Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SEALING ASSEMBLY FOR ROTARY OIL PUMPS
AND METHOD OF USING SAME
FIELD OF THE INVENTION
This invention relates generally to the oil production industry, and has to do
particularly with improving the efficiency of the seals used to seal a rotary rod of a
progressive g~ty oil well pump, in order to prevent leakage of oil.
BACKGROUND OF THE INVENTION
Many conventional oil wells are operated by a downhole pump at or close to
the bottom of the well, the pump being of a conventional reciprocating kind actuated
by a rod string which in turn is reciprocated vertically by a pump jack. Recently,
many conventional reciprocating pumps have been replaced by rotary-drive
progressive cavity pumps. The rotary pumps are particularly suited for the
production of crude oil laden with sand and water.
In the conventional vertically reciprocating pumps, the apparatus is typically
constructed in such a way that a single stuffing box provides control of leakage and
loss of oil. This conventional stuffing box is stationary and is secured to a
stationary housing. The part of the upper portion of the rod which actually contacts
the stuffing is usually highly polished, thus ensuring minim~l leakage and minim~l
damage to the packing material. With the introduction of rotary pumps, it has been
generally found that, if the conventional stuffing box (developed for vertical pumps)
is used for the rotary pumps, oil leakage develops relatively early, requiring
frequent mailllenallce and frequent replacement of the packing material.
Prior Art
The following provide a general survey of the background art:
U.S. patent No. 2,471,198, issued on May 24, 1949 to D. R. Cormany;
U.S. patent No. 3,891,031, issued on June 24, 1975 to Ortiz;
U.S. patent No. 4,087,211, issued on May 2, 1978 to Pochyly;
U.S. patent No. 4,089,624, issued on May 16, 1978 to Nichols et al;
U.S. patent No. 4,314,611, issued on February 9, 1982 to Willis;
U.S. patent No. 4,372,379, issued on February 8, 1983 to Klllh~n~k et al.
SUMMARY OF THIS INVENTION
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Broadly stated, the present invention provides an improved assembly for
restraining oil leakage from rotary oil well pumps by providing a special sleeve to
surround the rod with packing, the sleeve rotating with the rod and therefore not
requiring a dynamic seal between them. The sleeve in turn is rotatably mounted
within a recess defined by a stationary member, and a plurality of annular seal
cartridges are provided to occupy the space between the sleeve and the stationary
member. The seal cartridges are constructed in such a way as to resist the leakage
of oil on a sequential basis. Thus, oil must first get past an initial seal cartridge
before gaining access to the second in line, and the second cartridge must breakdown before the oil gains access to the third cartridge. Leak passages
corresponding to the plurality of seal cartridges indicate by the appearance of oil the
furthest dowl~,Lrealll cartridge to which the oil has gained access.
More particularly, this invention provides, for use with a rotary pump for oil
wells in which an elongate rod supports and rotates the rotor of a down-hole pump,
an assembly for restraining oil leakage, comprising:
-- a stationary first member defining a through-bore for the rod and
further defining a substantially cylindrical recess coaxial with said bore, the
cylindrical recess being defined by a cylindrical wall, the first member having an
external wall,
-- a rotary second member also defining a through-bore, the rod
extending through the through-bore of the second member and rotating therewith,
the second member having a substantially cylindrical portion received coaxially in
said recess, the cylindrical portion being defined by an outer cylindrical surface
which has a smaller ~ m~ter than the recess so as to leave an annular space between
them, the annular space having an upstream end where oil under pressure seeks toenter the space, and a downstream end opposite the upstream end,
-- a plurality of annular seal cartridges stacked within said annular
space, each cartridge having, in axial section:
a) a dynamic seal slidably contacting said cylindrical portion,
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b) a first open space downstream of the dynamic seal and adjacent the
cylindrical portion, and a second open space adjacent the cylindrical
wall, and
c) passageway means through which the two spaces are in co~ lunication,
-- for each seal cartridge a leak passage through the first member, the
leak passage comml-nicating the respective open spaces with said external wall, and
-- plug means for closing at least one of the passages.
