U.S. patent application number 11/395556 was filed with the patent office on 2007-10-04 for shaped charges, lead-free liners, and methods for making lead-free liners.
Invention is credited to Richard Palmateer.
Application Number | 20070227390 11/395556 |
Document ID | / |
Family ID | 38556970 |
Filed Date | 2007-10-04 |
United States Patent
Application |
20070227390 |
Kind Code |
A1 |
Palmateer; Richard |
October 4, 2007 |
Shaped charges, lead-free liners, and methods for making lead-free
liners
Abstract
A liner for a shaped charge may consist essentially of dendritic
copper powder compressed under sufficient pressure to cause the
dendritic copper powder to behave as a nearly solid mass. A shaped
charge may include a housing and a quantity of explosive provided
in the housing. A liner is positioned in the housing so that the
explosive is located between the liner and the housing. The liner
is compressively formed from a mixture of dendritic copper powder
and a lubricant, the mixture comprising from about 90 percent by
weight to less than 100 percent by weight dendritic copper powder
and from more than 0 percent by weight to about 10 percent by
weight lubricant.
Inventors: |
Palmateer; Richard; (Oro
Valley, AZ) |
Correspondence
Address: |
FENNEMORE CRAIG, P.C.
1700 Lincoln Street
SUITE 2625
DENVER
CO
80203
US
|
Family ID: |
38556970 |
Appl. No.: |
11/395556 |
Filed: |
March 31, 2006 |
Current U.S.
Class: |
102/476 |
Current CPC
Class: |
F42B 1/032 20130101 |
Class at
Publication: |
102/476 |
International
Class: |
F42B 12/00 20060101
F42B012/00 |
Claims
1. A liner for a shaped charge consisting essentially of a mixture
of dendritic copper powder and a lubricant compressed under
sufficient pressure to cause said mixture to behave as a nearly
solid mass.
2. The liner of claim 1, wherein said lubricant comprises one or
more selected from the group consisting essentially of graphite and
lithium stearate.
3. The liner of claim 1, wherein said mixture comprises from about
90 percent by weight to less than 100 percent by weight dendritic
copper powder and from more than 0 percent by weight to about 10
percent by weight lubricant.
4. The liner of claim 1, wherein said mixture comprises about 98
percent by weight dendritic copper and about 2 percent by weight
lubricant.
5. The liner of claim 1, further comprising less than about 5
weight percent metal powder additive, said metal powder additive
comprising one or more selected from the group consisting
essentially of molybdenum and tungsten.
6. The liner of claim 1, wherein said dendritic copper powder
comprises electrolytically-deposited copper powder.
7. A method for producing a liner for a shaped-charge explosive,
comprising: providing a mixture consisting essentially of dendritic
copper powder and a lubricant; and compressing said mixture under
sufficient pressure to cause said mixture to behave as a nearly
solid mass.
8. The method of claim 7, wherein said compressing comprises a cold
compaction process.
9. The method of claim 7, wherein said compressing comprises hot
isostatic pressing.
10. The method of claim 7, wherein said compressing comprises cold
isostatic pressing.
11. The method of claim 7, wherein said compressing comprises
applying to the mixture a pressure of about 30 tsi.
12. The method of claim 11, wherein said compressing imparts to
said liner a green strength in a range of about 3800 psi to about
5000 psi.
13. The method of claim 11, wherein said compressing imparts to
said liner a green density in a range of about 7 g/cc to about 8
g/cc.
14. The method of claim 7, wherein providing a mixture further
comprises: providing a supply of dendritic copper powder; providing
a supply of lubricant; mixing together a portion of said supply of
dendritic copper power and a portion of said supply of lubricant to
produce said mixture.
15. The method of claim 14, wherein mixing together further
comprises mixing from about 90 percent by weight to less than 100
percent by weight said dendritic copper powder and from more than 0
percent by weight to about 10 percent by weight said lubricant.
