Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02452696 2004-09-16
1 "UNIVERSAL PRESSURE PROTECTOR
2 FOR A POLISH ROD"
3
4 FIELD OF THE INVENTION
The present invention relates to improvements to sealing a polish
6 rod for a well. More particularly, apparatus is provided including a polish
rod seal
7 or is provided in addition to an existing stuffing box for better sealing
the polish
8 rod or for resisting high pressures such as those applied in flushing
operations.
9
BACKGROUND OF THE INVENTION
11 As the oilfield industry develops into the future, a major concern is
12 safeguarding the environment. Oil companies are recognizing that
improvements
13 must be made in the process of extracting oil. This extraction must be
completed
14 with as little harm to the surrounding environment as possible.
As is well known to those in the in the industry, a pump stator, such
16 as the stator of a progressive cavity pump, is located downhole at the end
of
17 production tubing. A pump rotor engages the stator and is suspended from at
a
18 distal end of a rod string. The rod string is driven from surface through a
polish
19 rod connected to a wellhead drive assembly for lifting well fluid to
surface. The
polish rod is connected to the rod string extending downhole through a bottom-
21 tapered rod coupler. The polish rod extends through a stuffing box to seal
the
22 rotating polish rod and well from the environment at surface. Typically
very little
23 pressure is applied to the stuffing box. A progressive cavity pump is
subject to
24 plugging at or adjacent the stator and rotor. Fluids are sometime pumped
downhole to flush debris from the pump.
CA 02452696 2004-09-16
1 One major concern is well fluid leaking onto the ground from
2 premature stuffing box failure; due to the high pressure being exerted on it
while
3 the well is being flushed. This flushing operation is done by pulling the
rotor out
4 of the stator by lifting the polish rod to the top of its bottom-tapered rod
coupler.
This allows the flush-by operation to then back-flush the production tubing to
6 remove sandy oil that is blocking the free flow of oil. The pressure exerted
onto
7 the tubing is the same pressure exerted onto the stuffing box, which can
reach
8 levels of 2500 psig.
9 In Canadian patents #2353277, #2027373, and #2171495 it clearly
shows that the main disadvantage in stuffing boxes is that they only seal
around
11 the polish rod extending therethrough. During flushing operations, greater
force
12 is exerted directly into the seal elements, which in tum causes the
premature
13 failure of the stuffing box.
14 What is needed is a device which aids in the longevity of existing
stuffing boxes and greatly reduces the occurrence of well fluid leaking to
16 atmosphere.
17
18 SUMMARY OF THE INVENTION
19 In one preferred embodiment, damage due to pressure exerted
during flushing is avoided and wellhead drive assembly seals protected through
a
21 housing positioned between the wellhead drive assembly and the well. The
22 housing is universal in that it is independent of the type of wellhead
drive
23 assembly or stuffing box; the housing need only be adapted to the polish
rod.
24 The housing introduces a sealing ring that seals around a tapered rod
coupler of
the polish rod for preventing high pressure from being exerted directly onto
seal
2
CA 02452696 2004-09-16
1 elements thereabove including whether the seal element are part of the
housing
2 or part of the wellhead drive assembly. Further, the housing spaces the
wellhead
3 drive assembly from the well as needed. Advantageously, a flange-to-flange
end
4 design of the housing allows installation of this device between any well
flow tee
of the well and the wellhead drive assembly.
6 In a broad aspect, apparatus is provided for sealing a polish rod
7 below a wellhead drive assembly connected to a well, the polish rod having a
8 tapered rod coupler at a bottom end, the apparatus comprising: a housing
having
9 a top end adapted for connection to the wellhead drive assembly and a bottom
end adapted for connection to the well, the housing having a bore for passing
the
11 polish rod therethrough; and a sealing ring positioned in the bore adjacent
the
12 bottom end, wherein when the polish rod is lifted to contact the tapered
rod
13 coupler with the sealing ring the well is isolated from the top end of the
housing.
14 The apparatus enables exercise of a method for sealing a polish
rod below a wellhead drive assembly connected to a well while flushing the
well
16 under pressure, the polish rod having a tapered rod coupler at a bottom
end, the
17 method comprising: providing a housing between the wellhead drive assembly
18 and the well the housing, the polish rod passing therethrough and having a
19 reduced diameter section of the bore adjacent the housing's bottom end and
sealing ring therebelow; lifting the polish rod to rest against the reduced
diameter
21 section and seal against the sealing ring; and applying pressure to the
well for
22 flushing the well wherein the sealing ring protects the wellhead drive
assembly
23 from the pressure in the well.
