U.S. patent application number 15/291724 was filed with the patent office on 2018-04-12 for downhole tool to be used in a well beyond a restriction.
The applicant listed for this patent is Mark Garcez, Ramon Perales, Ruben Soliz. Invention is credited to Mark Garcez, Ramon Perales, Ruben Soliz.
Application Number | 20180100365 15/291724 |
Document ID | / |
Family ID | 61830030 |
Filed Date | 2018-04-12 |
United States Patent
Application |
20180100365 |
Kind Code |
A1 |
Perales; Ramon ; et
al. |
April 12, 2018 |
Downhole Tool to Be Used in a Well Beyond a Restriction
Abstract
The invention is a retrievable downhole oil tool which can
travel beyond and set beneath a restriction in casing which has a
larger inner diameter than that of the restriction. The tool can
later unset and travel back up past the restriction to be
retrieved. Design of the tool allows for a larger inner diameter
than existing tools with the same outer diameter; slips which reach
out further than those of existing tools, from the outer diameter
of the tool to the inner diameter of the casing; and several
features which prevent damage to the tool while it squeezes through
a restriction.
Inventors: |
Perales; Ramon; (Karnes
City, TX) ; Soliz; Ruben; (Kenedy, TX) ;
Garcez; Mark; (Karnes City, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Perales; Ramon
Soliz; Ruben
Garcez; Mark |
Karnes City
Kenedy
Karnes City |
TX
TX
TX |
US
US
US |
|
|
Family ID: |
61830030 |
Appl. No.: |
15/291724 |
Filed: |
October 12, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 23/01 20130101 |
International
Class: |
E21B 23/01 20060101
E21B023/01 |
Claims
1. A retrievable downhole oil tool intended to set in a well,
comprising: (a) A slip cage and a drag spring cage that are not
radially concentric with each other; and (b) A drag spring cage
which has a smaller outer diameter (not including any drag springs
or blocks) than the slip cage; and (c) A plurality of slips which
each have a vertical slot in the middle; and (d) Conical or leaf
springs trapped between the slot of each slip and the underside of
the slip cage.
2. The tool of claim 1, which additionally comprises a backup ring
surrounding a mandrel; which backup ring has contact with the
mandrel along the backup ring's entire inner surface; and which
backup ring prevents the drag spring cage from moving up along the
mandrel.
3. The tool of claim 1, which additionally comprises: (a) Shear
pins located above or below the slip cage and drag spring cage; and
(b) A shear pin cap which protects the shear pins.
4. The tool of claim 2, which is set by a mechanical method.
5. The tool of claim 3, which is set by a mechanical method.
6. The tool of claim 1, which additionally comprises (a) An upper
cone which moves down along a threaded portion of the mandrel; and
(b) A lower cone which does not move in relation to the mandrel,
and which is longer than the upper cone.
7. The tool of claim 1, which is a tubing anchor catcher.
8. The tool of claim 2, which is a tubing anchor catcher.
9. The tool of claim 3, which is a tubing anchor catcher.
10. The tool of claim 4, which is a tubing anchor catcher.
11. The tool of claim 5, which is a tubing anchor catcher.
12. The tool of claim 6, which is a tubing anchor catcher.
13. A method of making a downhole oil tool which can travel beyond
a restriction in a well with casing, which can securely set in a
location beyond the restriction where the casing has a larger inner
diameter than that present at the restriction, and which can later
be retrieved and successfully travel past the restriction,
comprising the steps of: (a) Choosing a mandrel with a smaller
inner diameter and a smaller outer diameter than the inner diameter
of the casing at the restriction; (b) Mounting a generally tubular
drag spring cage and a generally tubular slip cage on said mandrel
in positions surrounding the mandrel such that the two cages are
not radially concentric; (c) Choosing a drag spring cage with a
smaller outer diameter than that of the slip cage; (d) Choosing
slips with a toothed side and a smooth side opposite to the toothed
side, which slips each have a slot positioned vertically on the
toothed side, such that the toothed side of the slip is divided
into two surfaces, while the smooth side is left intact; (e)
Choosing conical springs or leaf springs; and (f) Installing a
plurality of said slips radially in between said mandrel and said
slip cage, and inserting one or more conical springs or leaf
springs into the slot of each slip, such that each spring is
trapped between the slot of a slip and the slip cage.
