Note: Descriptions are shown in the official language in which they were submitted.
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OIL WELL PERFORATOR LINER WITH HIGH PROPORTION OF HEAVY METAL
TECHNICAL FIELD
A shaped charge suitable for use in a perforating tool for a subterranean well
is
described. The invention relates particularly to an improved shaped charge
liner constructed
from powdered heavy metal and binder material with a high proportion of
tungsten or similar
heavy metal.
BACKGROUND OF THE INVENTIONS
A subterranean gas or oil well typically begins with a hole bored into the
earth, which is
then lined with joined lengths of relatively large diameter metal pipe. The
casing thus formed is
generally cemented to the face of the hole to give the well integrity and a
path for producing
fluids to the surface. Conventionally, the casing and cement are subsequently
perforated with
chemical means, commonly explosives, in one or more locations of the
surrounding formation
from which it is desired to extract fluids. In general, the perforations
extend a distance into the
formation. Once of the problems inherent in the art is to maximize the depth
of penetration into
the formation.
Explosive shaped charges known in the art generally have a substantially
cylindrical or
conical shape and are used in various arrangements in perforating tools in
subterranean wells.
Generally, a tubular perforating gun adapted for insertion into a well is used
to carry a plurality
of shaped charges to a subsurface location where perforation is desired. Upon
detonation of the
shaped charges, explosive jets emanate from the shaped charges with
considerable velocity and
perforate the well casing and surrounding formation.
Liners of shaped charges have commonly been designed in an effort to maximize
penetration depth. Various metals have been used. Solid metal liners have the
disadvantage of
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introducing metal fragments into the formation, detracting from the
effectiveness of the
perforation. Compressed powdered metal liners have sometimes been used. Such
liners
disintegrate upon detonation of the shaped charge, avoiding the problems
associated with metal
fragments. It is known in the art that heavy metals are particularly suited
for use in liners.
Generally, the heavy metal is combined with one or more other metals with
suitable binding
characteristics to form rigid liners through very high compression of the
metal powders. One of
the principal problems in the art has been the attempt to increase the heavy
metal content of
liners. Such attempts are outlined in the United States Patent Numbers
5,656,791 and
5,814,758, which are incorporated herein for all purposes by this reference.
The success in the art of producing compressed powdered heavy metal liners has
been
limited by effort to identify suitable binding agents among elemental metals
and alloys.
Previous attempts in the art have increased tungsten content to approximately
80 percent. The
present invention employs binder materials in combination with tungsten powder
to produce an
improved shaped charge compressed liner with a tungsten content higher than
previously known
in the art.
SUMMARY OF THE INVENTIONS
The inventions provide shaped charge apparatus for use in a subterranean well.
In
general, the inventions contemplate an improved liner for a shaped charge
constructed from a
combination mixture of a high proportion of powdered heavy metal and selected
binder metal.
According to one aspect of the invention, a mixture of powdered tungsten and
powdered
metal binder is formed into a rigid shaped charge liner having a tungsten
content in a range of
between approximately 90% to 99.98% by weight.
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According to another aspect of the invention, a liner having a tungsten
content in a range
of between approximately 90% to 99.98% by weight is constructed of a binder
metal-coated
heavy metal powder formed into a rigid body.
According to a still another aspect of the invention, a liner for a shaped
charge is
constructed from a mixture of powdered tungsten and powdered metal binder
blended with a
binder metal-coated heavy metal powder formed into a substantially conical
rigid body. The
resulting liner having a tungsten metal content in a range of between
approximately 93% to
99.98% by weight.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings are incorporated into and form a part of the
specification to
illustrate several examples of the present inventions. These drawings together
with the
description serve to explain the principals of the inventions. The drawings
are only for the
purpose of illustrating preferred and alternative examples of how the
inventions can be made and
used and are not to be construed as limiting the inventions to only the
illustrated and described
examples. The various advantages and features of the present inventions will
be apparent from a
consideration of the drawings in which:
FIGURE 1 is a side elevation view of an example of an axially symmetrical
shaped
charge in accordance with the invention; and
FIGURE 2 is cross-sectional view taken along line 2-2 of Figure 1 showing an
example
of an embodiment of a shaped charge in accordance with the inventions.
DETAILED DESCRIPTION
The present inventions are described by reference to drawings showing one or
more
examples of how the inventions can be made and used. In these drawings,
reference characters
are used throughout the several views to indicate like or corresponding parts.
The drawings are
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not necessarily to scale and the proportions of certain parts have been
exaggerated to better
illustrate details and features of the invention.
The apparatus and methods of the invention are shown generally in Figures 1
and 2.
A conically symmetrical shaped charge 10 is shown. The shaped charge is sized
for a
perforating gun commonly used to perforate subterranean.wells and formations.
Typically, a
plurality of shaped charges are arranged in a substantially helical pattern on
the perforating
gun assembly. The exact size and shape of the shaped charge or the
configuration of the
perforating gun are not critical to the invention. The shaped charge 10 is
enclosed by a case
12. Generally, the case 12 is substantially cylindrical or conical. As used
herein, the term
"conical" is used to refer to shapes substantially conical or in the form of
frustum or truncated
cone. Again, the exact shape of the case is not critical to the invention. In
use, the
perforating gun (not shown) is placed in a subterranean location where
perforation of the well
casing and/or formation is desired, herein designated the target 14. The
shaped charge has a
muzzle 16, which is oriented toward the target 14, and an opposing closed end
18.
