U.S. patent application number 10/096609 was filed with the patent office on 2003-10-02 for shaped-charge liner with precursor liner.
Invention is credited to Barlow, Darren R., Glenn, Corbin S..
Application Number | 20030183113 10/096609 |
Document ID | / |
Family ID | 27765404 |
Filed Date | 2003-10-02 |
United States Patent
Application |
20030183113 |
Kind Code |
A1 |
Barlow, Darren R. ; et
al. |
October 2, 2003 |
Shaped-charge liner with precursor liner
Abstract
The present disclosure suggests a method to remove well bore
fluid from the path of a shaped-charge jet in order to reduce the
effect it has on the jet tip. This most preferred embodiment uses a
precursor liner and a primary liner both pressed in the same
housing. In the most preferred embodiment, the primary liner is
similar or equivalent to a standard big hole shaped charge liner.
The precursor liner is pressed into the apex end of the primary
liner and upon detonation is intended to form an initial very fast
moving precursor jet to open a path through the fluid of the well
bore annulus for the following primary jet. In the preferred
embodiment the precursor liner is made from different material,
preferably a less dense material and/or a material having a higher
sound speed, than the material forming the primary liner.
Inventors: |
Barlow, Darren R.;
(Mansfield, TX) ; Glenn, Corbin S.; (Benbrook,
TX) |
Correspondence
Address: |
CONLEY ROSE, P.C.
5700 GRANITE PARKWAY, SUITE 330
PLANO
TX
75024
US
|
Family ID: |
27765404 |
Appl. No.: |
10/096609 |
Filed: |
March 12, 2002 |
Current U.S.
Class: |
102/476 |
Current CPC
Class: |
F42B 1/028 20130101 |
Class at
Publication: |
102/476 |
International
Class: |
F42B 010/00 |
Claims
What is claimed is:
1. A liner for a shaped-charge having two liner components, each
component having a convex outer surface, a concave inner surface,
an apex having a center, a mouth portion of the liner component
opposite the apex of the liner component, and a skirt portion
terminating in a circular skirt edge at the mouth portion of the
liner component, the liner comprising: a first component made of a
first material and having an opening at the center of the apex of
the first component; a second component made of a second material
wherein a portion of the second component is within the opening at
the center of the apex of the first component; wherein the first
material and the second material comprise different materials.
2. The liner of claim 1, wherein the first material has a greater
density than the second material.
3. The liner of claim 1, wherein the second material has a greater
sound speed than the first material.
4. The liner of claim 1, wherein the first material comprises a
metal.
5. The liner of claim 1, wherein the first material is selected
from the group consisting of copper, copper alloy, aluminum,
aluminum alloy, tin, tin alloy, lead, lead alloy, powdered metal,
powdered metal within a polymeric base, and sintered metal.
6. The liner of claim 1, wherein the second material is selected
from the group consisting of copper, copper alloy, aluminum,
aluminum alloy, tin, tin alloy, lead, lead alloy, powdered metal,
powdered metal within a polymeric base, sintered metal, compacted
explosive, hardened explosive.
7. The liner of claim 1, wherein the second material is selected
from the group consisting of aluminum, copper alloy, and powdered
metal in a polymeric base.
8. The liner of claim 1 wherein: the first material comprises
copper alloy; and the second material comprises aluminum.
9. The liner of claim 1, wherein each of the first and second
components has a liner angle and wherein the second component has a
liner angle which is no more than about 15 degrees greater than the
liner angle of the first component.
10. The liner of claim 9, wherein the liner angle of the second
component is within about 15 degrees of the liner angle of the
first component.
11. The liner of claim 10, wherein the liner angle of the second
component is less than the liner angle of the first component.
12. The liner of claim 1, wherein each of the first and second
components has a liner height and wherein the liner height of the
second component is no more than about the liner height of the
first component.
13. The liner of claim 12, wherein the liner height for the second
component is less than about 2/3 of the liner height for the first
component.
14. The liner of claim 13, wherein the liner height for the second
component is between about 1/3 and 2/3 of the liner height for the
first component.
15. The liner of claim 12, wherein the liner height for the second
component is less than about 1/2 of the liner height for the first
component.
16. The liner of claim 15, wherein the liner height for the second
component is between about 1/4 and 1/2 of the liner height of the
first component.
17. The liner of claim 1, wherein the second component has an
approximately conical shape.
18. The liner of claim 1, wherein the approximate shape of the apex
of the first component is selected from the group consisting of
hemispherical, parabolic, ellipsoidal, flattened parabolic and
hyperbolic and is radially symmetric about the central axis passing
through the apex.
19. The liner of claim 1, wherein the circular skirt edge of the
first component has a diameter; the circular skirt edge of the
second component has a diameter; and, the ratio of the diameter of
the circular skirt edge of the second component to the diameter of
the circular skirt edge of the first component is between about
0.05 and about 0.35.
20. The liner of claim 19, wherein the ratio of the diameter of the
circular skirt edge of the second component to the diameter of the
circular skirt edge of the first component is between about 0.10
and about 0.25.
21. The liner of claim 1, wherein the circular skirt edge of the
second component has a diameter; and, wherein the circular skirt
edge of the second component has a diameter of between about 0.30
inches and about 0.45 inches.
22. A method for making a shaped-charge, the method comprising
forming a first liner component of a first material wherein the
first liner component has an apex and an opening at the center of
the apex; forming a second liner component of a second material
wherein the second material is not identical to the first material;
providing a housing containing explosive material; and assembling
the first component and the second component into the housing
acting together to line the explosive material wherein a portion of
the second component is within the opening at the center of the
apex of the first component.
23. The method of claim 22, wherein the action of forming the first
liner component comprises drawing the first liner component.
24. The method of claim 22, wherein the action of forming the first
liner component comprises molding the first liner component.
