U.S. patent application number 10/650708 was filed with the patent office on 2005-03-03 for bearing assembly for a progressive cavity pump and system for liquid lower zone disposal.
Invention is credited to Doyle, John P., Tessier, Lynn P., Weber, James L..
Application Number | 20050045333 10/650708 |
Document ID | / |
Family ID | 34217232 |
Filed Date | 2005-03-03 |
United States Patent
Application |
20050045333 |
Kind Code |
A1 |
Tessier, Lynn P. ; et
al. |
March 3, 2005 |
Bearing assembly for a progressive cavity pump and system for
liquid lower zone disposal
Abstract
A progressive cavity pump pumps liquid downhole to a lower
formation past a packer set in a casing of a wellbore. The rotor of
the pump is axially restrained by a bearing assembly spaced below
the pump for controlling uphole reactive loading on the rotor.
Preferably the rotor is releasably coupled to the bearing assembly
for release and recovery of the rotor from the bearing assembly.
Such a releasable coupling is a latch comprising a plunger
telescopically and releasably coupled with a housing using a dog
and track arrangement, the dog and track utilizing the telescoping
action to actuate the coupling and releasing of the latch.
Inventors: |
Tessier, Lynn P.; (Cochrane,
CA) ; Weber, James L.; (Calgary, CA) ; Doyle,
John P.; (Calgary, CA) |
Correspondence
Address: |
SEAN W. GOODWIN
237- 8TH AVE. S.E., SUITE 360
THE BURNS BUILDING
CALGARY
AB
T2G 5C3
CA
|
Family ID: |
34217232 |
Appl. No.: |
10/650708 |
Filed: |
August 29, 2003 |
Current U.S.
Class: |
166/305.1 ;
166/106 |
Current CPC
Class: |
E21B 23/006 20130101;
E21B 43/126 20130101 |
Class at
Publication: |
166/305.1 ;
166/106 |
International
Class: |
E21B 043/32 |
Claims
The embodiments of the invention for which an exclusive property or
privilege is claimed are defined as follows:
1. Apparatus in the casing of a wellbore for injecting liquid to a
lower formation with a PC Pump having a rotor, comprising: a packer
set in the casing above the formation and adapted for pumping
liquids, from uphole of the packer, downhole through the PC Pump
and into the lower formation; and a bearing assembly positioned
downhole of the PC Pump and spaced from the stator, a shaft
connected to the rotor and bearings for rotatably supporting and
axially restraining the rotor to the bearing assembly so that as
the PC Pump rotor rotated to pump liquid through the stator from
above the packer to the formation below the packer, uphole loads
acting on the rotor are restrained through the bearing
assembly.
2. The apparatus of claim 1 wherein the bearing assembly further
comprises a releasable coupling between the shaft and the
rotor.
3. The apparatus of claim 1 wherein the releasable coupling
comprises: a first connection depending from the rotor; a second
connection extending from the shaft; and cooperative means between
the first and second connections.
4. The apparatus of claim 3 wherein a pony shaft is connected
between the first and second connection.
5. The apparatus of claim 3 wherein the second connection further
comprises a housing having a bore; and the first connection further
comprises a plunger so that when the plunger engages the bore of
the housing the first and second connection become coupled.
6. The apparatus of claim 5 further wherein the plunger and the
housing form a latch operable between two positions: a first
position wherein the first and second connections are coupled; and
a second position wherein the first and second connections are
released.
7. The apparatus of claim 6 wherein the latch further comprises:
one or more dogs formed in the bore of the housing, and a track
formed on the plunger and operable with a first axial movement to
capture the dog for coupling the first and second connections and
operable with a second axial movement to release the one or more
dogs for uncoupling the first and second connections.
8. The apparatus of claim 6 wherein the latch further comprises:
one or more dogs on the plunger; and a track formed in the bore of
the housing and operable with a first axial movement to capture the
dog for connecting the first and second connections and operable
with a second axial movement to release the one or more dogs for
uncoupling connecting the first and second connections.
9. The apparatus of claim 6 further comprising a pup-joint spacing
the stator from the bearing assembly and having perforations formed
therein for directing pumped fluids into the wellbore for injection
into the lower formation.
10. The apparatus of claim 9 further comprising a one-way valve
located below the pup-joint perforations and above the lower
formation.
11. The apparatus of claim 1 wherein the bearings of the bearing
assembly is sealed from the pumped liquids.
12. The apparatus of claim 11 wherein the shaft extends through a
bore in the housing and the bearings rotatably support the shaft
from the housing, the bearing assembly further comprising: an
uphole seal for sealing between the rotatable shaft and the
housing; and a downhole seal for sealing the bore of the housing so
as to protectively sandwich the bearings therebetween.
13. The apparatus of claim 11 wherein: the uphole seal further
comprises a first seal face sealed and rotatable with the shaft and
biased to rotatably seal against a second seal face supported by
and sealed to the housing.
