U.S. patent application number 17/189366 was filed with the patent office on 2022-03-10 for asymmetric initiated shaped charge and method for making a slot-like perforation.
The applicant listed for this patent is GEODYNAMICS, INC.. Invention is credited to Wenbo YANG.
Application Number | 20220074719 17/189366 |
Document ID | / |
Family ID | 1000006009894 |
Filed Date | 2022-03-10 |
United States Patent
Application |
20220074719 |
Kind Code |
A1 |
YANG; Wenbo |
March 10, 2022 |
ASYMMETRIC INITIATED SHAPED CHARGE AND METHOD FOR MAKING A
SLOT-LIKE PERFORATION
Abstract
A shaped charge is configured to make a non-circular perforation
into a casing. The shaped charge includes a case having a side wall
that extends between an open top region and a base; an asymmetric
initiation insert configured to fit within the case; an explosive
material placed over the asymmetric initiation insert and in
contact with the side wall of the case; and a liner placed over the
explosive material, to hold the explosive material within the case.
The asymmetric initiation insert has a body that includes first and
second channels that extend from a bottom surface to a top surface
of the body, so that a detonation at the bottom surface is directed
to first and second initiation points, that correspond to the first
and second channels.
Inventors: |
YANG; Wenbo; (Kennedale,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GEODYNAMICS, INC. |
Millsap |
TX |
US |
|
|
Family ID: |
1000006009894 |
Appl. No.: |
17/189366 |
Filed: |
March 2, 2021 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
62984420 |
Mar 3, 2020 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F42B 1/036 20130101;
E21B 43/117 20130101; F42B 1/028 20130101; F42B 3/22 20130101 |
International
Class: |
F42B 3/22 20060101
F42B003/22; F42B 1/036 20060101 F42B001/036; F42B 1/028 20060101
F42B001/028; E21B 43/117 20060101 E21B043/117 |
Claims
1. A shaped charge for making a non-circular perforation into a
casing, the shaped charge comprising: a case having a side wall
that extends between an open top region and a base; an asymmetric
initiation insert configured to fit within the case; an explosive
material placed over the asymmetric initiation insert and in
contact with the side wall of the case; and a liner placed over the
explosive material, to hold the explosive material within the case,
wherein the asymmetric initiation insert has a body that includes
first and second channels that extend from a bottom surface to a
top surface of the body, so that a detonation at the bottom surface
is directed to first and second initiation points, that correspond
to the first and second channels.
2. The shaped charge of claim 1, wherein the top surface of the
body is convex.
3. The shaped charge of claim 1, wherein the top surface of the
body is part of a sphere of a given radius R.
4. The shaped charge of claim 1, wherein the asymmetric initiation
insert fits tightly over the base and side wall of the case so that
no explosive material is present at an interface between the
asymmetric initiation insert and the case.
5. The shaped charge of claim 1, further comprising: a booster
material placed in a conduit formed in the base of the case,
wherein the conduit is configured to drive a flame from the booster
material to the first and second channels of the asymmetric
initiation insert.
6. The shaped charge of claim 1, further comprising: a booster
material placed in a conduit formed in the base of the case,
wherein the booster material is in direct contact with the first
and second channels.
7. The shaped charge of claim 1, wherein each of the first and
second channels is fully formed within the body of the asymmetric
initiation insert.
8. The shaped charge of claim 1, wherein each of the first and
second channels is partially open to a side of the asymmetric
initiation insert.
9. The shaped charge of claim 1, wherein the first and second
channels are cylinders having a constant radius.
10. The shaped charge of claim 1, wherein the first and second
channels are conical frustums.
11. A perforating gun for perforating a casing in a well, the
perforating gun comprising: a casing; and a shaped charge provided
within the casing and configured to make a non-circular perforation
into the casing, wherein the shaped charge includes an asymmetric
initiation insert having a body that includes first and second
channels that extend from a bottom surface to a top surface of the
body, so that a detonation at the bottom surface is directed to
first and second initiation points, that correspond to the first
and second channels, and wherein the first and second initiation
points make the shaped charge to form a non-circular perforation
into the casing.
