Patent Application
20140105759
Not Applicable.
Not Applicable.
This invention relates to linear pump and motor systems. More particularly, to a linear pump and motor systems that provides improved operation and reliability. Additionally, the invention relates to a pressure compensation device and a gas mitigation assembly.
Several varieties of pumps are utilized to pump fluids, such as oil, water, and other fluids. For example, rod pumps, electrical submersible pumps (ESPs), and the like are utilized to pump fluids from wells or the like. Rod pumps may be operated by a pumping unit that is above ground that pivotally oscillates to provide pumping action. A rod oscillates up and down, and may cause ball check valves (e.g. a traveling and standing valve) to open and close during pumping. Rod pumps systems may encounter issues, such as rod stretch, gas lock, or the like. ESPs are centrifugal pumps that may be place into a well to pump fluids. Some ESPs may require a minimum flow rate or speed at which the pump must operated at to prevent overheating of the motor.
A pressure compensation device may minimize or eliminate a pressure differential between two fluids. A gas mitigation assembly may prevent the build up of gas. A linear pump and motor system may provide improved operation and reliability.
In one embodiment, a pressure compensation device (PCD) may provide a tubular and a piston positioned within the tubular. The piston may move within the tubular in response to a pressure differential between a first and second fluid. The first fluid may fill the tubular above the piston, and the second fluid may fill the tubular below the piston. In some embodiments, the PCD may be utilized with the linear pump discussed herein. In other embodiments, the PCD may be utilized in a pump, motor or the like. In yet another embodiments, the PCD may be utilized in any other suitable application.
In another implementation, gas mitigation assembly is integrated with a traveling valve. The traveling valve may be positioned below the standing valve. During the upstroke, traveling valve may mechanically open the standing valve to allow trapped gas to be released. In some embodiments, the gas mitigation assembly may be utilized in a pump, motor or the like. In yet another embodiments, the gas mitigation assembly may be utilized in any other suitable application.
In yet another embodiment, a linear pump and motor system includes a motor, rotary-to-linear mechanism, PCD, and gas mitigation assembly. The rotary-to-linear mechanism may translate rotation of a motor into linear motion to provide a reciprocating pumping action. A PCD may minimize a pressure differential between lubrication fluids and external fluids. A gas mitigation assembly may provide a mechanism that mechanically opens a valve.
The foregoing has outlined rather broadly various features of the present disclosure in order that the detailed description that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter.
For a more complete understanding of the present disclosure, and the advantages thereof, reference is now made to the following descriptions to be taken in conjunction with the accompanying drawings describing specific embodiments of the disclosure, wherein:
Refer now to the drawings wherein depicted elements are not necessarily shown to scale and wherein like or similar elements are designated by the same reference numeral through the several views.
Referring to the drawings in general, it will be understood that the illustrations are for the purpose of describing particular implementations of the disclosure and are not intended to be limiting thereto. While most of the terms used herein will be recognizable to those of ordinary skill in the art, it should be understood that when not explicitly defined, terms should be interpreted as adopting a meaning presently accepted by those of ordinary skill in the art.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention, as claimed. In this application, the use of the singular includes the plural, the word “a” or “an” means “at least one”, and the use of “or” means “and/or”, unless specifically stated otherwise. Furthermore, the use of the term “including”, as well as other forms, such as “includes” and “included”, is not limiting. Also, terms such as “element” or “component” encompass both elements or components comprising one unit and elements or components that comprise more than one unit unless specifically stated otherwise.
