Note: Descriptions are shown in the official language in which they were submitted.
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Apparatus and Method for Quick Connect of
a Plurality of Guns for Well Perforation
BACKGROUND OF THE INVENTION
Cross-Reference to Related Applications
[0001] This application claims priority under 35 U.S.C. 119(e) and P.C.T.
Rule 4.10 from co-
pending International Patent Application No. PCT/US2015/31047 filed in the
U.S. Receiving
Office, by Sergio F. Goyeneche, "Apparatus For Electromechanically Connecting
A Plurality Of
Guns For Well Perforation" filed 15 May 2015, which, by this statement, is
incorporated herein
by reference for all purposes.
Field of the Invention
[0002] This invention refers in general to an integral assembly (a "perf
assembly") of a plurality
of perforating guns ("guns") containing a plurality of shaped charges
("charges"). This perf
assembly is used for perforation of wells to increase flow. This invention is
particularly directed
to a new coupling between a plurality of perf guns to allow faster and more
reliable assembly
and sequential firing of the guns during the perforation process of production
wells.
[0003] This process of well perforation consists of the perforation of the
metallic casing of a
well, of isolating cement surrounding the casing, and of the layers of rock in
the producing
formation by means of explosives housed within perforating guns; achieving,
through bore holes
produced by a plurality of charges, a connection between the depths of the
producing zone and
the interior of the well. While this invention is generally found in the
petroleum production
industry, it may be equally applied to other environments where perforation of
well casing into
the surrounding environment is necessary, such as water wells.
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Background of the Invention
[00041 The perforation of producing wells is realized by lowering into the
well a perf assembly
comprised of a plurality of guns each containing a plurality of charges. The
guns are connected
by intermediate subs containing pass through openings for wiring. A firing
wire, coupled with
the casing as a ground, carries an electrical signal through the well bore to
connect with each gun
and allow firing of the detonators. The detonators may be fired through
independently
addressable switches or through a series of pressure switches and diodes which
isolate each gun
until the desired firing event. The perf assembly is then retrieved from the
well hole and the subs
are disassembled and saved for reuse. Undetonated explosives are safely
disposed of, and the
remaining assembly, consisting of pierced pipes, wires, and electronics are
then disposed.
[0005] One method of independently firing the guns is to use individually
addressable detonators
such as those described in U.S. Patent 8,091,477 and U.S. Patent 8,230,788.
Another method of
independently firing the guns is to connect each gun through a pressure
sensitive switch which
grounds the detonator of each gun until the pressure of the previous gun's
firing triggers the
switch to an active state. Further, diodes are used to cause each gun to
require a polarity reversal
from the signal which fired the previous gun. This prevents the signal from
propagating
throughout the assembly as the blasts set each pressure switch sequentially,
and the pressure
switches prevent the later guns from firing before the previous ones.
[0006] This method requires a continuous electrical signal to run the length
of the perf assembly.
However, wires are often twisted, broken, or can pull loose during the
assembly process during
the act of screwing the subs together. This results in the assembly having to
be deconstructed
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and repaired. Additionally, weakened wires may pass initial test during
construction only to fail
during the process of lowering the assembly to depth, or due to vibrations of
early charges in the
sequence. Additionally, the manual assembly process, when rushed, may be prone
to wiring
mistakes and other human error.
[0007] The preferred method is to fire the farthest/lowest gun first. Then,
sequentially fire each
gun back toward the well opening. This is because the
explosion/pressure/debris from one gun's
firing can possibly damage adjacent guns. Wires can break or connectors can
loosen during
shockwave vibrations, or by blast force. With pressure switches, any damage
requires retrieval
of the perf assembly for correction, as the rest of the assembly is now non-
fireable.
[0008] Addressable switches allow a damaged section to be skipped, but still
result in unfired
guns, which must be retrieved from the hole. Unfired guns are highly
undesirable, as they are
hazardous to bring to the surface due to the dangers of handling explosives
which are not known
to be in a safe condition or state.
[0009] To fulfill the operation so briefly described above, while
simultaneously respecting
existing norms for the manipulation of explosives, highly capable operators
are required to arm
and assemble the guns and the wellhead, stripping the ends of connecting wires
and joining them
by twisting the exposed portions of the wire together and covering the joint
with adhesive
electrical tape, resulting in an `artisanar activity requiring extreme
caution. While this assembly
process should be carefully completed and verified multiple times, it is just
human nature to rush
and possibly shortcut while performing this operation in the rain, cold
weather, or other adverse
conditions that are undesirable to the operator.