16. The method of claim 14, wherein mixing together further
comprises mixing about 98 percent by weight said dendritic copper
powder and about 2 percent by weight said lubricant.
17. The method of claim 14, wherein mixing together further
comprises mixing about 99 percent by weight said dendritic copper
powder and about 1 percent by weight said lubricant.
18. The method of claim 14, wherein providing a supply of dendritic
copper powder comprises providing a supply of electrolytically
deposited copper powder, and wherein providing a supply of
lubricant comprises providing a supply of lubricant comprising one
or more selected from the group consisting of lithium stearate and
graphite.
19. A liner for a shaped charge comprising at least 70% by weight
dendritic copper powder.
20. The liner of claim 19, further comprising a lubricant.
21. The liner of claim 20, wherein said lubricant comprises one or
more selected from the group consisting of graphite and lithium
stearate.
22. The liner of claim 20, wherein said lubricant comprises from
more than 0 percent by weight to about 10 percent by weight.
23. A shaped charge comprising: a housing; a quantity of explosive
provided in said housing; and a liner provided in said housing so
that said explosive is located between said liner and said housing,
said liner being compressively formed from a mixture of dendritic
copper powder and a lubricant, said mixture comprising from about
90 percent by weight to less than 100 percent by weight said
dendritic copper powder and from more than 0 percent by weight to
about 10 percent by weight said lubricant.
24. The shaped charge of claim 23, wherein said mixture comprises
about 99 percent by weight said dendritic copper powder and about 1
percent by weight said lubricant.
25. The shaped charge of claim 23, wherein said explosive comprises
one or more selected from the group consisting of RDX, HMX, and
HNS.
26. A liner for a shaped charge consisting essentially of dendritic
copper powder compressed under sufficient pressure to cause said
dendritic copper powder to behave as a nearly solid mass.
27. The liner of claim 26, further comprising a lubricant mixed
with said dendritic copper powder.
28. The liner of claim 27, wherein said lubricant comprises one or
more selected from the group consisting essentially of lithium
stearate and graphite.
29. A powder mixture consisting essentially of dendritic copper
powder and a lubricant, said lubricant having a percent by weight
which lies in a range from more than 0 percent to less than 10
percent, a remaining percent by weight of said mixture being said
dendritic copper powder.
30. The powder mixture of claim 29, wherein said lubricant
comprises one or more selected from the group consisting of lithium
stearate and graphite.
31. The powder mixture of claim 29 further comprising a green
strength in a range of about 3800 psi to about 5000 psi when said
powder mixture is compressed under a pressure of about 30 tsi.
32. The powder mixture of claim 29 further comprising a green
density in a range of about 7 g/cc to about 8 g/cc when said powder
mixture is compressed under a pressure of about 30 tsi.
Description
TECHNICAL FIELD
[0001] This invention relates to shaped explosive charges in
general and more specifically to liners for shaped explosive
charges.
BACKGROUND
[0002] Shaped explosive charges are known in the art and may be
used, for example, to form hydraulic openings or perforations in
wellbores. The wellbore must be perforated because the casing of a
wellbore is commonly retained within the wellbore by filling the
annulus between the casing and wellbore with cement. In addition to
retaining the casing within the wellbore, the cement also
hydraulically isolates from one another the various formations
penetrated by the wellbore.
[0003] A typical shaped charge for wellbore perforation comprises a
bell-shaped housing having an open end for receiving a quantity of
high-explosive, such as RDX, HMX, or HNS. A liner, typically of
conical shape, is positioned within the open end of the housing so
that the high-explosive is contained between the liner and the
housing. The shaped charge may then be placed in a suitable
perforation "gun" and lowered into the wellbore to perforate the
same. When detonated, the high explosive collapses the liner and
ejects it from the open end of the housing at an extreme velocity
(i.e., hypersonic) in a pattern commonly referred to as a "jet."