12. The perforating gun of claim 11, wherein the shaped charge
comprises: a case having a side wall that extends between an open
top region and a base; the asymmetric initiation insert is
configured to fit within the case; an explosive material placed
over the asymmetric initiation insert and in contact with the side
wall of the case; and a liner placed over the explosive material,
to hold the explosive material within the case.
13. The perforating gun of claim 12, wherein the top surface of the
body is convex.
14. The perforating gun of claim 12, wherein the top surface of the
body is part of a sphere of a given radius R.
15. The perforating gun of claim 12, wherein the asymmetric
initiation insert fits tightly over the base and side wall of the
case so that no explosive material is present at an interface
between the asymmetric initiation insert and the case.
16. The perforating gun of claim 12, wherein the shaped charge
further comprises: a booster material placed in a conduit formed in
the base of the case, wherein the conduit is configured to drive a
flame from the booster material to the first and second channels of
the asymmetric initiation insert.
17. The perforating gun of claim 12, wherein each of the first and
second channels is fully formed within the body of the asymmetric
initiation insert.
18. The perforating gun of claim 12, wherein the first and second
channels of the asymmetric initiation insert are cylinders having a
constant radius.
19. The perforating gun of claim 12, wherein the first and second
channels of the asymmetric initiation insert are conical
frustums.
20. A method of manufacturing a shaped charge that generates a
non-circular perforation in a casing, the method comprising:
providing a case for the shaped charge; placing an asymmetric
initiation insert within the case; orienting angularly the
asymmetric initiation insert relative to the case to achieve a
desired orientation of the non-circular perforation relative to the
casing; placing an explosive material over the asymmetric
initiation insert and in contact with a side wall of the case; and
placing a liner over the explosive material, to hold the explosive
material within the case, wherein the asymmetric initiation insert
has a body that includes first and second channels that extend from
a bottom surface to a top surface of the body, so that a detonation
at the bottom surface is directed to first and second initiation
points at the top surface, which correspond to the first and second
channels.
Description
BACKGROUND
Technical Field
[0001] Embodiments of the subject matter disclosed herein generally
relate to shaped charges and associated perforations made in the
casing of a well, and more specifically, to a shaped charge that is
configured to be asymmetrically initiated for generating a
slot-like jet of material for perforating the casing to obtain a
slot-like perforation profile.
Discussion of the Background
[0002] In the oil and gas field, once a well is drilled to a
desired depth H relative to the surface, and the casing protecting
the wellbore has been installed and cemented in place, it is time
to connect the wellbore to the subterranean formation and to
extract the oil and/or gas. This process of connecting the wellbore
to the subterranean formation may include a step of plugging with a
well a previously fractured stage of the well, a step of
perforating a new stage of the casing with a perforating gun system
(that includes plural guns) such that plural channels are formed to
connect the subterranean formation to the inside of the casing, a
step of removing the perforating gun system after all the desired
stages have been perforated, and a step of pumping to the surface
the oil that enters the casing through the formed plural
channels.
[0003] However, after the oil pressure in the formation becomes
smaller than the hydrostatic pressure in the well, the natural oil
flow from the formation into the casing diminishes, and the oil
production ceases, although oil is still trapped in the formation.
For these wells, a fracturing operation may be applied to extend
their lifespan. A typical fracturing operation uses a slurry of a
proppant (sand) and a liquid (water), which is pumped into each
stage at high rates. The slurry enters then through the holes
(perforations) made by the gun system into the casing, into the
channels made in the formation by the same gun systems and
hydraulically fractures the formation to open up the channels and
allow the remaining oil to flow into the casing.
