U.S. patent application number 10/750108 was filed with the patent office on 2005-06-30 for minimal resistance scallop for a well perforating device.
Invention is credited to Mauldin, Sidney Wayne.
Application Number | 20050139352 10/750108 |
Document ID | / |
Family ID | 34701151 |
Filed Date | 2005-06-30 |
United States Patent
Application |
20050139352 |
Kind Code |
A1 |
Mauldin, Sidney Wayne |
June 30, 2005 |
Minimal resistance scallop for a well perforating device
Abstract
The present invention is an improvement in the design of a
perforating gun to perforate the casing in oil and gas wells.
Perforating guns have a cylindrical body member with explosive
charges at specified intervals designed to shoot outwardly through
the body member, the well casing, cement sheath, and into the rock
formation. There are recessed areas, scallops, on the outer surface
of the body member where the perforating jets, formed by the
explosive charges, exit the body member. The present invention uses
the strength of an arching geometric shape for the recessed area to
be able to further reduce the thickness of steel for minimal
resistance to the perforating jet. Minimizing the resistance to the
perforating jet increases the depth of penetration into the rock
formation and increases the hole size.
Inventors: |
Mauldin, Sidney Wayne;
(Pampa, TX) |
Correspondence
Address: |
Brian E. Powley
Brian E. Powley, P.L.L.C.
P.O. Box 720415
Oklahoma City
OK
73172-0415
US
|
Family ID: |
34701151 |
Appl. No.: |
10/750108 |
Filed: |
December 31, 2003 |
Current U.S.
Class: |
166/55 ;
175/4.6 |
Current CPC
Class: |
E21B 43/116
20130101 |
Class at
Publication: |
166/055 ;
175/004.6 |
International
Class: |
E21B 043/11 |
Claims
What is claimed is:
1. A well perforating device comprising a tubular body member
having a plurality of inwardly shaped hole penetration areas of
reduced thickness formed on the outer surface thereof, and a
plurality of perforating charges positioned within said body
member, each of said perforating charges containing a hollow cone
shaped explosive charge aligned with one of said hole penetration
areas so that upon detonation of the hollow cone shaped charge said
body member is penetrated through said aligned hole penetration
areas, an improvement comprising; an arched geometric shape in said
inwardly shaped hole penetration areas which provides additional
strength to said tubular body member so that the thickness of said
body member at the location of said inwardly shaped hole
penetration can be further reduced minimizing the resistance to
said perforating charges while still retaining sufficient
structural strength to withstand pressures exerted on said body
member.
2. The perforating device of claim 1 wherein said plurality of
inwardly shaped hole penetration areas have an elliptical
shape.
3. The perforating device of claim 1 wherein said plurality of
inwardly shaped hole penetration areas have a radius shape.
4. The perforating device of claim 3 wherein said plurality of
inwardly shaped hole penetration areas are made longer
longitudinally so that said hole penetration areas have an
elliptical shape.
5. The perforating device of claim 1 wherein said plurality of
inwardly shaped hole penetration areas have a radius shape with a
longitudinal flat area where the thickness of said body member is
reduced the most.
6. The perforating device of claim 5 wherein said longitudinal flat
area makes said plurality of inwardly shaped hole penetration areas
to have an elliptical shape.
7. The perforating device of claim 1 wherein said plurality of
inwardly shaped hole penetration areas has an industry standard
elliptical shape with an additional longitudinal arched shape so
that a flat area is formed at the center of said hole penetration
area where the thickness of said body member is reduced the
most.
8. A well perforating devise comprising a tubular body member
having at least one hole penetration area of reduced thickness
formed in the outer surface thereof, and a perforating charge
positioned within said body member, said perforating charge
containing a hollow cone shaped explosive charge aligned with one
of said hole penetration areas so that upon detonation of the
hollow cone shaped charge said body member is penetrated through
said aligned hole penetration area, an improvement comprising; an
arched geometric shape for said hole penetration area of reduced
thickness as a means to provide additional structural strength to
further reduce the thickness while retaining sufficient strength to
withstand pressures exerted on said body member.
9. The perforating device of claim 8 wherein said hole penetration
area has an elliptical shape.
10. The perforating device of claim 8 wherein said hole penetration
area has a radius shape.
11. The perforating device of claim 10 wherein said hole
penetration area is made longer longitudinally so that said hole
penetration area has an elliptical shape.
12. The perforating device of claim 8 wherein said hole penetration
area has a radius shape with a longitudinal flat area where the
thickness of said body member is reduced the most.
