U.S. patent application number 16/480043 was filed with the patent office on 2020-05-14 for well plugging apparatus and temporary well plugging method.
The applicant listed for this patent is Kureha Corporation. Invention is credited to Takuma KOBAYASHI, Hiroaki YOSHIDA.
Application Number | 20200149368 16/480043 |
Document ID | / |
Family ID | 63919219 |
Filed Date | 2020-05-14 |
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United States Patent
Application |
20200149368 |
Kind Code |
A1 |
YOSHIDA; Hiroaki ; et
al. |
May 14, 2020 |
WELL PLUGGING APPARATUS AND TEMPORARY WELL PLUGGING METHOD
Abstract
An object of the present invention is to provide a well plugging
apparatus configured to reduce an expense and shorten a process for
well drilling and a temporal plugging method of a well using the
well plugging apparatus. The well plugging apparatus according to
the present invention is a well plugging apparatus that includes a
downhole plug, a setting tool (2) to operate and install the
downhole plug, and an obstacle that plugs a flow path in the
downhole plug. Since the setting tool (2) internally includes the
obstacle, after the downhole plug is installed inside the well, and
the setting tool (2) is removed, the flow path in the downhole plug
can be reliably plugged in a short time. Additionally, the use of
the well plugging apparatus of the present invention allows
temporarily plugging the well reliably in a short time.
Inventors: |
YOSHIDA; Hiroaki; (Tokyo,
JP) ; KOBAYASHI; Takuma; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kureha Corporation |
Tokyo |
|
JP |
|
|
Family ID: |
63919219 |
Appl. No.: |
16/480043 |
Filed: |
April 17, 2018 |
PCT Filed: |
April 17, 2018 |
PCT NO: |
PCT/JP2018/015857 |
371 Date: |
July 23, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 33/1293 20130101;
E21B 33/128 20130101; E21B 33/134 20130101; E21B 23/06
20130101 |
International
Class: |
E21B 33/128 20060101
E21B033/128; E21B 23/06 20060101 E21B023/06 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 28, 2017 |
JP |
2017-090649 |
Claims
1. A well plugging apparatus for plugging a well comprising: a
downhole plug; a setting tool disposed on a rear end side of the
downhole plug, the setting tool operating and installing the
downhole plug; and one or more obstacles that plug a flow path in
the downhole plug, wherein the downhole plug includes a hollow
mandrel that opens at least in a rear end, the setting tool
includes a setting rod and a setting sleeve, the setting rod is
directly or indirectly connected to a front end side of the
mandrel, and the setting sleeve is disposed to cover at least a
part of the setting rod and at least a part of the downhole plug,
the setting rod is inserted from the opening in the rear end of the
mandrel into the hollow portion of the mandrel, and the obstacle is
internally included in a space inside the setting tool.
2. The well plugging apparatus according to claim 1, wherein the
mandrel contains a resin as a main component.
3. The well plugging apparatus according to claim 1, wherein the
mandrel contains a degradable metal as a main component.
4. The well plugging apparatus according to claim 1, wherein the
mandrel contains a degradable resin as a main component.
5. The well plugging apparatus according to claim 1, wherein the
downhole plug includes a seat that receives the obstacle.
6. The well plugging apparatus according to claim 1, wherein the
obstacle is a ball, a dart, or a disk.
7. The well plugging apparatus according to claim 1, wherein the
obstacle at least partially contains a degradable material.
8. The well plugging apparatus according to claim 7, wherein the
degradable material is a degradable resin or a degradable
metal.
9. The well plugging apparatus according to claim 1, wherein the
mandrel has a rear end having a notch structure configured to
internally include the obstacle in a space inside the setting
tool.
10. The well plugging apparatus according to claim 1, wherein at
least one of the setting rod or the setting sleeve has a groove or
a notch structure with respect to an axial direction configured to
internally include the obstacle in a space inside the setting
tool.
11. The well plugging apparatus according to claim 10, wherein at
least one of the setting rod or the setting sleeve has the
sector-shaped notch structure with respect to the axial direction
configured to internally include the obstacle in the space inside
the setting tool.
12. The well plugging apparatus according to claim 10, wherein the
setting rod has the groove or the notch structure with respect to
the axial direction.
13. The well plugging apparatus according to claim 10, wherein the
setting sleeve has a groove in an inner surface.
14. (canceled)
15. A well plugging apparatus for plugging a well comprising: a
downhole plug; a setting tool disposed on a rear end side of the
downhole plug, the setting tool operating and installing the
downhole plug; and one or more obstacles that plug a flow path in
the downhole plug, wherein the downhole plug includes a hollow
portion that opens at least in a rear end, the setting tool
includes a setting rod and a setting sleeve, the setting rod is
directly or indirectly connected to the downhole plug, and the
setting sleeve has a tubular shape surrounding one end of a long
shaft of the setting rod, the setting rod is inserted from the
opening in the rear end of the downhole plug into the hollow
portion of the downhole plug, and the obstacle is internally
included in a space formed by an inner wall of the setting sleeve,
the setting rod, and the downhole plug.
16. The well plugging apparatus according to claim 15, wherein the
downhole plug includes a seat that receives the obstacle.