14. The method of claim 13, additionally comprising the step of:
(g) Installing a backup ring on a groove on said mandrel, which
backup ring has contact with the mandrel along the backup ring's
entire inner surface; and which backup ring prevents the drag
spring cage from moving up along the mandrel.
15. The method of claim 14, additionally comprising the steps of:
(h) Installing a plurality of shear pins in a location on the tool
which is axially below both the drag spring cage and the slip cage;
and (i) Installing a shear pin cap concentrically outside of the
shear pins, thus protecting said shear pins from substances and
forces in the well.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates to downhole oil tools which
are used during completion and production of an oil or gas well,
particularly a retrievable tool which can set securely below a
restriction or tight spot in the casing of the well.
Description of the Related Art
[0002] When drilling a well, casing is often installed to protect
the integrity of the hole. The widest casing is set at the top of
the hole, and successively narrower casing must travel down the
hole through the wider casings, so that the inner diameter of the
well gets narrower as the depth increases. In other words, the
inner diameter is wider at the top of the hole, and narrower at the
bottom of the hole, and the inner diameter steadily decreases from
top to bottom. Occasionally, the casing is installed in a different
configuration, with wider casing placed below narrower casing. We
call this inverted casing.
[0003] Sizes of casing are referred to by outer diameter in inches,
and weight in pounds per foot, which can be used to figure the
inner diameter. Sometimes a restriction or "tight spot" (these
terms used as synonyms in this specification) exists in the casing,
which can be caused for example by a casing patch, or inverted
casing installation. At the tight spot, the inner diameter of the
casing is smaller than the inner diameter below the tight spot or
restriction.
[0004] An anchor is a tool which is attached to the tubing string,
and which may be securely set at a given depth, to keep the tubing
and other tools attached to the tubing in vertical place. Each
anchor is manufactured to use a given setting method, such as
mechanical or hydraulic. An anchor travels down through the hole in
an unset state, and then is set using its given method. A
mechanical anchor, like the one described herein, can be set and
released and re-used many times; although it sets securely at a
given depth, it is not permanently set there. Mechanical anchors
are cost-effective and versatile, in that the operator can release
the anchor and re-set it at any time.
[0005] One type of anchor is a tubing anchor catcher, which is used
during production to anchor the tubing string at a desired depth,
and also to catch and prevent any parted tubing pipe from falling
into the well. As with all downhole oil tools, the operator
normally chooses a tubing anchor catcher with the largest outer
diameter and largest inner diameter possible, dependent upon the
inner diameter of the casing which is present at the depth where
the anchor is intended to set. A tool with a large inner diameter
is desirable so that the greater volume of fluid or gas per time
period can travel down or up through the inside of the anchor.
[0006] The mechanical rotational setting mechanism of an anchor
must be quite precise in order to work properly. When the anchor
reaches the appropriate depth, the operator rotates the tubing,
which begins the process of engaging the setting mechanism. The
drag springs or blocks must touch the casing with sufficient
friction and force so as to prevent the slip cage from rotating.
The drag spring cage must also stay in the same precise vertical
relationship with the slip cage, with the exact distance between
them preserved, so that when the cone moves downward, the slips are
in the right place, allowing the cones to push out the slips evenly
and correctly, and causing the slips to get a secure hold on the
casing with even amounts of pressure along the entire surface area
of the several slips.
[0007] Several problems exist when attempting to lower and set a
retrievable anchor below a tight spot: 1) The drag springs or
blocks must be able to contact the casing with sufficient force at
the wider setting depth, but also pass through the narrower tight
spot without deforming permanently. 2) The drag spring assembly
must make a tight squeeze through the restriction without moving
vertically up or down in relation to the rest of the tool. 3) While
the outer diameter of the entire tool must be small enough to pass
through the tight spot, it is still desirable to have the biggest
inner diameter possible inside the tool. 4) Depending upon their
placement in the tool, the shear pins or screws may be very
difficult to access and change; or they may be exposed to fluids,
debris and corrosion in the well, causing them to clog and may be
impossible to change out; or a tight spot may cause them to be
prematurely sheared. 5) The slips must somehow extend further out
than usual in order to set securely against the wider casing. 6)
The slips must set with sufficient outward force to hold securely,
without deforming the casing. 7) Finally, the tool must be able to
release, retract slips and pass through the restriction when coming
out of the well.
