U.S. patent application number 10/155083 was filed with the patent office on 2003-12-04 for multi-chamber positive displacement fluid device.
Invention is credited to Gilbert, Denis, Struyk, Arnoud.
Application Number | 20030223896 10/155083 |
Document ID | / |
Family ID | 29582149 |
Filed Date | 2003-12-04 |
United States Patent
Application |
20030223896 |
Kind Code |
A1 |
Gilbert, Denis ; et
al. |
December 4, 2003 |
MULTI-CHAMBER POSITIVE DISPLACEMENT FLUID DEVICE
Abstract
A pump comprises multiple, axially stacked positive displacement
fluid device sections, such as circumferential piston pumps having
chambers and contra-rotating chambers. The device can be similarly
employed as a fluid motor. The stacked sections are arranged within
an outer retaining barrel in one or more stages. The pump is
particularly suitable for installation downhole in the casing of a
wellbore. Each section comprises a pair of rotors fit to shafts
which are rotatably supported on hard faced bearings between the
shafts and the bosses. Each pump section draws fluid from an inlet
port and discharges fluid to a common and contiguous discharge
manifold. The inlets of the pump sections for a suction stage
communicate with a fluid source. Cross-over sections route fluid
between stages. Successive pressure stages draw fluid from the
cross-over fit to the preceding stage's discharge manifold.
Inventors: |
Gilbert, Denis; (Airdrie,
CA) ; Struyk, Arnoud; (Calgary, CA) |
Correspondence
Address: |
SEAN W. GOODWIN
237- 8TH AVE. S.E., SUITE 360
THE BURNS BUILDING
CALGARY
AB
T2G 5C3
CA
|
Family ID: |
29582149 |
Appl. No.: |
10/155083 |
Filed: |
May 28, 2002 |
Current U.S.
Class: |
418/9 ; 418/1;
418/200 |
Current CPC
Class: |
F04C 13/008 20130101;
F04C 11/001 20130101; F04C 2/123 20130101; F04C 2240/70 20130101;
F04C 15/0019 20130101; F04C 2/18 20130101 |
Class at
Publication: |
418/9 ; 418/1;
418/200 |
International
Class: |
F01C 011/00 |
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. A multi-chamber positive displacement fluid device comprising:
at least two sections stacked axially together, each section having
a chamber for moving fluid from an inlet to a discharge, at least
one section having an inlet adapted for fluid connection to a fluid
source, and at least one section having its discharge adapted for
fluid connection to a fluid destination; a pair of parallel and
contra-rotating rotors operable in the chamber of each section for
displacing fluid from each chambers' inlet to its respective
discharge when rotated, the pair of rotors for each section being
aligned axially with the pair of rotors for each other section; a
drive shaft extending axially and rotatably into each chamber for
rotating one rotor of the pair of rotors in each section; an idler
shaft parallel to the drive shaft and extending axially and
rotatably into each chamber for the other rotor of the pair of
rotors; and timing means between the drive shaft and idler shaft
for contra-rotating the drive and idler shafts and the pair of
rotors.
2. The positive displacement fluid device of claim 1 wherein fluid
is driven from the fluid source to the fluid destination for
fluidly driving the pair of rotors so as to motor the drive
shaft.
3. The positive displacement fluid device of claim 1 wherein the
fluid device is a pump and the chambers are rotor chambers and
wherein the drive shaft is driven for contra-rotating the pair of
rotors so as to cause fluid to be pumped through the rotor chambers
from the fluid source to the fluid destination.
4. The positive displacement pump of claim 3 wherein each of the
pair of rotors comprises a circumferential piston, further
comprising: a pair of bosses extending into each rotor chamber,
each boss having a cylindrical bore for rotatably passing the drive
and idler shafts; and bearings fit into the bore of each boss for
rotatably supporting the drive and idler shafts.
5. The positive displacement pump of claim 4 wherein the bearings
are complementary facing hard bearing surfaces in the boss and on
the drive and idler shafts.
6. The positive displacement pump of claim 5 wherein the
complementary facing hard bearing surfaces are manufactured from
material selected from the group consisting of tungsten carbide,
silicon carbide and ceramics.
7. The positive displacement fluid device of claim 3 wherein at
least one section is a suction stage and at least one section is a
pressure stage further comprising a cross-over section sandwiched
between the suction and pressure stages for fluidly connecting the
discharge of suction stage to the inlet of the pressure stage.
8. The positive displacement fluid device of claim 7 further
comprising seals sandwiched between each suction section, each
crossover section and each pressure section.
9. The positive displacement fluid device of claim 3 further
comprising: at least one suction stage having one or more suction
pump sections stacked together, the discharges of which are fluidly
connected to form a discharge manifold; at least one pressure
stage, each having one or more pressure pump sections stacked
together, the inlets of each pressure pump section being fluidly
connected to form a suction manifold and the discharges of which
are connected to form a discharge manifold; and a cross-over
section sandwiched between the suction stage and each successive
pressure stage, the cross-over section having passage for fluid
connection of each stage's discharge manifold to the suction
manifold of each successive pressure stage.
10. The positive displacement fluid device of claim 9 wherein two
or more pressure stages are stacked successively together, further
comprising a cross-over section sandwiched between each successive
stage, the cross-over section having a passage for fluid connection
between one pressure stage's discharge manifold and the successive
pressure stage's suction manifold.
11. The positive displacement fluid device of claim 9 further
comprising: a tubular housing having a wall and a bore, the one or
more suction stages, one or more cross-over sections and one or
more pressure stages being sandwiched sealingly together and housed
within the bore, the housing being adapted for immersion in the
fluid source; inlet ports formed in the wall corresponding to and
in fluid communication with each of the inlets of the at least one
suction section; and a discharge port in fluid communication with
the discharge of the pressure stage and with the fluid
destination.
12. The positive displacement fluid device of claim 9 further
comprising: a tubular housing having a wall and a bore, the one or
more suction stages, one or more cross-over sections and one or
more pressure stages being sandwiched sealingly together and housed
within the bore, the housing being adapted for immersion in the
fluid source; a suction manifold which fluidly connects the inlets
of the suction sections in the suction stage; an inlet port in
fluid communication with the suction manifold of the suction stage;
and a discharge port in fluid communication with the discharge of
the pressure stage and with the fluid destination.
