U.S. patent application number 09/553463 was filed with the patent office on 2002-05-09 for energy source for use in seismic acquisitions.
Invention is credited to Brooks, James E., Lezak, Paul A., Tite, Glen-Allan S..
Application Number | 20020053482 09/553463 |
Document ID | / |
Family ID | 22443637 |
Filed Date | 2002-05-09 |
United States Patent
Application |
20020053482 |
Kind Code |
A1 |
Tite, Glen-Allan S. ; et
al. |
May 9, 2002 |
ENERGY SOURCE FOR USE IN SEISMIC ACQUISITIONS
Abstract
A seismic acquisition system includes one or more perforating
shaped charge modules activable to generate seismic signals into an
earth sub-surface. The seismic signals are created by perforating
jets formed by the perforating shaped charge modules when
activated. The perforating jets produce directional seismic signals
that reduce the amount of lateral noise. One or more detectors are
employed to receive signals reflected from the earth sub-surface in
response to the seismic signals.
Inventors: |
Tite, Glen-Allan S.;
(Stafford, TX) ; Brooks, James E.; (Manvel,
TX) ; Lezak, Paul A.; (Lake Jackson, TX) |
Correspondence
Address: |
Patent Counsel
Schlumberger Technology Corporation
14910 Airline
P O Box 1590
Rosharon
TX
77583
US
|
Family ID: |
22443637 |
Appl. No.: |
09/553463 |
Filed: |
April 19, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60130220 |
Apr 20, 1999 |
|
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|
Current U.S.
Class: |
181/116 |
Current CPC
Class: |
G01V 1/104 20130101 |
Class at
Publication: |
181/116 |
International
Class: |
G01V 001/06 |
Claims
What is claimed is:
1. A seismic acquisition system comprising: an energy source
including a perforating shaped charge to generate a seismic signal;
and a detector positioned to detect a reflected signal in response
to a seismic wavefront.
2. The seismic acquisition system of claim 1, wherein the
perforating shaped charge generates a perforating jet.
3. The seismic acquisition system of claim 2, wherein the seismic
wavefront includes a pressure wave generated by the perforating
jet.
4. The seismic acquisition system of claim 1, further comprising an
anchor.
5. The seismic acquisition system of claim 4, wherein the
perforating shaped charge includes a housing fixed with respect to
the anchor.
6. The seismic acquisition system of claim 4, further comprising a
ramming member to drive the anchor into a ground surface.
7. The seismic acquisition system of claim 6, wherein the ramming
member includes a ramming pipe engageable by a ramming system.
8. The seismic acquisition system of claim 6, wherein the ramming
member may be manually manipulated by a user.
9. The seismic acquisition system of claim 1, further comprising a
detonator ballistically engaged to the perforating shaped
charge.
10. The seismic acquisition system of claim 9, further comprising
an electrical wire coupled to the detonator.
11. The seismic acquisition system of claim 1, further comprising
at least another energy source.
12. The seismic acquisition system of claim 1, further comprising
at least another detector.
13. The seismic acquisition system of claim 1, wherein the
perforating shaped charge is positioned to direct the perforating
jet into an earth sub-surface.
14. The system of claim 1, wherein the perforating shaped charge
includes a liner that contributes to generation of the perforating
jet.
15. The system of claim 14, wherein the liner is generally
conically shaped.
16. The system of claim 14, wherein the liner is generally
bowl-shaped.
17. The system of claim 1, wherein the perforating shaped charge
includes a cavity containing an explosive that is un-lined.
18. A method of acquiring seismic data requesting a characteristic
of an earth sub-surface, comprising: positioning an energy source
having a perforating shaped charge; and activating the perforating
shaped charge to transmit a seismic signal into the earth
sub-surface.
19. The method of claim 18, wherein activating the perforating
shaped charge generates a perforating jet.
20. The method of claim 18, further comprising arranging plural
energy sources each including the perforating shaped charge and
activating the perforating shaped charges to create seismic
signals.
21. An apparatus for use in a seismic acquisition system,
comprising: a perforating shaped charge positioned near an earth
surface and activable to generate a seismic signal into an earth
sub-surface.