[0008] Tight spots happen occasionally, and the inventors are
unaware of any retrievable mechanical or hydraulic anchors which
can successfully travel through a tight spot and set in casing
below with a wider inner diameter. Sometimes the operator must
resort to setting a tubing anchor catcher with a smaller outer
diameter directly in the tight spot or casing patch, thereby
settling for a smaller inner diameter in the tool, causing slower
production. Sometimes an operator will abandon a well because it is
too expensive to solve all of the problems associated with a tight
spot.
BRIEF SUMMARY OF THE INVENTION
[0009] This invention is a downhole oil tool which successfully
travels through casing restrictions; sets securely in wider casing
below; has a large inner diameter; and, if mechanically set,
retains all benefits of a mechanically set tool including
affordability, a high pressure rating, removability, reusability,
and no need for special equipment. The tool can achieve this
through a combination of several separate improvements and
innovations in its design: [0010] A backup ring which contacts the
mandrel along the entire inner surface area of the backup ring, as
well as along a portion of the top and bottom surface area of the
backup ring, so as to robustly prevent the drag spring assembly
from moving vertically closer to or further from the cone below;
[0011] Shear pins which are easily accessible and not trapped
inside the slip cage or drag spring cage, and are also protected by
a shear pin cap; [0012] The spatial relationship of the drag spring
assembly and the slip assembly: they are not radially concentric,
but instead the entire drag spring assembly is positioned
completely above or below the slip assembly, helping make the outer
diameter of the entire tool smaller while keeping the inner
diameter as big as possible; [0013] Use of drag springs rather than
conventional drag blocks, because drag springs are able to compress
through a tight spot, and conventional drag blocks cannot compress
or extend far enough; [0014] A drag spring cage with a narrower
outer diameter than the slip cage, to combat the problem of drag
springs permanently deforming if they compress too much and scrape
too hard against a narrow casing or restriction; [0015] Use of
conical springs or leaf springs to push the slips inwards while in
running (unset) position; both conical springs and leaf springs
compress farther than regular coil springs, allowing the cone to
push the slips out farther than a cylindrical coil spring would
allow; [0016] A stationary lower cone which is longer than the
moving upper cone, so that as the upper cone travels down the
mandrel toward and underneath the slips, it has more time and area
to push the slips out a greater distance than a conventional anchor
slip assembly would; [0017] Slips designed with a groove vertically
down the middle, to accommodate the conical springs in the
resulting pocket, and making each slip have two long and thin
surface areas to contact the casing. The slip may also include a
leaf spring in its pocket instead of conical springs. More points
of contact supporting the same load makes deformation of the casing
less likely; and [0018] Extra long slips which are pushed out and
supported by extra long cones, to enhance the robustness and
security of the contact with the well casing while in set
position.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0019] FIG. 1 shows a full exterior view of an anchor with the
setting mechanism of slips in running (unset) position, before it
is set in the casing.
[0020] FIG. 2 shows a lengthwise cutaway view of the anchor in FIG.
1.
[0021] FIG. 3 shows a full exterior view of the same anchor shown
in FIGS. 1 and 2, which has been set in the well casing with the
well casing shown cut away. The setting mechanism is shown holding
onto the casing.
[0022] FIG. 4 shows a lengthwise cutaway view of the anchor shown
installed in casing in FIG. 3.
[0023] FIG. 5 shows a transverse cutaway view of the same anchor
shown in FIGS. 1 and 2, in its running (unset) position with slips
fully retracted, cut at the level of the upper slip spring, and
viewed looking up.
[0024] FIG. 6 shows a transverse cutaway view of the same anchor,
cut at the same level as FIG. 5, except that the slip mechanism is
shown in its set position, with slips fully extended, and viewed
looking up.
