U.S. patent application number 17/049352 was filed with the patent office on 2021-08-19 for top set plug and method.
The applicant listed for this patent is GEODYNAMICS, INC.. Invention is credited to Dennis ROESSLER, Wayne ROSENTHAL, Michael WROBLICKY.
Application Number | 20210254428 17/049352 |
Document ID | / |
Family ID | 1000005608152 |
Filed Date | 2021-08-19 |
United States Patent
Application |
20210254428 |
Kind Code |
A1 |
ROESSLER; Dennis ; et
al. |
August 19, 2021 |
TOP SET PLUG AND METHOD
Abstract
A top set plug for sealing against a casing of a well. The plug
includes a mandrel having a throughout bore that extends from a top
end to a bottom end; a connecting mechanism located at the top end
of the mandrel; a sealing element located around the mandrel and
configured to be pushed toward an internal wall of the casing; an
upper wedge configured to push the sealing element against the
casing; and a slip ring configured to push the sealing element over
the upper wedge and also to engage the inner wall of the casing
with buttons for preventing the plug to slide along the casing.
Inventors: |
ROESSLER; Dennis; (Fort
Worth, TX) ; WROBLICKY; Michael; (Weatherford,
TX) ; ROSENTHAL; Wayne; (Cleburne, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GEODYNAMICS, INC. |
Millsap |
TX |
US |
|
|
Family ID: |
1000005608152 |
Appl. No.: |
17/049352 |
Filed: |
February 13, 2020 |
PCT Filed: |
February 13, 2020 |
PCT NO: |
PCT/US20/18031 |
371 Date: |
October 21, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62808574 |
Feb 21, 2019 |
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|
62941075 |
Nov 27, 2019 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 23/0413 20200501;
E21B 2200/08 20200501; E21B 33/13 20130101 |
International
Class: |
E21B 33/13 20060101
E21B033/13; E21B 23/04 20060101 E21B023/04 |
Claims
1. A top set plug for sealing against a casing of a well, the plug
comprising: a mandrel having a throughout bore that extends from a
top end to a bottom end; a connecting mechanism located at the top
end of the mandrel, wherein the connecting mechanism is configured
to connect to a setting tool and the connecting mechanism is
attached with a shear member to the mandrel; a sealing element
located around the mandrel and configured to be pushed toward an
internal wall of the casing; an upper wedge configured to push the
sealing element against the casing; and a slip ring configured to
push the sealing element over the upper wedge and also to engage
the inner wall of the casing with buttons for preventing the plug
to slide along the casing, wherein the shear member is manufactured
to break before any other part of the mandrel to release the
connecting mechanism, and wherein there is no lower wedge to push
against the sealing element.
2. The plug of claim 1, wherein the mandrel has a deep seat formed
away from the top and bottom ends of the mandrel.
3. The plug of claim 2, wherein the deep seat is formed directly
across from the slip ring, or directly across from the upper wedge,
or directly across from the sealing element.
4. The plug of claim 1, wherein the slip ring is the only slip ring
of the plug.
5. The plug of claim 1, further comprising: a second seat formed at
an end of the mandrel, away from the deep seat.
6. The plug of claim 1, wherein the mandrel has a seat formed at
the top end.
7. The plug of claim 1, wherein the entire plug is formed of one or
more dissolvable materials.
8. The plug of claim 1, wherein at least one of the mandrel, the
sealing element, the upper wedge, and the slip ring are formed from
a dissolvable material.
9. The plug of claim 1, further comprising: a guiding element
fixedly attached to the bottom end of the mandrel.
10. The plug of claim 1, wherein the mandrel has a flared-up part
that is configured to push the upper wedge toward the sealing
element and also radially away from a longitudinal axis of the
mandrel.
11. A top set plug for sealing against a casing of a well, the plug
comprising: a mandrel having a throughout bore that extends from a
top end to a bottom end; a connecting mechanism that is configured
to connect to a setting tool, wherein the connecting mechanism is
attached through a shear member to the mandrel; a sealing element
partially located around the mandrel and having a top end and a
bottom end, wherein the top end is configured to be pushed toward
an internal wall of the casing and acts as a seal while the bottom
end is configured as a ramp; and a slip ring configured to engage
the inner wall of the casing with buttons for preventing the plug
to slide along the casing, wherein the bottom end of the sealing
element enters into a bore of the slip ring and pushes the slip
ring radially outward toward the inner wall of the casing, and
wherein the shear member is manufactured to break before any other
part of the mandrel to release the connecting mechanism.
12. The plug of claim 11, wherein the mandrel has a deep seat
formed away from the top and bottom ends of the mandrel.
