Note: Descriptions are shown in the official language in which they were submitted.
CA 02310544 2000-06-O1
Ref
(23455/234)
IN THE CANADIAN PATENT OFFICE
INVENTORS: Wayne Thomas and Gary Morcom
ASSIGNEE: PanCanadian Petroleum Limited
TITLE: Fluid Displacement Apparatus and Method
TO ALL WHOM IT MAY CONCERN:
BE IT KNOWN THAT WE, Wayne Thomas
of Suite 611, 9800 Horton Road, Calgary, Alberta, Canada T2V SBS,
Citizen of Australia, and Gary Morcom
of 632 Willesden Drive, Calgary, Alberta, Canada T2J 2G1
Citizen of Canada
have invented a : FLUID DISPLACEMENT APPARATUS
AND METHOD
of which the following is a specification.
CA 02310544 2000-06-O1
FLUID DISPLACEMENT APPARATUS AND METHOD
Field Of Invention
This invention relates generally to the field of well production apparatus
such as
used, for example, in down-hole pumping systems in wells. It also relates to
pumping
apparatus and methods for use of that apparatus.
Background Of The Invention
Specific challenges arise in oil production when it is desired to extract
heavy,
sandy, gaseous or corrosive high temperature oil and water slurries from
underground
wells. These slurries to be pumped range over the breadth of fluid rheology
from highly
viscous, heavy, cold crude to hot thermal fluids. Recent technological
advances have
permitted well to be sunk vertically, and then to continue horizontally into
an oil
producing zone. Thus wells can be drilled vertically, on a slant, or
horizontally. To date,
although equipment is available to drill these wells, at present there is a
need for a
relatively efficient, and reasonably economical means to extract slurries from
wells of
these types.
In particular, it would be desirable to have a type of pump that would permit
relatively efficient extraction of oil slurries from underground well bores
that include
horizontal and steam assisted gravity drainage (SAGD) or non-thermal
conventional
wells. In one SAGD process twin horizontal wells are drilled in parallel, one
somewhat
above the other. Steam is injected into the upper bore. This encourages oil
from the
adjacent region of the oil bearing formation to drain toward the lower bore.
The
production fluids drawn from the lower bore can then be pumped from the lower
bore to
the surface.
It is advantageous to match the pumping draw down of the lower bore to the
rate
of steam injection used in the upper bore. This will depend on the nature of
the oil
bearing formation, the viscosity of the oil and so on. If the rates can be
matched to
achieve a relative balance, the amount of steam pressure required can be
reduced, thus
reducing the power of the steam injection system required, and resulting in a
more
3 S economical process.
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Pumping the production oil or slurry from the lower horizontal bore presents a
number of challenges. An artificial lift, or pumping, system must be able to
operate even
when the "liquid" to be pumped is rather abrasive. For example, some design
criteria are
based on slurries that may contain typically 3 % by weight, and for short
periods as much
as 30 % by weight, of abrasives, such as sand The pumping technology must be
capable
of handling a high volume of formation solids in the presence of high gas oil
ratios
(GOR). The system may well be called upon to handle slugs of hydrocarbon gas
and
steam created by flashing of water into vapour. On occasion the system may run
dry for
periods of time. As such, it is desirable that the system be capable of
processing gases,
and of running "dry". It is also desirable that a pump, and associated tubing,
be able to
operate to a depth of 1000 M below well-head, or more, with an allowance of
100 psi as
the minimum flow-line input pressure. It is also desirable that the equipment
be able to
operate in chemically aggressive conditions where pH is +/- 10.
1 S Further still, it would be advantageous to be able to cope with a large
range of
viscosities - from thick, viscous fluids to water, and at relatively high
temperatures. The
chosen equipment should be operable in both vertical and horizontal well
bores.
Another requirement is the ability to pump all of the available fluid from the
well
bore. To that end it is advantageous to be able to operate the pump as far as
possible in
depth into a horizontal section. The system needs to be able to operate at
high volume
capacities, i.e., high volumetric flow rates, and to operate reasonably well
under saturated
steam conditions while processing hydrocarbon gases. As far as the inventors
are aware,
there is at present no artificial lifting equipment that addresses these
problems in a fully
satisfactory manner. It would be desirable to have a relatively efficient high
temperature,
high volume pumping system that can accommodate a large range of production
requirements, with the capability of being installed into, and operating from,
the
horizontal section of a well bore.
Other artificial lift systems have been tried. For example, one known type of
pump is referred to as a "Pump Jack". It employs sucker rod pumping with a
down-hole
plunger pump. This is a reciprocating beam pumping system that includes a
surface unit
(a gearbox, Pittman arms, a walking beam, a horsehead and a bridle) that
causes a rod
string to reciprocate, thereby driving a down-hole plunger pump.
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Pump jack systems have a number of disadvantages. First, it is difficult to
operate
a down-hole reciprocating rod pump in a horizontal section because of the
reliance on
gravity to exert a downward force on the pump plunger. Further, a horizontal
application
may tend to cause increased pump wear due to curvature in the pump barrel (to
get to the
horizontal section) and increased sucker rod and tubing wear. Second, down-
hole pumps
are susceptible to damage from sand, high temperature operation, and other
contaminants.
Third, plunger pumps are prone to gas lock. Fourth, the downward stroke of the
pump
rod, being governed by gravity, is subject to "rod float". That is, as the
length of the rod
increases, the rod itself has sufficient resiliency, and play, that the motion
transmitted
from the surface is not accurately copied at the plunger - it may be out of
phase, damped,
or otherwise degraded so that much pumping effort is wasted. Fifth, pump jacks
tend to
require relatively extensive surface site preparation. Horizontal units tend
to require
larger than normal pump units because of the need to activate (i.e., operate)
the rod string
around the bend of the "build section" as well as to lift the weight of the
rod string.
Another type of pump is the progressive cavity pump, or screw pump. In this
type
of pump a single helical rotor, usually a hard chrome screw, rotates within a
double
helical synthetic stator that is bonded within a steel tube. Progressive
cavity pumps also
have disadvantages. First, they tend not to operate well, if at all, at high
temperatures. It
appears that the maximum temperature for continuous operation in a well bore
is about
180 F (80 C). It is desirable that the pump be able to operate over a range of
-30 to 350
C (-20 to 650 F), and that the pump be able to remain in place during steam
injection.
Second, progressive cavity pumps tend not to operate well "dry". It is
desirable to be able
to purge hydrocarbon gases, or steam created by flashing water into vapour. As
far as the
present inventors are aware, progressive cavity pumps have not been capable of
operation
in high GOR conditions. Further, the synthetic stator material of some known
pumps
appears not to be suitable for operation with aromatic oils. Due to the design
of the
screws, and their friction fit, progressive cavity pumps tend to have little,
if any, ability to
generate high pressures, thereby restricting their use to relatively shallow
wells. In
addition, progressive cavity pumps tend to be prone to wear between the rotor
and the
stator, and tend to have relatively short service run lives between overhauls.
Progressive
cavity pumps do not appear to provide high operational efficiency.
Electric submersible pumps (ESP) include a down-hole electric motor that
rotates
an impeller (or impellers) in the pump, thereby generating pressure to urge
the fluid up
the tubing to the surface. Electric submersible pumps tend to operate at high
rotational
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speeds, and tend to be adversely affected by inflow viscosity limitations.
They tend not
to be suitable for use in heavy oil applications. Electric submersible pumps
tend to be
susceptible to contaminants. Electric submersible pumps are not, as far as the
inventors
are aware, positive displacement pumps, and consequently are subject to
slippage and a
corresponding decrease in efficiency. The use of electric submersible pumps is
limited by
horsepower and temperature restrictions.
Jet pumps typically employ a high pressure surface pump to transmit pumping
fluid down-hole. A down-hole jet pump is driven by this high pressure fluid.
The power
fluid and the produced fluid flow together to the surface after passing
through the down-
hole unit. Jet pumps tend to have rather lower efficiency than a positive
displacement
pump. Jet pumps tend to require higher intake pressures than conventional
pumps to
avoid cavitation. Jet pumps tend to be sensitive to changes in intake and
discharge
pressure. Changes in fluid density and viscosity during operation affect the
pressures,
1 S thereby tending to make control of the pump difficult. Finally, jet pump
nozzles tend to
be susceptible to wear in abrasive applications.
Gas lift systems are artificial lift processes in which pressurised or
compressed gas
is injected through gas lift mandrels and valves into the production string.