[0025] FIG. 7 shows a partial lengthwise cutaway view of the same
anchor shown in all previous figures, and shows the slip assembly
portion of the tool in its running (unset) position, with slips
fully retracted.
[0026] FIG. 8 shows a partial lengthwise cutaway view of the same
anchor shown in all previous figures, and shows the slip assembly
portion of the tool in its set position, with slips fully
extended.
[0027] FIG. 9 shows an embodiment of the slip used in the anchor
previously pictured.
[0028] FIG. 10 shows an enlarged cutaway view of a portion of the
anchor in FIG. 1, including the backup ring and stop ring.
DETAILED DESCRIPTION OF THE INVENTION
[0029] The subject of this invention is a retrievable downhole oil
tool which can pass through a restriction of small inner diameter
in the casing, and then set in a lower larger inner diameter of
casing. Design of the invention allows the tool to have an outer
diameter small enough to pass through the tight spot or
restriction; an inner diameter which is as big as possible; and a
setting mechanism which is able to expand sufficiently to securely
set in the lower wider casing. Features of the invention also allow
the tool to retain functionality without damage after squeezing
through a restriction.
[0030] This paragraph contains a very high level description of how
a downhole oil tool such as this works. The tool is basically a
hollow tube with parts mounted on the outside circumference. The
parts on the outside are precisely mounted on the tube and in
relation to each other, to make it possible for the tool to set
securely in one spot down in the well for a period of time, and
also for the tool to be unset and retrieved later. In a
mechanically set tool, in order to set the tool, the operator
rotates and lifts the tube, and a large group of the mounted parts
stays vertically stationary and does not rotate or move up with the
tube. A small group of parts does rotate and move with the tube,
and that group of parts interacts with the stationary group of
parts, ultimately causing some of the vertically stationary parts
to move radially outwards and push against the inner wall of the
well with sufficient force to keep the tool anchored at that spot.
When it is time to retrieve the tool, the operator rotates the tube
in the opposite direction, reversing the setting process, and
causing the rotating group of parts to move back into original
position, which causes the anchoring parts to move away from the
inner wall of the well, releasing the tool. Sometimes the tube can
no longer rotate, due to debris or corrosion inside the tool; in
this case, an emergency backup method is used, lifting the tube
straight up with a greater amount of force sufficient to shear some
small pins or screws, allowing some of the parts to loosen so that
the anchoring parts are no longer forced out against the inner wall
of the well. Either way, the tool can then be retrieved.
[0031] FIGS. 1 and 2 show an embodiment of the invention in its
running (unset) position, with slips 13 retracted to minimize the
outer diameter of the tool as it travels up or down inside the
hole. FIGS. 3 and 4 show the same embodiment of the invention in
its set position, installed inside the casing. This tool is
installed in casing in the orientation shown, with 1 on the top and
20 on the bottom.
[0032] 1 is a top sub, which is screwed onto the outside of the
mandrel or body 2. The top sub is also threadedly connected with
the tubing 22, as shown in FIGS. 3 and 4. The hollow mandrel 2
extends from the top to the bottom of the tool, and all of the
other parts are mounted upon the mandrel 2 in various ways. The
mandrel 2 has a stop ring 3 and a backup ring 4 installed below the
top sub 1, in a groove which has been cut into the mandrel 2, with
a precise amount of space left between the top sub 1 and the top of
the stop ring 3. See FIG. 10 for a detailed view of the backup ring
4 area of the tool. The backup ring 4 securely fits into the groove
on the mandrel 2 such that the backup ring 4 does not move up along
the axis of the mandrel 2, and the backup ring 4 may or may not
rotate with the mandrel. The backup ring 4 is actually a ring
divided into two pieces along the line of its diameter, which
permits it to be installed in the groove of the mandrel 2.
