Note: Descriptions are shown in the official language in which they were submitted.
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Perforating Gun with Timed Self-Sealing Threads
RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Application No.
63/197,257, filed June
4,2021.
BACKGROUND
[0002] Generally, when completing a subterranean well for the production of
fluids, minerals, or
gases from underground reservoirs, several types of tubulars are placed
downhole as part of the
drilling, exploration, and completions process. These tubulars can include
casing, tubing, pipes,
liners, and devices conveyed downhole by tubulars of various types. Each well
is unique, so
combinations of different tubulars may be lowered into a well for a multitude
of purposes.
[0003] A subsurface or subterranean well transits one or more formations. The
formation is a body
of rock or strata that contains one or more compositions. The formation is
treated as a continuous
body. Within the formation hydrocarbon deposits may exist. Typically, a
wellbore will be drilled
from a surface location, placing a hole into a formation of interest.
Completion equipment will be
put into place, including casing, tubing, and other downhole equipment as
needed. Perforating the
casing and the formation with a perforating gun is a well-known method in the
art for accessing
hydrocarbon deposits within a formation from a wellbore.
[0004] Explosively perforating the formation using a shaped charge is a widely
known method for
completing an oil well. A shaped charge is a term of art for a device that
when detonated generates
a focused output, high energy output, and/or high velocity jet. This is
achieved in part by the
geometry of the explosive in conjunction with an adjacent liner. Generally, a
shaped charge
includes a metal case that contains an explosive material with a concave
shape, which has a thin
metal liner on the inner surface. Many materials are used for the liner; some
of the more common
metals include brass, copper, tungsten, and lead. When the explosive
detonates, the liner metal is
compressed into a super-heated, super pressurized jet that can penetrate
metal, concrete, and rock.
Perforating charges are typically used in groups. These groups of perforating
charges are typically
held together in an assembly called a perforating gun. Perforating guns come
in many styles, such
as strip guns, capsule guns, port plug guns, and expendable hollow carrier
guns.
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[0005] Perforating charges are typically detonated by a detonating cord in
proximity to a priming
hole at the apex of each charge case. Typically, the detonating cord
terminates proximate to the
ends of the perforating gun. In this arrangement, an initiator at one end of
the perforating gun can
detonate all the perforating charges in the gun and continue a ballistic
transfer to the opposite end
of the gun. In this fashion, numerous perforating guns can be connected end to
end with a single
initiator detonating all of them.
[0006] The detonating cord is typically detonated by an initiator triggered by
a firing head. The
firing head can be actuated in many ways, including but not limited to
electronically, hydraulically,
and mechanically.
[0007] Expendable hollow carrier perforating guns are typically manufactured
from standard sizes
of steel pipe with a box end having internal/female threads at each end. Pin
ended adapters, or
subs, having male/external threads are threaded one or both ends of the gun.
These subs can
connect perforating guns together, connect perforating guns to other tools
such as setting tools and
collar locators, and connect firing heads to perforating guns. Subs often
house electronic,
mechanical, or ballistic components used to activate or otherwise control
perforating guns and
other components.
[0008] Perforating guns typically have a cylindrical gun body and a charge
tube or loading tube
that holds the perforating charges. The gun body typically is composed of
metal and is cylindrical
in shape. Charge tubes can be formed as tubes, strips, or chains. The charge
tubes will contain
cutouts called charge holes to house the shaped charges.
SUMMARY OF EXAMPLE EMBODIMENTS
[0009] An example embodiment may include a perforating gun system having a
first perforating
gun having a housing with a first end, a second end with first alignment
mechanism, and a first set
of scallops aligned with the alignment mechanism, a second perforating gun
having a housing with
a first end with a second alignment mechanism coupled to the first alignment
mechanism of the
second end of the first perforating gun, and a second set of scallops aligned
with the second
alignment mechanism, wherein the coupling of the first perforating gun to the
second perforating
gun aligns the first set of scallops with the second set of scallops.
[0010] A variation of the example embodiment may include the first alignment
mechanism being
timed male threads. The second alignment mechanism may be timed male threads.
