Note: Descriptions are shown in the official language in which they were submitted.
CA 02310477 2000-06-O1
WELL PRODUCTION 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.
Backtground 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
undergound
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 undergound well bores
that include
horizontal and steam assisted gavity 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
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 efl~iciency.
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 e~ciency. 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,
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 infi-astructure - 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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-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
S 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
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
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 cor_structing 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.
S
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
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 h$ving 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,
the axes
lying in a common plane. The first and second gears are mounted to mesh
together in a
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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 an aspect of the invention there is a modular well pipe assembly. There is
a pipe
wall structure having at least first and second passages defined side-by-side
therein. The
1 S pipe wall structure has a first end and a second end. The first and second
ends have
respective first and second end couplings matable with other end couplings of
modular pipe
assemblies of the same type. The end fittings have alignment fittings for
aligning the first
and second passages with corresponding first and second passages in other
modular pipe
assemblies of the same type.
In an additional feature of that aspect of the invention, the pipe wall
structure
includes a hollow outer casing and at least first and second conduits for
carrying fluids
mounted side-by-side within the casing. In another additional feature of that
aspect of the
invention, one of the end couplings has a seal mounted thereto. The seal has
porting defined
therein corresponding to the passages. The seal is placed to maintain
segregation between
the passages when the modular pipe assembly is joined to another modular pipe
assembly of
the same type. In yet another additional feature, the end coupling is
engageable with a
mating modular pipe assembly to compress the seal.
In still another additional feature, the pipe wall structure includes a first
conduit
member and a second conduit member mounted within the first conduit member.
The first
conduit member has a continuous wall. The continuous wall has an inner surface
defining a
periphery of an internal space. The second conduit member occupies a first
portion of the
internal space of the first conduit member and leaves a remainder of the
internal space of the
first conduit member. The second conduit member has a continuous wall. The
continuous
wall of the second conduit member has the second side by side passage defined
therewithin.
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The continuous wall of the second conduit has an external surface. A portion
of the external
surface of the second conduit member is formed to conform to a first portion
of the inner
surface of the first conduit member, and being located thereadjacent. The
first passage is
defined within the remainder of the internal space of the first conduit
member. In still yet
another additional feature, the inner surface of the first conduit member has
a second
portion bounding a portion of the first passage.
In another additional feature of that aspect of the invention, the inner
surface of the
first conduit member has a second portion. The external surface of the second
conduit
member has a second portion. The second portion of the inner surface of the
first conduit
member and the second portion of the external surface of the second conduit
member
co-operate to bound at least a portion of the first passageway. In yet another
additional
feature of that aspect of the invention, the first conduit member has a round
cylindrical
cross-section. The second conduit member continuous wall has a portion lying
along a first
chord of the cylindrical cross-section. In still another additional feature,
the chord is a
diametrical chord. In another additional feature, the second conduit member
has another
portion lying along a second chord of the cylindrical cross-section. In a
further additional
feature of that aspect of the invention, the second conduit member occupies a
sector of the
cylindrical cross-section between the first and second chords.
In yet a fizrther additional feature, the pipe wall structure includes a third
conduit
member. The third conduit member has a continuous wall having a third side-by-
side
passage defined therewithin. The third conduit member has an external surface.
A portion
of the external surface is shaped to conform to, and is located adjacent to a
second portion of
the inner surface of the first conduit member.
In still a fizrther additional feature, the pipe wall structure includes a
third conduit
member. The third conduit member has a continuous wall having a third side-by-
side
passage defined therewithin. The second conduit member has an internal wall
surface. The
third conduit member continuous wall has an external surface. A portion of the
external
surface of the third conduit member is shaped to conform to, and is mounted
against, a
portion of the internal wall surface of the second conduit member.
In another additional feature of that aspect of the invention, the pipe wall
structure
3 S includes a first conduit member, a second conduit member, and a third
conduit member.
The second and third conduit members are mounted side-by-side within the first
conduit
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member. In yet another additional feature, the second conduit member has a
circular cross-
section. In still another additional feature, the second and third conduit
members have
circular cross-sections. In a further additional feature, a fourth conduit
member is mounted
within the first conduit member. In still a further additional feature, the
first conduit
S member has a circular internal wall surface. The second, third and fourth
conduit members
have circular cross sections and are mounted in tangential engagement with the
circular
internal wall surface of the first conduit member. In another additional
feature of that
aspect of the invention, each of the second, third and fourth conduit members
is tangent to
at least one of the others. In still another additional feature, at least one
of the second and
third conduit members is hexagonal in cross-section.
In yet another additional feature, at least one of the second and third
conduit
members is pie shaped in cross-section. In a further feature of that aspect of
the invention,
the pie shape is chosen for the set of pie shapes consisting of (a) a half of
a pie; (b) a third of
a pie; (c) a quarter of a pie; and (d) a sixth of a pie.
In another feature of that aspect of the invention, the pipe wall structure
includes a
first conduit member and a second conduit member mounted within the first
conduit
member. The second conduit member has a continuous wall bounding the second
passage.
The second passage has a periphery and a cross-sectional area. The second
conduit member
continuous wall has an internal surface defining the periphery of the second
passage. The
second passage has a hydraulic diameter that is less than the dividend
obtained by dividing
the perimeter by ~. In another additional feature, the second conduit member
is free of
convex portions.
In another additional feature of that aspect of the invention, the pipe wall
structure
includes a first conduit member and a second conduit member mounted within the
first
conduit member. The second passage has a perimeter 'P', a cross-sectional area
A and a
hydraulic diameter D~. The second conduit member has a continuous wall having
an
inside surface defining the perimeter 'P' of the second passage and A <
(P2/4n). In still
another additional feature, the second conduit member is free of convex
portions.
