Note: Descriptions are shown in the official language in which they were submitted.
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A PERFORATIRIG G11N HAVING A PLLlRAL1TY OF CHARGES
This application is a division of Canadian application Serial No. 2,145,740
filed
March 28, 1995.
BACKGROUND OF THE Il1VEN'I'ION
The subject matter of the present invention relates to a method and
apparatus for simultaneously initiating the detonation of a plurality of
shaped charges in a perforating gun adapted to be disposed in a wellbore.
The perforating gun includes an electrical current carrying conductor, a
current pulse generator connected to the conductor, a plurality of shaped
charges, and a plurality of exploding foil or exploding bridgewire initiators
connected, respectively, between the plurality of charges and the cuzzent
car*ying conductor for simultaneously detonating the charges in response to
a pulse of current from the current pulse generator.
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ti
Exploding bridge wire initiators and exploding foil initiators are known in
the art. For example, U.S. Patent 3,181,463 to Morgan et al discloses an
exploding bridge wire detonator. In addition, U.S. Patent 5,088,413 to
Huber et al, assigned to the same assignee as that of the present invention,
entitled "Method and Apparatus for Safe Transport Handling Arming and
Firing of Perforating Guns using a Bubble Activated Detonator" discloses an
exploding foil "bubble activated" initiator which utilizes a bubble instead of
a flying plate to detonate an explosive charge. In addition,
U.S. Patent No. 5,347,929, filed September 1, 1993, entitled "Firing
System for a Perforating Gun including an Exploding Foil Initiator and an
Outer Housing for conducting Wireline current and EFI current", assigned'
to the same assignee as that of the present invention, discloses a firing
head, utilizing an exploding foil flying plate or the bubble activated
initiator
of the Huber et al patent, for use in a perforating gun. In addition,
exploding foil "flying plate" initiators are known in the art. For example,
U.S. Patent 4,788,913 to Stroud et al, entitled "Flying Plate Detonator using
a High Density High Explosive" discloses an exploding foil flying plate
initiator. The flying plate initiator has been disclosed in connection with a
perforating gun in U.S. Patent 4,762,067 to Barker et al, entitled "Downhole
Perforating Method and Apparatus using Secondary Explosive Detonators".
However, the exploding foil "flying plate" initiator in the Barker et al
patent
patent initiates a detonation wave in a detonating cord, and the detonation
wave in the detonating cord subsequently detonates a plurality of charges in
the perforating gun.
Instead of using a conventional detonation wave to detonate a plurality of
shaped charges in a perforating gun, it would be desirable to use an
electrical current pulse generator to flow a pulse of current in an electrical
current carrying conductor and to use that pulse of current to detonate a
plurality of shaped charges in a perforating gun.
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U.S. Patent 5,094,167 to Hendley, Jr uses an ordinary current conducting in
an electrical conductor to detonate a plurality of shaped charges in a
perforating gun. Each of the shaped charges in the Hendley patent include
an initiator known as a semiconductor bridge initiator. Although the
semiconductor bridge initiator is useful for some purposes, it would be more
desirable to use a plurality of exploding foil or exploding bridgewire
initiators, in lieu of the semiconductor bridge initiator, to detonate a
respective plurality of shaped charges in a perforating gun. None of the
shaped charges in the Hendley patent utliize an exploding bridgewire
initiator or an exploding foil flying plate or bubble activated initiator (EFI
initiator).
U.S. Patent 4,658,900 to Stout entitled "High Energy Firing Head for Well
Perforating Guns" discloses a single shaped charge which includes a flying
plate initiator. This single shaped charge is pointing downwardly in a
perforating gun, and the jet from the shaped charge initiates a detonation
wave in a detonating cord. However, since the detonating cord is connected
to the plurality of shaped charges, the shaped charges are detonated by the
detonation wave in the detonating cord, not by an electrical current flowing
in an electrical current conductor.
In addition, recall that, in addition to a plurality of shaped charges and a
corresponding plurality of initiators, a current pulse generator is also
connected to the electrical current carrying conductor. The current pulse
generator could comprise a prior art charging circuit including a large
capacitor charged by a charging current from a high voltage source, or a
prior art compressed magnetic flux (CMF) generator. The prior art CMF
generator is described in an article entitled "Small Helical Flux
Compression Amplifiers" by J.E. Gover, O.M. Stuetzer, and J.L. Johnson,
Sandia Laboratories, Albuquerque, New Mexico, printed in "Megagauss .
Physics and Technology", 1979. The CMF generator is also described in an
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article entitled "The Central Power Supply", Showcase for Technology,
conference and exposition, 1981.
Therefore, it would be desirable to provide a new perforating system
adapted to be disposed in a wellbore which propagates a current pulse from
a current pulse generator through an electrical current carrying conductor
to a plurality of initiators corresponding, respectively, to a plurality of
shaped charges of the perforating system, and to use that current pulse to
simultaneously detonate the plurality of initiators and the plurality of
shaped charges of the perforating system.
In addition, it would be further desirable to provide a new preferred design
for a shaDed charge adapted for use in connection with the new perforating
system.
It would be further desirable to provide a new preferred design for an
electrical current carrying conductor adapted for use in connection with the
new shaped charge in the new perforating system.
It would be further desirable to provide a new preferred design for a current
pulse generator adapted for use in connection with the new current carrying
conductor in the new perforating system.
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SUMMARY OF THE INVENTION
In accordance with one aspect of the present
invention, there is provided a perforating gun, comprising:
a shaped charge adapted to detonate; an electrical current
carrying conductor adapted for conducting a current, said
conductor including a flat conductor cable helically wrapped
around said shaped charge; and an initiator adapted to
detonate interconnected between the conductor and the shaped
charge, the initiator detonating in response to the current
in the conductor, the shaped charge detonating in response
to the detonation of the initiator.
In accordance with another aspect of the present
invention, there is provided a perforating gun, comprising:
a shaped charge adapted to detonate; an electrical current
carrying conductor adapted for conducting a current, said
conductor including a flat sheet conductor wrapped around
said shaped charge; and an initiator adapted to detonate
interconnected between the conductor and the shaped charge,
the initiator detonating in response to the current in the
conductor, the shaped charge detonating in response to the
detonation of the initiator.
In accordance with yet another aspect of the
present invention, there is provided a method of
manufacturing a perforating gun, comprising the steps of:
locating a plurality of shaped charges in a loading tube;
and helically wrapping an electrically conductive current
carrying conductor cable around the plurality of shaped
charges, the cable being disposed in contact with the
plurality of charges.
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A system may provide an explosive device, an
electrical current carrying conductor, and an exploding foil
or exploding bridgewire initiator disposed between the
current carrying conductor and the explosive device and
electrically connected to the current carrying conductor for
detonating the explosive device in response to an electrical
current conducting in the current carrying conductor.
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A system may be provided that includes a shaped charge, an
electrical current carrying conductor, and an exploding
foil or exploding bridgewire initiator disposed between the current carrying
conductor and the shaped c.harge and electrically connected to the current
carrying conductor for detonating the shaped charge in response to an
electrical current .canducting in the conductor.
A system may be provided that includes a shaped charge, an
electrical current carrying conductor, and an exploding
foil flying plate initiator disposed between the current carrying conductor
and the shaped charge and electricaIly connected to the ctuzent carrying
conductor for detonating the shaped charge in response to an electrical
current conducting in the coaductor.
A system may be provided that includes a shaped charge, an
electrical current carrying conductor, and an exploding
foil bubble activated initiator disposed between the currert carrying
conductor and the shaped charge and electrically connected to the current
carrying conductor for detanating the shaped charge in response ta an
electrical current conducting in the conductor.
A system may be provided that includes an electrical current
carrying conductor, a shaped charge connected to one
end of the current carrying conductor, a compressed magnetic flux current
pulse generator connected to the other end of the current carrying conductor
for generating a current pulse and conducting the current pulse in the
conductor, and an exploding foil or exploding bridgewire initiator disposed
between the current carrying conductor and the ahaped charge and
electrically connected- to the' eandu.ctar for detonating the shaped charge in
response to the current pulse conducting in the current carrying conductor.
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A system may be provided that includes an electrical current
carrying conductor, a shaped charge connected to one
end of the current carrying conductor, a current pulse generator, which
includes a charging capacitor connected to a discharge switch and a high
voltage supply, connected to the other end of the current carrying conductor
for generating a current pulse and conducting the current pulse in the
conductor, and an exploding fail or exploding bridgewire initiator disposed
between the current carrying conductor and the shaped charge and
electricaIly connected to the conductor for detonating the shaped charge in
i0 response to the current pulse conducting in the current carrying conductor.
A system may be provided that includes a plurality of
electrical current carrying conductors, a plurality of shaped
charges connected to one end of the current carrying conductors, a current
pulse generator cannected to the other end of the current carrying
conductors for generating a current pulse and conducting the current pulse
in the conductors, and a plurality of exploding foil or exploding bridgewire
initiators disposed, respectively, between the plurality of shaped charges
and the current carrying conductors and electxicaIly connected to the
conductors for simultaneously detonating the plurality of shaped charges in
response to the current pulse conducting in the current carrying conductor,
where the current pulse generator includes a plurality of charging
capacitors connected, respectively, to the plurality of current carrying
conductors and to a high voltage source.
A perforating gun may be provided that includes a plurality
of shaped charges, an electrical current carrying
conductor, and a plurality of exploding foil or exploding bridgewire
initiators
disposed, respectively, between the plurality of shaped charges and the
current carrying conductor and electrically connected to the current carrying
conductor for simultaneously detanating the plurality of shaped charges in
response to an electrical current conducting in the conductor.
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A perforating gun may be provided that includes a plurality
of shaped charges, an electrical current carrying
conductor, and a plurality of exploding foil flying plate initiators disposed,
respectively, between the plurality of shaped charges and the current
carrying conductar and electrically connected to the current carrying
conductor for simultaneously detonating the plurality of shaped charges in
response to an electrical current conducting in the conductor.
l0 A perforating gun may be provided that includes a plurality
of shaped charges, an electrical current carrying
conduetor, and a plurality of explading foil bubble activated initiators
disposed, respectively, between the plura}ity of shaped charges and the
current canyi.ng conductor and electrically connected to the current carr,ying
conductor for simultaneously detonating the plurality of shaped charges in
response to an electrical crxrrent conducting in the conductar.
A perforating gun may be provided that includes a plurality
of shaped charges, an electrical current carrying flat
conductor cable helically wrapped around and in contact With the plurality
of shaped charges, and a plurality of exploding foil or exploding bridgewire
initiators disposed, respectively, between the plurality of shaped charges
and the current carrying flat conductar cable and electrically cannected to
the current carrying flat conductor cable for simultaneously detonati.ng the
plurality of shaped charges in response to an electrical current conducting in
the conductor.