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[0010] It should be noted that petroleum production and exploration activities
are generally
located in areas with hostile climatic conditions for the operators; work
hours are assigned in
accordance to the needs of the operation and may include nighttime and daytime
hours, with
extreme cold or heat, rain or wind, darkness or sunlight.
[0011] Hours are controlled by working against the clock and by penalizing
setbacks; to that
respect, it is absolutely necessary that the strictest safety norms be
followed while handling
explosive material; all of these factors together contribute to an increased
likelihood that
operators may commit errors while wiring or assembling the guns into a pert'
assembly to be
introduced into the well. Further, even if the operators do everything
correctly, the actions
required to connect the pipe sections that make up the perf assembly may still
produce a costly
mistake.
[0012] Once the fracturing operations are complete, the perf gun must be
disassembled. The
operators must separate the pierced gun casings from the sub connectors
joining the guns,
remove any wiring and or electronics. Once the equipment has been disassembled
and separated,
the sub connectors between the guns, which are costly and reusable, are set
aside for later
operations. The wiring and electronics are disposed of along with the pierced
gun casing and the
remaining parts of the perf assembly.
[0013] From the above facts, there exists an obvious need to simplify the
operation of arming
and joining the guns into a perf assembly. There is also a need to ensure that
the firing of one
gun does not introduce faults into the remaining portions of the perf assembly
preventing the
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required firing sequence. The object of this invention deals with the means to
reduce the time
and effort required on site to perform the gun assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a cross-section of an assembly of multiple armed and
assembled guns in a
manner that is utilized in the industry.
[0015] FIG. 2 shows a cross section of a single gun joined on each end with a
tandem sub
assembly.
[0016] FIG. 2A shows an insulator cap assembly prior to mating with the gun or
sub.
[0017] FIG. 2B shows a bottom sub assembly containing a detonator attached to
a bottom sub
and mated with a perf gun.
[0018] FIG. 3 shows two guns joined by a sub assembly where in the
pressure/diode switch is
mounted in the sub assembly and placed in contact with the retractable contact
pin installed into
an insulating top end assembly of one of the guns.
[0019] FIG. 4 shows two guns with insulating contact pins in each end joined
by a sub assembly
incorporating a feed through pin to connect there between.
[0020] FIG. 5A, 5B, and 5C are views of a pressure switch end cap for securing
a pressure/diode
switch in accordance with an exemplary embodiment of the innovation.
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[0021] FIG. 5D is a perspective view of a pressure/diode switch and end cap in
accordance with
an exemplary embodiment of the innovation.
[0022] FIG. 6 and 7 illustrate the assembly of two perf guns joined by a short
sub.
[0023] FIG. 8 is cross section of a perf gun assembly, explosives omitted for
clarity, illustrating
the use of end caps, insulated contact pins, and an short sub.
[0024] FIG. 9 is cross section of a plurality of assembled perf guns and a
quick change pin box
for connection to the firing controls.
[0025] FIG. 9A is an enlarged cross section view of a perf gun connected to a
quick change pin
box.
DETAILED DESCRIPTION OF THE INVENTION
[0026] In the previous application, which is referenced and incorporated
above, the inventor
discussed, inter alia, utilization of improved gun performance via specialized
end caps on the
guns to protect the wires of other guns in the perf assembly during handling
and blasting
operations. However, the previous application still utilized intermediate sub-
assemblies (referred
to as tandem subs) for joining together the plurality of guns which resulted
in the tandem subs
needing to be retrieved from between the guns after firing. It also requires
extending wires
through tandem subs which may twist as the sub-assemblies are assembled.
[0027] More reliable assembly can be accomplished if there is a safe way to
prepare and wire
perf gun segments in a controlled environment in such a manner that the
segment can be safely
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transported to a well site and joined with other segments to produce the
needed perf gun
apparatus for use in the well. A plurality of independent shape charged shots
are sequentially
positioned and wired to a pressure/diode switch, secured centrally in an end
cap at one end, and
wired to an insulated polarized-charge carrier contact pin at the distal end
to produce a shot
assembly.
[0028] The shot assembly is secured internally in a gun body casing via snap
rings fitted to a
groove at the internal end of standardized pipe threads internal to and
located at the ends of the
casing to produce a perforating gun segment. The pressure/diode switch is
recessed in the gun
body casing, which may be temporarily enclosed with an insulating protector
cap to allow safe
transportation and storage of the perforating gun assemblies. The distal end's
contact pin
projects from the end of the gun body casing and may also be temporarily
enclosed with an
insulating protector cap secured to the internal threads of the body casing
allowing safe
transportation and storage of the perforating gun assemblies.
