Note: Descriptions are shown in the official language in which they were submitted.
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ROTARY HYDRAULIC PUMP WITH ESP MOTOR
Field of the Invention
[001] This invention relates generally to the field of submersible pumping
systems,
and more particularly, but not by way of limitation, to a rotary hydraulic
pump driven
by a submersible electric motor.
Background
[002] Submersible pumping systems are often deployed into wells to recover
petroleum fluids from subterranean reservoirs. Typically, a submersible
pumping
system includes a number of components, including an electric motor coupled to
one
or more centrifugal pump assemblies. Production tubing is connected to the
pump
assemblies to deliver the petroleum fluids from the subterranean reservoir to
a storage
facility on the surface. The pump assemblies often employ axially and
centrifugally
oriented multistage turbomachines.
[003] In certain applications, however, the volume of fluid available to be
produced
from the well is insufficient to support the costs associated with
conventional electric
submersible pumping systems. In the past, alternative lift systems have been
used to
encourage production from "marginal" wells. Surface-based sucker rod pumps and
gas-driven plunger lift systems have been used in low volume wells. Although
widely
adopted, these solutions may be unacceptable or undesirable for a number of
reasons.
There is, therefore, a need for an improved submersible pumping system that is
well-
suited for use in marginal wells.
Summary of the Invention
[004] In some embodiments, the present invention includes a submersible
pumping
system that has an electric motor and a pump driven by the electric motor. The
pump
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includes a rotatable shaft driven by the motor, one or more piston assemblies
configured for linear reciprocating motion and means for converting the
rotational
movement of the shaft to linear reciprocating movement in the piston
assemblies.
[005] In another aspect, embodiments of the invention include a pump useable
within submersible pumping system. The pump includes a cylinder block that
includes a plurality of cylinders, a rotatable shaft, a tilt disc assembly and
a plurality
of piston assemblies. The tilt disc assembly includes a drive plate connected
to the
rotatable shaft and configured for rotation with the shaft and a rocker plate
that is not
configured for rotation with the shaft. Each of the plurality of piston
assemblies
includes a plunger that is configured for reciprocating linear motion in a
corresponding one of the plurality of cylinders and a piston rod connected to
the
plunger and to the rocker plate.
[006] In yet another aspect, embodiments of the invention include a pump
useable
within a submersible pumping system. The pump includes a plurality of
manifolds
and one or more banks of cylinders. Each of the banks of cylinders corresponds
to a
separate one of the plurality of manifolds. The pump further includes a
plurality of
cylinders within each of the banks of cylinders and each cylinder is in fluid
communication with the corresponding manifold. The pump also includes a
rotatable
camshaft and a plurality of pistons assemblies. Each piston assembly includes
a
piston and a connecting rod that connects the piston to the camshaft.
Brief Description of the Drawings
[007] FIG. 1 depicts a submersible pumping system constructed in accordance
with
an embodiment of the present invention.
[008] FIG. 2 provides a cross-sectional view of a rotary hydraulic pump of the
pumping system of FIG. 1 constructed in accordance with an embodiment.
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[009] FIG. 3 is a view of the downstream side of the cylinder block of the
rotary
hydraulic pump of FIG. 2.
[010] FIG. 4 is a view of the upstream side of the cylinder block of the
rotary
hydraulic pump of FIG. 2.
10111 FIG. 5 is a view of the downstream side of the tilt plate of the rotary
hydraulic
pump of FIG. 2.
[012] FIG. 6 is a view of the downstream side of the drive of the rotary
hydraulic
pump of FIG. 2.
[013] FIG. 7 provides a cross-sectional view of a rotary hydraulic pump
constructed
in accordance with an alternate embodiment.
[014] FIG. 8 provides a side cross-sectional view of a rotary hydraulic pump
of the
pumping system of FIG. 1 constructed in accordance with an alternate
embodiment.
[015] FIG. 9 provides a top cross-sectional depiction of the rotary hydraulic
pump of
FIG. 8.
Detailed Description
[016] In accordance with exemplary embodiments of the present invention, FIG.
1
shows an elevational view of a pumping system 100 attached to production
tubing
102. The pumping system 100 and production tubing 102 are disposed in a
wellbore
104, which is drilled for the production of a fluid such as water or
petroleum. As used
herein, the term "petroleum" refers broadly to all mineral hydrocarbons, such
as crude
oil, gas and combinations of oil and gas. The production tubing 102 connects
the
pumping system 100 to a wellhead 106 located on the surface.