13. The positive displacement fluid device of claim 4 wherein as
the drive shaft rotates, the first and second rotors of each
pumping section rotate and each pumping section discharges fluid
pulses according to the angular position of the rotors and wherein
the first rotor of two or more of the pumping sections are
angularly incremented on the drive shaft so that discharge pulses
from the two or more pumping sections occur at different angular
positions of the drive shaft; and a cross-over section sandwiched
between each successive stage, the block having passage for fluid
connection between one pressure stage's discharge manifold and the
successive pressure stage's suction manifold.
14. The positive displacement fluid device of claim 13 wherein each
pump section further comprises: a pump housing forming a rotor
chamber and a discharge chamber; first and second end plates for
enclosing the rotor chamber and at least one of the end plates
between adjacent pump housings having a discharge chamber which is
in communication with the discharge chamber of the pump housing for
forming a discharge manifold; first and second cooperating rotors
operable in the rotor chamber to displace fluid from the inlet to
the discharge chamber of the pump housing and to discharge
manifold.
15. The positive displacement pump of claim 14 further comprising:
a drive shaft extending through at least one end plate for rotating
one rotor; an idler shaft extending through the at least one end
plate which is driven by the drive shaft for rotating the other
rotor; and timing means between the drive shaft and idler shaft for
contra-rotating the first and second rotors so that they cooperate
to pump fluid.
16. The positive displacement fluid device of claim 15 wherein the
rotors are first and second circumferential pistons mounted for
co-rotation with the drive shaft and idler shaft, further
comprising: first and second bosses extending from an end plate,
the first and second rotors being positioned in the rotor chamber
and about the first and second bosses for pumping fluid through the
rotor chamber; and bearings rotatably supporting the drive and
idler shafts in the bosses.
17. The positive displacement fluid device of claim 16 wherein the
bearings are complementary facing hard bearing surfaces.
18. The positive displacement fluid device of claim 17 wherein the
complementary facing hard bearing surfaces are manufactured from
material selected from the group consisting of tungsten carbide,
silicon carbide and ceramics.
19. The positive displacement fluid device of claim 18 further
comprising a cross-over section between the discharge of the at
least one suction pump section and the inlet of the at least one
pressure pump section.
20. The positive displacement fluid device of claim 19 wherein the
seals comprise high temperature O-ring seals.
21. A multi-stage positive displacement pump comprising: a suction
stage having one or more axially stacked positive displacement
suction pump sections, each suction pump section having a rotor
chamber for pumping fluid from an inlet adapted for connection to a
fluid source to a discharge manifold; at least one pressure stage,
each stage having one or more stacked positive displacement
pressure pump sections, each pressure pump section having a rotor
chamber for pumping fluid from a suction manifold to a discharge
manifold adapted for connection to a fluid destination; a crossover
section for fluidly connecting the discharge manifold of the
suction stage to the suction manifold of the pressure stage; and
drive means extending axially into each suction pump section and
into each pressure pump section which rotates for moving fluid from
the fluid source to the fluid destination.
22. The positive displacement fluid device of claim 21 further
comprising: a tubular housing having a wall and a bore, the suction
stage, cross-over section and pressure stage being sandwiched
sealingly together and housed within the bore, the housing being
adapted for immersion in the fluid source; an inlet port formed in
the wall of the housing and corresponding to each pump section, the
inlet ports being in fluid communication with each pump section
inlet; and a discharge port formed in the housing and in fluid
communication with the discharge of the pressure stage and with the
fluid destination.
23. The positive displacement fluid device of claim 21 further
comprising: a pair of cooperating rotors operable in the rotor
chamber of each section for displacing fluid from the inlet to the
discharge when rotated; and wherein the drive means comprises: a
drive shaft extending rotatably into the chamber of each section
for rotating the first rotors of each section, an idler shaft
extending rotatably into each rotor chamber for rotating the second
rotors of each pumping section, and timing means between the drive
shaft and idler shaft for contra-rotating each of the rotors.
24. A method of pumping fluid comprising the steps of: providing at
least two positive displacement pump sections, each pump section
having at least two rotors in a rotor chamber and each rotor being
rotational about an axis for pumping fluid from a fluid suction to
a fluid discharge; stacking each pump section axially and sealably
together so that so that the respective axes of the rotors align
and the discharges form a contiguous discharge manifold; driving
the rotors of each pump section with a timed drive shaft and
cooperating idler shaft each of which extend axially and drivably
through the axis of each rotor of each pump section so, that when
the rotors are rotated, the pump sections draws fluid through their
inlets and discharges the fluid through the discharge manifold.
25. The method of claim 24 further comprising: providing a
cross-over section which, when sandwiched between two pump
sections, fluidly connects the discharge of a pump section to the
inlet of a successive stacked pump section; forming a suction stage
by stacking each pump section within the suction stage so that the
respective axes of the rotors align and the discharges forming a
contiguous discharge manifold; forming a pressure section by
stacking each pump section within the pressure stage so that the
respective axes of the rotors align and also align with the axes of
the rotors of the suction section, the inlets form a contiguous
suction manifold and the discharges forming a contiguous discharge
manifold; drawing fluid through the inlets of each pump section in
the suction stage and discharging the fluid through the discharge
manifold, through the crossover section to the suction manifold of
the pressure stage.
Description
FIELD OF THE INVENTION
[0001] This invention relates to positive displacement fluid
devices such as fluid-driven motors and pumps which are operable
for pumping high temperature, and contaminated fluids. More
particularly, such a fluid device is a circumferential piston pump
or motor configured for multi-chambered use in stacked and
multi-stage operation.
BACKGROUND OF THE INVENTION
[0002] Conventional methods and apparatus for bringing well fluids
to the surface involve various pump systems of different designs
and methods of operation. Restrictions on existing pump systems
sometimes include dimensional constraints, the ability to handle
high temperature and the need to pump contaminated fluids, e.g.
high sand content particularly at high temperature. Conventional
pumps are limited by their use at high temperature and with
contaminant sensitive polymers.
