U.S. patent application number 12/573657 was filed with the patent office on 2010-01-28 for dynamic source parameter selection for seismic vibrator data acquisition.
This patent application is currently assigned to ConocoPhillips Company. Invention is credited to Joel D. Brewer, Stephen K. Chiu, Peter M. Eick, Charles W. Emmons.
Application Number | 20100020641 12/573657 |
Document ID | / |
Family ID | 39492706 |
Filed Date | 2010-01-28 |
United States Patent
Application |
20100020641 |
Kind Code |
A1 |
Eick; Peter M. ; et
al. |
January 28, 2010 |
DYNAMIC SOURCE PARAMETER SELECTION FOR SEISMIC VIBRATOR DATA
ACQUISITION
Abstract
A method and system of operating single vibrator source points
for seismic data acquisition includes acquiring real-time field
survey locations for a first plurality of seismic vibrators,
determining at least one geometrical relationship between each of
the first plurality of seismic vibrators as a function of the field
survey locations, selecting a second plurality of seismic vibrators
from the first plurality of vibrators as a function of the at least
one geometrical relationship, selecting source parameter data for
the second plurality of seismic vibrators as a function of the
field survey locations and driving the second plurality of seismic
vibrators to propagate seismic energy into the earth. A third
plurality of vibrators is selected based on geometrical
relationships and associated source parameters are determined based
on vibrator locations. Multiple vibrator groups may acquire data
continuously without interruption.
Inventors: |
Eick; Peter M.; (Houston,
TX) ; Brewer; Joel D.; (Houston, TX) ; Chiu;
Stephen K.; (Katy, TX) ; Emmons; Charles W.;
(Houston, TX) |
Correspondence
Address: |
CONOCOPHILLIPS COMPANY - I. P. LEGAL
P.O Box 2443
Bartlesville
OK
74005
US
|
Assignee: |
ConocoPhillips Company
Houston
TX
|
Family ID: |
39492706 |
Appl. No.: |
12/573657 |
Filed: |
October 5, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11677438 |
Feb 21, 2007 |
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|
12573657 |
|
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60869318 |
Dec 8, 2006 |
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60888938 |
Feb 8, 2007 |
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Current U.S.
Class: |
367/38 |
Current CPC
Class: |
G01V 1/005 20130101 |
Class at
Publication: |
367/38 |
International
Class: |
G01V 1/00 20060101
G01V001/00 |
Claims
1-18. (canceled)
19. A set of application program interfaces embodied on a computer
readable medium for execution on a processor in conjunction with an
application program for activating a first group of seismic
vibrators comprising: a first interface that receives data for
selecting a second plurality of vibrators as a function of a
geometrical relationship associated with vibrator associated field
survey locations of the first plurality of seismic vibrators; and a
second interface that receives source parameter data for the second
plurality of vibrators as a function of the vibrator associated
field survey locations.
20. The set of application interface programs according to claim 19
further comprising: a third interface that receives instruction
data for activating the second plurality of vibrators to impart
energy into the earth.
21. The set of application interface programs according to claim 19
further comprising: a fourth interface that receives data for
selecting a third plurality of vibrators as a function of at least
one geometrical relationship; and a fifth interface that receives
source parameter data for the third plurality of vibrators as a
function of the vibrator associated field survey locations.
22. The set of application interface programs according to claim 19
further comprising: a sixth interface that receives instruction
data for activating the third plurality of vibrators.
23. The set of application interface programs according to claim 19
further comprising: a seventh interface to send data for selecting
the second plurality of seismic vibrators as a function of an
offset distance range from each other vibrator in the first
plurality of seismic vibrators.
24. The set of application interface programs according to claim 19
further comprising: an eighth interface to send data for selecting
the third plurality of seismic vibrators as a function of position
within an offset distance from each other vibrator in the first
plurality of seismic vibrators.
25. The set of application interface programs according to claim 19
further comprising: a ninth interface to provide upsweep parameter
data to the second plurality of seismic vibrators and downsweep
parameter data to the third plurality of seismic vibrators.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. patent
application Ser. No. 11/677,438 filed Feb. 21, 2007.
BACKGROUND
[0002] 1. Technical Field
[0003] The present disclosure generally relates to methods and
processing in the field of seismic data acquisition, and
particularly to the acquisition and processing of seismic data.
[0004] 2. Background Information
[0005] Seismic surveys image or map the subsurface of the earth by
imparting acoustic energy into the ground and recording the
reflected energy or "echoes" that return from the rock layers
below. The source of the acoustic energy is usually generated by an
explosion or seismic vibrators, or air guns (and marine vibrators)
in marine environments.
[0006] During a seismic survey, the energy source is positioned on
or near the surface of the earth. Each time the energy source is
activated it generates a seismic signal that travels into the
earth, is partially reflected, and, upon its return, may be
recorded at many locations on the surface as a function of travel
time.
[0007] The sensors that are used to detect the returning seismic
energy usually take the form of sensors like geophones or
accelerometers (land surveys) and hydrophones (marine surveys). The
returning seismic energy is acquired from a continuous signal
representing displacement, velocity or acceleration that may be
represented as an amplitude variation as a function of time.
[0008] Multiple source activation/recording combinations are
subsequently combined to create a near continuous image of the
subsurface. A survey produces a data volume that is an acoustic
image of the subsurface that lies beneath the survey area.
[0009] A seismic vibrator generally takes the form of a truck or
other vehicle that has a base plate that can be brought into
contact with the earth. A reaction mass in association with a
baseplate is driven by a system to produce vibratory motion which
travels downward into the earth via the base plate. A similar
system of actuating devices operates in the marine vibrator. A
survey may be designed that uses multiple vibrators, each being
activated simultaneously so that the recording instruments capture
a composite signal with contributions from all of vibrators. The
composite signal forms a separable source vibrator record that
allows for source separation through data inversion.
[0010] One vibratory seismic data acquisition method for acquiring
separable source vibrator records is known as high fidelity
vibratory seismic. In this method, multiple seismic vibrators are
operated simultaneously, thereby creating a complex source signal
wherein separate source signals from separate vibrators or groups
may be separated during subsequent processing.