[0004] The amount of the slurry that flows through each perforation
made into the casing may vary based upon a variety of factors. For
example, one such factor is the shape of the perforation. The shape
of the perforation depends on the type of the shaped charged used
in the gun system for perforating the casing. The typical shaped
charge is shown in FIG. 1 and is symmetrical along the longitudinal
axis Y. The shaped charge 100 has a case 110 that is made of metal
and is itself symmetrical relative to the axis Y. The case 110
holds an explosive material 112, which is kept in place by a liner
114. The liner is typically made of a metallic material. Both the
explosive material 112 and the liner 114 are also symmetrically
distributed relative to the axis Y. The base 111 of the case 110 is
filled with a detonation material 120, which is configured to
detonate the explosive material 112. A hole 122 into the base 111
of the case 110 allows a detonator cable 130 or a booster material
(not shown) to detonate the detonation material 120.
[0005] The problem with these symmetrical shaped charges is that
there is only one initiation point A of the explosive material 112
and thus, when the liner 114 collapses due to the pressure
generated by the explosion of the explosive material 112, the jet
of material 140 formed from the liner 114 is very symmetrical about
the longitudinal axis Y (i.e., is shaped as a cylinder), and this
jet, when penetrating the casing (not shown) and the formation (not
shown) would typically generate a round perforation and a round
channel, respectively.
[0006] Having round perforations in the casing and/or round
channels in the formation has been found over time to pose the
following problem. Assuming that the diameter of the perforations
is D1, and the average diameter of the particles in the slurry is
D2, which is smaller than D1, over time, if the D1 is not at least
six times larger than D2, the particles start to accumulate at the
edge of the perforation and over time, they form a bridge, which
diminishes if not suppresses the amount of the slurry that flows
from the casing into the formation. This is undesirable because the
fracturing operation relies on the slurry travelling at a desired
rate from the casing into the formation.
[0007] To prevent this problem, there are efforts in the field to
make slot-type perforations instead of round perforations. A
slot-type perforation is understood herein to be a perforation or
hole that is made in the casing with a shaped charge and has a
shape more similar to a rectangle or square, i.e., a slot, than to
a circle. In other words, a slot-type perforation is a non-circular
perforation. To obtain slot-type perforations, various shaped
charge manufacturers have tried to make the shaped charge
non-symmetrical along the Y axis, by either manipulating the shape
of the case, by providing plural initiation points by making
corresponding plural holes into the case, or by adding various
inserts in the explosive material to influence the shaped of the
jet 140.
[0008] However, such approaches are complicated as they required to
modify the case for making more initiation points, or to make an
asymmetrical case, or to add various inserts in the explosive
material. Further, such approaches are case specific, meaning that
each shaped charge manufacturer has to modify differently its
manufacturing process. Furthermore, these approaches cannot be used
with the existing shaped charge's cases, and thus, require further
investments and developing new manufacturing capabilities.
[0009] The slot-type perforations are also used for plug and
abandonment operations. At the end of life of the well, special
procedures are implemented for sealing the well and ensuring that
the formations around the well are pressure isolated so that
contamination between different formations is minimized. For these
operations, non-circular slots are desired to be made in the casing
of the well.
[0010] Thus, there is a need to form slot-type perforations into
the well's casing with an existing shaped charge's case, and to
achieve these results with an easy to manufacture shaped charge,
that require inexpensive modifications when compared to a
traditional shaped charge.
SUMMARY
[0011] According to an embodiment, there is a shaped charge for
making a non-circular perforation into a casing. The shaped charge
includes a case having a side wall that extends between an open top
region and a base, an asymmetric initiation insert configured to
fit within the case, an explosive material placed over the
asymmetric initiation insert and in contact with the side wall of
the case, and a liner placed over the explosive material, to hold
the explosive material within the case. The asymmetric initiation
insert has a body that includes first and second channels that
extend from a bottom surface to a top surface of the body, so that
a detonation at the bottom surface is directed to first and second
initiation points, that correspond to the first and second
channels.