[0003] Further, pumps having rotating components must have some
form of bearing to separate the moving from the stationary
components. It is a constant challenge to maintain bearing
integrity in high temperature or contaminated environments. Such
environments include those typical in the recovery of high
temperature hydrocarbons from Steam Assisted Gravity Drainage
(SAGD) wells in the heavy oil and bitumen recovery of northern
Alberta, Canada.
[0004] In downhole operations, such as conventional oil recovery
operations, progressive cavity (PCP) pumps have been applied to
great effectiveness. However, as the well becomes deeper, as the
temperature increases, and as the level of contamination increases,
the elastomers used begin to fail resulting in pump failure and
more frequent and expensive turnovers.
[0005] As an alternative, one may consider positive displacement
pumps which are applied in food and other fluid industries. Among
this class of pumps are circumferential piston pumps which have
been known since at least 1935 in U.S. Pat. No. 2,096,490 to Hanson
and still in production today by Waukesha Delavan, Wis. (Universal
II Series) and Tuthill of Alsip, Ill. (HD Series). Conventional
circumferential piston pumps utilize opposing, contra-rotating
rotors having pistons which are alternately swept through a common
chamber. Timing gears coordinate the rotor rotation. Traditionally
used in surface applications, significant effort has been applied
in order to seal the rotation of the rotors and the resulting pumps
to date have been typically used in single stage applications. The
rotors are each fitted on a shaft rotatably supported on bearings,
either cantilevered or being fit with bearings at each end. The
bearings are lubricated and separated from the process fluids by
seals (commonly known as external bearings).
[0006] The usual approach for increasing the volume and fluid flow
rate from such positive displacement pumps has been to increase the
pump's dimensions. However, in the restricted space of a wellbore,
such dimensional scale-up of pumps is not suitable for providing
either the necessary pressure or the flows in the wellbore.
[0007] In some applications, such as hot, contaminated downhole
wellbore operations, there is an objective to increase either the
volumetric flow rate or to increase the output pressure beyond that
which can conventionally be provided using a conventional
circumferential piston pump. Conventional pump technology has not
fulfilled these objectives. The design challenges are further
increased where the fluid is hot and contaminated, further
affecting the challenge of sealing the rotors of such pumps. In
particular, in the high pressure, high temperature contaminated
environment of oil well downhole operations, there is little
opportunity to provide an optimum environment for the bearings.
[0008] The above problems and challenges are equally applicable to
the reverse operation in which fluid is forced through such devices
so as to drive a shaft and act as a motor.
[0009] Accordingly, there is a need for a fluid device which can
operate in high temperature, contaminated fluids and which can be
further adapted to operate in high volume and pressure operations,
even in such restricted spaces as a wellbore.
SUMMARY OF THE INVENTION
[0010] The invention provides an improved positive displacement
fluid device, such as a pump, having one or more pump sections, the
pump sections being adapted for axial stacking which enables high
volume, high pressure transport of high temperature production
fluid which can contain a substantial degree of contamination. The
novel pumping system overcomes the high temperature limitation as
well as being associated with a high tolerance to pump contaminated
fluids over a wide viscosity range. The capability to pump high
temperature, contaminated fluids is achieved using a
circumferential piston pump utilizing a novel sealing arrangement.
Further, pump sections are stacked in parallel to achieve required
flow rates. The parallel stacked pump sections are in turn stacked
in series to meet required discharge head or pressure. Configured
as a pump, the fluid device is driven by a drive shaft for pumping
fluid. Configured as a motor, fluid is forced through the sections
for turning and driving the shaft. Herein, the specification
concentrates on a description of the fluid device as a pump
although the principle and inventive concepts apply equally to a
motor configuration.
[0011] In a preferred pumping configuration, the invention is a
multi-chamber positive displacement fluid device or pump comprising
two or more stacked positive displacement pump sections, each pump
section having a rotor chamber for pumping fluid from an intake
adapted for communication or connection with a fluid source to a
discharge manifold and through a fluid discharge adapted for
communication or connection to a fluid destination. Each rotor
chamber contains rotors driven by common timed drive and idler
shafts extending axially through each stacked rotor chamber. Each
of the stacked sections has a common discharge manifold which
contributes its incremental flow to the common discharge manifold.
The sections can be stacked in any combination of parallel or
series arrangements, each of which utilizes a drive shaft which
extends co-axially through the stack of sections.
[0012] If the sections are stacked in parallel, the volumetric flow
rate is incrementally increased.
[0013] If the sections are stacked in series, the discharge
pressure capability is incremented. For a series arrangement, the
discharge of one section or stack of sections is fluidly connected
to the inlet of a successive stacked section through a crossover
section. Sections stacked in series with a cross-over form a
pumping stage for incrementally increasing the pressure at the
fluid destination.
[0014] Applied as a motor for a given flow rate of fluid, sections
stacked in parallel result in a greater torque at the drive shaft
and sections stacked in series result in a greater rotation
speed.
[0015] In a multi-section pump, the invention comprises: two or
more axially stacked pump sections, each section having a rotor
chamber and associated rotors for pumping fluid from an inlet to a
discharge manifold and a drive which extends axially through each
rotor chamber for rotating the rotors and pumping fluid. Each
section comprises a pump housing for housing the rotor chamber and
rotors which are sandwiched between end plates and seals.
[0016] In a multi-stage pump, the invention comprises: a suction
stage have having one or more axially stacked suction pump
sections, each section having a rotor chamber and associated rotors
for pumping fluid from an inlet to a discharge manifold; and at
least one pressure stage, each stage having one or more stacked
pressure pump sections, each pressure pump section having a rotor
chamber for pumping fluid from a suction manifold to a discharge
manifold; a crossover section for fluidly connecting the discharge
manifold of the suction stage to the suction manifold of the
pressure stage; and a drive which extends axially through each
rotor chamber for rotating the rotors and pumping fluid.