[0011] In separable sweep applications the contributions of each
individual vibrator from the recorded composite signal in a
multi-vibrator survey may be separated. The sweep signals of each
vibrator are varied in such a way as to make later separation
feasible. This may involve the use of phase encoding of a constant
phase shift to each vibrator's signal relative to another vibrator
sweep in the group. When using multiple sweeps of the vibrators, a
different phase encoding scheme may be employed for each sweep.
[0012] The fidelity of the source separation depends to a large
degree on the selection of an appropriate vibrator sweep
parameters, a good scheme being one that leads to better (meaning
higher signal to noise) source separation. Better source
separation, in turn, will result in an improved data quality.
[0013] The description of the invention which follows, together
with the accompanying drawings, should not be construed as limiting
the invention to the examples or embodiments shown and described.
This is so because those skilled in the art to which the invention
pertains will be able to devise other forms of this invention
within the ambit of the appended claims.
SUMMARY
[0014] The following presents a general summary of some of the many
possible embodiments of this disclosure in order to provide a basic
understanding of this disclosure. This summary is not an extensive
overview of all embodiments of this disclosure. This summary is not
intended to identify key or critical elements of the disclosure or
to delineate or otherwise limit the scope of the claims. The
following summary presents some concepts of the disclosure in a
general form as a prelude to the more detailed description that
follows.
[0015] In one embodiment for separable source seismic vibrators,
operating a first group of seismic vibrators (substantially all the
vibrators operating on a survey) includes selecting a second group
of seismic vibrators from the first group of seismic vibrators in a
field survey area as a function of geometrical relationships
between the vibrators. The second group is activated to propagate
seismic energy into the earth. A third group of vibrators may be
selected from the first group. The third group of vibrators is
activated to propagate seismic energy into the earth. There may be
no time delays between the end of sweeping from one group (like the
second group) and initiation of activation in a subsequent group
(like the third group) or they may be activated contemporaneously
and sweeps from separate groups may be overlapping in time.
[0016] In another embodiment a method of operating a first
plurality of seismic vibrators having at least one geometrical
relationship between each of the vibrators as a function of
real-time survey locations includes selecting a second plurality of
seismic vibrators as a function of the first plurality geometry.
Source parameter data are selected for the second plurality of
seismic vibrators and the second plurality of seismic vibrators are
activated to propagate seismic energy into the earth.
[0017] The source parameter data may be provided to each of the
second plurality of seismic vibrators immediately prior to each
sweep, since conditions may be change dynamically during
acquisition. A sweep parameter look-up table may be prepositioned
within each vibrator to facilitate parameter distribution.
Geometrical relationships between each of the first plurality of
seismic vibrators as a function of the field survey locations
include a distance between each of the first plurality of seismic
vibrators and an angle between one of the first plurality of
seismic vibrators and two other of the first plurality of seismic
vibrators. The geometrical relationship function for selecting the
second plurality of seismic vibrators may be a minimum preselected
distance between each of the first plurality of seismic vibrators,
a maximum preselected distance between each of the first plurality
of seismic vibrators, a weighted distance between each of the first
plurality of seismic vibrators or an angle between one of the first
plurality of seismic vibrators and two other of the first plurality
of seismic vibrators. Source parameter data may be selected as a
function of the number of vibrators or a ground surface condition
associated with at least one of the field survey locations. Source
parameter determination may include equalizing the energy
propagated at field survey locations associated with the first
plurality of seismic vibrators.
[0018] In another aspect, the method may include recording, at a
field sensor, at least one signal responsive to the second
plurality of seismic vibrators and recording a propagation signal
associated with each seismic vibrator of the second plurality of
seismic vibrators to obtain a plurality of vibrator propagation
signals and then processing the data with the plurality of vibrator
propagation signals.
[0019] A third plurality of seismic vibrators may be selected as a
function of the geometrical relationships between each of the first
plurality of seismic vibrators and source parameter data determined
as a function of the location of at least one vibrator in the third
plurality of seismic vibrators. The third plurality of seismic
vibrators is then activated to propagate energy into the earth. The
second and third pluralities of seismic vibrators may utilize
upsweeps and downsweeps.
[0020] Source parameter data for the seismic vibrators include: a
sweep duration; a total time for all sweeps; a sweep start time; a
sweep stop time; a sweep start frequency; a sweep stop frequency; a
sweep as a function of amplitude and time; a sweep phase encoding;
a vibrator hold down force; a number of sweep segments; pre and
post sweep tapers and duration; and a sweep listen time between
sweeps.
[0021] In another embodiment a control unit for a seismic data
acquisition system in data communication with a first plurality of
seismic vibrators includes a processor associated with memory and
an application program associated with the processor for execution.
The application program includes instructions to select a second
plurality of seismic vibrators as a function of a geometrical
relationship associated with each field survey location of the
first plurality of seismic vibrators, instructions to determine
source parameter data as a function of the location of at least one
vibrator in the second plurality of seismic vibrators and
instructions to activate the second plurality of seismic vibrators
to propagate energy into the earth.
[0022] The application program may also include instructions to
select a third plurality of seismic vibrators as a function of at
least one geometrical relationship between each of the first
plurality of seismic vibrators, instructions to determine source
parameter data as a function of the field survey location of at
least one vibrator in the third plurality of seismic vibrators and
instructions to activate the third plurality of seismic vibrators
to propagate energy into the earth.
[0023] The control unit may include a plurality of sensors for
detecting a seismic event, each sensor having an output indicative
of the seismic event. The determined geometrical relationship
associated with each location of the first plurality of seismic
vibrators may include a distance between each of the first
plurality of seismic vibrators or an angle between one of the first
plurality of seismic vibrators and at least two other of the first
plurality of seismic vibrators.