This injected
gas lowers the hydrostatic pressure in the production string, thus
establishing the required
pressure differential between the reservoir and the well-bore, thereby
permitting
formation fluids to flow to the surface. Gas lift systems tend to have lower
efficiencies
than positive displacement pumps. They tend be uncontrollable, or poorly
controllable,
under varying well conditions, and tend not to operate effectively in
relatively shallow
wells. Gas lift systems only have effect on the hydrostatic head in the
vertical bore, and
may tend not to establish the required drawdown in the horizontal bore to be
beneficial in
SAGD application. Further, gas lift systems tend to be susceptible to gas
hydrate
problems. The surface installation of a gas lift system may tend to require a
significant
investment in infrastructure - a source of high pressure gas, separation and
dehydration
facilities, and gas distribution and control systems. Finally, gas lift
systems tend not to be
capable of achieving low bottom-hole producing pressures.
Operation of a pump at a remote location in a bore hole also imposes a number
of
technical challenges. First, the pump itself can not be larger in diameter
than the well
bore. In oil and gas well drilling, for example, it can only be as large as
permitted by the
well-head blow-out preventer. A typical casing may have a diameter of 140 to
178 mm
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(5 -1/2 to 7 inches). A typical production tube has a diameter in the range of
73 to 89 mm
(2 - 3/4 to 3 - 1/2 inches). Providing power to a down-hole pump is also a
challenge. An
electric motor may burn out easily, and it may be difficult to supply with
electrical power
at, for example, ten thousand feet (3000 m) distance along a bore given
significant line
losses. A pneumatic or hydraulic pump can be used, provided an appropriate
flow of
working fluid is available under pressure. Whatever type of pump is used, it
may tend to
need to be matched in a combination with the available power delivery system.
In a number of applications, such as oil or other wells, it is desirable to
conduct
one or more types of fluid down a long tube, or string of tubing, while
conducting another
flow, or flows, in the opposite direction. Similarly, it may be advantageous
to use a
passageway, or a pair of passageways to conduct one kind of fluid, and another
passageway for electrical cabling whether for monitoring devices or for some
other
purpose, or another pair of passageways for either pneumatic or hydraulic
power
transmission. In oil field operations it may be desirable to have a pair of
passageways as
pressure and return lines for hydraulic power, another line, or lines, for
conveying
production fluids to the surface, perhaps another line for supplying steam,
and perhaps
another line for carrying monitoring or communications cabling.
One method of achieving this end is to use concentrically nested pipes, the
central
pipe having a flow in one direction, the annulus between the central pipe and
the next
pipe carrying another flow, typically in the opposite direction. It may be
possible to have
additional annulli carrying yet other flows, and so on. Although singular
continuous
coiled tubing has been used, the ability to run an inner string within an
outer concentric
string is relatively new, and may tend to be relatively expensive. This has a
number of
disadvantages, particularly in well drilling. Typically, in well drilling the
outside
diameter of the pipe is limited by the size of the well bore to be drilled.
This pipe size is
all the more limited if the drilling is to penetrate into pockets of liquid or
gas that are
under pressure. In such instances a blow-out preventer (BOP) is used, limiting
the
outside diameter of the pipe. Typically, a drill string is assembled by adding
modules, or
sections of pipe, together to form a string. Each section is termed a "joint".
A joint has a
connection means at each end. For example, one end (typically the down-hole
end) may
have a male coupling, such as an external thread, while the opposite, well-
head , end has a
matching female coupling, such as a union nut. It is advantageous in this
instance to have
a positive make-up, that is, to be able to join the "joints" without having to
spin the entire
body of the joint, but rather to have the coupling rotate independently of the
pipe.
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A limit on the outside diameter of the external pipe casing imposes inherent
limitations on the cross-sectional area available for use as passageways for
fluids. In
some instances three or four passages are required. For example, this is the
case when a
S motive fluid, whether hydraulic oil or water, is used to drive a motor or
pump, requiring
pressure and return lines, while the production fluid being pumped out
requires one or
more passages. The annulus width for four passages nested in a 3.5 inch tube
is relatively
small. The inventors are unaware of any triple or quadruple concentric tube
string that
has been used successfully in field operations.
As the depth of the well increases, the downhole pressure drop in the passages
also increases. In some cases the well depth is measured in thousands of
metres. The
pressure required to force a slurry, for example, up an annular tube several
kilometres
long, may tend to be significant. One way to reduce the pressure drop is to
improve the
1 S shape of the passages. For example, in the limit as an annulus becomes
thin relative to its
diameter, the hydraulic diameter of the resultant passage approaches twice the
width, or
thickness, of the annulus. For a given volumetric flow rate, at high Reynolds
numbers
pipe losses due to fluid friction vary roughly as the fourth power of
diameter. Hence it is
advantageous to increase the hydraulic diameter of the various passageways.
One way to
increase the hydraulic diameter of the passage is to bundle a number of tubes,
or pipes, in
a side-by-side configuration. within an external retainer or casing in place
of nested
annulli. The overall cross-sectional area can also be improved by dividing the
circular
area into non-circular sectors, such as passages that have the cross-section
shape of a
portion of a pie.
Another important design consideration in constructing a pipe for deep well
drilling, or well drilling under pressure, is that the conduit used be
suitable for operation
in a blow out preventer. This means that the pipe must be provided in
sections, or joints,
that can be assembled progressively in the blow out preventer to create,
eventually, a
complete string thousands, or tens of thousands, of feet long. It is important
that the
sections fit together in a unique manner, so that the various passages align
themselves - it
would not do for an hydraulic oil power supply conduit of one section to be
lined up with
the production fluid upward flow line of an adjacent section. Further, given
the pressures
involved, not only must the passage walls in each section be adequate for the
operational
pressure to which they are exposed, but the sections of pipe must have a
positive seal to
each other as they are assembled. Further still, given the relatively remote
locations at
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which these assemblies may be used, and possibly harsh environmental
conditions, the
sections must go together relatively easily. It is advantageous to have a
"user friendly"
assembly for ease of pick-up, handling, and installation, that can be used in
a
conventional oil rig, for example.
Some of the tube passages must be formed in a manner to contain significant
pressure. For an actual operating differential pressure in the range of 0 -
2000 p.s.i. it
may be desirable to use pipe that can accommodate pressures up to, for
example, 8,000
p.s.i. seamless steel pipe can be obtained that is satisfactory for this
purpose. Electrical
resistance welded pipe (ERV~ that is suitable for this purpose can also be
obtained. The
steel pipe can then be roll formed to the desired cross-sectional shape.
Summary of the Invention
1 S In an aspect of the invention there is a fluid displacement assembly
having a first
gear, a second gear, and a housing having a chamber defined therein to
accommodate said
gears. The first and second gears are mounted within the housing in meshing
relationship. The housing has an inlet by which fluid can flow to the gears
and an outlet
by which fluid can flow away from the gears. The gears are operable to urge
fluid from
the inlet to the outlet, and at least a portion of the housing is made from a
ceramic
material.
In an additional feature of that aspect of the invention, the assembly is
operable at
temperatures in excess of 180°F. In another additional feature, the
assembly is operable
at temperatures at least as high as 350°F. In another additional
feature, the ceramic
material is part of a ceramic member, and is mounted within a casing. In still
another
feature, the ceramic material has a compressive pre-load.
In yet another feature the first and second gears are spur gears. In an
alternative
feature the first gear is a spur gear and said second gear is a ring gear
mounted
eccentrically about said first gear. In a further feature, a ceramic partition
member is
mounted within the ring gear between the first gear and the second gear. In a
further
alternative feature, the first and second gears are a pair of gerotor gears.
3 5 In a further additional feature of the invention, the gears are sandwiched
between
a pair of first and second yokes mounted to either axial sides thereof. Each
of the yokes
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has a pair of first and second bores formed therein to accommodate the first
and second
shafts. Each of the yokes has a gear engagement face located next to the
gears. Each of
the gear engagement faces has a peripheral margin conforming to the arcuate
portions of
the internal wall of the housing, and each of the yokes is biased to lie
against the gears.
In another aspect of the invention there is a gear pump having a first gear, a
second gear, and a housing having a chamber defined therein to accommodate
said gears.
The first gear is mounted on a shaft having an axis of rotation. The first and
second gears
are mounted in the housing in meshing engagement. The housing has an inlet by
which
fluid can flow to the gears and an outlet by which fluid can flow away from
the gears, and
the shaft is mounted in ceramic bushings within the housing. In another
feature of that
aspect of the invention, the ceramic bushings include ceramic inserts mounted
in a metal
body.
In a further aspect of the invention there is a gear pump having a first gear,
a
second gear, and a housing having a cavity defined therein to accommodate said
first and
second gears. The first and second gears are mounted in meshing relationship
within the
housing. The housing has an inlet by which fluid can flow to the gears and an
outlet by
which fluid can flow away from the gears. The gears are operable to displace
fluid from
the inlet to the outlet. The first gear is mounted on a first shift having a
first axis of
rotation. The first and second gears each have a first end face lying in a
first plane
perpendicular to the axis of rotation. A moveable wall is mounted within the
housing to
engage the first end faces of the gears. The moveable wall has a ceramic
surface oriented
to bear against the first end faces of the first and second gears.