A perforating gun may be provided that includes a plurality
of shaped charges, an electrical current carrying flat
sheet of canductor material wrapped around the entire circumference of the
perforating gun and in contact with the plurality of shaped charges, and a
plurality of exploding foil or exploding bridgewire initiators disposed,
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respacnvely, batweOn the plurality of shaped charges and the cu-rent
carryi.ng flat sheet of conductor.material.and electrically connected to the
current ca.zrying flat sheet of conductor material for simultaneously
detonating the plurality of shaped charges in respflnse to an electrical
cturent conduct,ing in the conductor.
A system may be provided that includes a perforating gun
having a plurality of shaped charges, an electrical current
carr3Ting conductor having one end connected to the plurality of shaped
charges, a compressed magnetic lux current pulse generator con.nected to
the other end of the rurrent carrying conducEor, and a plurality of exploding
foil or exploding bridgewire initiators disposed between the plurality of
shaped charges and the current carrying conductar for si.multaneously
detonating the plurality of shaped charges ia responae to an electrica].
current conductiag in the c+T**pnt carr-ying conductor.
A system may be provided that includes a perforating gun
having a plurality of shaped charges, an electrical current
caxzying conductor having one end connected to the plura.Iity of shaped
charges, a current pulse generator, including a charging capacitor connected
to a high voltage supply and a discharge switch, connected to the other end
of the current carrying conductor, and a plurality of exploding foil or
exploding bridgewire initiators disposed between the plurality of shaped
charges and the mu-rent carrying conductor for simultaneously detonating
.25 the plurality of shaped charges in response to an electrical current
conducting in- the current carrying canductor.
A system may be provided that includes a perforating gun
having a plurality of shaped charges, a plurality of
.30 electrical current carrying conductors connected to the plurality of
shaped
charges, a current pulse generator connected to the current carrying
conductors, and a plurality of exploding foil or exploding bridgewire
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initiators dispQsed, respectively, between the plurality of shaped charges
and the current carrying conductors for simultaneously detonating the
plurality of shaped charges in response to an electrical current conducting in
the current carrying conductors, where the current pulse generator includes
a plurality of charging capacitors connected, respectively, to the plurality
of
current carrying conductors and to a high voltage source.
A detonation transfer unit may be provided that is adapted
to be disposed between a first perforating gun and a
second perforating gun of a perforating apparatus for transferring a
detonation wave from a detonating cord of the first perforating gun to a
detonating cord of the second perforating gun, the detonation transfer unit
including a pressure bulkhead adapted to isolate and insulate the pressure
disposed within an interior of the first perforating gun from the pressure
disposed within an interior of the second perforating gun, an explosive
associated with the first perforating gun being disposed in abutment against
one side of the pressure bulkhad, and a piezoelectric ceramic being
disposed in abutment against the other side of the pressure bulkhead and
connected to a detonator associated with the second perforating gun.
A shaped charge may be provided that is adapted for use in
connection with a new perforating system in accordance
with thP present invention including a new secondary explosive pellet
disposed within an apex of the shaped charge, the explosive material of the
new secondary explosive pellet being specifically selected for use in
connection with exploding foil initiators or exploding bridgewire initiators.
A shaped charge may be provided that is adapted for use in
~connection with a new perforating system in accordance
v6th the present invention including a new secondary explosive pellet
having a nrst density and disposed within an apex of the shaped charge and
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a main body of explosive having a second density, the nrst density of the
pellet being less than the second density of the main body of explosive.
A system, such as a perforating apparatus, may be
provided that is adapted to be disposed in a
wellbore, includes a first current pulse generator for generating a pulse ai
current; a first electrical current carrying conductor connected to the
current
pulse generator for receiving the pulse of current from said current pulse
generator and conducting said current; a first plurality of explosive devices,
such as a first plurality of shaped charges in the perforating apparatus,
which are adapted to detonate; and a first plurality of initiators disposed,
respectively, between the first plurality of explosive devices and the first
electrical current carrying conductor and electricaIly connected to the first
current carrying conductor for receiving the current from the first current
carrying conductor and substantially simultaneously detonating in response
to the current, the first plurality of explosive devices substantially
simultaneously detonating in response to the substantially simultaneous
detonation of the first plurality of i.nitiators. A second electrical current
carrying conductor is connected to the first electrical current carrying
conductor via an intermediate adaptor. A second current pulse generator is
electrically connected between the intermediate adaptor and the second
current carrying conductor, and a second plurality of initiators are mounted
on the second current carrying conductor. In the same manner as described
above in connection with the first plurality of explosive devices, a second
plurality of explosives devices, such as a second plurality of shaped charges,
are substantially simultaneously detonated in response to the substantially
simultaneous detonation of the second plurality of initiators. Therefore, the
detonation of the first plurality of explosive devices by current flowing in
the
first electrical current-carzying-conductor is repeated again in cbnnection
with the second plurality of explosive devices and the second electricad
current carrying conductor. Each of the initiators include either an
exploding foil flying plate initiator or an exploding foil bubble activated
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initiator or an exploding bridgewire initiator (hereinafter collectively
referred to as an "EFI initiator"). Each of the initiators mounted on the
current carrying conductor substantially simultaneously detonate in
response to the pulse of current flowing in the conductor. When the
plurality of initiators substantially simultaneously detonate, the plurality
of
explosive devices, such as the plurality of shaped charges, also substantiaIly
simultaneously detonate.
The plurality of exploding foil (either flying plate or
bubble activated) initiators may be mounted on an
electrical current carrying flat cable conductor, and the
flat conductor cable is helically wrapped around the exterior of a new
perforating apparatus in accordance with the present invention in a manner
which allows the plurality of exploding foil initiators on the flat conductor
cable to abut, respectively, against.the apex of a plurality of new shaped
charges. In response to the current pulse conducting in the flat cable
conductor, the exploding foil initiators will simultaneously detonate. When
the exploding foil initiators detonate, the plurality of shaped charges also
substantially simultaneously detonate. The flat cable conductor includes a
first plurality of parallel connected exploding foil or exploding bridgewire
initiators, a second plurality of parallel connected exploding foil or
exploding
bridgewire initiators, a third plurality of paraIlel connected exploding foil
or
exploding bridgewire initiators, etc. The first plurality of.parallel
connected
exploding foil or exploding bridgewire initiators detonate simultaneously in
response to the current conducting in the flat cable conductor which is
helically wrapped around the exterior of the perforating gun. The second
plurality of parallel connected exploding foil or exploding bridgewire
initiators detonate simultaneously with the detonation of the first plurality
of parallel connected initiators in response to the current conducting in the
flat cable conductor. The third plurality of parallel connected exploding foil
or exploding bridgewire initiators detonate simultaneously with the
detonation of the first plurality of parallel connected initiators and the
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secand plurality of parallel connected i.nitiators in response to the current
conducting in the flat cable .conductor, etc. As a result, alI of the parallel
connected initiators on the flat cable conductor detonate approximately
si.m.ultanecusly, that is, over a short period of ti.me of approximately 10D
nano-seconds.
Instead of using a flat cable conductor which wraps helically
around the perforating apparatus, a sheet containing a
plurality of exploding foil or exploding bridgewire initiators
may be utilized. The sheet has a width and the width of the
sheet is approximately equal to a circumference of the perforating
apparatus. The sheet of initiators is wrapped completely around the entire
circumference of the perforating apparatus in a manner which allows the
plurality of initiators on the aheet to abut, respectively, .agai.nst an apex
of
the plurality of shaped chargn..s. Since each exploding foil or exploding
bridgewire initiator abuts against it's respective shaped charge, when the
plura}ity of exploding foil or eaploding bridgewire initiatozs on the aheet
substantially simultaneously detoaate, the plurality of shaped charges of
the perfnrating apparatus wiIl also substantially siuaultaneously detoa.ate.
Since the plurality of shaped charges detonate in
response to a current conducting in an electrical
current carrying conductor and since a plura3ity of exploding foil or
exploding bridgewire i.nitiators are mounted on the con.ductor adjacent the
-,5 shaped charges, each of the shaped charges must now be redesigned to
detonate in response to a detonation of an exploding bridgewire or an
impact by a flying plate or an expanding bubble of an exploding foil flying
plate or bubble activated initiator. Recall that each shaped charge includes
a main body of explosive and a secondary explosive pellet disposed within
the apex of the charge adjacent the main body of explosive. Therefore, the
secondary explosive pellet must now detonate in response to a detonation of
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an exp]Qc'iing bridgewire or in respanse to an impact from a flyi.ng plate or
an expa.nding bubble of an exploding foil flying plate or bubble activated
initiator. As a result, the secondary explosive pellet must now be selected
from the.followi.ng group consisting of: HN5-1V, NONA, H112Y,, RDX, pETli,
TATB, ABH, BTX, 'DPO, DODECA, Tripicryl-trinitrobenzene, barium
styphnate, and meta]Iic picrate salts.
During manufacture, the secondary explosive pellet of a shaped
charge, for use in connection with the perforating apparatus,
is pressed to a first density, and the -mai.n body of explosive is,pressed to
a
second density, where the first density of the secandary explosive pellet is
less t.han the second density of the main body of explosive.
A current pulse generator may be provided that is
1$ electrically connected to an electrically conductive
layer of the flat cable conductor which is helically wrapped around an
int,erior or an exterior of the perforati.ng apparatus, or the current pulse
generator is electrically connected to an electrically canducEive layer
disposed within the flat sheet of e-ploding foil or exploding bridgewire
initiators which is wrapped around the circtuuferenee of the perforating
apparatus. The current pulse generator develops a current pulse of
sufficient amplitude and pulse width to substantially simultaneously
detonate each of the plurality of exploding foil or exploding bridgewire
initiators on the flat cable conductor or the flat sheet. The current pulse
generator can include the conventional charging capacitor connected to a
high voltage source and a-discharge switch. The current pulse generator
can also comprise a plurality of parallel connected charging capacitors
connected to a high-voltage source, a plurality of discharge switches
connected to the plurality of capacitors, and a corresponding plurality of
conductors connected, respectively, to the plurality of discharge switches
and the plurality of shaped charges. However,
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the current pulse generator may be a compressed
magnetic flux (CMF) generator which generates a current
pulse from a last turn of an inductance coil in response to a detonation wave
induced in an explosive armature of the CMF generator. The detonation
wave in the armature of the CMF generator is induced therein by a separate
fring system disposed in the perforating apparatus. Although any suitable
firing system may be iitiLized, one enample of that separate firing sy.stem is
disclosed in U.S. Patent No, 5,347,929, filed 9-1-
93, entitled "Firing System for a Perforating gun Including an Exploding
Foil Initiator and an Outer Housing for Conducting Wireline Current and
EFI Current".