In yet another additional feature, the pipe wall structure includes a first,
outer,
conduit member having an inner wall surface and a second, inner, conduit
member mounted
within the first conduit member. The inner conduit member has an outer wall
surface. The
inner wall surface of the outer conduit member and the outer wall surface of
the inner
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conduit member bounds a region intermediate the outer conduit member and the
inner
conduit member. A third conduit member defines a third passage therewithin in
side-by-side
relationship to the second passage. The third conduit member is located in the
region
intermediate the inner wall surface of the outer conduit member and the outer
wall surface of
the inner conduit member.
In another additional feature of that aspect of the invention, the third
conduit
member has an outer wall surface. The outer wall surface of the third conduit
member has a
first portion engaging the inner wall surface of the outer conduit member and
a second
portion engaging the outer wall surface of the inner conduit member. In still
another
additional feature, the first portion of the third conduit member is shaped to
conform to a
portion of the inner wall surface of the outer conduit member. The second
portion of the
third conduit member is shaped to conform to a portion of the outer wall
surface of the inner
conduit member. In yet another additional feature, the region between the
outer and inner
1 S conduits is annular. In another additional feature, the inner conduit
member is concentric to
the outer conduit member. In yet another additional feature, an annulus is
defined between
the inner and outer conduit members and the third conduit member occupies a
sector of the
annulus. In another additional feature of that aspect of the invention, a
plurality of conduit
members each occupy sectors of the annulus.
In a further aspect of the invention, there is a fluid displacement apparatus
having
(a) a motor unit having a first gearset having an output shaft, the output
shaft having an
axis of rotation defining an axial direction; an inlet by which fluid can flow
to the first
gearset; and an outlet by which fluid can flow away from the first gearset;
(b) a gear
pump unit mounted axially with respect to the motor unit, the pump unit having
a second
gearset connected to be driven by the output shaft of the first gearset; an
inlet by which
production fluid can be flow to the second gearset; and an outlet by which the
production
fluid can flow away from the second gearset; and (c) a transport apparatus
having a first
end and a second end, the second end being connected axially relative to the
motor unit
and the pump unit. The transport apparatus has a first passageway defined
therein in fluid
communication with the inlet of the motor unit by which fluid under pressure
can be
directed to the first gearset to turn the output shaft; and at least a second
passageway
defined therein in fluid communication with the outlet of the pump unit by
which the
production fluid from the second gearset can be conveyed to the first end of
the transport
apparatus.
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In an additional feature of that aspect of the invention, the apparatus
includes a
plurality of the motor units connected axially together to drive the output
shaft. In
another additional feature, the apparatus includes a plurality of the gear
pump units
connected axially together.
S
In another additional feature, the transport apparatus has at least a third
passageway defined therein. The third passageway is in fluid communication
with the
outlet of the first gearset to permit return fluid from the first gearset to
be earned to the
first end of the transport apparatus. In still another feature, the transport
apparatus has
another passageway defined therein by which electrical cabling can extend
between the
first and second ends.
In still another feature, the first and second passageways extend in side-by-
side
relationship. In a further feature, the transport apparatus includes a bundle
of conduits
1 S defining the passageways, the bundle being mounted within a retainer. In
yet another
feature, the transport apparatus includes a plurality of modular pipe joints
connected
together in a pipe string. In another feature, the gear pump unit is free of
ball and roller
bearings.
In still another feature, the motor unit is mounted in a cylindrical housing,
the
housing having a production fluid passageway defined therein, the production
fluid
passageway being in fluid communication with the outlet of the second gearset
and with
the second passageway of the transport apparatus to permit production fluid
from the gear
pump to flow in the axial direction past the motor unit. In a further feature,
the gear
pump unit is mounted in a cylindrical housing, the cylindrical housing having
porting
defined therein to permit production fluid to flow to the inlet of the gear
pump unit.
In a further feature of that aspect of the invention, the fluid displacement
apparatus includes a plurality of the motor units mounted axially together and
a plurality
of the gear pump units mounted axially together. Each of the motor units has
an axially
extending pressure passage defined therein communicating with the inlet
thereof, and an
axially extending return passage defined therein communicating with the outlet
thereof.
The pressure passages of the motor units are in fluid communication to form a
common
high pressure passageway. The return passages of the motor units are in fluid
communication to form a common low pressure passageway; and a plate is mounted
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between the motor units and the gear pump units to close ofd the high pressure
and low
pressure passages from the pump units.
In still 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
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. A gear pump is connected
to the
first end of the 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 that extends between the
first and
second ends thereof. The transmission member is connected to permit the gear
pump be
driven from the wellhead. The gear pump is operable to urge production fluid
from the
first end of the transport assembly to the wellhead.
1 S In another aspect of the invention, there is a method of moving production
fluid
from a well to a wellhead. the method includes the steps of (a) mounting a
gear pump to
a first end of a transport apparatus; (b) introducing the first end of the
transport apparatus
into the well and locating the gear pump in the well; and (c) 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. In still another feature of
the invention,
the method includes the steps of (a) mounting an hydraulic motor to the gear
pump; (b)
providing a first passageway in the transport apparatus for carrying
production fluid from the
production region to the wellhead; (c) providing a second passageway in the
transport
apparatus for carrying hydraulic fluid to the hydraulic motor; and (d)
supplying hydraulic
fluid under pressure through the second passageway to operate the hydraulic
motor and the
gear pump. In a further additional feature, the method includes the step of
providing a third
passageway in the transport apparatus and directing a return flow of hydraulic
fluid from the
hydraulic motor through the third passageway to the well head.