When the ball screw 218 is rotated in a first direction, the thread coupling causes ball nut 220 to moves linearly in a first direction. When the ball screw 218 is rotated in an opposite direction, the thread coupling causes ball nut 220 to move in an opposite direction. For example, rotation of the ball screw 218 clockwise may cause the ball nut 220 to move down towards the motor 205, and rotation of the ball screw 218 counterclockwise may cause the ball nut 220 to move away from the motor 205. During operation of the linear pump 100, the motor 205 is repeatedly rotated back and forth in a clockwise and counterclockwise direction, thereby causing the ball nut 220 to move up and down along a linear path. The reciprocating movement of the ball nut 220 is utilized to provide the pumping action for the linear pump. The stroke length of the linear pump can be precisely control. Further, the stroke length is defined and repeatable, whereas other systems such as rod pumps may experience rod or tubing stretch with each stroke making the stroke length unpredictable. The ball nut 220 may be coupled to a ball screw encapsulator 228. For example, a coupling nut 222 may be provided that allows the ball nut 220 to be coupled to the ball screw encapsulator 228 using threads or the like.
Ball screw encapsulator 228 may be sealed on it outer diameter by a seal coupling 225. For example, seal coupling 225 may provide one or more seals on its inner diameter. A first end of the seal coupling 225 may be coupled to the ball screw guide 215, and a second end of the seal coupling may be coupled a tubular 235, such as a perforated sub. A coupling 230 may connect ball screw encapsulator 228 to a PCD tubular housing 238, which causes the PCD tubular housing 238 to move when the ball nut 220 is moved. As the ball nut 220 moves linearly, the ball screw encapsulator 228 and the PCD tubular housing 238 move within the ball screw guide 215 and tubular 235. While the perforated sub allows formation fluids to enter, the outside diameter of ball screw encapsulator 228 is in contact with the seals retained within seal couplings 225, which prevents oil for the ball screw assembly and motor 205 from mixing with the formation fluids entering the perforated sub.
Further, the pressure compensation device (PCD) provides a PCD tubular housing 238 and a shuttle piston 232 that also prevents lubricating oil for the ball screw assembly and motor 205 from mixing with formation fluids.
The tubular 235 may be perforated to allow formation fluids to enter into the pump 100. The tubular 238 of the PCD device may be coupled to an intake coupling nut 242, and the intake coupling nut 242 is also coupled to a pump plunger 245.
As the ball nut 220 is moved by the motor 205, pump plunger 245 moves up and down within the pump barrel 248 to pump formation fluids. As discuss previously, unlike rod pumps that experience rod or tubing stretch during each pump stroke, the linear pump provides for repeatable and precise control of a stroke length and position. In some embodiments, the linear pump discussed herein allows the stroke length and position to be precisely controlled within 49 mm or less. In some embodiments, the linear pump discussed herein allows the stroke length and position to be precisely controlled within 40 mm or less. In some embodiments, the linear pump discussed herein allows the stroke length and position to be precisely controlled within 30 mm or less. In some embodiments, the linear pump discussed herein allows the stroke length and position to be precisely controlled within 20 mm or less. In some embodiments, the linear pump discussed herein allows the stroke length and position to be precisely controlled within 10 mm or less. In some embodiments, the linear pump discussed herein allows the stroke length and position to be precisely controlled within 12.7 mm or less. Further, the ability to accurately control the stroke length and position does not degrade over time. This precise and repeatable control allows the position of the pump plunger 245 relative to the pump barrel 248 to be easily determined at all times. A top portion of the pump plunger 245 is coupled to a traveling valve assembly 255.
As an illustration, an example describing operation of the traveling valve assembly 255 is provided. When the pump plunger 245 and traveling valve assembly 255 are retracted towards the motor and away from a standing valve assembly 258 (downstroke), the inner diameter of the pump plunger 245 may be filled with formation fluids entering through intake coupling nut 242. Further, during the downstroke, ball 360 may be moved to allow fluids to flow out of pump plunger 245 through the traveling valve assembly 255. As shown in
Next, the pump plunger 245 and traveling valve assembly 255 are extended away from the motor 205 or back towards the standing valve (upstroke). During the upstroke, ball 360 of the traveling valve assembly 255 may become seated on seat 355 to prevent the flow of formation fluids into the pump plunger 245. As a result, fluid pressure of formation fluids between the traveling valve assembly 255 and standing valve assembly 258 may increase since the fluid is being compressed by pump plunger 245.