[0033] The stop ring 3 is threadedly attached to the top of the
drag spring cage 6, and these two parts closely surround the backup
ring 4, preventing the two pieces of the backup ring 4 from
separating or coming loose. The stop ring 3 is loosely attached to
the mandrel 2 so that when the mandrel 2 rotates during the setting
procedure, the stop ring 3 will not rotate. A set screw 5 keeps the
stop ring 3 and drag spring cage 6 together, so that the connection
between the two does not come loose. The drag spring cage 6 is
located both radially outside and below the backup ring 4, and
contacts the outside and bottom surfaces of the backup ring 4 which
is sticking out of the groove. The drag spring assembly is made up
of a drag spring cage or housing 6, which surrounds but is not
fastened to the mandrel 2; and the drag springs 7 which are
securely attached to the outside of the drag spring cage 6 with
drag spring screws 8.
[0034] The slip assembly is located directly below the drag spring
assembly, and it is securely fastened to the drag spring assembly
with a set screw 10. FIGS. 1 and 3 show the location of said set
screw 10, although the set screw would not be visible in these
views. Said set screw 10 keeps the drag spring cage 6 and slip cage
9 together, so that the connection does not come loose. The slip
assembly also surrounds but is not fastened to the mandrel 2. FIGS.
5, 6, 7 and 8 show the slip assembly in greater detail. The slip
assembly consists of a slip cage 9 with cutouts; the slips 13 which
extend out through the cutouts during the setting procedure; and
conical springs 14. Each slip 13 has a slot or pocket, shown in
FIGS. 5, 6 and 9, which is where conical springs 14 rest, touching
the underside of the slip cage 9. Leaf springs may also be used
instead of conical springs. FIGS. 3 and 4 show the location of the
conical springs 14, although the conical springs 14 would not be
visible in these views. When extended, the toothed surfaces of each
slip 13 project through cutouts in the slip cage 9, and each slip
13 straddles a portion of the slip cage 9.
[0035] An upper cone 12 is threadedly connected with the mandrel 2,
and is situated between the mandrel 2 and the upper end of the slip
cage 9. Pipe plugs 11 are attached to the upper cone 12, and the
pipe plugs protrude outward through cutouts in the slip cage 9.
These cutouts (see pipe plugs 11 in FIGS. 1, 2 and 3) are separate
from the cutouts located at the slips (see slips 13 in FIGS. 1, 2
and 3.) The pipe plugs 11 prevent the upper cone 12 from rotating
with the mandrel 2 during the setting and unsetting procedures. A
lower cone 15 is installed surrounding the mandrel 2 between the
mandrel 2 and the slip cage 9, within the lower end of, but not
affixed to, the slip cage 9. Radially inside the lower portion of
the lower cone 15, the bottom sub 16 is threadedly connected to the
mandrel 2, and a set screw 16 prevents the bottom sub 20 and
mandrel 2 from unscrewing and separating. An O ring 17 is installed
just under the set screw 16, between the bottom sub 20 and the
mandrel 2, to provide a seal at that connection. Said O ring 17 is
shown in FIGS. 2 and 4, and its location is shown on FIG. 3,
although the O ring 17 would not be visible in this view.
[0036] Shear pins 19 covered by a shear pin cap 18 are situated
below the slip assembly. Each shear pin 19 is embedded in the
bottom sub 16 and protrudes radially outward, such that it holds
the lower cone 15 in place and prevents it from sliding axially
downward. As shown in FIGS. 2 and 4, the upper portion of the lower
cone 15 has a smaller inner diameter, where it contacts and
surrounds the mandrel 2. The lower portion of the lower cone 15 has
a larger inner diameter, to accommodate the bottom sub 16 which has
a larger outer diameter than the mandrel 2. The difference between
the inner diameters of the lower cone 15 creates a shoulder which
will be significant during an emergency backup unsetting procedure.
In the event that the normal manual unsetting procedure fails, then
the emergency backup unsetting method involves pulling up on the
tubing 22 and mandrel 2 with sufficient force to shear off the
shear pins 19. The lower cone 15, no longer supported by the shear
pins 9, falls downward until its shoulder rests on the top of the
bottom sub 16.
[0037] The outer diameter of a tool including the innovations of
this invention is reduced, as compared to typical tools of a given
inner diameter, by moving the drag spring assembly to a position
above or below the slip assembly, rather than at the same level.