[0024] The function of the geometrical relationship associated with
each location of the first plurality of seismic vibrators for
selecting the second plurality of seismic vibrators may include a
minimum preselected distance between each of the first plurality of
seismic vibrators, a maximum preselected distance between each of
the first plurality of seismic vibrators, a weighted distance
between each of the first plurality of seismic vibrators or an
angle between one of the first plurality of seismic vibrators and
two other of the first plurality of seismic vibrators. The source
parameter data may be selected as a function of the number of
vibrators or a ground surface condition associated with at least
one of the field survey locations.
[0025] The application program may include instructions to
substantially equalize the energy propagated at field survey
locations according a preselected source acquisition effort. The
application program may include instructions to provide upsweep
data to the second plurality of seismic vibrators and downsweep
data to the third plurality of seismic vibrators.
[0026] In yet another embodiment a set of application program
interfaces are embodied on a computer readable medium for execution
on a processor in conjunction with an application program for
activating a first group of seismic vibrators including a first
interface that receives data for selecting a second plurality of
vibrators as a function of a geometrical relationship associated
with vibrator associated field survey locations of the first
plurality of seismic vibrators and a second interface that receives
source parameter data for the second plurality of vibrators as a
function of the vibrator associated field survey locations.
[0027] In another aspect the set of application interface programs
include a third interface that receives instruction data for
activating the second plurality of vibrators to impart energy into
the earth. A fourth interface may receive data for selecting a
third plurality of vibrators as a function of at least one
geometrical relationship and a fifth interface that receives source
parameter data for the third plurality of vibrators as a function
of the vibrator associated field survey locations. A sixth
interface may receive instruction data for activating the third
plurality of vibrators. A seventh interface may send data for
selecting the second plurality of seismic vibrators as a function
of an offset distance range from each other vibrator in the first
plurality of seismic vibrators. An eighth interface may send data
for selecting the third plurality of seismic vibrators as a
function of position within an offset distance from each other
vibrator in the first plurality of seismic vibrators. A ninth
interface may provide upsweep parameter data to the second
plurality of seismic vibrators and downsweep parameter data to the
third plurality of seismic vibrators.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The following drawings illustrate some of the many possible
embodiments of this disclosure in order to provide a basic
understanding of this disclosure. These drawings do not provide an
extensive overview of all embodiments of this disclosure. These
drawings are not intended to identify key or critical elements of
the disclosure or to delineate or otherwise limit the scope of the
claims. The following drawings merely present some concepts of the
disclosure in a general form. Thus, for a detailed understanding of
this disclosure, reference should be made to the following detailed
description, taken in conjunction with the accompanying drawings,
in which like elements have been given like numerals.
[0029] FIG. 1 is a flow chart of embodiment for continuous data
acquisition.
[0030] FIG. 2 is a schematic representation of a vibrator relative
to a selected minimum and a relative maximum offset distance within
to operate in relation to other vibrators.
[0031] FIG. 3 is a schematic representation a vibrator relative to
other vibrators for an example seismic field survey layout.
[0032] FIG. 4 is a flow chart illustrating a non-limiting
embodiment of acquiring data with source parameter data selected as
a function of a field location parameter.
[0033] FIG. 5 is a flow chart illustrating a non-limiting
embodiment of acquiring data with source parameter data selected
for a subset of the vibrators operating in a survey area, the
source parameter data selected as a function a field survey
condition.
[0034] FIG. 6 is a flow chart illustrating a non-limiting
embodiment of acquiring data with groups of the vibrators on a
field survey wherein the groups may be composed of different
numbers of vibrators.
[0035] FIG. 7 is a flow chart illustrating a non-limiting
embodiment wherein groups of vibrators are selected as a function
of geometrical relationships.
[0036] FIG. 8 is a flow chart illustrating a non-limiting
embodiment of continuous data acquisition for groups of
vibrators.
[0037] FIG. 9 illustrates a system for seismic data acquisition and
a seismic data processing system or main control within which a set
of instructions may enable the system to perform any of the
nonlimiting embodiments or their equivalents disclosed herein.
DETAILED DESCRIPTION
[0038] A non-limiting illustrative embodiment of system and method
for selecting vibrator units and their associated source parameter
data is presented through one or more of its various aspects such
as those noted below. Particular non-limiting embodiments for
selecting contemporaneously operating separable single vibrator
source points and related seismic vibrator-source acquisition
parameters are described. Embodiments disclosed herein and
equivalents that will be apparent to practitioners in the art
provide for robustly increasing the efficiency of acquiring high
quality seismic data.
[0039] The system and methods encompass various non-limiting
aspects of operating single vibrators sources including continuous
and uninterrupted data recording, optimized and variable sweep
encoding parameters, dynamic sweep encoding parameter selections
based on available field resources and field location conditions,
maintaining a substantially uniform source energy budget for all
source points, dynamic selection of vibrator units for an
acquisition effort based on available real-time field resources and
real-time resource management to maximize acquisition efficiency.
This `real-time` capability assures that vibrator field survey
positioning is known within a preselected accuracy, for example
position interrogation or reporting may take place from every few
seconds up to several minutes. The real-time management function
ensures that relevant data are being constantly or nearly
constantly acquired as long as acquisition resources are present in
the field.
[0040] The normal term for a sweep time applied per source point is
"pad time." Pad time refers to the total number of seconds spent
sweeping. The time subsequent to the time spent sweeping is termed
the listen time. A vibrator source seismic acquisition crew with
zero down time cannot achieve more production in a work period than
the total of the pad time plus the listen time.
[0041] Foregoing all or substantially all of the post-sweep listen
time (i.e. a `zero` listen time) reduces the overall acquisition
effort time. Alternatively, increasing the sweep time increases the
energy imparted into the earth and therefore the potential signals
returned to the recording sensors. Separable sweep seismic vibrator
acquisition methods require a stable matrix to enable a successful
inversion, so at least as many sweeps as active vibrators involved
in the setup are necessary. A listen time is not a fundamental
requirement for separable sweep vibrator methods.