It may have at
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least one o-ring seal between the second end of the first perforating gun and
the first end of the
second perforating gun. It may have a positive stop at the point of full
engagement between the
second end of the first perforating gun and the first end of the second
perforating gun. The positive
stop may be an angled face that resists rotation beyond a predetermined point
of thread
engagement. The positive stop may be a 45-degree angled face. The timed male
threads and timed
female threads may be self-sealing. It may include a positive stop at the
point of full engagement
between the second end of the first perforating gun and the first end of the
second perforating gun.
The positive stop may be an angled face that resists rotation beyond a
predetermined point of
thread engagement. The positive stop may be a 45-degree angled face.
[0011] An example embodiment may include a perforating gun system having a
first perforating
gun having a housing with a first end, a second end with timed male threads,
and a first set of
scallops aligned with the timed male threads, a second perforating gun having
a housing with a
first end with timed female threads coupled to the second end of the first
perforating gun with
timed threads, and a second set of scallops aligned with the timed female
threads, wherein the full
engagement of the timed male timed with the timed female threads aligns the
first set of scallops
.. with the second set of scallops.
[0012] A variation of the perforating gun system may include at least one o-
ring seal between the
second end of the first perforating gun and the first end of the second
perforating gun. It may
include a positive stop at the point of full engagement between the second end
of the first
perforating gun and the first end of the second perforating gun. The positive
stop may be an angled
face that resists rotation beyond a predetermined point of thread engagement.
The positive stop
may be a 45-degree angled face. The timed male threads and timed female
threads may be self-
sealing.
[0013] An example embodiment may include a method for assembling a perforating
gun string
including threading a first timed threads of a first perforating gun into a
second timed threads of a
second perforating gun, aligning a first set of scallops on the first
perforating gun with a second
set of scallops on a second perforating gun, engaging the first timed threads
of the first perforating
gun with the second timed threads of the second perforating gun fully, wherein
the full engagement
of the first perforating gun with the second perforating gun aligns the first
set of scallops with the
second set of scallops.
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[0014] A variation of the example embodiment may include engaging a positive
stop when
engaging the first timed threads of the first perforating gun with the second
timed threads of the
second perforating gun. It may include the full engagement of the first
perforating gun with the
second perforating gun provides a pressure seal between the inside of the
perforating gun string
and the outside of the perforating gun string.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] For a thorough understanding of the example embodiments, reference is
made to the
following detailed description of the preferred embodiments, taken in
conjunction with the
accompanying drawings in which reference numbers designate like or similar
elements throughout
the several figures of the drawing. Briefly:
FIG. 1 is a side view of a perforating gun with self-sealing tapered threads.
FIG.2 is a partially transparent view of a perforating gun with self-sealing
tapered threads.
FIG.3 is a cutaway view of two perforating guns with timed self-sealing
tapered threads
connected to each other.
FIG.4 is a cutaway view of a perforating gun with self-sealing tapered
threads.
FIG.5 is a cutaway view of the connection of two perforating guns with self-
sealing tapered
threads connected to each other.
FIG.6 is a perspective view of two perforating guns with timed self-sealing
tapered threads
connected to each other.
FIG.7 is a perspective view of the connection of two perforating guns with
timed self-
sealing tapered threads connected to each other.
FIG.8 is a partial cutaway view of the connection of two perforating guns with
timed self-
sealing tapered threads connected to each other.
DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS
[0016] In the following description, certain terms have been used for brevity,
clarity, and
examples. No unnecessary limitations are to be implied therefrom and such
terms are used for
descriptive purposes only and are intended to be broadly construed. The
different apparatus,
systems and method steps described herein may be used alone or in combination
with other
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apparatus, systems and method steps. It is to be expected that various
equivalents, alternatives,
and modifications are possible within the scope of the appended claims.
[0017] Terms such as booster may include a small metal tube containing
secondary high
explosives that are crimped onto the end of detonating cord. The explosive
component is designed
to provide reliable detonation transfer between perforating guns or other
explosive devices, and
often serves as an auxiliary explosive charge to ensure detonation.
[0018] Detonating cord is a cord containing high-explosive material sheathed
in a flexible outer
case, which is used to connect the detonator to the main high explosive, such
as a shaped charge.
This provides an extremely rapid initiation sequence that can be used to fire
several shaped charges
simultaneously.