FIGS. 1, 2, 3 and 4 show the drag spring assembly installed above
the slip assembly. Most anchors have these two assemblies at the
same level, with the drag springs or blocks radially outside of the
slips. The conventional design allows the tool to be axially
shorter, which is desirable to avoid the tool getting stuck if must
pass through a dogleg in the casing. However, when comparing a
conventionally designed tool of a given inner diameter with the
innovative tool of this invention with the same inner diameter, the
conventional tool would have a larger outer diameter.
[0038] A tool which includes the innovations of this invention must
use drag springs rather than conventional drag blocks, because drag
springs can compress without deforming when passing through a
restriction. In addition, the drag spring cage 6 has a smaller
outer diameter than the slip cage 9, which minimizes the
compression of the drag springs 7, further reducing the risk of
permanently deforming the drag springs 7 when squeezing through a
restriction.
[0039] Two additional features prevent damage to the tool while it
passes through a restriction: first, the backup ring 3 located
below the top sub 1 and above the drag spring cage 6 contacts the
mandrel 2 in a groove with the backup ring's full inner surface
area, as well as with a portion of the backup ring's top surface
area, rather than being attached to the mandrel 2 with a
conventional body nut. This contact area makes the backup ring 3
exceptionally robust, so that it will not fail when the tool passes
through a tight spot, when the drag springs 7 will squeeze against
the casing 21 and cause the drag spring housing 6 to push up hard
against the backup ring 3. The purpose of the backup ring 3 is to
keep the various parts of the tool which surround the mandrel 2
exactly in place and in the correct vertical placement in relation
to each other, so that the setting mechanism will work properly.
FIG. 10 shows an enlarged view of the backup ring and surrounding
parts.
[0040] The second additional feature which prevents damage to the
tool while passing through a restriction is a shear pin cap 18,
which protects the shear pins 19 at the bottom of the tool while
allowing them to be easily accessible. The purpose of the shear
pins 19 is to be able to release the tool as an emergency backup
method, so that it can be retrieved. Depending upon conditions of
the well where the tool will be set, the operator may want to
change the shear pins 19 before attaching the tool to the tubing
string 22. The placement of the shear pins 19 under a shear pin cap
18, rather than the conventional placement of shear pins between
the housing and the cone, makes it much easier to change out the
shear pins 19. The shear pin cap 18 is easily removed by the
operator with a wrench. Shear pins are usually placed deep within
the tool so as to shorten the tool, but this makes changing the
pins a tedious job, requiring the operator to substantially take
apart the tool to access the shear pins.
[0041] Some tools use shear screws, which are supposed to be easier
to replace because they are easily accessible on the outside of the
tool, but in practice, the heads of the screws often get covered
with debris and corrode while the tool is in the hole, and the
screws are then impossible to remove. The shear pin cap 18 protects
the shear pins 19 from debris and corrosion in the hole, as well as
from being prematurely stressed and/or sheared against the casing
21 while passing through a tight spot.
[0042] After the tool passes through a tight spot, it must then
extend out and set securely in casing 21 which has a larger inner
diameter than the restriction. The tool is able to do this because
of the innovative slip assembly design, which is shown in FIGS. 5,
6, 7 and 8. Each of the slips 13 is axially longer than normal, and
has a slot, or pocket, partially machined out of the outer toothed
side, from top to bottom, so that the toothed outer surface of each
slip 13 is divided into two separate toothed surfaces, still
connected on the undersurface. See FIG. 9 which shows a slip by
itself. FIG. 7 shows a slip on the right which is cut away in the
middle, so that its base is cut away and shaded, and the outer
portion of the slip is not cut away, because of the existing slot,
so it is not shaded. Each slip 13 is contained within the slip cage
9, with conical springs 14 which fit exactly in the pocket, and
which contact both the underside of the slip cage 9 and the outer
surface of the pocket in the slip 13. In running (unset) position,
these springs 14 are uncompressed and push the slips 13 inside of
the slip cage 9, so that the outer edges of the slips 13 do not
extend outside of the slip cage 9 at all. FIGS. 5 and 7 show
different views of the slip assembly design in running (unset)
position, with slips 13 fully retracted. FIG. 5 shows the tool cut
at a point at the bottom edge of the upper conical spring 14--see
FIG. 2. The slips 13 are touching the mandrel 2, and the upper cone
12 is shown above the slips 13, not contacting them at all yet.