The jet penetrates the wellbore casing, the cement, as well as
portions of the surrounding formation. It is generally believed
that, at such extreme velocities, the penetration process is
hydrodynamic, with the jet and the "target" behaving as
incompressible fluids. Consequently, the inherent mechanical
strengths of the jet and target material are of little
importance.
[0004] Generally speaking, it is desirable to perforate the
formation surrounding the wellbore to a significant degree,
referred to as penetration depth, in order to provide efficient
hydraulic communication between the formation and the wellbore. The
penetration depth may be increased by increasing the quantity of
explosive provided within the housing, which may be appropriate in
some cases. In addition, the penetration depth can also be affected
by the shape and/or composition of the liner, as is known in the
art.
[0005] The liners for shaped charges are usually formed from
copper, although other materials have been tried and may be used as
well. However, copper has been found to be generally preferable in
most applications due to its high performance and low cost. While
the copper may be formed into the particular shape (e.g., typically
conical) from an ingot of solid metal, it is more common to form
the liner from copper powder by pressing the copper powder in a
form or mold. In order to ensure that the compressed copper powder
remains in the desired compacted form, it has proven necessary to
mix the copper powder with a binder material. As its name implies,
the binder material binds together the copper powder and also
provides the liner with sufficient green strength to allow it to be
incorporated into the shaped charge and withstand subsequent
handling without disintegrating.
[0006] The binder material typically comprises lead powder and is
added in significant quantities, generally comprising about 20
weight percent or so of the liner. While being effective as a
binder, the presence of lead is disadvantageous from manufacturing
and environmental standpoints. For example, personnel must be
protected from the lead during fabrication and subsequent handling
of the liners. In addition, the detonation of the shaped charge in
the wellbore will cause the lead from the liner to be introduced
into the formation and wellbore environment.
[0007] Partly in an effort to avoid the problems with powdered lead
binders, other powdered metals, such as bismuth, silver, gold, tin,
uranium, antimony, zinc, cobalt, and nickel have been tried with
varying degrees of success. Unfortunately, however, none of these
other binder materials has proven entirely satisfactory in practice
for a number of reasons, and lead powder binders continue to be
widely used.
SUMMARY OF THE INVENTION
[0008] A liner for a shaped charge according to one embodiment may
consist essentially of dendritic copper powder compressed under
sufficient pressure to cause the dendritic copper powder to behave
as a nearly solid mass. Another embodiment may consist essentially
of a mixture of dendritic copper powder and a lubricant compressed
under sufficient pressure to cause the mixture to behave as a
nearly solid mass. Another embodiment of a liner for a shaped
charge may comprise at least 70% by weight dendritic copper
powder.
[0009] A shaped charge according to one embodiment of the present
invention may include a housing and a quantity of explosive
provided in the housing. A liner is positioned in the housing so
that the explosive is located between the liner and the housing.
The liner is compressively formed from a mixture of dendritic
copper powder and a lubricant, the mixture comprising from about 90
percent by weight to less than 100 percent by weight dendritic
copper powder and from more than 0 percent by weight to about 10
percent by weight lubricant.
[0010] A method for producing a liner for a shaped-charge explosive
may involve providing a mixture consisting essentially of dendritic
copper powder and a lubricant; and compressing the mixture under
sufficient pressure to cause the mixture to behave as a nearly
solid mass.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Illustrative and presently preferred exemplary embodiments
of the invention are shown in the drawings in which:
[0012] FIG. 1 is a cross-sectional view in elevation of a shaped
charge having a lead-free liner according to one embodiment of the
invention;
[0013] FIG. 2 is a scanning electron micrograph of dendritic copper
powder that may be used to construct lead-free shaped charge
liners; and
[0014] FIG. 3 is a schematic process diagram of a method for
forming a lead-free shaped charge liner.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] A shaped charge 10 having a lead-free liner 12 is
illustrated in FIG. 1 and may comprise a bell-shaped housing 14
sized to receive a quantity of explosive material 16 as well as the
lead-free liner 12. Although not shown in FIG. 1, shaped charge 10
may also be provided with an initiator and/or a detonating cord in
order to detonate the explosive material 16.