[0019] A detonator or initiation device may include a device containing
primary high-explosive
material that is used to initiate an explosive sequence, including one or more
shaped charges. Two
common types may include electrical detonators and percussion detonators.
Detonators may be
referred to as initiators. Electrical detonators have a fuse material that
burns when high voltage is
applied to initiate the primary high explosive. Percussion detonators contain
abrasive grit and
primary high explosive in a sealed container that is activated by a firing
pin. The impact of the
firing pin is sufficient to initiate the ballistic sequence that is then
transmitted to the detonating
cord.
[0020] Initiators may be used to initiate a perforating gun, a cutter, a
setting tool, or other
downhole energetic device. For example, a cutter is used to cut tubulars with
focused energy. A
setting tool uses a pyrotechnic to develop gases to perform work in downhole
tools. Any downhole
device that uses an initiator may be adapted to use the modular initiator
assembly disclosed herein.
[0021] As shown in the example embodiments of FIGs 1-8, the perforating guns
include housings
10 that have male threads 13 and a baffle 11 at one end (the pin end) and
female threads 40 at the
other end (the box end). The threads are of a tapered and/or self-sealing
variety. This allows the
perforating gun housing 10 to provide a pressure seal between the interior and
exterior of the
housing 10 without relying on o-rings. This allows for simplification of
manufacturing and
associated costs by reducing the number of machining operations necessary to
manufacture the
perforating gun housing 10. This also allows for simplification of the
assembly of the perforating
gun and associated costs by reducing the number of parts and operations
required.
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[0022] The male and female threads may also be timed (also referred to as
clocked) so that the
scallops 12 and/or perforating charges of adjacent perforating guns are
aligned with each other
when the threaded connection between guns is made up. Having the threaded
connection timed to
align the perforating charges and/or scallops 12 of the adjacent perforating
guns allows the
orientation of an entire string of perforating guns without the use of
alignment or orienting subs
and/or locking collars between perforating guns.
[0023] Perforating guns often, but not always have scallops 12, or machined
thin wall areas, that
are aligned with the exiting jet of the perforating shaped charges. The
examples of this description
could be made with or without scallops 12.
[0024] As seen in FIG. 3, the perforating guns each include a charge tube 15,
25 within each gun
housing 10, 20 respectively. Between each perforating gun is a pressure
bulkhead 11. In this
example embodiment the first gun housing 10 with scallops 12 engages with the
second gun
housing 20 with scallops 22. When coupling the tapered threads 13 of the pin
end of the first gun
housing 10 with the box end threads 43 of the second gun housing 20 there is a
contact point where
the threads initially make contact that is also aligned with the scallops 12
and 22. The purpose of
the pressure bulkhead/baffle 11 is to isolate the interior of each perforating
gun from pressure that
may be present in the interior of adjacent perforating guns. This pressure can
be caused by leaking
of wellbore pressure into the interior of a perforating gun, pressure from
detonation of explosives
within a perforating gun, or equalization of wellbore pressure into a
perforating gun housing 10
through holes made by perforating charges. Typically, o-rings provide the
pressure seal between
the pressure bulkhead/baffle 11 and the perforating gun carrier or housing 10.
The second
perforating gun housing 20 has a second bulkhead 21 for coupling to a third
perforating gun
housing.
[0025] In the example of FIG. 4, an o-ring groove is seen in the bulkhead 11
that could be used to
provide a pressure seal between the baffle 11 and perforating gun housing 10.
A top end fitting 16
on the loading tube holds an integral selective perforating switch. Such a
switch is generally
addressable to allow selective detonation of a single perforating gun in the
string. The switch may
also include an orientation detector, such as a gyroscope and/or an
accelerometer that provides
data regarding the orientation of the switch and, correspondingly, the
perforating charges. In the
example of FIG. 4, a pressure bulkhead/bottom contact within the bulkhead 11
provides an
electrical connection on the bottom of the perforating gun that connects to
the interior of the
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perforating gun housing 20, such as to the switch. The top end fitting 16 in
concert with the
bulkhead 11 provides a pressure seal between the interior of the perforating
gun housing 10 and
the wellbore or an adjacent perforating gun. The top end fitting 16 also
includes a top contact
providing electrical connections on the top of the perforating gun that
connect to the interior of the
perforating gun, such as to the switch. The charge tube 15 includes cutouts 19
for installation of
shaped charges.