In an additional feature of that aspect of the invention, the moveable wall is
a
head of a piston and, in operation, the piston is biased toward the first end
faces of the
first and second gears. In another feature the piston is hydraulically biased
toward the
gears. In another feature, each of the first and second gears has a second end
face lying in
a second plane spaced from the first plane, and a second moveable wall is
mounted within
the housing to bear against the second end faces of the first and second
gears. In another
feature, both of the moveable walls are biased toward the gears. In another
additional
feature, the end walls are heads of respective first and second pistons, the
pistons being
moveable parallel to the axis of rotation. In a further additional feature,
the ceramic
surface is a plasma carried on a metal substrate.
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In another additional feature, the second gear is mounted on a second shaft
extending parallel to the first shaft. The ceramic surface is formed on a body
having a
first bore defined therein to accommodate the first shaft and a second bore
defined therein
to accommodate the second shaft, the body being displaceable along the shafts.
In a
further feature, at least one of the bores has a wall presenting a ceramic
bushing surface to
one of the shafts. In another feature the body has a passageway formed therein
to
facilitate flow of fluid. In a further feature, the body has passageways
formed therein to
facilitate flow of fluid to and from the inlet and the outlet.
In still another aspect of the invention, there is a gear pump assembly having
a
pair of first and second mating gears, mounted on respective first and second
parallel
shafts in meshed relationship; a housing for the gears, the housing having an
inlet by
which fluid can flow to the gears and an outlet by which fluid can flow away
from the
gears. The gears are operable to urge fluid from the inlet to the outlet. the
housing
includes a gear surround having two overlapping bores defined therein
conforming to the
gears in meshed relationship, and the surround presents a ceramic internal
surface to said
gears.
In an additional feature the surround is formed of a transformation toughened
zirconia. In a further feature, the surround is made of a ceramic monolith. In
another
feature, the surround has a compressive pre-load. In a still further feature,
the surround
is mounted within a shrink fit casing member. In yet another feature, the
ceramic
monolith has a co-efficient of thermal expansion corresponding to the co-
efficient of
thermal expansion of the gears. In another additional feature, the gear pump
assembly
has a movable endwall mounted to ride in the overlapping bores.
In another additional feature, the shafts each have an axis of rotation and
said
gears each have first and second end faces lying in first and second spaced
apart parallel
planes, said parallel planes extending perpendicular to said axis. A movable
piston is
mounted to ride within the overlapping bores, and the piston has a face
oriented to engage
the first end faces of the gears.
In another aspect of the invention, there is a gear pump assembly having a
first
gear mounted on a first shaft, the first shaft having a first axis of
rotation; a second gear
mounted on a second shaft, the second shaft having a second axis of rotation;
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the axes lying in a common plane. The first and second gears are mounted to
mesh
together in a first region between the axes. A gear surround has an internal
wall defining
a cavity shaped to accommodate the gears. The internal wall has a first
portion formed on
an arc conforming to the first gear and a second portion, formed on another
arc, to
conform to the second gear. The first and second portions lie away from the
first region.
The internal wall has a third portion between the first and second portions.
The third
portion lies abreast of the first region and has a first passageway formed
therein to carry
fluid to the cavity adjacent to the gears to one side of the plane. The
internal wall has a
fourth portion lying between the first and second portions. The fourth portion
lies abreast
of the first region to the other side of the plane from the third portion. The
fourth portion
has a second passageway formed therein to carry fluid from the cavity. The
gears are
operable to transfer fluid from the first passageway to the second passageway.
In another aspect of the invention, there is a well production apparatus for
transporting a production fluid from a downhole portion of a well to a well
head. The
well production apparatus includes a transport assembly having a first end
located in the
downhole portion of the well and a second end located at the wellhead, and a
gear pump
mounted to said first end of said transport assembly. The transport assembly
has at least
one passageway defined therein for conducting production fluid from the first
end to the
second end. The transport assembly has a power transmission member extending
between the first and second ends thereof. The transmission member is
connected to the
gear pump to permit the gear pump be driven from the wellhead, and the gear
pump is
operable to urge production fluid from the first end of the transport assembly
to the
wellhead.
In still another aspect of the invention, there is a method of moving
production
fluid from a well to a wellhead, the method including the steps of mounting a
gear pump
to a first end of a transport apparatus from the wellhead; introducing the
transport
apparatus into the well and locating the gear pump in a downhole production
region of the
well; and driving the gear pump from outside the well to urge production fluid
from the
production region to the wellhead.
In an additional feature of that aspect of the invention, the method includes
the
steps of providing a passageway in the transport apparatus for carrying
production fluid
from the production region to the wellhead; and providing a power transmission
member
to carry power for the wellhead to the gear pump.
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These and other aspects and features of the invention are described herein
with
reference to the accompanying illustrations.
Brief Description of the Drawings
Figure la shows a general schematic illustration of a steam assisted gravity
drainage oil productions system having a down-hole production unit;
Figure lb shows a schematic illustration of the down-hole production unit of
Figure la.
Figure 2a shows a side view of the down-hole production unit of Figure la;
Figure 2b shows a side view of the down-hole production unit of Figure 2a with
its external casings removed;
Figure 2c shows a longitudinal cross-section of the down-hole production unit
of
1 S Figure 2a;
Figure 3a shows a cross-section taken on section '3a - 3a' of Figure 2b;
Figure 3b shows a end view of Figure 2a;
Figure 3c shows a cross-section taken on section '3c - 3c' of Figure 2c
Figure 3d shows a cross-section taken on section '3d - 3d' of Figure 2c;
Figure 3e shows a cross-section taken on section '3e - 3e' of Figure 2c;
Figure 3f shows a cross-section taken on section '3f - 3f of Figure 2c;
Figure 3g shows a cross-section taken on section '3g - 3g' of Figure 2c;
Figure 3h shows a cross-section taken on section '3h - 3h' of Figure 2c;
Figure 3i shows a cross-section taken on section '3i - 3i' of Figure 3d;
Figure 4a shows an end view of a top or intermediate stage motor unit of the
down-hole production unit of Figure 2b;
Figure 4b shows a cross-section on section '4b - 4b' of Figure 4a;
Figure 4c shows a cross-section on section '4c - 4c' of Figure 4a;
Figure 4d shows a side view of a fitting of Figure 4a;
Figure 4e shows an exploded view of the fitting of Figure 4d;
Figure 4f shows an end view of the fitting of Figure 4d;
Figure 4g shows a cross-sectional view taken on section '4g - 4g' of Figure
4f;
Figure Sa shows an end view of a bottom stage motor unit of the down-hole
production unit of Figure 2b;
Figure Sb shows a cross-section on section 'Sb - Sb' of Figure Sa;
Figure 5c shows a cross-section on section '5c - Sc' of Figure Sa;
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Figure 6a shows an end view of a top or intermediate stage pump unit of the
down-hole production unit of Figure 2b;
Figure 6b shows a cross-section on section '6b - 6b' of Figure
6a;
Figure 6c shows a cross-section on section '6c - 6c' of Figure
6a;
Figure 7a shows an end view of a bottom stage pump unit of
the down-hole
production unit of Figure 2b;
Figure 7b shows a cross-section on section '7b - 7b' of Figure
7a;
Figure 7c shows a cross-section on section '7c - 7c' of Figure
7a;
Figure 8a shows an exploded view of a positive displacement
gear pump
assembly of the down-hole production unit of Figure 2a;
Figure 8b shows an end view of the gears of the gear assembly
of Figure 8a;
Figure 8c shows an assembled perspective view of the positive
displacement gear
pump of Figure 8a;
Figure 8d shows an exploded view of an alternate positive
displacement gear
assembly to that of Figure 8a;
Figure 8e shows an end view of the gears of the gear assembly
of Figure 8d;
Figure 8f shows an exploded view of a further alternate positive
displacement
gear assembly to that of Figure 8a;
Figure 8g shows an end view of the gear assembly of Figure
8f;
Figure 8h shows a perspective view of an alternate piston
for the assembly of
Figure 8a;
Figure 8i shows a perspective view of another alternate piston
for the assembly of
Figure 8a;
Figure 9a shows a side view of an assembled mufti-passage
pipe assembly
according to an aspect of the present invention;
Figure 9b shows an isometric view of a pair of the mufti-passage
pipe assemblies
of Figure 9a joined together;
Figure 9c shows an exploded isometric view of the pair of
mufti-passage pipe
assemblies of Figure 9b in a separated condition;
Figure 9d is a cross-sectional view of the pipe assemblies
of Figure 9a showing
the join;
Figure l0a is an isometric view of a tube member of the mufti-passage
pipe
assembly of Figure 9a;
Figure lOb is a cross-sectional view of the tube member of
Figure 10a;
Figure l la is a plan view of a seal for the pipe assemblies
of Figure 9a;
Figure l lb is a diametral cross-section of the seal of Figure
l la;
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Figure l lc is a detail of a portion of the cross-section of the seal of
Figure l lb;
Figure 12 shows a cross-sectional view of the tube assembly of Figure 9a taken
on
S
section '12 - 12';
Detailed Description of the Invention
The description which follows, and the embodiments described therein, are
provided by way of illustration of an example, or examples of particular
embodiments of
the principles of the present invention. These examples are provided for the
purposes of
explanation, and not of limitation, of those principles and of the invention.