[0017] More preferably, the drive comprises a drive shaft or a
plurality of coaxially connected drive shafts extending axially and
rotatably to the rotor chamber of each section for rotating one of
the rotors; an idler shaft or idler shafts extending rotatably to
each rotor chamber for rotating the other rotor; and timing means
between the drive shaft and idler shaft for contra-rotating the
rotors.
[0018] The entire stack of sections and crossovers between stages
can be fit into the bore of a tubular barrel, compressed sealably
together and retained therein, the barrel forming a pump having a
fluid intake or inlet ports to a suction stage and having a fluid
discharge from a pressure stage.
[0019] Such a pump has great versatility in its designed flow
capacity and lift, all of which can be assembled into a small
diameter package and which is driven through a single drive shaft
connection; ideal for downhole operations or other space
restrictive areas. Configured as a motor, the fluid device
demonstrates similar same space and performance advantages in
meeting desired output torque and rotational speed
characteristics.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIGS. 1a-1e are schematic views of the sequential operating
principles of a circumferential piston pump;
[0021] FIG. 2 is an exploded perspective view of a multi-stage
circumferential piston pump according to one embodiment of the
invention;
[0022] FIG. 3 is a perspective view of an alternate suction stage
according to another embodiment, in which the inlets ports for all
pump sections draw from a common suction manifold;
[0023] FIG. 4 is an exploded perspective view of a pump section
configured as a fluid suction section;
[0024] FIG. 5 is an exploded perspective view of a four parallel
pressure pump fluid suction sections of FIG. 5, detailing main
drive shaft and idler shaft sections;
[0025] FIG. 6 is an exploded perspective view of a pump section
configured as a pressure pump lift section;
[0026] FIG. 7 is an exploded perspective view of four parallel
pressure pump lift sections of FIG. 6, detailing main drive shaft
and idler shaft sections;
[0027] FIG. 8 is an exploded perspective view of a center timing
gear assembly;
[0028] FIGS. 9a-9d are various views of a fluid cross-over unit.
More particularly, FIG. 9a is a perspective view with internal
passageway depicted in hidden lines, FIG. 9b is top view of FIG.
9a, FIG. 9c is a cross-sectional view of FIG. 9b along lines A-A,
and FIG. 9c is a cross-sectional view of FIG. 9b along lines
B-B;
[0029] FIG. 10 is an exploded perspective view of a top bearing
assembly;
[0030] FIG. 11 is an exploded perspective view of a complete pump
assembly with outer retaining barrel omitted; and
[0031] FIGS. 12a-12c are test results depicting the efficiency,
power and torque curves for a five section portion of a pump
constructed according to the embodiment of FIG. 2 when pumping
water at standard conditions;
[0032] FIGS. 13a-13c are test results according to FIGS. 12a-12c,
also depicting the efficiency, power and torque curves when pumping
SAE30 oil at 70.degree. C.; and
[0033] FIGS. 14a-14c are test results according to FIGS. 12a-12c,
also depicting the efficiency, power and torque curves when pumping
SAE30 oil at 190.degree. C.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0034] The principles of positive displacement pumps are hereby
adapted and modified for operation in environments known to be
challenging to current pumping technologies. Positive displacement
pumps include rotary-actuated gear pumps and circumferential piston
pumps. When fluid operated in reverse, a positive displacement
device can be used as a motor. Unless the context is specifically
otherwise, the description herein applies equally to operation as a
pump or as a motor.
[0035] In one embodiment a circumferential piston pump is applied
to overcome the pumping challenges identified by the applicant. The
principles of circumferential piston pumps are well known and are
summarized briefly herein for reference.
[0036] Generally, and using illustrations of a circumferential
piston pump as an example (FIGS. 1a-1e), a positive displacement
pump comprises at least a rotor chamber 10, rotors 11 fitted into
the rotor chamber, a fluid inlet 6 and a fluid discharge 7. In a
single stage implementation, the inlet 6 is connected to a fluid
source and its discharge 7 is connected to a fluid destination. In
the case of an elementary gear pump, two rotors 11 such as meshing
gears are rotated in the rotor chamber 10. The rotors 11,11 are
contra-rotated for effective fluid flow--either being driven by the
fluid as is the case for a motor, or driving the fluid as a
pump.
[0037] Specifically for a circumferential piston pump, two
contra-rotating piston rotors 11,11 are rotated in the rotor
chamber 10 about cylindrical machined bosses 12. Annular piston
bores 14 are formed between the rotor chamber 10 and the bosses 12.
Each rotor 11,11 has one or more arcuate pistons 15 which travel in
circular paths in their respective annular piston bores 14. The
piston bores 14,14 meet at a common point of intersection C in the
center of the rotor chamber 10. The center of rotation of each
rotor is spaced outside of the major diameter (sometime known as
external) of the opposing rotors. The point of intersection C of
the piston bores 14,14 is connected at one side to the pump's inlet
6 and at an opposing side to the pump's outlet 7. Each piston 15
alternates passing through the point of intersection C. Each piston
15 has a trailing edge and a leading edge. As the trailing edge of
a rotor's piston 15 leaves the point of intersection C, the volume
of its piston bore is steadily yet temporarily increased, causing a
suction and a resulting inflow of fluid from the inlet 6 or suction
side. This is the suction portion of the cycle of each rotor 11.
The leading edge of the same piston 15 then seals the piston bore
14 which traps the fluid drawn from the inlet 6 and positively
displaces it to the outlet 7 or discharge side. While one rotor's
piston 15 is displacing fluid out of its piston bore 14, the other
rotor's piston 15 is drawing fluid into its piston bore 14. The
suction inlet 6 and discharge outlet 7 are constantly isolated,
despite the common point of intersection C, due to the continual
presence of one rotor 11 or the other rotor 11 sealing between its
respective piston bore 14 and against the opposing rotor's
cylindrical boss 12.
[0038] In example sequential steps of operation, starting at FIG.