[0042] A minimal or no listen time increases the effective pad time
for the vibes putting source energy in the ground. This may improve
the data quality by increasing the effective sweep time per source
point and per productive work period. Depending upon the vibrator
and the electronics a minimal listen time of a few tens or hundreds
of milliseconds may be necessary for the vibrator to reset and
start the next sweep. Reset times for various vibrators and
electronic control systems vary. Continuous recording of seismic
data acquisition reduces the costs of survey acquisition while
improving the overall data quality. The signal to noise ratio for
acquired data is improved by minimizing the listen time and
increasing the effective amount of source energy per source point
by increasing the source effort or in effect increasing pad
time.
[0043] For continuous and uninterrupted source output, seismic data
recording systems may be operable so that recordings are made
continuously over time without any interruption. Seismic recordings
may be day-long records or even longer. There are several known
methods to correlate timing between source event times and the data
recordings.
[0044] FIG. 1 illustrates an embodiment for continuously recording
seismic data from first group of seismic vibrators 101 in a field
survey area. The embodiment, which may include one or more of the
following (in any order), includes selecting a second group of
seismic vibrators 103 from the first group of seismic vibrators in
a field survey area. The second group is activated 105 to propagate
seismic energy into the earth. A third group of vibrators is
selected 107 contemporaneously with the second groups' energy
propagation or immediately upon termination of the second group
sweeping. The third group of vibrators is activated 109 to
propagate seismic energy into the earth. There is no requirement
for time delays between the end of sweeping from one group (like
the second group) and initiation of activation in a subsequent
group (like the third group) and the third group sweeps may be
initially activated at any time during the time the second group is
sweeping. With well determined separable source parameter data,
single source vibrators and vibrator groups may begin and end
sweeping arbitrarily with overlapping sweeps.
[0045] Methods for acquiring seismic data from multiple vibrators
using contemporaneous and separable sweeps commonly disclose the
use of four vibrators with four sweeps per setup, with vibrators
located as a group with each vibrator a few meters to tens of
meters from other vibrators and generally using common sweep
frequencies. The sweeps usually differ only due to phase rotations,
and otherwise the sweeps have the same parameters.
[0046] However, for separable sweep operations, no set numbers of
vibrators, specific frequency ranges or specific phase separations
are required. Using single vibrators spaced well apart, in contrast
to previous practice, aids signal separation. Sweep frequency
parameters and other source related variables may be different
between vibrator sweeps to further optimize sweep separation.
Vibrator source parameter data may be unique to each vibrator and
do not have to be common for any of the total group of
contemporaneously operating vibrators. Up-sweeps and down-sweeps
and other variations with non-linear sweep parameters can be used
to improve the conditioning of the inversion matrix to improve
signal separation and increase the number of vibrator operating
contemporaneously.
[0047] In a nonlimiting example, upsweep and downsweep data may be
acquired with contemporaneously operating individual vibrator
source stations. One group of three, four or five individual
vibrators may be engaged for acquiring separable upsweep data while
another group of three, four or five individual vibrators are also
engaged in acquiring separable downsweep data records. This enables
contemporaneous data acquisition from six to ten source stations.
Of course, the number of source stations operating at any time may
be dependent on equipment field position.
[0048] When using single vibrators as individual source stations it
is beneficial to determine the range of distances from other
contemporaneously operated vibrators to optimize source
effectiveness. If two vibrators are operated too close together,
the vibrators will interfere with sensors on or near the
vibrator(s) such that source signal separation is less than would
be optimal with a larger spatial separation. At the same time,
there are also distances for vibrators such that a separation
between vibrators is so great that energy from vibrators interferes
by overwhelming any reflection received at the sensors near
vibrators at long distances from the vibrator representing the
source signal to be inverted.
[0049] As schematically illustrated in map view in FIG. 2, for a
vibrator A represented by a cross-symbol, a near source minimum
range of offset m is shown. For comparison, a maximum range M is
shown. The area that is greater than m and less than M is the area
relative to vibrator A within which other vibrators may optimally
be operated so as to not overwhelm sensors in proximity to the
vibrators. These distances m and M may be locally variable for
different areas, even within survey areas. Adjustments or
trade-offs may be made for different areas and different levels of
interference that may be considered acceptable.
[0050] A schematic layout for 10 vibrators is illustrated in map
view in FIG. 3 for vibrators A through J. The minimum selected
distances for each vibrator are illustrated. Vibrators A through F
(shown as the filled-in cross symbols to represent availability
under the selection parameters) are in position such that any
groups of from 1 to 6 of them may be chosen as a potential setup
for acquisition. Vibrators I and J are too far away from vibrators
G and H, and vice versa, to be used if the restrictions for not
using vibrators separated by more than a distance equivalent to M
are going to be used in this case. However, A through F are not
further than a distance equivalent to M from any of the other
vibrators A through J.
[0051] A further optimization of the set of vibrators in FIG. 3 may
be affected when using multiple groups, for example when groups of
three vibrators per setup have nominally been chosen. Vibrators A,
B and C may be selected as one group and vibrators D, E and F may
be chosen as another group. However, these two groups may provide a
linear footprint to the shot selection. This footprint may be
avoided by selecting A, B and D as one group and C, E and F as
another group, and so may provide for a better set of
recordings.
[0052] Computer simulations may be used to test sweep parameters to
determine an optimal set of parameters to provide effective source
separation between the vibrators used for any particular setup.
These computer simulations may be determined prior to an
acquisition effort. Additionally, simulations may also be performed
using acquisition parameters as found during the field effort. The
parameters may be tailored to the number of vibrators used, the
number of sweeps and even the environmental conditions in the
vicinity of one or more vibrators to be operated contemporaneously,
such as the ground surface conditions and the group vibrator
separations or offsets. When one or more vibrators sweep on soft
soil it may be beneficial to add a sweep to the nominal number
used. For example, if five sweeps were nominally used for a survey
area, six sweeps may be used which adds some redundancy to any
inversion as well as `conditioning` the surface which may be
beneficial for energy propagation. Additionally, shaped source
wavelets for a selected source point may be acquired by having more
than one vibrator occupy the same source point during repeated
setups, for example with a different bandwidth of sweep or
concatenated sweeps.
