U.S. patent application number 15/968596 was filed with the patent office on 2018-10-18 for seismic data acquisition system with selectively enabled sensor units, and associated methods.
The applicant listed for this patent is PGS Geophysical AS. Invention is credited to Claes Nicolai BORRESEN, Stig Rune Lennart TENGHAMN.
Application Number | 20180299574 15/968596 |
Document ID | / |
Family ID | 45220040 |
Filed Date | 2018-10-18 |
United States Patent
Application |
20180299574 |
Kind Code |
A1 |
BORRESEN; Claes Nicolai ; et
al. |
October 18, 2018 |
SEISMIC DATA ACQUISITION SYSTEM WITH SELECTIVELY ENABLED SENSOR
UNITS, AND ASSOCIATED METHODS
Abstract
A disclosed seismic survey system includes one or more
streamer(s) each having multiple spaced apart sensor units, and a
data recording and control system. Each sensor unit receives a
command from the data recording and control system, and operates in
an enabled state or a disabled state dependent upon the command.
The data recording and control system collects and stores data from
enabled sensor units. The sensor units produce data when in the
enabled state, and dissipate significantly less electrical power in
the disabled state. A described sensor unit includes one or more
sensor(s), an analog-to-digital converter, and a control unit that
enables or disables the analog-to-digital converter dependent upon
the command. A disclosed method for acquiring seismic survey data
includes issuing an enable or disable command to each of multiple
spaced apart sensor units, and receiving and storing data from
those sensor units that are enabled.
Inventors: |
BORRESEN; Claes Nicolai;
(Katy, TX) ; TENGHAMN; Stig Rune Lennart;
(Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PGS Geophysical AS |
Oslo |
|
NO |
|
|
Family ID: |
45220040 |
Appl. No.: |
15/968596 |
Filed: |
May 1, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12803503 |
Jun 29, 2010 |
10001575 |
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15968596 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01V 1/3808
20130101 |
International
Class: |
G01V 1/38 20060101
G01V001/38 |
Claims
1. A method for acquiring seismic survey data, comprising:
generating a configuration table that specifies an enabled/disabled
state for each of a plurality of spaced apart sensor units; using
the configuration table to issue an enable or disable command to
each of said plurality of spaced apart sensor units in a marine
seismic streamer to provide a compressed sensing arrangement of
enabled sensor units; triggering a seismic shot; receiving data
from those sensor units that are enabled; and storing the data.
2. The method as recited in claim 1, wherein the sensor units are
arranged to span a two-dimensional area.
3. The method as recited in claim 1, wherein the sensor units
dissipate substantially more electrical power in the enabled state
than in the disabled state.
4. The method as recited in claim 1, wherein the command comprises
at least one binary digit, and wherein the at least one binary
digit specifies whether a receiving sensor unit is to be placed in
the enabled state or the disabled state.
5. The method as recited in claim 1, wherein each of the sensor
units has a unique address, and wherein the issuing of the command
to each of the sensor units is carried out using the addresses of
the sensor units.
6. The method as recited in claim 1, wherein the generating
comprises: for each of the sensor units: producing a random number
between 0 and 1; if the random number is between 0 and a
predetermined threshold value, indicating in the configuration
table that the sensor unit is to be enabled; and if the random
number is not between 0 and the predetermined threshold value,
indicating in the configuration table that the sensor unit is to be
disabled.
7. The method as recited in claim 1, wherein each of the sensor
units comprises a control unit coupled to an analog-to-digital
converter, and wherein the control unit is adapted to receive the
command and to either enable or disable the analog-to-digital
converter in response to the command.
8. The method as recited in claim 1, wherein the storing of the
data involves storing the data on a non-volatile medium.