1a, an Open-to-inlet (OTI) volume is defined in a rightmost rotor
bore 14 by the rotor chamber 10 and by the departing the rightmost
rotor piston 15. The rightmost rotor piston 15 fluid seals the OTI
volume at the point of intersection C where the piston meets and
seals against the opposing rotor's cylindrical boss 12. Comparing
FIG. 1a and 1e, the OTI volume alternates between the piston bores
14,14 as the pistons 15,15 alternately enter or leave the point of
intersection C. Normally, neither the rotors 11,11 nor the pistons
15,15 contact each other and only close tolerance fluid seals exist
between the rotor 11 and the opposing rotor's boss 12. As the
rightmost rotor bore 14 forms the OTI volume (FIG. 1a), an
Open-to-Outlet (OTO) volume is defined in the leftmost rotor bore
14 by the rotor chamber 10 and the surfaces of rotor pistons 15
between their fluid seal contacts with the opposing boss 12 where
they leave the point of intersection C. Observing the rightmost
piston 15, FIGS. 1a and 1b illustrate the OTI suction portion of
the cycle, while FIG. 1c illustrates the trapping of the fluid and
its positive displacement towards the OTO volume. FIGS. 1d and 1e
illustrate the continuous discharge of the trapped fluid to the
outlet 7. As is shown in FIG. 1c, the OTI suction cycle for the
leftmost rotor 11 begins when the rightmost rotor 11 is completed
its OTI cycle.
[0039] In the conventional mode of operations, radial surfaces and
axial-end surfaces of the rotor pistons 15 run in close-clearance
contact with the walls of the rotor chamber 10, and due to the
reality of manufacturing tolerances, load-bearing contact may
occasionally occur in these zones. Annular apertures defined by the
running clearances therebetween determine the amount of fluid
leakage from the outlet 7 to the inlet 6, being from the OTO volume
to the OTI volume, for a given pressure difference and a given
effective viscosity. For each rotor chamber 10, each rotor 11,11
alternately supports the driving torque.
[0040] This ends a review of the more conventional aspects of the
circumferential piston pump, the principles of which are common
with positive displacement pumps generally and with the present
invention. Such conventional pumps utilize a pump body or housing
having a single inlet 6 and an outlet 7. The typical means for
increasing a pump's volume (OTI,OTO) and fluid flow rate has been
to increase the pump's dimensions. However, in the restricted space
of a wellbore, such dimensional scale-up of pumps is not suitable
for providing either the necessary pressure or the flows in the
wellbore.
[0041] Therefore, with reference to FIGS. 2 for the overall
arrangement and FIGS. 4 and 5 for details, and turning to a first
embodiment of the present invention, a novel pump 20 comprises two
or more positive displacement chambers 10,10 . . . , stacked
axially one chamber 10 atop another chamber 10. Each chamber 10 is
provided with its respective rotors 11,11, bosses 12,12 and an end
plate 13 for forming a section 21. In stacking the sections 21 and
thus stacking the chambers 10,10 . . . , the respective rotors
11,11 of each discrete chamber 10 are aligned along the same axes
and can thereby be driven through a common drive shaft and idler
shaft.
[0042] Two or more stacked sections 21 having their outlets 7
conjoined into a common discharge are stacked to form a pump stage
22. A pump 20 can merely have a single stage 22 of one or more
parallel stacked sections 21. Practically however, for increased
head or discharge pressure, a pump 20 preferably comprises two or
more stages; a suction stage 22s (FIGS. 4 and 5) and at least one
pressure stage 22p (FIGS. 6 and 7).
[0043] Each stage 22, whether suction or pressure 22s,22p,
comprises one or more pump sections 21 arranged or stacked axially
in parallel for obtaining the desired capacity or fluid flow rates.
Stages 22 can also be stacked axially in series 22s,22p,22p, . . .
for obtaining the desired discharge pressure from the ultimate
outlet from the pump 20.
[0044] As shown in FIG. 2, a complete pump 20 consists of pump
sections 21 combined in multiples in a stack 23 and preferably
having two or more stages 22 operating in series 22s,22p,22p.
[0045] The stack 23 of pump sections 21 and drive components
(described later) are sandwiched together for fluid tight
connections therebetween. While other means such as threading
section 21 to section 21 together or joining by fasteners could be
employed, one convenient means for assembling a multiplicity pump
sections 21 and their associated drive components is to fit the
stack 23 into an outer cylindrical retaining barrel 24. The length
of the outer retaining barrel 24 is complementary to the overall
height of the stack 23 so that when installed into the outer
retaining barrel, end retaining nuts 25 are secured into each end
of the outer retaining barrel 24 for engaging the stack ends 26 and
retaining them together.
[0046] While each section 21 may actually be identical, the
section's location in the stack can define its role as either a
suction or a pressure section 21s,21p. A suction section 21s,
multiple sections 21s,21s . . . , or a suction stage 22s is located
adjacent to and in fluid communication with a fluid source and
draws the design flow rate of fluid into the pump 20. As shown in
FIG. 2, such a suction stage 22s, can draw fluid independently into
each section 21s,21s . . . through a plurality of corresponding
inlets 6,6 . . . in the sections 21 and corresponding inlet ports
27 in the outer retaining barrel 24. Alternately, as shown in FIG.
3, the fluid can be drawn through a combined suction intake 34.
[0047] With reference to FIG. 4, a section 21s configured for
suction is illustrated. Each section 21 comprises a pump body or
pump housing 30 forming at least two chambers: a pumping or rotor
chamber 10 and a discharge chamber 31. For ease of manufacture and
assembly, the rotor chamber 31 of each section 21 is sandwiched and
sealed between end plates 13. A pair of bosses 12 extends from one
side of the end plate 13 and project into the rotor chamber 10. The
end plate 13 blocks one side of the rotor chamber 10, shown in this
configuration as a top end plate for one pump section while also
forming a bottom end plate for the next adjacent pump section. At
an extreme bottom end of a stack of pump sections, a termination
plate 32 without bosses is provided.
[0048] With reference to FIG. 5, four suction pump sections 21s are
shown with the discharges 31 of each of the pump housings 30 and
end plates 13 being aligned for forming a discharge manifold 31m
for contiguous fluid passage therethrough. Inlets 6 are shown
extending from the rotor chamber and through the pump housing 30.