A detonation transfer unit may be provided that is adapted
1$to be disposed between a first perforating gun and a
second perforating gun of a perforating apparatus. The detonation transfer
unit transfers a detonation wave from a first detonating cord of the first
periorating gun to a second detonating cord of the second perforating gun of
the perforating apparatus. The detonation transfer unit includes a pressure
bulkhead which is adapted to isolate and insulate the pressure disposed
within the interior of the nrst perforating gun from the pressure disposed
within the interior of the second perforating gun. An explosive associated
with the first detonating cord of the first perforating gun is disposed in
contact with one side of the pressure bulkhead and a piezoelectric ceramic
disc is disposed in contact with the other side of the pressure bulkhead. The
piezoelect~-zc ceramic stores energy and is connected to a detonator. The
detonator is connected to the detonating cord of the second perforating gun.
When a first detonation wave from the first detonating cord of the first
periorating gun hits the pre"ssure bulkb.ead; the explosive plane wave of the
first detonation wave is transferred through the bulkhead to the
piezoelectric ceramic disposed on the other side of the bulkhead thereby
causing the energy stored in the piezoelectric ceramic to dump into the
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detonator of the second detonating cord. As a result, in response to the
energy from the piezoelectric ceramic, the detonator initiates the
propagation of a second detonation wave in the second detonating cord of
the second perforating gun of the perforating apparatus.
Further scope of applicability of the present invention will become apparent
from the detailed description presented hereinafter. It should be
understood, however, that the detailed description and the specific
examples, while representing a preferred embodiment of the present
invention, are given by way of illustration only, since various changes and
modifications within the spirit and scope of the invention will become
obvious to one slfllled in the art from a reading of the following detailed
description_
BRIEF DESCRIPTION OF THE DRAWINGS
A full understanding of the present invention will be obtained from the
detailed description of the preferred embodiment presented hereinbelow,
and the accompanying drawings, which are given by way of illustration only
and are not intended to be limitative of the present invention, and wherein:
Figure 1 illustrates a perforating gun disposed in a wellbore including a
plurality of shaped charges connected to either a detonating cord or an
electrical conductor.
Figures 2-3 illustrate the plurality of shaped charges of figure 1 connected
to an electrical current carrying conductor, each shaped charge including an
initiator, such as an exploding foil flying plate initiator, or an exploding
foil
bubble activated initiator, or an exploding bridgewire initiator.
Figure 4 illustrates a cross section of the electrical current carrying
conductor of figure 3.
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Figure 5 illustrates a section of figure 4 taken along section lines 5-5 of
figure 4.
Figure 6 illustrates an expanded view of one of the shaped charges of figures
2 or 3 including the current carrying conductor and an associated exploding
foil "flying plate" initiator.
Figure 7 illustrates a section of the current carrying conductor of figure 6
taken along section lines 7-7 of figure 6.
Figure 8 illustrates an expanded view of one of the shaped charges of figures
2 or 3 including the current carrying conductor and an associated exploding
foil 'bubble activated" initiator.
Figure 9 illustrates a section of the current carrying conductor of figure 8
taken along section lines 9-9 of figure 8;
Figure 10 illustrates a conventional perforating gun having shaped charges
which are connected to a conventional detonating cord.
Figure 11 illustrates a perforating gun having shaped charges which are
connected to an electrical conductor in the form of a foil strip which is
longitudinally disposed within the perforating gun connected to each shaped
charge and energized by a current pulse from, for example, a compressed
magnetic flux (CMF) current pulse generator.
Figure 12 iIIustrates a perforating gun having a first plurality of shaped
charges which are connected to a first electrical conductor in the form of a
foil strip which is helically wrapped around the perforating gvn in a manner
which allows the plurality of initiators of the foil strip to abut against
their
respective plurality of shaped charges, the first electrical conductor being
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energized by a current pulse from a first compressed magnetic flux (CMF)
generator, and a second electrical conductor also in the form of a foil strip
helically wrapped around the gun and energized by a second CMF
generator.
Figure 13 iIlustrates an external view of the foil strip of figure 12.
Figure 14 illustrates an interaal view of only one initiator of the plurality
of
parallel connected initiators which are disposed on the inside portion of the
Ioil strip of figure 12.
Figure 15 illustrates the electrical current path which traverses all of the
parallel connected initiators disposed on the interior or inside portion of
the
entire foil strip of
figure 12.
Figure 16 illustrates a cross sectional view showing all of the individual
layers which comprise the foil strip of figures 12-15.
Figure 17 illustrates a shaped charge which is used in connection with an
exploding foil (flying plate or bubble activated) initiator or an exploding
bridgewire initiator of the perforating guns of figures 11, 12, and 26 where
the shaped charge includes a pellet of secondary explosive which is
responsive to a detonation of it's respective initiator for detonating the
primary explosive in the shaped charge.
Figure 18 illustrates a first embodiment of a prior art current pulse
generator for generating a current pulse, where the current pulse energizes
the flat cable conductor of figures 12, 13, and 15 or the sheet of initiators
of
figure 27 and detonates the initiators.
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Figure 19 illustrates a typical current pulse generated by the current pulse
generator of figure 18.
Figure 20 illustrates a second embodiment of a current pulse generator.
Figure 21 illustrates a third embodiment of a prior art current pulse
generator including a CMF current pulse generator having a capacitor
discharge input;
Figure 22 illustrates a fourth embodiment of a prior art current pulse
generator including a CMF generator having a piezoelectric ceramic input;
Figure 23 illustrates the fourth embodiment of the current pulse generator
of figure 22 which is connected to a plurality of parallel connected
initiators,
such as the exploding foil flying plate or bubble activated initiators or the
exploding bridgwire initiators, on the perforating gun of figures 11 and 12.
Figures 24-27 illustrate another embodiment of the present invention
including a sheet of initiators which has a width, where, instead of using the
flat cable conductor of figures 12, 13, and 15, the sheet of initiators is
wrapped around the entire circumference of the perforating gun of figure 12
until the width of the sheet is approximately equal to the circumference of
the perforating gun.
Figure 28 illustrates a section of figure 27 taken along section lines 21-21
of
figure 27.
Figure 29 iIlustrates a perforating apparatus including a first perforating
gun, a second perforating gun, and a detonation transfer unit in accordance
with another aspect of the present invention disposed between the first
perforating gun and the second perforating gun for transferring a
detonation wave from a first detonating cord of the first perforating gun to a
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second detonating cord of the second perforating gun of the perforating
apparatus.
Figure 30 illustrates a more detailed construction of the detonation transfer
unit of figure 29.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to figure 1, a perforating gun 10 is shown disposed in a wellbore
12. The perforating gun 10 includes a perforating gun carrier 14 in which a
loading tube 16 is disposed. The loading tube 16 includes a plurality of
phased mating holes, and a plurality of shaped charges 18 corresponding,
respectively, with the plurality of phased mating holes. A conducting
medium 20 is connected to the plurality of shaped charges 18, the
conducting medium 20 conducting an energy package to each shaped charge
for detonating the plurality of shaped charges 18. The conducting medium
may be an electrical current carrying conductor adapted for conducting
an electrical current pulse, or it may be a detonating cord adapted for
conducting a detonation wave.
Normally, the conducting medium 20 is a detonating cord and the energy
package is a detonation wave, the detonating cord conducting the detonation
wave to each shaped charge and the shaped charges detonating in response
to the detonation wave. When the shaped charges detonate, a jet is
produced from each charge. Since the conducting medium 20 in this case is
a detonating cord, each shaped charge 18 must include a special initiator
consisting of an explosive which responds to the detonation wave by
producing the jet from each shaped charge 18.
However, it would be desirable to use a new conducting medium 20 for
conducting a new energy package to the plurality of shaped charges 18. In
that case, since the new energy package is conducting in the conducting
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medium 20, a new initiator must be used with each of the plurality of
shaped charges. The new initiator responds to the new energy package
conducting in the conducting medium by producing the jet from the shaped
charges 18. The new conducting medium, the new energy package
conducting in the new conducting medium 20, and the new initiator
disposed within each shaped charge 18 is discussed below with reference to
figures 2-31 of the drawings.
Referring to figures 2-9, an electrical current carrying conductor 20-1 is
shown connected to the plurality of shaped charges 18 of a perforating
apparatus 10. A plurality of exploding foil flying plate or bubble activated
initiators (EFI initiators) 20a are mounted on the current carrying
conductor 20-1. Exploding bridgewire initiators could also be used. The
plurality of EFI initiators 20a are disposed in physical contact with an apex
of the respective plurality of shaped charges 18 in accordance with the
present invention.
In figure 2, the perforating gun 10 of figure 1 is again shown including the
plurality of shaped charges 18 connected to the conducting medium 20
which, in this case, comprises an ordinary electrical current carrying
conducting wire 20-1. The current conducting wire 20-1 of figure 2 is
physically attached to the inside of the perforating gun carrier 14, and each
of the plurality of shaped charges 18 is electrically connected to the current
conducting wire 20-1. As will be shown in detail in figures 3-9, a plurality
of
exploding foil or exploding bridgewire initiators 20a are mounted on the
conducting wire 20-1 and are disposed in contact with an apex of their
respective plurality of shaped charges 18. The electrical initiators 20a are
responsive to an ordinary electrical current conducting within the
conducting wire 20-1 for producing a jet from each of the shaped charges 18.
The electrical initiators 20a of figure 2 are known as an exploding foil
initiators (EFI initiators) 20a. There are three types of exploding foil
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78543-71
initiators: an exploding foil 'flying plate' initiator, an exploding foil
'bubble
activated' initiator, and an exploding bridge wire initiator. As shown in
figures 3-9, an exploding foil flying plate initiator 20a, or an exploding
foil
bubble activated initiator 20a, or an exploding bridgewire initiator is
disposed between each shaped charge of the perforating apparatus and the
current carrying conductor 20-1.
In figure 3, the conducting medium 20 of figure. l comprises an electrical
current carrying conductor wire 20-1 for carrying an electrical current. A
plurality of barrels 19 are disposed, respectively, between the plurality of
shaped charges 18 and the current carrying conductor 20-1. As shown in
the following figures of drawing, the current carrying conductor wire 20-1
includes a first copper foil having a plurality of EFI initiators 20a, a
second
copper foil connected to ground potential, and a plurality of polyimide
insulating layers.
In figure 4, the current carrying conductor wire 20-1 includes a first copper
foil 20-1(a), having a plurality of EFI initiators 20a disposed thereon,
located between a first polyimide layer 20b and a second polyimide layer
20c. A second copper foil 20d is disposed between the second polyimide
layer 20c and a third polyimide layer 20e. The polyimide layers 20b, 20c,
and 20e are approximately 0.025 inches in thickness. One type of polyimide
material, which may be used as the polyimide layers 20b, 20c, and 20e, is
known as "Kapton". Kapton is a registered trademark of E.I. Dupont De Nemours,
Incorporated. The Kapton polyimide material is manufactured by E.I.