In another additional feature, the method includes the steps of preparing a
well bore
3 5 having a horizontal production region, and introducing the gear pump into
the horizontal
production region. In another feature, the method includes the steps of (a)
preparing a
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horizontal production region of the well; (b) preparing a well bore above the
horizontal
production region; (c) introducing steam into the well bore, and (d) the step
of driving the
gear pump follows the step of introducing the steam into the well bore. In
still another
additional feature, the transport apparatus is a modular pipe joint apparatus
and the method
includes the step of incrementally introducing one pipe joint after another
into the well. In
another additional feature, the step of introducing includes passing the gear
pump and the
pipe joints through a well head blow out preventer.
These and other aspects and features of the invention are described herein
with
reference to the accompanying illustrations.
Brief Description of the Drawing
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
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 - 46' 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;
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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 - 5b' of Figure
5a;
Figure 5c shows a cross-section on section 'Sc - Sc' of Figure
Sa;
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 multi-passage
pipe assembly
according to an aspect of the present invention;
Figure 9b shows an isometric view of a pair of the multi-passage
pipe assemblies
of Figure 9a joined together;
Figure 9c shows an exploded isometric view of the pair of
multi-passage pipe
assemblies of Figure 9b in a separated condition;
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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;
Figure l lc is a detail of a portion of the cross-section of the seal of
Figure l lb;
Figure 12a shows an isometric view of an alternate assembly to that of Figure
9a;
Figure 12b is a detail view of a seal for the assembly of Figure 12a;
Figure 12c is a detail of a portion of the assembly of Figure 12a as
assembled;
Figure 13a is a plan view of a seal retainer for the pipe assemblies of Figure
12a;
Figure 13b is a side view of the seal retainer of Figure 13a;
Figure 13c is a detail of a cross-section of the seal retainer of Figure 13a;
Figure 14a is a plan view of a seal for the pipe assemblies of Figure 12a;
Figure 14b is a diametral cross-section of the seal of Figure 14a;
Figure 14c is a detail of a portion of the cross-section of the seal of Figure
14b;
Figure 14d is a plan view of an alternative seal for the assembly of Figure
12a;
Figure 14e is a diametral cross-section of the seal of Figure 14d;
Figure 14f is a detail of a portion of the cross-section of the seal of Figure
14e;
Figure 15a shows a cross-sectional view of the tube assembly of Figure 9a
taken
on section '15a - 15a';
Figure 15b shows a cross-sectional view of an alternate tube assembly to that
of
Figure 15a having a pair of semi-circular tubes mounted side-by-side;
Figure 15c shows a cross-sectional view of an alternate tube assembly to that
of
Figure 15a, having three passages, one being larger than the other two;
Figure 15d shows a cross-sectional view of an alternate tube assembly to that
of
Figure 15b, having two tubes, one being larger than the other, the tubes
meeting on a chord of a circle offset from the diametral plane;
Figure 15e shows a cross-sectional view of an alternate tube assembly to that
of
Figure 15d, having two tubes, one being larger than the other two, the
tubes meeting on radial planes;
Figure 16a shows a cross-sectional view of an alternate tube assembly to that
of
Figure 15a, having three equal sized passages with radially extending
webs;
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Figure 16b shows a cross-sectional view of an alternate tube assembly to that
of
Figure 15a, having three unequal tubes with radially extending webs;
Figure 17a shows a cross-sectional view of an alternate tube assembly to that
of
Figure 15a, having six equal pie shaped passages;
Figure 17b shows a cross-sectional view of an alternate tube assembly to that
of
Figure 15a, having seven hexagonal tubes;
Figure 18a shows a cross-sectional view of an alternate tube assembly to the
tube
assembly of Figure 15c, in which the largest passage occupies more than
half the tube area;
Figure 18b is similar to Figure 18a, but shows a tube assembly having three
tubes,
and in which one tube occupies a minor sector of the tube area;
Figure 18c shows a cross-sectional view of an alternate tube assembly to that
of
Figure 15a, having two unequal pairs of tubes with non-radial webs;
Figure 18d shows a cross-sectional view of an alternate tube assembly to that
of
Figure 15a, having four unequal tubes;
Figure 19a shows a cross-sectional view of an alternate tube assembly to that
of
Figure 15a, having two round tubes within a round casing;
Figure 19b shows a cross-sectional view of an alternate tube assembly to that
of
Figure 15a, having three round tubes within a round casing;
Figure 19c shows a cross-sectional view of an alternate tube assembly to that
of
Figure 15a, having four round tubes bundled within a circular outer wall;
Figure 20a shows a cross-sectional view of an alternate tube assembly to that
of
Figure 15a, having two equal outer tubes arranged about a central tube;
Figure 20b shows a cross-sectional view of an alternate tube assembly to that
of
Figure 15a, having two unequal outer tubes arranged about a central tube;
Figure 21a shows a cross-sectional view of an alternate tube assembly to that
of
Figure 15a, having three equal outer tubes arranged about a central tube;
Figure 21b shows a cross-sectional view of an alternate tube assembly to that
of
Figure 21a, having three unequal outer tubes arranged about a central tube;
Figure 22a shows a cross-sectional view of an alternate tube assembly to that
of
Figure 15a, having four equal outer tubes arranged about a central tube;
Figure 22b shows a cross-sectional view of an alternate tube assembly to that
of
Figure 15a, having four outer tubes, one larger than the others, arranged
about a central tube;
3 S Figure 22c shows a cross-sectional view of an alternate tube assembly to
that of
Figure 15a, having four unequal outer tubes arranged about a central tube;
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Figure 23a shows a cross-sectional view of an alternative pipe assembly to
that of
Figure 15a having a semi-circular tube nested within a circular tube;
Figure Z3b shows a cross-sectional view of an alternate pipe assembly to that
of
Figure 23a, having two pie shaped side-by-side tubes nested within a
circular tube;
Figure 23c shows a cross-sectional view of an alternate pipe assembly to that
of
Figure 23a, having three pie shaped side-by-side tubes nested within a
circular tube;
Figure 23d shows a cross-sectional view of an alternate pipe assembly to that
of
Figure 23a, having two circular side-by-side tubes nested within a circular
tube;
Figure 23e shows a cross-sectional view of an alternate pipe assembly to that
of
Figure 23a, similar to that of Figure 20a, but having one of the non-
circular tubes removed;
1 S Figure 24a shows a cross-sectional view of an alternate pipe assembly to
that of
Figure 23a, having a pie shaped tube nested within a semi-circular tube,
nested within a circular tube;
Figure 24b shows a cross-sectional view of an alternate pipe assembly to that
of
Figure 24a, having a pair of pie shaped tubes nested side-by-side within a
semi-circular tube, nested within a circular tube; and
Figure 25 shows cross-sectional views of extruded pipe assembly cross-sections
providing alternatives to the pipe assembly of Figure 15a.