13. The plug of claim 12, wherein the deep seat is formed directly
across from the slip ring.
14. The plug of claim 12, wherein the deep seat is formed directly
across from the sealing element.
15. The plug of claim 11, wherein the entire plug is formed of one
or more dissolvable materials.
16. The plug of claim 11, wherein the sealing element is the first
element of the plug at the upstream end of the plug.
17. The plug of claim 11, further comprising: a guiding element
fixedly attached to the bottom end of the mandrel.
18. A method for plugging a casing in a well, the method
comprising: attaching a setting tool to a frac plug, wherein a ball
is placed inside the setting tool; lowering the setting tool, the
ball and the frac plug to a desired depth into the casing of the
well; activating the setting tool to set up the frac plug, wherein
a connection between the setting tool and the frac plug is located
at a top end of the frac plug; removing the setting tool after the
connection between the setting tool and the frac plug is broken;
and pressuring the ball to seat onto a seat formed into a mandrel
of the frac plug.
19. The method of claim 18, wherein the seat is a deep seat, which
is located away from the top end and a bottom end of the mandrel,
to provide structural support to the frac plug.
20. The method of claim 18, wherein the frac plug has only an upper
wedge and not a lower wedge.
21. The method of claim 18, wherein one or more elements of the
frac plug are made of a dissolvable material.
Description
BACKGROUND
Technical Field
[0001] Embodiments of the subject matter disclosed herein generally
relate to downhole tools used for perforating and/or fracturing
operations, and more specifically, to a downhole plug that is
configured to be set from its top.
Discussion of the Background
[0002] In the oil and gas field, once a well 100 is drilled to a
desired depth H relative to the surface 110, as illustrated in FIG.
1, and the casing 102 protecting the wellbore 104 has been
installed and cemented in place, it is time to connect the wellbore
104 to the subterranean formation(s) 106 to extract the oil and/or
gas. This process of connecting the wellbore to the subterranean
formation may include a step of isolating a stage of the casing 102
with a plug 112, a step of perforating the casing 102 with a
perforating gun assembly 114 such that various channels 116 are
formed to connect the subterranean formations to the inside of the
casing 102, a step of removing the perforating gun assembly, and a
step of fracturing the various channels 116.
[0003] Some of these steps require to lower into the well 100 a
wireline 118 or equivalent tool, which is electrically and
mechanically connected to the perforating gun assembly 114, and to
activate the gun assembly and/or a setting tool 120 attached to the
perforating gun assembly. Setting tool 120 is configured to hold
the plug 112 prior to isolating a stage and also to set the plug.
FIG. 1 shows the setting tool 120 disconnected from the plug 112,
indicating that the plug has been set inside the casing.
[0004] FIG. 1 shows the wireline 118, which includes at least one
electrical connector, being connected to a control interface 122,
located on the ground 110, above the well 100. An operator of the
control interface may send electrical signals to the perforating
gun assembly and/or setting tool for (1) setting the plug 112 and
(2) disconnecting the setting tool from the plug. A fluid 124,
(e.g., water, water and sand, fracturing fluid, etc.) may be pumped
by a pumping system 126, down the well, for moving the perforating
gun assembly and the setting tool to a desired location, e.g.,
where the plug 112 needs to be deployed, and also for fracturing
purposes.
[0005] The above operations may be repeated multiple times for
perforating and/or fracturing the casing at multiple locations,
corresponding to different stages of the well. Note that in this
case, multiple plugs 112 and 112' may be used for isolating the
respective stages from each other during the perforating phase
and/or fracturing phase.
[0006] These completion operations may require several plugs run in
series or several different plug types run in series. For example,
within a given completion and/or production activity, the well may
require several hundred plugs depending on the productivity,
depths, and geophysics of each well. Subsequently, production of
hydrocarbons from these zones requires that the sequentially set
plugs be removed from the well. In order to reestablish flow past
the existing plugs, an operator must remove and/or destroy the
plugs by milling or drilling the plugs.
[0007] A typical frac plug for such operations is illustrated in
FIG. 2 and includes plural elements. For example, the frac plug 200
has a central, interior, mandrel 202 on which all the other
elements are placed. The mandrel acts as the backbone of the entire
frac plug. The following elements are typically added over the
mandrel 202: a top push ring 203, upper slip ring 204, upper wedge
206, elastic sealing element 208, lower wedge 210, lower slip ring
212, a bottom push ring 216, and a mule shoe 218.
