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.
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.
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. In deviated wellbores, for example, sucker rod pumps tend to experience premature failure due to rod-on-tubing wear. There is, therefore, a need for an improved submersible pumping system that is well-suited for use in marginal or deviated wells.
The present invention includes a submersible pumping system that has an electric motor, a rotary hydraulic pump driven by the electric motor, and a linear hydraulic pump that is configured to move a production fluid. The rotary hydraulic pump produces a pressurized working fluid that drives the linear hydraulic pump.
In another aspect, a submersible pumping system disposed in a wellbore that includes an electric motor filled with a motor lubricant fluid, a hydraulic pump driven by the electric motor that increases the pressure of the motor lubricant fluid, and a production pump configured to produce a production fluid from the wellbore. The production pump is driven by the pressurized motor lubricant fluid.
In yet another aspect, a method for controlling the temperature of an electric motor within a submersible pumping system disposed in a wellbore begins with the step of providing an electric motor that is filled with motor lubricant fluid at a first temperature. Next, the electric motor is activated to drive a hydraulic pump. The method continues with the step of pumping the motor lubricant fluid with the hydraulic pump from the electric motor to a production pump. The production pump is driven by the motor lubricant fluid to evacuate a production fluid from the wellbore. The method concludes with the step of providing the return of the motor lubricant fluid from the production pump to the electric motor at second temperature that is lower than the first temperature.
In accordance with an embodiment of the present invention,
The pumping system 100 includes a hydraulic pump 106, a motor 108 and a production pump 110. 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 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.
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 surface. 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.
The motor 108 is an electric submersible motor that receives power from a surface-based facility through a power cable 112. When electric power is supplied to the motor 108, the motor converts the electric power into rotational motion that is transferred along a shaft (not shown in
The pumping system 100 optionally includes a seal section 116 positioned above the motor 108 and below the hydraulic pump 106. The seal section 116 shields the motor 108 from mechanical thrust produced by the hydraulic pump 106 and isolates the motor 108 from the wellbore fluids in the hydraulic pump 106. The seal section 116 may also be used to accommodate the expansion and contraction of the lubricants within the motor 108 during installation and operation of the pumping system 100. In alternative embodiments, the seal section 116 is incorporated within the motor 108 or within the hydraulic pump 106. Magnetic couplings may also be used to transfer torque between the motor 108, seal section 116 and hydraulic pump 106. The use of magnetic couplings obviates the need for shaft seals within the motor 108, seal section 116 and hydraulic pump 106.
Unlike prior art electric submersible pumping systems, the pumping system 100 moves fluids from the wellbore 104 to the surface using the production pump 110, which is powered by a working fluid that is pressurized by the hydraulic pump 106, which in turn is driven by the motor 108. Thus, the hydraulic pump 106 acts as a hydraulic generator and the production pump 110 acts as a production pump to evacuate fluids from the wellbore 104. High pressure working fluid line 118a is used to transfer working fluid between the hydraulic pump 106 and the production pump 110. High pressure working fluid line 118b is used to transfer working fluid from the production pump 110 back to the motor 108. The working fluid lines 118a, 118b may be internal to the components of the pumping system 100 or external (as depicted in
The use of the hydraulic pump 106 to drive the production pump 110 presents several advantages over the prior art. In particular, the hydraulic pump 106 and motor 108 can be positioned in one portion of the wellbore 104, while the production pump 110 is located at a remote location. In some applications, it may be desirable to place the motor 108 and hydraulic pump 106 above the production pump 110, with the working fluid lines 118 extending through the wellbore between the hydraulic pump 106 and the production pump 110. The ability to divide the pumping system 100 into smaller distinct components connected by flexible lines permits the deployment of the pumping system 100 into highly deviated wellbores 104.
In the embodiment depicted in
The hydraulic pump 106 further includes an intake 124, a discharge 126 and a housing 128. Each of the internal components within the hydraulic pump 106 is contained within the housing 128. The intake 124 is connected directly or indirectly to the motor 108 and the working fluid is the motor lubricant fluid. The use of the motor lubricant fluid as the working fluid has the benefit of cooling the motor lubricant fluid as it travels away from the motor 108 in a circuit through the hydraulic pump 106 and production pump 110. Alternatively, the intake 124 is connected to a working fluid reservoir (not shown in
Generally, fluid enters the hydraulic pump 106 through the intake 124 and is carried by the upstream and downstream chambers 120a, 120b to the working fluid line 118a through the discharge 126. The pump shaft 122 is connected to the output shaft from the motor 108 (not shown) either directly or through a series of interconnected shafts. The hydraulic pump 106 may include one or more shaft seals that seal the shaft 122 as it passes through the upstream and downstream chambers 120a, 120b.
Each of the upstream and downstream chambers 120a, 120b includes a cylinder block 130, one or more piston assemblies 132 and a tilt disc assembly 134. The tilt disc assembly 134 includes a drive plate 136 and a rocker plate 138.
Referring back to
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 hydraulic pump 106 includes a bearing between the rocker plate 138 and the drive plate 136 to reduce friction between the two components.
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 causes 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.
Referring now to
The piston assemblies 132 include a piston rod 152 and a plunger 154. In the embodiment depicted in
In the embodiment depicted in
In the embodiment depicted in
During operation, the motor 108 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.
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 108 and pump shaft 122.
Turning to
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 108 such that operation of the motor 108 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.
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
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.
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.
Alternatively, the pistons 160 can be configured to extend into the manifold 164. In yet another alternate 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 hydraulic pump 106. Other forms of positive displacement pumps may be used as the hydraulic pump 106, including rotary positive displacement pumps that include rotating and variable chambers.
Turning to
The master piston 178 reciprocates in a master cylinder 192 that is in fluid communication with the working fluid inlet 184 and working fluid return 186. The master piston 178 includes lower standoffs 194, upper standoffs 196, a pushrod 198 connected to the slave piston 180 and a pull rod 200. The production pump 110 also includes a lower valve plate 202 and an upper valve plate 204. The pull rod 200 is configured to lift the lower valve plate 202 during upward movement of the master cylinder 192. A valve control ring 206 attached to the pushrod 198 is configured to lower the upper valve plate 204 during downward movement of the master cylinder 192.
Fluid is alternately admitted to the master cylinder 192 through a lower injection port 206 and an upper injection port 208 that are both in fluid communication with the working fluid inlet 184. Fluid is alternately evacuated from the master cylinder 192 through upper vent 212 and lower vent 210. The admittance and evacuation of working fluid is controlled by the position of the lower valve plate 202 and upper valve plate 204. In the first position shown in
As pressure builds in the master cylinder 192 below the master piston 178, the master piston 178 rises. When the master piston 178 nears the completion of its upward stroke, the pull rod 200 catches the lower valve plate 202 and raises the lower valve plate to a second position in which the lower injection port 206 is blocked and the lower vent 210 is opened, as depicted in
As the master piston 178 reciprocates, the slave piston 180 likewise reciprocates within a slave cylinder 218. The slave cylinder 218 is in fluid communication with the production fluid intakes 188. When the slave piston 180 is retracted (as shown in
In this way, the production pump 110 depicted in
In yet another aspect, some embodiments include a method 224 for controlling the temperature of the electric motor 108. Turning to
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 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.
This application is a divisional application of U.S. patent application Ser. No. 14/982,936 filed Dec. 29, 2015 entitled “Linear Hydraulic Pump for Submersible Applications,” the disclosure of which is herein incorporated by reference.
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Number | Date | Country | |
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Parent | 14982936 | Dec 2015 | US |
Child | 16458027 | US |