In the
description which follows, like parts are marked throughout the specification
and the
drawings with the same respective reference numerals. The drawings are not
necessarily
to scale and in some instances proportions may have been exaggerated in order
more
clearly to depict certain features of the invention.
By way of a general overview, an oil extraction process apparatus is indicated
generally in Figure la as 20. It includes a first bore 22 having a vertical
portion 24 and a
horizontal portion 26. Horizontal portion 26 extends into an oil bearing
formation 28 at
some distance below the surface. For the purposes of illustration, the
vertical scale of
Figure 1 is distorted. The actual depth to horizontal portion 26 may be
several
kilometres. A steam generating system 30 is located at the well head and is
used to inject
steam at temperature T and pressure P down bore 22. Horizontal portion 26 is
perforated
to permit the steam to penetrate the adjacent regions of formation 28.
A second well bore is indicated as 32. It has a vertical portion 34 and a
horizontal portion 36, corresponding generally to vertical portion 24 and
horizontal
portion 26 of bore 22. Horizontal portion 36 runs generally parallel to, and
somewhat
below, horizontal portion 26. A section (or sections) 38 of horizontal portion
36 runs
through oil bearing formation 28, and is perforated to permit production fluid
to drain
from formation 28 into section 38. The injection of steam into formation 28
through
portion 26 is undertaken to encourage drainage of oil from formation 28. It
will be
appreciated that alternative types of well can also have analogous vertical or
inclined
perforated sections.
A production fluid lift system in the nature of a pumping system is designated
generally as 40. It is shown schematically in Figure lb. It includes a power
generation
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system 42 at the well head, in the nature of a motor 44 that drives a
hydraulic pump 46.
A transport system 48 carries power transmitted from system 42 to the downhole
end 50
of bore 32, and carries production fluid from downhole end 50 to the well head
52. A
collection and separation system, such as a holding tank 54 is located at the
well head to
S receive the production fluid as it exits transport system 48. A hydraulic
reservoir 56
receives returned hydraulic fluid HF, and has a sump whence hydraulic fluid is
again
drawn into hydraulic pump 46. Respective filters are indicated as 57 and 59.
Transport system 48 terminates at a downhole production unit 60, described in
greater detail below. Production unit 60 includes a power conversion unit,
namely a
hydraulic motor section 62, that is driven by the pressurized hydraulic fluid
(such as
water) earned in pressure line 65 and return line 66 by transport system 48
from and to
hydraulic pump 46 to convert the transported power to a mechanical output,
namely
torque T in a rotating output shaft. Production unit 60 also includes a pump
section 64
that is driven by hydraulic motor 62, pump section 64 being operable to urge
production
fluids PF to the surface by way of production fluid lift line 68 through
transport system
48. A blow out preventer indicated as BOP, engages transport system 48 at well
head 52
since the well pressure, and temperature, may be well above atmospheric.
Downhole production unit 60 is shown in greater detail in the illustrations of
Figures 2a to 8c. As a note of preliminary explanation, the frame of reference
for
production unit 60, when deployed in production, is a well bore that can be
vertical,
inclined or horizontal. In the explanation that follows, whether the well is
horizontal, or
vertical, or inclined, references to up, or upward, mean along the bore toward
the well-
head. Similarly, references to down, or downward, mean away from the well
head. In a
consistent manner, when the unit is being assembled into a long string at the
well head,
the orientation of up and down corresponds to how personnel at the well head
would see
the unit, or its components as they are being assembled and introduced into
the well. For
the purposes of operation, the local portion of the well bore occupied at any
one time by
production unit 60 approximates a round cylinder having a central longitudinal
axis CL,
defining an axial direction either up or down, with corresponding radial and
circumferential directions being defined in any plane perpendicular to the
axial direction.
Downhole production unit 60 is shown, as assembled, in Figures 2a, 2b and 2c.
Starting at the upward end, the endmost portion of transmission system 48 is
shown with
casing removed as 70. Portion 70 has four conduit members in a bundle that
terminates at
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a female coupling 72. The four conduit members, identified in Figure 3a as 74,
75, 76
and 77 and carry, respectively, in conduit member 74, downflowing hydraulic
motor fluid
i
(the pressure supply line 65); in conduit member 75, upflowing hydraulic motor
fluid (the
return line 66); and in conduits 76 and 77, pumped production fluid flowing
upward, (i.e.,
the production fluid lift line 68 to the well head).
Female coupling 72 connects with the male end coupling of motor section 62.
Motor section 62 has a first, or upward transition coupling in the nature of a
motor section
inlet plate 80; a first motor unit namely upper motor assembly 82; a second
motor unit
namely lower motor assembly 84; a second, or lower transition coupling in the
nature of a
motor section outlet plate 86; and an external casing 88. Pump section 64 is
connected to
the lower end of motor section 62. Pump section 64 has a first, or upper, pump
unit
namely upper pump assembly 90, and a second, or lower, pump unit namely lower
pump
assembly 92. The direction of the various fluid flows through these units is
described
more fully below.
The basic unit of construction of each of first and second motor units 84 and
86 is
a positive displacement gear assembly, 100, shown in detail in Figures 5a to
8a. Gear
assembly 100 is shown in exploded view in Figure 8a. First and second pump
assemblies
90 and 92 employ positive displacement gear assemblies 101 which are almost
identical
to assembly 100 in construction but are, in the illustrated configuration,
somewhat larger
in diameter as shown in Figure 2c, and assemblies 101 have thicker shrink fit
casings 127.
For the purposes of the present description, a description of the elements of
assembly 100
will serve also to describe the components of pump assemblies 101.
As shown in Figure 8a, gear assembly 100 includes a pair of matched first and
second gears 102 and 104 mounted to respective stub shafts 106 and 108. Stub
shafts 106
and 108 are parallel such that their axes lie in a common plane. When gears
102 and 104
engage, there is continuous line contact between mating lobes in a meshing
region located
between the axes of rotation of shafts 106 and 108 such that there is no clear
passage
between the engaging teeth. Stub shafts 106 and 108 are arranged such that
gears 102
and 104 are mounted toward one end of their respective stub shafts, such that
a short end
110 protrudes to one side of each gear, and a long end 112 protrudes to the
other. Each
long end 112 has a set of torque transmission members, in the nature of a set
of splines
114 to permit torque to be received or transmitted as may be appropriate.
Gears 102 and
104 are engaged such that the respective long ends of stub shafts 106 and 108
protrude to
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opposite sides of the matched gears, that is, one extending to in the upward
axial
direction, and one extending in the downward axial direction.
First and second pistons are indicated as 116 and 118. Each has a body having
an
eyeglass shape of first and second intersecting cylindrical lobes 119, 120
with a narrowed
waist 121 inbetween. Each of the lobes has a circular cylindrical outer
portion formed on
a radius that closely approximates the tip radius of gears 102 and 104. Each
body has a
pair of parallel, first and second round cylindrical bores 122 and 123, formed
in the
respective first and second lobes, of a size for accommodating one or another
end of stub
shafts 106 and 108. The centers of the bores correspond to an appropriate
centreline
separation for gears 106 and 108. In the preferred embodiment of Figure 8a,
pistons 116
and 118 are made of steel with ceramic face plates for engaging the end faces
of gears
102 and 104, and ceramic inserts that act as bushings for the respective ends
of stub shafts
106 and 108.
Alternative embodiments of pistons can be used, as shown in Figures 8h and Si,
for example. In Figure 8h, an alternative piston 115 is shown having a
generally ovate
form with a single relief 117 to accommodate adjacent fluid flow in the axial
direction.
In Figure 8i, a further alternative piston 119 has an ovate form lacking a
relief, such that
the adjacent surround member carries has the flow passage formed entirely
therewithin.
Although pistons 116 and 118 are made of steel, as noted above, they could
also be made
from a metal matrix composite material (MMC) having approximately 20 - 30 %
Silicon
Carbide by volume, with Aluminum, Nickel and 5 % (+/-) Graphite, with ceramic
surfaces for engaging gears 102 and 104.
Gears 102 and 104, shafts 106 and 108, and pistons 116 and 118, when
assembled, are carried within a surrounding member in the nature of a ceramic
surround
insert 124. Insert 124 has a round cylindrical outer wall and is contained
within a mating
external casing 126. External casing 126 is a steel shrink tube that is shrunk
onto insert
124 such that casing 126 has a tensile pre-load and ceramic insert 124 has a
corresponding compressive preload, such as may tend to discourage cracking of
insert
124 in operation, and may tend to enhance service life. Insert 124 has an
internal, axially
extending cylindrical peripheral wall 130 of a lobate cross-section defining
gear set cavity
therewithin.