17. A method for temporarily plugging a well using a well plugging
apparatus, wherein the well plugging apparatus includes: a downhole
plug; a setting tool disposed on a rear end side of the downhole
plug, the setting tool operating and installing the downhole plug;
and one or more obstacles plugging a flow path in the downhole
plug, wherein the downhole plug includes a hollow portion at least
opening in a rear end, the setting tool includes a setting rod and
a setting sleeve, the setting rod is directly or indirectly
connected to the downhole plug, and the setting sleeve has a
tubular shape surrounding one end of a long shaft of the setting
rod, the setting rod is inserted from the opening in the rear end
of the downhole plug into the hollow portion of the downhole plug,
and the obstacle is internally included in a space formed by an
inner wall of the setting sleeve, the setting rod, and the downhole
plug, wherein the method comprises steps a) to c): a) moving the
well plugging apparatus to any position in the well and operating
and installing the downhole plug; b) disconnecting the setting tool
and the downhole plug to pull out the setting rod; and c) moving
the obstacle in the setting tool to plug the flow path in the
hollow portion of the downhole plug.
Description
TECHNICAL FIELD
[0001] The present invention relates to a well plugging apparatus
used in enhanced oil recovery of a well to produce hydrocarbon
resources such as petroleum or natural gas and a method for
temporary well plugging using the same.
BACKGROUND ART
[0002] A "fracturing method" or a "hydraulic fracturing" is one of
enhanced oil recoveries of hydrocarbon resources and is a method to
generate fractures in a production reservoir (reservoir that
produces hydrocarbon resources, such as petroleum such as shale oil
or natural gas such as shale gas) in deep subterranean by hydraulic
pressure from fracturing fluid. Using this method, a predetermined
section of a wellbore (downhole) drilled in a subterranean
formation several thousand meters underground is partially plugged
sequentially from a distal end portion of the wellbore, and the
fracturing fluid is delivered into the plugged section at high
pressure, thus performing the fracturing, which generates fractures
in the production reservoir. Then, the next predetermined section
(typically ahead of the preceding section, i.e., a section closer
to the ground surface) is plugged, and the fracturing is performed.
After that, this process is repeated until the required isolation
and fracturing are completed.
[0003] Various methods have been known as methods for plugging the
wellbore sequentially from the distal end portion of the wellbore.
An example of the method includes a method using a downhole tool
referred to as downhole plug (sometimes also referred to as "frac
plug," "bridge plug," "packer," or the like). For example, Patent
Documents 1 to 4 disclose downhole plugs configured to plug and fix
wellbores as the downhole plugs.
[0004] Patent Document 1 discloses a downhole plug for well
drilling (sometimes also simply called "plug" hereinafter), and
specifically discloses the plug including a mandrel (main body)
having a hollow portion in an axial direction, a ring or annular
member along an axial direction on an outer peripheral surface
orthogonal to the axial direction of the mandrel, a first conical
member and a slip, a malleable element formed from elastomer,
rubber, or the like, a second conical member and a slip, and an
anti-rotation feature. Isolation of the wellbore by a downhole plug
for well drilling is performed as follows.
[0005] In other words, moving the mandrel in the axial direction
decreases a gap between the ring or the annular member and the
anti-rotation feature. In association with this, the slip abuts on
an inclined surface of the conical member and advances along the
conical member, radially expands outward, abuts on an inner wall of
a wellbore, and is fixed to the wellbore. Furthermore, the
malleable element expands in diameter and deforms, abuts on the
inner wall of the wellbore, and seals the wellbore, thus sealing
the wellbore. The mandrel has the hollow portion in the axial
direction, and the wellbore can be sealed by setting a ball or the
like therein.
[0006] Metal materials (aluminum, steel, stainless steel, and the
like), fibers, wood, composite materials, plastics, and the like
are widely exemplified as materials that form plugs, and it is
described that composite materials containing a reinforcing
material such as carbon fibers, especially composite materials
containing polymer such as epoxy resin or phenol resin are
preferred, and that the mandrel is formed from aluminum or a
composite material. On the other hand, Patent Document 1 describes
that, in addition to the previously described materials, a material
that degrades depending on temperature, pressure, pH (acidic,
basic), and the like is usable as the ball or the like.
[0007] Patent Document 2 discloses a packer assembly for well
drilling in which each packer is detachably connected to an
adjacent packer.
[0008] Patent Document 3 describes a packer including a mandrel
having a hollow portion in an axial direction, slips, slip wedges,
resilient packer elements, extrusion limiters, and the like along
an axial direction on an outer peripheral surface orthogonal to the
axial direction of the mandrel.
[0009] Patent Document 3 discloses a disposable downhole tool
(meaning a downhole plug or the like) or a member thereof
containing a degradable material that degrades when exposed to the
environment inside a well, and as a biodegradable material,
discloses a degradable polymer such as an aliphatic polyester such
as polylactic acid. Additionally, Patent Document 3 describes a
combination of a tubular body element having an axial-direction
flow bore, a packer element assembly including an upper sealing
element, a center sealing element, and a lower sealing element
along an axial direction on an outer peripheral surface orthogonal
to the axial direction of the tubular body element, and a slip and
a mechanical slip body. Furthermore, Patent Document 3 discloses
that fluid flow in only one direction is allowed due to the fact
that a ball is set in the flow bore of the tubular body
element.
[0010] Patent Document 4 discloses a downhole plug including a flag
plug, a mandrel having a hollow portion present in an axial
direction of the flag plug, and a setting rod passing through the
hollow portion of the mandrel. The setting rod disclosed in Patent
Document 4 is connected to a front end of the downhole plug.
[0011] As the downhole plug, a downhole plug having an opening at
the center and including a seat that receives an obstacle is
generally used. In the use of a ball as the obstacle, to plug a
wellbore using a downhole plug with a ball seat, the downhole plug
is installed at a predetermined position using a setting tool and
the downhole plug is operated. Thereafter, the obstacle is supplied
and disposed on the seat of the downhole plug and an opening of the
seat is plugged, thus completing the plugging of the wellbore (for
example, Patent Document 5).