25. The method of claim 22, wherein the action of forming the
second liner component comprises drawing the second liner
component.
26. The method of claim 22, wherein the action of forming the
second liner component comprises molding the second liner
component.
27. The method of claim 22 wherein the first and second components
are joined.
28. The method of claim 22 wherein the first and second components
are joined before assembling the components into the housing.
29. The method of claim 22 wherein the first and second components
are joined during assembly of the components into the housing.
30. The method of claim 27, wherein the action of joining the first
and second components comprises fitting a portion of the second
component within the opening in the apex of the first
component.
31. The method of claim 30, wherein the action of fitting comprises
pressing the second component into the opening of the apex of the
first component until an interference fit is attained between the
two components.
32. The method of claim 30, wherein the second component has a
mouth and a lip around the mouth and wherein the action of fitting
comprises inserting the second component into the opening of the
apex of the first component until the lip of the second component
catches the edge of the opening of the first component.
33. The method of claim 32, wherein the apex of the first component
has a recess around the opening and wherein the lip of the second
component fits into the recess around the opening of the first
component.
34. The method of claim 30 further comprising the action of
attaching the two components at the intersection of the opening of
the apex and the portion of the second component.
35. The method of claim 34, wherein the action of attaching
comprises applying an adhesive coating.
36. The method of claim 34, wherein the action of attaching
comprises soldering.
37. The method of claim 34, wherein the action of attaching
comprises welding.
Description
FIELD OF THE INVENTION
[0001] The present invention is concerned with explosive
shaped-charges, and more particularly to an improved liner for use
in such shaped-charges, an improved shape charge which is
especially useful in a well pipe perforating gun, and a method for
making them.
BACKGROUND OF THE INVENTION
[0002] The use of shaped-charges for perforating the tubing, pipes,
or casings used to line wells such as oil and natural gas wells and
the like, is well-known in the art. For example, U.S. Pat. No.
3,128,701, issued Apr. 14, 1964 to J. S. Rinehart et al, discloses
a shaped-charge perforating apparatus for perforating oil well
casings and well bore holes.
[0003] Generally, shaped-charges utilized as well perforating
charges include a generally cylindrical or cup-shaped housing
having an open end and within which is mounted a shaped explosive
which is configured generally as a hollow cone having its concave
side facing the open end of the housing. The concave surface of the
explosive is lined with a thin metal liner which, as is well-known
in the art, is explosively driven to hydrodynamically form a jet of
material with fluid-like properties upon detonation of the
explosive and this jet of viscous material exhibits a good
penetrating power to pierce the well pipe, its concrete liner and
the surrounding earth formation. Typically, the shaped-charges are
configured so that the liners along the concave surfaces thereof
define simple conical liners with a small radius apex at a radius
angle of from about 55 degrees to about 60 degrees. Other charges
have a hemispherical apex fitted with a liner of uniform
thickness.
[0004] Generally, explosive materials such as HMX, RDX, PYX, or HNS
are coated or blended with binders such as wax or synthetic
polymeric reactive binders such as that sold under the trademark
KEL-F. The resultant mixture is cold- or hot-pressed to
approximately 90% of its theoretical maximum density directly into
the shaped-charge case. The resulting shaped-charges are initiated
by means of a booster or priming charge positioned at or near the
apex of the shaped-charge and located so that a detonating fuse,
detonating cord or electrical detonator may be positioned in close
proximity to the priming charge.
[0005] The known prior art shaped-charges are typically designed as
either deep-penetrating charges or large-diameter hole charges.
Generally, shaped-charges designed for use in perforating guns
contain 5 to 60 grams of high explosive and those designed as
deep-penetrating charges will typically penetrate concrete from 10
inches to over 50 inches. Large-diameter hole shaped-charges for
perforating guns create holes on the order of about one inch in
diameter and display concrete penetration of up to about 9 inches.
Such data have been established using API RP43, Section I test
methods.
SUMMARY OF THE INVENTION
[0006] The disclosed embodiments of the present invention addresses
a liner for a shaped-charge made up of two liner components and a
method for making a shaped-charge using such a liner. In the
preferred embodiments, each liner component has a convex outer
surface, a concave inner surface, an apex having a center, a mouth
portion of the liner component opposite the apex of the liner
component, and a skirt portion terminating in a circular skirt edge
at the mouth portion of the liner component. The first liner
component is made of a first material and has an opening at the
center of its apex. The second component is made of a second
material and a portion of the second component is within the
opening at the center of the apex of the first component.
[0007] The first material and the second material include different
materials. In one embodiment, the first material has a greater
density than the second material. In another embodiment the second
material has a greater sound speed than the first material. In the
more preferred embodiments, the first material comprises a metal
and most commonly the first material is selected from the group of
copper, copper alloy, aluminum, aluminum alloy, tin, tin alloy,
lead, lead alloy, powdered metal, powdered metal within a polymeric
base, and sintered metal. By comparison, the second material is may
be made from a similar set of materials or compacted or hardened
explosive, but more preferably comprises aluminum or copper alloy
or powdered metal in a polymeric base. In the most preferred
embodiment the first material comprises copper alloy and the second
material comprises aluminum.
[0008] In the described embodiments, each of the first and second
components has a liner angle. In the more preferred embodiment the
second component has a liner angle which is no more than about 15
degrees greater than the liner angle of the first component. In
alternative embodiments, the liner angle of the second component is
less than the liner angle of the first component. The first and
second components each also have a liner height. In the preferred
embodiments, liner height of the second component is no more than
about the liner height of the first component. The circular skirt
edges of first and second components each have a diameter. In the
presently most preferred embodiment the circular skirt edge of the
second component has a diameter of between about 0.30 inches and
about 0.45 inches. It is also preferred that the ratio of the
diameter of the circular skirt edge of the second component to the
diameter of the circular skirt edge of the first component is
between about 0.05 and about 0.35 and more preferably between about
0.10 and about 0.25.