[0016] In the embodiment shown and described herein, the shaped
charge 10 is configured to be used in "down-hole" applications to
perforate wellbores and surrounding formations. As such, the shaped
charge 10 is sized to be received by a perforation gun (not shown),
that may be lowered into the wellbore. Generally speaking, such
perforation guns are configured to receive a plurality of shaped
charges, thereby allowing many separate perforations to be formed
in the wellbore. When initiated, the explosive material 16
collapses the lead-free liner 12 which forms a jet (not shown). The
jet travels generally along the longitudinal axis 18 of shaped
charge 10, perforating the wellbore casing, the cement surrounding
the casing, as well as portions of the formation.
[0017] In accordance with the teachings provided herein, the
lead-free liner 12 may be formed substantially entirely of
dendritic copper powder 20 (FIGS. 2 and 3). That is, the liner 12
does not require the presence of a binder, lead or otherwise.
Generally speaking, the dendritic copper powder 20 should comprise
at least about 70 percent by weight of the lead-free liner 12, such
as at least about 90 percent by weight of the lead-free liner 12,
and more preferably about 100 percent by weight (not including the
presence of a lubricant, as described below). Put in other words,
it will be generally advantageous to form the liner 12
substantially entirely from dendritic copper powder 20 (with the
exception of a lubricant), with only minimal amounts of
non-dendritic copper powders and/or other materials which may be
present, and which may be generally regarded as impurities that do
not materially affect the basic characteristics of the dendritic
copper powder composition and liners made therefrom.
[0018] The dendritic copper powder 20 may comprise any of a wide
range of particle sizes and mixtures of particle sizes so long as
the particle sizes allow the dendritic copper powder 20 to be
compressed and achieve the green strengths and densities described
herein. Generally speaking, acceptable results can be obtained with
powder sizes in the following ranges: TABLE-US-00001 TABLE 1 Mesh
Size Weight Percent 150 7%-11% 200 16%-24% +325 30%-40% -325
37%-44%
[0019] Alternatively, good results have been obtained with
dendritic copper powder mixtures comprising about 95 percent by
weight particles smaller than 325 mesh.
[0020] The dendritic copper powder 20 may be prepared by any of a
wide range of electrolytic deposition processes known in the art
and is currently commercially available from a wide range of
suppliers. By way of example, in one embodiment, a suitable supply
of dendritic copper powder 20 is available from Phelps Dodge
Corporation of Phoenix, Ariz. (US). Generally speaking, the
dendritic copper power 20 should be substantially free of
impurities, with impurity levels of less than about 1 weight
percent providing acceptable results.
[0021] A small quantity of a lubricant 22 (FIG. 3) may be mixed
with the dendritic copper powder 20 to form a mixture 24. The
addition of the lubricant 22 will assist in the subsequent
compression of the mixture 24 in a suitable mold or form (not
shown) in order to cause the mixture 24 to behave as a nearly solid
mass, thus forming the liner 12. The lubricant 22 may be present in
a range of about 10 percent by weight to less than about 0 percent
by weight, and more preferably in a range of about 1 percent by
weight to about 0.75 percent by weight. Lubricant 22 may comprise
any of a wide range of lubricants now known in the art or that may
be developed in the future that would be suitable for the
particular application. Consequently, the present invention should
not be regarded as limited to any particular lubricant. However, by
way of example, in one embodiment, the lubricant 22 may comprise
lithium stearate. Alternatively, graphite (e.g., 1651 graphite), or
a combination of lithium stearate and graphite, may be used as the
lubricant 22.