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It is preferred that insert 124 be formed of a transformation toughened
zirconia
(TTZ) stabilized with magnesium. However, other materials can be used
depending on
the intended use. Other ceramics that can be used included, but are not
limited to,
alumina or silicon carbide, or alternatively, a plasma coated steel. The
ceramic chosen
S has a similar co-efficient of thermal expansion to gears 106 and 108,
pistons 116 and 118
and surround shrink tube, casing 126, to be able to function at elevated
temperatures. The
ceramic material also tend to be relatively resistant to abrasives. The
combination of high
hardness, and thermal expansion similar to steel is desirable in permitting
operation with
abrasive production fluids at high temperatures.
Pistons 116 and 118 can be made from silicon carbide, as noted above, or
reaction
bonded silicon nitride, tungsten carbide or other suitable hard wearing
ceramic with or
without graphite for lubricity. These materials can be shrunk fit or braised
to a metal
surround of substrate for high temperature applications, or to a metal matrix
material for
low temperature applications.
Gears 102 and 104 are made from a tough material suited to high temperature
and
abrasive use, such as steel alloy EN30B, cast AIOQ or Superimpacto (t.m.). The
material
can be carburized and subjected to a vanadium process for additional
hardening.
Wall 130 has first and second diametrically opposed lobes 132 and 134 each
having an arcuate surface formed on a constant radius (i.e., forming part of
an arc of a
circle), the centers of curvature in each case being the axis of rotation of
stub shafts 106
and 108 respectively, and the radius corresponding to the tip radius of gears
106 and 108.
As such, lobes 132 and 134 describe arcuate surface walls of a pair of
overlapping bores
centered on the axes of shafts 106 and 108 respectively. Pistons 116 and 118
fit closely
within, and are longitudinally slidable relative to, lobes 132 and 134. Wall
130 also has a
pair of first and second diametrically opposed transverse outwardly extending
bulges,
indicated as axial fluid flow accommodating intake and exhaust lobes 136 and
138 which
define respective axially extending intake and exhaust (or inlet and outlet)
passages. As
shown in the cross-sectional view of Figure 8b, when assembled, if the gears
turn in the
counter-rotating directions indicated by arrow 'A' for gear 106 and arrow 'B',
fluid
carried at the intake passage 135 defined between lobe 136 and the waist 121
of pistons
116 and 118 can occupy the cavity defined between successive teeth of gears
106 and
108, to be swept past arcuate wall lobes 132 and 134 respectively. However, as
the gears
mesh, the volume of the cavities between the teeth is reduced, forcing the
fluid out from
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between the teeth and into the exhaust passage 137 defined between lobe 138
and the
waist of piston 118.
Casing 126 has a longitudinal extent that is greater than insert 124, such
that when
insert 124 is installed roughly centrally longitudinally within casing 126,
first and second
end skirts 140 and 142 of casing overhang each end of insert 124 (i.e., the
skirts extend
proud of the end faces of insert 124). Each of skirts 140 and 142 is
internally threaded to
permit engagement by a retaining sleeve 144, 146. Retaining sleeves 144 and
146 are
correspondingly externally threaded, having notches to facilitate tightening,
and an
annular shoulder 148 that bears against whichever type of end plate adapter
may be used.
In the example of Figure 8a, a first end flow adapter fitting, or end plate,
is indicated as
end plate 150, and a second end flow adapter fitting, or second end plate, is
indicated as
152. The internal features of plates 150 and 152 are described more fully
below.
End plate 150 has a first end face 154, facing away from gears 106 and 108,
and a
second end face 156 facing toward gears 106 and 108. Externally, end plate 150
has a
round cylindrical body having a smooth medial portion 158, a first end portion
160 next
to end face 154, and a second end portion in the nature of a flange 162 next
to second end
face 156. Portion 160 is of somewhat smaller diameter than portion 158, and is
externally
threaded to permit mating engagement with, in general, a union nut of a next
adjacent
pump or motor section. Flange 162 has a circumferential shoulder 164 lying in
a radial
plane, such that when retaining ring 144 is tightened within casing 124,
shoulder 148 of
retaining ring 144 bears against shoulder 164, thus drawing end plate 150
toward gears
106 and 108.
Second end face 156 of plate 150 has a seal groove 166 into which a static
seal
168 seats. Seal 168 is of a size and shape to circumscribe the entire lobate
periphery of
internal peripheral wall 130 of insert 124. Face 156 also has a pair of
indexing recesses
170, 171 into which dowels pins 172 and 173 seat. Insert 124 has corresponding
dowel
pin recesses 174, 175, such that when assembled, dowel pins 172, 173 act as an
alignment
means in the nature of indexing pins, or alignment governors, to ensure
alignment of plate
150 with insert 124 in a specific orientation. As described below, end plate
150 has a
number of internal passages, and the correct alignment of those passages with
stub shafts
106 and 108 and with passages 135 and 137 of insert 124 is required for
satisfactory
operation of unit 100. The outward face of piston 116, that is, face 178 which
faces
toward plate 150 (or 152) and away from gears 106 and 108, has a rebate
against which
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an omega seal 180 can bear, with a seal backup 182 located behind seal 180.
When
retaining ring 144 is tightened, seals 180, 182 and 168 are all compressed in
position. If
the direction of rotation of gears 102 and 104 is reversed, the role of intake
and exhaust is
also reversed. The ability to reverse the direction of rotation of the
gearset, or to operate
the gearset as a motor, depends on the seals employed. Omega seals 180 of the
preferred
embodiment are mono-directional seals which tend to resist leakage past face
178 from
passage 137 back to passage 135. They do not work equally well in the other
direction.
End plate 152 has a first end face 184, facing away from gears 106 and 108,
and a
second end face 186 facing toward gears 106 and 108. Externally, end plate 152
has a
round cylindrical body having a smooth medial portion 188, a first end portion
190 next
to end face 184, and a second end portion in the nature of a flange 192 next
to second end
face 186. Portion 190 is of somewhat smaller diameter than portion 188, and is
externally
smooth to permit longitudinal travel of a mating female union nut 194. Portion
190
terminates in an end flange 196 having a shoulder that engages a spiral
retaining ring 198
of nut 192 when nut 192 is tightened on an adjacent fitting of the next
adjacent motor or
pump section. Flange 192 has a circumferential shoulder 200 lying in a radial
plane, such
that when retaining ring 146 is tightened within casing 126, shoulder 148 of
retaining ring
146 bears against shoulder 200, thus drawing end plate 152 toward gears 106
and 108.
First end face 184 is also provided with O-ring seals 197 for sealing the
connection
between its own fluid passages (described below) and the passages of an
adjoining fitting
when assembled.
Second end face 186 of plate 152 has a seal groove 16b into which another
static
seal 168 seats. As above, seal 168 is of a size and shape to circumscribe the
entire
periphery of internal peripheral wall 130 of insert 124. Face 186 also has
another pair of
indexing recesses 170, 171 into which further dowels pins 172 and 173 seat.
Insert 124
has corresponding dowel pin recesses 174, 175, such that when assembled, dowel
pins
172, 173 act as an alignment means in the nature of indexing pins, or
alignment
governors, to ensure alignment of plate 152 with insert 124 in a specific
orientation. As
described below, end plate 152 has a number of internal passages, and the
correct
alignment of those passages with stub shafts 106 and 108 and with passages 135
and 137
of insert 124 is required for satisfactory operation of unit 100. The outward
face of piston
118, that is, face 178 which faces toward plate 152 and away from gears 102
and 104, has
a rebate against which an omega seal 180 can bear, with a seal backup 182
located behind
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seal 180. When retaining ring 146 is tightened, seals 180, 182 and 168 are all
compressed
in position, in the same manner as noted above.
When unit 100 is fully assembled, and in operation, pistons 116 and 118 are
urged
against the end faces of gears 102 and 104 by hydrodynamic pressure, such that
hydraulic
fluid will tend not to seep easily from the high pressure port to the low
pressure port.
Inasmuch as there are neither ball nor journal bearings, and inasmuch as the
body of the
assembly is predominantly hard, abrasion resistant ceramic, with tough,
hardened steel
fittings, the unit is able to operate at relatively high temperatures, that
is, temperatures in
excess of 180 F. The unit may tend also to be operable at temperatures up to
350 F or
higher.
As noted above, each of motor units 82 and 84 and each of pump units 90 and 92
employs a gear assembly unit 100. The difference between motor units 82 and 84
is in
the respective transition plates used between the units. These plates act as
fluid manifolds
by which the various fluids are directed to the correct destinations.