The traveling valve assembly 255 and standing valve assembly 258 may also provide gas mitigation features. During pumping, gas may be released from formation fluids or enter into the pump. The gas may enter the pump barrel 248 between the standing 258 and traveling valve 255 assembly. As gases can be compressed more than liquids, the presence of gas may cause gas lock. For example, if enough gas is present between the traveling valve assembly 255 and standing valve assembly 258, the pressure exerted by gas compressed on the upstroke may not be sufficient to move ball 390 in the standing valve assembly 258. In order to prevent gas lock, the cage 365 of the traveling valve assembly 255 may provide a probe 375. As shown in
It will be recognized that several components of the linear pump 100 may be adapted for other applications. The following provides a discussion of non-limiting examples of alternative uses for certain components of the linear pump 100.
Pressure Compensation Device (PCD)
While the Pressure Compensation Device (PCD) is utilized in the linear pump discussed above, it will be recognized by one of ordinary skill in the art that the PCD may be suitable for use in several other applications. The PCD may be utilized in any device in which it is desirable to balance pressures between two fluids that are undesirable to mix.
Tubular housing 420 may be position in a well, borehole, casing, formation or the like. For purposes of illustration, tubular housing 420 is shown in a casing 460 for a well. A third region 470 between the casing 460 and tubular housing 420 may be filled with the same fluid that is provided in the first region 440 (embodiment shown) or the same fluid that is provided in the second region 450 (reversed embodiment—not shown). For purposes of illustration, the first fluid is also provided in the third region 470, and the first region 440 may be in fluid communication with the third region 470. As a result, the fluid pressure outside of tubular housing 420 in the third region may be approximately the same as the fluid pressure in the first region above the tubular. It will be recognized that in the reversed embodiment, second region 450 may be in fluid communication with the third region 470.
The bottom of tubular housing 420 may be coupled to a motor, pump, or the like. The second fluid in the second region 450 may be isolated to prevent mixing with other fluids. For example, the second fluid may be a lubricating fluid for the motor, pump, or the like. Seals, threaded connections, or the like may be provided to isolate the second fluid from other fluids, such as the first fluid. However, the second fluid may become pressurized or de-pressurized during operation of the motor, pump, or the like due to displacement of second fluid, thermal expansion/shrinking, or the like. As a result, without pressure compensation, the second fluid may be forced out through connections, seals, or the like when pressure is high or external fluid may be sucked in through connections, seals, or the like when the pressure is low. The loss of the lubricating fluid or mixing of lubrication fluid and external fluids may cause damage to or reduce performance of the motor, pump, or the like.
In order to prevent such issues, a pressure compensation device may be provided to minimize or eliminate the pressure differential between the two fluids. As shown in
Gas Mitigation
Prior systems provided the traveling valve above the standing valve. As such, the downward movement of the traveling valve in such system make it difficult to use the traveling valve to open or unseat the ball of the standing valve. In other words, the downward motion of the traveling valve would allow the standing valve ball to move into seat of the standing valve.
In contrast, the standing valve 520 is provided above the traveling valve 510. The standing valve 520 remains stationary, whereas the traveling valve 510 may extend and retract within the pump barrel. Since the traveling valve 510 moves linearly in relation to the standing valve 520, the traveling valve 510 may be coupled to a linear mechanism 560. For example, in the exemplary embodiment discussed previously, the traveling valve 510 was coupled to a ball screw/nut assembly. However, in other embodiments, traveling valve 510 may be coupled to a rod pump, rod screw assembly, or any other suitable linear mechanism utilized in pumps or motors. During pumping or the like, gas may be present between the standing 520 and traveling valve 510 that may cause gas lock. As a result of the linear motion provided by linear mechanism 560, probe 530 of the traveling valve 510 may mechanically open the standing valve 520.