[0009] The more preferred shape for the second component is an
approximately conical shape. The more preferred approximate shapes
for the first component are selected from the group consisting of
hemispherical, parabolic, ellipsoidal, flattened parabolic, and
hyperbolic. For both it is highly preferred that each component be
radially symmetric about the central axis passing through the
apex.
[0010] The present disclosure also addresses a method for making a
shaped-charge. The preferred method starts by forming a first liner
component of a first material wherein the first liner component has
an apex and an opening at the center of the apex. A second liner
component is formed of a second material wherein the second
material is not identical to the first material. A housing is
provided which contains explosive material. The first component and
the second component are assembled into the housing acting together
to line the explosive material. The components are assembled so
that a portion of the second component is within the opening at the
center of the apex of the first component.
[0011] In various embodiments, the action of forming the liner
components may comprise drawing or molding the liner components
among a number of possible forming methods. In the most preferred
embodiments, the two liner components are joined, although they may
be joined before, during, or even after assembly into the
housing.
[0012] The action of joining may include fitting a portion of the
second component within the opening in the apex of the first
component. This may involve pressing the second component into the
opening of the apex of the first component until an interference
fit is attained between the two components. In an alternative
embodiment, the second component could have a lip around its mouth,
in which case the action of fitting would include inserting the
second component into the opening of the apex of the first
component until the lip of the second component catches the edge of
the opening of the first component. In another alternative, the
first component could also have a recess around the opening and the
lip of the second component could fit into the recess around the
opening in the apex of the first component.
[0013] Finally, in the preferred embodiments the two components may
be attached at the intersection of the opening of the apex and the
portion of the second component. Attaching could be accomplished by
applying an adhesive coating, by soldering, by welding, or by other
methods disclosed herein. These forms of attachment could be
accomplished alone or in combination with each other and could
occur before, during, or after assembly into the shaped-charge.
DESCRIPTION OF THE DRAWINGS
[0014] The invention, together with further advantages thereof, may
best be understood by reference to the following description taken
in conjunction with the accompanying drawings in which:
[0015] FIG. 1 is a cross-sectional diagram illustrating an
assembled shaped-charge including a primary liner having a
flattened parabolic apex with a conical precursor liner.
[0016] FIG. 2 is a cross-sectional diagram illustrating an
assembled shaped-charge including a primary liner having a
hemispherical apex with a conical precursor liner.
[0017] FIG. 3 is a cross-sectional diagram illustrating a
flat-bottom cone primary liner having a flattened parabolic apex
with a conical precursor liner.
[0018] FIG. 4 is a cross-sectional diagram illustrating a hemi-cone
primary liner having a hemispherical apex with a conical precursor
liner.
[0019] FIG. 5 is a cross-sectional diagram illustrating an
assembled shaped-charge including a primary liner having a
hemispherical apex with a larger conical precursor liner.
[0020] FIG. 6 is a cross-sectional diagram illustrating an
ellipsoidal primary liner with a conical precursor liner.
[0021] FIG. 7 is a cross-sectional diagram illustrating an
assembled shaped-charge including a flat-bottom cone primary liner
having a flattened parabolic apex with a hemispherical precursor
liner.
DETAILED DESCRIPTION
[0022] One factor influencing performance of shaped-charges in
large well bores is the presence of fluid in the annulus between
the perforating gun carrying the charges and the casing. The
presence of fluid in this area significantly affects the formation
of the jet tip, particularly in "big hole" perforators, but also in
perforators in general (where shaped-charges are the perforators or
perforating devices carried on the perforating guns). The fluid has
a mushrooming effect on the jet tip which causes it to create a
large entry hole in the first string of casing. While this may be
desirable for single string completions where big holes are sought,
there are situations where wells are completed in zones with
multiple strings of casings, or it is necessary to establish fluid
communication through multiple strings. When this situation occurs,
it is desirable to obtain a large hole in all of the casing
strings. Having fluid in the annulus makes this more difficult,
because the mushroomed jet tip expends most of its energy getting
through the fluid and creating a large hole in the first string,
and there is very little energy left to perforate subsequent
strings.
[0023] The present disclosure suggests a method to remove well bore
fluid from the path of a shaped-charge jet in order to reduce the
effect it has on the jet tip. The reduction of the mushrooming
effect caused by the fluid enables the shaped-charge designer to
spread out the jet's energy so that it can be used more effectively
to create large holes through multiple strings of casing when
shooting across fluid gaps. The shaped-charge designer may
alternatively be able to create a larger hole in a single string
when shooting across fluid gaps or even a deeper penetration of the
formation after shooting across fluid gaps. This is most preferably
accomplished by using a precursor liner and a primary liner both
pressed in the same housing. In the most preferred embodiment, the
primary liner is similar or equivalent to a standard big hole
shaped charge liner. The precursor liner is pressed into the
booster end (or apex end) of the primary liner to form an initial
very fast moving jet to open a path through the fluid of the well
bore annulus. The jet from the primary liner moves at a slower rate
of speed and thus follows the path made through the fluid by the
precursor resulting in reduced effects from the well bore
fluid.
[0024] A particular class of big hole liner incorporates the use of
an opening, preferably circular, at the center of the apex of the
liner. The opening at the apex is especially useful in "big hole"
applications, as it enhances entrance hole performance, although
there typically is a trade off in terms of loss of penetration.
When assembled in a shaped-charge under the present disclosure, the
primary liner has the apex opening, and the precursor liner is fit
within the apex opening. The precursor liner and primary liner may
also be viewed as components of a single overall shaped-charge
liner which are joined together by any of a number of means. The
liners are in theory usable separately, but when placed together in
the shaped-charge act together to line the explosive charge. The
two liners (or liner components as they are also referred to
herein) most typically interact at the apex opening of the primary
liner.