Now refernng primarily to Figure 2, the case 10 is shown in cross section,
revealing
that the closed end 18 has a relatively small aperture 20 connected to a
detonation cord 22.
The detonation cord 22 is typically operably connected to a detonation circuit
system (not
shown) known in the art. The case 10 contains a predetermined amount of high
explosives
24 generally known in the arts, for example, RDX, HMX, HNS, CL-20, NONA, BRX,
PETN, or PYX. A substantially conical liner 26 is disposed inside of case 12
between the
high explosive 24 and the muzzle 16, preferably such that the high explosive
24 fills the
volume between the casing 12 and the liner 26. The liner is typically affixed
to the case with
adhesive (not shown), but a retaining ring or spring may also be used. Upon
detonation of
the high explosive 24, the liner 26 disintegrates and the liner material is
propelled through the
muzzle 16 into the target 14. As known to those skilled in the arts, it is
advantageous for the
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liner to disintegrate upon detonation of the high explosive and to have the
maximum possible
mass and velocity.
Further refernng primarily to Figure 2, the liner 26 is preferably constructed
by
compressing a powdered heavy metal and powdered metal binder material under
very high
pressure to form a rigid body. The process of compressively forming the liner
from powdered
heavy metal and powdered metal binder is understood by those skilled in the
arts. Other
methods of fabrication, such as sintering may be used. The powdered heavy
metal is preferably
tungsten, but may be another metal or mixture of metals. Metals with high
density, high
ductility, and capable of achieving high acoustic velocity are preferred.
Metals chosen from the
group tungsten, tantalum, hafnium, and copper are particularly suitable.
Although other metals
may be used, cost is often a major factor. Preferably, the percentage of heavy
metal, preferably
tungsten, in the liner is within a range of approximately 99.0% to 99.98% by
weight.
Optionally, percentages within a range of approximately 90.0% to 99.98% may be
used.
The binder metal is chosen for its ability to bind together under high levels
of
compression. Typically, metals chosen from the group copper, lead, zinc, tin,
and bismuth are
used. The percentage of powdered binder metal, preferably lead, in the mixture
is preferably
within a range of approximately 0.02% to 1.0% by weight, although percentages
within a range
of approximately 0.02% to 10.0% may be used. Optionally, mixtures of binder
metals or
alloys such as those containing relatively high levels of tin or zinc may be
used.
Optionally, the liner 26 may also contain approximately 0.2% to 1.0% lubricant
by
weight. Powdered graphite is a preferred lubricant known in the arts, although
oils may also be
used. Some oils such as linseed oil or tong oil, or other unsaturated organic
compounds as
disclosed in United States Patent Number 4,794,990, which is incorporated in
its entirety for all
purposes by this reference, are thought to be helpful in preventing corrosion
of the liner.
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The presently most preferred embodiment of the invention uses a liner 236
constructed
from a heavy metal powder coated with a binder metal, a binder metal-coated
heavy metal
powder compressively formed into a rigid body. The process of coating the
heavy metal powder
with a binder metal is understood by those skilled in the arts. The heavy
metal powder, coated
with a binder metal, is then compressed under very high pressure into a rigid
body. Presently,
tungsten and lead are preferred for the heavy metal and binder metal coating,
respectively,
although the alternative metals described above may be used. Combinations of
metals may also
be used. Preferably, the percentage of tungsten in the liner is within a range
of approximately
99.0% to 99.98% by weight, although percentages within a range of
approximately 90.0% to
99.98% may be used. The percentage of led in the mixture is preferably within
a range of
approximately 0.02% to 1.0% by weight, although percentages within a range of
approximately
0.2% to 10.0% may optionally be used.
An additional alternative embodiment of the invention uses a liner 26, which
is
construed of a combination of the elements of the first two embodiments
described. That is, a
I S mixture of heavy metal powder and powdered binder metal may be used in
combination with
binder metal-coated heavy metal powder to construct the liner 26. The same
proportions and
variations in ingredients described with reference to the first two
embodiments may be
employed with this additional embodiment as well.
The invention has many advantages attendant with raising the percentage of
heavy metal
in the liner to higher levels than have been known in the art.
The embodiments shown and described above are only exemplary. Many details are
often found in the art such as: types of high explosives, size and shape of
shaped charges, and
configuration of perforating gun assemblies. Therefore, many such details are
neither shown
nor described. It is not claimed that all of the details, parts, elements, or
steps described and
shown were invented herein. Even though numerous characteristics and
advantages of the
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present inventions have been set forth in the foregoing description, together
with details of
the structure and function of the inventions, the disclosure is illustrative
only, and changes
may be made in the detail, especially in matters of shape, size and
arrangement of the parts
within the principles of the inventions to the full extent indicated by the
broad general
meaning of the terms used in the attached claims.
The restrictive description and drawings of the specific examples above do not
point out
what an infringement of this patent would be, but are to provide at least one
explanation of how
to make and use the inventions. The limits of the inventions and the bounds of
the patent
protection are measured by and defined in the following claims.
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