Dupont De Nemours, Incorporated (Dupont). The first copper foil 20-1(a)
functions as a current carrying conductor for carrying electrical current to
each of the plurality of EFI initiators 20a and ultimately to each of the
plurality of charges 18. The second copper foil 20d functioning as a return
path for the current to ground potential.
In figure 5, a section of the current carrying conductor 20-1 of figure 4,
taken along section lines 5-5 of figure 4, is illustrated. In figure 5, the
first
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-78543-71
copper fail 20-1(a) is shown disposed over the second polyimide layer 20c.
The first copper foi120-1(a) includes a plurality of EFI initiators 20a spaced
apart along the surface of the first copper foil, and each EFI initiator 20a
on
the first copper foil 20-1(a) includes a first part 20a2, a bridge 20a1, and a
second part 20a3. If the width of the copper foil 20a is "W", each bridge
20a1 has a width "w", where the width "w" is much less than the width W.
As a result, in response to a current "I" of sufficient magnitude and duration
flowing through the bridges 20a1, the bridges 20a1 will vaporize, creating
an open circuit and producing a plasma gas directly above each bridge. The
second copper foi120d does not include any such bridges 20a1, the width of
the second copper foil 20d being of constant width W.
Referring to figures 6 and 7, a 'flying plate' type of exploding foil
initiator
20a is used with each of the shaped charges 18 of the perforating gun of
figure 2. In figure 6, one of the barrels 19 is shown disposed between one of
the shaped charges 18 and the current carrying conductor 20-1 (which
embodies the flying plate initiator 20a) of the perforating gun of figure 2.
In figures 6 and 7, a flying plate 20b1 in figure 6 is shown "flying" within a
hole 19a in the barrel 19. The hole 19a of barrel 19 is disposed directly
above the bridge 20a1 of figure 7 of the first copper foi120-1(a). The flying
plate 20b1 is actually a part of the $rst polyimide layer 20b, the flying
plate
20b 1 being a disc which was sheared off from the first polyimide layer 20b
when a current "I" of sufficient magnitude flowed through the EFI initiator
20a of the first copper foi120-1(a) of figure 7 and vaporized the bridge 20a1
of the EFI initiator 20a of the first copper foi120a producing the plasma gas.
A flying plate detonator is shown and discussed in U.S. Patent 4,788,913 to
Stroud et al, entitled "Flying Plate Detonator using a High Density High
Explosive".
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CA 02599056 2007-09-11
A functional description of the operation of a shaped charge 18 of the
perforating gun of figure 2 including an exploding foil flying plate initiator
for use in connection with the shaped charge 18 of the perforating gun is set
forth in the following pargraphs with reference to figures 6 and 7 of the
drawings.
In figure 6, assume a current "I" is flowing in the first copper foil 20-1(a).
The current "I" is not a transient current, but is a direct current of
sufficient
time duration and magnitude to vaporize, approximately simultaneously, all
of the bridges 20a1 of the EFI initiator 20a of the first copper foil 20-1(a)
of
figure 5. When the plurality of bridges 20a1 associated with each of the
plurality of EFI initiators 20a vaporize, a corresponding plurality of high
pressure plasma gas is produced. This plurality of high pressure gas
associated with the plurality of bridges 20a1 produces a corresponding
plurality of turbulence areas, and the plurality of turbulence areas are
disposed directly under a plurality of portions of the first polyimide layer
20b. The plurality of portions of the first polyimide layer 20b are, in turn,
disposed directly under the plurality of holes 19a associated with a
respective plurality of barrels 19. As a result of these turbulence areas, a
plurality of discs (the flying plate 20b1) are sheared off from the first
polyimide layer 20b, the discs being forced to fly within the holes 19a of
barrels 19. Therefore, in figure 6, the "flying plate" 20b1 is shown flying
within hole 19a of barrel 19. The shaped charges 18 each include a
secondary explosive pellet 18a, the pellet 18a being an HE pellet.
Eventually, the flying plate 20b1 will impact the secondary explosive (HE
pellet) portion 18a of the shaped charge 18. When this occurs, the secondary
explosive pellet 18a detonates thereby detonating the shaped charge 18 and
forming a jet which projects from the shaped charge and perforates a
formation traversed by the wellbore, as shown in figure 1. As shown in
figure 7, when the bridge 20a1 of the EFI initiator 20a of the first copper
foil
20-1(a) vaporizes, an open c:ircuit condition occurs. As a result, a first
part
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78543-71 D
of first copper foi120a2 is physically and electrically disconnected from a
second part of the first copper foil 20a3.
Referring to figures 8 and 9, a 'bubble activated' type of exploding foil
initiator is used with each of the shaped charges 18 of the perforating gun of
figure 2. In figure 8, one of the barrels 19 is disposed between one of the
shaped charges 18 and the current carrying conductor 20-1 (which embodies
the exploding foil 'bubble activated' initiator 20a) of the perforating gun of
figure 2.
In figure 8, a bubble 20b2 is shown expanding within a hole 19a in the
barre119. The hole 19a of barrel 19 is disposed directly above the bridge
20a1 of the first copper foi120-1(a). The bubble 20b2 is actually a part of
the first polyimide layer 20b, the bubble 20b2 forming from the first
polyimide layer 20b when a current "I" of sufficient magnitude flows
through the EFI initiator 20a of the first copper foi120-1(a) and vaporizes
the bridge 20a1 of the EFI initiator 20a of the first copper foi120-1(a). The
bubble activated initiator is discussed in detail in U.S. Patent 5,088,413 to
Huber et al, entitled "Method and Apparatus for Safe Transport Handling
Arming and Firing of Perforating Guns using a Bubble Activiated
Detonator"
A functional description of the operation of the shaped charge 18 of the
perforating gun of figure 2 including an exploding foil bubble activated
initiator for use in connection with the shaped charge 18 of the perforating
gun is set forth in the following pargraphs with reference to figures 8 and 9
of the drawings.
In figures 8 and 9, assume a current "I" is flowing in the first copper foil
20-
1(a). The current "I" is not a transient current, but is a direct current of
sufricient time duration and magnitude to vaporize, approximately
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CA 02599056 2007-09-11
simultaneously, all of the bridges 20a1 of the EFI initiators 20a on the first
copper foi120-1(a) of figure 5. When one of the bridges 20a1 vaporize, a
plasma gas is produced, the plasma gas producing a turbulence directly
under that portion of the first polyimide layer 20b which is disposed directly
under the hole 19a of the barrel 19. As a result of this turbulence, a bubble
20b2 is formed from the first polyimide layer 20b, the shape and size of the
bubble 20b2 being controlled by the shape and size of the hole 19a of barrel
19. Therefore, in figure 8, the bubble 20b2 is shown expanding within hole
19a of barre119. The shaped charges 18 each include a secondary explosive
(HE pellet) portion 18a. Eventually, the bubble 20b2 wiIl impact the
secondary explosive pellet 18a of the shaped charge 18. When this occurs,
the secondary explosive pellet 18a detonates thereby detonating the shaped
charge 18 and forming a jet which projects from the shaped charge and
perforates a formation traversed by the wellbore, as shown in figure 1. As
shown in figure 9, when the bridges 20a1 of the EFI initiators 20a of the
first copper foil 20-1(a) vaporize, an open circuit condition occurs with each
bridge 20a1. As a result, as shown in figure 9, since each of the bridges
20a1 of the EFI initiators 20a are now open circuited, a first part 20a2 of
the EFI initiators 20a of the first copper foil is physically and electrically
disconnected from a second part 20a3 of the EFI initiator 20a of the first
copper foiL
As a result, when the conducting medium 20 of figure 1 is an electrical
current carrying conductor, such as the current carrying conductor wire 20-1
of figure 4, and when an exploding foil flying plate or bubble activated
initiator of the type described above with reference to figures 3-9 is used to
detonate the shaped charges 18, and when a current of sufficient magnitude
and time duration flows in the first copper foil 20-1(a) of conductor 20-1,
the
exploding foil flying plate or bubble activated initiators 20a will
simultaneously detonate, and the simultaneous detonation of the EFI
initiators 20a will, in turn, simultaneously detonate all of the shaped
charges 18 of the perforating gun 10 of figures 1 and 2.
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CA 02599056 2007-09-11
Referring to figure 10, a conventional perforating gun is illustrated. The
conventional perforating gun includes a plurality of shaped charges 30
connected to a detonating cord 32. A detonator 34 initiates the propagation
of a detonation wave in the detonating cord 32 in response to a current
propagating in the electrical conductor 36. The detonation wave detonates
the shaped charges thereby producing a jet 38 from each of the shaped
charges 30.
Referring to figure 11, a new perforating gun in accordance with the present
invention, similar to the new perforating gun of figure. 2, is illustrated.
The
new perforating gun of figure 11 includes a plurality of shaped charges 40
connected to an electrical current carrying conductor 42. As will be
discussed later in this specification, the conductor 42 includes a plurality
of
initiators 20a, such as an exploding foil flying plate initiator 20a of
figures
6-7 or an exploding foil bubble activated initiator 20a of figures 8-9 or an
exploding bridgewire initiator. The plurality of initiators 20a on the
conductor 42 are disposed, respectively, adjacent to the plurality of shaped
charges 40 for simultaneously detonating all of the charges in response to a
simultaneous detonation of the plurality of initiators 20a. The conductor 42
is electrically connected to a current pulse generator 44. As will be noted
later in this specification, the current pulse generator 44 can be either a
charging capacitor circuit, or a parallel-connected charging capacitor
circuit,
or a compressed magnetic flux (CMF) current pulse generator.
Referring to figure 12, a preferred embodiment of the new perforating gun of
figure 11 in accordance with the present invention is illustrated.
In figure 12, a first plurality of phased shaped charges 40a are disposed on
one side of the new perforating gun. A first electrical current carrying flat
cable conductor 42a (hereinafter, the "flat cable conductor 42a") is helically
wrapped around the plurality of shaped charges 40a. The flat cable
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CA 02599056 2007-09-11
conductor 42a is shown to be wrapped around the plurality of shaped
charges 40a within the interior of the loading tube 45 of the new perforating
gun of figure 12, although the flat cable conductor 42a could just as easily
be
wrapped around the plurality of shaped charges 40a and around the exterior
of the loading tube 45 of the new perforating gun of figure 12. The flat cable
conductor 42a contacts the apex of each of the first plurality of shaped
charges 40a. The flat cable conductor 42a is approximately 1.25 inches in
width. The flat cable conductor 42a is a flat electrical current carrying
conductor and it includes a plurality of initiators 20a spaced apart at
periodic intervals along the length of the flat cable conductor 42a. When the
flat cable conductor 42a is wrapped around the plurality of shaped charges
40a, the plurality of initiators 20a on the flat cable conductor 42a abut,
respectively, against the apex of the first plurality of shaped charges 40a.