[0025] A number of potential approaches may be used to join the two
liner components at the apex opening. One preferred method involves
the use of an interference fit between the mouth of the precursor
liner and the walls of the opening in the primary liner. Another
method could involve the addition of a lip to the mouth of the
precursor liner such that the lip is too large to pass through the
apex opening in the primary liner, while the rest of the precursor
liner is able to pass through. The precursor liner could also sit
atop the primary liner. This could be done by forming a recess in
the top of the convex outer portion of the main liner and setting
the precursor liner in the recess. In this instance, "glue" could
again be used to keep the precursor liner in place or the
confinement/compression between the explosive powder and the
primary liner could be the fixing mechanism. An additional
alternative could employ welding or soldering the border between
the precursor liner and the primary liner.
[0026] In an alternative embodiment, the precursor liner may not be
pressed all the way onto the primary liner, leaving a portion of
the precursor liner extending above the opening in the primary
liner. One approach to this alternative would be to have an
interference fit where the mouth of the precursor liner is somewhat
larger than the opening in the apex of the primary liner such that
as the precursor liner is pressed in the two are interference fit
at a circumference of the precursor liner below the mouth of the
precursor liner. Alternatively the precursor liner could be
inserted to the desired point and one of the other attachment
methods described above or below could be used to join the two
components together into the overall liner.
[0027] The most preferred approach is to have a close fit (without
being an interference fit) and applying an adhesive coating to keep
the two components of the overall liner (individually the primary
liner and the precursor liner) together. The coating is most
preferably an adhesive/paint sold under the trademark Glyptol,
preferably an adhesive selected from an epoxy material compatible
with the explosive material, and generally comprises an adhesive.
The coating may be a single layer either of adhesive alone or
adhesive in combination with graphite. The coating may also be more
than one layer, with a layer as described above and additional
layers contributing to other properties, such as improving the
moisture barrier characteristics, or improving the slight amount of
time the coating acts as to dynamically confine the explosive gases
which are the product of detonation. The coating as a whole is
preferably no more than twice the thickness of the liner around the
opening in the apex, more preferably less than or about the
thickness of the liner around the opening of the apex, and most
preferably between about 5-10% of the thickness of the liner around
the opening of the apex. This tends to place the thickness of the
coating within the range of about 0.002 inches to about 0.05
inches. The coating may also be employed even when other methods
should maintain relative position (such as the use of a lip or
interference fit or other methods understood by those of skill in
the art). In this case the adhesive properties of the coating may
provide additional assistance, and the coating may also help to
improve the seal between the liners, preventing potential salting
out of explosive material through the component interface (the
interface between the primary liner component and the precursor
liner component).
[0028] The primary liner component is preferably made from a metal
strip or sheet, more preferably from a metal selected from the
group of copper, copper alloy, aluminum, aluminum alloy, tin, tin
alloy, lead, and lead alloy, and most preferably made of copper
alloy. In alternative processes, the liner may be made from a
powdered metal within a polymeric base which is molded (for example
injection molded) into the form of a liner. The liner could also be
made from a sintered metal, possibly with other material
components, which is cast or molded into a desired shape. These
alternative processes would typically be manufactured using a
molding or casting process.
[0029] The precursor liner component may be made from similar
materials and using similar processes. However, in the preferred
embodiment, the precursor liner is made from a material which is
less dense than the material used in the primary liner component.
Alternatively, the precursor liner component may be made from a
material with a greater sound speed, where the sound speed is the
speed at which an acoustic shockwave travels through the liner
material. In either event, these properties assist the precursor
liner in traveling more quickly than the primary liner following
the detonation of the charge. This helps to promote the travel of
the jet formed by the precursor liner into the fluid preceding the
jet formed by the primary liner. A preferred material for the
precursor liner component is aluminum, but a lighter brass or even
a CLG-80 powdered metal are preferred alternative materials.
Another less preferred alternative would involve making the
precursor liner out of a hardened or compacted explosive. This
could create an exploding precursor jet to push a path through the
fluid. It might also have a lower density or higher sound speed
than the primary liner component. For either liner component, when
the word material is used in the present disclosure it is intended
to refer to blends and composites as well as more simple elemental
materials. Basically, it represents the stuff out of which a liner
component is formed.
[0030] The preferred method for making the liner components calls
for drawing the chosen material (preferably from a flat state) into
a concave shape radially symmetric about a central axis passing
through and perpendicular to the center of the apex, where radial
symmetry about an axis is intended to describe concentricity about
such axis within any plane defined perpendicular to such axis and
intersecting such axis. In this process the center of the material
is drawn down to form the apex while the perimeter of the material
forms a skirt portion terminating in a circular skirt edge at the
mouth of the liner. Depending on the desired apex shape and other
factors, the draw may be done in a single step or may be done in
several steps. For a hemispherical apex, a single step draw is
preferable. The drawing process may result in creation of a slight
necking point in the material, where the thickness is slightly
reduced generally in the area near the transition from the skirt
portion to the apex portion of the liner. Multiple step draws tend
to leave several necking points near each radial transition, but
these are generally smaller and less well defined. Multiple step
draws are preferable when the desired apex profile is parabolic
such as the more complex flattened parabolic apex described in this
disclosure.
[0031] The primary liner component will typically use an opening in
the apex to locate and/or hold the precursor liner component.
Preferably, a punch is used to punch the opening in the apex
centered on the central axis. This preferably occurs in the same
sequence as the drawing process to increase reliability of the
central axis for the punch being identical to the central axis for
the draw. Other alternatives to the use of a punch to create the
hole include drilling, honing, sawing, or chemically etching.
[0032] The draw is preferably done from a sheet of material, but
may also be performed on pre-cut and sized discs or other shaped
blanks. At the conclusion of the draw, either preferably as a final
step in the drawing process using the drawing tools, or as a
separate step, any excess flat material from the sheet or blank
outside of the circular skirt edge forming the mouth of the liner
must be removed. Additionally, in some embodiments, following
removal of any excess flat material, an additional step may be
undertaken to trim the height of the liner to a desired size.