[0053] Using a common set of sweep frequencies, sweep types and
relative phase rotations in each seismic vibrator of a group of
vibrators may not yield an optimal set of sweep parameters. Any
sweep parameter variables may be optimized for sweep separation,
not just the relative phase rotations used for sweep phase
encoding. These variable sweep parameters may be determined and
provided for input to vibrator controllers any time including
immediately prior to a group of vibrators finalizing their setup.
To provide an optimal set of sweep parameters for a group of
vibrators, one or more of a group of contemporaneously operating
vibrators may use a set of sweeps or concatenated sweeps that is
unique from any of the other vibrators for that setup.
[0054] FIG. 4 illustrates an embodiment of a method, which may
include one or more of the following (in any order), for operating
a plurality of seismic vibrators 401 includes acquiring real-time
field survey locations 403 for a group of seismic vibrators and
determining at least one associated field location parameter 405.
Source parameter data for each of the plurality of seismic
vibrators is selected 407 as a function of the number of vibrators
in the plurality of vibrators and any associated field location
parameter at any of the vibrators (such as a specific ground
surface conditions that may effect sweep parameters). The selected
source parameter data are communicated 409 to the plurality of
vibrators and the vibrators are activated 411 to propagate seismic
energy into the earth.
[0055] In another aspect the associated field location parameter
that may affect a source parameter can include a weight of any of
the seismic vibrators or a ground force parameter used to drive any
seismic vibrators. Source parameter data communicated to the
vibrators include, but are not limited to a sweep duration, sweep
start and stop times, sweep start and stop frequencies, dwell time
and type, pre and post tapers and rates, phase encoding, hold down
force, up/down sweeps, and number of sweeps. These source
parameters may be adjusted to substantially equalize the energy
imparted for source point locations across the survey using any
known process for estimating signal propagation.
[0056] Acquisition also includes recording at a field sensor
signals responsive to the seismic vibrators, recording a
propagation signal associated with each seismic vibrator to obtain
a plurality of vibrator propagation signals (e.g, the ground force
signal or other signal to compute a designature operator), and
processing or inverting the responsive signals with the designature
operator to obtain seismic records for further processing. An
example of designature is a deconvolution to remove a measured or
modeled wavelet, i.e., to estimate what would have resulted from an
impulsive source with a broad bandwidth or a measured bandwidth of
a vibrator source. Designature and deconvolution methods are well
known by practitioners of seismic processing methods.
[0057] FIG. 5 illustrates an embodiment, which may include one or
more of the following (in any order), for operating a first group
501 of seismic vibrators, which may be all the vibrators operating
in a survey area, that includes determining real-time field survey
locations 503 of the vibrators and selecting a second group of
vibrators 505 from the first group based on relative distances
between any of the first group of seismic vibrators. Source
parameter data is determined 507 as a function of the second group
of vibrators and field survey conditions associated with the field
survey locations in vicinity of the selected vibrators. The source
parameter data are sent 509 to the second group of seismic
vibrators and the vibrators are activated 511 to propagate seismic
energy into the earth.
[0058] The field survey condition may be the number of seismic
vibrators in the second group, a weight of any of the second group
of seismic vibrators, a ground surface condition at the field
survey location or the ground force signal used to activate any the
of seismic vibrators. A third group of seismic vibrators selected
after activation of the second group of seismic vibrators may be
activated, except possibly for equipment reset requirements.
[0059] Offset parameters that may affect whether to include
vibrators in any group for a particular setup include selecting a
seismic vibrator that is positioned greater than a preselected
inter-group minimum distance from any other vibrator (e.g. m in
FIG. 3), selecting a seismic vibrator that is positioned less than
a preselected inter-group maximum distance from any other vibrators
(e.g., M in FIG. 3) or selecting a seismic vibrator that is
positioned within a preselected intra-survey maximum distance of
any other of the first plurality of seismic vibrators.
Alternatively, the distances may be given a weighting such that an
optimized group is selected, and a group may include some vibrator
pairs that would not otherwise be chosen except for maximizing
recording acquisition in areas where adequate coverage has not been
obtained.
[0060] Source parameter data used in separable sweep
vibrator-source recordings may involve loading a fixed parameter
set of phase encodings into a lookup table for a vibrator sweep
encoder. The vibrator sweep encoder then cycles through the fixed
number of phase encodings for each setup. Upon completion of the
setup, the vibe moves to the next source point and is or has been
reset to the first lookup position. These parameters are often
loaded prior to a survey field effort and do not change during the
acquisition program. This type of program is therefore fairly rigid
and prone to inefficiencies and down time when any components, such
a single vibrator unit, are not operational at all times.
[0061] Fixed numbers of sweeps and unchanging parameters may not
provide an optimal set of sweeps for a group of contemporaneously
operating seismic vibrators. A group of seismic vibrators may lose
a member due to mechanical fault that puts the entire group on
standby until replaced or repaired.
[0062] An optimal set of sweeps for multiple single-vibrator
station data acquisition may depend on environmental conditions in
the field and the available resources, like the number of vibrators
available for recording at any particular time. One requirement for
inverting separable vibrator-source sweep records is a stable
matrix that contains at least as many sweeps as active vibrators
involved in the acquisition setup. Different phase encoding
parameters and other sweep parameters may provide for more optimal
separable records than may be known prior to the field effort. If a
vibrator in a group is unable to perform, the optimal sweep
parameters may be reset or else the acquisition may be put on on
standby. Additionally, sweep parameters may be further adjusted so
that processing, interpretation and analysis of seismic data may be
made significantly easier by providing a uniform amount of energy
be applied to each source point.
[0063] Prior art field operations often involve waiting for a set
of vibrators to get into position prior to starting acquisition at
the next setup. During this downtime data are not being acquired.