[0043] During the setting process, the operator rotates the tubing
22, which causes the mandrel 2 to rotate, but the drag springs 7
prevent the slip assembly from rotating. Pipe plugs 11 are attached
to the upper cone 12 to prevent the upper cone 12 from rotating
with the mandrel 2. Rotation of the mandrel 2 causes the upper cone
12 to travel downward on a threaded portion of the mandrel 2 toward
the slips 13 and the stationary lower cone 15. The angle of each
conical surface matches the angle of the underside of each slip 13,
and so as the upper cone 12 moves down under each slip 13, it
pushes the slip 13 downward, causing the entire slip cage 9 to move
downward toward the stationary lower cone 15.
[0044] Between the time that the upper cone 12 first contacts the
upper edge of the slips 13 and the time that the lower edge of the
slips 13 first contact the lower cone 15, the slips 13 do not move
radially outward very much, because the conical springs 14 which
rest in the pocket of the slips 13 and contact the slip cage 9
provide resistance against outward movement. When the underside of
the slips 13 meet the lower cone 15 however, further travel of the
upper cone 12 down the threaded portion of the mandrel 2 causes the
slips 13 to move radially outward as well as down, as they are
pushed outward along the slanted edges of both the upper 12 and
lower cones 15. Since the slips 13 can no longer move downward
easily, the force of the upper cone's 12 movement overcomes the
springs' 14 resistance and the slips 13 are pushed outward until
they forcibly grip the well casing 21. The slips 13 themselves and
the conical surfaces of both cones are longer than normal, which
allows the slips 13 to be pushed out farther at a conventional
angle.
[0045] As each slip 13 is pushed radially outwards, the conical
springs 14 between the slip 13 and the slip cage 9 are compressed.
When fully compressed, the conical springs 14 are basically flat,
allowing the slips 13 to extend outwards as much as possible, more
than conventional cylindrical springs in the pocket would allow.
Leaf springs have the same function as conical springs, in that
they push the slips inside of the slip cage while the tool is in
running (unset) position, and the leaf springs are basically flat
when fully compressed, when the tool is set. FIGS. 6 and 8 show the
slip assembly in set position, with the cones 15 pushing out the
slips 13, and the slips 13 sufficiently extended to reach out to
the casing wall 21. The two white donut-shaped areas in FIG. 6
represent the upper cone--the inner part is the lower edge of the
cone, closest to the viewer, and the outer part shown is the
conical sides of the cone, the outer diameter increasing as it gets
further from the viewer. Note that FIG. 6 shows the tool in set
position, but not installed in casing--if it were installed in
casing, the drag springs would be compressed by the casing, and
would radially reach out the same distance as the slips. Using
springs which compress so much is important to the design, because
the reduced space between the inner diameter and the outer diameter
of the tool limits the possible thickness of the slips. The slips
must extend outwards farther than slips in a conventional tool,
since the outer diameter of the tool is reduced in order to pass
through a restriction, and so it is important that the springs not
reduce the extent to which the slips can jut outward and grab onto
the wider casing.
[0046] The slip design has more points of contact with the casing
than conventional tools of this kind, since each slip is
effectively made into two separate toothed surfaces. See FIG. 9.
Having more points of contact with the casing is desirable to
reduce the likelihood of deforming the casing during the setting
procedure. Since each slip is effectively cut in half and made
narrower than normal, the longer length increases the surface area
of the contact points.
[0047] While the embodiment of the invention shown in the figures
is a mechanically set tubing anchor catcher, other embodiments may
be devised without departing from the basic scope of the invention.
Such other embodiments would use the features of the invention in a
hydraulically set tubing anchor catcher, as well as in a different
tool which mechanically or hydraulically sets in a well, such as a
packer or plug. The inventors also envision that the invention may
be used in a well without a restriction, since the tool has a
larger inner diameter than is usually possible in a tool with a
given outer diameter.
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