The pump housing, may or may not have a suction chamber 33 which
mirrors the discharge chamber 31. In this embodiment, a suction
chamber 33 would be a mere artifact of the implementation of pump
housings which are interchangeable for either suction or pressure
section use. As shown in FIG. 2, the assembled suction stage 22s
draws fluid from a fluid source outside the pump 20, typically from
a wellbore. Fluid enters the suction stage through a series of
inlet ports 27 formed in the outer retaining barrel 24. The inlet
ports 27 align with corresponding inlets 6 in each of the suction
stages 21s; typically one inlet port 27 per suction pump section
21. While this arrangement does require some accuracy in matching
inlet ports 27 and pump section inlets 6, use of individual inlet
ports 27 does minimize fluid restriction and ensures a
substantially equal supply of fluid to each pump section 21. Each
suction pump section 21 transports substantially an equal amount of
fluid from the inlet 6 and delivers it to the common discharge
manifold 31m which is located 180 degrees opposite to the suction
manifold 33m. The discharge manifold 31m runs along the full axial
length of each pump stage 22s,22p . . . , through both the pump
housings 10 and the end plates 13 for accumulating and delivering
the discharge fluid to the next pump stage 22.
[0049] In the alternate embodiment shown in FIG. 3, the
multiple-stacked chambers of the suction stage 22s can all draw
from suction intake 34. The suction sections 21s,21s . . . have
their inlets 6 extending only from the rotor chamber 10 to a
suction chamber 33 as part of an overall common suction manifold
33m. This simplifies the pump assembly and avoids the need to
accurately align individual section inlets 6 with the inlet ports
27 in the outer retaining barrel 24. Accordingly, a common or
combined suction intake 34 is formed at the initial suction section
21s or the suction stage 22s. The intake 34 is formed in the
termination plate 32. In this embodiment, the suction manifold 33m
is required to pass the entire design fluid flow rate, and thus the
pressure drop therethrough must be considered in the design such as
increasing the manifold 33m cross-section accordingly. The suction
manifold 33m may have sufficient cross-sectional areas to supply
fluid to all of the multi-chambers 10 in the stage 22 without
starving the latter sections 21 of fluid flow. The suction manifold
33m for all pump sections 21 may be increased in size. The inlets 6
for each section 21 are all joined through the common suction
manifold 33m. In the alternate embodiment in FIG. 3, it is clear
that the pressure and suction sections 21p,21s may be identical for
simplification and economy of manufacture.
[0050] Turning to FIG. 6, a pressure pump section 21p is shown
herein as differing from an independent inlet operating suction
pump section 21s by the absence of an inlet 6 extending through the
pump housing 30 which forms a suction manifold 33. As shown
individually in FIG. 6 and stacked in FIG. 7, the pressure pump
sections 21p correspond in all other respects to the suction pump
sections 21s set forth in FIGS. 4 and 5 except that the suction
chamber 33 now forms the inlet to each section 21. The suction
chamber 33 is isolated from the outer retaining barrel 24 and is
enclosed wholly within the pump housing 30. A pressure stage 22p is
typically configured to accept fluid from the suction stage's
common discharge, process the fluid through the one or more
sections 21p in parallel and also discharge the fluid through a
common discharge 31 or manifold 31m.
[0051] The end plates 13 are also fitted with suction and discharge
chambers 33,31 which are complementary to the pump housing's
suction and discharge chambers 33,31 for forming respective suction
and discharge manifolds 33m,31mextending continuously along the
pump 20 for contiguous fluid communication between stacked pump
stages 22s,22p,22p . . . As noted above, end plates 13 throughout a
suction stage 22s may or may not include a suction chamber 33 as
the suction section's pump housing 30 may be absent such a chamber,
being fitted only with an inlet 6.
[0052] With reference to FIG. 7, four pressure pump sections
21p,21p . . . are shown with each of the respective suction and
discharge manifolds 33,31 of the pump housings 30 and end plates 13
being aligned for contiguous fluid passage therethrough.
[0053] Rotors 11 and their pistons 15 are mounted rotatably over
the bosses 12 for rotation in the rotor chamber 10. Single lobed
rotors 11 are shown although double lobed or other rotor
arrangements are possible. In U.S. Pat. No. 2,642,808 to Thomas,
the entirety of which is incorporated herein by reference,
double-lobed rotors are implemented. Further, the circumferential
piston 15 can extend axially from the rotor 11 to overhang the boss
12, as illustrated herein, or can be cantilevered, as taught by
Thomas.
[0054] Accordingly, and referring to FIGS. 2 and 4-7, when
assembled into a typical pump 20 configuration, a suction stage 22s
is demonstrated as having fifteen stacked suction pump sections 21s
and fifteen corresponding inlet ports 27. All fifteen suction pump
sections 21s discharge to the common discharge manifold 33m. The
fluid in the suction stage's discharge manifold 31m is directed to
a first pressure stage 22p. The first pressure stage 22p is also
illustrated as having fifteen stacked pressure pump sections 21p.
All fifteen pressure pump sections 21p draw from a common suction
manifold 33m and discharge to a common discharge manifold 31m. The
fluid in the first pressure stage's discharge manifold 31m is
directed to a second pressure stage 22p. The second pressure stage
22p is also illustrated with fifteen pressure pump sections 21p.
All fifteen pressure pump sections 21p also draw from a common
suction manifold 33m and discharge to a common discharge manifold
31m.
[0055] Turning to FIGS. 7 and 8, one rotor 11 is driven by one or
more drive shafts 40,40 . . . which extend through each rotor
chamber 10 and which are connected end to end for co-rotation. The
opposing rotor 11 is driven by one or more idler shafts 41,41 . . .
which are also connected end to end for co-rotation. The one or
more drive shafts 40 and one or more idler shafts 41 are
hereinafter referred to collectively and simplistically as singular
drive shaft 40 and idler shaft 41 respectively.
