Note: Descriptions are shown in the official language in which they were submitted.
CA 02619167 2008-01-30
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PATENT
Atty. Dkt. 22.1616
PROCESS OF IMPROVING A GUN ARMING EFFICIENCY
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention generally relates to perforating apparatus, and,
more
particularly, to a process for improving the efficiency with which a
perforating gun is
armed.
Description of the Prior Art
[0002] For purposes of enhancing production from a subterranean formation, a
perforating gun typically is lowered down into a wellbore that extends through
the
formation. A perforating gun may, for example, comprise a plurality of
radially-oriented
shaped charges which are detonated to form perforations in the formation
proximate the
wellbore. The shaped charges may, for example, be placed at points along a
helical spiral
that extends around a longitudinal axis of the perforating gun.
[0003] Current gun systems use separate components for the pressure bulkhead,
detonator, charge holder, detonation cord and wiring to the guns below. When a
gun is
built, all the pieces are assembled together except the detonator and shipped
to the
location where the perforating operation is to be conducted. At that location,
the gun is
opened and the detonator is installed. The detonator may, for example, be an
RF-safe
detonator provided by the assignee of the present application, and this
detonator may
include an addressable switch, a fireset and an initiator. Accordingly, the
installation of
the detonator assembly at the site where perforating is to take place involves
the
connection of a number of wires in a very small space. The installation of the
detonator
also involves the utilization of a safety tube in which the detonator is
placed before
connection of the detonator to the wiring in the loading tube.
[0004] It would be advantageous to be able to arm a perforating gun by
utilizing a port in
the gun assembly thereby avoiding the disassembly of the gun components. These
novel
and useful results have been realized by the method and apparatus of the
present
invention.
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SUMMARY OF THE INVENTION
[0005] In accordance with some aspects of the present invention, a process is
provided for assembling
a perforating gun. A process in accordance with some aspects of the present
invention comprises
installing into a gun tube at a first location (e.g. a workshop, manufacturing
site, testing facility or
non-field location that is not the site at which perforating operations will
be conducted) a
plurality of shaped charges having primer ends, a ballistics train including a
detonating
cord connected to the primer ends of the shaped charges, a detonator receptor
that holds a
booster and cord in place near a port, and wiring operatively connected
between the ends
of the gun tube and to the detonator receptor. One end of the detonating cord
is also
operatively connected to the detonator receptor. An embodiment of the
detonator
receptor includes an addressable switch and a I-inset and a receptacle for
receiving either
an exploding foil initiator or an exploding bridge wire detonator. In other
embodiments,
the detonator receptor includes a receptacle for receiving either an exploding
foil initiator
or an exploding bridge wire, but does not include an addressable switch. An
addressable
switch comprises a circuit facilitating selection (e.g., from a surface
location) of a
particular perforating gun in a string of perforating guns. While the
detonator receptor
includes a receptacle for receiving either an exploding foil initiator or an
exploding
bridge wire detonator, it is significant that the exploding foil initiator or
exploding bridge
wire is not installed into the receptacle at the first location. The gun tube
thus assembled
may easily be packaged and electrically tested at the first location.
[0006] A gun tube thus assembled at the first location is then transported to
a second
location, where the second location is the site at which the perforating
operation will be
conducted (e.g. a field location or other deployment site). At the second
location, a process in
= accordance with some aspects of the present invention comprises the step
of installing an
initiating device into the gun tube through a port in the carrier. The
initiating device may,
for example, be electrically connected to the fireset of the detonator
receptor by a pair of
wires through the port while in a safety tube and may then be operatively
connected to
the detonation cord by installing it into the detonator receptor. In one
embodiment, the
initiating device comprises an exploding foil initiator, while in another
embodiment the
initiating device is an exploding bridge wire detonator.
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[0007] In accordance with some aspects of the present invention, a method of
operating a
perforating system is provided which comprises assembling a plurality of gun
assemblies as
described above and installing the assemblies into a carrier. Each adjacent
pair of gun
assemblies is separated by a pressure bulkhead. After many gun assemblies and
pressure
bulkhead as are needed in the perforating operation are assembled into the
perforating string,
the perforating string may then be lowered into the wellbore and the shaped
charges may be
detonated.
[0008] In accordance with some aspects of the present invention, a gun tube is
provided
which is made in accordance with the process of installing shaped charges, a
detonating cord,
a detonator receptor and wiring into the gun tube at a first location which is
not the site at
which the perforating operation will be conducted. Apparatus in accordance
with some
aspects of the present invention includes a gun tube into which an RF-safe or
similar detonator
is installed at the location where the perforating operations are to be
conducted.