[0029] Once assembly is commenced at the site a plurality of the perforating
guns are joined
there between by short intermediate subs which allow the insulated polarized-
charge carrier
contact pin of one gun assembly to be positioned in contact with the
pressure/diode switch of the
neighboring gun assembly, completing the electrical circuit from one end of
the perf gun to the
distal in with a continuous electrical and physical contact.
[0030] In another embodiment, a plurality of guns with intermediate/tandem sub-
assemblies and
pressure/diode switches may be pre-assembled before transportation to reduce
site prep work.
Sub-assemblies maybe manufactured from low-grade steel, plastics, fiberglass,
or other material
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of sufficient strength to support the weight of the gun assembly and securely
connect it to the
drill pipe. One skilled in the art would understand that use of a non-
conductive material such as
plastics or fiberglass would also require an integrated conductor to ensure
proper electrical
grounding between the various assemblies.
[0031] Currently in the industry a plastic insulating or a metal bottom end
cap attaches to the
charge carrier, and approximately centers it within the gun body. The bottom
end cap has a
central hole through which passes a wire carrying the electrical firing
signal. A second wire
connects to a grounding pin affixed to the plastic end cap or to the metal end
cap which is routed
to contact against the gun body to establish a ground. Any of these wires may
be broken or
disconnected during assembly and therefore prior assembly and testing in is
preferred.
[0032] In the preferred embodiment, the perf gun has a recessed insulated
contact pin held by a
connector end cap in a central orientation at one end. The distal end has a
recessed
pressure/diode switch held by a connector end cap in a central orientation. A
tandem sub with a
feed thorough pin can connect the insulated contact pin of the connector end
of one perf gun to
the pressure/diode switch of the distal end of the neighboring gun to ensure
physical and
electrical contact throughout the entire perf gun assembly.
[0033] In another embodiment, only one of the two neighboring guns is
configured in
accordance with the innovation described herein. That perf gun has a recessed
insulated contact
pin held by a connector end cap in a central orientation at one end. In such a
situation, a tandem
sub with a pressure/diode switch is joined to the gun and the wires from the
pressure/diode
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switch are connected to the neighboring gun in a traditional manner of the
current practices in the
industry.
[0034] In another embodiment, that perf gun has a recessed pressure/diode
switch held by a
connector end cap in a central orientation. In such a situation, a tandem sub
with a feed through
pin is joined to the gun and distal end of the feed through pin is connected
to the firing wire of
the neighboring neighboring gun in a traditional manner of the current
practices in the industry.
[0035] 'The innovation includes replacing the traditional plastic or metal end
caps on each charge
carrier with an improved design which is more robust and reliable in the
assembly of multiple
guns into a single perf assembly as taught in the prior application, and
includes an additional
design for a robust and reliable end cap which houses a pressure/diode switch.
[0036] In the new innovation, the end cap of one perf gun positions the
insulated contact pin to
extend just past the end of the gun casing. The end cap of the neighboring
perf gun positions the
pressure/diode switch slightly recessed within the end of the gun casing. A
disposable short sub
assembly joins the two neighboring perf guns by threading into the ends of
each and thus placing
the insulating contact pin of the first perf gun in contact with the
pressure/diode switch of the
second perf gun.
[0037] The improved design eliminates the through hole in the center of the
bottom end cap,
which was previously used to pass wires through for connection, and allows the
connection to be
made by simply screwing the two guns together with the disposable short sub
assembly. This
eliminates the difficulty of ensuring proper wiring and operation. Further,
the disposable short
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sub assembly does not need to be retrieved from between the guns after firing,
or more
importantly in instances of misfires which leads to handling explosives in an
unknown state.
DETAILED DESCRIPTION OF THE DRAWINGS
[0038] The following is a detailed description of exemplary embodiments to
illustrate the
principles of the invention. The embodiments are provided to illustrate
aspects of the innovation,
but the invention is not limited to any embodiment. As those skilled in the
art will appreciate,
the scope of the invention encompasses numerous alternatives, modifications,
and equivalent; it
is limited only by the appended claims.
[0039] FIG. 1 is a cross-section of an assembly of multiple armed and
assembled guns in a
manner that is utilized in the industry. The perf a.ssembly (1) has a firing
head (2), a plurality of
perforating guns (3), each containing a charge carrier, two tandem subs (4),
and a bottom sub (5).