This downtime may be minimized by the use of more than one set or
group of seismic vibrators, but there may still be a significant
portion of the workday that the recording crew is waiting for vibes
to get into position. Positioning one or more sets of vibrators so
that as soon as a first group ends an acquisition effort a
subsequent group of vibrators may immediately initiate data
acquisition provides that data are acquired at all times equipment
is in the field.
[0064] Dynamically adjusting the number of active vibrators along
with their other source parameter data via parameters transmitted
in real-time during an acquisition effort provides for an optimal
acquisition scheme without having to wait for a preset or
preselected group. This may be especially important when various
vibrator equipment is not operating at peak efficiency or one
preselected group of vibrators does not have a full or nominal
complement. With compensating parameter selection that may be
provided in real time, the field effort does not need to incur any
standby time.
[0065] For example, when one group seismic of vibrators is being
used in a field effort, another group of vibrators may be preparing
for a subsequent effort associated with acquisition source points
and this preparation may include receiving source parameter data
from a central location. Alternatively, source parameter data may
complement or modify a lookup table of selectable phase encodings,
ground force settings and other source parameters for different
numbers of seismic vibrators, which may be loaded into and/or
resident with the vibrator sweep controller. A central or control
location may provide for dynamically determining the vibrator sweep
controller parameters depending upon the number of vibes involved
in the setup and environmental conditions in the vicinity of the
group chosen to next acquire data records. An optimal number of
sweeps and associated parameters is thereby selected and provided
in real-time to maintain uniform source point energy for an optimal
data quality as well as continuous and uninterrupted source energy
propagation.
[0066] If a survey operator has selected that a desired nominal
amount of energy is required per source point, the number of sweeps
and/or sweep lengths with associated phase encodings may be
supplied to a selected group of seismic vibrators to help ensure
the effort is undertaken. These parameters may change based on
available vibrators and other environmental conditions. The energy
propagated into the earth to maintain a uniform source effort for
each source point is dynamically adjusted depending on the
available selected number of vibrators along with a selected phase
encoding to be provided to the vibrator controllers that represents
an optimum for the vibrators involved.
[0067] The number of vibrators to be used is dynamically adjusted
and an optimal set of phase encodings or other parameters for those
vibrators may be provided nearly instantaneously, which may be
important during an equipment failure. On a source-point by
source-point basis the number of sweeps and length of the sweeps
are adjusted to maintain the uniform energy.
[0068] FIG. 6 illustrates an embodiment, which may include one or
more of the following (in any order), for operating a first group
of seismic vibrators 601 (substantially all the vibrators operating
on a survey) located at field survey locations includes selecting a
second group of vibrators 603 and a third group of vibrators 605
from the first group of seismic vibrators. The second and third
groups contain different numbers of seismic vibrators. Source
parameter data is determined 607 as function of a preselected
nominal field acquisition effort. For example, a survey may be
planned such that nominal source efforts will be comprised of five
vibrators that sweep five times. This second group of vibrators is
then activated 609 to propagate seismic energy into the earth.
Source parameter data to be provided to the third group is selected
611 to substantially equalize the energy propagated at these third
group field survey locations commensurate with the energy
propagated at locations for the second plurality of seismic
vibrators.
[0069] In another aspect source parameter data may be further
selected as a function of surface conditions associated with the
field survey locations of the first plurality of seismic vibrators.
In still another aspect, the third group of seismic vibrators is
activated to propagate seismic energy into the earth. The
preselected source acquisition effort nominally includes
substantially equalizing the amount of vibrational energy imparted
at all field survey locations associated with the first plurality
of seismic vibrators. The vibrators in the second and third groups
may be selected as a function of the vibrators' respective field
survey locations. Selecting the second and third groups of
vibrators from the first group of vibrators is based on the
distances between locations of the vibrators.
[0070] For seismic vibrators used in separable sweep
vibrator-source seismic data acquisition surveys, the vibrators not
related to the active source point may appear as noise sources that
contaminate the acquired data during the setup. There may be some
leakage of noise between the different vibrators involved in a
setup even with an optimal phase encoding.
[0071] Seismic acquisition designs for 3D-surveys have a natural
tendency to include an increased number of traces in the mid and
far offsets from the sources due to the increasing distance from
the source when compared to the near offset. Thus near offsets may
need to be protected from noise contamination. Testing in the field
and computer simulations indicate that in separable sweep
vibrator-source data acquisition operations, at far offsets (or as
offsets increase from an active source) the noise of the vibrators
involved in the setup eventually overpower the signal being
recorded by the geophones or sensors at the surface. Therefore, if
the vibrators are close to the receiver point they may contaminate
the near source sensors and if very far apart they tend to
overpower the geologic signals in the far offset sensors. For a
particular field survey area or portion of a survey area, the
vibrators involved in any particular set up may advantageously be
selected to be within a range of offsets from each other vibrator
in the group's setup.
[0072] In one embodiment a queue of available vibrators associated
with a seismic data acquisition survey may be stored in computer
memory in real time. A software or hardware-software combination
then dynamically selects the best constellation or areal
arrangement of an arbitrary number of vibes to minimize the cross
contamination of noise between records. The constellation group
locations (i.e., distributed source array or setup) may be highly
variable (not linearly positioned relative to other vibrators) to
minimize the amplitude variation with azimuth impact and footprint
issues and allows optimization of the final data quality by
distributing the cross contamination noise for shot records in a
benign manner.
[0073] FIG. 7 illustrates an embodiment, which may include one or
more of the following (in any order), for operating seismic
vibrators 701 includes acquiring real-time field survey locations
703 for a first group of seismic vibrators operating in a survey
area. At least one geometrical relationship 705 between each of the
first group of seismic vibrators is determined as a function of the
field survey locations. From the first group, a second group of
vibrators is selected 707 as a function of at least one geometrical
relationship. Source parameter data is then selected 709 as a
function of the field survey locations. The vibrators are then
activated 711 to propagate energy into the earth. The data are then
recorded for further processing.