[017] The pumping system 100 includes a pump 108, a motor 110, and a seal
section
112. Although the pumping system 100 is primarily designed to pump petroleum
products, it will be understood that the present invention can also be used to
move
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other fluids. It will also be understood that, although each of the components
of the
pumping system are primarily disclosed in a submersible application, some or
all of
these components can also be used in surface pumping operations.
[018] As used in this disclosure, the terms "upstream" and "downstream" will
be
understood to refer to the relative positions within the pumping system 100 as
defined
by the movement of fluid through the pumping system 100 from the wellbore 104
to
the wellhead 106. The term "longitudinal" will be understood to mean along the
central axis running through the pumping system 100; the term "radial" will be
understood to mean in directions perpendicular to the longitudinal axis; and
the term
"rotational" will refer to the position or movement of components rotating
about the
longitudinal axis.
[019] The motor 110 is an electric submersible motor that receives power from
a
surface-based facility through power cable 114. When electric power is
supplied to
the motor 110, the motor converts the electric power into rotational motion
that is
transferred along a shaft (not shown in FIG. 1) to the pump 108. In some
embodiments, the motor 110 is a three-phase motor that is controlled by a
variable
speed drive 116 located on the surface. The variable speed drive 116 can
selectively
control the speed, torque and other operating characteristics of the motor
110.
[020] The seal section 112 is positioned above the motor 110 and below the
pump
108. The seal section 112 shields the motor 110 from mechanical thrust
produced by
the pump 108 and isolates the motor 110 from the wellbore fluids in the pump
108.
The seal section 112 may also be used to accommodate the expansion and
contraction
of lubricants within the motor 110 during installation and operation of the
pumping
system 100. In some embodiments, the seal section 112 is incorporated within
the
motor 110 or within the pump 108.
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[021] Unlike prior art electric submersible pumping systems, the pump 108 is a
rotary hydraulic pump that is driven by the motor 110. The pump 108 translates
rotational motion produced by the motor 110 into linearly motion that drives
reciprocating pistons within the pump 108. Although a single pump 108 is
depicted
in FIG. 1, it will be appreciated that the pump 108 can be used in combination
with
additional pumps and motors. For example, the pump 108 can be used with other
hydraulic rotary pumps, to feed a surface-based sucker rod pump or to feed a
centrifugal pump.
[022] In the embodiment depicted in FIG. 2, the pump 108 utilizes a tilt-plate
to
translate the rotational movement of motor 110 into reciprocating linear
motion. In
the cross-sectional depiction of the pump 108 in FIG. 2, the pump 108 includes
an
upstream chamber 118, a downstream chamber 120 and a pump shaft 122. It will
be
appreciated, however, that the scope of exemplary embodiments is not limited
to two-
chamber designs. The pump 108 could alternatively include a single chamber or
more
than two chambers.
[023] The pump 108 further includes an intake 124, a discharge 126 and a
housing
128. Each of the internal components within the pump 108 is contained within
the
housing 128. Fluid from the wellbore 104 enters the pump 108 through the
intake 124
and is carried by the upstream and downstream chambers 118, 120 to the
production
tubing 102 through the discharge 126. The pump shaft 122 is connected to the
output
shaft from the motor 110 (not shown) either directly or through a series of
interconnected shafts. The pump 108 may include one or more shaft seals that
seal
the shaft 122 as it passes through the upstream and downstream chambers 118,
120.
[024] Each of the upstream and downstream chambers 118, 120 includes a
cylinder
block 130, one or more piston assemblies 132 and a tilt disc assembly 134. The
tilt
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disc assembly 134 includes a drive plate 136 and a rocker plate 138. FIGS. 5
and 6
illustrate the upstream face of the rocker plate 138 and the upstream face of
the drive
plate 136. The rocker plate 138 and the drive plate 136 may both be formed as
substantially cylindrical members.
[025] Referring back to FIG. 2, the drive plate 136 is connected to the pump
shaft
122 in a non-perpendicular orientation. In this way, rotation of the pump
shaft 122
causes an upstream and a downstream edge of the drive plate 136 to rotate
around the
shaft 122 within the upstream and downstream chambers 118, 120 at opposite
times.
In some embodiments, the drive plate 136 is connected to the pump shaft 122 at
a
fixed angle. In other embodiments, the angular disposition of the connection
between
the drive plate 136 and the pump shaft 122 can be adjusted during use.