[0056] As shown in FIGS. 7 and 8, the pump sections 21 are driven
using the drive shaft 40, extending axially through each pump
section 21 and connecting driven rotors 11 in each stacked pump
stage 22. The rotors 11 in each pump stage 22 rotate in the same
contra-rotating directions as they are driven by one common input
main drive shaft 40. The opposing rotor 11 in each pump section 21
is driven by paired sets of timing gears 50, connected to the drive
shaft 40 and the parallel idler shafts 41. The plurality of
discontinuous, yet co-axial, conjoined idler shafts 41 each being
driven through the timing gears 50. The timing gears 50 have a dual
function: to drive the idler shaft 41 and their associated rotors
11, and to ensure that the rotors' pistons 15 are timed correctly
so that they do not contact or clash.
[0057] A person of skill in the art can design one or more shafts
40,40 . . . and 41,41 . . . for assembly into a single co-rotating
shaft 40 or 41. As shown in FIG. 7, an individual shaft 40 or 41
may be conjoined at splined connections 42 at its respective and
common rotor 11. For example, the ends of the shafts 40,41 can be
fitted with an external involute spline 42 which fits cooperatively
with an internally splined coupling bushing (or rotor 11 or gear
50) to co-axially connect the shaft sections of each of the stacked
pump stages 22. Further, as shown in FIG. 8, the shafts may be
conjoined with splined connections at the timing gears 50.
[0058] The timing gears 50 are housed in timing assemblies 51,51 .
. . which are located at regular intervals between multiple stacked
pump sections 21, and thereby provide accurate timing for the
piston sections 21,21 . . . . Typically, a timing assembly 51 is
sandwiched between every four of five pump sections 21. The timing
gears 50 are contained in separate timing assemblies 51, fully
integrated in each pump stage 22.
[0059] Regardless of the form of connection to a fluid source, the
common discharge manifold 31m of the suction stage 22s delivers
pumped fluid to the next successive pump stage 22, in this case
being the first pressure pump stage 22p. The first pressure stage
22p and successive pressure pump stage 22p is similar in design and
construction to the previous suction pump stage 22s, excluding the
suction inlets 6 and inlet ports 27.
[0060] At the discharge of each stage 22, such as between the
suction stage 22s and a pressure stage 22p, the discharge manifold
31m is routed to the suction manifold 33m of the successive pump
stage. In order to maintain common rotational axes for the drive
shaft 40 and idler shaft 41, and to pump the discharge flow to the
common suction manifold 33m of the successive stage 22p, the fluid
needs to crossover 180 degrees to flow into the common suction
manifold 22s of the successive stage 22.
[0061] With reference to FIGS. 2 and 9a-9d, a fluid flow cross-over
section 60 comprises a cylindrical block forming an end wall 61 for
blocking the preceding stage's suction manifold 33m and a fluid
inlet 62 for accepting fluid flow from the preceding stage's
discharge manifold 31m. The fluid from the preceding stage's
discharge manifold 31m is routed through a fluid flow passage 63 to
a fluid outlet 65. The fluid outlet 65 is arranged for discharge
into the suction manifold 33m of the successive stage 22. As shown
in FIGS. 9b and 9d, the cylindrical block is fitted with a bore 66
for forming a through passage for the drive shaft 40. The idler
shafts 41, being driven by timing assemblies 51 positioned
periodically along the pump, are able to terminate either side of
the cross-over section 60. Accordingly, the fluid flow passage 63
is neither obstructed nor interrupted by the drive shaft 40 or
idler shafts 41,41.
[0062] Sockets 67 and bearings (not shown) are provided for the
termination of a preceding idler shaft and for the termination of a
successive idler shaft. Such sockets 67 can be machined into the
cross-over section 60 or into specialized end plates (not shown)
which can be provided as matter of economics so as to avoid further
machining of the cross-over section 60.
[0063] As known by those of skill in the art of positive
displacement pumps, each rotor 11,11 is rotated in close
non-contacting tolerance to their respective bosses 12,12 and to
the rotor chamber 20 and the opposing rotor 11 so as to effect a
positive displacement motoring or pumping action. To maintain such
operational tolerances, the rotors 11,11 are mounted securely to
their respective shafts 40,41 and the shafts themselves are
supported concentrically in the bosses 12,12 using bearings 70.
Unlike the conventional wisdom applied to such circumferential
piston pumps, the bearings 70 employed herein are not supported
external to the rotor chamber in a protected environment.
Recognizing the oft times harsh conditions experienced by pumps in
hot, or contaminated environments, face-to-face hard bearing
surfaces, including tungsten carbide, silicon carbide, and ceramics
are provided inside each boss 12,12 and on the corresponding
locations on the main drive shaft 40 and idler shaft 41. Best shown
in FIGS. 6 and 8, bearings 70 are fit into each boss 12. Mating
bearings 70 are also fit to the shafts 40,41 (obscured in FIGS. 6
and 8--an example shown in FIG. 8). Similar complementary bearings
70 are employed in each timing assembly 51.
[0064] Best seen in FIGS. 4 and 6, sealing between the individual
components of the pump housings 30, end plates 13, timing
assemblies 51, and fluid cross-over sections 60 is accomplished
using specially molded high temperature O-ring seals 90. The seals
90 are fitted in corresponding shaped grooves 91 formed in each
pump housing 30, providing full sealing around the perimeter of
each chamber 30, each stacking interface and each individual
lubricant and instrumentation port hole 80, running through the
full length of the pump stage 22.
[0065] As discussed earlier, each complete assembled pump stage 22
is mounted inside an outer retaining barrel 24 for supporting the
complete assembly. Accordingly, each complete stacked pump stage 22
is free of any internal mechanical fasteners.
[0066] The outside pump retaining barrel 24 is precision ground and
polished on its inside diameter, and provides close tolerance
support for each internally mounted section 21,21 and stage 22. The
extreme ends 29 of the outer retaining barrel 24 are internally
threaded, and each match with the externally threaded retaining
nut. The retaining nut 25 can also be provided by a threaded fluid
cross-over 60. Once the retaining nuts 25 are threaded into each
end of the outer retaining barrel, they sandwiches the stacked pump
sections 21 and stages 23 together, compressing the O-ring seals 90
and thereby providing full internal sealing of the internal pump
stage components 21,51,60.
[0067] The assembly is aided by compressing the stack of pump
components 21,51,60 using opposing mandrels. The end retaining nuts
25 are then threaded into each end of the outer retaining barrel to
retain the compressed stack in the outer retaining barrel 24.