[0008a] According to one aspect of the present invention, there is provided a
process for
assembling a gun tube with first and second ends for use in a perforating gun,
comprising:
installing shaped charges and detonating cord in the gun tube at a first
location which is not
where the perforating operation will be conducted, the detonating cord being
operatively
connected to the primer ends of the shaped charges; forming a port in the gun
tube to permit
access to the interior of the gun tube; obstructing communication into the gun
tube with a
removable plug; installing a fireset and detonator receptor at the first
location, wherein the
fireset and detonator receptor are adapted to receive an initiating device
into the gun tube
proximate said port; and installing wiring into said gun tube at the first
location where the
wiring is operatively connected between the ends of the gun tube and to the
detonator
receptor.
[0008b1 According to another aspect of the present invention, there is
provided a method of
assembling a perforating system, comprising: (a) installing a detonator
receptor comprising
an addressable switch and a fireset into a gun tube at a first location which
is not where the
perforating operation will be conducted; (b) installing wiring into said gun
tube at said first
location; (c) installing shaped charges and a detonating cord into the gun
tube at said first
location; (d) covering access ports in the gun tubes; (e) repeating steps (a)-
(d) for as many gun
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tubes as are required in the perforating system; (f) transporting the gun
tubes assembled in
steps (a)-(d) to a second location which is the site where perforating
operations will be
conducted; (g) uncovering access ports; (h) installing an RF-safe initiating
device into each
gun tube at said second location through a port in the gun tube, said RF-safe
initiating device,
when installed, being operatively connected to said fireset and to said
detonating cord; and (i)
covering access ports.
10008c1 According to still another aspect of the present invention, there is
provided apparatus
for use in a perforating gun comprising: a gun tube with first and second ends
with connectors
at said ends for receiving shaped charges, a detonating cord and wiring; a
port in the gun tube
covered by a removable plug; a detonator receptor comprising a fireset
installed in said gun
tube at a first location which is not the site at which perforating operations
are to be
conducted; wiring which is installed at said first location and which is
operatively connected
between the connectors and to the detonator receptor; a detonating cord and
shaped charges
which are installed into the gun tube at a said first location, the detonating
cord being
operatively connected to the primer ends of the shaped charges and to the
detonator receptor.
[0008d] According to yet another aspect of the present invention, there is
provided a
perforating apparatus for assembly at a first location and for use in a
perforating system at a
second location, where the first location is not the site where perforating
operations will be
conducted, comprising: a gun tube having an inner bore formed therein and
first and second
ends and connectors at each first and second end, the inner bore adapted for
receiving shaped
charges, a detonating cord, wiring, and a detonator receptor, the gun tube
further comprising a
port formed therein adapted to establish communication between the inner bore
and external
of the gun tube, the detonator receptor comprising an addressable switch and a
fireset for
operative connection to the detonating cord, the detonator receptor further
comprising a
receptacle for receiving a RF-safe initiating device; a plug adapted to close
the port in the gun
tube; a plurality of shaped charges having primer ends; a detonating cord for
connection to the
primer ends of the shaped charges; and wiring for connection between the
connectors and to
the detonator receptor.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0009] In the accompanying drawings:
[0010] FIGS. 1-3 are pictorial diagrams in partial cross-section which
illustrates an
installation of a detonator into a perforating gun according to the prior art.
[0011] FIGS. 4-6 are pictorial diagrams in partial cross-section which
illustrate a process in
accordance with some aspects the present invention.
DESCRIPTION OF THE SPECIFIC EMBODIMENTS
[0012] It will be appreciated that the present invention may take many forms
and
embodiments. In the following description, some embodiments of the invention
are described
and numerous details are set forth to provide an understanding of the present
invention.
Those skilled in the art will appreciate, however, that the present invention
may be practiced
without those details and that numerous variations and modifications from the
described
embodiments may be possible. The following description is thus intended to
illustrate and not
to limit the present invention.
[0013] In the specification and appended claims: the terms "connect",
"connection",
"connected", "in connection with", and "connecting" are used to mean "in
direct connection
with" or "in connection with via another element"; and the term "set" is used
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Atty. Dkt. 22.1616
to mean "one element" or "more than one element". As used herein, the terms
"up" and
"down", "upper" and "lower", "upwardly" and downwardly", "upstream" and
"downstream"; "above" and "below"; and other like terms indicating relative
positions
above or below a given point or element are used in this description to more
clearly
described some embodiments of the invention. However, when applied to
equipment and
methods for use in wells that are deviated or horizontal, such terms may refer
to a left to
right, right to left, or other relationship as appropriate.