[0008] When a setting tool 300 is used to set the frac plug 200, as
illustrated in FIG. 3, the setting tool 300 applies a force F on
the push ring 203 on one side and applies an opposite force on the
bottom push ring 216, from the other side. As a consequence of
these two opposite forces, the intermediate components of the plug
200 press against each other causing the sealing element 208 to
elastically expand radially and seal against the casing 102. Upper
and lower wedges 206 and 210 press not only on the seal 208, but
also on their corresponding slip rings 204 and 212, separating them
into plural parts and at the same time forcing the separated parts
of the slip rings to press radially against the casing. In this
way, the slip rings maintain the sealing element into a tension
state to seal against the casing of the well and prevent the
elastic sealing element from returning to its initial position.
When the upper and lower wedges 206 and 210 swage the elastic
sealing element to seal against the casing, the elastic sealing
element elastically deforms and presses against the entire
circumference of the casing.
[0009] Traditionally, the setting tool 300 has a main body 301 to
which is attached a setting sleeve 304, which contacts the upstream
end of the frac plug 200. A mandrel 306 of the setting tool 300
extends from the main body 301 all the way through a bore 201 of
the plug 200, until a distal end 306A of the mandrel exits the mule
shoe 218. A disk or nut 308 is attached to the distal end 306A of
the mandrel 306. If a disk is used, then a nut 310 may be attached
to the mandrel 306 to maintain in place the disk 308. An external
diameter D of the disk 308 is designed to fit inside the bore 201
of the mule shoe 218, but also to be larger than an internal
diameter d of the shear ring 216 or another element (e.g., a
collet) that may be used for engaging the mandrel.
[0010] Because the mandrel 306 extends through the entire frac plug
200 and the disk 308 applies a force on the bottom part (the part
closest to the toe of the well) of the frac plug, this type of plug
is called a bottom set plug. A disadvantage of such a plug is the
fact that a typical bottom set plug does not allow for an operation
that is known in the art as a "ball in place" mode, which means
that a ball that is used to close the bore 201 of the frac plug 200
is run into the wellbore along with the plug. This mode is in
contrast to a traditional mode in which the frac plug 200 is first
set up, the setting tool 300 is removed from the well, and then the
ball is pumped down the wellbore, from the surface, to seal the
bore 201 of the frac plug 200. Such an operation increases water
usage, costs, and operational inefficiency. Further, the frac plug
shown in FIG. 2 has many parts that need to fit together, which
increases its cost. Furthermore, when the frac operation is
completed, the frac plug needs to be removed, which is currently
achieved by milling it. This process further adds to the complexity
of the well exploration and also adds to the oil extraction cost,
as the milling operation is expensive and time consuming.
[0011] Thus, there is a need for a simplified plug design that has
fewer components, can be manufactured to be easily removable, and
also can perform the ball in place operation.
BRIEF SUMMARY OF THE INVENTION
[0012] According to an embodiment, there is a top set plug for
sealing against a casing of a well. The plug includes a mandrel
having a throughout bore that extends from a top end to a bottom
end, a connecting mechanism located at the top end of the mandrel,
wherein the connecting mechanism is configured to connect to a
setting tool and the connecting mechanism is attached with a shear
member to the mandrel, a sealing element located around the mandrel
and configured to be pushed toward an internal wall of the casing,
an upper wedge configured to push the sealing element against the
casing, and a slip ring configured to push the sealing element over
the upper wedge and also to engage the inner wall of the casing
with buttons for preventing the plug to slide along the casing. The
shear member is manufactured to break before any other part of the
mandrel to release the connecting mechanism, and there is no lower
wedge to push against the sealing element.
[0013] According to another embodiment, there is a top set plug for
sealing against a casing of a well. The plug includes a mandrel
having a throughout bore that extends from a top end to a bottom
end, a connecting mechanism that is configured to connect to a
setting tool, wherein the connecting mechanism is attached through
a shear member to the mandrel, a sealing element partially located
around the mandrel and having a top end and a bottom end, wherein
the top end is configured to be pushed toward an internal wall of
the casing and acts as a seal while the bottom end is configured as
a ramp, and a slip ring configured to engage the inner wall of the
casing with buttons for preventing the plug to slide along the
casing. The bottom end of the sealing element enters into a bore of
the slip ring and pushes the slip ring radially outward toward the
inner wall of the casing. The shear member is manufactured to break
before any other part of the mandrel to release the connecting
mechanism.