[0040] FIG. 2 shows a cross section of a single gun joined on each end with a
tandem sub
assembly. The gun (3) comprises a charge carrier (13) with a plurality of
explosive shape
charges (16) joined by a detonation cord or fuse (19). The charge carrier (13)
is supported,
substantially centered, within the gun body casing (12) by an insulating top
end (14) and an
isolating bottom end (15).
[0041] One can see in the interior of the carrier (13) that the shaped charges
(16) are shown set
in radial fashion, that is to say, perpendicular to the gun wall, to the
carrier, and, when the guns
are within the well, to the well casing. In the illustration, six shape
charges are illustrated, but
the actual number and orientation will vary.
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[0042] The shaped charges are explosives set in such a manner that they
concentrate the force of
the explosion outward, generating a jet of gas (plasma) at high pressure and
temperature, that
pulls the metal from the interior of the charge and projects it outward until
it arrives at the well
formation; with this action the charges produce a perforating effect that is
variable in proportion
to the potency of the charges.
[0043] In each intermediate joint or intermediate sub or tandem sub (4) one
can see the pressure
activated changeover switch (17), from which wires extend to the rest of the
assembly. When
the detonator is activated, a detonation is propagated by way of a "fuse"¨or
detonating cord
(19)¨to each of the shaped charges in the carrier (13) that burst in
simultaneous fashion within
the corresponding gun (3). Although not described in detail herein, the
internal details of the
assembly are protected by a watertight seal; otherwise the liquids present in
the well would enter
into the interior of the gun causing problems with the electric and/or
ballistic systems.
[0044] In FIG. 2A, the insulating end plate is represented as being attached
to the lower end of
the charge carrier (13), and has a tab for connecting the ground wire (22)
from the carrier to the
interior of the gun housing; furthermore, it has a hole, or central orifice,
(23) that permits the
passage of a pair of wires, 'live' or 'fire' (F) and 'ground' (G). These wires
are connected to the
components in the next tandem immediately below to pass the signal throughout
the assembly (1,
not illustrated) as required by the electronic configuration thereof.
[0045] In FIG. 2B, the insulating end plate (15) centers the charge carrier
(13) and causes the
grounding contact (22) to connect with the gun body (12) represented as being
attached to the
lower end of the charge carrier (13), and has a tab for connecting the ground
wire (22) from the
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carrier to the interior of the gun housing; furthermore, it has a hole, or
central orifice, (23) that
permits the passage of a pair of wires, 'live' or 'fire' (F) and 'ground' (G).
These wires are
connected to the components in the next tandem immediately below to pass the
signal throughout
the assembly (1, not illustrated) as required by the electronic configuration
thereof.
[0046] FIG. 3 shows two guns joined by a sub assembly where in the
pressure/diode switch is
mounted in the sub assembly and placed in contact with the retractable contact
pin installed into
an insulating top end assembly of one of the guns. The gun body casing (12)
encloses the charge
carrier (13) which contains the plurality of explosive shape charges (16).
[0047] A firing signal wire (F) carries the firing signal through the
insulated contact pin (500),
which is secured in the connector end cap (400) by a nut (550) to secure it
and allow movement
by the spring (540) which urges it outward to contact the pressure/diode
switch (17) secured by a
snap ring (600) in the tandem sub (4). The wires (F and G) carry the firing
signal from the
pressure/diode switch (17) to the neighboring gun. The neighboring gun in this
illustrated
exemplary assembly does not have an incorporated pressure/diode switch.
[0048] FIG. 4 shows two guns with insulating contact pins in each end joined
by a sub assembly
incorporating a feed through pin to connect there between. In this illustrated
exemplary
assembly each gun (12) comprises a snap ring (600) securing a connector end
cap (400) having a
central insulated contact pin (500) which passes the firing signal to the
addressable switch (620)
in each gun. The guns are joined by an intermediate sub (4) which has a
central feed through pin
(610) electrically and mechanically linking the insulating contact pins (500)
of each gun (12).
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[0049] FIG. 5A, 5B, and 5C are views of a pressure switch end cap for securing
a pressure/diode
switch in accordance with an exemplary embodiment of the innovation. The
pressure switch end
cap (700) is manufactured from a durable solid material which is electrically
conductive. In the
preferred embodiment the end cap is manufactured from aluminum. The pressure
switch end cap
(7(X)) has an inner face (710) and an opposing outer face (720).