The flat cable conductor 42a is electrically connected to a first current
pulse
generator 44a for generating a pulse of current which approximately
simultaneously detonates the plurality of initiators 20a on the flat cable
conductor 42a. The first current pulse generator 44a is actually a
compressed magnetic flux (CMF) current pulse generator 44a (hereinafter
called the "first CMF current pulse generator 44a"). The first CMF current
pulse generator 44a receives a detonation wave from a detonator 48 and
generates a current pulse in response to the detonation wave. The
detonator 48 can be any typical detonator, such as a percussion detonator,
an electric detonator, or an exploding foil initiator detonator, or an
exploding bridgewire initiator detonator.
However, in addition, a second plurality of phased shaped charges 40b are
disposed on the other side of the new perforating gun of figure 12. A second
electrical current carrying flat cable conductor 42b (hereinafter, the flat
cable conductor 42b) is helically wrapped around the plurality of charges
40b and within the interior of the loading tube 45 on the other side of the
new perforating gun of figure 12, although the flat cable conductor 42b could
just as easily be wrapped around the plurality of charges 40b and around
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CA 02599056 2007-09-11
78543-71
the exterior of the loading tube 45. The flat cable conductor 42b contacts
the apex of each of the second plurality of shaped charges 40b. The flat
cable conductor 42b is a flat electrical current carrying conductor. As a
result, the flat cable conductor 42b also includes a plurality of initiators
20a
spaced at periodic intervals along the length of the flat cable conductor 42b.
The initiators 20a can be the flying plate initiator, the bubble activated
initiator, or the exploding bridgewire initiator. When the flat cable
conductor 42b is wrapped around the plurality of shaped charges 40b, the
plurality of initiators 20a on the flat cable conductor 42b abut,
respectively,
against the apex of the second plurality of shaped charges 40b. The flat
cable conductor 42b is electrically connected to a second current pulse
generator 44b which is actually a second compressed magnetic flux (CMF)
current pulse generator 44b.
The first and second CMF current pulse generator 44a and 44b are each
described in an article entitled "Small Helical Flux Compression
Amplifiers", by J.E. Gover, O.M. Stuetzer, and J.L. Johnson, of Sandia
Laboratories, Albuquerque, New Mexico, printed in Megagauss Physics and
Technology, 1979.
An intermediate adaptor 46 separates the one side of the new perforating
gun from the other side and functions to convert an electrical current pulse
in the end of the first cable 42a into a detonation wave which initiates the
generation of a current pulse from the second CMF current pulse generator
44b. The intermediate adaptor 46 includes an EFI firing head 46c
connected to the end of the first flat cable conductor 42a. The EFI firing
head 46c is identical to the EFI firing head 124 which is discussed below
with reference to figure 23 of the drawings. The EFI firing head 46c
functions to receive the current pulse propagating in the end of the first
flat
cable conductor 42a and to detonate an explosive pellet disposed within the
firing head 46c. The intermediate adaptor 46 fzu-ther includes a first
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CA 02599056 2007-09-11
detonating cord 46a connected to the EFI firing head 46c and responsive to
the detonation of the explosive pellet in the EFI firing head 46c for
initiating the propagation of a detonation wave in the first detonating cord,
and a second detonating cord 46b disposed in side-by-side abutment with
the first detonating cord 46a. In operation, when the current pulse
propagating in the end of the first flat cable conductor 42a energizies the
EFI firing head 46c, an explosive pellet in the firing head 46c detonates,
which, in turn, initiates the propagation of a detonation wave in the first
detonating cord 46a. Since the second detonating cord 46b is disposed in
side-by-side abutment with the first detonating cord 46a, the detonation
wave in the first detonating cord 46a transfers to the second detonating cord
46b. Therefore, a detonation wave now propagates in the second detonating
cord 46b, and this detonation wave energizes the second CMF generator
44b. As a result, the second CMF generator 44b generates a second current
pulse in response thereto.
A functional description of the operation of the new perforating gun of figure
12 will be set forth in the following paragraph with reference to figure 12 of
the drawings.
The first CMF current pulse generator 44a receives a detonation wave from
the detonator 48 and generates a current pulse in response therto. The
current pulse propagates through the flat cable conductor 42a thereby
detonating, approximately simultaneously, all of the initiators 20a disposed
on the flat cable conductor 42a. Since the initiators 20a on the flat cable
42a abut, respectively, against the first plurality of shaped charges 40a,
when the initiators on the flat cable conductor 42a simultaneously detonate,
the first plurality of shaped charges 40a also detonate approximately
simultaneously. The intermediate adaptor 46 converts the current pulse in
the flat cable conducotr 42a into a second detonation wave. As a result, in
response to the second detonation wave, the second CMF current pulse
generator 44b generates a second current pulse. The second current pulse
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CA 02599056 2007-09-11
propagates through the flat cable conductor 42b thereby detonating,
approximately simultaneously, all of the initiators disposed on the flat cable
conductor 42b. Since the initiators on the flat cable conductor 42b abut,
respectively, against the apex of the second plurality of shaped charges 40b,
when the initiators on the flat cable conductor 42b detonate simultaneously,
the second plurality of shaped charges 40b also detonate approximately
simultaneously.
Referring to figures 13-16, a detailed construction of the first electrical
current carrying flat cable conductor 42a and the second electrical current
carrying flat cable conductor 42b of figure 12 is illustrated.
Since the first and second flat cable conductors 42a and 42b are flat, ribbon
like cables, they each have two sides, an external side which does not abut
the apex of a shaped charge and an internal side which does abut the apex
of the shaped charge. In accordance with a preferred embodiment of the
present invention, a plurality of exploding foil (flying plate, or bubble
activated, or exploding bridgewire) initiators 20a, similar to the EFI
initiators 20a on the first copper foil 20-1(a) shown in figures 4 and 5, are
disposed on the internal side of the flat cables 42a and 42b, and they are
spaced apart at periodic intervals along the internal side of the cable 42a
and 42b. The external side of the flat cables 42a and 42b is shown in figure
13 and the internal side of the flat cables 42a and 42b is shown in figure 14.
In figure 13, a view of a portion of the external side of the first and second
flat cable conductors 42a and 42b of figure 12 is illustrated. Since the
external side of the flat cables face externally, the external side does not
abut against the apex of any shaped charge 40 of figure 12. In figure 13, the
external side of the flat cable conductors 42a and 42b includes a plurality of
external initiator terminals 42a1. Since, in the preferred embodiment, an
exploding foil (flying plate or bubble activated or exploding bridgewire)
initiator (EFI) is the preferred type of initiator, hereinafter, each of the
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CA 02599056 2007-09-11
plurality of initiator terminals 42a1 will be referred to as "external EFI
terminals 42a1". Each external EFI terminal 42a1 includes a pair of EFI
attach holes 42a1(a), an EFI alignment hole 42a1(b), a charge jacket
attachment hole 42a1(c), a ground relief 42a1(d), and a high voltage relief
42a1(e). In order to fully understand the construction of the "external" EFI
terminal 42a1, it is necessary to understand the construction of the
"internal" side of the flat cable conductors 42a and 42b of figure 12.
Accordingly, refer to the figure 14 description below.
Referring to figure 14, a view of a portion of the internal side of the first
and
second flat cable conductors 42a and 42b of figure 12 is illustrated. Since
the flat cable conductors 42a and 42b of figure 12 each include a plurality of
exploding foil initiators 20a, in figure 14, the construction of a single
exploding foil initiator (EFI initiator) 20a (similar to the EFI initiator 20a
of
figure 5 which includes the the first part 20a2, the bridge 20a1, and the
second part 20a3) is illustrated.
Figure 14 actuaIly illustrates a view of the external EFI terminal 42a1 of
figure 13 from the "internal" side of the first and second flat cable
conductors 42a and 42b. Recall from the above description in connection
with figures 6 and 7 that a flying plate 20b1 is sheared out from a first
polyimide layer 20b when a bridge 20a1 of the EFI initiator 20a on a first
copper foi120-1(a) vaporizes in response to a current flowing from the first
part 20a2 of the first copper foil 20-1(a), through the narrow bridge 20a1 of
width "w", to the second part 20a3 of the first copper foil.
In figure 14, each of the exploding foil initiators 20a, disposed on the
"interaal" side of the first and second flat electrical current carrying cable
conductors 42a and 42b of figure 12, includes a first part 20a2 (see figure 7)
which is connected to one of the EFI attach holes 42a1(a) of figure 13 and a
second part 20a3 which is connected to the other of the EFI attach holes
42a1(a) of figure 13. A bridge 20a1(similar to bridge 20a1 of figure 7) is the
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CA 02599056 2007-09-11
narrow portion of the EFI initiator 20a which is electrically connected
between the first part 20a2 of the EFI initiator 20a and the second part
20a3 of the EFI initiator 20a.
Referring to figure 15, a view of the internal side of the first and second
flat
conductor cables 42a and 42b of figure 12 is illustrated.
Figure 15 actually represents a view of the entire electrical current path
which is disposed on the internal side of the first and second flat conductor
cables 42a and 42b of figure 12 and which includes all of the parallel
connected exploding foil (flying plate or bubble activated or exploding
bridgewire) initiators.
Recall from the above description in connection with figures 6-9 that an EFI
initiator 20a is comprised of at least two layers: a first copper foil 20-1(a)
for
conducting a current, and a second copper foi120d which functions to
provide a return path for the current to ground potential. The first copper
foi120-1(a) of figure 6 conducts a current pulse through the bridge 20a1 of
the EFI initiator 20a on the first copper foil 20-1(a), the bridge 20a1
separating the first part 20a2 of the first copper foil 20-1(a) 20a2 from the
second part 20a3 of the first copper foiL Recall also that the second copper
foil 20d functions as a ground potential providing a return path for the
current flowing in the first copper foil 20-1(a).
In figure 15, an electrical current path associated with a plurality of
parallel
connected EFI initiators 20a disposed on the internal side of the flat cable
conductors 42a and 42b is denoted by the element numeral 54. An electrical
current path associated with the return path to ground potential is denoted
by the element numeral 56. The electrical current path 54, including a
plurality of parallel connected EFI initiators 20a, is connected to a voltage
supply 50 via a spark gap switch 52. Note that the electrical current path
54 includes a first plurality of parallel connected exploding foil initiators
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20a4 which receive a current from the voltage supply 50, a second plurality
of parallel connected exploding foil initiators 20a5, a third plurality of
parallel connected exploding foil initiators 20a6, and a fourth plurality of
parallel connected exploding foil initiators 20a7. The first, second, third,
and fourth plurality of exploding foil initiators.20a4-20a7 in figure 15 are
each identical to the exploding foil initiator 20a shown in figure 14 of the
drawings. As noted by the direction of the arrows in figure 15, the current
from the voltage supply 50 flows through the electrical current path 54 as
follows: in a first direction through the first plurality of initiators 20a4,
then
in a second direction opposite to the first direction through the second
plurality of initiators 20a5, then in a third direction opposite to the second
direction in the third plurality of initiators 20a6, and then in a fourth
direction opposite to the third direction in the fourth plurality of
initiators
20a7. The current from the fourth plurality of iniitators 20a7 flows back to
the voltage supply 50 via the return electrical current path 56 in figure 15.