[0012] However, in the use of, for example, the ball as the
obstacle, to supply and dispose the ball having a predetermined
size from the ground to the ball seat of the downhole plug
installed underground at a depth from 1000 to 5000 m, the ball
needs to be transported taking a certain amount of time by
high-pressure water flow. At this time, the use of the
high-pressure water flow deforms the ball due to, for example, a
collusion with a reservoir formation during transportation or
generates breakage such as cracking or chipping, possibly
deteriorating a seal performance.
[0013] In contrast, Patent Document 6 discloses a mandrel present
in an axial direction of a frac plug and a tubular metallic sleeve
installed inside the mandrel and describes a downhole plug
including a ball in this metallic sleeve.
[0014] While downhole plugs are sequentially disposed in a well
until welling is completed, the downhole plugs need to be removed
at a stage where recovery of hydrocarbon resources starts. Because
the plug is typically not designed so as to release the plugging to
be retrievable after use, the plug is removed by destruction or by
making it into small fragments by any method including fracturing
or perforation, but substantial cost and time are required for
fracturing, perforation, and the like. There are also plugs
specially designed to be retrievable after use (retrievable plugs),
but since plugs are placed in deep subterranean, substantial cost
and time are required to recover all of them.
[0015] Furthermore, under circumstances where excavation conditions
such as high depth are becoming demanding and diverse more and
more, it has been requested to provide a well plugging apparatus
and a method for temporary well plugging that allow reliably
causing an obstacle to be seated on a seat of a downhole plug in a
short time to ensure cost reduction and shorting of a process for
well drilling.
CITATION LIST
Patent Document
[0016] Patent Document 1: US 2011/0,277,989 A specification [0017]
Patent Document 2: US 2003/0,183,391 A specification [0018] Patent
Document 3: US 2005/0,205,266 A specification [0019] Patent
Document 4: US 2011/0,277,987 A specification [0020] Patent
Document 5: US 2015/0,252,643 A specification [0021] Patent
Document 6: US 2002/0,189,822 A specification
SUMMARY OF INVENTION
Technical Problem
[0022] Under circumstances where excavation conditions such as high
depth are becoming demanding and diverse more and more, an object
of the present invention is to provide a well plugging apparatus
configured to reliably supply an obstacle that plugs a flow path in
a downhole plug in a short time and a temporary plugging method of
a well using the well plugging apparatus.
Solution to Problem
[0023] As a result of diligent research to solve the problems, the
inventors of the present invention have found the following. By
including an obstacle to plug a flow path in a downhole plug in a
setting tool used for installation of the downhole plug, the
obstacle is provided to the downhole plug in a short time without
introducing the obstacle from the ground and with damage reduced.
This allows solving the problems, thus completing the present
invention.
[0024] That is, the present invention provides a well plugging
apparatus for plugging a well that includes a downhole plug, a
setting tool, and one or more obstacles. The setting tool is
disposed on a rear end side of the downhole plug. The setting tool
operates and installs the downhole plug. The one or more obstacles
plug a flow path in the downhole plug. The downhole plug includes a
hollow mandrel that opens at least to a rear end. The setting tool
includes a setting rod and a setting sleeve. The setting rod is
directly or indirectly connected to a front end side of the
mandrel. The setting sleeve is disposed to cover all or a part of
the setting rod and at least a part of the downhole plug. The
setting rod is inserted from the opening in the rear end of the
mandrel into the hollow portion of the mandrel. The obstacle is
internally included in a space inside the setting tool.
[0025] Note that the setting tool itself or a part of the setting
tool of the present invention may be referred to as an adapter kit,
and the adapter kit includes a setting rod and a setting
sleeve.
[0026] Here, "front end" and "rear end" in this specification refer
to ends forward and rearward in an orientation in which the
downhole plug advances from an inlet of the well into the well.
Additionally, "front end side" and "rear end side" refer to front
and rear with respect to a midpoint of a length in a longitudinal
axial direction.
[0027] There is provided a method for temporarily plugging a well
using a well plugging apparatus including a downhole plug, a
setting tool, and one or more obstacles. The setting tool is
disposed on a rear end side of the downhole plug. The setting tool
operates and installs the downhole plug. The one or more obstacles
plug a flow path in the downhole plug. The downhole plug includes a
hollow mandrel at least opening in a rear end. The setting tool
includes a setting rod directly or indirectly connected to a front
end side of the mandrel and a setting sleeve having a shape to
cover a part or all of the setting rod and at least a part of the
downhole plug. The setting tool is inserted from the opening in the
rear end of the mandrel into the hollow portion of the mandrel. The
obstacle is internally included in a space inside the setting tool.
The method includes the following steps a) to d): a) moving the
well plugging apparatus to any position in the well and operating
and installing the downhole plug; b) disconnecting the setting tool
and the downhole plug to pull out the setting rod; c) moving the
obstacle in the setting tool to plug the flow path in the hollow
portion of the mandrel; and d) after an elapse of a predetermined
period, removing the obstacle to recover the flow path.
Advantageous Effects of Invention
[0028] Under circumstances where excavation conditions such as high
depth are becoming demanding and diverse more and more, the present
invention can provide the well plugging apparatus including the
setting tool and the downhole plug. The well plugging apparatus is
configured to cause the obstacle to plug the flow path in the
downhole plug to be internally included in the setting tool
adjacent to the downhole plug to supply the obstacle to the
downhole plug safely in a short time. Additionally, the method that
temporarily plugs the well using the well plugging apparatus can
also be provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a diagram illustrating a specific example of a
well plugging apparatus of the present invention.
[0030] FIG. 2 is a schematic front cross-sectional diagram
illustrating a specific example of the well plugging apparatus of
the present invention.