9. A method for acquiring seismic survey data, comprising:
generating a configuration table that specifies an enabled/disabled
state for each of a plurality of spaced apart sensor units spanning
a two-dimensional area; using the configuration table to issue an
enable or disable command to each of said plurality of spaced apart
sensor units in a marine seismic streamer to provide a compressed
sensing arrangement of enabled sensor units, the command comprising
at least one binary digit indicating whether a sensor unit is to be
enabled or disabled; triggering a seismic shot; receiving data from
those sensor units that are enabled; and storing the data.
10. The method as recited in claim 9, wherein the sensor units
dissipate substantially more electrical power in the enabled state
than in the disabled state.
11. The method as recited in claim 9, wherein each of the sensor
units has a unique address, and wherein the issuing of the command
to each of the sensor units is carried out using the addresses of
the sensor units.
12. The method as recited in claim 9, wherein the generating
comprises: for each of the sensor units: producing a random number
between 0 and 1; if the random number is between 0 and a
predetermined threshold value, indicating in the configuration
table that the sensor unit is to be enabled; and if the random
number is not between 0 and the predetermined threshold value,
indicating in the configuration table that the sensor unit is to be
disabled.
13. The method as recited in claim 9, wherein each of the sensor
units comprises a control unit coupled to an analog-to-digital
converter, and wherein the control unit is adapted to receive the
command and to either enable or disable the analog-to-digital
converter in response to the command.
14. The method as recited in claim 9, wherein the storing of the
data involves storing the data on a non-volatile medium.
15. The method as recited in claim 9, wherein each of the sensor
units comprises an analog-to-digital converter, and wherein issuing
the enable or disable command to each of said plurality of spaced
apart sensor units in a marine seismic streamer comprises
activating or deactivating the analog-to-digital converter of the
sensor unit.
16. A method for acquiring seismic survey data, comprising:
generating a configuration table that specifies an enabled/disabled
state for each of a plurality of spaced apart sensor units spanning
a two-dimensional area, each sensor unit comprising an
analog-to-digital converter; using the configuration table to issue
an enable or disable command to each of said plurality of spaced
apart sensor units in a marine seismic streamer to provide a
compressed sensing arrangement of enabled sensor units, the command
comprising at least one binary digit indicating whether a sensor
unit is to be enabled or disabled; in response to the command,
activating or deactivating the analog-to-digital converter of each
sensor units in the marine seismic streamer; triggering a seismic
shot; receiving data from those sensor units that are enabled; and
storing the data on a non-volatile medium.
17. The method as recited in claim 16, wherein the sensor units
dissipate substantially more electrical power in the enabled state
than in the disabled state.
18. The method as recited in claim 16, wherein each of the sensor
units has a unique address, and wherein the issuing of the command
to each of the sensor units is carried out using the addresses of
the sensor units.
19. The method as recited in claim 16, wherein the generating
comprises: for each of the sensor units: producing a random number
between 0 and 1; if the random number is between 0 and a
predetermined threshold value, indicating in the configuration
table that the sensor unit is to be enabled; and if the random
number is not between 0 and the predetermined threshold value,
indicating in the configuration table that the sensor unit is to be
disabled.
20. The method as recited in claim 16, wherein each of the sensor
units further comprises a control unit coupled to the
analog-to-digital converter, and wherein the control unit is
adapted to receive the command and to either enable or disable the
analog-to-digital converter in response to the command.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is a divisional application of co-pending U.S. patent
application Ser. No. 12/803,503 filed Jun. 29, 2010, which is
incorporated by reference herein.
BACKGROUND
[0002] Marine seismic surveys usually employ seismic sensors below
the water's surface, e.g., in the form of long cables or
"streamers" towed behind a ship, or cables resting on the ocean
floor. A typical streamer includes multiple seismic sensors
positioned at spaced intervals along its length. Several streamers
are often positioned in parallel over a survey region.