Starting at the top, or upper, end of the string, transport system 48 ends at
a first
manifold, namely motor section inlet plate 80. Motor section 62 includes a
pair of
modular gear assemblies 100, ganged together, and motor section outlet plate
86. A
round cylindrical casing 214 is welded to inlet plate 80 and outlet plate 86,
leaving a
generally annular passageway 216 defined between an outer peripheral wall,
namely the
inner face of casing 214, and the exterior surface of the ganged gear
assemblies, which
are designated as upper motor assembly 82 and a lower motor assembly 84.
As shown in Figures 2c, 2d, 3a, 3b, 3c, 3d, and 3k, motor section inlet plate
80
has a cylindrical body having a medial flange 222 that extends radially
outward to present
a circumferential face about which one end of casing 214 is welded. To the
upward side
of flange 222, there is an externally threaded end portion 224 that mates with
a female
coupling 72 of transport system 48. To the other, downward side of flange 222
there is an
intermediate portion 228 that has a smooth cylindrical surface, and,
downwardmost, there
is an externally threaded end portion 230 that mates with union nut 194 of
upper motor
assembly 82. Taken on the cross-sections of Figure 3c, 3d and 3k, it can be
seen that
inlet plate 80 has first and second parallel, axially extending through bores
232 and 234
defining hydraulic fluid supply and return passages 233 and 235 which
communicate with
transport system supply tubes 75 and 74. Inlet plate 80 also has a pair of
parallel, axially
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extending blind bores 236 and 238 let in from upward face 240, and which
terminate at
dead ends 241 and 242. Porting for bores 236 and 238 is provided by
perpendicular blind
cross bores 244 and 246 extend radially inward through the wall of
intermediate portion
228. When assembled, bores 236 and 238, and cross-bores 244 and 246 define
passageways 237 and 239 which provide a fluid communication pathway between
annular passageway 216 and, ultimately, tubes 76 and 77 of transport system
48.
Upper motor assembly 82 has a union nut 194 as described above, which engages
threaded end portion 230 of motor section inlet plate 80. As shown in Figures
2c and 5c,
plate 150 has a pair of parallel longitudinally extending through bores 250
and 251
defining hydraulic fluid intake and exhaust passages 252 and 253 that
communicate with
the respective intake and exhaust passages 135 and 137 of the positive
displacement gear
assembly 100 containing gears 106 and 108 of unit 82. Taken on the
perpendicular
longitudinal cross-section, plate 150 has a pair of parallel countersunk bores
254 and 256.
1 S Bores 254 and 256 dead end at the blocked interface with motor section
inlet plate 80 in
line with dead ends 241 and 242. Bore 256 is occupied by splined end 114 of
stub shaft
106 of gear 102, such that shaft 106 is an idler. Bore 254 is unoccupied. As
shown in
Figure 4c, an internally splined coupler is indicated as 258. Coupler 258 is
employed
when assembly 82 is an intermediate motor assembly (i.e., neither the top nor
the bottom
unit in a string of several motor assemblies). Coupler 258 is removed when
used in a top
unit such as assembly 82 since there is no shaft above it in the string with
which to
connect, and coupler 258 would otherwise foul the blind end face of plate 80.
As shown in Figure 4b, plate 151 of upper motor assembly 82 has a pair of
parallel longitudinally extending through bores 260 and 261 defining hydraulic
fluid
intake and exhaust passages 262 and 263 that communicate with the respective
intake and
exhaust passages 135 and 137 of the positive displacement gear section
containing gears
106 and 108 of unit 218. Taken on the perpendicular longitudinal cross-section
of Figure
4c, plate 151 has a pair of parallel countersunk bores 264 and 266. Bores 264
and 266 are
open clear through to corresponding countersunk bores of the next adjacent
motor unit,
namely lower motor unit 84. Bore 264 is occupied by splined end 108 of stub
shaft 104
of gear 104. Bore 266 is unoccupied.
Upper plate 270 of lower motor assembly 84 is identical to plate 150 of upper
motor unit 82. Union nut 194 of plate 270 of lower motor assembly 84 engages
the
external thread 268 of plate 151 of upper motor assembly 82. In this case an
internally
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splined transmission coupling shaft 272 engages the downwardly extending
splines of
stub shaft 108 of upper motor assembly 82, and the upwardly extending splines
of stub
shaft 106 of lower motor assembly 84 such that when the upper shaft is driven,
torque is
transmitted by coupling shaft 272 to the lower shaft. The broadened
countersunk portions
of bores 254 and 256 accommodate coupling shaft 272.
Plate 271 of lower motor assembly 84 is shown in Figures 2c, 5b and 5c. It is
identical to plate 151 of upper motor assembly 82 except insofar as it does
not have
hydraulic fluid transfer passages corresponding to passages 262 and 263, but
rather is
dead ended opposite the ends of passages 135 and 137 of unit 100 of assembly
84, thus
closing the end of the hydraulic pump fluid circuit. As a result, the only
ways for
hydraulic fluid to pass from the pressure, or supply side is through the
positive
displacement gear sets of either upper motor assembly 82 or lower motor
assembly 84.
Given the positive engagement of coupling shaft 272, these gearsets are locked
together
to turn at the same rate, and any output torque is available on driven stub
shaft 108 of
lower motor assembly 84.
Motor section outlet plate 86 has a medial, radially outwardly extending
flange
274, an upwardly extending first body end portion 276, and a second,
downwardly
extending second body end portion 278. End portion 276 has an external flange
280 and
a union nut 194 by which it is mounted to the external threads 282 of lower
plate 271 of
lower motor assembly 84. Flange 274 has a circumferential step into which the
bottom
margin of casing 214 seats, and is welded. Second body end portion 278 is
externally
threaded to accept a union nut 283 attached to pump section 64. As shown in
Figures 2c
and 3g, motor outlet plate 212 has a longitudinal bore 282 that extends
inwardly (i.e.,
upwardly, from downward face 284 past the longitudinal position of the upward
facing
shoulder 286 of flange 280. A lateral notch, or aperture 288 is formed in
second end
portion 278 to permit fluid communication between passage 216 and the passage
290
defined by bore 282 and aperture 288. Motor section outlet plate 86 has a
second
longitudinal bore 292 aligned with shaft 108 of lower motor assembly 220, and
a tail
shaft, or transfer shaft, in the nature of driven shaft 294 extends from a
splined coupling
272 mounted to shaft 108 of lower motor assembly 84 to connect with upper pump
assembly 90.
Upper pump assembly 90 is shown in Figures 2c, 3h, 6a, 6b and 6c. Upper pump
assembly 90 has a first, or upper plate 300 and a lower plate 301 to upper and
lower sides
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of a gear assembly 101. As noted above, gear assembly 101 is identical in
construction
to gear assembly 100, but is somewhat larger in diameter as shown in Figure
2c, and has a
thicker shrink fit casing 127. Upper plate 300 has a cylindrical body having a
first,
upward face 302, a second, downward face 304, a first, upward portion 306 next
to face
302 having a flange and a union nut 194 as described above, and a smooth
cylindrical
exterior surface 308. In the same manner as plate 150, upper plate 300 also
has a second,
or lower outwardly stepped cylindrical portion 310 having a smooth surface and
an end
flange 312 to be captured by a retaining ring, or sleeve 144 as described
above, and fixed
in position relative to external pump casing 127. Plate 300 has a first pair
of parallel
longitudinally extending, round cylindrical, through-bores 312 and 314. Bore
312 defines
within its walls is an outflow, or exhaust passage 316. Bore 314 defines
within it an inlet
passage 318, or an inlet manifold leading to gear assembly 100 of upper pump
assembly
90. An cross-bore 320 intersects bore 314 and provides inlet ports by which
production
fluid can enter passage 314. Whereas exhaust passage 316 is open to passage
290 of
motor outlet section plate 86, inlet passage 318 is dead ended at plate 86.
In the perpendicular cross section, shown in Figure 6c, plate 300 has a pair
of first
and second parallel longitudinal countersunk bores 320 and 322, bore 320 being
occupied
by stub shaft 106 of upper pump assembly 90, and bore 322 being unoccupied. An
inwardly splined coupling mates with driven shaft 294 of plate 86 described
above such
that driving rotation of shaft 294 will tend to turn the gearset of upper pump
assembly 90,
thus driving production fluid from passage 318 to passage 316.
Lower plate 301 has a cylindrical body having a first, upward face 332, a
second,
downward face 334, a first, upward portion 336 next to face 332. In the same
manner as
member 151, lower plate 301 also has a first, or upper outwardly stepped
cylindrical
portion 338 having a smooth surface and an end flange 340 to be captured by a
retaining
sleeve 146 as described above, and fixed in position relative to external pump
casing 311.