13. The perforating device of claim 12 wherein said longitudinal
flat area makes said hole penetration area to have an elliptical
shape.
14. The perforating device of claim 8 wherein said hole penetration
has an industry standard elliptical shape with an additional
longitudinal arched shape so that a flat area is formed at the
center of said hole penetration area where the thickness of said
body member is reduced the most.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable
REFERENCE TO A MICROFICHE APPENDIX
[0003] Not Applicable
BACKGROUND OF THE INVENTION
[0004] The invention relates generally to an improvement in the
design of an oil and gas well perforating device. The improvement
applies to a type of perforating device that is typically lowered
into the well through the casing or tubing in the well to a
position where the explosive charges are detonated at the desired
depth. The improvement is a method of modifying the scallop that is
cut on the exterior of the device, at the location of a perforating
charge, so as to minimize the resistance to the explosive charge
which in turn improves the performance of the perforating charge by
increasing its depth of penetration and hole size.
[0005] After an oil or gas well is drilled, steel casing is lowered
into the well and cemented to the adjoining rock formations.
Typically, perforations are needed to allow the oil or gas from the
desired rock formation to be able to flow into the casing and then
out of the well. The perforations are made by lowering, on a
wireline or tubing, the perforating gun containing explosive
charges to the desired depth and detonating the charges. There are
several different types of perforating guns.
[0006] One type of perforating gun is referred to as a casing gun.
A casing gun is a hollow steel carrier that is lowered into the
casing of the well with the perforations made through screwed in
ports. These screwed in ports are used to allow the ports to be
removed and the perforating gun used again. Since the present
invention relates to an improvement in a scallop for the
perforation, the present invention is not applicable to a casing
gun.
[0007] A second type of perforating gun is an expendable casing
gun. This is similar to the previously discussed casing gun with
the addition of larger charges that will cause significant
distortion to the hollow steel carrier. The distortion is
sufficient to make the hollow steel carrier useable only one time
and therefore expendable. The larger charges are sometimes needed
when greater penetration is required such as when some of the rock
formation has washed away and there is a greater amount of cement
to penetrate. An expendable casing gun will have scallops cut for
the perforations or may have no scallops at all which is referred
to as run slick.
[0008] A third type of perforating gun is a tubing conveyed
perforating gun. The tubing is a retrievable string of pipe inside
of the casing that is permanently cemented in place. This is
another type of casing gun except the carrier is made a part of the
tubing string rather than being run on the wireline. The carrier
can have scallops or be slick.
[0009] All of the previously discussed perforating guns are made to
be lowered into the casing. There are also perforating guns made to
be lowered into the tubing. These through tubing perforating guns
are designed to be utilized while leaving the tubing inside the
well and casing. In order for the perforating guns to be lowered
inside of the tubing requires a smaller diameter perforating gun.
The through tubing perforating guns are lowered through the tubing
to a desired depth, below the bottom of the tubing, at the desired
rock formation.
[0010] A fourth type of perforating gun is a through tubing strip
gun run on wireline. This type of perforating gun includes a strip
carrier on which capsule shaped charges may be mounted. The capsule
shaped charges are sealed to protect the charges from the well
environment. At detonation the strip gun is basically blown apart
and the debris drops to the bottom of the well below the
perforations. Any intact portion of the strip gun is then retrieved
through the tubing. There is no hollow steel carrier needed for the
through tubing strip gun and so the present invention is not
applicable to this type of perforating gun.
[0011] A fifth type of perforating gun is the retrievable through
tubing gun which is like the casing gun in that it uses a sealed
carrier to hold the charges but is a smaller diameter to fit inside
the tubing. These smaller diameter carriers utilize the scallops
and the present invention would be applicable.
[0012] In summary, the present invention is applicable to all of
the types of perforating guns with the exception of the casing gun
that uses screwed in ports and the strip gun that has no carrier.
All of the perforating guns discussed utilize a sealed carrier with
the exception of the strip gun. The sealed carriers usually have
recessed areas or scallops at the location of the charges. The
recessed area was originally made to compensate for the burr formed
on the outside of the carrier and also serves to reduce the amount
of energy the charge loses in exiting the perforating gun. The
recessed area of reduced wall thickness can be accomplished in
different ways, such as removable plugs for the casing gun, but the
most common method is to make a cut into the outer surface of the
perforating gun at the location of each perforating charge. This
type of cut is typically referred to as a scallop. Removing more
steel in the scallop is limited by the decrease in strength of the
carrier.