[0014] According to yet another embodiment, there is a method for
plugging a casing in a well. The method includes a step of
attaching a setting tool to a frac plug, wherein a ball is placed
inside the setting tool; a step of lowering the setting tool, the
ball and the frac plug to a desired depth into the casing of the
well; a step of activating the setting tool to set up the frac
plug, wherein a connection between the setting tool and the frac
plug is located at a top end of the frac plug; a step of removing
the setting tool after the connection between the setting tool and
the frac plug is broken; and a step of pressuring the ball to seat
onto a seat formed into a mandrel of the frac plug.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Fora more complete understanding of the present invention,
reference is now made to the following descriptions taken in
conjunction with the accompanying drawings, in which:
[0016] FIG. 1 is a schematic diagram of a well in which a setting
tool and a plug have been deployed;
[0017] FIG. 2 is a schematic diagram of a frac plug;
[0018] FIG. 3 illustrates a setting tool that sets up a frac plug
at the bottom of the plug;
[0019] FIG. 4 illustrates a top set frac plug;
[0020] FIG. 5 illustrates the top set frac plug having a ball
seated deep inside an internal mandrel for providing structural
reinforcement;
[0021] FIG. 6 illustrates an activation of the setting tool for
setting the top set plug;
[0022] FIG. 7 illustrates a ball from another top set plug
interacting with a current top set plug;
[0023] FIG. 8 illustrates a pattern of a slip ring of the top set
plug;
[0024] FIG. 9 illustrates a cross-section of the slip ring of the
top set plug;
[0025] FIG. 10 illustrates another top set plug that has a sealing
element as the top most element;
[0026] FIG. 11 illustrates the another top set plug after the
setting tool has been removed and a ball is seated inside the plug;
and
[0027] FIG. 12 is flowchart of a method for setting up the top set
plug in a casing of a well.
DETAILED DESCRIPTION OF THE INVENTION
[0028] 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 frac plug. However, the embodiments to be discussed next are not
limited to a frac plug, but they may be applied to other types of
plugs or other devices that need to be set up in a narrow
conduit.
[0029] 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.
[0030] According to an embodiment, a novel frac plug is configured
to have less parts and to be set up at the top part and not at the
bottom part as the traditional plugs. In one embodiment, one or
more parts, even all the parts, of the frac plug are made of a
dissolvable material so that there is no need for milling the plug
after the frac operation of a given stage is over. In one
embodiment, the novel frac plug can be used in a ball in place
mode, due to the top set up operation. In yet another embodiment,
the slip part of the frac plug is configured in a zig-zag pattern
to maximize a gripping with the casing. The zig-zag pattern also
prevents the fingers of the slip part to break apart when in the
well. The above noted features may be combined in any desired way
for a given frac plug, depending on its application.
[0031] According to an embodiment illustrated in FIG. 4, a top set
plug 410 is configured to be set up at a top part. The terms "top"
and "bottom" are defined in this application with regard to a
placement of the plug in a vertical or horizontal well, where the
top points toward the head of the well and the bottom points toward
the toe of the well. Thus, a top part of the frac plug is well
defined as being the part that contacts the setting tool, while the
bottom part of plug is the part that is facing toward the toe of
the well and opposite from the setting tool.
[0032] The top set plug 410 is shown in FIG. 4 as being part of a
system 400 that also includes a setting tool 470 that is connected
to the top set plug 410. The top set plug 410 is placed inside a
casing 102 and has a mandrel 412 that is configured with a
connecting mechanism 414, at its top end 412A, so that the
connecting mechanism 414 is configured to contact and connect to an
inner sleeve 472 of the setting tool 470. In one embodiment, the
connecting mechanism 414 is a thread and the inner sleeve 472 has a
mating thread 474. However, in another embodiment, the connecting
mechanism is a breakable pin. Other implementations of the
connecting mechanism may be used by those skilled in the art.
Irrespective of the implementation of the connecting mechanism, it
ensures that the plug 410 is fixedly attached to the setting tool
while the plug is lowered to the desired location inside the
casing.
[0033] The connecting mechanism 414 is attached to the mandrel 412
through a shear member 416. The shear member 416 is attached to a
flared-up portion 417 of the mandrel 412. FIG. 4 shows the
flared-up portion 417 of the mandrel having a larger internal
diameter D1 than a diameter D2 of the remaining portion of the
mandrel. The flared-up portion 417 is configured in this way to
press against an upper wedge 422, and to push the upper wedge 422
toward the inner wall of the casing 102, as discussed later. The
shear member 416 may be made from the same material as the mandrel
412 and the connecting mechanism 414. However, in one application,
these elements may be made of different materials and as separated
parts. In this embodiment, these three elements are made integrally
as part of the mandrel. When the time comes to separate the setting
tool 470 from the plug 410, the inner sleeve 472 is pulled apart
from the plug 410 until the shear member 416 breaks and releases
the setting tool. Note that the only part that keeps the plug 410
attached to the setting tool 470 is the connecting mechanism 414.