[026] The rocker plate 138 is not configured for rotation with the pump shaft
122
and remains rotationally fixed with respect to the cylinder block 130 and
housing 128.
In some embodiments, the upstream face of the rocker plate 138 is in sliding
contact
with the downstream face of the drive plate 136. In other embodiments, the
pump
108 includes a bearing between the rocker plate 138 and the drive plate 136 to
reduce
friction between the two components.
[027] The rocker plate 138 includes a central bearing 140 and piston rod
recesses
142. The central bearing 140 permits the rocker plate 138 to tilt in response
to the
rotation of the adjacent drive plate 136. Thus, as the drive plate 136 rotates
with the
pump shaft 122, the varying rotational position of the downstream edge of the
drive
plate 136 cause the rocker plate 138 to tilt in a rolling fashion while
remaining
radially aligned with the cylinder block 130 and housing 128. The central
bearing
140 may include ball bearings, lip seals or other bearings that allow the
rocker plate
138 to tilt in a longitudinal manner while remaining rotationally fixed.
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[028] Referring now to FIGS. 2, 3 and 4, the cylinder block 130 is fixed
within the
housing 128. The cylinder block 130 includes a plurality of cylinders 144,
intake
ports 146 and one-way valves 148. In the exemplary embodiment depicted in
FIGS. 3
and 4, the cylinder block 130 includes six cylinders 144, six intake ports
146, six
intake way valves 148 and six discharge valves 150. It will be understood,
however,
that the cylinder block 130 may include different numbers of cylinders 144,
intake
ports 146 and one-way valves 148.
[029] The piston assemblies 132 include a piston rod 152 and a plunger 154. In
the
embodiment depicted in FIG. 3, the pump 108 includes six piston assemblies
132. It
will be understood, however, that fewer or greater numbers of piston
assemblies 132
may also be used. A proximal end of each the piston rods 152 is secured within
a
corresponding one of the piston rod recesses 142 in the rocker plate 138. A
distal end
of each of the piston rods 152 is attached to the plunger 154. Each plunger
154
resides within a corresponding one of the cylinders 144.
[030] In the embodiment depicted in FIG. 3, the intake ports 146 extend to the
upstream side of the cylinder blocks 130. An intake valve 148 within the
intake ports
146 allows fluid to enter the intake port 146 from the upstream side of the
cylinder
block 130, but prohibits fluid from passing back out of the upstream side of
the
cylinder block 130. A corresponding discharge valve 150 allows fluid to exit
the
cylinder 144, but prohibits fluid from entering the cylinder 144.
[031] In an alternate embodiment depicted in FIG. 7, the intake ports 146
extend
through the downstream side of a single cylinder block 130. An intake valve
148
within the intake ports 146 allows fluid to enter the intake port 146 from the
downstream side of the cylinder block 130, but prohibits fluid from passing
back out
of the intake port 146. A corresponding discharge valve 150 allows fluid to
exit the
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cylinder 144, but prohibits fluid from entering the cylinder 144. In the
embodiment
depicted in FIG. 7, it may be desirable to attach discharge tubes 156 to each
of the
cylinders 144 to prevent fluid from recirculating through the cylinder block
130.
[032] During operation, the motor 110 turns the pump shaft 122, which in turn
rotates the drive plate 136. As the drive plate 136 rotates, it imparts
reciprocating
longitudinal motion to the rocker plate 136. With each complete rotation of
the drive
plate 136, the rocker plate 138 undergoes a full cycle of reciprocating,
linear motion.
The linear, reciprocating motion of the rocker plate 138 is transferred to the
plungers
154 through the piston rods 152. The piston rods 152 force the plungers 154 to
move
back and forth within the cylinders 144.
[033] As the plungers 154 move in the upstream direction, fluid is drawn into
the
cylinders through the intake ports 146 and intake valves 148. As the plungers
154
continue to reciprocate and move in the downstream direction, the intake
valves 148
close and fluid is forced out of the cylinders 144 through the discharge
valves 150. In
this way, the stroke of the piston assemblies 132 is controlled by the
longitudinal
distance between the upstream and downstream edges of the rocker plate 138.
The
rate at which the piston assemblies 132 reciprocate within the cylinder block
130 is
controlled by the rotational speed of the motor 110 and pump shaft 122.