[0013] There are no known attempts to modify the scallop, cut in
the carrier, in order to further reduce the thickness of the steel
by changing the geometrical shape of the scallop to make it
structurally stronger. Schlumberger has two patents related to
shaped geometry recesses to reduce or control reflection of
compression waves generated from the explosive jet. Schlumberger
has a method of making the recess by drilling a round hole
perpendicular to the carrier with a resulting flat bottom and a
ninety degree angle between the flat bottom and side. This is the
prior art as described and drawn by Schlumberger. Schlumberger then
offers in U.S. Pat. Nos. 6,460,463 B1 and 6,523,474 B2 a variety of
different geometrical shapes, usually with sloping sides, that
could reduce the compression waves generated by use of
Schlumberger's prior art. The prior art and improvements described
in that patent are unique to the way that Schlumberger makes their
recesses.
[0014] The normal method utilized in the industry is the scallop
which removes more steel over a larger area. The compression waves
are not considered of any consequence in such a design as there is
little to no sides to constrict the compression waves. The industry
standard scallop method does not require as much accuracy in aiming
the perforating charges as the Schlumberger method. The present
invention adds a geometric cut to the scallop to remove more steel
while increasing the mechanical strength of the carrier to
withstand the internal and external pressures.
[0015] There continues to be a need to be able to minimize the
energy lost by the perforating jet in exiting the sealed hollow
steel carrier of the perforating guns. Any reduction in the energy
lost exiting the carrier is available to the perforating jet to be
able to penetrate deeper into the rock formation. Increasing the
depth of penetration and hole size are the most important factors
in the performance of a perforating gun. The method of reducing the
lost energy must also maintain sufficient integrity of the carrier
housing.
SUMMARY OF THE INVENTION
[0016] The present invention is an improvement for a well
perforating device and method of manufacture to make a modification
to the industry standard method of cutting a scallop on the outer
surface of the hollow steel carrier that contains the perforating
charges. The scallops are made at the location of each charge to
reduce the energy needed to exit the carrier. The present invention
is the use of an arching geometric cut for the scallop. The
thickness of the carrier at the location of the scallop can be
reduced while maintaining sufficient structural strength to
withstand the pressures exerted on the carrier, as a result of the
additional strength imparted from the arched geometric cut. The
deeper arching geometric shape reduces the thickness of steel that
the perforating jet must penetrate to exit the carrier which
increases the remaining energy for greater penetration and hole
size. Increasing the depth of cut of the scallop alone to the same
thickness would result in significantly reduced structural strength
of the carrier and failure to withstand the external pressures
exerted on the carrier. The additional smaller geometric cut
utilizes the additional strength created from the rigidity of the
geometric cut to counter the effects of the reduced thickness.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a partial side view of the prior art elliptical
scallop cut on the outside of the perforating device hollow steel
carrier.
[0018] FIG. 2 is a partial, cross sectional view of the prior art
elliptical scallop cut along the longitudinal axis of the device of
FIG. 1 along line 2-2.
[0019] FIG. 3 is a partial, cross sectional view of the prior art
device of FIG. 2 along line 3-3.
[0020] FIG. 4 is a partial side view of the first preferred
embodiment of the present invention showing the resulting
elliptical shape made by a round bottom cut on the outside of the
perforating device hollow steel carrier.
[0021] FIG. 5 is a partial, cross sectional view of the first
preferred embodiment of the present invention along the
longitudinal axis of the device of FIG. 4 along line 5-5.
[0022] FIG. 6 is a partial, cross sectional view of the first
preferred embodiment of the present invention device of FIG. 5
along line 6-6.
[0023] FIG. 7 is a partial side view of the second preferred
embodiment of the present invention showing the resulting
elliptical shape made from a round flat bottom cut on the outside
of the well perforating device hollow steel carrier.
[0024] FIG. 8 is a partial, cross sectional view of the second
preferred embodiment of the present invention device along the
longitudinal axis of the device of FIG. 7 along the line 8-8.
[0025] FIG. 9 is a partial, cross sectional view of the second
preferred embodiment of the present invention device of FIG. 8
along line 9-9.
[0026] FIG. 10 is a partial side view of the third preferred
embodiment of the present invention showing the elliptical shape of
a standard scallop with an additional longer and narrower geometric
cut along the longitudinal axis on the outside of the well
perforating device hollow steel carrier.
[0027] FIG. 11 is a partial, cross sectional view of the third
preferred embodiment of the present invention device along the
longitudinal axis of the device of FIG. 10 along the line
11-11.
[0028] FIG. 12 is a partial, cross sectional view of the third
preferred embodiment of the present invention device of FIG. 11
along line 12-12.