Once the shear member 416 breaks, the plug is freed from the
setting tool. For this reason, the shear member 416 is made to
break when a desired force is applied to it. While the shear member
416 is shown in FIG. 4 as being implemented as a thin part of the
mandrel 412, those skilled in the art would understand that the
shear member may be implemented in different configurations, e.g.,
made of a material that is weaker than the material of the mandrel
and the connecting member 414. The shear member 416 is shaped
and/or made of a material so that is breaks before any other part
of the mandrel.
[0034] The bottom end 412B of the mandrel 412 is configured to
engage with a guide member 418, for example, through threads 420.
Other mechanisms may be used for attaching the guide member 418 to
the mandrel 412. The guide member 418 may have an external diameter
D that is slightly (e.g., about 10 to 30%) smaller than an interior
diameter of the casing 102, so that the guide member guides the
plug inside the casing while being lowered to its desired
location.
[0035] Between the guide member 418 and the connecting mechanism
414, the following elements are distributed along the mandrel 412.
Starting from the connecting mechanism 414, the upper wedge 422 (or
tapered cone or ramp or wedge-shaped body) is distributed around
the mandrel and is configured to push radially out on a sealing
ring element 424. The ramp part 422A of the upper wedge 422
contacts directly the underside of the sealing ring element 424 and
pushes the sealing ring element toward the casing 102 when the
upper wedge 422 is pushed by the external sleeve 480 of the setting
tool 470. The upper wedge 422 may include one or more seals 423,
that are placed between the upper wedge body and the mandrel 412,
to prevent a well fluid to move past the upper wedge. The sealing
ring element 424 also can include one or more seals 425A and 425B,
located between the sealing element and the casing and/or the upper
wedge 422 to further prevent the escape of the well fluid past the
plug 410. Note that all these elements of the plug 410 are shown in
FIG. 4 as being separated from each other by a considerable
distance when in fact, this distance is infinitesimal or
non-existent, i.e., these elements are tightly packed together. The
large distance between these elements is used in this figure to
more clearly illustrate each element and the relationships between
these elements.
[0036] The plug 410 also includes a slip ring 426 disposed around
the mandrel 412. In one embodiment, the plug includes only one slip
ring. The slip ring 426 includes one or more buttons 428, which are
made from a hard material, and are configured to directly engage
with the casing 102 when the frac plug is set. The direct contact
between the buttons 428 and the casing 102 ensures that the plug
does not move along a longitudinal axis X of the well when the plug
is exposed to an upstream pressure.
[0037] A bore 413 of the mandrel 412 is configured to have one or
two seats. A seat is defined herein as being a portion of the
mandrel, in the bore, that is shaped to receive and mate a ball
440. For example, the mandrel 412 may be shaped to have a large
seat 430 or a smaller seat 432. In one embodiment, the mandrel 412
may be shaped to have both seats. The large seat 430 is a side
seat, i.e., it is formed at the side of the mandrel 412. However,
the smaller seat 432 is an internal seat, i.e., it is formed in a
region of the bore that is not at the side of the frac. An
advantage of having an internal seat is that when the ball 440 is
seated against such deep seat 432, as shown in FIG. 5, the ball 440
exerts a force 510 (only one force is shown although the ball
exerts the same force all around the mandrel 412) on the mandrel
412, which structurally supports the entire plug 410 from being
compressed along the radial direction by the pressure exerted by
the pumped fluid in the well. In other words, because the ball 440
is seated deep into the plug 410, as shown in FIG. 5, the deep-set
ball imparts additional structural integrity to the plug in that it
resists an inward radial movement of the slips and wedge, which
would otherwise loosen the plug's grip on the casing. It is noted
that if one or more elements of the plug move radially inward
toward the central point of the bore 413, a seal between the
sealing ring element 424 and the casing 102 may be weakened, which
may result in the collapse of the plug and the well fluid rushing
past the plug.
[0038] The inventors have found that by having the plug 410
configured to allow the ball 440 to enter deep inside the mandrel
412, i.e., at least past the ends of the mandrel, for example,
close to a middle point of the mandrel, as shown in FIG. 5, it
achieves this structural advantage. In one embodiment, the ball 440
is considered to enter deep inside the mandrel 412 when the ball is
at the same position, along the longitudinal axis X, as the sealing
ring element 424, or as the slip ring 426. Note that FIG. 5 shows
the frac plug 410 being set, i.e., the shear element 416 has been
broken, so that the setting tool 470 has been freed and removed
(although spaces between the elements of the plug and also spaces
between the plug and the casing are still shown).