24 In another aspect of the invention, a system is provided for sealing
a polish rod in a well comprising: a wellhead drive assembly having a polish
rod
3
CA 02452696 2004-09-16
1 sealing stuffing box adapted for connection to the well and the polish rod
2 extending therethrough; a protector housing having a top end adapted for
3 connection to the stuffing box and a bottom end adapted for connection to
the
4 well, the housing having a bore for passing the polish rod therethrough; and
a
polish rod seal in the bore of the housing, wherein the protector housing
seals
6 the polish rod before the polish rod extends through the stuffing box.
7 In another aspect, the life of the stuffing box of any wellhead drive
8 assembly can extended through the installation of a polish rod seal of an
9 embodiment of the invention. Where a wellhead drive assembly has a stuffing
box connected to a well and the stuffing box and well having a standard flange
11 connection therebetween then apparatus can be employed comprising: a
housing
12 having a bore for passing the polish rod therethrough; a standard flange at
a top
13 end of the housing for connection to the stuffing box of the wellhead drive
14 assembly; a standard flange at a bottom end of the housing for connection
to the
well; and a polish rod seal in the bore of the housing, wherein the polish rod
seal
16 extends the longevity of the stuffing bax.
17
18 BRIEF DESCRIPTION OF THE DRAWINGS
19 Figure 1 is a cross-sectional view of one embodiment of the
housing for a cylindrical through-bore stuffing box unit with universal
flanged
21 connections; and
22 Figure 2 illustrates greater detail of the internal components of the
23 bore of the housing according to Fig. 1.
4
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1 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
2 Having reference to Fig. 1, one embodiment of the universal
3 pressure protector 100 is shown comprising a housing 101 having a barrel 2,
a
4 top flange 1 and a bottom flange 3. The housing 101 is typically a one-piece
cylindrical through-bore steel unit with universal flanged designed ends
6 resembling a dumbbell shape. A polish rod can extend through the housing
101.
7 The universal pressure protector 100 is for use with an oil well that
8 has a rotary pump in which a polish rod is used to rotate the rotor of a
down-hole
9 pump on either a straight or slanted well. The housing 101 is typically
mounted
at surface between the top of a flow tee and the bottom end of a wellhead
drive
11 unit assembly. The wellhead drive unit assembly typically comprises an
upper an
12 existing stuffing box which restrains oil fluid leakage from the flow tee.
13 In one embodiment, the universal pressure protector 100 is an
14 extender on oil wells when more distance is needed between the flow tee and
wellhead drive unit assembly.
16 The top flange 1, such as an industry standard RTJ R31 flanged
17 end (ASME B16.5 Class 300 - 8-bolt flange for nominal 3" pipe), is bolted
to the
18 bottom of a stuffing box of an oil well drive unit (not shown). The flange-
to-flange
19 design of a R31 type flange is capable of bolting under any current brand
or type
of wellhead drive unit assembly and flow tee or well that is used on a rotary
drive
21 oil well which is known to applicant.
22 The barrel 2 has an outer thick wall of the through-bore barrel that
23 houses the inner parts of the universal pressure protector 100. The bottom
24 flange 3, a R31 flange designed end, is bolted to the top of an oil well
flow tee
(not shown). High-pressure grease nipple entries allowing lubrication of
tapered
5
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1 brass bushings, packing, and cavity. Through-bore grease nipples 4,5 grease
2 the packing, brass mandrel and bottom-tapered bushing (See Fig. 2). A
through-
3 bore grease nipple 6 greases the top-tapered brass bushing and fills the top
4 sealed cavity located between the top of the housing 101 and the bottom
flange
of a stuffing box.
6 The top and bottom flanges 1,3 are fit with inside threads 7,8
7 respectively which allow lock-down rings 21,13 to be screwed therein. The
8 flanges 1,3 are fit with eight bolt holes 9 which enable bolting of the
device 100 to
9 either the flow tee with the bottom flanged designed end 3, and the upper
stuffing
box with the top flanged designed end 1.
11 In more detail, with reference to Fig. 2, the inner part of the through-
12 bore barrel 2 has a bore 23 where the polish rod slides through. The bore
13 houses the sealing components of this embodiment comprising:, a sealing
ring
14 11, a bottom threaded lock-down ring 12 and setscrew 13, a bottom bushing
14
with wiper rings 15, grease mandrel 16, a first plurality of packing rings 17,
spring
16 18, a second plurality of packing rings 19, a top bushing 20, a top
threaded lock-
17 down ring 21 and setscrew 22.