[0031] FIG. 3 is a diagram illustrating an appearance of a frac
plug as a specific example of a downhole plug included in the well
plugging apparatus of the present invention.
[0032] FIG. 4A is a schematic front cross-sectional diagram
illustrating the frac plug as a specific example of the downhole
plug included in the well plugging apparatus of the present
invention, and FIG. 4B is a schematic front cross-sectional diagram
illustrating a state where the downhole plug of FIG. 4A is
installed and fixed in a wellbore.
[0033] FIG. 5A is a diagram illustrating a circumferential
cross-section of a setting rod of FIG. 2 partially cut off into a
straight line shape, FIG. 5B is a diagram illustrating a
circumferential cross-section of the setting rod of FIG. 2
partially cut off into a curvilinear shape, and FIG. 5C and FIG.
5C' are diagrams illustrating circumferential cross-sections of the
setting rods of FIG. 2 partially cut off into angular shapes.
[0034] FIG. 6A is a diagram illustrating a circumferential
cross-section of the setting sleeve of FIG. 2 with an inner surface
having a curvilinear groove, and FIG. 6B and FIG. 6C are diagrams
illustrating circumferential cross-sections of the setting sleeves
of FIG. 2 with inner surfaces having angular grooves.
DESCRIPTION OF EMBODIMENTS
[0035] The present invention relates to a well plugging apparatus
including a downhole plug, a setting tool for installing the
downhole plug, and an obstacle to plug a flow path in the downhole
plug and a method for temporarily plugging a well using the same.
The following describes the well plugging apparatus and the
plugging method according to one embodiment of the present
invention.
1. Well Plugging Apparatus
[0036] The following describes the well plugging apparatus
according to the present embodiment with reference to the drawings.
The well plugging apparatus of the present embodiment includes a
downhole plug 1, a setting tool 2, and an obstacle 3 to plug a flow
path in the downhole plug. Note that FIG. 1 is a specific example
of means to solve the problems of the present invention, and the
scope of the present invention is not limited to the well plugging
apparatus with the aspect illustrated in FIG. 1.
(1) Downhole Plug
[0037] The downhole plug, which is referred to as frac plug, bridge
plug, packer, or the like, is a device installed into a wellbore to
plug a part of the well. The downhole plug includes at least one
mandrel and one or more members mounted on an outer peripheral
surface orthogonal to an axial direction of the mandrel. The
following describes the frac plug 1 in the aspect illustrated in
FIG. 1 as one example of the downhole plug. FIG. 3 illustrates an
appearance of the frac plug 1. As illustrated in FIG. 3, the frac
plug 1 includes a mandrel 11 and members mounted on an outer
peripheral surface orthogonal to an axial direction of the mandrel
11.
1) Mandrel
[0038] The mandrel 11 provided with the frac plug 1 is a member
that has an approximately round shape in cross-section and has a
length sufficiently long relative to a diameter of the
cross-section to ensure strength of the frac plug 1. The diameter
of the cross-section of the mandrel 11 is appropriately selected
according to the size of the wellbore. This diameter configured
slightly smaller than an inner diameter of the wellbore allows the
frac plug 1 to move inside the wellbore. Meanwhile, the diameter of
the mandrel 11 and the inner diameter of the wellbore have a
difference in diameter to the extent that the wellbore can be
plugged by expanding a diameter of a diameter-expandable, circular
rubber member 15 described later and the like. While the mandrel 11
has the length, for example, approximately 5 to 20 times of the
diameter of the cross-section, the length is not limited to this.
The diameter of the cross-section of the mandrel 11 is typically in
a range approximately from 5 to 30 cm.
[0039] Although the mandrel 11 may be a solid, from perspectives of
securing the flow path at an early stage of fracturing, reduction
in weight of the mandrel, and the like, the mandrel 11 is
preferably a hollow mandrel at least partially including a hollow
portion along the axial direction. That is, the hollow portion may
be configured so as to penetrate the mandrel 11 along the axial
direction or to not penetrate the mandrel 11 along the axial
direction. In addition, to push the frac plug 1 into the well using
a fluid for transportation, the mandrel 11 preferably has the
hollow portion along the axial direction. When the mandrel 11 has
the hollow portion along the axial direction, the cross-sectional
shape of the mandrel 11 is a circular ring shape formed by two
concentric circles defining the diameter (outer diameter) of the
mandrel 11 and the outer diameter of the hollow portion
(corresponding to the inner diameter of the mandrel 11). A ratio of
the diameters of the two concentric circles, that is, the ratio of
the outer diameter of the hollow portion to the diameter of the
mandrel 11 is preferably at most 0.7. The magnitude of this ratio
has a reciprocal relationship with the magnitude of a ratio of a
thickness of the hollow mandrel 11 to the diameter of the mandrel
11, so determining the upper limit of this ratio can be considered
equivalent to determining a preferable lower limit of the thickness
of the hollow mandrel. When the thickness of the hollow mandrel is
too thin, the strength (in particular, the tensile strength) of the
hollow mandrel may be insufficient when the frac plug 1 is disposed
inside the wellbore or at the time of plugging the wellbore or
fracturing, which may damage the frac plug 1 in extreme cases.
Therefore, the ratio of the outer diameter of the hollow portion to
the diameter of the mandrel 11 is more preferably at most 0.6 and
even more preferably at most 0.5.