[0039] Returning to FIG. 4, the setting tool 470 is configured to
carry the ball 440 while also being attached to the plug 410, i.e.,
to be able to perform the ball in place mode. For this mode, the
ball 440 is placed inside the inner sleeve 472 of the setting tool.
To prevent the ball 440 from moving unintentionally while the
setting tool is moved in the well to the desired position where the
plug needs to be set up, the outer mandrel 480 includes a retention
element 482, for example a pin, that prevents the ball from moving
upstream. To prevent the ball to move in a downstream direction,
the inner sleeve 472 includes a retaining mechanism 476, for
example, a spring. The ball 440 is placed between the retention
element 482 and the retaining mechanism 476 while the setting tool
is lowered into the casing. As the setting tool and the ball move
downstream in the casing, the fluid well needs a passage to bypass
this tandem. For this reason, one or more slots 484 may be made
into the external sleeve 480. In this way, the fluid well 490 is
able to pass through the setting tool 470 and through the bore 413
of the plug 410, as indicated by path 492.
[0040] The retention element 482, which is fixedly attached to the
external sleeve 480, is allowed to move relative to the inner
mandrel 472, to push the ball 440 past the retaining mechanism 476,
due to a slot 473 formed into the wall of the inner mandrel 472. In
this way, when the plug 410 needs to be set, and the setting tool
470 is activated so that the internal sleeve 472 moves upstream
while the outer sleeve 480 remains stationary (or the other way
around), the retention element 482 effectively moves downstream
relative to the inner sleeve 472, and pushes the ball 440 over the
retaining mechanism 476. Once the ball 440 has moved past the
retention mechanism 476, due to the well pressure exerted by the
pumps at the well head, the ball 440 moves until is seated in the
large seat 430, or the deep seat 432, depending on its size. Note
that if the ball 440 is sized to seat the large seat 430, it cannot
move past this seat to reach the deep seat 432.
[0041] FIG. 6 illustrates the situation in which the setting tool
470 has been activated, the external sleeve 480 is preventing the
upper wedge 422 from moving along the axial direction X, the inner
sleeve 472 has moved in an upward direction relative to the
external sleeve 480, opposite to the longitudinal direction X, thus
pulling the mandrel 412 along the same direction. As a consequence
of the movement of the mandrel 412 while the upper wedge 422 is
stationary, the guiding element 418 has moved toward the upper
wedge 422, pressing the slip ring 426 and the sealing ring element
424 up the ramp of the wedge element 422, so that the sealing ring
element 424 is pressing against the casing 102, effectively sealing
the casing's bore.
[0042] In addition, the retaining mechanism 476 has also moved
toward the retention element 482, thus forcing the ball 440 to move
past the retaining mechanism 476, as shown in the figure. The ball
440 is now freed and when the fluid 490 is pressurized from the
surface and moves along direction 492, it moves the ball 440 into
the large seat 430 or the deep seat 432, depending on the size of
the ball. Note that FIG. 6 shows the setting tool 470 being
activated but not yet freed from the mandrel 412.
[0043] FIG. 7 shows the ball 440 being seated in the deep seat 432
and the setting tool 470 freed from the plug 410 as the inner
mandrel has exerted the force on the plug 410 and the shear member
416 broke. Also note that the mandrel 412 has been moved together
with the guiding element 418 relative to the other members of the
plug 410, so that the upper wedge 422 is now removed from the large
seat 430. The upper wedges 422 was either in direct contact with
the large seat 430 in FIG. 4, or very close to it.
[0044] FIG. 7 shows that one or more slots 434 may be formed in the
bottom end 412B of the mandrel 412 so that when a ball 440' from a
previous frac plug is contacting the bottom end 412B, the fluid
inside the well still can pass from the toe of the well toward the
head (e.g., during a backflow operation) of the well, past this
ball and the frac plug. FIG. 7 further shows how the ball 440
seated in the deep seat 432 provides structural support to the
upper wedge 422 and the slip ring 426, to prevent these elements
from moving radially inward, toward the bore 413 of the mandrel
412. In one embodiment, the deep seat 432 is formed in the mandrel
so that the deep seat is directly opposite to the slip ring 426
relative to the mandrel. In another embodiment, the deep seat is
manufactured to be located directly across the upper wedge 422. In
still another embodiment, the deep seat is manufactured to be
located across the sealing element 424. One skilled in the art
would understand from this disclosure that the deep seat 432 can be
formed anywhere internal to the mandrel to be across any of the
elements to support them. When a large pressure is applied to the
well fluid, the mandrel 412 can slide relative to the sealing
element 424 and the upper wedge 422, as illustrated in FIG. 5, due
to the force imparted by the ball 440. Due to the flared-up part
417 of the mandrel, it can add additional support to the upper
wedge 422.