14. The apparatus of claim 11 wherein the downhole seal further
comprises: a piston in the bore of the housing and having annular
seals therebetween; and a spring biasing the piston downhole so
that the piston is sealably slidable in the bore for equalizing
pressure between the formation and the bore.
15. The apparatus of claim 1 further comprising a pup-joint spacing
the stator from the bearing assembly and having perforations formed
therein for directing pumped fluids into the wellbore for injection
into the lower formation.
16. The apparatus of claim 15 further comprising a one-way valve
located below the pup-joint perforations and above the lower
formation.
17. A method for injecting liquid from a wellbore into a lower
formation with a PC Pump having a rotor and a stator, comprising:
anchoring the packer in the wellbore above the lower formation;
rotating the rotor for pumping liquids from uphole of the packer
downhole through the PC Pump and into the lower formation; and
supporting the rotor with a bearing assembly positioned downhole of
the PC Pump and spaced from the stator.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a regular application of: U.S. Patent
provisional application Ser. No. 60/406,338, filed Aug. 28, 2002,
the entirety of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] In one aspect, the invention relates generally to the use of
a progressive cavity pump (PC Pump) for pumping water downhole for
disposal and more particularly to a bearing package for resisting
reactive rotor loads of a PC Pump for pumping water downhole for
disposal. In another aspect, the invention relates generally to
complementary male/female profiled latch components which are
applied in a variety of downhole operations to releasably couple
components such as for coupling a pump rotor to a bearing package
or drivably coupling a pump rotor to surface through a rod
string.
BACKGROUND OF THE INVENTION
[0003] It has been a long recognized problem that during production
of hydrocarbons, particularly from gas wells, liquids, primarily
water, accumulate in the wellbore. As the liquid builds at the
bottom of the well, a hydrostatic pressure head is built which can
become so great as to overcome the natural pressure of the
formation or reservoir below, eventually "killing" the well.
[0004] A fluid effluent, including liquid and gas, flows from the
formation and through perforations in the casing. Liquid
accumulates as a result of condensation falling out of the upwardly
flowing stream of gas or from seepage of liquids from the formation
itself. To further complicate the process the formation pressure
typically declines over time. Once the pressure has declined
sufficiently so that production has been adversely affected, or
stopped entirely, the well must either be abandoned or
rehabilitated. Most often the choice becomes one of economics,
wherein the well is only rehabilitated if the value of the
unrecovered resource is greater than the costs to recover it.
[0005] Many techniques have been utilized to attempt to remove
liquids which have accumulated in the wellbore. Of these many
techniques some are focused on lifting liquids uphole to the
surface, such as in gas or plunger lift systems. Other techniques
have been focused on pumping water below the producing zone and
into a lower portion of the formation that can act as a reservoir
to accommodate the pumped water. These techniques are typified by
arrangements that collect liquids below a conventional
uphole-pumping pump, pump them slightly uphole and them route them
back downhole through bypass tubing. These arrangements are subject
to loss of head pumping failures in attempting to establish suction
under low head conditions to pump uphole.
SUMMARY OF THE INVENTION
[0006] Described herein is a combination of novel elements which
enable convenient and effective implementation of a system of
direct pumping of liquid to a lower formation for disposal. In a
preferred embodiment, a novel arrangement of a PC Pump is applied
for pumping downhole through a packer, the rotor being rotatable
yet axially restrained in a novel manner against uphole reactive
loading and a novel latch being releasably coupled to the
rotor.
[0007] In one aspect of the invention, a PC Pump is used to pump
liquid directly downhole for disposal. However, Applicant's
recognize that the rotor of the pump must be held down into
position in the stator during this operation.
[0008] In one broad aspect of the invention apparatus is located in
the casing of a wellbore for injecting liquid to a lower formation
with a PC Pump having a rotor and a stator, comprising: a packer
set in the casing above the formation and adapted for pumping
liquids, from uphole of the packer, downhole through the PC Pump
and into the lower formation; and a bearing assembly positioned
downhole of the PC Pump and spaced from the stator, a shaft
connected to the rotor and bearings for rotatably supporting and
axially restraining the rotor to the bearing assembly so that as
the PC Pump rotor rotated to pump liquid through the stator from
above the packer to the formation below the packer, uphole loads
acting on the rotor are restrained through the bearing
assembly.
[0009] The apparatus enables operation of a method for injecting
liquid from a wellbore into a lower formation comprising anchoring
the packer in the wellbore above the lower formation; rotating the
rotor for pumping liquids from uphole of the packer downhole
through the PC Pump and into the lower formation; and supporting
the rotor with a bearing assembly positioned downhole of the PC
Pump and spaced from the stator.
[0010] Accordingly, in another aspect of the invention, a bearing
assembly is provided for restraining uphole movement of a PC Pump
rotor while pumping water downhole for disposal. The bearing
assembly comprising a shaft extending through a bore in a housing
and having bearings rotatably supporting the shaft from the
housing, an uphole seal for sealing between the rotatable shaft and
the housing; and a downhole seal for sealing the bore of the
housing so as to protectively sandwich the bearings therebetween.
