Patent Application
20170184089
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. There is, therefore, a need for an improved submersible pumping system that is well-suited for use in marginal wells.
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 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.
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.
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.
In accordance with exemplary embodiments of the present invention,
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 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 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.
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
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.
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
In the embodiment depicted in
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.
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 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 pump 108 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 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.
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 an alternate embodiment depicted in
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.
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.
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 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.
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.
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.
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.
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.