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.
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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 R 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 3b 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
system 42 at the well head, in the nature of a motor 44 that drives a
hydraulic pump 46.
A transport system 48 carnes 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
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) carried 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
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-22-
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
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
(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.
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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 20, 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
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
3 S 106 and 108.
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Alternative embodiments of pistons can be used, as shown in Figures 8h and 8i,
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 (lVflNIC) 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 earned within a surrounding member in :he 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.
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
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.
20743432.3
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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
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.
3 S 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
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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
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 seal 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
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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 166 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 132 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
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.
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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, 3x, 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
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.
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
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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
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
3 S lower motor assembly 84.
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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, 3b, 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
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.
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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.
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.
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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.
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
20743432.3
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acts as a motor providing output torque to shaft 416 upon which inner gear 402
is
mounted. 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
426 and 428 relative to the respective axes of rotation of gears 402 and 404,
and to each
other.
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
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-34-
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
porting permits assembly 450 to be used as a motor or a pump, and several
units can be
linked together to form a multi-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
multi-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
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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.
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, protzude 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 15a. 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
15a, tube
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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.
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
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
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 oil 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
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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 can 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
and lower as installed), each of grooves 620 and 622 having the shape, in plan
view, to
con espond 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,
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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 15a 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
mufti-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.
Figures 12a to 12c show an alternative embodiment to pipe assembly 520, namely
pipe assembly 521. As above, the general arrangement of quarter-pie shaped
tubes, the use
of retaining collars, and the use of male and female fitting to draw adjacent
pipe joints
together is generally as described above. Assembly 521 differs from assembly
520 in that
one pair of the pie shaped pipes 525 is longitudinally stepped relative to
another pair 527,
permitting the elimination of dogs 546 and 548. To accommodate this step, each
of pairs
525 and 527 is provided, at its joining interface with a corresponding
adjacent pair of an
adjacent pipe joint, with a pair of seals 529, 531, and a seal retainer 533.
In the example
shown in Figures 12a, 12b, 13a, 13b and 13c, seal retainer 533 is a frame
having a semi-
circular shape, in plan view, with a pair of quarter-pie shaped openings 535,
537 defined
therein. The peripheral wall of each of openings 535 and 537 has an inwardly
protruding
medial rib, or ridge, 539 having upward and downward facing shoulders 541.
Two alternative examples of seal are shown for engaging, that is, seating
within,
retainer 533. In Figures 14a, 14b and 14c, a quarter-pie shaped seal 543 has
axl internal
peripheral arcuate face 547 that, when installed, faces, and defines a portion
of the flow
passageway for, the fluid to be transported. On the opposite, or back face,
seal 543 has a
pair of outwardly protruding external ribs 549, defining a square shouldered
rebate between
them sized to engage ridge 539 of retainer 533. To either longitudinal side of
ribs 549, seal
543 has a pair of pipe-wall engaging lands, 551. The skirts formed by the
distal edges 553
of lands 551 are flared outward a small amount (for example, about 4 degrees).
In use,
engagement with the mouth of a similarly shaped tube will necessitate inward
deflection of
the flared ends, forming a snug interference fit. Alternatively, as shown in
Figures 14d, 14e
and 14f, a quarter-pie shaped seal 553 is generally similar to seal 543,
having a relief 555 for
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engaging ridge 539, but rather than having square shoulders, have tapered
shoulders 557
leading to lands 559. In use seal 543, or 553, is mated with each aperture in
retainer 533,
and seated on the end of one of the tube pairs. The flat faces 561 of retainer
533 bear against
the end faces of the respective tube pairs.
It is not necessary that equal pairs of tubes be stepped to give an indexing
feature to
the assembly. For example, rather than a pair, a single pipe could be advanced
to give a
unique assembly orientation. A number of possible alternative configurations
are possible.
An advantage of the example shown in Figures 14a, 14b and 14c is that it
permits use of a
single type of symmetrical end seal, in a single type of retainer. That is,
fewer parts need to
be stocked, and the parts that are stocked can be inserted with either face up
or down to
achieve the same fit.
Alternative Embodiments of Conduit Members
In the alternative side-by-side embodiments of Figures 15a to 23e, 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 15a, or the alternative
embodiments of
Figures 15b to 23e, lies outside the cross-sectional area of any of the other
tubes that are in
side-by-side relationship. The hydraulic diameter, Dh of a passageway is given
by the
formula:
Dh - 4A/P
Where:
A = Cross sectional area of the passage; and
P = Perimeter of the passage.
In each side-by-side example, whether in Figure 15a or any of Figures 15b to
23e,
the hydraulic diameter of at least two of the tubes are less than the quotient
obtained by
dividing the perimeter of the particular tube by ~. Similarly, in each of the
side-by-side
examples provided in Figure 7 and Figures 8a to 8n, the cross-sectional area
of at least two
of the tubes is less than the square of the perimeter divided by 4n.