[0040] The diameter of the mandrel 11 and the outer diameter of the
hollow portion may be uniform along the axial direction of the
mandrel 11, but may also vary along the axial direction. That is,
by varying the outer diameter of the mandrel 11 along the axial
direction, the outer peripheral surface of the mandrel 11 may
include a bent part such as a convex portion, a step, a flange
portion, a recess portion (groove portion), and further a screw
portion (typically a male screw-thread structure), or meshing
portions of a ratchet mechanism described later. In addition, the
outer diameter of the hollow portion (inner diameter of the mandrel
11) may vary along the axial direction to provide a bent part, such
as a convex portion, a step, a groove portion, and further a screw
portion (a male screw-thread structure or a female screw-thread
structure) in the inner peripheral surface of the mandrel 11.
Further, the bent part can have a tapered portion.
[0041] Additionally, as described below, since the obstacle is
disposed in a space (hereinafter, this space may also be referred
to as "space inside the setting tool") formed by a setting sleeve
inner wall, a setting rod, and a mandrel rear end in the well
plugging apparatus of the present embodiment, the mandrel rear end
may be cut out such that the obstacle can be disposed. The cutout
preferably has a shape approximately identical to the surface shape
of the obstacle.
[0042] The convex portion, step, flange portion, and recessed
portion (groove portion), which can be provided in the outer
peripheral surface or the inner peripheral surface of the mandrel
11, are usable as supporting parts when the frac plug 1 is
transported in the well, or are usable as parts for mounting and
fixation of another member to the outer peripheral surface or the
inner peripheral surface of the mandrel 11. In addition, when the
mandrel 11 has the hollow portion, the part can serve as a seat to
hold the obstacle to plug the flow path. In a case where the hollow
portion of the mandrel 11 is present at least in the rear end, the
mandrel 11 is open. Configuring this opening into a seat having the
shape configured to hold the obstacle allows the obstacle to be
seated more reliably and plugging the flow path more reliably as a
result. Note that, as the seat, in addition to configuring the
opening of the mandrel 11 into the seat shape, a seat member having
an open center part may be attached to the mandrel 11. For example,
in the use of a ball as the obstacle, appropriately selecting the
size of the opening in the seat (ball seat) of the downhole plug
prevents cracking and escape of the ball, thereby ensuring plugging
the flow path more reliably. Furthermore, the ring-shaped ratchet
mechanism orthogonal to the axial direction of the mandrel may be
configured in the outer peripheral surface of the mandrel 11. In
cooperation with an inner peripheral surface of a member mounted on
the outer peripheral surface orthogonal to the axial direction of
the mandrel 11, the ratchet mechanism permits one-way movement of
this member along the axial direction of the mandrel and forms the
plurality of meshing portions restricting a movement in the
opposite direction.
Material Forming Mandrel
[0043] The material forming the mandrel 11 provided in the downhole
plug is not particularly limited. Materials conventionally used as
materials to form a mandrel provided with a downhole plug are
usable. Examples of the material can include a metal material
(aluminum, steel, stainless steel, and the like), fiber, wood, a
composite material, resin, and the like. Specifically, the material
can include a composite material containing a reinforcing material
such as carbon fiber, particularly a composite material containing
polymer such as epoxy resin and phenol resin, and the like. Since
the downhole plug of the present embodiment allows cost reduction
and shortening of the process for well drilling through ease of
removal of the downhole plug and securing the flow path, the
mandrel 11 is preferably made of a degradable material.
Degradable Material
[0044] In the mandrel 11 made of the degradable material in the
downhole plug used for the present embodiment, as the degradable
material, a degradable material having biodegradability or
hydrolyzability, and further a degradable material that can be
chemically degraded by any other method are usable.
[0045] Note that a material physically degraded by applying a large
mechanical force, such as destruction and disintegration, like a
metal material such as aluminum, which is generally used as the
mandrel provided in the downhole plug conventionally, is not
applied as the degradable material forming the mandrel 11 provided
in the downhole plug. However, as seen in a composite material of
degradable resin and a metal material or an inorganic substance, a
material that reduces strength possessed by the original resin due
to reduction in degree of polymerization and the like and
embrittles, and as a result, is easily disintegrated and loses its
shape by an application of an extremely small mechanical force is
classified as the degradable material. Specifically, the degradable
material configured as follows is included. A recess portion such
as a depression having a predetermined shape is provided in a base
material made of a degradable material such as degradable resin
including polyglycolic acid (hereinafter also sometimes referred to
as "PGA"), metal (such as a metal piece) or an inorganic substance
having a shape matching with the shape of this recess portion is
fitted, and these members are fixed with an adhesive.
Alternatively, a wire, fiber, or the like is wound around to be
fixed such that the metal piece or the inorganic material and the
base material can maintain the fixed state.
[0046] In the downhole plug used in the present embodiment, in the
case of the mandrel 11 made of the degradable material, the
degradable material is preferably a hydrolyzable material degraded
with water at a predetermined temperature or more. Preferably, the
degradable material mainly contains PGA. Among PGAs, polyglycolic
acid having a weight average molecular weight of 150000 or greater
is preferable, and high molecular weight polyglycolic acid having a
weight average molecular weight of 180000 or greater is especially
preferable because of its high strength. That is, a downhole plug
with the mandrel 11 made of PGA with high molecular weight is
desirable. Furthermore, the degradable material may contain a
reinforcing material or can contain another ingredient. Degradable
metal is also usable as the degradable material forming the mandrel
11. Because of having high strength, Mg alloy is preferable as the
degradable metal used for the mandrel 11.