[0022] In addition to a lubricant 22, small amounts (e.g.,
generally less than about 5 percent by weight) of a higher density
metal powder may be added to increase the green density of the
desired product (e.g., charge liner 12). For example, powdered
molybdenum, tungsten, and mixtures thereof, may be added in
quantities of up to about 5 weight percent in order to increase the
green density of the charge liner 12.
[0023] Referring now primarily to FIG. 3, once a mixture 24 has
been prepared, e.g., from a supply of dendritic copper powder 20
and a supply of a lubricant 22, it may be formed into the desired
product (e.g., liner 12) by any of a wide range of forming
processes 26 now known in the art or that may be developed in the
future that are (or would be) suitable for forming the powder
mixture 24 so that it behaves as a nearly solid mass. An exemplary
forming process 26 that may be utilized is a cold compaction
process, although other forming processes, such as hot and cold
isostatic pressing processes, may also be used.
[0024] If the mixture 24 is to be used to form a liner 12 for an
explosive shaped charge of the type suitable for wellbore
perforation, it will be generally desirable to compress the mixture
24 to a degree sufficient to provide the liner 12 with the desired
green strength. For example, when compressed under a pressure of
about 30 tons/in.sup.2 (tsi) (about 4.14.times.10.sup.8 Pa) copper
powder mixtures 24 prepared in accordance with the teachings
provided herein will acquire green strengths in a range of about
3800 pounds per square inch (psi) (about 2.62.times.10.sup.7 Pa) to
about 5000 psi (about 3.45.times.10.sup.7 Pa) and green densities
in a range of about 7 to about 8 g/cc. Generally speaking,
experiments have confirmed that mixtures prepared in accordance
with the teachings provided herein generally provide higher green
strengths and comparable green densities under the same compressive
pressures as compared to those achieved by a conventional copper
powder/lead binder mixture.
COMPARATIVE EXAMPLES
[0025] Two different mixtures "A" and "B" comprising dendritic
copper powder 20 were compared with results obtained from a
conventional (i.e., non-dendritic) copper powder mixture
("Conventional"). More specifically, Mixture "A" comprised
dendritic copper powder (about 95%-325 mesh), and about 0.75
percent by weight lithium stearate. Mixture "B" comprised mixture
"A" with about 1 percent by weight graphite added (i.e., about 0.75
percent by weight lithium stearate and about 1 percent by weight
graphite). The conventional copper powder mixture, commonly
referred to as "CLG-80" comprised 80 percent by weight
non-dendritic copper powder (56%-150/+325 mesh, 25%-325 mesh), 19
percent by weight lead powder, and 1 percent by weight carbon
graphite as a lubricant.
[0026] A first comparative test was used to measure the comparative
green densities and green strengths of compacted rods or bars made
from the conventional mixture and Mixture "A." More specifically,
the first test comprised a die wall friction test and was conducted
in accordance with the procedures specified by ASTM B-328. Briefly,
ASTM B-328 involves the compression of powder contained within a
cylindrical opening formed within a die. The cylindrical opening
has a diameter of 0.125 inches (in) (about 7.125 mm) and a length
of 1.0 in (about 2.54 mm). The powders were compacted from the top
only at a pressure of about 30 tons/in.sup.2 (tsi) (about
4.14.times.10.sup.8 Pa). The resulting compacted rods or bars of
the samples were then cut into four equal segments (A, B, C, and
D), the green densities and strengths of which were then measured
in accordance with ASTM testing methods.
[0027] The results of the test are presented below in Table 2.
TABLE-US-00002 TABLE 2 Conventional (Cu80Pb18C1) Mixture "A" Green
Green Green Density Strength Green Density Strength Location (g/cc)
(psi) (g/cc) (psi) Top (A) 7.34 2050 7.17 4150 B 7.29 1900 6.71
2750 C 6.87 1150 6.27 1800 Bottom (D) 6.27 550 5.99 1400
[0028] As indicated in Table 2, at 30 tsi compaction pressure, the
green strength of a bar formed from Mixture "A" exceeded that of a
bar formed from conventional powder at any position along the
length of the respective sample bars. The green density of a bar
formed from Mixture "A" was generally comparable, although slightly
lower, than that associated with a bar formed from the conventional
powder. Lubricity measured by the die wall friction test shows
large gains in green strengths with comparable green densities for
Mixture "A" compared to the conventional mixture.