3 5 In the alternative embodiment of Figure 15b, a pipe assembly 650 has a
pair of semi-
cylindrical tubes 652 and 654 nested in a side-by-side manner within an outer
casing 656.
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Each of semi-cylindrical tubes 652 and 654 has a tube wall that has a flat
portion 658, and an
arcuate portion 660, joined at smoothly radiused corners to form a semi-
circular D-shape as
shown. As above, tubes 652 and 654 as seamless steel tubes of a known pressure
rating that
have being roll formed through progressive dies to achieve the smoothly
radiused D-shape
shown.
The tube walls of tubes 652 and 654 each have an internal surface 662 or 664
defining an internal passageway 666, 668 along which fluids can be conducted.
Each
passageway has a cross-sectional area, neither cross-sectional area
overlapping the other, and
neither having a centroid lying within the cross-sectional area of the other.
The external
surfaces of flat portions 658 of tubes 652 and 654 engage along a planar
interface lying on
a diametral plane of casing 656. As above, casing 656 is shrink fit about
tubes 652 and 654,
creating a tensile pre-load in casing 656, and a compressive pre-load in
arcuate portions 660
of tubes 652 and 654. A seal of suitable shape is used in place of seal 530
described above
at the connections between successive tube assemblies.
In this kind of two tube embodiment, water (or another suitable working fluid)
can
be used as the working fluid to drive the downhole pump, such that one passage
such as
passage 668 carries water under pressure down to the pump, and the other
passage 666
carries both the production fluid and the return flow of the water used to
drive the pump.
Such a system may tend to require a relatively large supply of clean working
fluid. The
working fluid and the production fluid will tend to need to be separated at
the surface, so a
significant settling or other separation system may tend to be required.
In a two tube arrangement, it is not necessary that the two tubes have cross-
sections
of equal area. For example, as shown in pipe assembly 670 of Figure 15d,
depending on the
pressures in the tubes, it may be desired that the pressure supply flow (in
the downward
passage) be rather smaller than the return flow (in the upward passage), which
carries both
the working fluid and the production fluid. Since line losses vary with the
square of mean
flow velocity, it may be desired for the smaller volumetric flow to be carned
in a smaller
tube. Hence down flow tube 672 is smaller in cross-sectional area than return
flow tube 674.
That is, the corresponding flat portions 676 and 678 of tubes 672 and 674 do
not have a
diametral surface, but rather run along, and have an abutting interface at, a
chord 675 offset
from the diametral centerline 679.
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Although the offset in Figure 15d is achieved along an offset chord, this need
not be
the case. As shown in Figure 15e, a pipe assembly 680 has an outer casing 682
shrink fit
about two internal tubes 684 and 686. The smaller of these, tube 686, has the
shape of a pie
shaped piece, with radiused corners, subtending a minor arc of the circular
inner face of
casing 682. The large piece, 684, has the shape of the remainder of the pie,
with smoothly
radiused corners. The side portions of tubes 684 and 686 meet along planar
interfaces that
extend radially relative to the axial centerline of casing 682.
In the alternative embodiment of Figure 16u, a pipe assembly 690 has a set of
three
tubes 691, 692 and 693 of equal passage size. Each of tubes 691, 692 and 693
occupies one
third of the area within shrink fit casing 694, and has side wall portions 696
and 697 that
extend radially outward from the center of casing 694 and an arcuate
circumferential portion
695 that is placed in mating engagement with casing 694. The inner face 698 of
each of
tubes 691, 692 or 693 defines an internal passageway, 699, having a cross
sectional area
that is roughly 120 degrees of arc, or 1/3 of the area of casing 694, less the
thickness of the
walls forming the periphery of passageway 699.
A three pipe embodiment of pipe assembly is shown in Figure 15c as 700. In a
three
pipe embodiment, one pipe can be used, for example, to carry hydraulic fluid
under pressure,
such as to drive a downhole hydraulic pump; a second pipe can provide the
return line; and
the third pipe provides the conduit by which production fluid is conveyed to
the surface.
This may tend to avoid mixing of the return and production fluid flows in the
return of a two
pipe system, and may also tend to avoid the need for a large settling or
separation system at
the discharge end of the production floe pipe. Alternatively, the working
fluid can be fed
down one pipe, production fluid and the return of the working fluid can be by
a second of
the three pipes, and the third pipe can carry electronic cables.
In pipe assembly 700 a first roll-formed tube of known pressure rating is
shown as
701. It is roughly semi-circular in shape, with radiused corners. It has a
flat portion 702 and
an arcuate portion 703 for mating engagement within the round cylindrical
inner surface of a
shrink fit casing 704. Second and third tubes 706 and 708 have the shape of
quarter pie
pieces, each with radiused corners. Each has first and second flat 710, 711
portions meeting
at a right angled radiused corner, the flat portions extending more or less
radially outward to
meet an arcuate portion 712 suited for engaging an arc of the circumferential
inner face of
casing 704. The various flat portions of tubes 701, 706 and 708 meet on radial
planes of
casing 704. Each of tubes 701, 706 and 708 has an internal face defining the
periphery of a
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passageway, 714, 715, 716 respectively, each passageway having a cross-
sectional area
defined within that periphery.
The various pipes need not necessarily be of the same size, particularly if
the flow of
working fluid for driving the pump is under high pressure, but relatively low
flow. It may be
preferable for the cross-section of the passage for conveying the production
fluid, namely
714 to be larger than the others, as shown in the embodiment of Figure 15c,
particularly
since line losses tend to vary in turbulent flow as the square of the mean
velocity of the fluid,
and the mean velocity of the fluid is determined by dividing the volumetric
flow by the
passage area. Given that the pressure and return lines are carrying very
nearly the same
volumetric flow rate of a largely incompressible fluid (differing only to the
extent of the
pressure difference multiplied by the bulk modulus of compression of the fluid
at the given
operating temperature), pressure and return passages 715 and 716 can most
conveniently be
made the same size, as shown in this embodiment.