DETAILED DESCRIPTION
[0029] In the following description, details of the present
invention are given to provide an understanding of the present
invention. However, those skilled in the art will know that the
present invention may be practiced without these details and that
numerous variations or modifications from the described embodiments
are possible.
[0030] Recesses formed in the outer wall of a body member 10 are to
enhance the performance of the shaped charge perforating jets or
other explosives. The thinned area allows for less energy to exit
the body member 10 and more energy to penetrate the rock formation.
The preferred embodiments presented are shaped with geometric cuts
to remove more steel, to improve performance, while utilizing the
strength of the geometric cut to maximize the remaining strength of
the body member 10 to withstand the hydrostatic pressures exerted
by the wellbore fluids. One of the preferred embodiments is adding
a geometric cut to the industry standard elliptical scallop 12.
[0031] FIG. 1 is a side view of a typical industry standard prior
art scallop 12 cut into the outside of the round tubular body
member hollow steel carrier 10 as part of a typical prior art
perforating device used to perforate the casing, cement and rock
formation in an oil and gas well to allow the reservoir fluids to
flow into the well. The perforating device comprises a cylindrical
body member 10, which is sealed to protect the plurality of
perforating charges, not shown, from the fluids in the wellbore and
from the hydrostatic pressures of those fluids. The body member 10
has a smaller outer diameter than the inner diameter of the casing
or tubing in order for the body member 10 to be slidably received
within the longitudinal inner diameter of the casing or tubing. The
body member 10 outer diameters range from one and three eighths
inches to seven inches and are most typically in the two to four
inch range.
[0032] There is a prior art scallop 12 cut in the outer wall of the
body member 10 where the perforating charge is positioned. The
prior art scallop 12 is aligned with the perforating charge such
that the perforating jet exits through the prior art scallop 12 to
lessen the force needed to exit the body member 10. Decreasing the
force needed to exit the body member 10 increases the remaining
force available to penetrate deeper into the rock formation. When
the perforating charges are detonated, the perforating jet should
exit the body member 10 of the perforating gun at the center of the
scallop 12 where the bottom flat section of the scallop has reduced
the steel of the body member 10 to its minimum thickness. The
minimum thickness of the steel allows for less of the energy from
the perforating jet to be used to exit the body member 10 which
allows more energy to be available to penetrate into the rock
formation. The minimum thickness of the steel is balanced with the
need to have sufficient thickness of steel to withstand the
hydrostatic pressure exerted on the body member 10 along with
providing for thickness variations in the original body member
10.
[0033] The strength of the tubular hollow steel carrier body member
10 depends primarily upon the thickness and diameter of the
carrier. The greater the thickness of the body member 10 provides
additional strength. The smaller diameter of the body member 10
also serves to provide additional strength as the tighter arch of
the tubular hollow steel carrier body makes the body member able to
withstand greater forces. It is this same principle of the arch
shape providing additional strength, that allows the present
invention to remove more steel where the perforating jet exits the
body member 10 while still maintaining sufficient structural
integrity to resist the hydrostatic pressures. The additional
strength created by the arching geometric cut allows more steel to
be removed which in turn allows for greater penetration into the
rock formation. The structural dynamics of an arch distributes the
load laterally along the curvature of the arch.
[0034] The concept of the present invention and the preferred
embodiments all use a geometric cut with an arch. Using an arch in
the geometric shape of the cut could allow for many variations.
Testing of various shapes on various hollow steel carrier body
members has resulted in three preferred embodiments. These three
preferred embodiments are not the only possibilities applying the
concept of the present invention.
[0035] The first embodiment of the present invention is depicted in
a side view in FIG. 4 and in cross sections in FIG. 5 and FIG. 6.
This embodiment is a radius cut scallop 14. The radius cut scallop
14 is comprised of one continuous curved surface 16. The elliptical
shape of the radius cut scallop 14 is a result of the longitudinal
length of the scallop being longer with all of the scallop being a
curved surface with no flat area. The embodiment uses the strength
of the arch from the radius cut to allow for more steel to be
removed with less steel remaining for the perforating jet to
penetrate. The strength of the arch provides additional strength to
resist the hydrostatic forces of the wellbore fluids. Using the
same thickness of steel with a standard scallop would collapse
under the hydrostatic forces.
[0036] There are no known attempts to accomplish the result of the
present invention. There are however, two patents dealing with a
similar shape as the first embodiment of the present invention.