18 The bottom-tapered brass bushing 14 helps to centralize and
19 stabilize the polish rod. The top-tapered brass bushing 20 also helps to
centralize and stabilize the polish rod.
21 TeflonT"" (trademark of Dupont) wiper rings 15 are recessed into the
22 bottom-tapered brass bushing 14 which cleans off oil and sand from the
polish
23 rod as it is being lifted through the through-bore barrel 2. The brass
grease
24 mandrel 16 allows grease to pass through and lubricate between the polish
rod
and bushings 20,14.
6
CA 02452696 2004-09-16
1 A first plurality of packing rings 17 and a second plurality of packing
2 rings 19 seal around the polish rod. The first and second plurality of
packing
3 rings 17,19 are sandwiched between the top and bottom bushings 20,14. A
4 spring 18, when compressed, hold tension on these packing rings 17, 19. The
spring 18 can be positioned between the first and second plurality of packing
6 rings 17,19. The spring 18 is compressed when the threaded lock-down ring 21
7 is threaded into the housing 101 and locked with setscrew 22 at the top of
8 cylindrical through-bore barrel 2.
9 The threaded lock-down ring 21 is locked in with the setscrew 22.
Further the top-tapered brass bushing 20 is also pushed down by the top
11 through-bore threaded lock-down ring 21, compressing the spring 18 and
packing
12 rings 17,19 that seal around the polish rod.
13 The bore 23 forms a relatively reduced diameter section 10 of the
14 through-bore barrel 2. The bottom-reduced diameter section 10 of through-
bore
23 secures the bottom-tapered bushing 12 in said through-bore 23.
16 This reduced diameter section 10 is the point where the bottom-
17 tapered rod coupler of a polish rod comes to rest when lifted out of the
oil well
18 production tubing in preparation for a flushing operation. This reduced
diameter
19 section 10 positions and stabilizes the bottom-tapered rod coupler of a
polish rod
during flushing operations and also keeps the bottom-tapered rod coupler from
21 coming in contact with the bottom-tapered brass bushing 14.
22 The sealing or rubber ring 11 seals around the top of the bottom-
23 tapered rod coupler of the polish rod for sealing off oil fluid from
entering the
24 sealing elements thereabove during flushing operations. This rubber ring 11
is
7
CA 02452696 2004-09-16
1 held in place by the bottom threaded lock-down ring 12 which has a through-
bore
2 center and is locked with a setscrew 13.
3 Accordingly, in use, in preparation far a flushing operation, the
4 polish rod is lifted to seal against the tapered rod coupler of the polish
rod,
thereby sealing the well from the wellhead drive assembly. When pressure
6 resulting from the flush by operation is exerted on the well, any seals
above the
7 sealing ring, including the polish rod seals 19,17 and the existing stuffing
box of
8 the wellhead drive assembly are protected. The tapered rod coupler can rest
9 against the reduced diameter section with the tapered rod coupler sealing
against
the sealing ring
11 When the housing is bolted to the upper stuffing box of a wellhead
12 drive unit assembly a sealed cavity is formed. The cavity can be filled
with
13 grease through the top grease nipple 6.
14 Within the oilfield industry is found many different types of corrosive
materials that will determine which types of materials are used to build a
16 universal pressure protector 100. This enables the adaptation for use under
17 many unique conditions found throughout the oil fields. The outer shell, or
flanges
18 1,3 and barrel 2, can be made from many different types and grades of
steel. The
19 tapered brass bushings 20,14, brass mandrel 16, grease nipples 4,5,6, inner
spring18, packing rings 17,19, TeflonT"" rings 15, rubber ring 11, and lock-
down
21 rings 21,12 can all be made from many different types of material. Further,
the
22 TefIonT"" rings, rubber ring, tapered brass bushings, brass mandrel, and
packing
23 rings can all be sized to fit any polish rod size.
24 The intended use of a Universal Pressure Protector is to protect
well equipment above the flow tee on an oil well, by absorbing the brunt of
the
8
CA 02452696 2004-09-16
1 tubing pressure that is exerted from the well pump. This Universal Pressure
2 Protector can also be used as an extender on oil wells when more distance is
3 needed between the flow tee and the wellhead drive unit.
9