[034] Turning to FIG. 8, shown therein is a cross-sectional depiction of the
pump
108 constructed in accordance with another embodiment. In the embodiment
depicted
in FIG. 8, the pump 108 uses a central camshaft 158 to drive one or more
series of
pistons 160 within banks of cylinders 162. The cylinders 162 are connected to
manifolds 164 that extend the length of the pump 108. In exemplary
embodiments,
the pump 108 includes 2, 4, 6 or 8 banks of cylinders 162, manifolds 164 and
series of
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pistons 160 that are equally distributed around the pump 108, as depicted in
the top
cross-sectional view of FIG. 9.
[035] The camshaft 158 includes a number of radially offset lobes 166 to which
connecting rods 168 are secured for rotation. The camshaft 158 is connected
directly
or indirectly to the output shaft from the motor 110 such that operation of
the motor
110 causes the camshaft 158 to rotate at the desired speed. It will be
appreciated that
the pistons 160, camshaft 158 and connecting rods 168 may include additional
features not shown or described that are known in the art, including for
example, wrist
pins, piston seal rings and piston skirts. Each set of pistons 160 and
connecting rods
168 can be collectively referred to as a "piston assembly" within the
description of
this embodiment.
[036] Each of the manifolds 164 includes an inlet 170 and outlet 172 and one
or
more check valves 174. The inlets 170 are connected to the pump intake 124 and
the
outlets 172 are connected to the discharge 126. In the embodiment depicted in
FIG. 8,
each manifold 164 includes a separate check valve between adjacent pistons
160. The
check valves 174 prevent fluid from moving upstream in a direction from the
outlet
172 to the inlet 170. In this way, the check valves 174 separate the manifolds
164
into separate stages 176 that correlate to each of the pistons 160 and
cylinders 162.
[037] During operation, the camshaft 158 rotates and causes the pistons 160 to
move
in reciprocating linear motion in accordance with well-known mechanics. As a
piston
160 retracts from the manifold 164, a temporary reduction in pressure occurs
within
the portion of the manifold 164 adjacent to the cylinder 162 of the retracting
piston
160. The reduction in pressure creates a suction that draws fluid into the
stage 176
from the adjacent upstream stage 176 through the intervening check valve 174.
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[038] During a compression stroke, the piston 160 moves through the cylinder
162
toward the manifold 164, thereby reducing the volume of the open portion of
the
cylinder 162 and stage 176. As the pressure increases within the stage 176
adjacent
the piston 160 in a compression stroke, fluid is discharged to the adjacent
downstream
stage through the check valve 174. The configuration and timing of the
camshaft 158
can be optimized to produce suction-compression cycles within each stage 176
that
are partially or totally offset between adjacent stages 176 that provide for
the
sequential stepped movement of fluid through the manifolds 164.
[039] In an alternate embodiment, the pistons 160 are configured to extend
into the
manifold 164. In another embodiment, the check valves 174 are omitted and the
progression of fluid through the manifold 164 is made possible by holding the
pistons
160 in a closed position within the manifold 164 to act as a stop against the
reverse
movement of fluid toward the inlet 170. The timing of the pistons 160 can be
controlled using lobed cams and rocker arms as an alternative to the camshaft
158 and
connecting rods 168. In this way, the pistons 160 produce rolling progressive
cavities
within the manifolds 164 that push fluid downstream through the pump 108.
[040] Thus, in each of the embodiments disclosed herein, the pump 108 provides
a
positive displacement, linearly reciprocating pump that is powered by the
rotating
shaft of a conventional electric submersible motor 110. The pump 108 will find
particular utility in lower volume pumping operations and in wellbores 104
that
present fluids with a large gas fraction. Because the pump 108 can be
configured to
be shorter than conventional multistage centrifugal pumps, the pump 108 is
also well-
suited for deployment in deviated (non-vertical) wellbores 104.
[041] It is to be understood that even though numerous characteristics and
advantages of various embodiments of the present invention have been set forth
in the
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foregoing description, together with details of the structure and functions of
various
embodiments of the invention, this disclosure is illustrative only, and
changes may be
made in detail, especially in matters of structure and arrangement of parts
within the
principles of the present invention to the full extent indicated by the broad
general
meaning of the terms in which the appended claims are expressed. It will be
appreciated by those skilled in the art that the teachings of the present
invention can
be applied to other systems without departing from the scope and spirit of the
present
invention.
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