[0003] An underwater seismic wave source, such as an air gun,
produces pressure waves that travel through the water and into the
underlying earth. When such waves encounter changes in acoustic
impedance (e.g., at boundaries or layers between strata), some of
the wave energy is reflected. The seismic sensors in the
streamer(s) detect the seismic reflections and produce output
signals. The sensor output signals are recorded, and later
interpreted to infer structure of, fluid content of, and/or
composition of rock formations in the earth's subsurface.
[0004] Traditional data acquisition has been driven by the
Shannon-Nyquist sampling theorem that, in essence, a continuous
signal cannot be reconstructed from its samples unless the sampling
rate is at least twice the signal's maximum frequency. (This
theorem applies to both time sampling and spatial sampling.)
"Compressed sensing", also called "compressive sampling", relaxes
the strictures of the Shannon-Nyquist theorem, either by
recognizing and exploiting structure in the sampled signals that
reduces their information content, or by allowing some information
loss to occur during the sampling process (i.e., "lossy" sampling).
In effect, the compressed sensing technique combines a sampling
operation with a compression operation in a manner that enables
sparse sampling, advantageously reducing the volume of acquired and
recorded sample data. A subsequent operation can be employed to
reconstruct traditional signal samples and/or the analog signals.
Such processing can be performed offline, e.g., in an environment
having more time and resources for data processing and storage.
[0005] Data acquisition using compressed sensing techniques is akin
to lossy data compression, so there is a tradeoff between a total
number of sensors employed and the quality of the resultant survey
data. For signals with low information density, like seismic
signals, this tradeoff is worthwhile. In the recent paper
"Optimized Compressed Sensing for Curvelet-based Seismic Data
Reconstruction" by Wen Tang, Jianwei Ma, and Felix J. Herrmann,
available at
http://dsp.rice.edu/sites/dsp.rice.edu/files/cs/OPCRSI3.pdf and
incorporated herein by reference in its entirety, the authors
propose an under-sampling scheme that favors sparsity-promoting
recovery. The Tang paper teaches, among other things, that seismic
survey data can be acquired using substantially fewer sensors,
albeit sensors carefully placed at predetermined locations. The
locations can be determined in a number of ways, ranging from a
random scattering to a closed-form solution derived from the
expected spatial frequency content of the signals. The Tang paper
provides a good compromise between expediency and performance using
an "optimized" random solution.
[0006] Conventional marine seismic streamers can often be 12
kilometers (km) long, and may include hundreds, or even thousands
of seismic sensors. The sheer scale of this array creates
reliability concerns which are typically addressed by building the
streamers out of similar, interchangeable streamer sections. If
there is a problem with one of the streamer sections, the
problematic streamer section is replaced by a similar streamer
section. In addition, streamer sections are much easier to handle
and store than whole streamers. The prior art fails to suggest a
streamer for compressed sampling that can adequately address such
reliability concerns.
SUMMARY
[0007] The problems outlined above are at least in part addressed
by a seismic data acquisition system with closely-spaced,
selectively enabled sensor units, and associated methods for
operating the data acquisition system. A disclosed seismic survey
system includes one or more streamer(s) and a data recording and
control system. Each of the streamer(s) includes multiple spaced
apart sensor units. Each of the sensor units is adapted to receive
a command, and to operate in an enabled state or a disabled state
dependent upon the command. The data recording and control system
issues commands to enable or disable selected sensor units,
collects data from enabled sensor units, and stores the data.
[0008] In some embodiments, the sensor units produce data when in
the enabled state, and do not produce data when in the disabled
state. The sensor units may dissipate significantly less electrical
power in the disabled state than in the enabled state. The data
recording and control system may generate a configuration table for
the sensor units that specifies an enabled/disabled condition for
each of the sensor units, and may issue the commands based on the
configuration table. The sensor units may be uniformly spaced along
the streamer. The enabled sensor units, on the other hand, need not
be uniformly spaced. The seismic survey system may include a ship
that tows the one or more streamer through a body of water.