22. The apparatus of claim 21, further comprising a detector to
receive a signal reflected from the earth sub-surface in response
to the seismic signal.
23. The apparatus of claim 21, further comprising plural
perforating shaped charges arranged in a predetermined pattern.
Description
[0001] This application claims the benefit, under 35 U.S.C.
.sctn.119, of U.S. Provisional Patent Application Serial No.
60/130,220, entitled, "Energy Source for Use in Seismic
Acquisitions," filed on Apr. 20, 1999.
BACKGROUND
[0002] The invention relates to energy sources used for acquisition
of seismic data of sub-surface formations.
[0003] To perform a field seismic survey of the earth's
sub-surface, a seismic energy source is used to generate a seismic
signal (also referred to as a seismic pressure wave). The seismic
signal is transmitted into the earth's sub-surface, and a portion
of the seismic signal is reflected back towards the surface of the
earth where one or more detectors may be positioned to receive the
reflected signal. The seismic data received is used to determine
geophysical information about the earth's sub-surface.
[0004] A typical energy source used for seismic acquisition
includes dynamite that is exploded in a hole of some depth. For
reliable performance, the dynamite may need to be placed in a
relatively deep hole. In addition, multiple holes may be employed
to create a pattern of seismic signals. Explosion of the dynamite
creates expanding gas volume, downwardly moving shock waves as well
as a substantial amount of lateral shock waves that are directed
side ways. Useful data typically is derived from reflected signals
of downwardly moving shock waves. The lateral shock waves from the
energy source generate noise trains that frequently reduce the
detector's ability to see the reflected signal. Another
disadvantage of using explosives such as dynamite as energy sources
in seismic acquisition is that explosions may disrupt the
environment around the survey site. With increased environmental
protection concerns, use of such energy sources is generally not
desirable, especially in environmentally sensitive areas.
[0005] Various types of alternative energy sources have been
proposed or implemented. For example, use of air-gun energy sources
as well as low frequency marine vibrators have been used. However,
a need continues to exist for improved energy sources used in
seismic acquisition systems.
SUMMARY
[0006] In general, according to an embodiment, a seismic
acquisition system includes an energy source having a perforating
shaped charge to generate a seismic signal. A detector is
positioned to detect a reflected signal in response to a seismic
wavefront.
[0007] Other features and embodiments will become apparent from the
following description and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 illustrates an embodiment of a seismic acquisition
system.
[0009] FIG. 2 illustrates an energy source including a perforating
shaped charge according to one embodiment that is used in the
seismic acquisition system of FIG. 1.
[0010] FIG. 3 illustrates a charge retainer, detonator, and
detonating wire in the energy source of FIG. 2.
[0011] FIG. 4 illustrates a ramming system for positioning the
energy source of FIG. 2 in the earth.
[0012] FIG. 5 illustrates detonation of a perforating shaped charge
with a conical liner in which a perforating jet is formed.
[0013] FIG. 6 illustrates a perforating shaped charge with a
generally bowl-shaped liner.
[0014] FIG. 7 illustrates a perforating shaped charge without a
liner.
DETAILED DESCRIPTION
[0015] In the following description, numerous details are set forth
to provide an understanding of the present invention. However, it
will be understood by those skilled in the art that the present
invention may be practiced without these details and that numerous
variations or modifications from the described embodiments may be
possible.
[0016] According to some embodiments of the invention, an energy
source used in a seismic acquisition system includes a perforating
shaped charge that when detonated produces a perforating jet that
penetrates the earth's sub-surface. The perforating jet of the
shaped charge is used as an energy propagating medium, which is
different from typical energy sources (which may include dynamite)
used in conventional systems. As used here, "perforating shaped
charge" refers to any explosive device that produces a perforating
jet directed along a general direction. One or more energy sources
including perforating shaped charges positioned near the earth's
surface are activated to generate seismic signals (from formation
of corresponding perforating jets). Signals reflected from the
earth sub-surface are then detected and measured to determine
characteristics of the earth's sub-surface.
[0017] Referring to FIG. 1, a seismic acquisition system 10 may
include one or more energy sources 12 that are positioned in holes
14 of predetermined depths, e.g., less than about 100 feet. The
depth may be selected between a range of about 10-100 feet. The
holes 14 may have relatively shallow depths due to the improved
energy propagation medium provided by a perforating jet. The energy
sources 12 may be coupled to a surface controller 16, where an
operator may selectively activate one or more of the energy sources
12.