Additionally, this invention provides a method for restraining oil leakage in a
pump for oil wells in which an elongate rod supports and rotates the rotor of a
down-hole pump, utili~ing an assembly including a stationary first member defining
a through bore for the rod and further defining a substantially cylindrical recess
coaxial with said bore, the cylindrical recess being defined by a cylindrical wall, the
first member having an external wall, a rotary second member also defining a
through- bore, the rod extending through the through-bore of the second member
and rotating therewith, the second member having a substantially cylindrical portion
received coaxially in said recess, the cylindrical portion being defined by an outer
cylindrical surface with a smaller ~ m~ter than the recess so as to leave an annular
space between them, the annular space having an upstream end where oil under
pressure seeks to enter the space, and a dowl~llealll end opposite the upstream end;
said method comprising the steps:
a) providing a plurality of stacked annular seal cartridges within said
annular space, each cartridge having, in axial section: a dynamic seal in
sliding contact with said cylindrical portion, a first open space
downstream of said dynamic seal and adjacent the cylindrical portion, a
second open space adjacent the cylindrical wall, and passageway means
through which the two spaces are in co~ nication,
b) providing, for each seal cartridge, a leak passage through the first
member, each leak passage collllllunicating the respective open spaces
with said external wall,
c) injecting a lubricant through the leak passage of the furthest upstream
seal cartridge and then plugging that leak passage, while
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leaving open the leak passage of a seal cartridge downstream of the
furthest upstream cartridge,
d) monitoring the left-open leak passage for leaking oil, and
e) when such leaking oil is detected, .shlltting down the pump and replacing
S at least those seal cartridges past which oil has leaked.
GENERAL DESCRIPTION OF THE DRAWINGS
One embodiment of this invention is illustrated in the accompanying
drawings, in which like numerals denote like parts throughout the several views,and in which:
Figure 1 is an axial sectional view through an apparatus used at the wellhead
of a downhole rotary pump for supporting and rotating the rod, and for restraining
leakage of oil from the well to the environment;
Figure 2 is a view similar to that of Figure 1, showing a slightly simplified
version;
Figure 3 is an axial sectional view through the portion of the apparatus
where the dynamic rotary seals are located;
Figure 4 is an axial sectional view, to a larger scale, through a seal cartridgefor use with this invention; and
Figure 5 is a partial, exploded, axial sectional view through a portion of the
apparatus where the packing is located.
DETAILED DESCRIPTION OF THE DRAWINGS
Attention is first directed to Figure 1, which shows, in axial section, an
elongate rod 10 which supports and rotates the rotor of a downhole pump (not
illustrated). In Figure 1 the upper end is to the right, and the lower end is to the
left.
At its top end (to the right in Figure 1), the rod 10 has an external thread 12
which engages a nut member 14 at one end of a threaded bore 16 in the nut member14, the other end of the bore 16 being engaged by the threaded end of a lift rod 18.
At its lower (leftward) end, the nut member 14 has a non-circular
protuberance 20 which is engaged by a non-circular, hollow tail bar 22 of which the
other end engages a similar protuberance 24 on a further nut member 26.
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The nut member 26 defines an internally threaded blind bore 28 adapted to
be secured to the upper, threaded end 30 of a packing member 32. It will be
noted that the packing member 32 and the nut member 26 together define a
through-bore 34 through which the rod 10 passes. The packing member 32
defines at its upper end (to the right in Figure 1) an annular packing cavity 36containing conventional packing 38. An annular closure member 40 compresses
the p~,king 38, and is pushed downwardly by the tightening of the nut member
26. The closure member 40 can be sçlec,tçd to be of different axial dim~n~ions, so
as to provide the right degree of compression on the packing 38 when the nut
member 26 has been screwed down as far as possible on the packing member 32.
The packing member 32 has a reduced portion 42 which surrounds the rod
10 and which has an external thread adapted to fit into an internally threaded,
cylindrical recess 44 defined at the top (rightward end) of a sleeve member 46, the
latter having a through-bore 48 for receiving the rod 10.