[0009] A described sensor unit for use in a seismic sensing array
includes one or more sensor(s), an analog-to-digital converter, and
a control unit. Each of the sensor(s) is adapted to produce an
analog output signal indicative of seismic wave energy. The
analog-to-digital converter is coupled to receive the analog output
signal produced by the sensor(s), and adapted to periodically
sample the analog output signal, and to produce a digital data
output indicative of the sampled analog output signal. The control
unit is coupled to the analog-to-digital converter, and adapted to
receive a command, and to enable or disable the analog-to-digital
converter dependent upon the command. The enabling or disabling is
independent of other sensor units in the seismic sensing array. The
seismic sensing array may include one or more towed marine seismic
streamers.
[0010] The analog-to-digital converter may be disabled by stopping
a clock signal, or in response to an enable signal. The control
unit may be adapted to produce an enable signal dependent upon the
command. The analog-to-digital converter may be coupled to receive
the enable signal, and adapted to sample the analog output signal
produced by the one or more sensor and to produce the digital data
output dependent upon the enable signal. The control unit may be
adapted to provide electrical power to the analog-to-digital
converter dependent upon the command. The one or more sensor(s) may
include a hydrophone and/or a 3-axis accelerometer.
[0011] A disclosed method for acquiring seismic survey data
includes issuing an enable or disable command to each of multiple
spaced apart sensor units. A seismic shot is triggered, and data
from those sensor units that are enabled is received and stored.
The issuing of the enable or disable command may include
determining an arrangement of enabled sensor units that would
support compressed sensing, and the issued commands may create this
arrangement.
[0012] The sensor units may be arranged to span a two-dimensional
area, and may dissipate substantially more electrical power in the
enabled state than in the disabled state. The command may include
one or more binary digit(s) that specify whether a receiving sensor
unit is to be placed in the enabled state or the disabled state.
Each of the sensor units may have a unique address, and the issuing
of the command to each of the sensor units may be carried out using
the addresses of the sensor units.
[0013] The method for acquiring seismic survey data may also
include generating a configuration table for the sensor units that
specifies an enabled/disabled condition for each of the sensor
units. The method may also include using the configuration table to
issue the command to each of the sensor units. The configuration
table may be generated by determining the number of desired active
sensors and randomly selecting those sensors from the pool of
available sensors.
[0014] Each of the sensor units may include a control unit coupled
to an analog-to-digital converter. The control unit may be adapted
to receive the command, and to either enable or disable the
analog-to-digital converter in response to the command. The storing
of the data may involve storing the data on a non-volatile
medium.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] A better understanding of the various disclosed embodiments
can be obtained when the detailed description is considered in
conjunction with the following drawings, in which:
[0016] FIG. 1 is a side elevation view of an illustrative marine
seismic survey system performing a marine seismic survey, where the
marine seismic survey system includes multiple streamers;
[0017] FIG. 2 is a top plan view of the marine seismic survey
system of FIG. 1;
[0018] FIG. 3 is a diagram of an illustrative streamer section;
[0019] FIG. 4 is a diagram of an illustrative sensor unit;
[0020] FIG. 5 is a diagram of an illustrative data recording and
control system;
[0021] FIG. 6 is a diagram of an illustrative sensor array
configuration table; and
[0022] FIG. 7 is a flowchart of an illustrative method for
acquiring data.
[0023] While the invention is susceptible to various modifications
and alternative forms, specific embodiments thereof are shown by
way of example in the drawings and will herein be described in
detail. It should be understood, however, that the drawings and
detailed description thereto are not intended to limit the
invention to the particular form disclosed, but on the contrary,
the intention is to cover all modifications, equivalents and
alternatives falling within the scope of the appended claims.
DETAILED DESCRIPTION
[0024] Turning now to the figures, FIG. 1 is a side elevation view
of an illustrative marine seismic survey system 10 performing a
marine seismic survey. A survey vessel or ship 12 is moving along
the surface of a body of water 14, such as a lake or an ocean. A
data acquisition system 16 of the survey system 10 includes a data
recording and control system 18 aboard the ship 12. The data
acquisition system 16 also includes a seismic source 20 and a
sensor array 22 towed through the water 14 by the ship 12.