[0018] Activation of the surface controller 16 causes detonation of
the perforating shaped charges, which propagates energy along
desired paths (in most cases along generally downward paths). The
propagated energy is generally along the direction of the
perforating jet. An advantage of using a perforating shaped charge
in the energy source 12 according to some embodiments is the
improved ability to control the direction of seismic signals sent
into the earth's sub-surface 20. By using perforating shaped
charges, generation of lateral signals that contribute to noise may
be reduced. Reflected signals from the sub-surface 20 may be
received by one or more detectors 18 positioned at or in the
surface. The detectors 18 may be coupled to the surface controller
16, which may receive the acquired data for processing and/or
storage.
[0019] Referring to FIG. 2, a perforating shaped charge (PSC)
assembly 100 for use as an energy source 12 includes a perforating
shaped charge (PSC) module 112 that includes housing sections 114
and 116. An explosive charge 118 is contained inside the shaped
charge housing section 114, with a liner 120 lining the outside of
the explosive charge 118. The housing section 114 provides the
container for the explosive charge, while the housing section 116
is attached to the housing section 114 to provide a sealed cap.
Other arrangements of the PSC module 112 may also be possible in
further embodiments.
[0020] As illustrated in FIG. 2, the shaped charge has a generally
conical liner that is adapted to provide a relatively narrow and
deep perforating jet. Upon detonation of the explosive charge 118,
the liner 120 collapses to form a directional perforating jet.
Generally, the liner 120 is formed of a metallic material, e.g.,
copper, nickel, silver, gold, tantalum, lead, tungsten, or a metal
alloy. Other types of materials may also be used that are
sufficiently high density and ductile. In other embodiments, a
perforating shaped charge may not incorporate a liner as part of
the charge cavity, relying instead on a lower density jet formed
from explosive gases. In such embodiments, the perforating shaped
charge includes a cavity containing an explosive charge that is
un-lined.
[0021] In alternative embodiments, liners of other shapes may also
be implemented, including liners having generally the following
shapes: hemispherical, parabolic, trumpet, tulip, and so forth.
Such other types of liners may generally be referred to as
generally bowl-shaped, and are often adapted to produce wider and
shallower perforating jets than conical liners. Perforating shaped
charges employing these types of liners may be referred to as big
hole perforating shaped charges. The geometry of the liners
determines the width and depth of the perforating jet once the
shaped charge in the perforating charge module 112 is
detonated.
[0022] An un-lined shaped charge may include an explosive shaped to
either a generally conical or bowl-shaped geometry.
[0023] In the illustrated embodiment of FIG. 2, the PSC module 112
is attached to an anchor 110. The anchor 110 provides a shoulder
122 on which a portion of the shaped charge housing section 116
sits. The upper portion of the anchor 110 engages a ramming stem
collar adapter 104. To hold the PSC module 112 in place, a charge
retainer 106 is mounted and secured over the module 112. The
retainer 106 includes a bore 124 in which a detonator 130 (FIG. 3)
may be positioned. The detonator 130 is ballistically coupled to or
engaged with the explosive charge 118 in the shaped charge module
112. The detonator 130 is also coupled to a detonating wire 132
that extends into the bore 126 of a ramming pipe 102 that is
attached to the ramming stem collar adapter 104. Alternatively, a
ramming member other than the ramming pipe 102 may be attached to
the PSC assembly 100.
[0024] The PSC assembly 100 that is fitted to the end of the
ramming pipe 102 may be rammed into the ground to position the PSC
assembly at a desired depth. Referring further to FIG. 4, the
ramming pipe 102 is part of a ramming system 200. A ratchet member
206 is attached along a longitudinal portion of the ramming pipe
102. The ratchet member 206 is engaged to be moved up or down by
rotational movement of a gear 204 that is driven by a motor 208. In
the ramming system 200, an opening 210 may be provided in the
ramming pipe 102 through which the detonating wire 132 may be
passed through to connect to a detonating device (not shown).
