 ultra short base line (USBL) device that is capable of acoustic positioning an
underwater object. The acoustic system 214 may also be provided on the head-float
120.
[0050] The hydro-generator 162 and its novel features are now discussed with
regard to Figure 12. Figure 12 shows a head-float 300 that may have all or part of
10 the components discussed with regard to the head-float 120. For simplicity. Figure
12 only shows the hydro-generator 162 and its propeller 163. However, it is possible
to have more than one hydro-generator. For example, in one embodiment, the
head-float has two generators symmetrically located on the body of the head-float
and the propellers of the two hydro-generatos may be configured to rotate in
15 opposite directions to reduce/eliminate a resulting torque on the head-float. It is
noted that if the head-float advances along axis X, the propeller 163 may be behind
the hydro-generator as shown in the figure or in front of the hydro-generator. A
protection grid 302 may be added to the hydro-generator 162 to enclose the
^ p propeller 163 for protecting it from debris, marine animals (e.g., sea turtles), etc. The
20 protection grid 302 may be manufactured to have openings sized to be smaller than
a size of the animals and/or debris to be avoided. In another embodiment, the shape
of the protection grid 302 is made to promote the debris and/or animals to slide past
it (e.g., aerodynamic shape). In still another exemplary embodiment, an attachment
mechanism 304 may be used to attach the protection grid 302 to the hydro-generator
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162 and the attachment mechanism 304 may be configured to rotate relative to the
hydro-generator 162. In this way, the controller 156 may instruct the attachment
mechanism 304 to rotate to clean the protection grid 302. The attachment
mechanism may be activated by its own motor powered by the battery of the head-
5 float, the hydro-generator or by both of them.
[0051] In another embodiment illustrated in Figure 13, a head-float 400 has a
protection grid 402 that is located in front of the impeller 163 when advancing along
the traveling direction X. The protection grid 402 may be attached through a portion
404 to the body 401 of the head-float 400. In one application, a motor 406 is
10 provided inside the head-float 400 and attached to the portion 404 for rotating back
and forth the protection grid 402. The motor 406 may rotate the protection grid along
arrow 408. In one application, the motor may rotate the protection grid 402 by 10
degrees (other angles may be used) in each direction. In this way, the protection
grid may be cleaned.
15 [0052] Further, the portion 404 may prevent debris and/or marine animals to
get trapped between the body 401 of the head-float and the hydro-generator 162. In
one application, the portion 404 is a simple rod. However, in another application, the
portion 404 is a mesh. The protection grid 402 may have different shapes. One
^ p example shown in Figure 13 includes two mesh surfaces (planar or curved) that are
20 connected together at the portion 404. Other shapes for the protection grid may be
used. In another application, the portion 404 does not contact the body 401 of the
head-float 400. In this case, the protection grid may be attached to the hydrogenerator,
as already discussed above.
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[0053] In still another embodiment illustrated in Figure 14, a protection grid
502 may be attached to the body 501 of the head-float 500 or to the hydro-generator.
The protection grid 502 may include a stationary grid 504 that is physically attached
to the body or to the hydro-generator, or to both, and a movable grid 506 provided in
5 close proximity to the stationary grid 504. The stationary grid 504 may be attached
to make an angle with the body of the head-float to promote removal of kelp, debris,
etc. The movable grid 506 may be provided inside or outside the stationary grid 504.
Figure 14 shows a single movable grid 506 for simplicity. However, more than one
movable grid may be provided next to the stationary grid.
10 [0054] The movable grid 506 is configured to rotate relative to the stationary
grid 504. Thus, the movable and stationary grids may have a cylindrical shape. One
or more paddles 512 may be located on the movable grid 506 to generate the
rotation motion under the water action. The movable grid 506 may be kept in place,
next to the stationary grid 504 by various mechanisms, for example, each grid has a
15 track that engages the other grid's track. More movable grids may be provided on
the stationary grid to cover most of the stationary grid. However, the movable grids
should be able to rotate without touching the hydro-generator. Figure 14 shows the
protection grid 502 enclosing only the propeller. In another exemplary embodiment,
^ p the protection grid may be designed to also enclose the hydro-generator 162. The
20 stationary grid 504 may be attached with an attachment 508 to the body 501 of the
head-float. In another application, the stationary grid 504 may be attached with an
attachment 510 to the hydro-generator 162. In still another exemplary embodiment,
the stationary grid 504 may be attached to both the body of the head-float and the
hydro-generator.