[0050] The outer face (720) has a recessed 0-Ring (730) for sealing against
the short sub (not
illustrated), when one is used for assembly of guns. The inner face (710) has
an edge, the charge
carrier mating surface (740) which mates with the charge carrier of the gun,
and is secured
thereto with pins through the screw holes (745). A guide pin (760) extending
from one edge of
the pressure switch end cap (700) prevents the cap from turning once it is
mated to a guiding
groove in the gun body casing (12, not illustrated).
[0051] The inner edge of the guide pin (760) is beveled (765) to assist in
insertion into the gun
body casing (12). Guide points (770) aid in centering the cap in the gun body
casing while
minimizing contact to reduce insertion force required seating the cap. The
inner face of the cap
includes an opening (780) for the electrical wires of the pressure switch to
pass into the gun body
casing (12).
[0052] FIG. 5D is a perspective view of a pressure/diode switch and end cap in
accordance with
an exemplary embodiment of the innovation. The pressure/diode switch (17) has
an electrically
conductive pressure activator (20). The body of the pressure/diode switch has
one or more 0-
rings (630) which securely fit the central opening of the pressure switch end
cap's (7(X)) outer
face (720).
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[0053] The pressure switch end cap (7(X)) has another 0-ring (730) around the
outside of the
outer face (720) to contact with the short sub. The guide pin (760) and guide
points (770) ensure
a centrally located and non-twistable connection with the gun body casing
(12).
[0054] FIG. 6 and 7 illustrate the assembly of two perf guns joined by a short
sub. In the
referenced drawings, the left side is the upper gun, and the right side is the
lower gun. The gun
body casings (12) include threads to mate with the pipe threads (940) of the
short sub (900).
[0055] The pressure switch end cap (700) and the connector end cap (400) seat
into voids in the
short sub (900) so that the pressure/diode switch (17) is in electrical
contact (20) with the
insulating contact pin (500) of the neighboring gun. 0-rings (630) ensure a
water tight seal and
prevent contaminants from entering the guns at the short sub.
[0056] FIG. 8 is cross section of a perf gun assembly, explosives omitted for
clarity, illustrating
the use of end caps, insulated contact pins, and an short sub. The charge
carrier (13) with its
plurality of shape charge openings (16A) is secured co-axially with the gun
body casing (12).
One end has a pressure switch end cap (700) into which a pressure/diode switch
(17, not
illustrated) may be placed during final assembly.
[0057] The distal end of the charge carrier (13) has a connector end cap (400)
containing an
insulating contact pin (500) inserted into the lower side opening (920) of the
short sub (900).
The short sub (900) with 0-rings (630) is threaded (940) to the end of the gun
body casing (12)
securing the charge carrier (13) therein. A plurality of recesses for 0-rings
(950) on the upper
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side of the short sub (900) ensure water tight seals when the neighboring gun
is threaded (940)
on to secure the -pressure/diode switch (17) in the upper side opening (930).
[0058] FIG. 9 is cross section of a plurality of assembled pen f guns and a
quick change pin box
for connection to the firing controls. FIG. 9A is an enlarged cross section
view of a perf gun
connected to a quick change pin box. Continuing from FIG. 8, the upper side
opening (930) of
the short sub (900) is mated to the right side of FIG. 9 with the
pressure/diode switch (17) being
placed in contact with the insulated connector pin (500) of the lower side
gun.
[0059] At the top of the gun, illustrated on the left side of FIG. 9, a
terminating sub (670)
connects to the short sub (900) to secure a quick change pin box assembly
(800) to the gun. An
extending pin (810) and extension spring (820) are secured with a retainer
clip (840) to allow the
Quick connector pin (830) to protrude from the top of the entire gun assembly
for connection of
the firing signal wires.
[0060] The diagrams in accordance with exemplary embodiments of the present
invention are
provided as examples and should not be construed to limit other embodiments
within the scope
of the invention. For instance, heights, widths, and thicknesses may not be to
scale and should
not be construed to limit the invention to the particular proportions
illustrated. Additionally,
some elements illustrated in the singularity may actually be implemented in a
plurality. Some
element illustrated in the plurality could actually vary in count. Some
elements illustrated in one
form could actually vary in detail. Such specific information is not provided
to limit the
invention.
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[0061] The above discussion is meant to be illustrative of the principles and
various
embodiments of the present invention. Numerous variations and modifications
will become
apparent to those skilled in the art once the above disclosure is fully
appreciated. It is intended
that the following claims be interpreted to embrace all such variations and
modifications.
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