[0025] In other embodiments, other types of ramming systems may be
used. For example, the ramming pipe 102 (or other ramming member)
may be manipulated by hand to enable operators to manually (by use
of loading poles, for example) ram one or more PSC assemblies 100
into the ground. Because of the improved shock communication
characteristics of perforating shaped charges, the depth at which
the PSC assemblies 100 are placed may be sufficiently shallow to
enable such manual ramming. Manual ramming is particularly feasible
if the earth is sufficiently soft. A benefit offered by manual
ramming is that heavy equipment, such as the ramming system 200
(FIG. 4), may be avoided at the survey site. In other embodiments,
instead of ramming the PSC assembly 100 into the ground, one or
more holes may be drilled followed by placement of one or more PSC
assemblies into the drilled holes.
[0026] According to some embodiments, the loading sequence of the
PSC assembly 100 may be as follows. The PSC module 112 is placed
and secured in (or otherwise fixed with respect to) the disposable
anchor 110. The charge retainer 106 is then placed over the PSC
module 112 and the detonator 130 is positioned in the charge
retainer 106. The PSC assembly 100 is then attached to the ramming
pipe 102, with the detonating wire 132 passed through the inner
bore 126 of the ramming pipe 102. The PSC assembly 100 is then
rammed into the ground, either by hand or by using a ramming system
(such as system 200). After the PSC assembly 100 is rammed into the
ground to some predetermined depth below the surface, the ramming
pipe 102 detaches from the PSC assembly 100 as the ramming pipe 102
is retracted. The detonating wires are then attached to a
detonating device, and the acquisition phase can begin.
[0027] When an electrical signal is transmitted over the detonating
wire 132, the detonator 130 is initiated. This causes detonation of
the explosive charge 118, which in turn causes the collapse of the
liner 120. As illustrated in FIG. 5, formation of a perforating jet
150 from detonation of the explosive charge 118 and collapse of the
liner 120 is illustrated. As illustrated, the perforating jet 150
is highly directional. Due to the conical shape of the liner 120, a
narrower and deeper jet is formed. However, if a big hole charge,
such as a charge 300 shown in FIG. 6, having a generally
bowl-shaped liner 302 is employed, then the produced perforating
jet (not shown) may be wider and slightly shallower. As shown in
FIG. 7, a perforating shaped charge 400 may also be designed
without a liner. The shaped charge 400 includes an explosive 404
contained in a housing section 402. With the liner-less perforating
shaped charge, the explosive is shaped to produce a lower density
perforating jet produced from explosive gases. The explosive 404
may be formed to various shapes, such as generally conical or
generally bowl-shaped (e.g., hemispherical, parabolic, trumpet,
tulip, etc.).
[0028] The PSC assembly 100 in accordance with some embodiments,
may be used in many applications, including
environmentally-sensitive applications. Seismic surveys can be
performed in transition zone applications where explosive charges
may be mechanically rammed into a soft clay, sand, or mud
sub-surface to predetermined depths. The ramming technique provides
a superior, more reliable earth-to-charge coupling than
conventional techniques. Due to the enhancement in charge coupling
according to some embodiments, the requirement for deeper holes may
be significantly reduced.
[0029] Some embodiments of the invention have one or more of the
following advantages. Increased downward energy is provided due to
the directional perforating jet of a shaped charge. Because of the
directivity of seismic energy produced by a PSC assembly, less
explosive weight per charge may be employed. In addition, because
of the directivity of the seismic signal generated by the PSC
assembly according to embodiments, improved data quality may be
provided since the signal-to-noise ratio is increased. Because of
less laterally coupled energy (ground roll) that is generated by
energy sources according to some embodiments, the need for multiple
pattern holes may be reduced and in some cases eliminated. As a
result, the drilling effort and associated costs may be reduced and
productivity may be increased. In addition, due to increased charge
directivity and charge couple improvements, surface blow-outs
(cratering) due to bridging may be reduced.
[0030] While the invention has been disclosed with respect to a
limited number of embodiments, those skilled in the art will
appreciate numerous modifications and variations therefrom. It is
intended that the appended claims cover all such modifications and
variations as fall within the true spirit and scope of the
invention.
* * * * *