Note: Descriptions are shown in the official language in which they were submitted.
CA 02239715 1998-06-OS
TEM File No. 207.1
TITLE: ANCHORING DEVICE
FIELD OF THE INVENTION
The present invention relates to devices for anchoring and catching well
equipment
within a well conduit, and in particular devices for anchoring well equipment
within the
well in both directions longitudinally and in one rotational direction.
BACKGROUND OF THE INVENTION
Various types of devices for anchoring and catching well equipment are known
which use either a right hand thread, a left hand thread, or both. These
threaded types of
anchoring devices suffer from several drawbacks, one being that such threaded
components tend to seize or jam during operations, particularly during
emergency release
operations, and stop pins are susceptible to breakage during use. Jammed
anchoring
devices are difficult to dislodge, resulting in time delays, lost productivity
and increased
operating costs. Jammed anchoring devices can also cause significant damage to
well
equipment, including conduits and casings. Threaded anchoring devices are also
expensive to manufacture.
Solutions to at least some of the above-noted problems have been proposed by
the
present applicant in co-pending Canadian Patent Application no. 2,160,647,
which
describes a helical bearing and associated helical groove. The present
invention, however,
provides an improved groove of shorter distance and altered configuration
which further
overcomes the limitations and disadvantage of prior art devices, as will
become apparent
-1-
CA 02239715 1998-06-OS
in the description. In particular, only about a quarter turn is required to
set and unset the
teeth of the present anchoring device whereas three or more turns are needed
for prior
anchors. Multiple turns are not merely inconvenient but are undesireable in
soft, sandy-
type formations (e.g. oil sands) where it could be difficult to determine
whether the
multiple turns are unsetting the anchoring device or undoing the tubing
threads.
DESCRIPTION OF THE DRAWINGS
Embodiments of the invention will now be described, by way of example only,
with
reference to the accompanying drawings, wherein:
Figure 1 is an elevated side view of an anchoring device according to a
preferred
embodiment of the present invention within a well conduit shown in cross-
section;
Figure 2 is a sectional view along line 2-2 of fig. l, showing the anchoring
device in
an unset position within the well conduit;
Figure 3 is a view similar to fig.2 but with the anchoring device in a set
position;
Figure 4 is a perspective view of a mandrel of the anchoring device of fig.l
showing an improved bearing and groove arrangement according to the present
invention;
Figure 4a is a detailed view of the bearing of fig.4;
Figure Sa is a sectional view along line Sa~Sa of fig.2;
Figure Sb is a sectional view along line Sb-Sb of fig.3; and
Figure 6 is a close-up view in fig:3 of a slip's downwardly facing teeth
engaging
the well conduit.
-2-
CA 02239715 1998-06-OS
DESCRIPTION OF PREFERRED EMBODIMENTS
The anchoring device of the present invention, generally designated by
reference
numeral 10 in the figures, is located inside a well conduit 12 and has well
equipment 14
attached above and below. Referring to figs. l & 2, a slip 16 is shown
positioned within a
generally rectangular opening 21 in slip retainer 20. Typically at least three
slips are
suitably positioned about the anchoring device. Each slip 16 has gripping
teeth 18 for
engaging the inner well conduit wall 32. A feature of the present invention is
shown in
fig.6 in that the teeth 18 are pointed in one direction, namely downwardly
(i.e. away from
the surface of the well) so as to grip the wall 32 during compression of the
anchoring
device, and to reduce or avoid interference and resistance by the slips 16
when removing
the anchoring device, as opposed to teeth on prior slips which point in both
directions. An
upper cap screw 22 is shown contacting a shoulder 24 on the slip retainer 20.
A drag
body 26 can be seen to accommodate a drag means 28 and a friction surface 30
which
contacts the inner well conduit wall 32. The well equipment 14 is shown
attached to a
mandrel 34.
Referring to fig.2, the anchoring device 10 in the well conduit 12 has a cone
element 36 shouldered against the mandrel 34. The cone element 36 has a
conical surface
38, and cone set screws 40 retain the cone element 38 on the mandrel 34. The
drag body
26 accommodates the drag means 28 and has drag springs 42 to urge the drag
means 28
outwardly against the inner well conduit wall 32. The drag means 28
frictionally contacts
the inner well conduit wall 32 to urge the drag body 26 to remain stationary
within the
well conduit while the mandrel 34 rotates within. The upper cap screws 22 are
shown to
contact the slip retainer's shoulder 24 to prevent the slip retainer 20 from
moving upward
and from allowing the slip 16 to contact the 'cone element 36. The upper cap
screw 22
-3-
CA 02239715 1998-06-OS
also prevents the drag body 26 from moving off of the mandrel 34 should pins
44 shear, as
described later. The drag body 26 also has a conical surface 138 which is out
of contact
with the slip 16 in the unset position, as is the cone's conical surface 38.
Upper and lower
retaining rings or sleeves 46 and 48, respectively, keep the drag means 28
from escaping
the anchoring device 10. Lower cap screws 50 attach the lower retaining ring
48 to the
drag body 26, which ring also keeps the pins 44 within the drag body 26.