Advantages
The linear pump and components discussed above provide several advantages over existing systems. Some ESP motors require significant amounts of production fluids to pass around the ESP motor to prevent overheating. As a result, low production wells are not suitable for continuous operation of ESP motors at low speeds. For example, some ESP motors are not suitable for operation at speeds below 60 Hz, 3600 rpm, or production rates of 300 barrels per day or less. To prevent overheating of ESPs in low production wells, the ESPs may be cycled on and off at normal speeds (e.g. 60 Hz) or greater to prevent overheating. In some embodiments, the linear pump discussed herein may operate in low production wells that provide 400 barrels per day or less. In some embodiments, the linear pump discussed herein may operate in low production wells that provide 300 barrels per day or less. In some embodiments, the linear pump discussed herein may operate in low production wells that provide 250 barrels per day or less. In some embodiments, the linear pump discussed herein may operate in low production wells that provide 200 barrels per day or less. In some embodiments, the linear pump discussed herein may operate in low production wells that provide 150 barrels per day or less. In some embodiments, the linear pump may operate in low production wells that provide 100 barrels per day or less. The linear pump is capable of operating in low production wells because it does not require a certain amount of production fluids to pass by the motor. In some embodiments, the linear pump may operate at 3000 rpm or less. In some embodiments, the linear pump may operate at 2500 rpm or less. In some embodiments, the linear pump may operate at 2000 rpm or less. In some embodiments, the linear pump may operate at 1500 rpm or less. Lubricating oil utilized by the motor is sealed off from production fluids and provides sufficient cooling and lubrication to prevent overheating. Rod Lift systems require significant horsepower to lift a rod string, have frictional losses between the sucker rod and tubing, and may have rod or tubing stretch with each stroke. The linear pump discussed provides several advantages over the alternatives, such as allowing the use of a more efficient, lower power motor, reducing frictional losses due to elimination of the rod string, etc. Further, the linear pump discussed has a defined and repeatable stroke. In other words, a length that the ball nut can travel up or down along the ball screw will not change over time. Additionally, the PCD and gas mitigation assembly utilized by the linear pump may provide several other advantages as discussed herein. In the case that a permanent magnet motor is utilized, precise control and determination of position can be determined without the use of sensors disposed within the linear pump.
Further, in motors or pumps with lubricating oil provided in a sealed off chamber, pressure compensation may be important. If the motor or pump causes changes in pressure to the lubricating oil, it may cause lubricating oil to be forced out or may cause external fluids to be sucked in. The PCD discussed previously prevents or minimizes a pressure differential between lubricating oil and external fluids.
In traditional rod lift system or other reciprocating pump systems, the traveling valve is above the standing valve. As a result the traveling valve is traveling in the wrong direction to unseat the standing valve. In contrast, the traveling valve and standing valve arrangement discussed allows the standing valve to be easily and mechanically opened allowing gas to be produced.
In some embodiments, the linear pump is simplified to require no positioning sensors. The linear pump may rely on time and amp/power readings to determine position. This reduces the number of wires required going to the pump, which reduces complexity and cost. Surface controls may receive motor performance data. The data may be utilized to derive information about the well conditions, mechanical condition of the pump, formation fluid level, or the like.
Implementations described herein are included to demonstrate particular aspects of the present disclosure. It should be appreciated by those of skill in the art that the implementations described herein merely represent exemplary implementation of the disclosure. Those of ordinary skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific implementations described and still obtain a like or similar result without departing from the spirit and scope of the present disclosure. From the foregoing description, one of ordinary skill in the art can easily ascertain the essential characteristics of this disclosure, and without departing from the spirit and scope thereof, can make various changes and modifications to adapt the disclosure to various usages and conditions. The implementations described hereinabove are meant to be illustrative only and should not be taken as limiting of the scope of the disclosure.
This application claims the benefit of U.S. Provisional Patent Application No. 61/708,761 to Henry et al., filed on Oct. 2, 2012, which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61708761 | Oct 2012 | US |
