Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02778018 2012-05-29
POLISHED ROD WITH LATCHING SECTION
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The inventive concepts disclosed herein generally relate to sucker
rod strings for producing oil and gas, and more particularly, but not by way
of
limitation, to a polished rod having a latching section near the upper end of
the
polished rod with a reduced diameter on which a rod elevator can be attached
2. Brief Description of Related Art
[0002] In the production of hydrocarbons from subsurface formations, it is
common to use a sucker rod to lift fluids to the surface. Typical sucker rod
pumps include a string of sucker rods extending from the earth's surface down
to
a downhole pump. A pump jack located on the surface is employed to
reciprocate the sucker rod string and thus the downhole pump. The pump jack
typically is a beam that pivots in a vertical plane and which is provided with
a
horse head at one end. The horse head supports a pair of bridle cables and a
carrier bar.
[0003] A polished rod is suspended from the carrier bar and extended
through a stuffing box. The lower end of the polished rod is attached to the
upper
end of the sucker rod string. The polished rod has a polished exterior surface
to
serves to form a seal with the stuffing box and thus force formation fluid
that is
lifted to the earth's surface to flow from production tubing to a collection
conduit
by which the produced fluid is conveyed to a tank battery, pipeline or other
system whereby the produced fluid is collected.
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[0004] The sucker rod string is formed of a series of individual sucker rods
which are connected to one another in an end-to-end fashion so as to work
together to lift the fluid from the ground. At times, the need arises to
service the
well or replace or maintenance the downhole pump. To do so requires the
sucker rod string be removed from the well.
[0005] Removal of the sucker rod string starts with the removal of the
polished rod. Because polished rods are manufactured with a smooth, polished
shaft having a uniform diameter, a pony rod is typically attached to the upper
end
of the polished rod to provide a location at which an elevator can be
attached.
Pony rods are provided with a recessed section consisting of a smaller
diameter
than the diameter at its ends. This recessed section allows the rod elevator
to be
attached to the pony rod so that the rod string can be lifted from the well.
[0006] After the polished rod is lifted and detached from the sucker rod
string, the remaining sucker rods in the rod string are removed without the
assistance of a pony rod because the sucker rods have a latching area for the
rod elevator. Thus, only the polished rod requires the use of the pony rod to
facilitate its removal from the rod string.
[0007] While the use of pony rods has long been accepted in the
petroleum industry, many inefficiencies are encountered in the use of pony
rods.
For example, because polished rods are manufactured in a variety of sizes,
those servicing wells must maintain an inventory of a variety of sizes of pony
rods, thereby increasing costs. More critical, however, is the fact that the
steps
required to install a pony rod on a polished rod places services personnel in
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precarious positions above the well and thus exposes the service personnel to
severe injury.
[0008] Therefore, a need exists for an improved polished rod that includes
an integral latching section near an upper end to provide a latching area. It
is to
such an improved polished rod that the inventive concepts disclosed herein are
directed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is an elevation view of a prior art pumping unit.
[0010] FIG. 2 is an elevation view of the prior art pumping unit of FIG. 1
illustrating a pony rod attached to a polished rod.
[0011] FIG. 3 is an elevation view of the prior art polished rod.
[0012] FIG. 4 is an elevation view of a polished rod constructed in
accordance with the inventive concepts disclosed herein.
[0013] FIG. 5 is an elevation view of polished rod of FIG. 4 shown
suspended from a rod elevator.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0014] Before explaining at least one embodiment of the presently
disclosed and claimed inventive concepts in detail, it is to be understood
that the
presently disclosed and claimed inventive concepts are not limited in their
application to the details of construction, experiments, exemplary data,
and/or the
arrangement of the components set forth in the following description or
illustrated
in the drawings. The presently disclosed and claimed inventive concepts are
capable of other embodiments or of being practiced or carried out in various
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ways. Also, it is to be understood that the phraseology and terminology
employed herein is for purpose of description and should not be regarded as
limiting.
[0015] Referring now to the drawings, and in particular FIG. 1, one version
of a conventional beam pumping unit 10 is illustrated. The pumping unit 10
includes a pump jack 12 that drives a downhole reciprocating pump (not shown)
located in a wellbore 14. The pump jack 12 has a walking beam 16 with a horse
head 18 located at one end. Activation of a primary mover 20 causes the horse
head 18 to deliver a reciprocal pumping stroke to the downhole pump. A carrier
bar 22 is suspended from bridle cables 24a and 24b which roll tangentially
over
the horse head 18 as it reciprocates. A string of sucker rods 26 is suspended
from the carrier bar 22, and the sucker rod string 26 extends down production
tubing 28 to drive the pump.
[0016] A polished rod 30 is connected to the top of the sucker rod string
26. The polished rod 30 extends through a stuffing box 32 and through the
carrier
bar 22. A rod clamp 34 is secured to the polish rod 30 above the carrier bar
22 to
support the sucker rod string 26 while the weight is carried by the bridle
cables
24a and 24b and the carrier bar 22.