2) Members Mounted on Outer Peripheral Surface Orthogonal to Axial
Direction of Mandrel
[0047] The downhole plug used in the present embodiment includes
the mandrel and the members mounted on the outer peripheral surface
orthogonal to the axial direction of the mandrel. That is, in the
downhole plug, for efficiently and reliably performing the
transport and installation of this plug, plugging of the wellbore,
and fracturing, various members are typically mounted on the outer
peripheral surface of the mandrel additionally for the purpose of
improving ease of handling and the like. The members mounted on the
outer peripheral surface orthogonal to the axial direction of the
mandrel are not particularly limited as long as the members are
conventionally used in the downhole plug. In particular, as
illustrated in FIG. 3, regarding the frac plug 1, at least one of
members selected from a group of a slip 12, a wedge 13, a pair of
ring-shaped fixing members 14, and the diameter expandable circular
rubber member 15 is preferable. Note that these members are
referred to as members in the meaning including mounting members
for mounting of the respective members to the mandrel.
Material Forming Member Mounted on Outer Peripheral Surface
Orthogonal to Axial Direction of Mandrel
[0048] The material forming the member mounted on the outer
peripheral surface of the mandrel used in the present embodiment is
not particularly limited, and a material conventionally used as a
material forming this member provided in the downhole plug is
usable. Examples of the material can include a metal material
(aluminum, steel, stainless steel, and the like), fiber, wood, a
composite material, resin, and the like. Specifically, the material
can include a composite material containing a reinforcing material
such as carbon fiber, particularly a composite material containing
polymer such as epoxy resin and phenol resin, and the like. From a
perspective that the cost reduction and the shortening of process
for well drilling can be achieved through ease of release of the
plugging and securing of the flow path after use, at least one of
the members is preferably made of a degradable material, similarly
as previously described regarding the mandrel.
Degradable Material
[0049] In the downhole plug used in the present embodiment, as the
degradable material forming at least one of the members, similarly
as previously described regarding the mandrel, the degradable
material having biodegradability or hydrolyzability, additionally a
degradable material that can be chemically degraded by any other
method, and a degradable material that can be embrittled and easily
disintegrated are usable. With the member being a diameter
expandable circular rubber member, as the degradable material, for
example, degradable rubber such as aliphatic polyester-based
rubber, polyurethane rubber, natural rubber, polyisoprene, acrylic
rubber, aliphatic polyester rubber, polyester-based thermoplastic
elastomer, and polyamide-based thermoplastic elastomer are
usable.
3) Operating and Installing Downhole Plug and Plugging Wellbore
[0050] The downhole plug used in the present embodiment is operated
by the setting tool described later and installed in the wellbore.
For example, in the frac plug 1, an application of a force that
reduces a distance between the pair of ring-shaped fixing members
14 in the axial direction of the mandrel causes the slip 12 to
climb on an inclined top surface of the wedge 13 and to move
outward orthogonal to the axial direction of the mandrel. Then, the
outermost circumferential surface of this slip 12 orthogonal to the
axial direction of the mandrel abuts on the inner wall of the
wellbore, and thus the plug can be installed at a predetermined
position in the wellbore. Additionally, in association with the
diameter expandable circular rubber member 15 being compressed in
the axial direction of the mandrel to decrease the axial distance
(decrease in diameter), the diameter expandable circular rubber
member 15 expands in diameter in the direction orthogonal to the
axial direction of the mandrel. This circular rubber member 15
expands in diameter and the outward portion in the direction
orthogonal to the axial direction abuts on the inner wall of the
wellbore and further the inward portion in the direction orthogonal
to the axial direction abuts on the outer peripheral surface of the
mandrel, thereby ensuring plugging (sealing) the space between the
plug 1 and the wellbore (plugging of wellbore). Then, in the state
where the space between the plug and the wellbore has been plugged
(sealed), fracturing can be performed.
(2) Setting Tool
[0051] The setting tool used in the well plugging apparatus of the
present embodiment has an approximately columnar shape and includes
the setting rod and the setting sleeve. The setting rod typically
has a rod shape and is centered in a cross-section of the setting
tool (cross-section parallel to the bottom surface of the
approximate column). That is, the setting rod is inserted into the
hollow portion of the setting tool. The setting sleeve has a
tubular shape surrounding one end of a long shaft of the setting
rod.
[0052] The setting tool itself or a part of the setting tool of the
present embodiment is sometimes referred to as an adapter kit, and
the adapter kit includes a setting rod and a setting sleeve.
[0053] The setting tool used in the present embodiment is disposed
from the rear with respect to the rear end of the downhole plug to
the rear end side in the hollow portion, and the setting rod and
the setting tool are each in contact with the downhole plug. That
is, the setting rod is directly or indirectly connected to the
mandrel, and the setting sleeve is installed adjacent to the member
mounted on the outer peripheral surface orthogonal to the axial
direction of the mandrel. When the setting tool is operated, while
the setting sleeve suppresses the movement of the member mounted on
the outer peripheral surface of the mandrel in the rear end
direction, the setting rod moves in the rear end direction and
transmits the force in the rear end direction to the mandrel to
pull out the mandrel in the rear end direction, and the downhole
plug operates as described above. An example includes a setting
tool that includes a setting sleeve and a setting rod operated by
gas generated by explosion.
1) Setting Rod
[0054] In the well plugging apparatus of the present embodiment,
while the setting rod is connected to the mandrel, the setting rod
is typically directly or indirectly connected to the mandrel at the
end portion on the side opposite to the end portion surrounded by
the setting sleeve. The setting rod is inserted into the hollow
portion of the mandrel from the opening at the rear of the mandrel.
Although the connecting position of the mandrel with the setting
rod may be the rear end side, the center, or the front end side of
the mandrel in the longitudinal axial direction, in a case where
compressive strength is insufficient due to the mandrel made of
resin or the like, the setting rod is preferably connected to the
front end side of the mandrel. In this case, the setting rod is
connected to the front end side from the rear end side of the
mandrel through the hollow portion. The following describes an
example of connecting the setting rod to the front end of the
mandrel with reference to FIG. 2 and FIG. 3.