As with the example of Figure 15c, the pie-shaped tubes need not be of equal
size.
Thus, in Figure 16b, a pipe assembly 720 has an external casing 722 and three
internal tubes
724, 725 and 726, which are in other ways similar to tubes 691, 692 and 693,
except that
tube 724 subtends a pie shape of about 1/6 of casing 722, tube 725 subtends a
pie shape of
about 1/3 of casing 722, and tube 726 subtends about 1/2 of casing 722. In
this case, if for
example a gas under pressure such as air or steam, or an inert gas, is used as
the driving fluid
to operate a pneumatic pump, the return line, at lower pressure, may need to
have a larger
cross-sectional area to keep gas velocity somewhat lower.
Figure 17a shows a pipe assembly 730 having a set of six equal side-by-side
pie-
shaped tubes 732 contained within an external cylindrical casing 734. Each of
tubes 732 is a
roll-formed tube similar to tube 726, above. As the number of tubes in the
bundle increases,
and given the need for a reasonable radius on the roll-formed tubes, the size
of the gap 733 at
the center of the bundle increases, and becomes a significant passageway for
cables or other
wiring as may be desired. A central tube can also be obtained as shown in
Figure 17b in
which a tube assembly 735 has a cluster of smoothly radiused, side-by-side
hexagonal tubes
736 retained within an external casing 738. In such an assembly each of the
available tubes
can be used for a different function, or, alternatively, the operator can
select two or more
hexagonal tubes for one purpose, another pair for another purpose, and the
remaining two for
yet some other purpose or purposes. The selection of tubes is associated with
the provision
of an appropriate downhole manifold and well-head manifold, and suitable seals
between
20743432.3
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' - 43 -
successive the pipe assembly sections to maintain segregation between the
various
passageways.
Figures 18a and 18b show alternative configurations to that of Figure 15c. In
Figure
18a a pipe assembly 740 has an external casing 742 and three internal tubes
744, 745 and
746, each having an internal wall defining the periphery of an internal
passage. Tubes 745
and 746 are minor images of each other, and tube 744 is rather larger such
that the flat
interface of tube 744 with tubes 745 and 746 lies along a chord 748 offset
from the diametral
plane 747 of casing 742. Tube 744 occupies more than half of the inner cross-
sectional area
of casing 742. Figure 18b shows a pipe assembly 750 having a casing 752 and
three internal
tubes 754, 755 and 756, each having an internal wall defining the periphery of
an internal
passage. Tubes 755 and 756 are minor images of each other, and tube 754
occupies the
remainder of the cross-sectional area not occupied by tubes 755 and 756. The
flat interface
of the external surface of the flat portion of tube 754 with the external
surface of flat portions
1 S of tubes 755 and 756 lies along a chord 758 offset from the diametral
plane 757 of casing
752 such that tube 754 occupies less than half of the cross-sectional area of
casing 752.
Figure 18c shows an embodiment of a four tube variation of the embodiments of
Figures 18a and 18b. In this instance a tube assembly 760 has a retainer in
the nature of an
external casing 762 and four internal roll-formed tubes 764, 765, 766, and
767. Tubes 764,
765, 766 and 767 are of unequal sizes. The planar interface between the
external surfaces of
tubes 764 and 765 lies on a chord that is offset from a diametral plane 768 by
a step distance
a, and the interface between the external surfaces of tubes 766 and 767 is
offset from
diametral plane 768 by a step distance (3. In the most general case, ~i is not
equal in
magnitude to a.
Figure 18d shows a further variation of an embodiment of a four tube pipe
assembly
770, having a casing 772 and four tubes 774, 775, 776, and 777. Tubes 774,
775, 776 and
777 are of unequal sizes. The planar interface between the external surfaces
of tubes 774
and 775 lies on a chord that is offset from a diametral plane 778 by a step
distance fir. Tubes
776 and 777 are pie shaped, and are unequal in size.
In each case, by providing tubes in a side-by side configuration, overall
resistance to
fluid flow in the assembly may tend to be reduced over that achievable with
concentric
nested pipes. It may tend also to reduce the need for spiders or other means
for maintaining
specific spacing of the pipes that might otherwise be required for concentric
pipes. That is,
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the pipes are formed such that they can lie side-by-side within the outer
retainer. The shape
of the tube walls can be adjusted by roll forming to achieve planar interfaces
between the
internal pipes to give hydraulic diameters that are less than the result
obtained by dividing
4A/n, while continuing to use pipes that have either flat portions or concave
arcuate
portions. The examples described thus far do not have convex peripheral
portions, such as
would occur with a re-entrant curve. In a re-entrant curve, (a) the local
radius of curvature
extends away from the wall portion toward a local focus point and (b) the
local focus point
of the radius of curvature lies outside the cross-sectional area of the
particular pipe.
In some instances it may be acceptable merely to place round pipes side-by-
side
within a casing. In Figure l9st a two-tube pipe assembly is shown as 780. It
has a round
cylindrical outer casing 782 and a pair of round, internal tubes 783 and 784
mounted within
casing 782 and tangent to the inside surface of casing 782. Each of tubes 783
and 784 has a
known pressure rating, and each has an internal passageway 785, 786 having a
periphery and
a known cross-sectional area. The remaining spaces 787, 788 between the
internal wall of
casing 782 and the outer wall surfaces of tubes 783 and 784 can be used to
carry services
such as electrical cabling. In the alternative, if casing 782 has a known
pressure rating,
fluids under pressure can be carried in the passageways formed by spaces 787
and 788,
although they have less favourable hydraulic diameters and cross-sectional
shapes than
might otherwise be desired.