[0017] Referring now to FIG. 2, one version of a prior art pony rod 36 is
shown connected to the upper end of the polished rod 30 with a coupler 38. The
pony rod 36 includes a recessed section 40. A rod elevator 41 which is
supported by a rod hook 42 is shown latched to pony rod 36 at the recessed
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section 40 of the pony rod 36. The rod hook 42 is connected to an external
hoist
(not shown).
[0018] The prior art polished rod 30 is best shown in FIG. 3 as including
shank 43 with a threaded upper pin connector 44, and a threaded lower pin
connector 46. The shank 43 has a uniform diameter and a polished surface 48
which travels slidably through the stuffing box 32 (FIG. 1) such that a
hydraulic
seal is maintained.
[0019] As discussed above, removal of the sucker rod string 26 from the
well bore 14 entails disconnecting the carrier bar 22 and the rod clamp 34
from
the polished rod 30 and attaching the pony rod 36 to the upper end of the
polished rod 30 to allow the rod elevator 42 to be latched to the sucker rod
string
26 and the external hoist (not shown) to be used to lift the sucker rod string
26
from the wellbore 14 so that the polished rod 30 may be disconnected from the
remainder of the sucker rod string 26. As will be appreciated, the process of
attaching a typical pony rod to sucker rod string prior to removal of the
sucker rod
string from a wellbore s cumbersome and inefficient. In addition, because the
upper end of the polished rod often extends a considerable height above the
stuffing box, personnel are exposed to hazardous conditions during the process
of installing a pony rod.
[0020] Referring now to FIG. 4, one embodiment of a polished rod 50
constructed in accordance with the inventive concepts disclosed herein is
illustrated. The polished rod 50 includes a unitary or one piece shank 52
having
an upper end 54 and a lower end 56. The shank 52 may be formed of a variety of
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materials, such as steel and steel alloy. The upper end 54 and the lower end
56
each have a diameter. A first connector 58 is formed on the upper end 54 of
the
shank 52, and a second connector 60 is formed on the lower end 56 of the shank
42. In one embodiment, the first and second connectors 58 and 60 may be in the
form of threaded rod pin connectors. However, it should be appreciated that
the
connectors may be in a variety of forms.
[0021] The shank 52 further includes at least one sealing section 62 and a
latching section 64. The sealing section 62 extends from the lower end 56 of
the
shank 62 towards the upper end 54 of the shank 52, and the latching section 64
is formed between the sealing section 62 and the upper end 54 of the shank 52.
It will be appreciated, however, that the shank 52 may be formed to include a
latching section on both the lower end 56 and the upper end 54.
[0022] The sealing section 62 is configured to travel slidably through the
stuffing box such that a hydraulic seal is maintained. To this end, the
sealing
section 62 has a polished surface 66 and a uniform diameter which is
substantially equal to the diameter of the upper end 54 and the lower end 56
of
the shaft 52. In one embodiment, the polished surface 66 has a surface finish
in
a range of about 8 pin. to about 32 pin. However, it will be appreciated that
a
variety of surface finishes may be utilized. In addition, it will be
appreciated that
the length and diameter of the sealing section 62 may be varied, but typically
the
length will be in a range of eight feet to forty feet. Finally, it will be
appreciated by
those of ordinary skill in the art that a polished rod liner (not shown) may
be
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secured about the sealing section 62 whereby the polished rod liner forms the
hydraulic seal with the stuffing box.
[0023] The latching section 64 of the shank 52 is characterized as having
a diameter less than the diameter of the sealing section 62 and the upper end
54
so as to define a recessed area on the polished rod 50 on which a rod elevator
may latch. In one embodiment, the length of the latching section 64 is less
than
the length of the sealing section 62, and the latching section 62 has a
generally
cylindrical cross-section to permit latching of a rod elevator to the latching
section
62.
[0024] In use, the polished rod 50 is connected to the upper end of the
sucker rod string 26 in a manner similar to that described above in relation
to the
polished rod 30. The polished rod 50 extends through the stuffing box 32 and
through the carrier bar 22. The rod clamp 34 is secured to a selected location
on
the sealing section 62 of the shank 52 above the carrier bar 22 to support the
sucker rod string 26 while the weight is carried by the bridle cables 24a and
24b
and the carrier bar 22.
[0025] With reference to FIG. 5, removal of the sucker rod string 26 simply
requires disconnecting the carrier bar 22 and the rod clamp 34 from the
polished
rod 30 and attaching the rod elevator 41, which is connected to the rod hook
42
and the external hoist (not shown), to the latching section 64 of the shank 52
Due to the presence of the polished rod 50, the rod elevator 41 attaches
directly
to the polished rod 50 rather than to a pony rod that must first be installed.
Thus,
employment of the polished rod 50 eliminates the need to insert the pony rod
26
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into the sucker rod string before the polished rod 50 and the sucker rod
string 26
are lifted from the wellbore 12.
[0026] From the above description, it is clear that the present inventive
concept is well adapted to carry out the objects and to attain the advantages
mentioned herein as well as those inherent in the invention. While exemplary
embodiments of the invention have been described for purposes of this
disclosure, it will be understood that numerous changes may be made which will
readily suggest themselves to those skilled in the art and which are
accomplished within the spirit of the inventive concept disclosed and claimed
herein.
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