Referring now to figs. 4 and 4a as well; a bearing 52 accommodates the pins 44
within a hole 54. According to an important aspect of the present invention
the helical
bearing 52 is generally cylindrical in shape for ease of maneuverability
within an elongate
groove 56 which accommodates the bearing 52. The bearing 52 slides along the
groove
56, and may be made to roll within the groove if desired. The groove 56, which
may be
termed a helical groove since it extends about a portion of the cylindrical
surface of the
mandrel 34, appears in fig. 4 as an inverted "7". The helical groove 56 has a
transverse or
"horizontal" portion 56a terminating with an enlarged slot 57a, a diagonal
portion 56b
terminating at 57b, and an elbow or setting point 56c intermediate the
transverse and
diagonal portions 56a, 56b.
Figure 3 shows the anchoring device in the set position. In operation, the
anchoring device is brought to the set position by first running the anchoring
device to the
setting depth in the well conduit 12. In the preferred embodiment the well
equipment 14,
including the anchoring device 10, is then lifted a short distance (typically
about 4 inches,
due mostly to tubing stretch from weight of tubing string) and the mandrel 34
is rotated in
a first direction (i.e. to the "left" or counterclockwise in the embodiment
shown) a quarter
turn to move the bearing 52 and pin 44 from the slot 57a to the setting point
56c along the
horizontal portion 56a of the helical groove 56, as indicated by arrow 70 in
fig.4. The
-4-
CA 02239715 1998-06-OS
mandrel 34 is next rotated in a second direction opposite to the first
direction (i.e. to the
"right" or clockwise in the embodiment shown) and dropped down to move the
bearing 52
and pin 44 from the elbow 56c to the end 57b along the groove's helical
transverse portion
56b. During this latter rotation to the right (also about a quarter turn) the
conical surfaces
38 and 138 on the cone element 36 and the drag body 26, respectively, move
toward each
other. The conical surfaces 38, 138 contact the respective concave inner
surfaces 58 and
60 of the slips 16 to drive the slips outwardly. The gripping teeth 18 contact
and bite into
the inner well conduit wall 32 and cease moving. The mandrel 34 and the
attached well
equipment 14 is therefore set, namely they can not move with respect to the
well conduit
12 in a downwardly longitudinal direction, nor any further in the rotational
setting
direction. Figure Sb shows the anchoring device 10 set with the slips 16 in
contact with
the inner well conduit wall 32.
The anchor is unset by reversing the above setting procedure. The mandrel 34
is
rotated about a quarter turn in the first direction (i. e. to the left, or
counterclockwise, in
the instant case) and lifted to move the bearing 52, pin 44 and the drag body
26
downwardly. Hence, the conical surfaces 36 and 136 separate and move away from
the
inner concave surfaces 58 and 60 of the slips 16 to allow the slips to
retract. A spring 62
connected to the backside of each slip 16 urges the slip 16 away from the
inner well
conduit wall 32. The mandrel 34 is then rotated a quarter turn in the second
direction (i.e.
to the right, clockwise) to bring the bearing 52 to the slot 57a which keeps
the bearing in
that location while the anchoring device 10 is moved to a different position
in the well
conduit for resetting or is removed entirely from the well conduit. Figure Sa
shows the
anchoring device 10 unset with the slips 16 retracted from the inner well
conduit wall 32.
-5-
CA 02239715 1998-06-OS
An alternate method of unsetting the anchoring device 10 is to pull upwardly
on
the mandrel 34 until the maximum shear strength of the pins 44 is exceeded.
The pins 44
will therefore shear off of the bearings 52 to allow the mandrel 34 and cone
element 36 to
be lifted. Once the conical surface 38 of the cone element 36 moves away from
the slips
16, the spring 62 urges each slip 16 to retract from the inner well conduit
wall 32.to free
the anchoring device 10 for removal from the well conduit 12. Good results
have been
obtained using three pins 44, each with a maximum shear strength of about 6000
lbs.
Some of the advantages of the present invention may now be better appreciated.
An important advantage over prior threaded designs is that the anchoring
device 10
requires a mere quarter turn in both directions and a pull or push straight up
or down to
either set or unset the catcher within the well conduit 12. Three or more
turns are needed
to set or unset prior threaded anchoring devices which is inconvenient and
particularly
undesireable in soft, sandy-type formations where it may be diWcult to
determine whether
the multiple turns are unsetting the anchoring device or undoing the tubing
threads. The
unidirectional teeth 18 on the slips 16 also help reduce unwanted resistance
when
removing the anchoring device from the well conduit after unsetting.
The above description is intended in an illustrative rather than a restrictive
sense
and variations to the specific configurations described may be apparent to
skilled persons
in adapting the present invention to specific applications. Such variations
are intended to
form part of the present invention insofar as they are within the spirit and
scope of the
claims below. For instance, the incline of the diagonal portion 56b of the
groove 56 may
be altered to address particular design specifications, or the amount of twist
may be
changed from a quarter to, say, a half turn, although this is not preferred.
-6-