Depending upon the number of sections 21 for the particular pump
configuration, and as an example, for three stages of fifteen
sections/stage about 10,000 to 20,000 pounds force is applied.
[0068] In operation, each stage of a circumferential piston pump
produces a characteristic pulsing at each discharge. Accordingly,
and in a preferred aspect, such pulsing is minimized by slightly
rotationally incrementing each pair of rotors 11,11 for each
successive section 21,21. One approach is to mount the rotors 11,11
on the drive shafts 40 and idler shafts 41 such that the pump
OTI/OTO timing for a complete pump stage 22 is incremented, at
equal angular intervals throughout the entire 360.degree. shaft
circumference, so as to equally divide the pulsing throughout each
360 degrees revolution. The resulting fluid flow has an overall
reduced variation in pulsation at the discharge manifold 31m and
provides continuous low pulsation fluid intake and fluid flow
discharge characteristics. For example, for a stage 22 having
fifteen pump sections 21, each rotor 11 of a rotor pair would be
incrementally rotated about 24 degrees on the main drive shaft
(360/15). The rotors 11 are connected to the drive and idler shafts
40,41 by means of splines 42 and shaft keys (not shown). As is the
convention in rotating machines, shaft keyways are rounded with
radius ends, to reduce stresses on the shafts 40,41.
[0069] Referring to both FIGS. 2 and 10, the drive shaft 40,
running through the full length of the complete pump 20, is
supported at the discharge end of the pump 20 by a thrust/radial
bearing assembly 100. The thrust bearing assembly comprises a
bearing housing 101 located on top of the uppermost pump stage 22p,
and forms an integral part of the pump 20 when installed into the
outer retaining barrel 24. The thrust bearing assembly 100 contains
double thrust bearings 102,102 and double radial bearings 103,103
fit with bearing housings 104 to prevent axial and radial
driveshaft movement. The bearing assembly 100 is a sealed unit,
with high temperature mechanical seals 105,105 located at the upper
and lower end of the drive shaft bearing assembly 100. The bearing
assembly 100 is filled with high temperature lubricant oil to
lubricate the bearings 102,103. The bore of the bearing housing 101
contains the combined stack of bearings 102,103 and has an
additional lubricant oil reservoir 106 surrounding the bearing
assembly 100. The reservoir 106 can be refreshed or topped up
through a lube oil connection (not shown) at the top of the pump 20
adjacent the production line connection 110.
[0070] Alignment of the stacked components 21,51 is accomplished by
hollow alignment dowels 80, located in integral
lubricant/instrumentation galleries 81 running through the full
length of the complete pump 20. Each pump housing 30, end plate 13,
timing assembly 51 and fluid cross-over section 60 have such
galleries 81 into which are fit hollow dowels 81 for alignment as
well as for lubricant/instrumentation purposes. Each pump section
21 is located and rotationally locked to the adjacent section 21
using the dowels 80. Further, through the use of hollow dowels 81,
one through four galleries 80 can be formed along the length of the
pump 20. For example, the oil reservoir 106 surrounds the bearing
assembly 100 and is also supplied with lubricant externally through
one of the galleries 80 running through the full length of the pump
20.
[0071] As shown in FIG. 11, assembly of the pump sections 21
comprises first stacking each of two or more pump housings 30 and
rotors 11,11 between end plates 13,13. The end plate's bosses 12,12
center and locate the rotors 11,11 in the pump housing 30, and also
rotatably support the main drive shaft 40 and idler shaft 41
bearings 70. Pump housings 30 and end plates 13,13 are stacked back
to back, with timing assemblies 51 at regular intervals, to form
one or more stages 22. As shown in FIG. 2, the entire stack
30,13,51 . . . is compressed and installed in the outer retainer
barrel 24 for form the complete pump 20.
[0072] The discharge fluid is delivered from the uppermost pump
stage 22p via the common discharge manifold 31m to a last
cross-over section 60, connecting to the production pipe line 110
for directing the fluid to the fluid destination. In a pump 20 fit
to a wellbore, the fluid destination would be the earth's
surface.
EXAMPLE
[0073] Operations for a pump 20 capable of operation in a 95/8"
wellbore casing include a plurality of 8" diameter pump housings 30
comprises a suction stage 22s and two pressure stages 22p,22p. Each
pump section 20 has a rotor chamber 10 and rotor 11,11 combination
having a displacement of 0.833 liters per rotor revolution. Timing
gears 50 are provided every five pump sections 21, or three
assemblies 51 per stage 22. Rotational speed of the pump sections
21 can vary between about zero to over 600 rpm, limited only by
mechanical constraints such as the means for driving the drive
shaft and depending on the characteristics of the fluid. Operating
with drive means such as conventional top drives rotating at 400
rpm, such a pump 20 can produce flow rates of about 1000
liters/minute at 4500 kPa on fluid such as oil having gravity and
viscosity equivalent to fluid similar to a SAE30 oil.
[0074] Having reference to FIGS. 12a-12c, a single stage 22 having
five sections 21 of the above pump 20 was manufactured, assembled
and operated on water at 30.degree. C. The water had a viscosity of
less than about 1 mPa.multidot.s. The figures are graphs of pump
performance versus fluid discharge flow rates and discharge
pressure. FIG. 12a demonstrates test results for pump efficiency
pumping water at 30.degree. C. FIGS. 12b and 12c illustrate the
pump power and torque. FIGS. 13a-13c illustrate the same parameters
of efficiency, power and torque curves when pumping SAE30 oil at
70.degree. C. and FIGS. 14a-14c illustrated efficiency, power and
torque curves when pumping SAE30 oil at 190.degree. C.
[0075] With oil at 70.degree. C., the 5 stages produced flow rates
in the order of 340-300 l/min at between 350-1400 kPa respectively.
Through extrapolation to 15 sections 21 per stage 22, one would
expect to get about three times the flow rate or upwards of 1000
liters/min, and when pumped through two additional pressure stages,
each having 15 sections for maintaining the flow rates, one could
expect discharge pressures of up to about 4200 kPa.
* * * * *