[0026] Alternatively, the perforating gun may not include a switch. In that
example, the electrical
connections would still pass electrical signals from one perforating gun to
another without the
presence of a switch in each perforating gun.
[0027] FIG. 5 shows a detailed view of the connection between two perforating
guns. The first
.. perforating gun housing 10, having tapered threads 13, is coupled to the
second perforating gun
housing 20, having female threads 43. In this example, the bulkhead 11
includes a larger diameter
sealing portion having a shoulder on each side. These shoulders then engage
corresponding
shoulders 31 on the adjacent perforating gun housing 20. This captures the
sealing portion of the
bulkhead 11 between the two adjacent perforating gun housings 10, 20. This
engagement provides
a metal-to-metal high pressure seal 33 between adjacent perforating guns. Such
an arrangement
obviates the necessity of exterior/external o-rings. FIG. 5 also shows the
seal provided by tapered
self-sealing threads in adjacent gun carriers. End fitting 17 is shown
supporting the charge tube
15. The bottom contact 18 provides electrical communication through the
bulkhead 11. The spring
32 provides additional contact support within the bulkhead 11. The end fitting
26 supports the
charge tube 25 with shaped charge cutouts 29.
[0028] These example features are further shown in FIGs 6-8. A first
perforating gun housing 10
is coupled to a second perforating gun housing 20. The scallops 12 and 22 are
aligned. The
alignment is provided by the timed threads. The gun carrier may include a
positive stop 45 aligned
with the scallops 12 and 22 to provide specific engagement for timing the
threads on adjacent gun
housings to ensure the alignment of the scallops 12 and 22 when the two
perforating gun housings
10 and 20 reach their engagement point 34. The positive stop 45 may be a face
angled relative to
the long axis of the gun carrier 50. In that case, torque applied when making
up the threaded joint
between adjacent perforating gun housings 10 and 20 can be converted to axial
force, thus
improving engagement between the threads of adjacent gun carriers, and further
improving sealing
and pressure resistance. In some examples, the angle of the positive stop 45
may be 45 degrees.
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[0029] In some examples, not all of these features will be present. In various
examples, the key
features may be present in any combination. For example, a tool string may
have perforating guns
with timed threads that are not necessarily self-sealing and may use
traditional sealing mechanisms
such as o-rings. In another example, a tool string may have perforating guns
without timed threads,
but whose threads are self-sealing and may not use traditional sealing
mechanisms such as o-rings.
In another example, a tool string may include perforating guns that have a
positive stop, or a
positive stop with an angled face, without requiring timed threads and self-
sealing threads, or
without either timed threads or self-sealing threads.
[0030] These improvements could also be combined with an orientation sensor or
orientation
sensing switch to provide confirmation of each perforating guns orientation
before firing and/or
when fired.
[0031] Although the example embodiments have been described in terms of
embodiments which
are set forth in detail, it should be understood that this is by illustration
only and that the example
embodiments are not necessarily limited thereto. For example, terms such as
upper and lower or
top and bottom can be substituted with uphole and downhole, respectfully. Top
and bottom could
be left and right, respectively. Uphole and downhole could be shown in figures
as left and right,
respectively, or top and bottom, respectively. Generally downhole tools
initially enter the borehole
in a vertical orientation, but since some boreholes end up horizontal, the
orientation of the tool
may change. In that case downhole, lower, or bottom is generally a component
in the tool string
that enters the borehole before a component referred to as uphole, upper, or
top, relatively
speaking. The first housing and second housing may be top housing and bottom
housing,
respectfully. In a gun string such as described herein, the first gun may be
the uphole gun or the
downhole gun, same for the second gun, and the uphole or downhole references
can be swapped
as they are merely used to describe the location relationship of the various
components. Terms like
wellbore, borehole, well, bore, oil well, and other alternatives may be used
synonymously. Terms
like tool string, tool, perforating gun string, gun string, or downhole tools,
and other alternatives
may be used synonymously. The alternative embodiments and operating techniques
will become
apparent to those of ordinary skill in the art in view of the present
disclosure. Accordingly,
modifications of the example embodiments are contemplated which may be made
without
departing from the spirit of the claimed example embodiments.
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