Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
[0001] Slip Joint for Downhole Tubing
FIELD
[0002] This relates to a slip joint for a downhole tubing string that
allows the downhole
tubing to be moved relative to a stationary tubing section.
BACKGROUND
[0003] As pumps are used downhole to produce wellbore fluids, the pump
and its
components, such as a sucker rod, move through repetitive, reciprocal or
rotary motions. This
can cause wear in the tubing in which they are placed, and may result in a
hole in the tubing.
Tubing must be serviced regularly to repair or replace any sections of tubing
that are
damaged.
SUMMARY
[0004] There is provided a movable downhole tubing string that has a
stationary tubing
section and a movable tubing section telescopically received within the
stationary tubing
section. The stationary tubing section is positioned at a pump end of the
tubing string and the
movable tubing section extends toward a surface end of the tubing string from
the stationary
tubing section. An actuator is provided for telescopically moving the movable
tubing section
relative to the stationary tubing section between an extended position and a
retracted position
or between a retracted position and an extended position.
[0005] In an aspect, a rotator is provided that rotates the movable
tubing section as it
moves between the extended position and the retracted position.
[0006] In an aspect, the rotator has a sleeve that has a position that is
fixed relative to the
stationary tubing section. The sleeve has at least one groove that defines a
spiral and each of
the grooves is engaged by a pin that is carried by the movable tubing section.
The pin travels
along the groove as the movable tubing section moves between the retracted
position and the
extended position.
[0007] In an aspect, the actuator is a hydraulic actuator or a mechanical
actuator.
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[0008] In an aspect, the actuator is a hydraulic actuator and the tubing
string has a piston
mounted at an upper end of the movable tubing section.
[0009] In an aspect, the stationary tubing section has a pump attachment
and the movable
tubing section extends to the surface.
[0010] In an aspect, the tubing string also has a second stationary
tubing section that is
positioned at the surface end of the tubing string. The movable tubing section
is telescopically
received within the second stationary tubing section.
[0011] There is provided, in combination, a movable downhole tubing
string, a downhoe
pump, a wellhead and a pump drive string. The movable downhole tubing string
has a
stationary tubing section and a movable tubing section telescopically received
within the
stationary tubing section. The stationary tubing section is positioned at a
pump end of the
tubing string and the movable tubing section extends toward a surface end of
the tubing string
from the stationary tubing section. An actuator is provided for telescopically
moving the
movable tubing section relative to the stationary tubing section between an
extended position
and a retracted position or between a retracted position and an extended
position. The
downhole pump is secured to the stationary tubing section of tubing and the
surface end of the
tubing string is telescopically attached to the wellhead. The pump drive
string extends through
the tubing string and is attached to drive the downhole pump.
[0012] There is provided a method of operating a downhole pump. A tubing
string with a
stationary tubing section and a movable tubing section telescopically received
within the
stationary tubing section is provided. A downhole pump is attached to the
stationary tubing
section of the tubing string and a pump drive string is attached to the
downhole pump. The
tubing string is inserted into a producing wellbore and the pump is driven
using the pump
drive string. The movable tubing section of the tubing string is
telescopically moved relative
to the stationary tubing section between an extended position and a retracted
position or
between a retracted position and an extended position to distribute the wear
on the movable
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tubing section incurred by the pump drive string along the movable tubing
string.
[0013] In an aspect, the method also includes rotating the movable tubing
section as it
moves between the extended position and the retracted position.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] These and other features will become more apparent from the
following
description in which reference is made to the appended drawings, the drawings
are for the
purpose of illustration only and are not intended to be in any way limiting,
wherein:
FIG. 1 is a side elevation schematic view of a slip joint for downhole tubing.
FIG. 2 is a side elevation view in section of a tubing string in a retracted
position.
FIG. 3 is a side elevation view in section of a tubing string in an extended
position.
FIG. 4 is a side elevation view in section of a rotator sleeve.
DETAILED DESCRIPTION
[0015] Referring to FIG. 1, there is shown a movable downhole tubing
string, generally
indicated by reference numeral 10, which includes a stationary tubing section
12 and a
movable tubing section 14 that is telescopically received within stationary
tubing section 12.
Stationary tubing section 12 is positioned at a pump end 16 of tubing string
10 and movable
tubing section 14 extends toward a surface end 18 of tubing string 10 from
stationary tubing
section 12. The various sections of tubing that are described herein may be
any length.
However, the sections are more likely to be approximately 30 ft, as this is
the common length
used for tubular members. It will also be understood that the various
components may not be
the same length. However, it is preferred that the movement cover an entire
length of a
section of tubing, for reasons that will be apparent from the discussion
below.