As a result, the first, second, third, and fourth plurality of exploding foil
initiators 20a4, 20a5, 20a6, and 20a7 in figure 15 all detonate substantially
simultaneously in response to the current pulse originating from the voltage
supply 50 and flowing through all of the initiators.
Referring to figure 16, a cross sectional view of the flat cable conductors
42a
and 42b, including all of the individual layers of the first and second flat
cables 42a and 42b of figure 12, is illustrated.
In figure 16, the flat cable conductors 42a and 42b of figures 12, 13 and 15
each include: a two (2) Mil Kapton layer 42a2; an adhesive layer 42a3; a two
(2) ounce copper layer 42a4 which conducts a current to the first copper foil
20-1(a) of figures 6-9; a two (2) mil Kapton layer 42a5 which includes the
second polyimide layer 20c of figures 6-9; a two (2) ounce copper layer 42a6
which includes the second copper foil 20d return current path of figures 6
and 8; an adhesive layer 42a7; a two (2) mil Kapton layer 42a8 which
includes the third polyimide layer 20e of figures 6 and 8; and a one (1) mil
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copper "EFI layer" 20a, disposed on top of the two mil Kapton layer 42a2,
which is the EFI layer shown in figure 14 of the drawings and which
includes the first part 20a2, the bridge 20a1, and the second part 20a3 of the
first copper foi120-1(a) shown in figures 7 and 9 of the drawings. As shown
in figure 6, a plate 20b1 is sheared o$'from the. first polyimide layer 20b in
response to the current (I) flowing in the bridge 20a1 of the EFI layer 20a
and the plate 20b1 flies through the hole 19a in the barrel 19 eventually
impacting a secondary explosive pellet 40a1 of the shaped charges 40a/40b
shown in figure 17 of the drawings.
Referring to figure 17, a cross sectional view of the shaped charges 40a and
40b shown in figure 12 is illustrated.
The shaped charges 40a and 40b each include a metal liner 40a3, a metal
case 40a4, a main body of high explosive 40a2 disposed between the metal
liner 40a3 and the metal case 40a4, and a secondary explosive pellet 40a1
disposed in the apex of each shaped charge. The apex of each shaped charge
is adapted to abut against the hole 19a of the barrel 19 of an EFI initiator
20a, as shown in figure 16, in a manner which guarantees that the hole 19a
of the barrel 19 is disposed directly above and in direct alignment with the
secondary explosive pellet 40a1 of the shaped charge 40a or 40b.
In accordance with another aspect of the present invention, the secondary
explosive pellet 40a1 of the shaped charge 40a and 40b of figure 17 must be
comprised of a special explosive composition which wiIl detonate when the
flying plate 20b1 of figure 6 impacts the pellet 40a1, or when the expanding
bubble 20b2 of figure 8 impacts the pellet 40a1, or when a detonation wave
in a detonating cord impacts the pellet 40a1. After extensive
experimentation, it has been discovered that the special explosive
composition of the secondary explosive pellet 40a1 must be selected from a
group consisting o HNS-IV, NONA, HMX, RDX, PETN, TATB, ABH, BTX,
DPO, DODECA, Tripicryl-trinitrobenzene, barium styphnate, and metallic
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picrate salts. At low temperatures, for best performance, the secondary
explosive pellet 40a1 should be selected from the following group: PETN,
RDX, and HMX; however, at high temperatures, for best performance, the
secondary explosive pellet 40a1 should be selected from the following group:
ABH, BTX, DPO, NONA, DODECA, Tripicryl-trinitrobenzene, barium
styphnate, and metallic picrate salts. However, the main body of explosive
40a2 can be selected from the following group: RDX, HMX, or HNS. One of
the special explosive compositions disclosed in the above group will work in
connection with some type of exploding foil initiator, or in connection with a
semiconductor bridge initiator (of the type disclosed in U.S. Patent
5,094,167 to Hendley Jr.), or in connection with some type of an exploding
bridgewire initiator.
In the normal construction of a shaped charge, all explosives are pressed
under a common load so that initiation sensitivity is not controlled
independently from charge performance (higher pressing forces tend to
desensitize the charge and cause misfires).
In accordance with still another aspect of the present invention, during
manufacture of the shaped charge 40a and 40b of figure 17, the main body
of explosive 40a2 is pressed independently of the pressing of the secondary
explosive pellet 40a1. The main body of explosive 40a2 is pressed to a
separate "high" density, but the secondary explosive pellet 40a1 is pressed
to a separate "low" density. The "high" density of the main body of explosive
40a2 may be defined as that density which is above ninety percent (90 !0) of
the theoretical maximum crystal density. The optimal "low" density of the
"HNS IV" secondary explosive pellet 40a1, for example, would be 1.57
grams/cc. Recall that initiation of the pellet 40a1 must occur in response to
detonation of either an EFI initiator 20a or a detonating cord. Pressing the
pellet 40a1 to a separate low density relative to that of the main body of
explosive 40a2 optimizes the initiation sensitivity of the secondary explosive
pellet 40a1. The aforementioned optimized initiation sensitivity of the
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pellet 40a1 is required since the pellet must be initiated by detonation of
either the EFI initiator 20a (which includes the Exploding Bridge Wire) or
the detonating cord.
Referring to figures 18-23, various embodiments of the current pulse
generator 44 of figure 11 are illustrated.
In figures 18 and 19, a first embodiment of the current pulse generator 44 of
figure 11 is illustrated. The current pulse generator 44 can comprise a
conventional charging capacitor and discharge swith arrangement. For
example in figure 18, a high voltage source 60 is connected to a charging
capacitor 62 via a charging resistor 64. The charging capacitor 62 is
connected to a discharge switch 66. The voltage source 60 charges the
capacitor 62. When the capacitor 62 is completely charged, the discharge
switch 66 changes from a open circuit to a short circuit condition allowing a
discharge current pulse stored in the form of a charge in the capacitor 62 to
discharge through the short circuited discharge switch 66. The discharge
current pulse (also known as an injection current) energizes the flat cable
conductor 42 in figure 11 and flat cable 42a in figure 12.
Figure 19 illustrates the exact nature of this discharge current pulse from
the capacitor 62.
In figure 20, a second embodiment of the current pulse generator 44 of
figure 11 is illustrated.
In figure 20, the current pulse generator 44 could comprise a high voltage
source 70 connected to a first charging resistor 72, a second charging
resistor 74, a third charging resistor 76 and a fourth charging resistor 78.
The first charging resistor 72 is connected to a first charging capacitor 80,
and the first charging capacitor 80 is connected to a charge bank (1) 84 via a
discharge switch 82. The charge bank (1) 84 comprises a first plurality of
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the shaped charges 40 of figure 11 of the perforating apparatus. The second
charging resistor 74 is connected to a second charging capacitor 86, and the
second charging capacitor 86 is connected to a charge bank (2) 88 via an
explosive ionization gap 90. The charge bank (2) 88 comprises a second
plurality of the shaped charges 40 of the perforating apparatus of figure 11.
The third charging resistor 76 is connected to a third charging capacitor 92,
and the third charging capacitor 92 is connected to a charge bank (3).94 via
an explosive ionization gap 96. The charge bank (3) 94 comprises a third
plurality of the shaped charges 40 of the perforating apparatus of figure 11.
The fourth charging resistor 78 is connected to a fourth charging capacitor
98, and the fourth charging capacitor 98 is connected to a charge bank (4)
100 via an explosive ionization gap 102. The charge bank (4) 100 comprises
a fourth plurality of the shaped charges 40 of the perforating apparatus of
figure 11. The charging capacitors are sized for about 0.3 uf times the
number of charges it will fire. These capacitors are charged to a voltage of
about 2 to 5 kV depending upon the length of the line and whether it will
fire an EFI or an EBW initiator. In operation, the voltage source 70 charges
the first charging capacitor 80. When the discharge switch closes it's circuit
in response to the charge on the capacitor 80, a first discharge current flows
from capacitor 80 to the charge bank (1) 84 thereby simultaneously
detonating the first plurality of shaped charges. In the meantime, the
voltage source 70 has already fully charged the other remaining charging
capacitors, that is, the second, third, and fourth charging capacitors 86, 92,
and 98. When the last charge of said first plurality of shaped charges of
charge bank (1) 84 has detonated, the explosive ionization gap 90 allows a
second discharge current to flow from the second charging capacitor 86 to
the charge bank (2) 88 thereby simultaneously detonating the second
plurality of shaped charges. When the last charge of said second plurality of
shaped charges of charge bank (2) 88 has detonated, the explosive ionization
gap 96 allows a third discharge current to flow from the third charging
capacitor 92 to the charge bank (3) 94 thereby simultaneously detonating
the third plurality of shaped charges. When the last charge of said third
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78543-71
plurality of shaped charges of charge bank (3) 94 has detonated, the
e-plosive ionization gap 102 allows a fourth discharge current to flow from
the fourth charging capacitor 98 to the charge bank (4) 100 thereby
simultaneously detonating the fourth plurality of shaped charges.
In figure 21, a third embodiment of the current pulse generator 44 of figure
11 is illustrated.
In figure 21, the current pulse generator 44 could comprise a compressed
magnetic flux (CMF) current pulse generator. The CMF generator is
described in an article entitled "Small Helical Flux Compression Amplifiers"
by J.E. Gover, O.M. Stuetzer, and J.L. Johnson, Sandia Laboratories,
.Albuquerque, New Mexico, printed in "Megagauss Physics and Technology",
1979. The CMF generator is also described in an article entitled
"The Cent-al Power Supply", Showcase for Technology, conference and
e position, 198? _ The CIV;F ;-n--rent pulse generator of figure 21 includes a
source of injection or seed current 110, such as a capacztor discharge system
wh1Ch duffiDs energy from a capacitor into the inductance coil 114. The
injection current source 110 is connected to a crow bar switch 112. The crow
bar switch 112 is further connected to an inductance coil 114. An armature
116 os disnosed within the center of the inductance coi1114. The armature
116 includes an explosive 116a which is detonated in response to a
detonation wave from a detonating cord or a detonator. The last turn of the
inductance coil 114 is connected to a load 118, such as the flat cable
Z5 conductor 42a or the flat cable conductor 42b in figure 12 of the drawings.