[0012] According to another embodiment, there is a perforating gun
for perforating a casing in a well and the perforating gun includes
a casing and a shaped charge provided within the casing and
configured to make a non-circular perforation into the casing. The
shaped charge includes an asymmetric initiation insert having a
body that includes first and second channels that extend from a
bottom surface to a top surface of the body, so that a detonation
at the bottom surface is directed to first and second initiation
points, that correspond to the first and second channels. The first
and second initiation points make the shaped charge for form a
non-circular perforation into the casing.
[0013] According to still another embodiment, there is a method of
manufacturing a shaped charge that generates a non-circular
perforation in a casing. The method includes providing a case for
the shaped charge; placing an asymmetric initiation insert within
the case; orienting angularly the asymmetric initiation insert
relative to the case to achieve a desired orientation of the
non-circular perforation relative to the casing; placing an
explosive material over the asymmetric initiation insert and in
contact with a side wall of the case; and placing a liner over the
explosive material, to hold the explosive material within the case.
The asymmetric initiation insert has a body that includes first and
second channels that extend from a bottom surface to a top surface
of the body, so that a detonation at the bottom surface is directed
to first and second initiation points at the top surface, which
correspond to the first and second channels.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate one or more
embodiments and, together with the description, explain these
embodiments. In the drawings:
[0015] FIG. 1 illustrates a traditional shaped charge that is fully
symmetrical around a longitudinal axis;
[0016] FIG. 2 illustrates a novel shaped charge that has an
asymmetric initiation insert for generating a slot-type perforation
in a casing;
[0017] FIG. 3 illustrates another novel shaped charge that has an
asymmetric initiation insert for generating a slot-type perforation
in a casing;
[0018] FIG. 4A illustrates the shaped charge having the asymmetric
initiation insert with two channels that are shaped as conical
frustums;
[0019] FIG. 4B illustrates the shaped charge having the asymmetric
initiation insert with two channels that are shaped as
cylinders;
[0020] FIGS. 5A to 5C illustrate the location of the channels made
in the body of the asymmetric initiation insert for a varying
number of channels;
[0021] FIGS. 6A and 6B illustrate partially open channels made in
the body of the asymmetric initiation insert;
[0022] FIG. 7 illustrates in more detail the top and bottom
surfaces of the asymmetric initiation insert;
[0023] FIG. 8 illustrates a perforating gun system having a gun
that includes the shaped charge with the asymmetric initiation
insert;
[0024] FIG. 9 shows a slot formed into the casing by the shaped
charge having the asymmetric initiation insert;
[0025] FIG. 10 illustrates the relative position of the perforating
gun inside the casing of a well and the various angles at which the
shaped charges of the perforating gun are oriented;
[0026] FIG. 11 illustrates actual slots formed in the casing of the
well with the shaped charges having the asymmetric initiation
insert;
[0027] FIG. 12 illustrates the sizes and angle distribution of the
slots formed in the well's casing with the shaped charges of FIG.
4A;
[0028] FIG. 13 illustrates the sizes and angle distribution of the
slots formed in the well's casing with the shaped charges of FIG.
4B; and
[0029] FIG. 14 is a flowchart of a method for making a shaped
charge having the asymmetric initiation insert.
DETAILED DESCRIPTION
[0030] The following description of the embodiments refers to the
accompanying drawings. The same reference numbers in different
drawings identify the same or similar elements. The following
detailed description does not limit the invention. Instead, the
scope of the invention is defined by the appended claims. The
following embodiments are discussed, for simplicity, with regard to
a perforating gun system used for perforating a casing in a well.
However, the embodiments discussed herein may be used for guns in
another context.
[0031] Reference throughout the specification to "one embodiment"
or "an embodiment" means that a particular feature, structure or
characteristic described in connection with an embodiment is
included in at least one embodiment of the subject matter
disclosed. Thus, the appearance of the phrases "in one embodiment"
or "in an embodiment" in various places throughout the
specification is not necessarily referring to the same embodiment.
Further, the particular features, structures or characteristics may
be combined in any suitable manner in one or more embodiments.