Preferably, the uphole seal further comprises a first seal face
sealed and rotatable with the shaft and biased to rotatably seal
against a second seal face supported by and sealed to the housing.
The bearing assembly is preferably pressure equalized having a
piston in the bore of the housing and having annular seals
therebetween; and a spring biasing the piston downhole so that the
piston is sealably slidable in the bore for equalizing pressure
between the formation and the bore.
[0011] Further, the rotor is preferably removable for maintenance.
There are a variety of mechanisms to releasably couple downhole
components including collets and shear devices. Due to the
inaccessibility of the downhole location and the need for gross
movements to effect actuating movement at the point of coupling,
there is a need for a reliable and simple coupling device. As set
forth above, one downhole operation which is critically dependent
on the ability to releasable couple two downhole wellbore
components is a situation wherein a PC Pump rotor is restrained
against uphole movement as opposed to the conventional restraint
against downhole movement during uphole pumping activities.
[0012] Accordingly, in yet another aspect of the invention, a
releasable coupling or latch is provided. While the disclosed
embodiments are predominately downhole implementations, the latch
can be used as surface as well, for instance, to drivably couple a
top drive to a polish rod. Further, the latch has characteristics
such as being preferably sufficiently compact to be insertable
through the PC Pump's stator. In another downhole pumping
situation, large PC Pumps can be suspended at the end of tubing.
However, the corresponding and large rotors are too large to insert
or remove through the tubing string. Accordingly, in this
situation, there is a need for a torque-capable releasable coupling
between the drive rod string and the uphole end of a rotor which
remains in the stator of the PC Pump.
[0013] A qualifying releasable coupling for each of these scenarios
is a telescopically coupled plunger and latch housing having
complementation radial dogs and a track which implement downhole
and uphole manipulation therebetween to effect an automatic,
indexed relative rotation therebetween to alternately lock and
release the coupling while further enabling the transmission of
torque as desired. The tool is implemented in an alternating
on/locked and off/released manner.
[0014] In one broad aspect of the invention apparatus for
releasably coupling first and wellbore components, at least one of
the first or second wellbore components being capable of rotation
in response to applied rotational force, comprises a housing
adapted for connection to the first wellbore component and having a
bore with a first half of a dog and track arrangement formed
thereto having at least one dog; and a plunger adapted for
connection to the second wellbore component and being sized to fit
telescopically axially into and out of the bore, the plunger having
a second half of the dog and track arrangement formed thereto, the
track of the dog and track arrangement having at least one entrance
to and from a circumferential portion, the circumferential portion
bounded by a discontinuous proximal cam, through which the at least
one entrance extends, and a distal cam spaced from the proximal
cam, so that
[0015] in a first action, when the plunger telescopes into the
housing, each dog is guided through the at least one entrance into
the circumferential portion, coupling the plunger and the housing,
each dog contacting the distal cam for causing relative rotation
between the housing and the plunger until engaging a first
rotational stop out of alignment with the entrance in a first
rotationally and axially coupled position, and
[0016] in a second action, when the plunger telescopes out of the
housing, each dog contacts the proximal cam for causing relative
rotation between the housing and the plunger until engaging a
second rotational stop out of alignment with the entrance in a
second rotationally and axially coupled position, and
[0017] in a third action, when the plunger telescopes into the
housing, each dog contacts the distal cam for causing relative
rotation between the housing and the plunger until engaging a third
rotational stop substantially aligned with the entrance, so
that
[0018] in a fourth action, when the plunger telescopes out of the
housing, each dog is guided through the at least one entrance to
release the plunger from the housing.
[0019] In another broad aspect, the apparatus enables practicing a
novel method for releasably coupling a first wellbore component to
a second wellbore component, comprising: telescoping the plunger
into the housing for guiding the one or more dogs through
corresponding entrances into the track and engaging the track to
causing relative rotation between the housing and the plunger until
engaging a first rotational stop in a first rotationally and
axially coupled position out of alignment with the corresponding
entrances, and telescoping the plunger out of the housing for
engaging the track and causing relative rotation between the
housing and the plunger until engaging a second rotational stop in
a second rotationally and axially coupled position out of alignment
with the corresponding entrances, and telescoping into the housing
for engaging each dog with the track to causing relative rotation
between the housing and the plunger until engaging a third
rotational stop substantially aligned with the corresponding
entrances, and telescoping the plunger out of the housing for
guiding each dog through the corresponding entrances to release the
plunger from the housing.
[0020] Preferably, the releasable coupling is located between the
downhole end of a rotor of a PC Pump and an uphole end of a bearing
assembly spaced below the PC Pump.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a cross-sectional elevation of a wellbore having
PC Pump and a bearing assembly accordingly to one embodiment of the
invention.