Lower plate 301 also has a second, lower portion having a threaded cylindrical
exterior
surface 342. Plate 301 has a first pair of parallel longitudinally extending
round
cylindrical, through-bores 344 and 346. Bore 344 defines within its walls an
outflow, or
exhaust passage 348 that is in fluid communication with passage 316 and with
the exhaust
side of the positive displacement gearset of lower pump assembly 92. Bore 346
defines
within it an inlet passage 350, or an inlet manifold leading to gear assembly
100 of lower
pump assembly 92. Inlet passage 350 is open to inlet passage 318, making a
common
inlet manifold passage.
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In the perpendicular cross section, shown in Figure 6C, plate 301 has a pair
of
first and second parallel longitudinal countersunk bores 360 and 362, bore 360
being
occupied by stub shaft 108 of upper pump assembly 90, and bore 362 being
unoccupied.
Lower pump assembly 92 also has an upper plate 370 and a lower plate 371.
Upper plate 370 is identical to upper plate 300. Lower plate 371 is similar to
lower plate
301, but while having drive shaft bores, 372 and 373, is dead ended opposite
the intake
and exhaust passages 135 and 137 of the positive displacement gearset of lower
pump
assembly 92.
A perforated external casing 375 is carried outside upper and lower pump
assemblies 90 and 92, and has ports, or apertures 376 by while production
fluid can enter
and find its way to intake passages 318.
When all of the above units are assembled in their aligned positions, it can
be seen
that when hydraulic fluid is supplied under pressure to motor section 62, the
various
gearshafts are forced to turn, thus driving the upper and lower pump sections
to urge
production fluid from the inlet side, represented by passages 318, to the
outlet or exhaust
side, represented by passages 316. The production fluid is then forced
upwardly through
the series of inter-connected production fluid passages, namely item numbers
290, 216,
237 and 239 to passages 74 and 75 of transport system 48, and thence to the
well head.
Although a preferred embodiment of production unit has now been described,
various alternative embodiments can be used. For example, with appropriate
substitution
of top and bottom plates and with appropriate lengths of casing tubes, a motor-
and-pump
production unit can be assembled with only a single motor unit, or a single
pump unit.
Since the upper motor and pump units respectively have lower end fittings that
correspond to their own top end fittings, it is possible to string together a
large number of
such motor assemblies, or such pump assemblies, in intermediate positions as
may be
required at a given site depending on the desired flowrate and the physical
properties,
viscosity, of the production fluid, such as viscosity. The number of motor
assemblies
need not equal the number of pump assemblies, and may be greater or lesser as
may be
appropriate given the circumstances of the particular well from which
production fluid is
to be extracted.
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Other types of positive displacement gear pumps can also be employed. Figures
8d and 8e show views of a positive displacement gear assembly 400 having a
first, or
internal gear 402, an external ring gear 404 mounted eccentrically relative to
internal gear
402, and a spacer in the nature of a floating crescent 406 mounted in the gap
between
gears 402 and 404. External gear 404 is mounted concentrically about the
longitudinal
axis 401 of gear assembly 400, generally, the axis of rotation of gear 402
being eccentric
relative to axis 401. The internal concave arcuate face 408 of crescent 406 is
formed on a
circular arc having a radius of curvature corresponding to the outer tip
radius of internal
gear 402. The external, convex arcuate face 410 of crescent 406 is formed on a
circular
arc having a radius of curvature corresponding to the tip radius of the
inwardly extending
teeth of ring gear 404. As gears 402 and 404 turn, the interstitial spaces
between the teeth
define fluid conveying cavities, and when the teeth mesh the cavity volumes
are
diminished so that the fluid is forced out. Consequently, as the gears turn,
fluid is
transferred between intake and exhaust port regions 412 and 414.
Alternatively, when a
pressure differential is established between port regions 412 and 414 gear
assembly 400
acts as a motor providing output torque to shaft 416 upon which inner gear 402
is
mcmrtted. In either case, the direction of rotation will determine which is
the intake port,
and which is the exhaust. Shaft 416 is splined at both ends 418 and 420,
permitting
power transfer transmission to and from adjacent pump or motor units.
The gear set formed by gears 402 and 404, crescent 406 and shaft 416 is
mounted
within a round cylindrical annulus, or housing, namely ceramic insert 422,
which is itself
contained with a shrink-fit external steel tube casing 424. As above, casing
424 has a
tensile pre-load, and imposes a compressive radial pre-load on insert 422.
First and second end plates are indicated as 426 and 428. Each has a counter
sunk
eccentric bore 430 for close fitting accommodation of a ceramic bushing 432
which seats
about shaft 416 and has an end face that abuts one face of inner gear 402.
Bore 430 is
sufficiently large at its outer end to permit engagement of an internally
splined coupling
by which torque can be transferred to an adjacent shaft, in a manner analogous
to that
described above. Each of end plates 426 and 428 has a first end face 427 that
locates
adjacent a face of ring gear 404, and has an outer peripheral seal groove and
a static seal
429 seated therein to bear against a shoulder of insert 422. Locating means,
in the nature
of indexing sockets and mating dowel pins 433 determine the orientation of end
plates
3 S 426 and 428 relative to the respective axes of rotation of gears 402 and
404, and to each
other.
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End plate 426 is nominally the upward end plate of the assembly, and has a
flange
434 to be engaged by a retaining ring 436. Retaining ring 436 is externally
threaded and
engages the internally threaded overhanging upward end skirt 437 of casing 424
in the
manner of retainer 44 and skirt 140 described above. A union nut 438 and
retaining ring
439 engage and end face flange 440 in the manner of union nut 194 described
above. End
plate 428 is the same as end plate 426 externally, with the exception that the
distal portion
441 is externally threaded to mate with a union nut of an adjacent pump or
motor
assembly, or other fitting.
Internally, end plates 426 and 428 each have a pair of parallel, round
cylindrical
longitudinally extending bores 442 and 444 let inward from the end face most
distant
from gears 402 and 404, and extending toward gears 402 and 404, defining
respective
internal passageways. Each has an enlarged port 446, 448 in the nature of an
arcuate,
circumferentially extending rebate at the respective end face 427 of plate 426
or 428 that
is located adjacent to gears 402 and 404. These rebates act as intake and
exhaust galleries
for gears 402 and 404, the function depending on the direction of rotation of
the gears.
Given the symmetrical nature of assembly 400, it can be seen that it can be
operated either as a motor or as a pump, and, with appropriate interconnection
transition
plates analogous to plates 80, and 86, several units can be ganged together as
parallel (or,
serial) pump stages or motor stages, with the shafting and splined couplings
permitting
transmission of mechanical torque between the various stages.
A further alternative gear assembly is shown in Figures 8f and 8g as 450. All
of
the components of assembly 450 are the same as those of assembly 400 of
Figures 4c and
4d described above, except that in place of the positive displacement gear
assembly of
gear 402, gear 404 and crescent 406, assembly 450 employs a positive
displacement gear
assembly in the nature of a gerotor assembly 452. Gerotor assembly 452 has an
inner
gerotor element 454 and a mating outer gerotor element 456. Outer gerotor
element 456
is concentric with the longitudinal centerline 458 of assembly 450 generally,
and inner
gerotor element 454 is mounted on an eccentric parallel axis. In the manner of
gerotors
generally, as the gerotor elements turn, variable geometry cavities defined
between
respective adjacent lobes of the inner and outer elements expand and contract,
drawing in
fluid at an intake side 460, and expelling it at an exhaust region 464 (as
before, intake and
exhaust depend on the direction of rotation of the elements). As above,
appropriate
20763676.1
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porting permits assembly 450 to be used as a motor or a pump, and several
units can be
linked together to form a mufti-stage pump or multistage motor. Shafting and
splined
couplings can be used to transfer mechanical torque from stage to stage.
Operation of the foregoing preferred and alternative embodiments of production
units and their associated motor or pump units requires a supply of hydraulic
fluid, and
transport of the production fluid to the surface. To that end, transport
system 48 employs a
mufti-passage conduit that is now described in greater detail. By way of a
general overview,
and referring to Figures 9a, 9b, and 9c, a pipe string "joint" in the nature
of a modular pipe
assembly is shown as 520. It has a casing 522 and an interconnection in the
nature of a male
fitting 524 at one end, and a female fitting in the nature of a female
coupling 526 at the
other, such that a string of modular pipe assemblies 520 can be joined
together. A pipe
bundle 528 is contained within casing 522, and a seal 530 of matching profile
to bundle 528
is clamped between adjacent assemblies 520 when a string is put together.
Notably, the
pipes of bundle 528 lie side by side, rather than being nested concentrically
one within the
other. For the purposes of illustration, the length of the assembly or
assemblies shown is
shorter in the illustrations than in actual fact. In use a typical assembly
length would be 10
or 12 m (32.8 to 39.5 ft), and the pipe bundle diameter would be about 15 cm
(6 in.). Other
lengths and diameters can be used. The longitudinal, or axial direction is
indicated in the
figures by center line axis CL of casing 522.