Schlumberger is a large manufacturer of perforating guns and has
two patents dealing with various geometric shapes of recessed areas
for perforations to reduce or control reflection of compression
waves generated in response to the perforating jet. These patents,
U.S. Pat. Nos. 6,460,463 B1 and 6,523,474 B2, provide for various
shapes of recessed areas to reduce compression waves resulting from
the explosive charge. The embodiments of these Schlumberger patents
are alterations to the standard Schlumberger recessed area,
referred to as the prior art in those patents, which is simply a
round flat bottom cut with ninety degree angle sides. Schlumberger
determined that the geometry of their standard recessed area
created these compression waves that cause interference that may
adversely affect the performance of the perforating jets. These
patents only mention that other types of recess geometries are
available, some may have generally elliptical shapes, which is the
standard industry elliptical scallop, and that such recess
geometries may come at the expense of the body member 10 integrity
as the recess may take up to much surface area of the body member
10 or remove too much body member 10 material. The present
invention and the three preferred embodiments are all based on
standard industry elliptical scallop for tubing guns and has
nothing to do with compression waves.
[0037] One of the many embodiments of the Schlumberger patents is
similar to the first embodiment of the present invention. Both
patents depict and describe an emdodiment that does not have
discrete bottom and side surfaces, that instead has a generally
arcuate or curvilinear surface that extends around the periphery of
the recess. It is further described as the arcuate surface of the
recess is generally semi-hemispherical in shape and has a bottom
surface portion that is continuous with a side surface portion
along an arc. This is all various ways of describing the
Sclumberger embodiment with some similarity to the radius cut 14
first embodiment of the present invention. So while these two
recessed areas for the perforation have generally simillar shape,
they are being utilized for totally different reasons. Schlumberger
uses the shape as one of its many variations to possibly reduce the
compression waves created from the Schlumberger prior art recessed
area. The shape is being used in the first embodiment of the
present invention for the reasons stated of using the strength of
the arch to allow a deeper cut removing more steel to be removed
which absorbs less energy and deeper penetrating of the perforating
jet into the rock formation.
[0038] The second embodiment of the present invention is depicted
in a side view in FIG. 7 and in cross sectional views in FIG. 8 and
FIG. 9. The second embodiment, the radius with a flat scallop 18,
is similar to the first embodiment in that there is a radius cut
with a curved surface 20, but the second embodiment also has a flat
portion 22 at the center of the scallop. The flat area 22 is
longitudinal resulting in the elliptical shape. The flat area 22 is
small relative to the rest of the radius with a flat scallop 18.
The arched portion of the radius with a flat scallop 18 provides
the additional strength to maintain the structural integrity while
removing more steel for a deeper penetration.
[0039] The third embodiment of the present invention is depicted in
a side view in FIG. 10 and in cross sectional views in FIG. 11 and
FIG. 12. Part of the third embodiment appears as an industry
standard elliptical scallop 26 with an additional longitudinal
arching cut 28 and is referred to as the double cut scallop 24. The
tightly arched longitudinal arching cut 28 creates a flat area at
the center of the scallop 30. While described as the double cut
scallop 24 because of its appearance, it is machined as one single
cut. Such tooling to produce this economically has not been
available until recently. The cross sectional views of the double
cut scallop 24 show how significantly more steel is removed
compared to the industry standard elliptical scallop 26. This third
embodiment again uses the strength of the arching cut to maintain
structural integrity while removing more steel for deeper
penetration.
[0040] Testing has been performed of various geometries including
the three embodiments on various sizes of hollow steel carrier body
members 10. The smaller diameter body members 10 have a smaller
arch which affords more strength and so more steel can be removed.
The larger diameter body members 10 have a larger arch which
affords less strength and so less steel can be removed. The first
embodiment, radius cut scallop 14, is the most amount of steel to
penetrate and affords the most strength. The second embodiment,
radius with a flat scallop 18, has less steel to penetrate and
affords less strength than the first embodiment. The even larger
flat portion of the third embodiment, double cut scallop 24,
affords less strength than either the first or second embodiments
and is compensated for by the tighter inside arch. For these
reasons, the first embodiment, radius cut scallop 14, is for larger
diameter body members 10 of more than four inches. The second
embodiment, radius cut with a flat scallop 18, is for medium
diameter body members 10 of two and one half to four inches. The
third embodiment, double cut scallop 24, is for smaller diameter
body members 10 of less than two and one half inches.
[0041] The design of the present invention and the three preferred
embodiments are much better suited, over the prior art, to
accomplish the objectives stated as well as those inherent therein.
While the three preferred embodiments of the present invention have
been described, numerous changes could be made by those skilled in
the art which are encompassed within the spirit of the invention as
described.
* * * * *