[0022] FIG. 2 is a perspective view of the housing of a bearing
assembly of the present invention having a latch housing connected
thereto for connection using a latch plunger to a rotor (not shown)
of a PC Pump;
[0023] FIG. 3a is a downhole end view of the bearing assembly
housing according to FIG. 2 further detailing showing a snap ring
at a lower end of the housing, a hex nut and a lower piston face
retained by the snap ring;
[0024] FIG. 3b is a cross-sectional view of the bearing assembly
housing, latch housing and plunger according to FIG. 3a as
sectioned along section lines A-A;
[0025] FIG. 3c is a cross-sectional view of the latch housing and
plunger according to FIG. 3b taken along section lines B-B;
[0026] FIG. 4 is a perspective view of the latch housing according
to FIG. 3b with a partial cutaway to illustrate the radial profile
of a latch dog;
[0027] FIG. 5a is an end view of a latch housing according to FIG.
4;
[0028] FIG. 5b is a cross-sectional view of the latch housing
according to FIG. 5a taken along section lines A-A and illustrating
an axial post at a downhole end for coupling to a shaft of the
bearing assembly;
[0029] FIG. 6a is a downhole end view of a latch plunger adapted
for connection to the rotor of a PC Pump, the plunger being adapted
for latching with the latch housing and latch dogs according to
FIGS. 3b and 5b;
[0030] FIG. 6b is a cross-sectional view according to FIG. 6a taken
along section lines A-A;
[0031] FIG. 6c is a side view of the latch plunger according to
FIG. 6b;
[0032] FIG. 6d is a cross-sectional view according to FIG. 6c along
section lines C-C;
[0033] FIG. 6e is a cross-sectional view according to FIG. 6c along
section lines G-G;
[0034] FIG. 7a is a perspective view of the latch plunger according
to FIG. 6c;
[0035] FIG. 7b is a partial perspective view of an upper profiled
track and a lower profiled track of the plunger assembly according
to the cutaway E of FIG. 7a;
[0036] FIG. 7c is a side view of the upper profiled track according
to cutaway F of FIG. 6c;
[0037] FIG. 7d is a partial side view of the lower profiled track
according to the cutaway D of FIG. 7c;
[0038] FIG. 8 is a roll-out schematic view of the circumferential
arrangement of a latch according to one embodiment of the
invention. The roll-out illustrates the progressive movement of a
dog of the latch housing (only one of three shown for clarity) as
the plunger and the lower and upper profiled tracks interact with
the latch dog between released, latched, and released once
again;
[0039] FIGS. 9a-c are partial side views illustrating the housing
and plunger of another embodiment of the invention, operating
according to the principles set forth in FIG. 8 and illustrating
the sequence for engaging the latch plunger of a rotor to the latch
housing of the bearing assembly where,
[0040] FIG. 9a illustrates the latch plunger entering a bore of the
latch housing,
[0041] FIG. 9b illustrates the latch plunger being pushed into the
latch housing, rotating the latch housing to cause a latch dog to
engage the upper latch track, and
[0042] FIG. 9c illustrates pulling the plunger uphole to cause the
latch housing to rotate and the latch dog to lock into the lower
profiled track;
[0043] FIGS. 10a and 10b together illustrate a cross-sectional view
of a wellbore casing according to an embodiment of the invention
wherein a stator of a PC Pump is connected to a tubing string and
wherein the rotor is installed through the tubing string and into
the stator, the lower end of the rotor being latched into a lower
bearing assembly for pumping liquid water downhole, the packer, an
optional anchor and a one way valve being illustrated in schematic
form only;
[0044] FIGS. 11a and 11b together illustrate a cross-sectional view
of a wellbore casing according to another embodiment of the
invention wherein the rotor of a PC Pump, anchored downhole, is
lowered into the stator using co-rod, coiled tubing or the like,
and is latched into a lower bearing assembly for pumping liquid
water downhole;
[0045] FIG. 12 is a perspective view of a male and female latch
prior to coupling, the plunger and the housing being arranged for
more generic connection with their respective components, threaded
ends and wrench flats being provided for both;
[0046] FIG. 13 is a cross-sectional views of the male and female
components of the latch in the working and fully set downhole
rotated position;
[0047] FIG. 14 is a schematic view illustrating an implementation
of the latch for releasably coupling with an oversize rotor for
driving the rotor in a pump stator at the end of a tubing string;
and
[0048] FIG. 15 is an optional embodiment with the latch housing
connected to a rod string and the plunger connected to the top of a
PC Pump rotor, all of the description associated with FIG. 8 being
applicable if uphole/downhole are inversed.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0049] With reference to the schematic of FIG. 1, a system 10 is
provided for lower zone disposal in a well. A PC Pump 11 is located
downhole and arranged to pump below a packer 12 to isolate a zone
below the pump itself. Conventional rod string is threaded for RH
rotation. Causing a PC Pump to pump downwardly without first
pumping uphole can be achieved with a downwardly pumping rotor
having and opposite helix to conventional rotors so that
conventional rod threading and rotation can be maintained. The PC
Pump rotor 13 is restrained from reactive uphole movement with a
bearing assembly 14 and coupling means 15 are provided for
releasably coupling the rotor 13 with the bearing assembly 14.