[0032] According to an embodiment, a shaped charge includes, in
addition to a case, an explosive material, a liner, and a booster
material, an asymmetric initiation insert that makes (1) the
explosive material to be initiated from at least two different
locations, and (2) the initiation to be asymmetrical relative to a
longitudinal axis Y of the shaped charge's case. The longitudinal
axis Y may be a symmetry axis for the case, but not for the
asymmetric initiation insert. In one application, the longitudinal
axis is a symmetry axis for each element of the shaped charge, but
for the asymmetric initiation insert. The asymmetric initiation
insert may be made of an inexpensive material, for example,
plastic, resin, or even a metal. In one application, the asymmetric
initiation insert may be 3D printed. In another application, the
asymmetric initiation insert may be added to any existing shaped
charge case, i.e., any shaped charge can be retrofitted to have the
asymmetric initiation insert. The asymmetric initiation insert can
be added manually or automatically by a robot to the shaped
charge's case. The details of the asymmetric initiation insert are
now discussed in more detail with regard to the figures.
[0033] FIG. 2 shows a shaped charge 200 having a case 210 that has
a base 212 and an open top region 214. The base 212 has a passage
216 that fluidly communicates the exterior of the case 210 with an
interior chamber 218, which is defined by the lateral wall 211 of
the case 210. The passage 216 of the base 212 is connected to a
conduit 219, provided on the outside of the case, and configured to
receive a blast from a detonator cord 217. The conduit 219 has an
internal chamber that together with the passage 216 are configured
to receive a booster material 232, as discussed later. In one
application, the booster material 232 partially extends into the
passage 216.
[0034] An asymmetric initiation insert 220 is placed inside chamber
218, close to the base 212. The insert 220 is shaped in this
embodiment to have a frustoconical body, i.e., a truncated cone. In
one application, the top surface of the frustoconical body is
curved (e.g., convex) and the bottom surface is flat. In one
application, the asymmetric initiation insert 220 is in direct
contact to the base 212. Although the asymmetric initiation insert
220 is shown in FIG. 2 to be placed in direct contact with the base
212, in another embodiment, as illustrated in FIG. 3, the
asymmetric initiation insert 220 is placed away from the base 212.
For the embodiment illustrated in FIG. 3, there is a space 222
between the asymmetric initiation insert 220 and the wall 211 of
the case 210 all around the insert 220. The asymmetric initiation
insert 220 can be placed to be away from the wall 211 either by
first packing part of the explosive material 230 on the base 212
and then adding the asymmetric initiation insert 220, or by
manufacturing the asymmetric initiation insert 220 to have small
spacers or legs 224, which are configured to extend from the insert
and sit directly on the base 212 of the case 210.
[0035] Returning to the embodiment shown in FIG. 2, the explosive
material 230 is placed over the asymmetric initiation insert 220,
and a liner 240 is added over the explosive material 230, to fix
the explosive material between the insert 220, the wall 211, and
the liner 240. The volume of the chamber 218 is thus fully loaded
with the explosive material 230. To achieve a blast connection
between the detonation cord 217 and the explosive material 230, the
booster material 232 may be placed inside the passage 216. The
booster material 232 ensures that the fire wave that is initiated
by the detonation cord 217 propagates inside the case 210, toward
the explosive material 230. The explosive material 230 and the
booster material 232 may include any one or more of the following
materials: RDX, HMX, HNS, PYX, NONA, ONT, TATB, HNIW, TNAZ, PYX,
BRX, PETN, CL-20, NL-11, or any another suitable explosive known in
the art.
[0036] To allow the fire wave to propagate from the cord 217 to the
explosive material 230, the asymmetric initiation insert 220 may
have two or more channels 226 that extend through the entire body
of the insert (FIG. 2 shows only one channel due to the angle of
the view). In one embodiment, the booster material 232 is in direct
contact with the channels 226. FIGS. 4A and 4B show the insert 220
having two channels 226-1 and 226-2 that extend from a top surface
220A to a bottom surface 220B of the insert. In the embodiments
shown in FIGS. 4A and 4B, each channel is fully formed inside the
body 221 of the insert 220. Further, the embodiment shown in FIG.