[0045] In one embodiment, to enhance the adherence of the slip ring
426 to the casing 102, the slip ring 426 is configured to have a
ring 810 and alternating slots 812, which partially extend radially
around the ring 810 to form a zig-zag pattern, as illustrated in
FIG. 8. Note that the buttons 428 may be configured to have a
surface inclination relative to the casing, such that a better grip
between the buttons and the casing is obtained. This zig-zag
patterned slip(s) then maximizes the surface area gripping the
casing wall, thereby increasing the axial hold force. In other
embodiments, the slips may be made of several fingers formed from
slots all extending from one end of the ring. An advantage of the
alternating slots 812, or zig-zag patterned slips, is that upon
setting, the slip ring 426 will have a tendency to remain intact as
compared to the individual fingers. If a finger or section of the
slip ring separates, it may dislodge from the others, thereby
weakening the plug's adherence to the casing. The buttons 428 of
the slip ring 426 "bite" into the casing 102 and increase the axial
holding force of the plug. In this context, the "axial hold force"
refers to the resistance to axial movement along the longitudinal
axis X of the wellbore casing 102. Typically, the force is
expressed in terms of the wellbore pressure (in pounds per square
inch (psi)) times the sealed inner area of the casing required to
overcome the plugs adherence to the casing inner wall and move the
plug axially.
[0046] A sectional view of the slip ring 426 is shown in FIG. 9,
together with two cross-sections AA and BB from FIG. 8. FIG. 9
shows the ring 810 and the fingers 814 that are connected to the
ring 810. The slots 812 between the fingers 814 are shown being
positioned in a first configuration, toward the bottom end 412B,
then those at the top end 412A. FIG. 9 shows that the slots at the
two ends are offset with a given angular displacement, for example,
90 degrees.
[0047] In one embodiment, the plug 410 components may be
manufactured as machined or molded composites, or as dissolvable
materials or a combination of the two. In one application, all the
parts of the plug 410 are made of dissolvable materials. This means
that after the frac operation for a given stage is completed,
instead of using a drill to mill the plug, the well fluid or a
special fluid is pumped into the well, which after interacting for
a given amount of time with the plug, dissolves the components of
the plug. This is very advantageous because lowering in the well
the drilling equipment is time consuming and thus, expensive.
[0048] When the traditional plug of FIG. 2 is compared to the novel
plug 410 of FIG. 4, one can observe that the plug 410 has less
components. For example, the plug 410 does not have the upper slip
ring 204 and the upper wedge 206. In one embodiment, the plug 410
also does not have the bottom push ring 216. Because of these
features, a volume of the plug 410 may be reduced to less than 80
in.sup.3, from a volume of 250 in.sup.3, which customary for an
existing frac plug. Further, the reduced volume of the plug 410
ensures, in one application, that the well fluid that passes
through it is increased, which prevents large pressure
differentials across the plug.
[0049] In another embodiment, as illustrated in FIG. 10, a frac
plug has even less components than the plug 410 discussed above. A
frac plug relies on the structural integrity of its components to
withstand the stresses applied during its use in the well. The
available plugs do not use the ball or a restrictive plugging
element to aid in the support of the plug during the frac
operation. As such, the available plugs use force supportive
members (ramps or wedges) that may or may not be backed up by inner
mandrels to preserve the overall structural integrity. However,
such mandrels have an overall inner diameter just less than about
2.0''. This design often results in plugs longer than 18'' with a
total volume exceeding 250 in.sup.3 (in a typical 5.5'' casing
application).
[0050] This configuration restricts the amount of well fluid that
can be transmitted through the plug when advancing through the
well. Thus, this existing configuration may create large pressure
differentials across the plug.
[0051] Furthermore, the available plugs use opposing taper angles
or ramps of wedges 206 and 210, as illustrated in FIG. 2, to draw
either a sealing area 208 or a gripping area 212 of the plug into
its final set position, against the wall of the casing. The
opposing ramps design also requires excess plug length as the full
travel of the ramps needs to be included in both the swaging
element and the element to be expanded (the seal).
[0052] The novel plug 1010 shown in FIG. 10 overcomes these
problems by placing the sealing element 1024 at the top end of the
plug. This means that there is no wedge or ring or other element
upstream of the sealing element 1024 for pushing onto the sealing
element, as is the case for the existing frac plugs. In addition,
this plug is configured, similar to the plug 410, to be a top set
plug. The sealing element 1024 is configured to have two functions:
the top end part 1024A acts as the sealing member while the bottom
end part 10246 is shaped and acts as a ramp for driving the slip
ring 1026 toward the casing 102. In other words, the bottom end
part 1024B of the sealing element 1024 acts as the upper wedge 422.