The sleeve member 46 is constructed in such a way as to receive a radial
bearing 50 and a thrust bearing 52, which support the sleeve member 46 for
rotation with respect to a frame member 54 which is solidly connected to the
wellhead housing by means which are not shown and which do not play any part
in the present invention.
In the assembly of Figure 1, a pinion gear 56 is locked for rotation with
the sleeve member 46 by a key 58. Means not illustrated are provided for rotating
the gear 56, along with the sleeve member 46.
Bolted to the underside (the left side in the drawing) of the frame 54 is a
stationary first member 60 which defines a through bore 62 for the rod 10 and isin turn bolted or otherwise f~tened to a T-member 64 which forms no part of the
present invention. .. .
As can be seen in Figure 1, the stationary first member 60 further defines a
subst~nti~lly cylindrical recess 66 which is coaxial with the through-bore 62 and
which is primarily defined by a cylindrical wall 68. The first member 60 furtherhas an external wall 70, which reduces through a frusto-conical transition 72 to a
throat portion 74. The first member 60 further has a lower flange 76 for
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securement ~o the T-member 64, and an upper flange 78 for securement to the
frame member 54.
Attention is now directed to Figures 3 and 4, for a more detailed
- description of the contents of the cylindrical recess 66.
As particularly seen in Figure 3, the sleeve member 46 has an integral tail
portion 80, to be referred to hereinafter as a cylindrical portion, and the
cylindrical portion 80 is received coaxially in the recess 66. The cylindrical
portion 80 has an outer cylindrical surface which has a smaller diameter than the
cylindrical recess 66, so as to leave an annular space 84 between them. The
annular space 84 has an upstream end 86 where oil under pressure (arriving the
through-bore 62) seeks to enter the annular space 84, and a downstream end 88
opposite the upstream end 86.
T ~,~ted within the cylindrical recess 66 (annular space 84) are three
annular seal cartridges 90 which are stacked one behind the other in the annularspace 84.
As can be seen by comparing Figure 3 and 4, each cartridge has, in axial
section:
(a) a knife-edge corner 92 which slidably contacts the cylindrical portion 80,
(b) a first open space 94 downstream (rightward) from the knife-edge corner
92 and ~dj~cent the cylindrical portion 80, and a second open space 96
adjacent the cylindrical wall 68. Passageway means 97 (preferably in the
form of spaced-apart passageways drilled radially into each cartridge)
provide communication between the first open space 94 and the second
open space 96.
Each seal cartridge 90 further defines an inwardly open groove 98
downstream of the first open space 94, with a resilient ring 100 in the groove 98.
The resilient ring is adapted to be conl~ssed by the freezing and expansion of
any water within the open spaces 94 and 96.
Each seal cartridge 90 further includes a support surface 102 subst~nti~lly
parallel with the outer cylindrical surface 82, and located downstream of the
groove 98. Also provided is an O-ring seal element 104 which is generally U-
shaped in radial section, and which includes two arms 106 and 108, of which the
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arm 106 is adapted to lie against the outer cylindrical surface 82, and of whicharm 108 is adapted to lie against the support surface 102, in such a way that the
interior of the U-shape is open downwardly (leftwardly) toward the first open
space 94. This is clearly seen in Figure 4.
The O-ring seal element 104 further has an outwardly projecting integral
flange 110 which lies within a flange recess 112 defined by the seal cartridge 90,
and arranged such that the flange l lO is co.,.plcssed and gripped between the
respective cartridge and the next adjacent cartridge. This is best seen in Figure 3.
It is also to be noted that the first member 60 provides, for each seal
cartridge 90, a leak passage 114, each leak passage 114 communicating the open
spaces (of the respective seal cartridge 90) with the external wall 70. An
externally threaded plug 116 is provided for closing at least one of the passages.