[0016] Stationary tubing section 12 is designed to be attached to a pump
20. This
attachment may be done in various ways, depending on the type of pump being
used, as will
be recognized by those skilled in the art. Stationary tubing section 12 may be
anchored to the
wellbore directly, or pump 20 may be anchored downhole to ensure stationary
tubing section
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12 remains stationary. A pump drive string 19, such as a sucker rod string,
extends from
surface down through movable tubing section 14 and stationary tubing section
12 to engage
and drive pump 20. Pump 20 may be a rotary pump or a reciprocating pump, as
will be
known in the art.
[0017] Referring to FIG. 2, movable tubing section 14 is preferably made
up of sections
of tubing string that are commonly used in the industry. The main differences
between
movable tubing section 14 and a traditional tubing string will be found at the
pump end 16
and the surface end 18, as will be described below.
[0018] Referring again to FIG. 1, there is also an actuator 22 that
telescopically moves
movable tubing section 14 relative to stationary tubing section 12. In the
example described
below, the movement of movable tubing section 14 will be from a retracted
position to an
extended position relative to stationary tubing section 12. However, it will
be understood that
the movement could also be from an extended position to a retracted position.
Referring to
FIG. 2, seals 21 are provided between movable tubing section 14 and stationary
tubing
section 12, however these are intended primarily to prevent debris and
unwanted material
from entering the mechanism while movable tubing section 14 is kept
stationary. As will be
understood, it is necessary for any fluid between these seals to escape, or
for fluid to be drawn
in, as the components move, and either seals 21 must be designed accordingly
or another
egress must be provided. In one example, the space between movable tubing
section 14 and
stationary tubing section 12 may be filled with hydraulic oil prior to
installation. As movable
tubing section 14 is moved upward relative to stationary tubing section 12,
the hydraulic oil is
pushed out through seals 21, which helps lubricate the movement.
[0019] Referring to FIG. 2, actuator 22 may be a hydraulic actuator. In
the depicted
example, movable tubing section 14 includes a piston 24 that is received
within a second
stationary tubing section 26, and sealed together by seals 28. A hydraulic
line 32
communicates hydraulic fluid below piston 24, causing it to move upward and
lift movable
tubing section 14. It will be understood that, if movable tubing section 14 is
designed to
move downward instead, the hydraulic force must be adjusted accordingly. If
the weight of
movable tubing section 14 is sufficient, it may be sufficient to remove
hydraulic fluid from
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below piston 24 and allow it to descend based on gravity alone. Otherwise, it
may be
necessary to push downward on piston 24.
[0020] In other examples, other types of actuators 22 may also be used.
For example,
5 actuator 22 may be mechanically driven, such as by gears or cables as
will be recognized by
those skilled in the art. Furthermore, it may be convenient to incorporate
second stationary
tubing section 26 into a wellhead.
[0021] Referring now to FIG. 2 and 3, tubing string 10 may have a rotator
30 that causes
movable tubing section 14 to rotate as it is being raised. As depicted,
rotator 30 is a section of
tubing that rotates the movable tubing section as it is moves between the
extended position
and the retracted position.
[0022] The depicted rotator 30 is made up of a sleeve 34 that is attached
to second
stationary tubing section 26 and is stationary as movable portion 14 is
received within sleeve
14. The actual position of rotator sleeve 34 may be varied, provided that it
is fixed relative to
stationary tubing section 12. Referring to FIG. 4, sleeve 34 has grooves 36
along an inner
surface 38 that define a spiral. In one example, two grooves that are offset
by 180 degrees
may be used, although there may be one or more than two grooves. Referring to
FIG. 2 and
3, pins 40 mounted to movable tubing section 14 engage grooves 36. As movable
tubing
section 14 is moved up or down, pins 40 travel along grooves 36 and apply a
rotary force to
movable tubing section 14, causing it to rotate. It will be understood that
other types of
rotators may also be used.
[0023] Once installed, pump 20 is driven as is known in the art. Pump 20 is
driven by
either rotating or reciprocating drive string 19. As this occurs, drive string
19 will create wear
on the inside of tubing string 10. In order to delay replacement or repair of
tubing string 10,
actuator 22 may be actuated to cause movable tubing section 14 to move
relative to stationary
tubing section 12. As movable tubing section 14 moves telescopically and
rotationally, the
wear due to either a rotating string 19, which is generally localized at one
position along
tubing string 10, and a reciprocating string 19, which is generally localized
at one radial
position of tubing string 10, is distributed, thus increasing the useful life
of tubing string 10, or
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the time between servicing.
[0024] In this patent document, the word "comprising" is used in its non-
limiting sense to
mean that items following the word are included, but items not specifically
mentioned are not
excluded. A reference to an element by the indefinite article "a" does not
exclude the
possibility that more than one of the element is present, unless the context
clearly requires that
there be one and only one of the elements.
[0025] The following claims are to be understood to include what is
specifically illustrated
and described above, what is conceptually equivalent, and what can be
obviously substituted.
The scope of the claims should not be limited by the preferred embodiments set
forth in the
examples, but should be given the broadest interpretation consistent with the
description as a
whole.