Recalling that the flat cable conductors 42a and 42b of figure 12 each
include a plurality of the exploding foil (flying plate or bubble activated)
initiators 20a shown in figure 14 of the drawings, the load 118 of figure 21
comprises a plurality of the exploding foil initiators 20a shown in figure 14.
In operation, a current from the injection current source 110 is injected into
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the inductance coi1114. When the current in the coil 114 is near maximum,
the explosive filled armature 116 is detonated from one end (e.g., from a
detonating cord). The armature 116 begins to expand from one end (the left
hand end in figure 21). As the armature 116 expands, the crow bar switch
112 is shorted out, and the coils of the inductance coil 114 are shorted out
in
sequence. Recall that, when the individual coils of the inductance coil 114
short out, since the magnetic field generated by the inductance coil 114
must remain constant, the current in the remaining coils of the inductance
coi1114, which are not shorted out, must increase in amplitude thereby
producing a pulse of current having an increasingly greater amplitude.
Therefore, the current in the remaining coils of the inductance coi1114
increases in amplitude until it reaches a maximum in the last remaining
coil of the inductance coi1114 which has not yet been shorted out by the
expanding armature 116. The current in the last remaining coil of
inductance coi1114 is typically 50 to 100 times the injection current from
the injection current source 110. Thus, by selecting the correct number of
turns of the inductance coil 114 and the injection current from injection
current source 110, a sufficient output current can be obtained from the
CMF current pulse generator 44 of figure 21 to fire several hundred
initiators (EFI or EBW initiators) associated with several hundred shaped
charges 40a or 40b of the perforating gun of figure 12.
In figure 22, a fourth embodiment of the current pulse generator 44 of figure
11 is illustrated.
Figure 22 illustrates another embodiment of the compressed magnetic flux
(CMF) current pulse generator shown in figure 21. However, in figure 22,
instead of using the separate source of injection or seed current 110 shown
in figure 21, a piezoelectric ceramic 120, configured for a high output
current and voltage, stores energy and therefore can be used as the source of
injection current The piezoelectric ceramic 120 encloses an armature 116
containing an explosive 116a, where the explosive 116a can be detonated by
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another exploding foil initiator, an exploding bridewire, or a standard
electric detonator. In addition, a percussion detonator or a trigger charge
booster activated by one of many available firing heads will detonate the
explosive 116a in the armature 116. A crow bar switch 112 is connected to
an inductance coil 114, the inductance coi1114 enclosing the armature. The
last turn of the inductance coi1114 is connected to a load 118, which can be
one of the plurality of exploding foil initiators 20a of figure 14 arranged on
a
flat conductor cable similar to flat cable 42a and 42b in figure 12. A certain
spacing is chosen between the piezoelectric ceramic 120 and the inductance
coil 114. This certain spacing must be used to allow the field in the coi1114
to build to near maAmum before sequential shorting of the coi1114
commences. The certain spacing distance corresponds to the detonation
velocity of the armature multiplied by the time required to charge the coil
114. The certain spacing distance is approximately 100 mm for a typical
system but would vary depending upon the coil 114 size, inductance of the
coil 114, and explosive type of the explosive.116a. In operation, the
explosive 116a in the armature 116 is detonated by the detonator 48 of
figure 12. Detonation of the explosive 116a produces an explosive shock in
the armature 116. The explosive shock from the armature 116 releases the
energy stored in the piezoelectric ceramic 120 and pumps the energy into
the inductance coil 114. In response to the release of the energy from the
piezoelectric ceramic 120, a current begins to flow from the ceramic 120 to
the inductance coi1114. However, the armature explosive 116a has been
detonated. As a result, the armature 116 expands in it's radial dimension,
the expansion propagating from the left hand side of the armature 116 in
figure 22 to the right hand side in figure 22. This propagating expansion of
the armature 116 shorts out the crow bar switch 112, and then begins to
short out each of the individual turns of the inductance coi1114, starting
with the first turn of the coil 114 on the left hand side of the figure 22 and
ending with the last turn on the right hand side of figure 22. Since the
magnetic field produced by the coi1114 must remain constant, since the
number of turns of the coi1114 which are not short circuited by the
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78543-71
expanding armature is decreasing, the current in the remaining coil turns
must increase to a maximum. When all turns of coil 114 are short circuited
except for the last turn, the current in the last turn 114a has reached it's
ma.ximum value. This current in the last turn 114a is used to energize the
load 118. As a result, all of the bridges 20a1 of all of the exploding foil
initiators 20a or exploding bridgewire initiators on the flat cable 42a and
42b of figure 12 are substantiaIly simultaneously vaporized.
Referring to figure 23, the CMF generator 44 of figure 22 is again shown in
figure 23. The output of the CMF generator 44 is shown connected to a
plurality of the exploding foil initiators 20a of figure 14, where a first
plurality of exploding foil initiators 20a is connected in parallel to a
second
plurality of such initiators 20a, the second plurality being connected in
parallel to a third plurality of such initiators 20a, and the third plurality
being connected in parallel to a fourth plurality of such initiators 20a. The
explosive 116a in the armature 116 is detonated by a detonation wave
propagating in a detonating cord 122. The detonating cord 122 has a
booster 122a which is detonated by a firing head 124. The firing head 124 is
discussed in U.S. Patent No. 5,347,929, filed
September 1, 19193, entitled "Fining System for a Perforating gun Including
an E ,ploding Foil Initiator and an Outer Housing for Conducting Wireline
Current and EFI Current", The functional operawon of
the CMF generator in figure 23 is the same as that which is described above
with reference to figure 22. However, the last turn 114a of the coil 114,
which is not short circuited by the expanding armature 116, has a
maximum pulse of current 114a1 flowing therein. This maximum pulse of
current 114a1 substantially simultaneously detonates each of the exploding
foil initiators 20a disposed on the surface of the flat cable conductor 42a
and
42b of figure 12.
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Referring to figures 24-28, another embodiment of the present invention is
illustrated. In this embodiment, instead of using a flat conductor cable 42a
and 42b having a plurality of initiators disposed thereon, as shown in
figures 12-16, to detonate the plurality of shaped charges in a perforating
gun as shown in figure 12, a sheet containing a plurality of initiators,
adapted to wrap around the entire circumference of the perforating gun of
figure 12, is utilized. When the sheet containing the plurality of initiators
is
wrapped around the entire circumference of the perforating gun of figure 12,
each of the initiators on the sheet will abut against the apex of it's
corresponding shaped charge for detonating the charge. The initiators on
the sheet may each include an exploding foil (flying plate or bubble
activated) initiator or an exploding bridgewire initiator.
In figure 24, a perforating gun 130 includes a shaped charge 132. In the
actual embodiment, the perforating gun 130 includes a plurality of shaped
charges 132. The perforating gun 130 is the same perforating gun as that
which is shown in figure 12, except that the flat cable conductors 42a and
42b of figure 12 are each replaced by a sheet 134 containing a plurality of
EFI initiators 20a as shown in figures 24-28 (hereinafter called "the sheet of
initiators"). In figure 24, the sheet of initiators 134 is shown laying flat
before the sheet has been wrapped around the circumference of the
perforating gun 130. The sheet 134 has an external side 134a and an
internal side 134b, and, in figure 24, the sheet 134 includes an initiator
136.
In the actual embodiment, the sheet 134 includes a plurality of initiators
134 corresponding, respectively, to the plurality of shaped charges 132 of
the perforating gun 130. In the preferred embodiment, the initiator 136 is
an exploding foil initiator 20a identical to the exploding foil initiator 20a
shown in figure 14 of the drawings. The charge 132 includes an apex 132a.
In figure 25, the sheet 134 has been wrapped around the entire
circumference of the perforating gun 130 until the initiator 136 abuts
against the apex 132a of the shaped charge 132.
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In figure 26, a three dimensional view of the perforating gun 130 of figures
24-25 is illustrated. Since the width "W" of the sheet 134 (see figure 27) is
approximately equal to the circamference of the perforating gun 130, the
sheet of initiators 134 is physically wrapped around the entire
circumference of the perforating gun 130 until the width "OV" of the sheet
134 equals the circumference of the gun 130. The wrapping of the sheet 134
around the circumference of the gun 130 takes place in a manner which
allows each of the plurality of EFI initiators 136 on the sheet to abut
against the apex 132a of their respective shaped charges 132. As a result,
when the initiator 136 detonates, the shaped charge 132 will detonate. The
initiator 136 includes external initiator terminals 136a disposed on the
external side surface of the sheet 134, similar to the external initiator
terminals 42a1 shown in figure 13.
In figure 27, the external side 134a of the sheet of initiators 134 of figure
26
is shown laying flat on a surface and illustrating a plurality of the external
initiator terminals 136a. In the preferred embodiment, the initiator 136 is
an exploding foil initiator 20a, similar to the exploding foil initiator shown
in figure 14 of the drawings. Therefore, the external initiator terminals
136a in figure 27 are terminals, disposed on the external side 134a of the
sheet of initiators 134, associated with an exploding foil initiator 20a. Each
of the external initiator terminals 136a include an EFI alignment hole
136a1, a charge jacket attachment hole 136a2, and a pair of EFI attach
holes 136a3, similar to the alignment hole 42a1(b), attachment hole 42a1(c),
and EFI attach holes 42a1(a) shown in figure 13 in connection with the flat
cables 42a and 42b. The EFI attach holes 136a3 are first and second
terminals, the first terminal of the EFI attach hole 136a3 being electrically
connected to the first part 20a2 of the exploding foil initiator 20a of figure
14, the second terminal of the EFI attach hole 136a3 being electrically
connected to the second part 20a3 of the exploding foil initiator 20a of
figure
14.
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Figure 28 illustrates a partial cross-section of one of the exploding foil
initiators 20a of figure 27 taken along section lines 28-28 of figure 27. In
figure 28, the sheet of initiators 134, in cross section, has the same layers
as
that which is discussed above with reference to figure 16 of the drawings.
However, for purposes of simplicity, in figure 28, only three layers of the
sheet of initiators 134 is iIlustrated: a first two (2) ounce copper layer
42a4
which conducts a current to each of the plurality of exploding foil initiators
20a; a second two (2) mil Kapton layer 42a5 which represents the second
polyimide layer 20c of figures 6-9; and a third two (2) ounce copper layer
42a6 which represents the second copper foil 20d functioning as a return
current path to ground potential in figures 6 and 8. The exploding foil
initiators 20a, being electrically connected to the first copper layer 42a4,
is
energized by a current conducting along the first copper layer 42a4 from the
current pulse generator (CPG) 44 of figure 11, and it is also electricaIly
connected to ground potential via the third copper layer 42a6. When the
bridge 20a1 of the exploding foil initiator 20a vaporizes in response to the
current from first copper layer 42a4, a flyer or bubble is formed from the
first polyimide layer 20b, the flyer/bubble propagating through the hole 19a
in barrel 19 thereby impacting the secondary explosive pellet 40a1 in
shaped charge 40a. As noted above in the discussion with reference to
figure 17, since the pellet 40a1 is comprised of the aforementioned special
explosive composition, the pellet 40a1 detonates the shaped charge 40a.