[0050] Each of the bearing assembly 14, the disposal system 10 and
the coupling means 15 are discussed herein.
[0051] Generally, with reference to schematic FIG. 1, and to more
detailed FIGS. 10a-11b, several embodiments of the invention are
illustrated for disposing of liquid to a formation below a packer
12. In one embodiment in FIGS. 1 and 10a-10b a stator 16 of the PC
Pump 11 is fit to the bottom of a tubing string 17 and positioned
downhole below perforations 18 in the casing 19 of a cased wellbore
of a gas well. As shown, accumulated liquid 20 can interfere with
the perforations and inflow of gas. Tubing perforations 20b
positioned downhole of the casing perforations 18 enable draining
of accumulated liquid into the PC Pump 11. Minimum pumping head
issues are obviated by placing the PC Pump suction at the top of
the pump for downward pumping. The PC Pump rotor 13 is suspended
from a rod string 21 extending downhole in the tubing string 17 to
fit operably into the stator 16. The rotor 13 extends through a
pup-joint 22 to connect to a bearing assembly. Liquid from the PC
Pump is discharged through perforations 23 in the pup joint 22 for
disposal into a lower formation 30 (FIG. 10b), typically through a
one-way valve 31.
[0052] The bearing assembly 14 is spaced and supported from the
stator 16 via the pup-joint connection 22 for resisting the loads
placed thereon by the rotor. The stator 16 is typically supported
in the casing 19 with the packer 12. Use of a convention anchor is
optional in conjunction with the packer 12 or if the packer 12 is
not rotationally supporting the stator 16.
[0053] Similarly in the embodiment of FIGS. 11a,11b, a PC Pump is
positioned downhole below the perforations 18 in the casing and the
casing 19 itself is used as the gas production tubing to surface.
The PC Pump stator or other connected tubing is isolated with the
packer 12 and is anchored to the casing 19 without the need for a
supporting tubing string.
[0054] The packer 12, preferably a hydraulic packer, is set
adjacent a bottom of the well above the lower formation 30 into
which water can be disposed. The operation of the system is
described in greater detail below.
[0055] As shown in FIG. 1, in use, the downhole-pumping rotor 13
generates uphole reactive loads. If not restrained, the rotor 13
will move uphole to pull free or otherwise damage the stator 16.
Accordingly, the rotating rotor 13 is restrained against uphole
movement with the bearing assembly 14. The reactive loads borne by
the bearing assembly 14 are resisted through the pup-joint
connection 22 to the bottom of the PC Pump stator 16.
[0056] Water Disposal
[0057] For implementing an embodiment of the disposal invention, as
shown in FIGS. 10a-10b, a bottom packer 12b, preferably a hydraulic
packer, is set adjacent a bottom of a well above a lower formation
30 into which liquid such as water can be disposed. A tubing string
17 containing the bearing assembly 14 and latch housing 60 of the
present invention as well as the stator 16 of a PC Pump 11 is
lowered into the wellbore above the bottom packer 12b. A second
packer 12 is set near the top of the PC Pump 11 to hold the stator
16 and tubing 17 in place. The intake of the PC Pump 11 is
positioned below the perforations. A plunger 61 is attached to a
rotor 13, preferably by a pony rod 21 so as to minimize any effects
caused by the eccentric rotation of the rotor 13. A series of ports
20b are formed in the tubing string 17 below the perforations 18
and above the PC Pump 11 to permit water, which is heavier than gas
to enter and fall into the pump. The PC Pump is configured to draw
the water downhole and through a one way valve 31 such as that set
in bottom packer 12b. Thus the liquid, disposed of in the higher
pressure formation below, cannot return uphole.
[0058] The rotor 12 is lowered into and through the stator 16 until
the plunger 61 engages the latch housing 60 and the rotor 12 is
locked into position in the bearing assembly 14. Pumping can then
begin.
[0059] In a second embodiment of the invention, as shown in FIGS.
11a-11b, a lower packer 12b is set as in the first embodiment. The
bearing assembly 14 with a stator 16 attached at surface is lowered
into the wellbore, below the perforations 18 using coiled tubing or
the like (not shown) and is held in place by a second packer 12 set
adjacent an uphole end of the PC Pump 11. A cone inlet 11a is fit
to the inlet of the stator 11 to assist in directing the plunger 61
and rotor 12 into the stator. The rotor 13 and attached plunger 61
are then lowered into the wellbore using co-rod or coiled tubing
and the rotor 13 is latched to the bearing assembly 14 as described
above. Liquid produced through the perforations 18 above the pump
falls into the cone inlet 11a and enters the PC Pump 11. In the
embodiment of the invention shown in FIGS. 11a,11b, significant
costs can be saved as a service rig is not required, due to the
elimination of jointed tubing string. All of the operations
described in this embodiment can be performed using co-rod or
coiled tubing without the need for a service rig.