[0074] The geometrical relationships between each of the first
group of seismic vibrators as a function of the field survey
locations includes a distance between each of the first plurality
of seismic vibrators and may also include an angle between one of
the first plurality of seismic vibrators and at least two other of
the first plurality of seismic vibrators. The function of the at
least one geometrical relationship for selecting the second
plurality of seismic vibrators may be a minimum preselected
distance between each of the first plurality of seismic vibrators,
a maximum preselected distance between each of the first plurality
of seismic vibrators, a weighted distance between each of the first
plurality of seismic vibrators or an angle between one of the first
plurality of seismic vibrators and at least two other of the first
plurality of seismic vibrators. Further, the function of the field
survey locations for selecting source parameter data may be the
number of vibrators selected or a ground surface condition
associated with at least one of the field survey locations.
Selecting source parameter data may be selected to substantially
equalize the energy propagated at field survey locations associated
with all of seismic vibrators source acquisition effort.
[0075] FIG. 8 illustrates another embodiment, which may include one
or more of the following (in any order), for operating seismic
vibrators 801 that includes determining field survey locations 803
for a first group of seismic vibrators operating in a survey area.
A second group of vibrators 805 and a third group of vibrators 807
may be selected from the first group as a function of the field
survey location parameters. For example the distances separating
the vibrators and the distances each group is from another group
are factors affecting selections. These distance parameters may
change over a survey area. Source parameter data for the second
group and third group is selected 809 as a function of each
vibrator field survey location parameters. The second group of
vibrators is activated 811 to propagate seismic energy into the
earth and the third group of vibrators may be activated 813 to
propagate seismic energy substantially when the second plurality of
seismic vibrators ceases to propagate energy into the earth, so
that vibrators are continuously sweeping without interruption.
Alternatively, the third group of vibrators may sweep at any
arbitrary time during activation of the second group of vibrators
so that the acquisition from the second and third groups overlap in
time. When there is no listen time between sweeps, multiple groups
of vibrators may be sweeping continuously without interruption.
[0076] Acquisition using multiple groups continuously recording
includes recording signals at field sensors responsive to the
seismic vibrators, recording a propagation signal associated with
each seismic vibrator to obtain a plurality of vibrator propagation
signals (e.g, the ground force signal or other signal to compute a
designature operator), and processing or inverting the responsive
signals with the designature operator to obtain separated seismic
records for further processing.
[0077] The fidelity of the separable sweep vibrator-source seismic
data acquisition technology depends on the design of a vibrator
phase encoding scheme and related sweep parameters, the location of
the vibrators in space, a robust inversion algorithm and the method
of field operations. This technology requires multiple vibrators to
sweep simultaneously to generate a multi-vibrator gather. Within a
vibrator array, each vibrator has a unique sweep. This process is
repeated for a certain or predetermined multiple number of sweeps
at the same source locations.
[0078] The efficiency of acquisition may be optimized by providing
a method of determining the selection (of the location) of the
available vibes, number of sweeps and best sweep scheme for the
subset of vibes. The method is comprised of using a subset of the
available vibes that minimizes the cross contamination of noise
from the different vibes onto the inverted shot records.
[0079] FIG. 9 illustrates a seismic data acquisition system and
that may include a control unit 10 for the acquisition system. The
control unit 10 includes one or more of the components illustrated.
and described herein. The seismic data acquisition system includes
a first group of seismic vibrators (e.g., the vibrators deployed
for a seismic survey illustrates as A through J, similar to FIG.
3), optionally a plurality of sensors 901 for detecting and
recording a seismic event, each sensor having an output indicative
of the seismic event.
[0080] The system includes a main control unit 10, which may be
included as part of the seismic data processing system and in data
communication with the first group of seismic vibrators and
optionally with a plurality of sensors. Sensors recording,
including sensors providing real-time position data are not
required as part of the system, though timing between sources and
receivers may need to be very accurately determined for the
vibrators. The location of the main control unit 10 may be anywhere
relative to the physical layout of the seismic survey equipment
(vibrators and sensors), and may be located at a remote site.
[0081] A computer program (one or a combination of 13, 15, 21, 27
and 29) associated with the main control unit 10 includes
instructions for execution. These include instructions to determine
a geometrical relationship associated with each field survey
location of the first group of seismic vibrators, instructions to
select a second group of seismic vibrators as a function of the
geometrical relationship associated with each location of the first
group of seismic vibrators, instructions to determine source
parameter data as a function of the field survey location of at
least one vibrator in the second group of seismic vibrators and
instructions to activate the second group of seismic vibrators to
propagate energy into the earth.
[0082] The computer program may also include instructions to select
a third group of seismic vibrators as a function of the geometrical
relationships between each of the first group of seismic vibrators,
instructions to determine source parameter data to communicate to
each vibrator in the third group of seismic vibrators as a function
of the location of at least one vibrator in the third group of
seismic vibrators, and instructions to activate the third group of
seismic vibrators to propagate energy into the earth. The program
may also include instructions to activate the third group of
seismic vibrators to propagate energy into the earth.
[0083] The determined geometrical relationship associated with each
location of the first group of seismic vibrators may be a distance
between each of the first group of seismic vibrators or an angle
between one of the first group of seismic vibrators and at least
two other of the first group of seismic vibrators. The geometrical
relationship associated with each location of the first group of
seismic vibrators for selecting the second group of seismic
vibrators may be one of a minimum preselected distance between each
of the first group of seismic vibrators, a maximum preselected
distance between each of the first group of seismic vibrators, a
weighted distance between each of the first group of seismic
vibrators or an angle between one of the first group of seismic
vibrators and two other of the first group of seismic vibrators.
The function of the location of at least one vibrator in the second
group of seismic vibrators for determining source parameter data
may be the number of vibrators selected or a ground surface
condition associated with at least one of the field survey
locations. The computer program may include instructions to
substantially equalize the energy propagated at field survey
locations according a preselected source acquisition effort.