4A has each of the channels 226-1 and 226-2 shaped as a conical
frustum, with the smaller diameter toward the base 212 of the case
210, or toward the bottom surface 220B of the insert 220, and the
larger diameter toward the opening 214 of the case 210, or toward
the top surface 220A of the insert 220. In this way, two initiation
points 228A and 228B are provided for the explosive material
230.
[0037] The two initiation points are asymmetrical, i.e., they are
not provided on the longitudinal axis Y. Further, the two
initiation points are provided while the base 212 of the case 210
has only one passage 216. In addition, the two initiation points
228A and 228B are on the top surface 220A of the body 221, i.e.,
within the top surface 220A. The embodiment illustrated in FIG. 4B
has the two channels 226-1 and 226-2 shaped as cylinders, i.e.,
having a constant diameter along their lengths. The angle .alpha.
between (1) each longitudinal axis of the channels 226-1 and 226-2
and (2) the axis Y, which is normal to the base 220B of the insert
220, is the same. The angle may take any desired value. FIGS. 4A
and 4B further show that an interface 250 between the side and
bottom surfaces of the insert 220 and the case 210 may be so small
that no explosive material 230 can fit there. This means that the
insert 220 may be manufactured to exactly fit at the bottom of the
case 210. However, if some explosive material is desired to be
present at that interface, the insert 220 size may be modified to
achieve such clearance.
[0038] The number of the channels 226 made in the body 221 of the
insert 220 may vary from 2 to N, where N is a natural number
between 3 and 30. The angular distribution of the channels 226
relative to the top surface 220A is illustrated in FIGS. 5A to 5C.
More specifically, FIG. 5A shows only two channels 226-1 and 226-2
located opposite to each other, i.e., making a 180 degrees angle on
an angular axis. FIG. 5B shows four channels 226-1 to 226-4 formed
into the top surface 220A, each adjacent pair of channels making a
90 degrees angle relative to an angular axis. FIG. 5C shows an
embodiment in which there are three channels 226-1 to 226-3 on the
top surface 220A, each two adjacent channels making an angle of 120
degrees. It is noted that in one embodiment, it is preferred that
the number of channels used are distributed with the same angular
distance. However, those skilled in the art would understand from
this disclosure that is also possible to change these angles if the
shape of the perforation hole in the casing of the gun system needs
to be adjusted or changed. The distribution of holes made in the
base 220B of the body 221, which correspond to the channels 226,
would be similar to those made in the top surface 220A shown in
FIGS. 5A to 5C. These bottom holes are illustrated by the dash
lines in the figures. However, the difference is that the bottom
holes are distributed closer to the central point of the base than
the top holes. FIGS. 5A to 5C also show that the top and bottom
holes that correspond to opposite channels, if projected on the
same plane, would lie on the same line.
[0039] While FIGS. 4A and 4B show that the top surface 220A of the
insert 220 is convex, it is also possible to have the top surface
shaped to be concave or even flat. A distance D between the top
point of the top surface 220A and the vertex 242 of the liner 240
(see FIG. 4A) can be selected so that the desired slot-type
perforation is obtained in the casing of the gun system. The
channels 226 may be fully filed with the explosive material 230,
the booster material 232, or with a combination of the two
materials.
[0040] While FIGS. 4A to 5C show the channels 226 being fully
formed within the body 221 of the insert 220, it is also possible,
as illustrated in FIGS. 6A and 6B, to have the channels only
partially formed within the body 221. More specifically, FIGS. 6A
and 6B show that a side of the channels is open to the ambient,
i.e., the channel is not fully enclosed by the body 221. While
FIGS. 6A and 6B show only two channels being partially exposed to
the ambient, any number of the channels in a given insert may be
exposed to the ambient. FIG. 6B further shows that about half of
the channel's cross-section is formed in the body 221. However, any
percentage of the channel's cross-section may be formed within the
body 221. Note that in one embodiment, when the insert 220 is
placed inside the case 210, the lateral sides of the insert 220
directly contact the internal surface of the case 210, i.e., there
is no explosive material 230 at an interface between the sides of
the case 210 and the sides of the insert 220. However, if the
configuration shown in FIG. 6A is implemented, i.e., the channels
226 of the insert 220 are open to the ambient, then the explosive
material may be present between the sides of the case 210 and the
open channels 226.