[0060] Bearing Assembly
[0061] With reference to FIGS. 2, 3a-c, and 10b the bearing
assembly 14 is provided for preventing uphole movement of the rotor
13 of a PC Pump 11 while pumping liquid 20 downhole for
disposal.
[0062] As shown in FIGS. 1,10b, the bearing assembly 14 does not
impede the casing 19 so that disposed liquid 20 can pass thereby. A
bypass of the bearing assembly can be through the assembly itself
(not shown) or, as shown, can be around the assembly through an
annular passage 32 formed between the assembly 14 and the casing
19.
[0063] As shown in FIGS. 2 and 3b, the bearing assembly 14
comprises a non-rotating bearing housing 40 defining a bore 41
through which a rotating inner shaft 42 extends. An annular passage
32 is formed between the housing 40 and the casing 19 (see FIG.
10b). The housing 40 is secured against rotation and relative
movement relative to the PC Pump (not shown).
[0064] A latch housing 60 is connected at an uphole end of the
inner shaft 42 and is adapted for latching to a plunger 61 adapted
for connection to the rotor 13 of the PC Pump 11. The inner shaft
42 is supported for rotation and against reactive axial loading.
One or more lower thrust bearings 43 are positioned adjacent a
lower end of the shaft 42. One or more upper radial bearings 44 are
fit adjacent an upper end of the inner shaft 42. While preferably
the upper bearings 44 support radial loading, they may also support
axial thrust. Similarly, why it is preferred that the lower
bearings 43 primarily support thrust, they may also be specified to
support radial loading as well. The lower and upper bearings 43,44
are isolated from well liquids 20 with a sealing system.
[0065] The lower thrust bearings 43, such as angular contact ball
bearings, are fit to an annular space 45 created between the inner
shaft 42 and the non-rotating outer housing 40. A nut and washer
assembly 46 secure the lower end of the inner shaft 42 to the lower
thrust bearings 43 which are rotationally supported through a
shoulder 47 formed in the outer housing 40. The annular space 45 is
sealed from the wellbore environment by upper seals 50a,50b and a
lower seal 51. The lower seal 51 is formed between a spring-biased
lower piston 52 between the lower bearings 43 and the outer housing
40. The lower seal 51 is a non-rotating seal sealably and slidably
fit to the non-rotating outer housing 40. The lower piston 52 is
spaced downhole of the lower end of the inner shaft 42 creating a
reservoir for clean lubricating fluid in fluid communication with
the annular space 45 for lubricating the bearings 43,44.
[0066] The inner shaft 42 is further supported against lateral and
radial loading by the upper radial bearings 44 such needle bearings
positioned in the annular space 45 adjacent an upper seal housing
53 positioned between the upper seal 50 and the outer housing 40.
The upper seal housing 53 is located above the upper bearings 44.
The upper seals 50a,50b seal despite relative rotation between the
inner shaft 42 and the housing 40.
[0067] The upper seals 50a,50b preferably comprise opposing,
mirrored tungsten or silica carbide seal faces. A first rotating
upper seal 50b is connected to the inner shaft 42 by the upper seal
housing 53 and a second static upper seal 50a is connected to the
outer housing 40 below the first rotating upper seal 50b. The first
rotating upper seal 50b is biased towards and rotates upon the
second static seal face 50a in a sealed relationship so as to
substantially prevent the loss of lubricant from the annular space
45.
[0068] The lower seal's lower piston 52 acts to equalize pressure
within the annular space 45 to be substantially that in the
wellbore. Further, the lower piston 52 has a preload spring 54
which allows it to react to small losses of lubricant from the
bearing assembly annular space.
[0069] As shown in FIGS. 10a, 10b and 3b, the rotor 13 and plunger
61 releasably couple to the latch housing 60 for restraining the
rotor 13 thereto and thereby retaining the rotor 13 in the PC Pump
stator 16 in a proper pumping relationship.
[0070] Latch
[0071] In greater detail and with reference to FIGS. 3b, 4-7d, the
means 15 for connecting the rotor and bearing assembly 14 is a
latch 15b. The latch is capable of releasably coupling a variety of
wellbore components together without the need to specifically
rotatably align the cooperating mating components themselves.
Further, once latched the latch 15b can transmit significant torque
as well as maintain axial coupling. In one embodiment, the latch
15b is employed to releasably couple or lock the rotor 13 of the PC
Pump 11 to the bearing assembly 14.
[0072] As shown in FIG. 3b, the latch 15b comprises a latch housing
60 adapted for connection to a first wellbore component such as the
bearing assembly 14. As shown in this embodiment, the latch housing
60 is connected at a top end 62 of the bearing assembly's shaft 42
through a threaded or other connection for co-rotation therewith.