[0055] A setting rod 21 in FIG. 2 is connected to the downhole plug
1 with a connection portion 23. A method for connecting the
connection portion 23 includes a method for directly connecting and
fixing the connection portion 23 to the front end of the mandrel 11
and a method for indirectly connecting and fixing the connection
portion 23 via a connection member (not illustrated) installed on
the front end of the mandrel 11 and installed on the mandrel 11. A
method for fixing the connection portion 23 to the downhole plug 1
includes a method for fixing the connection portion 23 to the
downhole plug 1 using a screw engraved on the outer periphery of
the connection portion 23 and a method for fixing the connection
portion 23 with a pin. The screw and the pin are preferably damaged
due to a force applied in the axial direction of the mandrel to
disconnect the downhole plug and the setting tool.
[0056] As described later, in the well plugging apparatus of the
present embodiment, the obstacle is disposed in a space formed by
the setting sleeve inner wall, the setting rod, and the mandrel
rear end or the member mounted on the rear end. Accordingly, the
setting rod may be deformed by, for example, recessing, bending, or
shaving a part of the rod into a sector shape in the axial
direction such that the setting sleeve can internally include the
obstacle (ball). In other words, the setting rod may have a groove
or a notch structure to the axial direction.
[0057] Specific examples of the deformation of the setting rod
include: a part of a round shape as a cross-section of the setting
rod being cut off into a straight line shape (FIG. 5A), cut off
into a curvilinear shape (FIG. 5B), cut off into angular shapes
(FIGS. 5C and 5C'), or the like.
[0058] Although a position and a length of the deformation in the
entire length of the setting rod are not particularly limited as
long as the function of the setting rod is not inhibited, the
deformed parts illustrated in FIGS. 5A to 5C' are preferably on the
front end side in the length from the distal end (front end) of the
setting rod not connected to the downhole plug to the rear end of
the downhole plug. Additionally, the length of the deformed part is
preferably 10 mm or more in the axial direction of the setting
rod.
2) Setting Sleeve
[0059] A setting sleeve 22 of the present embodiment is positioned
adjacent to the rear end side of the member mounted on the outer
peripheral surface of the mandrel 11, and has a function of
suppressing the movement of the member on the outer peripheral
surface of the mandrel to the rear side.
[0060] In addition, similarly to the setting rod, the setting
sleeve may have a groove or a notch structure in the inner wall
such that the setting sleeve can internally include the obstacle
(ball). Specific examples of the groove in the setting sleeve inner
wall include a curvilinear groove (FIG. 6A) or angular grooves
(FIGS. 5B and 6C) in the cross-section of the setting sleeve.
[0061] The groove in the setting sleeve inner wall only needs to
have a shape that the setting sleeve can internally include the
obstacle and the position, the length, and the depth are not
particularly limited. However, the grooves illustrated in FIGS. 6A
to 6C preferably have a length (in the axial direction of the
setting sleeve) of 10 mm or greater, a width of 5 mm or greater,
and a depth of 1 mm or greater.
Material Forming Setting Tool
[0062] The material forming the setting tool used in the present
embodiment is not particularly limited, and conventionally used
materials are usable.
(3) Obstacle for Plugging Flow Path in Downhole Plug
[0063] The obstacle for plugging the flow path in the downhole plug
used in the present embodiment is disposed in the space formed by
the setting sleeve inner wall and the setting rod of the setting
tool, and the mandrel rear end or the member mounted on the rear
end. The obstacle for plugging the flow path in the downhole plug
has a function to plug the flow path in the downhole plug after the
downhole plug is installed in the well and the setting rod is
removed. As long as the flow path in the downhole plug can be
plugged and the obstacle has the size and the shape that can be
fallen into the space in the above-described setting tool, the
shape of the obstacle is not particularly limited and, for example,
includes shapes such as a ball, a dart, or a disk. Among these
obstacles, the ball can plug the opening of the seat regardless of
the seated direction and the flow path can be plugged reliably and
therefore is preferable.
Material Forming Obstacle to Plug Flow Path in Downhole Plug
[0064] The material forming the obstacle to plug the flow path in
the downhole plug used in the present embodiment is not
particularly limited, and materials conventionally used as
materials forming this obstacle are usable. Examples of the
material can include a metal material (aluminum, steel, stainless
steel, or the like), fiber, wood, a composite material, resin, and
the like. Specifically, the materials can include a composite
material containing a reinforcing material such as carbon fiber,
and particularly a composite material containing polymer such as
epoxy resin and phenol resin, and the like. From a perspective that
the cost reduction and the shortening of process for well drilling
can be achieved through ease of release of the plugging and
securing of the flow path after the use of the downhole plug, at
least a part of the obstacle is preferably made of a degradable
material, similarly as previously described regarding the mandrel.
The degradable material mainly containing PGA is more preferred. In
a case of the use of PGA as the main component, the weight average
molecular weight of PGA is preferably large from a perspective of
increasing strength, for example, 50000 or greater is preferable,
100000 or greater is more preferable, and 150000 or greater is
further preferable.
Degradable Material
[0065] As the degradable material forming the obstacle to plug the
flow path in the downhole plug used in the present embodiment,
similarly as previously described regarding the mandrel, the
degradable material having biodegradability or hydrolyzability,
additionally a degradable material that can be chemically degraded
by any other method, and a degradable material that can be
embrittled and easily disintegrated are usable. Among the
materials, degradable resin or degradable metal features ease of
adjustment of a degradation rate, and thus is preferable as the
degradable material used for the obstacle. In particular, because
of its high strength, polyglycolic acid is preferable as the
degradable resin, and Mg alloy is preferable as the degradable
metal.