It will be noted that the annular space 84 defined between the cylindrical
wall 68 and the cylindrical surface 82 is closed at its upstream (leftward) end by
an annular wall 120, and that the lowermost (furthest leftward) seal cartridge 90
abuts the wall 120.
Each seal cartridge 90 has an outer peripheral recess 122 (see Figure 4)
adjacent the cylindrical wall 68 of the member 60, and an O-ring seal 124 withinthe peripheral recess 122.
Figure 3 shows the provision of lock means urging the annular seal
cartridges 90 downwardly (leftwardly) against the annular wall 120.
More specifi~lly, the lock means includes two annular members 126 and
128, along with a circlip lodged in a collc~ponding groove in the cylindrical wall
68.
Attentioll is now directed briefly to Figure 5, which shows a version of the
p~king member 32 having slightly different ~im~n~ional characteristics from thatshown in Figure 1. However, all the main coml)onents are present in Figure 5,
and in addition there is shown an O-ring 130 received in a collcsponding recess,the O-ring 130 being colllpressed against the corner portion 132 of the sleeve
member 46'. This ensures that no leakage will occur at the joint between the
pa~l~in~ member 32 and the sleeve member 46.
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Figure 2 illustrates a variant of the assembly shown in Figure l. In Figure
2, the frame member 54 is absent, as is the pinion gear 56 and the mounting
bearings. In the arrangement of Figure 2, a different means (not shown) would berequired for rotating the sleeve member 46'.
Another difference in Figure 2 is the provision of a lift ring 132 instead of
the nut member 14 in Figure 1. The lift ring 132 has a threaded bore 134 with
which the upper, externally threaded end of the rod 10 can be engaged.
Aside from the mentioned differences, all of the other parts are identical as
between Figures 1 and 2. Below is described a method for ~Itili7ing the apparatus
just described, in restraining oil leakage in a pump for oil wells, in which an
elongate rod supports and rotates the rotor of a down-hole pump.
The method involves, firstly, providing all of the components illustrated in
the figures and described previously, including the provision of a plurality of
stacked annular seal cartridges 90 with the described configuration, and providing,
for each seal cartridge 90, a leak passage 114 through the first member 60, eachleak passage 114 communicating the respective open spaces (94, 96) with the
external wall 70.
In one mode of utilizations, prior to the initiation of pumping, a lubricant
such as grease or heavy oil is injected through the leak passage of the furthestupstream (furthest leftward in Figures 1 and 2) seal cartridge 90, and then thatleak passage is plugged, while leaving open the leak passage of the seal cartridge
next downstream of the furthest upstream cartridge. Utilizing three cartridges as
illustrated in the figures, we can speak of an upstream cartridge, a downstream
cartridge, and an intermediate cartridge. Thus, the lubricant is injected into the
Llp~llealll cartridge, and the collespol1ding leak passage is plugged and sealed.
The leak passage for the intell~,e~i~te cartridge, however, is left open. In this
particular mode of operation, the third leak passage (that for the downstream
cartridge) can be closed with a plug of the kind shown at 116 in Figure 3.
Pumping is then initi~ted, and the operator monitors the intermP~i~te leak
passage for leaking oil. When leaking oil is detected at the leak passage for the
interme~ tP~ cartridge, this .signifies that oil has got past the knife-edge 92 of both
the U~S~ and the intermedi~tP, cartridges. At this point, the opeldtor may
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decide to shut down the pumping operation, and replace at least the upstream andinterme~ e cartridges (which can no longer withstand the oil pressure).
Alternatively, the operator can remove the plug from the downstream leak passageand use it to plug up the leak passage for the intermediate cartridge. This willS shift attention to the third cartridge. When oil appears at the open leak passage of
the third cartridge, this will signify that the oil has now got past the knife-edge
seal 92 of all three cartridges. At this point, the opeMtion should be shut downand all seal cartridges should be replaced.
While several variants of this invention have been illustrated in the
10 accompanying drawings and described hereinabove, it will be evident to those
skilled in the art that changes and modifications may be made therein without
departing from the essence of this invention, as set forth in the appended claims.