Referring to figure 29, a perforating apparatus is illustrated. This
perforating apparatus includes a first perforating gun 137, a second
perforating gun 141, and a detonation transfer unit 140 disposed between
the first perforating gun 137 and the second perforating gun 141. A first
detonating cord 138 is connected to and is associated with the first
perforating gun 137. A second detonating cord 142 is connected to and is
associated with the second perforating gun 141. A detonator 158 is
connected to the second detonating cord 142. The detonator 158 may be an
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CA 02599056 2007-09-11
exploding foil initiator detonator, or an exploding bridgewire initiator
detonator, or an electric detonator. The detonation transfer unit 140, which
separates the first perforating gun 137 from the second perforating gun 141,
is interconnected between the first detonating cord 138 and the detonator
158. A detailed construction of the detonation.transfer unit 140 of figure 29
is discussed below with reference to figure 30 of the drawings.
Referring to figure 30, a more detailed construction of the detonation
transfer unit 140 of figure 29 is illustrated.
In figure 30, the detonation transfer unit 140 includes a pressure bulkhead
152 which is adapted to isolate and insulate the pressure which exists
within the interior of the first perforating gun 137 from the pressure which
exists within the interior of the second perforating gun 141. An end of the
first detonating cord 138 of the first perforating gun 137 of figure 29 is
disposed in abutment against one side of the pressure bulkhead 152. A
piezoelectric ceramic disc 156 is disposed in abutment against the other side
of the pressure bulkhead 152. The piezoelectric ceramic 156 stores energy
and is connected to the detonator 158 of figure 29 associated with the second
detonating cord 142 of the second perforating gun 141 in figure 29. When a
first detonation wave from the first detonating cord 138 hits the pressure
bulkhead 152, the explosive plane wave of the first detonation wave is
transferred through the bulkhead 152 to the piezoelectric ceramic 156
disposed on the other side of the bulkhead 152 thereby causing the energy
stored in the piezoelectric ceramic 156 to dump into the detonator 158. As a
result, a second detonation wave propagates from the detonator 158 into the
second detonating cord 142 of the second perforating gun 141 of figure 29.
A functional description of the operation of the present invention is set
forth
in the following paragraphs with reference to figure 3 through figure 31 of
the drawings.
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78543-71
This functi.onal description will involve the perforating apparatus of figure
12, having the flat cable conductors 42a and 42b which helically wrap
around the perforating apparatus in a manner which abuts against the apex
of each shaped charge, and the perforating apparatus of figure 26, having
the sheet of initiators 134 which wraps around the entire circumference of
the perforating apparatus 130.
In figure 11, the current pulse generator 44 must generate a cu.rrent pulse,
similar to the current pulse shown in figure 19, in order to substantially
simultaneously detonate the plurality of shaped charges 40 of the
perforating apparatus in figures 11 and 12. In the preferred embodiment,
the current pulse generator 44 is the compressed magnetic flux (CMF)
current pulse generator 44 shown in figure 23 of the drawings. Recall that
the CMF generator 44 is described in a first article entitled "Sma.ll Helical
Flux Compression Amplifiers" by J.E. Gover, O.M. Stuetzer, and J.L.
Johnson, Sandia Laboratories, Albuquerque, New Mexico, printed in
"Megagauss Physics and Technology", 1979, and in a second article entitled
"The Central Power Supply", Showcase for Technology, conference and
exposition, 1981.
In ngnre 23, the exploding foil initiator (EFI) firing head 124 detonates the
booster 112a of the detonating cord 122. Recall that the nring head 124 is
described in U.S. Patent No. 5,347,929, filed
September 1, 1993, entitled "Firing System for a Perforating gun Including
an Exploding Foil Initiator and an Outer Housing for Conducting Wireline
Current and EFI Current", The detonating cnrs3122, in turn, detonates
the explosive 116a of armature 116. The explosive detonation of the
explosive 116a causes the piezoelectric ceramic 120 to release it's stored
energy. As a result, a current begins to flow in the inductance coil 114.
Detonation of the explosive 116a in the armature 116 causes the armature
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116 to expand in it's diameter dimension, the expanded diameter
propagating from left to right in figure 23. The expanded diameter of the
armature 116 begins to short circuit the turns of the inductance coi1114,
beginning with the left-most turn of the coi1114. The short circuit of coils
114 propagates from the left side of coil 114 to the right side in figure 23
until only one turn 114a of the coi1114 remains which is not short circuited.
The magnetic field produced by the coi1114 must remain constant.
Therefore, since the number of turns of the coi1114 is decreasing, the
current in the remaining coils which are not short circuited must increase.
10-As a result, a maximum pulse of current 114a1 flows in the one last
remaining turn 114a of the inductance coil 114. This maximum pulse of
current 114a1, shown in figure 23, flows into the plurality of initiators 20a
in figure 23.
In figure 12, the maximum pulse of current flows from the CMF generator
44a into the flat cable conductor 42a.
In figure 15, when the spark gap switch 52 begins to conduct (changes from
an open circuit to a closed short circuit condition), this maximum pulse of
current, from the last turn 114a of coi1114 of figure 23, flows on the
internal
side (the internal side being shown in figure 14) of the flat cable conductor
42a as follows: into the electrical current path 54 of figure 15, and begins
to
flow into the first plurality of parallel connected exploding foil initiators
20a4, then into the second plurality of parallel connected exploding foil
initiators 20a5, then into the third plurality of parallel connected exploding
foil initiators 20a6, then into the fourth plurality of paraIlel connected
exploding foil initiators 20a7, and then into the return electrical current
path 56 to ground potential. When this maximum pulse of current flows
into the first plurality of parallel connected EFI initiators 20a4, it flows
into
first, second, third and fourth EFI initiators 20a.
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In figures 5 and 14, when the maximum pulse of current flows into an EFI
initiator 20a, it first flows into the first part 20a2 of the EFI initiator
20a,
then into the bridge 20a1, and then into the second part 20a3 of the EFI
initiator 20a. When the maximum pulse of current flows through the bridge
20a1, the bridge 20a1 vaporizes producing a plasma gas which creates a
turbulence in the region immediately above the bridge 20a1.
In figures 6 and 8, in response to the turbulence produced in the region
immediately above the bridge 20a1, in figure 6, a disc 20b1 is sheared out
from the first polyimide layer 20b, the disc 20b1 flying through a hole 19a in
the barre119 and impacting the secondary explosive pellet 18a in figure 6
(40a1 in figures 16 and 17). When the disc impacts the pellet 18a, the
shaped charge 18 in figure 6 (40a in figure 17) detonates. However, in
figure 8, in response to the turbulence, a bubble 20b2 is formed from the
first polyimide layer 20b, the bubble 20b2 impacting the secondary explosive
pellet 18a (40a1 in figures 16 and 17) thereby detonating the shaped charge
18 in figure 8 and 40a in figure lfi.
When the last shaped charge 40a of the first perforating gun of the
perforating apparatus of figure 12 detonates, the pulse of current conducting
in the end of the first flat cable conductor 42a energizes the firing head 46c
of the intermediate adaptor 46 of figure 12.
In figure 12, when the EFI firing head 46c receives the pulse of current
conducting in the flat cable conductor 42a, a pellet in the firing head 46c
detonates. Detonation of the pellet in the firing head 46c initiates the
propagation of a first detonation wave in the first detonating cord 46a of the
intermediate adaptor 46. Since the second detonating cord 46b of
intermediate adaptor 46 is disposed in side-by-side abutment with the first
detonating cord 46a, the first detonation wave in the first detonating cord
46a transfers to the second detonating cord 46b. Therefore, a second
detonation wave now propagates in the second detonating cord 46b, and this
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CA 02599056 2007-09-11
detonation wave energizes the second CMF generator 44b. As a result, the
second CMF generator 44b produces another maximum pulse of current,
and that pulse of current propagates through the second flat conductor cable
42b in figure 12, detonating the plurality of shaped charges 40b of the
second flat cable conductor 42b in the same manner as described above in
connection with the first flat conductor cable 42a in figure 12.
Assume that the perforating gun in figure 12 does not use a flat conductor
cable. Assume, instead, that a sheet of initiators, such as the sheet of
initiators 134 shown in figure 26 of the drawings, is wrapped completely
around the entire circumference of the perforating gun of figure 12. Based
on that assumption, a functional description is set forth below with
reference to figures 23-28 of the drawings.
In figure 26, perforating gun 130 (the same gun as shown in figure 12 except
the flat cable conductors 42a and 42b are not used) has a sheet of initiators
134 wrapped completely around the circumference of the perforating gun
130.
In figure 23, the CMF generator 44 produces the pulse of current 114a1 in
the same manner described above in connection with the perforating gun of
figure 12.
In figure 26, the pulse of current 114a1 flows into the sheet of initiators
134.
In figure 28, when the pulse of current 114a1 has flowed into the sheet of
initiators 134, the current pulse 114a1 flows into the first two (2) ounce
copper layer 42a4, into the EFI attach hole 136a3, and into the EFI initiator
20a. Recalling that the EFI initiator 20a includes the first part 20a2, the
bridge 20a1, and the second part 20a3 (see figure 14), the pulse of current
114a1 flows through the first part 20a2, the bridge 20a1, the second part
20a3, into the EFI attach hole 136a3, and into the third two (2) ounce
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CA 02599056 2007-09-11
copper layer 42a6 to ground potential. The bridge 20a1 vaporizes producing
a turbulence directly above the bridge 20a1 of the EFI initiator 20a. As
noted in the above description, this turbulence either shears out a disc from
the first polyimide layer 20b, the disc flying through the hole 19a in barrel
(figure 6), or a bubble 20b2 is formed in the first polyimide layer 20b
(figure
8), the bubble 20b2 impacting the secondary explosive pellet 18a/40a1 and
detonating the shaped charge 18/40a.
As a result, when the pulse of current 114a1 enters the flat cable conductor
42a/42b of figure 12, or enters the sheet of initiators 134 of figures 26 and
27, all of the initiators (whether they are EFI flying plate or bubble
activated initiators 20a or exploding bridgewire initiators) on the flat cable
42a/42b or on the sheet of initiators 134 will detonate substantially
simultaneously. In addition, since an electrical current carrying conductor
is used to substantially simultaneously detonate a plurality of shaped
charges in a perforating gun, detonating cords are no longer needed.
The invention being thus described, it will be obvious that the same may be
varied in many ways. Such variations are not to be regarded as a departure
from the spirit and scope of the invention, and all such modifications as
would be obvious to one sldlled in the art are intended to be included within
the scope of the following claims.
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