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[0055] In still another embodiment, the controller 156 may be configured to
monitor the power generated by the hydro-generator and when this power falls below
a predetermined threshold (which indicates that debris or other things are reducing
the flow of water to the propeller), to instruct the attachment mechanism 304 or the
5 motor 406 to rotate the protection grid for cleaning purposes.
[0056] In yet another exemplary embodiment illustrated in Figure 15, a headfloat
600 may have a protection grid 602 distributed around the impeller 163 of the
hydro-generator 162. To move (rotate, translate or both) of the protection grid, which
may be fixedly attached to the hydro-generator 162, the entire hydro-generator may
10 be rotated by a motor 604 located inside the body 601 of the head-float 600. For all
the above discussed embodiments, the controller 156 may coordinate the rotation of
the protection grid, the measurement of the power generated by the hydro-generator,
communication with the vessel, etc.
[0057] In still another exemplary embodiment, there is a head-float associated
15 with a head portion of a streamer or a lead-in towed underwater. The head-float
includes a body configured to float in water; a connector connecting the head-float to
a head-buoy; and positioning equipment attached to the head-float and configured to
determine a position of the streamer or a position of a source. The head-float does
( ^ not provide floatation to the streamer. In one application, the head-buoy is free of
20 any positioning equipment and the head-buoy is configured to connect through a
cable to the head portion of the streamer or to the lead-in. In another application, the
connector includes first and second connecting parts configured to disconnect from
each other to separate the head-buoy from the head-float. The positioning
equipment may include an acoustic system configured to determine a position of the
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streamer relative to adjacent streamers; and/or a global positioning system
configured to determine an absolute position of the streamer. The head-float may
further include a power supply configured to generate energy; and a data
transmission device configured to exchange data with a vessel that tows the
5 streamer. The power supply is configured to supply the head-buoy with power and
there is no electric power cable between the streamer or the lead-in and the headbuoy.
The head-float may include at least one fin for controlling a traveling direction.
[0058] In one application, the head-float is not directly attached to the
streamer or the lead-in. The head-float may also include a hydro-generator
10 configured to generate energy by rotating a propeller; and a protection grid for
protecting the propeller from debris and/or marine animals. The protection grid is
configured to move relative to a body of the head-float to clean the protection grid.
The head-float may also include a controller for sensing a power produced by the
hydro-generator and for controlling a movement of the protection grid based on the
15 sensed power.
[0059] The methods discussed above may be implemented in dedicated
devices (e.g., dedicated networks or computers or cloud-computing networks, etc.)
for being performed. A combination of software and hardware may be used to
^ P achieve the event-related transversal isotropic axis and/or an associated tilt model.
20 A dedicated machine that can implement one or more of the above-discussed
exemplary embodiments is now discussed with reference to Figure 16.
[0060] An exemplary computing arrangement 1600 suitable for performing the
activities described in the exemplary embodiments may include server 1601. Such a
server 1601 may include a central processor (CPU) 1602 coupled to a random
20
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^
access memory (RAM) 1604 and to a read-only memory (ROM) 1606. The ROM
1606 may also be other types of storage media to store programs, such as
programmable ROM (PROM), erasable PROM (EPROM), etc. The processor 1602
may communicate with other internal and external components through input/output
5 (I/O) circuitry 1608 and bussing 1610, to provide control signals and the like. The
processor 1602 carries out a variety of functions as are known in the art, as dictated
by software and/or firmware instructions.
[0061] The server 1601 may also include one or more data storage devices,
including hard and floppy disk drives 1612, CD-ROM drives 1614, and other
10 hardware capable of reading and/or storing information such as DVD, etc. In one
embodiment, software for carrying out the above-discussed steps may be stored and
distributed on a CD-ROM 1616, removable media 1618 or other form of media
capable of portably storing information. These storage media may be inserted into,
and read by, devices such as the CD-ROM drive 1614, the disk drive 1612, etc. The
15 server 1601 may be coupled to a display 1620, which may be any type of known
display or presentation screen, such as LCD, plasma displays, cathode ray tubes
(CRT), etc. A user input interface 1622 is provided, including one or more user
interface mechanisms such as a mouse, keyboard, microphone, touchpad, touch
screen, voice-recognition system, etc.