Figure 19b shows a pipe assembly 790 that dii~ers from pipe assembly 780 in
that it
has an outer casing 792 housing a set of three internal tubes 793, 794 and 795
of round
cylindrical section, and of somewhat smaller diameter than tubes 783 and 784.
Once again,
casing 792 can be a pipe of known pressure rating, and the interstitial spaces
796, 797, and
798 can be used to carry electrical or other services. Figure 19c shows a
further variation of
pipe assembly 800, that differs from assemblies 780 and 790 by having a casing
802 and
four circular internal tubes 803, 804, 805 and 806.
In some cases it is also possible to improve hydraulic properties of a pipe
assembly
even when one or more tubes in a pipe bundle pipe have local portions that
have re-entrant,
or convex walls. Figure 20st shows a three-tube pipe assembly 810 that has a
shrink fit
round cylindrical outer casing 812. A central round cylindrical pressure rated
seamless steel
tube 814 is located concentrically to casing 812. A pair of half doughnut, or
kidney shaped,
tubes 815 and 816 are contained within casing 812 and form a sandwich about
central tube
814. Each of tubes 815 and 816 has a tube wall that has an outer arcuate
portion 817 of a
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circular arc suitable for engaging the inner surface of casing 812, and an
inner arcuate
portion 818, opposed to outer arcuate portion 817, that has an external
surface formed on an
arc suitable for engaging the outer surface of circular cylindrical tube 814.
Tubes 815 and
816 also have first and second radial portions 819 and 820 that are joined to
portions 817
and 818 to form a hollow, closed, kidney shape as noted, the vertices being
smoothly
radiused. The inner surface of this kidney-shaped wall defines the periphery
of internal
passage 821. Tube 816 is of the same construction as tube 815, the two tubes
meeting at the
planar external faces of portions 819 and 810 that lie on a diametral plane
822 of casing 812.
In this instance, portion 818 is convexly curved relative to passage 821. That
is, the local
radius of curvature extends away from passage 821 to a local focus of the
local radius of
curvature that lies outside passage 821. However, the centroid 823 of the
cross-sectional
area of passage 821 lies within passage 821, rather than falling within the
cross-sectional
area of the internal passage 824 of central tube 814.
1 S The configuration of Figure 20a, in effect, splits the annular space
between central
tube 814 and casing 812 in half across the diameter of casing 812, rather than
by trying to
nest a third pipe concentrically between central tube 814 and casing 812. The
resulting
passages will tend to have a combined area that is greater than can be
achieved with
concentric tubes of the same wall thickness, and will have larger hydraulic
diameters, with a
consequent reduction in resistance to fluid flow.
It is not necessary that tubes 815 and 816 be of equal size. Pipe assembly 825
of
Figure 20b is similar to pipe assembly 810, but rather than have kidney shaped
pipes of
equal size, assembly 825 has first and second pipes 826 and 828 of unequal
size, meeting on
radial interfaces.
Figure 21a shows a cross-section of another, four-tube, modular pipe assembly
830,
having a casing 832, a central tube 834 mounted concentrically within casing
832, and three
equal tubes 836, 837 and 838 clustered about central tube 834 a,nd meeting at
radial planar
interfaces on 120 degree centers. Each of tubes 836, 837 and 838 occupies a
sector that is a
third of the annular space between casing 832 and central tube 834. As noted
above, it is not
necessary that the tubes be of equal sizes. Figure 21b shows a cross-section
of a modular
pipe assembly 840 having a casing 842, a round cylindrical central tube 844,
and three tubes
of different sizes 846, 847, and 848, describing, respectively, 75, 120 and
165 degrees of
arc. In general, the arcuate extent of the tubes may be chosen, with all sizes
different, two
the same, or three the same a.s may be desired or convenient.
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-46-
Figure 22a shows a cross-section of a five-tube modular pipe assembly 850
having a
casing 852, a central tube 854, and four equal sectoral tubes 855, 856, 857
and 858, each
occupying a quarter-sector space. Figure 22b shows a similar four-tube
arrangement but
with a single semi-sectoral tube 860, and a pair of quarter-sectoral tubes 862
and 864.
Figure 22c shows yet another alternative five-tube arrangement, in which each
of sectoral
tubes 865, 866, 867 and 868 occupies a different sized sector, being
respectively 60, 75, 90
and 135 degrees of arc being radial interfaces. In general, all sizes may be
different, or two,
three or four sectors can be the same size as may be desired.
In each of the examples of Figures 20a, 20b, 21a, 21b, and 22a, 22b and 22c,
the
concentric central tube, such as tube 814, is maintained in position relative
to the casing by
the radial wall of the surrounding tubes. That is, the shape of the tubes
occupying the
annular space between the casing and the central tube is such as to act in the
manner of a
spider to maintain the relative position of the central tube to the casing,
although the central
tube and the casing do not contact each other directly. The same is true of
the central
hexagonal tube in the bundle of hexagonal tubes shown in Figure 17b.
Figure 23a shows a modular pipe assembly 870 having an external casing 872
that is
a seamless steel tube of known pressure rating. A roll-formed seamless steel
tube 874, also
of known pressure rating, is formed into a D-shape, or hollow semi-circular
form. The outer
wall surface of arcuate portion 876 of tube 874 is of a radius to mate with
the inner surface
of casing 872. When located as shown in Figure 23a, a first passageway 878 is
defined
within the inner wall surface of tube 874, and a second passageway 880 is
defined between
the outer surface of straight portion 882 of tube 874 and the remaining half
884 of the inner
surface of casing 872 that is not engaged by portion 876 of tube 874. The
result is a two-
tube configuration generally similar to that shown in Figure 15b and described
above. Tube
874 can be held in its nested position within casing 872 by a bonding agent,
or by welding,
or by other mechanical means that does not impair the integrity of the
passageways.