The latch housing 60 has a bore 63. The plunger 61 is similarly
adapted for connection to the second wellbore component such as a
threaded or other connection to the lower end of a PC Pump rotor
13. The plunger 61 is sized to couple telescopically and axially
with the housing's bore 63. One of either the housing or plunger is
capable of at least limited rotation to permit some relative
rotation between the plunger and the housing. In this embodiment,
the coupling and releasing action of the plunger and the housing
impose rotational forces, causing the passive component to rotate.
In the PC Pump embodiment, one of the rotor 13 or the bearing
assembly 14 is capable of rotation, typically the housing freely
rotates with the bearing assembly in reaction to a rotational force
imposed by the plunger.
[0073] As shown in FIGS. 10a-11b, the plunger 61, having a diameter
less than an overall diameter of the latch housing 60, is
advantageously connected to the rotor 13 for facilitating passage
through the stator 16 with minimal interference. Where such
diametral restriction is not a factor the relative positions of the
plunger 61 and the latch housing 60 may be reversed. For ease of
discussion herein, unless otherwise specified, the context is
described with respect to the plunger being the uphole wellbore
component.
[0074] With reference to FIGS. 4 and 5, the latch 15b operates
using guided movement of one or more dogs 70, which extend radially
from one of either the latch housing 60 or the plunger 61, in a
track 80 which is formed in the complementary and opposing plunger
or latch housing 60 respectively.
[0075] In the illustrated embodiment of FIGS. 3c,4 and 5a, one or
more dogs 70 (three equidistant circumferentially-spaced dogs 70
shown) extend radially into the bore 63 of the housing with a
complementary radially extending track 80 being formed in the
plunger 61. In FIGS. 8 and 5b, each dog has a substantially
trapezoidal shape having an uphole leading edge 71 and a downhole
trailing edge 72. The leading edge 71 is angled and the trailing
edge 72 is also angled. In FIG. 5b, the trailing edge 72 is
optionally formed as an extended key 73 with substantially parallel
side edges 74 while retaining the angled trailing edge 72.
[0076] With reference to FIGS. 6a-e, the plunger 61 comprises a
tapered lower end 62. Best shown on FIG. 6c-6e, formed on an outer
surface of the plunger 61 is a plurality of radially outwardly
raised segments 63 spaced sufficiently circumferentially from one
another so as to form one or more entrances 64 corresponding to
each of the one or more dogs. Each entrance 64 to the track permits
a corresponding dog 70 to pass axially thereby to the track 80.
Three dogs 70, requiring corresponding three entrances,
automatically distributes loads such as torsional loads.
[0077] The track 80 is adapted to sequentially accept the one or
more dogs 70 through the entrances 64; guide and lock the dogs
therein and then release the dogs. Each entrance 64 leads to a
track's circumferential portion 80c bounded with a uphole cam 67,
proximal the entrances 64, and a downhole cam 69 spaced from the
entrances 64 and from the uphole cam profile 67. The uphole cam is
discontinuous, interrupted circumferentially by entrances 64.
[0078] The uphole and downhole orientations are for reference only,
pertinent for this embodiment, and could be inverted in other
embodiments.
[0079] Angled downhole faces 66 of the segments 63 guide the dogs
70 into their respective entrances 64. Uphole faces of the segments
form a discontinuous downhole cam 67, interrupted by the entrances
64. Spaced uphole from the downhole cam 67 is a shoulder 68 forming
an uphole cam 69. The uphole and downhole cams 69,67 are spaced
sufficiently apart to permit circumferential and stepwise movement
of the dogs 70 therebetween.
[0080] The downhole cam 67 guides each dog's trailing edge 72 and
the uphole cam guides each dogs' leading edge 71 through the
track's circumferential portion 80c. The track 80 enables
alternating the plunger 61 between a coupled position and a
released position. The uphole and downhole cams are formed with
angled faces complementary to each dog's leading and trailing edges
respectively.
[0081] The plunger and latch housing are in a coupled position
occurs in at least one instance when the plunger 61 is being pulled
axially way from the latch housing 60 wherein each dog's trailing
edge 72 engages the downhole cam 67 (tensile forces acting between
the plunger 61 and the latch housing 60). The plunger and latch
housing can be locked in a second instance when the plunger 61 is
engaged fully into the latch housing 60 and each dog's leading edge
71 engages the uphole cam 69 (compressive forces acting between the
plunger 61 and the latch housing 60).
[0082] More specifically, and with reference to the rolled-out view
of the plunger 61 and latch housing in FIG. 8 and the exploded
views of FIGS. 9a-9c, the sequence of operation on one typical dog
70 is illustrated as follows. The plunger 61 and attached rotor
(not shown) are lowered through the wellbore and stator until the
plunger encounters the latch housing 60.