[0025] As described in more detail below, the sensor array 22
includes multiple spaced apart sensor units. Each sensor unit
includes one or more sensors that detect seismic signals and
produce output signals indicative of the seismic signals. The
sensor units of the sensor array 22 are selectively enabled via
commands issued by the data recording and control system 18 to
achieve an arrangement of enabled sensor units that spans a
two-dimensional area and supports compressed sensing. The data
recording and control system 18 collects and stores data from
enabled sensor units.
[0026] FIG. 2 is a top plan view of the marine seismic survey
system 10 of FIG. 1. Referring to FIGS. 1 and 2, the multiple
spaced apart sensor units of the sensor array 22 are housed in
multiple sensor cables or streamers 24A-24D. Each of the streamers
24A-24D includes multiple streamer sections 26 connected end to
end. Each of the streamer sections 26 includes multiple sensor
units. The streamers 24A-24D are towed via a harness 28 that
produces a desired arrangement of the streamers 24A-24D. The
harness 28 includes multiple interconnected cables, and a pair of
controllable paravanes 30A and 30B connected to opposite sides of
the harness 28. As the ship 12 tows the harness 28 through the
water 14, the paravanes 30A and 30B pull the sides of the harness
28 in opposite directions, transverse to a direction of travel of
the ship 12. Electrical` conductors and/or fiber optic cables
connect the sensor units in the streamer sections 26 of the
streamers 24A-24D to the data recording and control system 18
aboard the ship 12.
[0027] Referring back to FIG. 1, the seismic source 20 produces
acoustic waves 32 under the control of the data recording and
control system 18, e.g., at regular intervals or at selected
locations. The seismic source 20 may be or include, for example, an
air gun. The acoustic waves 32 travel through the water 14 and into
a subsurface 36 below a bottom surface 34. When the acoustic waves
32 encounter changes in acoustic impedance (e.g., at boundaries or
layers between strata), some of the wave energy is reflected. In
FIG. 1, ray 40 represents wave energy reflected in a particular
direction from interface 38.
[0028] As described in more detail below, enabled sensor units of
the sensor array 22, housed in the streamer sections 26 of the
streamers 24A-24D, detect these seismic reflections and produce
output signals. The output signals produced by the enabled sensor
units are recorded by the data recording and control system 18
aboard the ship 12. The recorded signals are later interpreted to
infer structure of, fluid content of, and/or composition of rock
formations in the subsurface 36.
[0029] There are often many thousands of detectors in a given
sensor array 22. A modular construction, e.g., with substantially
identical and interchangeable sections 26, greatly simplifies
handling, maintenance, and repair. However, compressed sensing
employs an irregular layout of detectors. It would be impractical
to build customized streamer sections that would need to be
assembled in a particular order and would not be interchangeable.
In the embodiment of FIGS. 1 and 2, the streamer sections 26 of the
streamers 24A-24D are substantially identical and interchangeable.
If there a problem develops with one of the streamer sections 26,
the problematic streamer section 26 can be replaced by any other
spare streamer section 26.
[0030] FIG. 3 is a diagram of an illustrative streamer section 26
from FIGS. 1 and 2. In the embodiment of FIG. 3, the streamer
section 26 includes multiple spaced apart sensor units 50, where
each of the sensor units 50 includes at least one seismic sensor as
described in more detail below. The streamer section 26 is
substantially cylindrical, and has two opposed ends 52A and 52B.
The streamer section 26 has a length L typically between 50 meters
and 100 meters. Each of the ends 52A and 52B has one or more
connectors for conveying electrical power and data signals between
sections. The sensor units 50 are spaced apart by a distance S2 in
the range between 0.3 meters and 3.0 meters. The distance from the
ends 52A, 52B to the nearest sensor unit 50 is S1, which is about
half of S2. (FIG. 3 is not drawn to scale.)