[0084] In still another embodiment a set of application program
interfaces is embodied on a computer readable medium (e.g.,
associated with one or more elements as illustrated with main
control unit 10 in FIG. 9) for execution on a processor (15) in
conjunction with an Application Program (29) for activating a first
group of seismic vibrators may include an interface that receives
vibrator associated field survey location data to recognize or
determine data for selecting a second plurality of vibrators as a
function of a geometrical relationship associated with vibrator
associated field survey locations of the first plurality of seismic
vibrators. Another interface receives data for selecting a second
plurality of vibrators as a function of the geometrical
relationships. Still another interface receives source parameter
data for the second plurality of vibrators as a function of the
vibrator associated field survey locations. Another interface
receives instruction data for activating the second plurality of
vibrators to impart energy into the earth. The programs may also
include an interface that receives data for selecting a third
plurality of vibrators as a function of at least one geometrical
relationship and an interface that receives source parameter data
for the third plurality of vibrators as a function of vibrator
associated field survey locations. Still another interface may
receive instruction data for activating the third plurality of
vibrators. Another interface may also send data for selecting the
second plurality of seismic vibrators as a function of an offset
distance range from each other vibrator in the first plurality of
seismic vibrators. Another interface may send data for selecting
the third plurality of seismic vibrators as a function of position
within an offset distance from each other vibrator in the first
plurality of seismic vibrators.
[0085] Various aspects of embodiments in this disclosure and their
equivalents may be undertaken with a seismic data processing
system. A seismic data processing system may include any computer
hardware and software combination operable to compute, classify,
process, transmit, receive, retrieve, originate, switch, store,
display, manifest, detect, record, reproduce, handle, or utilize
any form of seismic information, intelligence, or data for
business, scientific, control, or other purposes. For example, a
seismic data processing system may be a personal computer, a super
computer, a network storage device, or any other suitable device
and may vary in size, shape, performance, functionality, and price.
The seismic data processing may include random access memory (RAM),
one or more processing resources such as a central processing unit
(CPU) or hardware or software control logic, ROM, and/or other
types of nonvolatile memory. Additional components of the seismic
data processing system may include one or more disk drives, one or
more network ports for communicating with external devices as well
as various input and output (I/O) devices, such as a keyboard, a
mouse, and a video display. The seismic data processing system may
also include one or more buses operable to transmit communications
between the various hardware components.
[0086] An example of a seismic data processing system is
illustrated in FIG. 9 with a main controller FIG. 9, an embodiment
of a seismic data processing system within which a set of
instructions may enable the system to perform any of the
nonlimiting embodiments or their equivalents disclosed herein. A
seismic data processing system may be a standalone system
comprising at least unit 10, with any additional computer, host
computer, server or blade, or may be connected to other systems
within a network. The main control unit 10 for a seismic data
processing system may include a radio transceiver 11 connected to
an antenna for providing wireless access to systems, networks and
devices. For example, the transceiver 11 enables wireless
communication with the pluralities of vibrators on a seismic survey
(e.g., A through J) and may use antenna 33. In a networked
deployment, the seismic data processing system may operate as a
server or a client in server-client networked environment or as a
member of a distributed network environment. Memory 13 may be
volatile or non-volatile memory with instructions and data. A
central processing unit (CPU) 15 or other processor may be included
with instructions. The instructions may at least partially reside
within the memory 13 and/or within the processor 15 during
execution. Memory 13 and processor 15 may include machine-readable
media.
[0087] Machine-readable media includes solid-state memory such as
cards or other non-volatile memories, random access memories or
other volatile memories, magneto-optical or optical media (e.g.,
disk or tape), or signals embodying computer instructions in a
transmission medium. A machine-readable medium for the embodiments
disclosed herein includes equivalents and successor media.
[0088] An input/output device 17 is provided to send data to, or
receives data from, other system components or devices. At least
one seismic data processing system bus 31 provides communication
between and among components.
[0089] Additionally, main control unit 10 for a seismic data
processing system may include peripherals 21 (keyboards, GPS
receivers, USB adapter, headphones, microphone, wireless audio
transmitter, print adapter, mouse, serial adapter, etc). Various
types of display device 23 may be attached or linked with the main
control unit 10. Network interface equipment such as Network
Interface Controller 25 (NIC) may provide hardwired access to
infrastructure. Other interfaces may include a PCI bus, and USB
ports, etc. A machine readable medium with instructions 27 may be
on a disk drive device and provide additional software and data
storage capability to main control unit 10.
[0090] Processor 15 may carry out graphics/memory controller hub
functions and enable input/output (I/O) functions for I/O device 17
and associated peripherals 21. Peripherals 21 such as a mouse,
keyboard, and tablet are also coupled to other components at the
option of the user. The seismic data processing system bus 31 may
connect to I/O devices 17. Non-limiting examples of a seismic data
processing system bus may include a Peripheral Component
Interconnect (PCI) bus, PCI Express bus, SATA bus or other bus is
coupled to enable seismic data processing system bus 31 to be
connected to other devices which provide main control unit 10 with
additional functionality. Application program interfaces of any
type may interface with Application Program 29 through bus 31 to
other components as needed. A universal serial bus (USB) or other
I/O bus may be coupled to seismic data processing system bus 31 to
facilitate the connection of peripheral devices 21 to main control
unit 10. System basic input-output system (BIOS) may be coupled to
processor 15. BIOS software is stored in nonvolatile memory 13 such
as CMOS or FLASH memory. A network interface controller (NIC) 25 is
coupled to processor 15 to facilitate connection of unit 10 to
other data, information or seismic data processing systems. A media
drive controller (not shown) is coupled to processor 15 through bus
21. An example of a media drive controller may include a baseboard
management controller (BMC). Devices that can be coupled to media
drive controller include CD-ROM drives, DVD drives, hard disk
drives and other fixed or removable media drives. It should be
understood that the technology disclosed herein is not only
applicable to the embodiment illustrated with FIG. 9 but is also
applicable to the other types of seismic data processing
systems.
[0091] While various embodiments have been shown and described,
various modifications and substitutions may be made thereto without
departing from the spirit and scope of the invention. Accordingly,
it is to be understood that the present invention has been
described by way of illustrations and not limitation.
* * * * *