[0033] In an alternative method of manufacture, the liner
components of the present invention may be manufactured by spinning
a sheet of material into a concave shape radially symmetric about a
central axis, having an apex centered on the central axis and a
mouth at the opposite end from the apex, wherein a portion of the
material forms the apex and a portion of the material forms a skirt
portion terminating in a circular skirt edge at the mouth of the
liner. Following the spinning process there must be a removal of
any excess material outside the circular skirt edge forming the
mouth. Where an opening in the apex is desired, this may be
accomplished by the use of a punch or drill, after the completion
of the spinning process. Other methods of manufacture may also be
contemplated by those of skill in the art as appropriate to the
material of choice, such as sintering, casting, molding,
compositeing, and the like.
[0034] FIG. 1 is a cross-sectional diagram illustrating one
specific embodiment of the present invention. FIG. 1 is a
cross-section of a shaped-charge 10 having a primary liner 50 with
a flattened parabolic apex 54 and a precursor liner 70 with a
conical apex 74. The shaped-charge 10 includes a housing 12 having
an outer wall 14, an inner wall 16, a base 18, and a mouth 20
opposite the base 18. Within the housing is contained a shaped
explosive 28 mounted on the inner wall 16 of the housing 12 and
having an open concave side facing the mouth 20 (or mouth portion)
of the housing.
[0035] The housing 12 also contains a chamber 22 to hold an
initiation charge 24. The initiation charge 24 preferably is
actually larger than chamber 22 and flows into the area housing the
main shaped explosive 28. In the illustrated embodiment, the
initiation charge actually overlaps the precursor liner. One
alternative may modify the shape of the standard shaped-charge
housing to allow sufficient initiation charge without having the
charge overlap the precursor liner.
[0036] One of the simpler approaches to change the position of the
initiation charge is to angle the cavity where the initiation
charge generally sits while preserving the minimum diameter. This
would bring the initiation charge line away from the precursor
liner. In addition increasing the angle of the inner wall of the
case above the cavity by increasing the minimum diameter would also
lower the initiation charge line. Another way to change the level
is by manipulating how much powder is actually poured into the
charge. Finally, a two-step pressing process could be employed in
which the initiation charge is shaped to reflect the conical (or
other) shape of the precursor liner. During this pressing the shape
could potentially be offset to allow some amount of air or
preferably some amount of the main explosive to be between the
initiation charge and the precursor liner. While an alternative, it
may be less desirable to pre-form the initiation charge after it
was poured into the case due to the additional process steps and
complexity of manufacture.
[0037] The initiation charge 24 is triggered by an explosive
member, preferably a linear explosive member linking and initiating
several shaped-charges, contained at least in part within primer
container 26 attached to the base 18 of housing 12.
[0038] The primary shaped-charge liner component 50 (also referred
to as the primary liner) has a concave inner surface 51, a convex
outer surface 52, an apex 54 (or apex portion), and a mouth
opposite the apex 54 (illustrated here contiguous to mouth 20 of
housing 12). The apex 54 has a center at a point where the apex 54
intersects the central axis 53 about which the shaped-charge liner
is radially symmetric. The embodiment illustrated in FIG. 1 further
includes an opening 56 at the center of the apex 54. The liner 50
also includes a skirt portion 60 terminating in a circular skirt
edge 62 at the mouth of the liner on the opposite end of the liner
from the apex 54. The liner 50 lines the concave side of the shaped
explosive 28 leaving an open space 30 between the concave inner
surface 51 of the liner and the mouth 20 of the housing.
[0039] The precursor shaped-charge liner component 70 (also
referred to as the precursor liner) has a concave inner surface 71,
a convex outer surface 72, an apex 74 (or apex portion), and a
mouth opposite the apex 74 (illustrated here contiguous to opening
56 of primary liner 50). The apex 74 has a center at a point where
the apex 74 intersects the central axis 53 about which both the
primary liner 50 and the precursor liner 70 are radially symmetric.
The precursor liner 70 also includes a skirt portion 80 terminating
in a circular skirt edge 82 at the mouth of the liner on the
opposite end of the liner from the apex 74. The combined liner
components 50 and 70 work together to line the concave side of the
shaped explosive 28 leaving an open space 30 between the concave
inner surface 51 of the primary liner and the mouth 20 of the
housing.
[0040] The main shaped explosive 28 is bounded by the housing inner
wall 16, the initiation charge 24, the convex outer surface 52 of
the primary liner 50, and the convex outer surface 72 of the
precursor liner 70.
[0041] In the embodiment illustrated in FIG. 1, the primary liner
50 is drawn multiple steps. The transition between the skirt
portion 60 and the apex portion 54 of the liner 50 is roughly
defined as the transition from a straighter, although not
necessarily completely straight, skirt section 60 from the skirt
edge 62 of the liner 50 to the more curved (having a shorter radius
of curvature) apex portion 54 of the liner 50. With the more
complex curve of this embodiment, the transition is a transition
region of gradually decreasing radius of curvature, which may
decrease stepwise or in an approximately curvilinear fashion. In a
simpler curved liner such as FIG. 2 below, the primary liner may be
drawn in a single step and have a necking point near the transition
between the skirt portion and the apex portion of the liner. For
the embodiment of FIG. 1, the transition between the skirt portion
60 and the apex portion 54 of the liner 50 is roughly defined as
the transition from a straighter, although not necessarily
completely straight, skirt section 60 from the skirt edge 62 of the
liner 50 to the more curved (having a shorter radius of curvature)
apex portion 54 of the liner 50. With a more complex curve, the
transition is a transition region of gradually decreasing radius of
curvature, which may decrease stepwise or ideally in a curvilinear
fashion. The transition point 64 identified in the drawing of FIG.