[0041] FIG. 7 shows a longitudinal cross-section of the insert 220,
having two channels 226-1 and 226-2. The top surface 220A is shown
to be curved. The top surface 220A can be parametrized as it is
selected to describe a desired curvature. For example, it is
possible that the top surface 220A is part of a sphere having a
given radius R. The radius R can be in the mm or cm range. In
another embodiment, the top surface 220A can be described as part
of an ellipse, which is characterized by a semi-minor axis a and a
semi-major axis b. In yet another embodiment, the top surface 220A
can be described as part of a parabola, which is characterized by
three parameters a, b, and c. Other shapes may be selected for the
top surface 220A. The bottom surface or base 220B may be selected
to be planar, or to have any other profile that will match the
internal wall of the shaped charge base. It is noted that the shape
of the insert 220 may be selected to intimately match the inside of
the base and lateral walls of any shaped charge.
[0042] The embodiments discussed herein illustrate various
possibilities of providing two or more initiation points for the
explosive material 230. Also, the embodiments discussed herein
alter the speed of the explosive initiation at the different points
so that the shockwave and pressure generated by the explosion of
the explosive material 230 does not happen in a radial or circular
pattern, as with the traditional shaped charge of FIG. 1, thus
generating a jet 140 having a non-circular shape, which is
responsible for the slot-type perforation in the casing of the gun
system and the channels in the formation. In addition, the insert
220 discussed herein can be implemented in any existing shaped
charge, and does not require expensive or difficult additional
manufacturing steps when loading the case of the shaped charge.
[0043] Because this novel insert 220 would make the shaped charge
200 to generate a slot-type perforation into the casing of the gun
system, it is possible to orient the insert to obtain the slot-type
oriented in a desired way relative to the casing of the gun system.
In this regard, FIG. 8 shows a perforating gun system 800 that
includes a first perforating gun 810, a second perforating gun 820,
and a connecting or tandem sub 830 that physically connects the two
perforating guns to each other. The perforating gun 810 has a
casing 812 that fully encloses the various shaped charges 200-I
provided inside the gun. The shaped charges 200-I are distributed
in this embodiment along a spiral inside the casing. The figure
shows that a first shaped charge 200-1 has the first and second
channels 226-1 and 226-2 (only the first channel is visible in the
figure) arranged along a line 814, the second shaped charge 200-2
has the two channels arranged along a line 816, and the shaped
charge 200-I has the two channels arranged along a line 818. The
three lines 814 to 818 are shown in the figure having different
orientations. However, the inserts 220 may be oriented inside the
corresponding shaped charges to obtain the same orientation of the
lines 814 to 818. This orientation is related to the desired
orientation of the slot-type perforations, which is schematically
illustrated in the figure with the corresponding slots 815 to 819.
It is noted that the longitudinal axis of each slot is
substantially perpendicular to the line that passes through the
corresponding two channels in this embodiment. These slots are
expected to be formed in the casing 812 of the gun 810,
corresponding to each shaped charge, as schematically illustrated
in FIG. 9. Thus, depending on the needs of the well's operator, the
orientation of the slots in the casing can be controlled by the
orientation of the insert 220 in the shaped charge 200. For this
purpose, the insert 220 can be marked with an orientating feature
upon its surface, for example, a tab, wing, slot or similar mark,
to indicate the orientation of its channels, so that the insert can
be clocked accordingly to the case of the shaped charge and/or the
casing of the gun.