20 [0062] The server 1601 may be coupled to other computing devices, such as
the landline and/or wireless terminals and associated applications, via a network.
The server may be part of a larger network configuration as in a global area network
(CAN) such as the Internet 1628, which allows ultimate connection to the various
landline and/or mobile client/watcher devices.
21
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[0063] As also will be appreciated by one skilled in the art, the exemplary
embodiments may be embodied in a wireless communication device, a computer
network, as a method or in a computer program product. Accordingly, the exemplary
embodiments may take the form of an entirely hardware embodiment or an
5 embodiment combining hardware and software aspects. Further, the exemplary
embodiments may take the form of a computer program product stored on a computerreadable
storage medium having computer-readable instructions embodied in the
medium. Any suitable computer-readable medium may be utilized including hard disks,
CD-ROMs, digital versatile disc (DVD), optical storage devices, or magnetic storage
10 devices such a floppy disk or magnetic tape. Other non-limiting examples of computer
readable-media include flash-type memories or other known memories.
[0064] The disclosed exemplary embodiments provide a system and a method
for reducing the down-time associated with equipment maintenance of a head-float.
It should be understood that this description is not intended to limit the invention. On
15 the contrary, the exemplary embodiments are intended to cover alternatives,
modifications and equivalents, which are included in the spirit and scope of the
invention as defined by the appended claims. Further, in the detailed description of
the exemplary embodiments, numerous specific details are set forth in order to
^ p provide a comprehensive understanding of the claimed invention. However, one
20 skilled in the art would understand that various embodiments may be practiced
without such specific details.
[0065] Although the features and elements of the present exemplary
embodiments are described in the embodiments in particular combinations, each
feature or element can be used alone without the other features and elements of the
22
^
embodiments or in various combinations with or without other features and elements
disclosed herein.
[0066] This written description uses examples of the subject matter disclosed to
enable any person skilled in the art to practice the same, including making and using
any devices or systems and performing any incorporated methods. The patentable
scope of the subject matter is defined by the claims, and may include other examples
that occur to those skilled in the art. Such other examples are intended to be within the
scope of the claims.
10
23

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'/We Claims: iJ ^ ^ -7 5 UO^ W^
1. A streamer head-float system connected to a head portion of a streamer or
to a lead-in, the system comprising:
a head-buoy configured to float in water and connected through a cable to the
head portion of the streamer or to the lead-in;
a head-float configured to float in water;
a connector connecting the head-float to the head-buoy; and
positioning equipment on the head-float and configured to determine a
position of the streamer.
2. The system of Claim 1, wherein both the head-buoy and the head-float are
configured to float at the water surface and the connector is a detachable
connectors.
15 3. The system of Claim 1, wherein the connector includes first and second
connecting parts configured to disconnect from each other to separate the headbuoy
from the head-float.
^ p 4. The system of Claim 1, wherein the head-buoy further comprises:
20 an actuator device configured to actuate the cable to adjust the given depth of
the streamer.
5. The system of Claim 4, wherein the head-buoy further comprises:
24
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a battery connected to the actuator device and configured to actuate the , ^. i O^y
actuator device.
6. The system of Claim 1, wherein the positioning equipment comprises:
5 an acoustic system configured to determine a position of the streamer relative
to adjacent streamers; and/or
a global positioning system configured to determine an absolute position of
the streamer.
10 7. The system of Claim 6, wherein the head-float further comprises:
a power supply configured to generate energy; and
a data transmission device configured to exchange data with a vessel that
tows the streamer.
15 8. The system of Claim 7, wherein the power supply is one of a battery, a
solar panel, a fuel cell, a wave energy converter, or a hydro-generator.
9. The system of Claim 1, wherein the head-float further comprises:
( ^ a hydro-generator configured to generate energy by rotating a propeller; and
20 a protection grid for protecting the propeller from debris and/or marine
animals.
10. A head-float for providing position information associated with a seismic
source towed underwater, the head-float comprising:
25
-jg0'
a body configured to float in water; ^\S
a connector connecting the head-float to a float of the seismic source; and
positioning equipment attached to the head-float and configured to determine
a position of the seismic source or a seismic streamer.