[0031] In the embodiment of FIG. 3, the sensor units 50 are
arranged in groups of N sensor units, where N is expected to be in
the range between 4 and 64, but is not limited to this range. The
sensor units 50 in each group are connected to a common group
control unit. Two such groups are shown in FIG. 3, where a first
sensor unit group is connected to a group control unit 54A, and a
second sensor unit group is connected to a group control unit 54B.
Each group control unit receives data signals from the sensor units
in the corresponding group, and produces a single output data
stream that conveys the data from that group. The group control
units may employ data compression and multiplexing techniques to
generate the output data stream from the sensor data signals.
[0032] In the embodiment of FIG. 3, a power distribution bus 56
spans the length of the streamer section 26 between the connectors
at the ends 52A and 52B, and a data bus 60 spans the length of the
streamer section 26 between the connectors at the ends 52A and 52B.
Each of the group control units (including the group control units
54A and 54B) is coupled to the data bus 60, and the data bus 60 is
used to convey the output data streams produced by the group
control units out of the streamer section 26. The data bus 60 is
also used to convey output data streams produced by other group
control units within other streamer sections connected to the end
52B. In some embodiments, the group control units employ a standard
network communications protocol to send data packets to the data
recording and control system 18.
[0033] The streamer sections 26 are often subject to wear and
damage during transport, deployment, and use. Accordingly, the
power distribution bus 56 and the data bus 60 of FIG. 3, may
include two or more buses, each capable of performing the intended
function (e.g., dual redundant buses). The multiple buses may be
located close to one another for increased convenience (at the cost
of reduced survivability), or separated from one another for
increased survivability (at the cost of reduced convenience). The
streamer sections 26 also include a jacket covering an exterior of
the streamer sections 26, and one or more strength members
extending along the length of the streamer sections 26 inside the
jacket. Suitable streamer section construction techniques are
described in U.S. Pat. No. 7,298,672 granted to Tenghamn et al.,
incorporated herein by reference in its entirety.
[0034] In conventional seismic streamers, numbers and physical
sizes of electrical and/or fiber optic cables servicing sensors,
and power supply voltage safety constraints, often limit a number
of the sensors that can be located in streamer sections. However,
in the marine seismic survey system 10 of FIGS. 1 and 2, a majority
of the sensor units 50 of the sensor array 22 are expectedly
disabled by the data recording and control system 18 to achieve a
programmable arrangement of enabled sensor units 50 that spans a
two-dimensional area and supports compressed sensing. For example,
in some arrangements of the sensor array 22, only about 25 percent
of the sensor units 50 would be enabled. This factor enables
significantly more sensor units 50 to be positioned in the streamer
sections 26 of FIG. 3 and consequently allows the spacing distances
S1 and S2 to be reduced.
[0035] FIG. 4 is a diagram of a representative sensor unit 50. In
the embodiment of FIG. 4, the sensor unit 50 includes an
analog-to-digital converter 70 coupled to a hydrophone 78, a 3-axis
accelerometer 76, and a sensor control unit 74. (Some embodiments
omit the analog-to-digital converter 70, enabling the digitization
to be performed at the group control unit.) During operation, the
analog-to-digital converter 70 receives analog output signals
produced by the hydrophone 78 and the 3-axis accelerometer 76, and
periodically samples the analog output signals to produce digital
data output signals indicative of the sampled analog output
signals. The analog-to-digital converter 70 provides the digital
data output signals to the sensor control unit 74, and the sensor
control unit communicates the data to the data recording and
control system 18.
[0036] Sensor unit 50 is adapted to receive commands from the data
recording and control system 18, and to operate in an enabled state
or a disabled state dependent upon those commands. The sensor unit
50 collects data when in the enabled state, and does not collect
data when in the disabled state. The sensor unit 50 dissipates
substantially less electrical power in the disabled state than in
the enabled state.