[0083] As shown at A, in a first action, the plunger 61 is stabbed
into the housing (FIGS. 8,9a). Downhole force applied to the
plunger 61 results in engagement of each dog's leading edge 71 with
each segment's angled downhole face 66 causing relative rotation of
the latch housing 60 and plunger 61, typically causing the latch
housing 60 to rotate sufficiently to permit the dogs 70 to align
with and pass axially through each entrance 64, at B, and into the
circumferential portion 80c between the uphole and downhole cams
69,67.
[0084] With reference to FIGS. 8, 9b, each dog 70 engages the
uphole cam 69 for enabling indexed relative rotation from B to C,
and misaligning each dog 70 from an entrance 64 so that the dogs
cannot be directly released from the circumferential track portion
80c. Relative rotation stops when the dog 70 engages a first
rotational stop 81 formed in the uphole cam 69. At C, the leading
edge 71 of each dog 70 is positioned and restrained in a first
coupled position for locking the plunger 61 into compressive
coupling with the latch housing. Torque applied by the plunger 61
is capable of driving the latch housing 60. Typically, a rod string
21 is threadably connected and is capable of drivable RH rotation
without unthreading. Accordingly, in most instances, the rotational
stops and angled faces of the uphole and downhole cams are arranged
so as to provide driving surfaces. The orientation of angles is
dependent on which of the plunger and housing are driving and which
is being driven.
[0085] With reference to FIGS. 8, 9c, upon a second and subsequent
uphole action from C to D of the rotor 13 and plunger 61, such as
during downhole pumping, the plunger 61 moves uphole relative to
the dogs 70 to D, wherein the trailing edges 72 of the dogs 70
engage the downhole cam 67, guiding each dog 70 through indexed
relative rotation to a second rotational stop 82 so as to position
and restrain each dog's trailing edge 72 in a second coupled
position for locking the plunger 61 in axially tensile coupling
with the latch housing 60. In the embodiment of the PC Pump 11 and
rotor 13, this is the operational mode wherein the rotor 13 imposes
tensile loads for co-rotation with the latch housing 60, such loads
being further borne or restrained by the bearing assembly 14. In
this mode, the plunger 61, while under tensile loading can also
rotatably drive the latch housing 60.
[0086] In FIG. 8, one generic embodiment of a dog 70 and downhole
cam 67 are shown. This embodiment permits application of torque in
one direction only as the first and second rotation stops 81,82 are
unidirectional. In an optional embodiment, as shown in FIGS. 5b,6c
and 9c second rotational stop 82 is a pocket 82p forming a
bidirectional stop, having axial faces 77 for engaging the extended
key 73, with its parallel edges 74, in both directions. This
arrangement enables torque in both directions. Further, the
extended key 73 provides greater surface area and greater torque
capability.
[0087] In a third action from D to E, as shown further in the
general case of FIG. 8, when it is desirable to manipulate the
plunger 61 to the released position such as to disengage the rotor
13 from the bearing assembly 14 and to trip the rotor out of the
wellbore, one applies set down or downhole force to move the
plunger 61 downhole, guiding each dog's leading edge 71 for contact
with the uphole cam 69 at E, causing indexed relative rotation to a
third rotational stop 83 which misaligns each dog 70 from the
second rotational stop 82 and aligns each dog 70 with an angled
discharge face 78 on each segment's downhole cam 67.
[0088] In a fourth action, at F, uphole movement of the plunger 61
aligns each dog 70 once again with each entrance 64 for release of
each dog from the track 80 wherein each dog 70 and the plunger 61
telescope out of the latch housing 60 to be released at G.
[0089] Turning to FIG. 12, in a another more universal embodiment
of a releasable coupling, a latch assembly 89 is illustrated
comprising the described plunger 61 and the latch housing 60. The
plunger 61 is adapted with a more generic connector 90 having,
threaded ends 91 and wrench flats 92 being provided. Similarly, the
latch housing 60 is similarly fitted with threaded ends 93 and
wrench flats 94. In greater detail in FIGS. 13a-13c, such as
generic latching assembly is provided illustrating the equivalent
implementation of the dogs 70, segments 63 and cam profiles 67,69
although the uphole and downhole cam designations need not apply,
the assembly being operable in either orientation.
[0090] With reference to FIG. 14, an implementation of the latch
assembly 89 is illustrated in a PC Pump situation which could apply
the latch assembly 89 in either orientation whether the pump is
pumping liquids uphole or downhole. There is no longer any
requirement to connect the rotor to any specific one of the well
components as both the plunger 61 and latch housing 60 remain above
the PC Pump and are not diameter-restricted. In this embodiment,
the latch assembly 89 is required to convey torque from the drive
string 21 to the rotor. As shown in FIG. 15, in a further
illustration of the flexibility of the latch invention, the plunger
61 is shown as depending from the drive string 21 and the latch
housing 60 is connected to the rotor 13.
* * * * *