During deployment or installation, pipe assembly 520 is mounted to another
pipe
assembly, then introduced into a well bore a few feet, another similar section
of pipe is
added, the string is advanced, another string is added and so on. Although
assembly 520 can
be used in a horizontal well bore application, the assembly at the well head
is generally in
the vertical orientation. Thus Figures 9a, 9b, and 9c each have arrows
indicating "Up" and
"Down" such as well rig workers would see at the well head.
Examining the Figures in greater detail, casing 522 is round and cylindrical
and
serves as an external bundle retainer. It is preferred that casing 522 be
shrink fit about
bundle 528. In the preferred embodiment of Figure 9a, casing 522 is made from
mild steel
pipe. The type of material used for the casing may tend to depend on the
application. For
example, a stainless steel or other alloy may be preferred for use in more
aggressive
environments, such as high sulfur wells. Casing 522 has a pair of first and
second ends, 534
and 536. Male fitting 524 is mounted at first end 534. Female coupling 528 is
mounted
about casing 522, and is longitudinally slidable and rotatable with respect to
second end 536.
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A retaining ring 542 is mounted flush with second end 536, and a start flange,
544, is
mounted inboard of ring 542. Start flange 544 is a cylindrical collar having
one turn of a
single external thread 545. As shown in Figure 9c, first and second indexing
dogs 546 and
548, protrude longitudinally, or axially, from first and second ends 524 and
526 respectively.
At corresponding positions indicated by arrows 550 and 552, assembly 520 has
sockets into
which dogs of other mating pipe assemblies can locate. During assembly of a
string of pipes
at the well head, dogs 546 and 548 engage matching sockets in the next
adjacent assemblies,
thus ensuring their relative alignment as the string is assembled.
As shown in Figures 9b and 9c, each of pipe assemblies 520 has four parallel
conduit
members, or pipe sections, in the nature tubes, 554, 556, 558 and 560 arranged
in a bundle
within casing 522. In the Figures 9b and 9c all of tubes 554, 556, 558 and 560
have the
same cross-section, being that shown in Figures l0a and 12. That section has
the shape of a
right angle sector of a circle, that is, a pie-shaped piece approximating a
quarter of a pie,
with smoothly radiused corners. In the preferred embodiment of Figures l0a and
12, tube
560 has an outer arcuate portion 562, having an outside radius of curvature of
2.75 inches to
suit a pipe having an inside, shrink fit diameter of 5.5 inches. Tube 560 also
has a first side
564, and a second side 566 at right angles to first side 564. Arcuate portion
562 and sides
564 and 566 are joined at their respective common vertices to define a closed
wall section,
570. Section 570 has an external wall surface 572, and an internal wall
surface 574, each
having respective first and second straight portions and an arcuate portion,
with radiused
corners.
Section 570 is made by roll forming a round pipe of known pressure rating into
irregular pie shape shown. This can be done in progressive roll forming
stages. Section 570
is a seamless pipe. Other types of pipe can also be used, such as seamed ERW
pipe, or an
extruded pipe capable of holding the pressures imposed during operation.
Internal wall surface 574 defines a passageway, indicated generally as 580,
along
which a fluid can be conveyed in the axial, or longitudinal direction, whether
upward or
downward. When casing 522 is shrunk fit in place, tubes 554, 556, 558 and 560
have a
combined outer surface approximating a circle and are held in place against
each other's
respective first and second external side portions by friction.
3 5 In the cross-section of Figure 9d, a pair of assemblies 520 are shown as
connected in
an engaged or coupled position. Female coupling 526 has a circular cylindrical
body 582
20763676.1
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having an internal bore 584 defined therewithin. At one end body 582 has an
end wall 583
having an opening 585 defined centrally therein, opening 585 being sized to
fit closely about
casing 522. At the other end body 582 has a cylindrical land 586 that has an
internal thread
588 for mating engagement with the external male thread 590 of male fitting
524 of an
S adjacent assembly 520.
Body 582 also has an internal relief 592 defined therein. Relief 592 is
bounded by a
first shoulder 594, on its nominally upward end. As assembled, first shoulder
594 bears
against the upward facing annular end face 598 of start flange 544, and, as
female internal
thread 588 engages male external thread 590, the upper and lower assemblies
520 are drawn
together, compressing seal 530 in the process.
When the upper and lower assemblies 520 are not joined together, female
coupling
526 is backed off such that the first turn of internal thread 588 downstream
of relief 592
engages the single external thread 545 of start flange 544. This results in
female coupling
526 being held up at a height to permit a well worker to make sure that seal
530 is in place
on the downward assembly 520, and indexed correctly relative to dogs 546 and
548, before
the two units are joined together.
Seal 530 is shown in plan view in Figure lla. It has a circular external
circumference 602, with first and second dog locating notches 604 and 606
shown
diametrally opposed from each other, notches 604 and 606 acting as alignment
governors, or
indexing means. When located on the end of a pipe assembly 520, notch 604, for
example,
locates on dog 546, and when two such pipe assemblies are joined, the other
dog, namely
dog 548 of the second pipe assembly, will locate in the opposite notch, namely
notch 606.
Although the preferred embodiment is shown in Figure lla, the notches need not
be on 180
degree centers, but could be on an asymmetric, or offset 90 degrees, such as
may be suitable
for ensuring that the dogs line up as indexing devices to ensure that
adjoining sections of
pipe, when assembled have the correct passages in alignment. Seal 530 has four
quarter pie
shaped openings 610, 612, 614, and 616 defined on 90 degree centers, such as
correspond to
the general shape of the cross-section of passageway 580 of each of tubes 554,
556, 558 and
560. With these openings so defined, seal 530 is left with a four-armed spider
615 in the
form of a cross. A fifth, rather smaller, generally square aperture 618, is
formed centrally in
spider 615, such as may be suitable for permitting the passage of electrical
wires for a
sensing or monitoring device. As ca.n be seen in the sectional view of Figures
llb and llc,
seal 530 has grooves 620 and 622 formed on opposite sides (that is, front and
back, or upper
20763676.1
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and lower as installed), each of grooves 620 and 622 having the shape, in plan
view, to
correspond to the shape of a protruding lip of the end of each of tubes 554,
556, 558 and
560. The mating shapes locate positively, again ensuring alignment, and, when
squeezed
under the closing force or female coupling 526, a seal is formed , tending to
maintain the
integrity, that is, the segregation, of the various passageways from pipe to
pipe as the string
is put together.
The approximate centroids of the passages of tubes 554, 556, 558, and 560 are
indicated as 600. It will be noted that unlike nested pipes, whether
concentric or eccentric,
none of the passages defined within any or the respective pipes is occluded by
any other
pipe, and none of the centroids of any of the pipes fall within the profiles
of any of the other
pipes. Put another way, the hydraulic diameter of each of the pipes is
significantly greater
than the hydraulic diameter that would result if four round cylindrical tubes
were nested
concentrically, one inside the other, with equivalent wall thicknesses. The
useful area within
casing 522 may also tend to be greater since the sum of the peripheries of the
tubes,
multiplied by their thickness may tend to yield a lesser area than the wall
cross-sectional area
of four concentric pipes.
The embodiment of Figure 12 is currently preferred. Such an embodiment has a
number of advantages. First, all of the pipe segments are of the same cross-
section, which
simplifies manufacture, assembly and replacement. Second, in an application
where the
multi-passage conduit assembly so obtained is used to drive a down-hole
hydraulic pump,
one passage can be use to carry hydraulic fluid under pressure, another
passage can be used
to carry the hydraulic fluid return flow, a third passage can carry the
production fluid that is
to be pumped out of the well, and the fourth passage or the central gap can be
used for
electrical cabling, such as may be required for monitoring equipment.
In the side-by-side embodiment of Figure 12, none of the cross-sectional areas
of any
of the individual tube sections overlaps the area of any other, as would be
otherwise be the
case in a nested pipe arrangement. Further, it is a matter of mathematical
calculation that the
centroid of the cross-sectional area of any of the tube sections of the
preferred embodiment
of Figure 12, lies outside the cross-sectional area of any of the other tubes
that are in side-by-
side relationship. The hydraulic diameter, D,, of a passageway is given by the
formula:
Dh - 4A/P
3 5 Where:
A = Cross sectional area of the passage; and
20763676.1
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P = Perimeter of the passage.
In Figure 12, the hydraulic diameter of the tubes is less than the quotient
obtained by
dividing the perimeter of the particular tube by 7z. Similarly the cross-
sectional area of at
least two of the tubes is less than the square of the perimeter divided by 4~.
Various embodiments of the invention have now been described in detail. Since
changes in and or additions to the above-described best mode may be made
without
departing from the nature, spirit or scope of the invention, the invention is
not to be limited
to those details, but only by the appended claims.
20763676.1