Figure 23b shows a modular pipe assembly 890 that is similar to assembly 870,
but
has two nested roll formed tubes 892 and 894, each occupying a sector roughly
equal to 1/3
of the space within pressure rated casing tube 895, such that three side-by-
side passages 896,
897 and 898 are formed. This yields a three passageway result similar to the
tube bundle
configuration of Figure 16a. Figure 23c shows a modular pipe assembly 900 that
is again
similar to assemblies 870 and 890, but in this case has three internal roll-
formed tubes 902,
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903 and 904 each occupying about a quarter sector of the space defined within
outer
pressure rated tube 905. This yields a side-by-side four passageway result
similar to that of
Figure 15a. Sectoral tubes such as 892 and 894, or 902, 903 and 904 can be
used singly or
in equal or unequal combinations as may be suitable for a given application.
Figures 23d and Z3e represent further alternatives to the assemblies of
Figures 23a,
23b and 23c. In Figure 23d, an outer pressure rated tube 910 has a pair of
round circular
tubes 912 and 913 nested side-by-side eccentrically within tube 910. This
yields a pair of
relatively small, round cylindrical passages 914 and 915 within tubes 912 and
913, and a
larger, irregularly shaped passage 918, in the remaining space within the
inner wall of tube
910. Tubes 912 and 913 can be bonded or welded in place, or can be held in
place by other
mechanical means, such as a bracket or spider, that does not impair the
integrity of the
passageways. Figure 23e uses an outer pressure rated tube 920, a kidney shaped
tube 922
nested within outer tube 920, and a central tube 924 nested against tube 922,
concentric with
outer tube 920, yielding a result generally similar to that of Figure 20a.
An advantage of the alternative embodiments of Figures 23a - 23e, is that by
omitting one of the internal tubes of the analogous cross-sections of Figures
15a, 16a, 15b,
19c, or 20a (or of others of the above described cross-sections as may be
suitable) the cross-
sectional area otherwise occupied by the wall thickness of the omitted tube is
made available
for carrying fluids or other services. For a given volumetric flowrate, mean
velocity is
determined by the available cross-sectional area. Losses vary as the square of
the mean
velocity of the fluid, and hydraulic diameter also improves. For example, a 6
inch outer pipe
with a 0.25 inch wall thickness, and an inner tube of 0.217 inch wall
thickness, the potential
increase in area for a semi-circular tube is significant. In each case,
notwithstanding that one
or several pipes are nested within another, the relationships of the
passageways remains a
side-by-side relationship, rather than a concentric relationship.
Figure 24a shows a modular pipe assembly 930 having an outer conduit in the
nature
of a seamless steel tube 932 of known pressure rating. As in the alternative
embodiment of
Figure 23a, a second conduit member in the nature of a roll formed seamless
steel tube 934
formed in the shape of a semi-circle is located within the hollow interior
region defined by
the inside surface of tube 932, the outer surface of the arcuate portion of
tube 934 being
formed to engage a portion of the inner surface of the continuous peripheral
wall of tube
3 S 932. In addition, a third conduit member, in the nature of a seamless
steel tube 936, roll
formed into a shape of a quarter pie piece, more or less, is located within
tube 934. Tube
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936 has an arcuate outer surface shaped to engage a portion, roughly half, of
the inside face
of the arcuate portion of the peripheral wall of tube 934. and a flat portion
whose outside
surface lies against a portion of the inside face of the flat portion of tube
934. As shown, this
configuration of tubes defines three parallel side-by-side passages, 937, 938
and 939.
Passage 937 is defined, or bounded, by half of the inside arcuate face of
outer tube 932 and
the outer face of the back, or straight portion of tube 934. Passage 938 is
defined, or
bounded, by half of the inner surface of the straight portion of tube 934,
half of the arcuate
inner surface of tube 934, and the outer surface of the radial leg portion of
the wall of tube
936 that extends at right angles to the diametral flat portion of tube 934.
Passage 939 is
defined, or bounded, by the interior face of the peripheral wall of tube 936.
The alternative embodiment of Figure 24b is similar to that of Figure 24a in
having a
D-shaped tube 942 located within a circular tube 940, but differs to the
extent that rather
than having a third tube nested within tube 940, third and fourth tubes 944
and 946 are
located in side-by-side arrangement within the D-shaped cavity of tube 940. As
shown,
tubes 944 and 946 are unequal. In the general case of either the embodiment of
Figure 24a
or Figure 24b, the pipes need not be equal in size, need not have right angled
corners, and
need not have straight sides lying on diametral chords of outer tube 942, but
may have
proportions suited for the flows to be carried, may lie on sectors of non-
square angles, and
may have side portions that lie on chords offset from the diameter of the
respective tubes.
Figure 25 shows eight variations of cross-sections of extruded tube that could
be
used as an alternative to the mufti-tube assemblies described above, the
sections having a
suitable pressure rating. The proportions of the pipe walls and webs are not
drawn to scale.
In principle it is possible to extrude tubes corresponding to any of the
sections described
above. Member 950 corresponds to assembly 690. Member 951 corresponds to
assembly
520. Member 522 corresponds to assembly 750. Member 953 corresponds to
assembly 770,
and is intended to represent the general case of any four passage duct. Member
954
corresponds to assembly 810. Member 955 corresponds to assembly 830. Member
956
corresponds to assembly 850, and member 957 corresponds to the assembly of
Figure 22b,
or more generally, a four passage duct that includes a central tube.
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.
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