1 is illustrative, but is not intended to be correct to scale.
[0042] For the purposes of this disclosure a "liner angle" may be
defined for a liner component. If a section is taken on a plane
through a liner or liner component which includes the central axis
and intersects the apex of the liner and a straight line is drawn
tangential to the skirt portion of the liner on each side. The
lines should intersect at a point below the apex of the liner (or
exactly at the apex of the liner in the case of a perfect cone) and
define an angle between them. This angle represents the liner angle
for the liner or liner component.
[0043] For the embodiment described in FIG. 1, the liner angle for
the primary component is preferably within the range of 10 degrees
to 150 degrees, more preferably within the range of 35 degrees to
75 degrees, and most preferably within the range of 50 degrees to
55 degrees. For the embodiment described in FIG. 1, the liner angle
for the precursor component is preferably within the range of 10
degrees to 150 degrees, more preferably within the range of 20
degrees to 75 degrees, and most preferably within the range of 35
degrees to 55 degrees. It is also preferable that the liner angle
for the precursor liner be no more than 15 degrees more than the
liner angle for the primary liner. It is more preferable that the
liner angle for the precursor liner be between about 15 degrees
less and about 5 degrees more than the liner angle for the primary
liner. In the present described embodiment, it is most preferable
that the liner angle for the precursor liner be less than the liner
angle for the primary liner. Similar to the deep-penetrating
advantages provided by conical liners over the more curvilinear big
hole liners, it is believed that steeper liners (smaller liner
angles) for the precursor liners will travel faster thus helping to
promote the travel of the jet formed by the precursor liner into
the fluid preceding the jet formed by the primary liner.
[0044] For the purposes of this disclosure a "liner height" may be
defined for a liner component. If measurement is taken along the
central axis from the opening or lowest apex of the liner component
to the point on the axis where a plane defined by the circular
skirt edge of the liner intersects the axis, this measurement
represents the liner height for the liner or liner component.
[0045] For the embodiment described in FIG. 1, the liner height for
the primary component is preferably within the range of 0.25 inches
to 3.0 inches, more preferably within the range of 0.5 inches to
2.0 inches, and most preferably within the range of 0.75 to 1.25
inches. For the embodiment described in FIG. 1, the liner height
for the precursor component is preferably within the range of 0.125
inches to 1.5 inches, more preferably within the range of 0.125
inches to 0.5 inches, and most preferably within the range of 0.2
inches to 0.4 inches. These represent specific heights for a
specific embodiment, but as is understood by those of skill in the
art, charges may be scaled up or down depending on the proposed or
desired end use. There are also preferred ratios for the height of
the liners. It is preferable that the liner height for the
precursor liner be less than 1/2 the liner height for the primary
liner. It is more preferable that the liner height for the
precursor liner be less than about 1/3 of the liner height for the
primary liner, and most preferable that the liner height for the
precursor liner be between 1/5 and 1/3 of the liner height for the
primary liner.
[0046] FIG. 2 is a cross-sectional diagram illustrating a distinct
specific embodiment of the present invention. FIG. 2 is a
cross-section of a shaped-charge 110 having a primary liner 150
with a hemispherical apex 154 and a precursor liner 170 having a
conical apex 174. The shaped-charge 110 includes a housing 112
having an outer wall 114, an inner wall 116, a base 118, and a
mouth 120 opposite the base 118. Within the housing is contained a
shaped explosive 128 mounted on the inner wall 116 of the housing
112 and having an open concave side facing the mouth 120 (or mouth
portion) of the housing.
[0047] The housing 112 also contains a chamber 122 to hold an
initiation charge 124. The initiation charge 124 is triggered by an
explosive member contained at least in part within primer container
126 attached to the base 118 of housing 112.
[0048] The primary shaped-charge liner 150 has a concave inner
surface 151, a convex outer surface 152, an apex 154 (or apex
portion), and a mouth opposite the apex 154 (illustrated here
contiguous to mouth 120 of housing 112). The apex 154 has a center
at a point where the apex 154 intersects the central axis 153 about
which the shaped-charge liner is radially symmetric. The embodiment
illustrated in FIG. 2 further includes an opening 156 at the center
of the apex 154. The liner 150 also includes a skirt portion 160
terminating in a circular skirt edge 162 at the mouth of the liner
on the opposite end of the liner from the apex 154. The liner 150
lines the concave side of the shaped explosive 128 leaving an open
space 130 between the concave inner surface 151 of the liner and
the mouth 120 of the housing.
[0049] The precursor shaped-charge liner 170 has a concave inner
surface 171, a convex outer surface 172, an apex 174 (or apex
portion), and a mouth opposite the apex 174 (illustrated here
contiguous to opening 156 of primary liner 150). The apex 174 has a
center at a point where the apex 174 intersects the central axis
153 about which both the primary liner 150 and the precursor liner
170 are radially symmetric. The precursor liner 170 also includes a
skirt portion 180 terminating in a circular skirt edge 182 at the
mouth of the liner on the opposite end of the liner from the apex
174. The combined liner components 150 and 170 line the concave
side of the shaped explosive 128 leaving an open space 130 between
the concave inner surface 151of the primary liner and the mouth 120
of the housing.
[0050] The shaped explosive 128 is bounded by the housing inner
wall 116, the initiation charge 124, the convex outer surface 152
of the primary liner 150, and the convex outer surface 172 of the
precursor liner 170.