[0014] In general, the present invention regards improved perforating gun
apparatuses
and processes of manufacture, assembly, and use for RF-safe gun systems. As
used
herein, the term "RF-safe" means that the initiator of the gun system is
designed to be
substantially immune to typical levels of electrostatic discharge, RF
radiation, and/or
accidental or unintended applications of power. Moreover, various embodiments
of the
perforating gun apparatus and processes of manufacture and use are described
with
respect to selective fire (e.g., wherein the RF-safe initiator includes an
addressable
switch). It is intended, however, that other embodiments of the present
invention include
improved perforating gun apparatuses and processes of manufacture, assembly,
and use
for non-selective fire gun systems (e.g., wherein the RF-safe initiator does
not include an
addressable switch). In the specification, the term "RF-safe initiating
device" is used to
mean an exploding foil initiator, an exploding bridge wire detonator, or other
component
to initiate the gun system in an RF-safe manner. In the specification and
appended
claims, the terms "detonator" and "initiator" may be used interchangeably.
[0015] With reference to FIGS. 1-3, there is illustrated a process according
to the prior
art for installing a detonator 10 in a gun tube 12 at a location where
perforating
operations are to be conducted. The size of detonator 10 necessitates the
removal of end-
to-end connections 22 of adjacent gun assemblies 12 and 20 to install
detonator 10 in gun
tube 12. After end-to-end connections 22 have been removed detonator 10 is
placed in
safety tube 18 and the wires 14 are then connected to the leads of the
detonator 14. Once
wired, detonator 10 may be removed from safety tube 18 and installed in the
ballistics
train by connecting detonating cord 16 to detonator 10. The end-to-end
connections 22
of the gun assemblies 12 and 20 may then be re-established. This prior art
method of
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Atty. Dkt. 22.1616
assembling a perforating gun for deployment in the field is inefficient due to
the
disassembly required.
[0016] With reference now to FIGS. 4-6, an embodiment of a gun tube 40 in
accordance with the present invention comprises a detonator receptor 48 which
could
include an addressable switch, a fireset, or simply a receptacle 49 for
receiving an RF-
safe initiating device, but does not include an initiating device. In other
embodiments,
the detonator receptor 48 does not include an addressable switch. The
detonator receptor
48, along with shaped charges (not shown), wiring 41, and detonating cord 52
are
installed in gun tube tube 40 at a first location which is not the site where
perforating
operations are to be conducted. The wiring 20 interconnects the ends of the
gun tube 44,
40 and is connected to the detonator receptor 48. The detonating cord 52 is
connected to
the primer ends of the shaped charges, and one end of detonating cord 52 is
operatively
connected to detonator receptor 48. All of the components of the detonating
apparatus
(absent the RF-safe initiating device) are thus installed at the first
location.
[0017] Gun tube 40 further comprises a port 42 covered by a removable plug 43.
In
various embodiments, the plug 43 may be an insertable, threaded, or sliding
cover, or any
other device to removably obstruct communication into the inner bore of the
gun tube.
At a second location which is the site at which perforating operations are to
be conducted,
port 42 is opened and RF-safe initiating device 56 is connected to wires 50
such that the
RF-safe initiating device is operatively connected to the fireset in the
detonator receptor
48. Once wired, RF-safe initiating device 56 may be installed via port 42 into
receptacle
49 of detonator receptor 48. The installation of RF-safe initiator 56 into
detonator
receptor 48 is such that RF-safe initiating device 56 is operatively connected
to the
detonating cord 52. After installation of the RF-safe initiating device 56,
port 42 is
closed again communication into the gun tube 40 is interrupted by plug 43.
[0018] In some embodiments, the gun tube may comprise a loading tube, or any
other
tubular gun housing assembly. Also, in some embodiments, the detonator
receptor may
comprise an electronic board.
[0019] Embodiments of the perforating gun of the present invention -- as
described above
-- include apparatuses, processes, and methods wherein a perforating gun is
assembled at
a first location that is not the site of perforating operations. The "first
location" can
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Atty. Dkt. 22.1616
actually comprise one location that is not the actual perforating site (i.e.,
at the well), or
alternatively a combination of locations each of which are not the actual
perforating site.
For example, the initiator (without the final RF-safe initiating device) may
be
manufactured and installed into the gun tube at a shop in China, and then the
gun tube
may be transported to a shop in the United States where the detonating cord
and shaped
charges are installed and the gun tube is transported to the well site. At the
wellsite, the
RF-safe initiating device may be installed via a port in the gun tube. One or
more of the
guns may be connected together to form an assembled and armed perforating gun
string.
Finally, the perforating gun string may be deployed in the well for detonation
downhole.
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