The slip ring 1026 may have buttons 1028, similar to the slip ring
element 426.
[0053] An inner mandrel 1012 allows for load transfer between the
setting tool 1070, which is attached at the top end 1012A of the
mandrel, and the guiding element 1018, which is located at the
bottom end 1012B of the mandrel. In this embodiment, the guiding
element 1018 is attached to the mandrel 1012 by a shoulder 1019,
which is configured to fit in a corresponding groove 1015 formed in
the outer wall of the mandrel 1012. In another embodiment, the
guiding element 1018 may be attached with threads, as the guiding
element 418 in FIG. 4. Those skilled in the art, having the benefit
of this disclosure, might chose various other implementations for
this element. The setting tool 1070 is configured, similar to that
of FIG. 4, to connect to the upper part of the mandrel 1012, for
example, through a connecting mechanism 1014 that connects to the
inner sleeve 1072. In this figure, the connecting mechanism 1014 is
implemented as threads. However, the connecting mechanism may be
implemented as a breakable pin, etc. A shear member 1016 is present
on the mandrel 1012 to allow the top part to break away after the
setting tool has set up the plug. FIG. 10 further shows the outer
sleeve 1080 of the setting tool being in direct contact with the
sealing member 1024.
[0054] The frac plug 1010 further includes a single piece slip
1026, which includes a base ring 1027 with slips 1029 machined such
that they are attached solely at the base of each geometric slip
section. Included on the outward surface of the slip 1026 is a
hardened insert or button 1028. This hardened material may be
comprised of ceramic, carbide, cast iron, etc. A transitionary seal
1023 may be located between the mandrel 1012 and the sealing
element 1024. The transitionary seal allows the plug to actuate
through its full range of motion while maintaining the pressure
differential integrity. This feature is not required in that when
the tool is in its fully set state and has been stroked down due to
wellbore isolation pressures, a metal to metal seal may be achieved
between the mandrel 1012 and the main swage body.
[0055] One or more grooves 1025 may be formed in the sealing
element 1024, facing the casing 102, and they are aiding in
obtaining a positive metal to metal seal between the frac plug
outer diameter and the inner diameter of the cased wellbore. These
grooves can be either ran as shown or with the addition of an
elastomeric sealing element nested inside each groove.
[0056] The frac plug 1010 and the setting tool 1070, configured as
discussed in this embodiment, can carry a ball 1040 while being
deployed from the surface, thus being capable of achieving a ball
in place mode. After the setting tool 1070 is activated and removed
from the plug, the ball 1040 enters inside the plug 1010, and seats
on the deep seat 1032, as shown in FIG. 11, thus sealing or
blocking a bore 1013 of the mandrel 1012. The deep seat 1032 is
located under the sealing element 1024, so that the force F that is
applied by the well fluid 1090 onto the ball 1040 is partially
spread radially outward on the inner wall of the sealing element
1024, to enhance the integrity of the seal and to further press the
sealing element against the inner wall of the casing 102. In one
embodiment, the deep seat is configured to be across the slip ring
1026. While FIG. 11 shows that the ball 1040 interacting only with
the deep seat 1032, formed in the mandrel 1012, in one embodiment
it is possible to configure the plug 1010 so that the ball 1040
also directly contacts the sealing element 1024.
[0057] A method for plugging a casing in a well for a frac
operation is now discussed with regard to FIG. 12. The method
includes a step 1200 of attaching a setting tool to a frac plug,
wherein a ball is placed inside the setting tool, a step 1202 of
lowering the setting tool, the ball and the frac plug to a desired
depth into the casing of the well, a step 1204 of activating the
setting tool to set up the frac plug, wherein a connection between
the setting tool and the frac plug is located at a top side of the
frac plug, a step 1206 of removing the setting tool after the top
connection between the setting tool and the frac plug is broken,
and a step 1208 of pressuring the ball to seat into a deep seat
inside a mandrel of the frac plug, away from a top end and a bottom
end of the mandrel, to provide structural support to the frac plug.
In one application, the frac plug has a single wedge, for example,
the upper wedge and not a lower wedge. In another application, the
frac plug 410 has only the elements shown in FIG. 4 and the frac
plug 1010 has only the elements shown in FIG. 10, i.e., much less
elements than the existing plug 200.
[0058] The disclosed embodiments provide a top set plug for use in
a well for isolating one stage from another. The top set plug is
configured to have less parts than an available plug. It should be
understood that this description is not intended to limit the
invention. On the contrary, the 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 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.
[0059] Although the features and elements of the present
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.
[0060] 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.
* * * * *