[0037] In the embodiment of FIG. 4, the sensor control unit 74
receives the commands, and responsively enables or disables the
analog-to-digital converter 70. For example, the analog-to-digital
converter 70 may include a clock unit 72 that governs the operation
of the analog-to-digital converter 70. When an enable signal `EN`
is asserted, the clock unit 72 runs, thereby producing an
oscillating clock signal and enabling the analog-to-digital
converter 70 to operate. When the enable signal is de-asserted, the
clock unit 72 halts, thereby holding the clock signal in stasis and
disabling operation of the analog-to-digital converter. When the
sensor control unit 74 receives an enable command, the sensor
control unit 74 may assert the enable signal EN. When, on the other
hand, the sensor control unit 74 receives a disable command, the
sensor control unit 74 may deassert the enable signal EN, thereby
effectively stopping the clock signal and disabling the
analog-to-digital converter 70.
[0038] In the embodiment of FIG. 4, the sensor control unit 74
receives electrical power (e.g., from the power bus 56 of FIG. 3)
via a line labeled `PWR,` and distributes electrical power to the
analog-to-digital converter 70, the hydrophone 78, and the 3-axis
accelerometer 76 via lines labeled `PWR.` In some embodiments, the
sensor control unit 74 is adapted to control the redistribution of
power dependent upon the commands received from the data recording
and control system 18. For example, when the sensor control unit 74
receives an enable command, the sensor control unit 74 may provide
electrical power to the analog-to-digital converter 70, the
hydrophone 78, and/or the 3-axis accelerometer 76. When, on the
other hand, the sensor control unit 74 receives a disable command,
the sensor control unit 74 can switch off the electrical power to
the analog-to-digital converter 70, the hydrophone 78, and/or the
3-axis accelerometer 76.
[0039] FIG. 5 is a diagram of one embodiment of a computer system
90 capable of carrying out some or all of the functions of the data
recording and control system 18. In the embodiment of FIG. 5, the
computer system 90 includes one or more processor(s) 92, a bridge
94, a memory 96, a bus 98, an interface unit 100, a storage device
102, and a storage medium 104. The bridge 94 is connected to the
processor(s) 92, the memory 96, and the bus 98. The bridge 94
handles communication between the processor(s) 92 and the memory
96, the interface unit 100, and the storage device 102, and between
the memory 96 and the interface unit 100 and the storage device
102.
[0040] The interface unit 100 conveys data to and from the computer
system 90, thereby enabling the processor(s) 92 to communicate
commands to various components of the sensor array 22 and to
receive data from the sensor array. The command and data signals
may be, for example, electrical signals conveying digital data, or
optical signals conveying digital data. Among the various commands
sent via the interface unit are the commands that the processor(s)
92 use to enable or disable selected sensor units 50.
[0041] The storage device 102 is adapted to send information to,
and receive information from, the information storage medium 104.
Various contemplated storage devices include a magnetic or optical
disk drive device or storage array, or a port such as a universal
serial bus (USB) port. The storage medium 104 may be, for example,
a nonvolatile memory device such as a magnetic disk, an optical
disk such as a Compact Disc Read Only Memory (CD-ROM) disk or a
Digital Versatile Disc (DVD) disk, a flash memory device such as a
USB flash drive, or a portable hard drive.
[0042] Software including processor instructions for carrying out
the functions of the data recording and control system 18 may, for
example, be retrieved from storage device 102 and temporarily
stored in the memory 96 for easy access. The processor(s) 92 may
fetch the instructions as needed from the memory 96 and execute the
instructions, thus carrying out the functions of the data recording
and control system 18. In some embodiments, the data recording and
control system 18 executes program instructions to generate a
configuration table for the sensor array 22, and to issue commands
to enable or disable selected sensor units 50 based on the
configuration table. FIG. 6 is a diagram of an illustrative
configuration table 110 that specifies an enabled/disabled
condition for each of the sensor units 50 in the sensor array 22.