[0051] For the embodiment described in FIG. 2, the liner angle for
the primary component is preferably within the range of 10 degrees
to 150 degrees, more preferably within the range of 35 degrees to
65 degrees, and most preferably within the range of 42 degrees to
47 degrees. For the embodiment described in FIG. 2, the liner angle
for the precursor component is preferably within the range of 10
degrees to 150 degrees, more preferably within the range of 20
degrees to 90 degrees, and most preferably within the range of 20
degrees to 50 degrees. For this embodiment and some other
embodiments, it is also preferable that the liner angle for the
precursor liner be no more than 15 degrees more than the liner
angle for the primary liner. It is more preferable that the liner
angle for the precursor liner be between about 15 degrees less and
about 10 degrees more than the liner angle for the primary
liner.
[0052] For the embodiment described in FIG. 2, the liner height for
the primary component is preferably within the range of 0.25 inches
to 3.0 inches, more preferably within the range of 0.5 inches to
2.0 inches, and most preferably within the range of 1.0 inches to
1.35 inches. For the embodiment described in FIG. 2, the liner
height for the precursor component is preferably within the range
of 0.125 inches to 1.5 inches, more preferably within the range of
0.125 inches to 0.5 inches, and most preferably within the range of
0.2 inches to 0.4 inches. These represent specific heights for a
specific embodiment, but as is understood by those of skill in the
art, charges may be scaled up or down depending on the proposed or
desired end use. There are also preferred ratios for the height of
the liners. With the embodiment of FIG. 2 in mind, it is preferable
that the liner height for the precursor liner be less than 2/3 the
liner height for the primary liner. It is more preferable that the
liner height for the precursor liner be less than 1/2 of the liner
height for the primary liner, and most preferable that the liner
height for the precursor liner be between 1/4 and 1/2 of the liner
height for the primary liner.
[0053] The liner illustrated in FIG. 3 is made up of a relatively
straight conical section in the skirt transitioning into a
flattened parabolic apex, where the apex comprises a flattened
parabola that is radially symmetric about the central axis passing
through the center of the apex. The parabolic apex is blended in a
curvilinear fashion to a simple truncated conical section that
extends to the opening of the case. This type of liner allows an
increased standoff for the parabolic section while minimizing the
amount of explosive material necessary to fill the case. The
conical section allows this standoff while maintaining a solid
boundary between the explosive and the cavity within the
shaped-charge. The precursor liner illustrated is approximately a
simple cone where the mouth of the precursor liner is contiguous to
the opening in the apex of the primary liner. The various methods
of coupling the two liner components at or about the opening in the
primary liner are addressed above and equally apply for this
embodiment.
[0054] In the described example of FIG. 3, the opening at the
center of the apex of the primary liner has a diameter of about
0.375 inches and the circular skirt edge has a diameter of about
1.9 inches. In this example the ratio of the diameter of the
opening to the diameter of the circular skirt edge is about 0.2.
Preferably the ratio of the diameter of the opening to the diameter
of the circular skirt edge is between about 0.05 and about 0.35 and
more preferably the ratio of the diameter of the opening to the
diameter of the circular skirt edge is between about 0.10 and about
0.25. In the specific examples disclosed herein the opening at the
center of the apex preferably has a diameter of between about 0.30
inches and about 0.45 inches. In the preferred embodiment, this
ratio equally applies to the ratio of the diameter of the circular
skirt edge of the mouth of the precursor liner to the circular
skirt edge of the mouth of the primary liner.
[0055] In the described example of FIG. 4, the opening at the
center of the apex of the primary liner has a diameter of about
0.36 inches and the circular skirt edge has a diameter of about
2.45 inches. In this example the ratio of the diameter of the
opening to the diameter of the circular skirt edge is about 0.15.
Similarly the ratio of the diameter of the circular skirt edge of
the mouth of the precursor liner to the circular skirt edge of the
mouth of the primary liner is about 0.15. In both FIG. 3 and FIG.
4, the size of the opening in the apex also approximates the size
of the mouth of the precursor liner and thus the ratio of the mouth
of the primary liner to the apex opening of the primary liner
approximates the ratio of the mouth of the primary liner to the
mouth of the precursor liner.
[0056] The hemi-cone primary liner illustrated in FIG. 4 allows a
larger apex and tends to distribute more explosive material
directly behind the apex section. Again, the embodiment illustrated
in FIG. 4 incorporates a simple cone for the precursor liner.
[0057] In one alternative embodiment illustrated in FIG. 5, it may
be desirable to have a more substantial precursor component
resulting in a larger apex opening in the primary liner and
corresponding larger mouth in the precursor liner. Similarly, the
relative liner heights of the two liners may also approach one end
of the most preferred spectrum.
[0058] For the embodiment described in FIG. 5, the liner angle for
the primary component is preferably within the range of 10 degrees
to 150 degrees, more preferably within the range of 35 degrees to
65 degrees, and most preferably within the range of 42 degrees to
47 degrees. For the embodiment described in FIG. 5, the liner angle
for the precursor component is preferably within the range of 10
degrees to 150 degrees, more preferably within the range of 30
degrees to 100 degrees, and most preferably within the range of 40
degrees to 60 degrees. For this embodiment and some other
embodiments, it is also preferable that the liner angle for the
precursor liner be no more than 15 degrees more than the liner
angle for the primary liner. It is more preferable that the liner
angle for the precursor liner be between about 15 degrees less and
about 15 degrees more than the liner angle for the primary liner
(within about 15 degrees of the liner angle for the primary
liner).
[0059] For the embodiment described in FIG. 5, the liner height for
the primary component is preferably within the range of 0.25 inches
to 3.0 inches, more preferably within the range of 0.5 inches to
2.0 inches, and most preferably within the range of 1.0 inches to
1.35 inches. For the embodiment described in FIG. 5, the liner
height for the precursor component is preferably within the range
of 0.125 inches to 1.5 inches, more preferably within the range of
0.25 inches to 1.0 inches, and most preferably within the range of
0.6 inches to 0.8 inches. These represent specific heights for a
specific embodiment, but as is understood by those of skill in the
art, charges may be scaled up or down depending on the proposed or
desired end use. There are also preferred ratios for the height of
the liners. With the embodiment of FIG. 5 in mind, it is preferable
that the liner height for the precursor liner be less than the
liner height for the primary liner. It is more preferable that the
liner height for the precursor liner be less than 2/3 of the liner
height for the primary liner, and most preferable that the liner
height for the precursor liner be between 1/3 and 2/3 of the liner
height for the primary liner.