[0044] The capabilities of the inserts 220 discussed above have
been tested as now discussed. FIG. 10 shows in transversal
cross-section the gun 810, its casing 812, a single shaped charge
200 having an insert 220, all of which are placed in a casing 1010
of a well. The well is horizontal and thus, the casing 812 of the
gun 810 sits with a bottom portion on the casing 1010 of the well.
This means that a fluid 1020 inside the well's casing has a maximum
volume at 180 degrees along an angular axis ANG, and zero volume at
the origin of the axis ANG. The figure shows various angular
positions around the casing 1010 and these positions correspond to
the plural shaped charges (not shown) included in the one or more
guns 810. It is noted that the amount of fluid between the gun's
casing 812 and the well's casing 1010 negatively impacts the well
perforation as the jet formed when the shaped charge is fired loses
energy when interacting with the fluid 1020.
[0045] FIG. 11 shows actual slots 817 formed in plural well's
casings 1010 for various angles, which are listed on the left side
of the figure, for each casing. Further, the slots 817 at the left
of each casing were made with the configuration of the insert shown
in FIG. 4A (i.e., channels that increase in diameter toward the top
surface 220A of the insert 220) while the slots 817 at the right of
each casing where made with the configuration of the insert shown
in FIG. 4B (i.e., channels that have a constant diameter). It is
noted that the shape of the slots 817 is much closer to a rectangle
than a circle, which is the desired goal of the insert 220.
[0046] FIG. 12 shows a table with the results for various shots
that use the configuration of the insert shown in FIG. 4A. FIG. 12
shows the slots 817 obtained for multiple shots, each shot being
characterized by the phasing angle (the angles shown in FIG. 10),
and the water clearance (the distance between the exterior of the
casing of the gun and the interior of the casing of the well). Each
slot is characterized by a long axis L1 of the hole made in the
casing and a short axis L2 of the same hole, i.e., the length and
width of the slot. FIG. 13 shows similar results when the insert
shown in FIG. 4B is used. It is noted that in both cases, the slots
are close to a rectangle, as desired.
[0047] FIG. 14 illustrates a method for assembling an asymmetric
initiated shaped charge 200. The method starts in step 1400 with
providing the case of the shaped charge. In optional step 1402, the
booster material 232 is placed in the passage 216. In step 1404,
the insert 220 is placed inside the case 210, by inserting it from
the open end 214 until reaching the base 212. The insert 220 may be
simply left as is inside the case 210, or it may be attached with a
glue like substance to the inside of the case. In step 1406, either
the booster material 232 or the explosive material 230 may be
placed inside the channels 226 or both materials may be placed in a
desired proportion. In optional step 1408, the insert 220 is
clocked relative to a longitudinal axis of the gun to generate the
slot-type perforation with a desired orientation relative to the
longitudinal axis. In step 1410, a desired amount of the explosive
material 230 is placed inside the case 210, over the insert 220. In
step 1412, the liner 240 is placed over the explosive material 230
to seal it inside the case 210.
[0048] The disclosed embodiments provide methods and systems for
generating a slot-like hole perforation into a casing of a well, by
using at least an asymmetric initiated shaped charge. It should be
understood that this description is not intended to limit the
invention. On the contrary, the exemplary embodiments are intended
to cover alternatives, modifications and equivalents, which are
included in the spirit and scope of the invention as defined by the
appended claims. Further, in the detailed description of the
exemplary embodiments, numerous specific details are set forth in
order to provide a comprehensive understanding of the claimed
invention. However, one skilled in the art would understand that
various embodiments may be practiced without such specific
details.
[0049] Although the features and elements of the present exemplary
embodiments are described in the embodiments in particular
combinations, each feature or element can be used alone without the
other features and elements of the embodiments or in various
combinations with or without other features and elements disclosed
herein.
[0050] This written description uses examples of the subject matter
disclosed to enable any person skilled in the art to practice the
same, including making and using any devices or systems and
performing any incorporated methods. The patentable scope of the
subject matter is defined by the claims, and may include other
examples that occur to those skilled in the art. Such other
examples are intended to be within the scope of the claims.
* * * * *