The configuration table 110 (or a representation thereof) may be
stored in the memory 96.
[0043] Illustrative configuration table 110 includes a row for each
group control unit in array 22 and a column for each sensor unit in
a group. FIG. 6 shows M sensor unit groups, with N sensor units in
each group. An `ON` designation in the configuration table 110
indicates that a corresponding one of the sensor units is to be
enabled, and an `OFF` designation indicates that a corresponding
one of the sensor units is to be disabled. The data recording and
control system 18 may use the configuration table 110 to send
enable or disable commands to each of the sensor units.
[0044] In at least some embodiments, each of the sensor units 50
has a unique address, and the data recording and control system 18
issues commands that are directly addressed to the sensor units. In
other embodiments, the data recording and control system 18
addresses the commands to the group control units, providing state
information for each of the sensor units in the group. The group
control units then generate individual commands to the sensor units
to put the sensor units in the appropriate state. In either case,
the commands received by the sensor control units might include an
address field and a control field. The address field would have one
or more bits specifying an address of one of the sensor units, and
the control field would include at least one bit specifying whether
the addressed sensor unit is to be placed in the enabled state or
the disabled state.
[0045] FIG. 7 is a flowchart of an illustrative method 120 which
could be implemented by the data recording and control system 18.
During a block 122 of the method, data recording and control system
18 generates a configuration table (e.g., the configuration table
110 of FIG. 6) to specify the state of each sensor unit in the
sensor array. The system may employ any one of a variety of methods
to generate the configuration table. A random configuration can be
obtained, for example, by generating for each of the available
sensor units a random number with a uniform probability
distribution between zero and one. The random value is compared to
a threshold and those values below the threshold indicate that the
corresponding sensor unit should be disabled, while values above
the threshold indicate that the sensor unit should be enabled. The
threshold is set higher or lower to reduce or increase the relative
number of enabled sensor units. For example, setting the threshold
at 0.75 (when using a uniform distribution between 0 and 1) will
result in about 25% of the sensor units being active. In an
alternative approach, the number of desired active sensors is first
determined, and for each desired active sensor a random number is
generated to determine which of the available sensors will serve as
that active sensor. In this approach the random number R between 0
and 1 may be multiplied by the number of available sensors N, and
the result rounded up to the nearest integer to find the selected
sensor, e.g., s=round(R*N+0.5). Where it is desired to improve the
performance of the sensor array, the initial random configuration
can be evaluated and adjusted in accordance with the procedures
outlined by Wen Tang, Jianwei Ma, and Felix J. Herrmann, in
"Optimized Compressed Sensing for Curvelet-based Seismic Data
Reconstruction", which was previously referenced herein.
[0046] In block 124, the system issues commands to enable or
disable each of the sensor units in accordance with the
configuration table. In block 126, the data recording and control
system 18 receives seismic measurement data from the enabled sensor
units. As part of this receiving operation, the system may send a
trigger signal to the seismic source to fire a shot and a trigger
signal to the seismic array to initiate operation of the enabled
sensor units. In block 128 the system stores the measured data. The
recorded data can then be processed later to reconstruct the
seismic signals and perform conventional seismic inversion to
obtain information about the subsurface structure in the survey
area.
[0047] Numerous variations and modifications will become apparent
to those skilled in the art once the above disclosure is fully
appreciated. For example, if one or more defective sensor units are
detected, the system can adjust the configuration table (and with
it, the resulting arrangement of enabled sensor units) to avoid
using the defective sensor units. Such reconfiguration can, if
necessary, be performed in mid-survey. Where accelerometers are
used, particle-velocity sensors can be employed instead. It is
intended that the following claims be interpreted to embrace all
such variations and modifications.
* * * * *
References