[0060] In the described example of FIG. 5, the opening at the
center of the apex of the primary liner has a diameter of about
0.675 inches and the circular skirt edge has a diameter of about
2.45 inches. In this example the ratio of the diameter of the
opening to the diameter of the circular skirt edge is about 0.275.
Similarly the ratio of the diameter of the circular skirt edge of
the mouth of the precursor liner to the circular skirt edge of the
mouth of the primary liner is about 0.275. Preferably the ratio of
the diameter of the opening to the diameter of the circular skirt
edge is between about 0.10 and about 0.45 and more preferably the
ratio of the diameter of the opening to the diameter of the
circular skirt edge is between about 0.20 and about 0.35.
[0061] While the embodiments particularly addressed above reflect
the use of an approximately hemispherical apex liner and of a
flattened parabolic apex liner as primary liners, one of skill in
the art will recognize that the benefits of the proposed invention
could also apply in other shapes of liners, for example simple
conical liners, slightly modified conical liners which take the
form of ellipsoids (partial 3-dimensional ellipses) or have
ellipsoidal apexes (for example the primary and precursor liner
illustrated in FIG. 6), liners with hyperbolic apexes, liners with
truncated apexes, other shapes familiar to those of skill in the
art. For any of the shapes described herein, when an apex is
described as having a particular shape it is recognized that the
shape is approximate and may involve some degree of eccentricity,
deviation, or transitioning, both as a matter of design and as a
matter of manufacture. The shape is intended to provide insight
into the basic pattern being followed and is not intended to be a
precise description of the physical outcome. In any event, the
liners are preferably radially symmetric about the central axis
passing through the center of the apex. While the disclosure herein
refers to concave and convex surfaces to describe the general
orientation of the surface within the context of the object, the
use of convex and concave are not intended to imply a requirement
that the surface be smooth or curvilinear.
[0062] Returning to the embodiment described in FIG. 6, (briefly
introduced above) the liner angle for the primary component is
preferably within the range of 10 degrees to 150 degrees, more
preferably within the range of 25 degrees to 55 degrees, and most
preferably within the range of 37 degrees to 43 degrees. For the
embodiment described in FIG. 6, the liner angle for the precursor
component is preferably within the range of 10 degrees to 150
degrees, more preferably within the range of 20 degrees to 75
degrees, and most preferably within the range of 35 degrees to 55
degrees. For this embodiment and some other embodiments, it is also
preferable that the liner angle for the precursor liner be no more
than 15 degrees more than the liner angle for the primary liner. It
is more preferable that the liner angle for the precursor liner be
within about 15 degrees of the liner angle for the primary
liner.
[0063] For the embodiment described in FIG. 6, the liner height for
the primary component is preferably within the range of 0.25 inches
to 3.0 inches, more preferably within the range of 0.75 inches to
2.0 inches, and most preferably within the range of 1.20 inches to
1.50 inches. For the embodiment described in FIG. 6, the liner
height for the precursor component is preferably within the range
of 0.125 inches to 1.5 inches, more preferably within the range of
0.125 inches to 0.5 inches, and most preferably within the range of
0.2 inches to 0.4 inches. These represent specific heights for a
specific embodiment, but as is understood by those of skill in the
art, charges may be scaled up or down depending on the proposed or
desired end use. There are also preferred ratios for the height of
the liners. With the embodiment of FIG. 6 in mind, it is preferable
that the liner height for the precursor liner be less than 1/2 the
liner height for the primary liner. It is more preferable that the
liner height for the precursor liner be less than about 1/3 of the
liner height for the primary liner, and most preferable that the
liner height for the precursor liner be between 1/5 and 1/3 of the
liner height for the primary liner.
[0064] In the described example of FIG. 6, the opening at the
center of the apex of the primary liner has a diameter of about
0.375 inches and the circular skirt edge has a diameter of about
2.50 inches. In this example the ratio of the diameter of the
opening to the diameter of the circular skirt edge is about 0.15.
Similarly the ratio of the diameter of the circular skirt edge of
the mouth of the precursor liner to the circular skirt edge of the
mouth of the primary liner is about 0.15. Preferably the ratio of
the diameter of the opening to the diameter of the circular skirt
edge is between about 0.05 and about 0.35 and more preferably the
ratio of the diameter of the opening to the diameter of the
circular skirt edge is between about 0.10 and about 0.25.
[0065] While the precursor liners shown in the examples have been
simple cones, more complex shapes could be employed as described
above or as illustrated in FIG. 7. Alternatively, even a simple
button or disk could be employed for the precursor liner, however,
such an instance makes particularly favorable the choice of a
material for such liner which is less dense or has a greater sound
speed than the material making up the primary liner.
[0066] The embodiments addressed above involve an open
shaped-charge, i.e. one without a cover. This type of shaped-charge
is typically used within a perforating gun or tubing, which
provides protection from direct exposure to the downhole pressure
and environment. Alternative shaped-charges have covers that
cooperate with the housing to protect each individual charge from
direct exposure to the downhole environment. While not specifically
addressed here, the benefits of the present invention would equally
apply to such covered charges, as would be recognized by one of
skill in the art.
[0067] Although only a few embodiments of the present invention
have been described, it should be understood that the present
invention may be embodied in many other specific forms without
departing from the spirit or the scope of the present invention.
Therefore, the present examples are to be considered as
illustrative and not restrictive, and the invention is not to be
limited to the details given herein, but may be modified within the
scope of the appended claims along with their full scope of
equivalents.
* * * * *