[0029] Average green strengths and densities for the conventional
powder, Mixture "A," and Mixture "B" were also obtained by
compressing the powders at various pressures, i.e., 5, 10, 30, and
48 tsi (about 6.9.times.10.sup.7, 1.38.times.10.sup.8,
4.14.times.10.sup.8, and 6.62.times.10.sup.8 Pa) to produce 3
separate compressed samples at each compaction pressure. The
average values for each of the three samples at each of the
pressures are presented in Table 3: TABLE-US-00003 TABLE 3
Conventional (Cu80Pb19C1) Mixture "A" Mixture "B" Green Green Green
Green Green Green Pressure Density Strength Density Strength
Density Strength (tsi) (g/cc) (psi) (g/cc) (psi) (g/cc) (psi) 5
5.80 311 5.32 620 5.30 640 5 5.79 290 5.34 648 5.32 630 5 5.81 339
5.33 651 5.31 600 Avg. 5.80 313 5.33 640 5.31 620 10 6.62 1013 6.16
1570 6.09 1510 10 6.63 1002 6.16 1540 6.08 1450 10 6.58 936 6.18
1610 6.09 1600 Avg. 6.61 984 6.17 1570 6.09 1520 30 8.04 3697 7.45
4940 7.28 4440 30 8.07 3784 7.45 5190 7.27 4640 30 8.06 3883 7.40
4920 7.29 4530 Avg. 8.06 3788 7.43 5020 7.28 4537 48 8.53 5342 7.81
6870 7.58 6200 48 8.53 5326 7.80 6820 7.59 6150 48 8.50 5357 7.84
6530 7.61 5950 Avg. 8.52 5341 7.82 6740 7.59 6100
[0030] As evidenced by the data in Table 3, samples formed from
both Mixtures "A" and "B" produced significantly higher green
strengths at all compaction pressures compared to samples formed
from the conventional powder. Green densities were generally
comparable, although somewhat lower, compared to samples formed
from the conventional powder.
[0031] Two additional mixtures, Mixture "C" and Mixture "D" were
also prepared using dendritic copper powder having particle sizes
shown in Table 4: TABLE-US-00004 TABLE 4 Mesh Size Weight Percent
-100/+170 8% -170/+230 18% -230/+325 33% -325 41%
[0032] Mixture "C" also comprised about 0.75 percent by weight
lithium stearate. Mixture "D" comprised Mixture "C" with about 1
percent by weight graphite added (i.e., about 0.75 percent by
weight lithium stearate and about 1 percent by weight graphite).
Three separate samples of Mixtures "C" and "D" were compressed
under a pressure of about 30 tsi (about 4.14.times.10.sup.8 Pa).
The average values for each of three samples at the 30 tsi
compaction pressure are presented in Table 5: TABLE-US-00005 TABLE
5 Conventional Mixture Mixture Mixture Mixture (Cu80Pb19C1) A B C D
Green Density 8.06 7.43 7.28 7.58 7.47 (g/cc) Green Strength 3788
5020 4530 3908 3816 (psi)
[0033] As evidenced by the data in Table 5, samples formed from
Mixtures "C" and "D" resulted in somewhat higher green densities,
but somewhat lower green strengths when compared with Mixtures "A"
and "B." The green densities of Mixtures "C" and "D" were
comparable to those achieved by the conventional powder, with the
green strengths being somewhat higher.
[0034] Having herein set forth preferred embodiments of the present
invention, it is anticipated that suitable modifications can be
made thereto which will nonetheless remain within the scope of the
invention. The invention shall therefore only be construed in
accordance with the following claims:
* * * * *