[0066] With the well plugging apparatus of the above-described
present embodiment, the obstacle to plug the flow path in the
downhole plug can be reliably supplied in a short time. Thus,
damage in the obstacle accompanied by the transport of the obstacle
can be avoided and a fluid volume to transport the obstacle can be
saved. This allows reducing the cost for well drilling and allows
shortening the process for well drilling.
2. Method for Plugging Well
[0067] The well plugging apparatus of the present embodiment is
usable regardless of the depth of the well and whether a vertical
hole or a horizontal hole.
[0068] The method for plugging the well using the well plugging
apparatus of the present embodiment is as follows. First, the well
plugging apparatus of the present embodiment is moved to any
position inside the well using a fluid or the like (FIG. 4A). After
that, when the setting tool is operated, the annular rubber member
and the slip are expanded in diameters to install and fix the
downhole plug to the inner wall of the wellbore (FIG. 4B). Then,
the setting tool and the downhole plug are disconnected, and the
setting rod is removed from the hollow portion of the mandrel. The
obstacle internally included in the setting sleeve is supplied and
disposed at a position to plug the flow path in the downhole plug,
for example, the seat installed in the mandrel, thus completing the
plugging.
[0069] When the obstacle is made of, for example, the degradable
material having hydrolyzability, exposure of the obstacle under
water for a predetermined period degrades the obstacle, and
disintegrating, dissolving, or exiting the obstacle from the
opening of the seat (receptacle) allows recovering the plugged flow
path.
3. Summary
[0070] A well plugging apparatus for plugging a well that includes
a downhole plug, a setting tool, and one or more obstacles. The
setting tool is disposed on a rear end side of the downhole plug.
The setting tool operates and installs the downhole plug. The one
or more obstacles plug a flow path in the downhole plug. The
downhole plug includes a hollow mandrel that opens at least in a
rear end. The setting tool includes a setting rod directly or
indirectly connected to a front end side of the mandrel and a
setting sleeve disposed to cover at least a part of the setting rod
and at least a part of the downhole plug. The setting rod is
inserted from the opening in the rear end of the mandrel into the
hollow portion of the mandrel. The obstacle is internally included
in a space inside the setting tool.
[0071] Additionally, preferably the mandrel contains a resin as a
main component.
[0072] Additionally, preferably the mandrel contains a degradable
metal as a main component.
[0073] Additionally, preferably the mandrel contains a degradable
resin as a main component.
[0074] Additionally, preferably the downhole plug includes a seat
that receives the obstacle.
[0075] Additionally, preferably the obstacle is a ball, a dart, or
a disk.
[0076] Additionally, preferably the obstacle at least partially
contains a degradable material.
[0077] Additionally, preferably the degradable material is a
degradable resin or a degradable metal.
[0078] Additionally, preferably the mandrel has a rear end having a
notch structure configured to internally include the obstacle in a
space inside the setting tool.
[0079] Additionally, preferably at least one of the setting rod or
the setting sleeve has a groove or a notch structure with respect
to an axial direction configured to internally include the obstacle
in a space inside the setting tool.
[0080] Preferably at least one of the setting rod or the setting
sleeve has the sector-shaped notch structure with respect to the
axial direction configured to internally include the obstacle in
the space inside the setting tool.
[0081] Additionally, the setting rod has the groove or the notch
structure with respect to the axial direction.
[0082] Additionally, preferably the setting sleeve has a groove in
an inner surface.
[0083] There is provided a method for temporarily plugging a well
using a well plugging apparatus including a downhole plug, a
setting tool, and one or more obstacles. The setting tool is
disposed on a rear end side of the downhole plug. The setting tool
operates and installs the downhole plug. The one or more obstacles
plug a flow path in the downhole plug. The downhole plug includes a
hollow mandrel at least opening in a rear end. The setting tool
includes a setting rod directly or indirectly connected to a front
end side of the mandrel and a setting sleeve having a shape to
cover at least a part of the setting rod and at least a part of the
downhole plug. The setting rod is inserted from the opening in the
rear end of the mandrel into the hollow portion of the mandrel. The
obstacle is internally included in a space inside the setting tool.
The method includes the following steps a) to d): a) moving the
well plugging apparatus to any position in the well and operating
and installing the downhole plug; b) disconnecting the setting tool
and the downhole plug to pull out the setting rod; c) moving the
obstacle in the setting tool to plug the flow path in the hollow
portion of the mandrel; and d) after an elapse of a predetermined
period, removing the obstacle to recover the flow path.
INDUSTRIAL APPLICABILITY
[0084] The present invention is the well plugging apparatus
including the setting tool and the downhole plug that causes the
obstacle to plug the flow path in the downhole plug to be
internally included in the setting tool adjacent to the downhole
plug. Accordingly, the well plugging apparatus that can supply the
obstacle to the downhole plug in a short time and safely, avoid
damage in the obstacle, reduce the cost for well drilling including
saving of a fluid volume for transporting the obstacle, and shorten
the process is provided, bringing a high industrial applicability.
Additionally, the method for temporarily plugging the well using
the well plugging apparatus is provided, bringing a high industrial
applicability.
REFERENCE SIGNS LIST
[0085] 1 Frack plug [0086] 2 Setting tool [0087] 3 Ball [0088] 12a,
12b Slip [0089] 13a, 13b Wedge [0090] 14a, 14b Ring-shaped fixing
member [0091] 15 Diameter expandable circular rubber member [0092]
21 Setting rod [0093] 22 Setting sleeve [0094] 23 Connecting
portion between setting tool and frac plug [0095] H Inner wall of
wellbore
* * * * *