EP3170968B1 - Well pumping system and method - Google Patents
Well pumping system and method Download PDFInfo
- Publication number
- EP3170968B1 EP3170968B1 EP16199698.8A EP16199698A EP3170968B1 EP 3170968 B1 EP3170968 B1 EP 3170968B1 EP 16199698 A EP16199698 A EP 16199698A EP 3170968 B1 EP3170968 B1 EP 3170968B1
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- European Patent Office
- Prior art keywords
- actuator
- rod string
- well pumping
- flowmeter
- control system
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Images
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
- F04B49/12—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00 by varying the length of stroke of the working members
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B33/00—Sealing or packing boreholes or wells
- E21B33/02—Surface sealing or packing
- E21B33/03—Well heads; Setting-up thereof
- E21B33/06—Blow-out preventers, i.e. apparatus closing around a drill pipe, e.g. annular blow-out preventers
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/12—Methods or apparatus for controlling the flow of the obtained fluid to or in wells
- E21B43/121—Lifting well fluids
- E21B43/126—Adaptations of down-hole pump systems powered by drives outside the borehole, e.g. by a rotary or oscillating drive
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B19/00—Machines or pumps having pertinent characteristics not provided for in, or of interest apart from, groups F04B1/00 - F04B17/00
- F04B19/20—Other positive-displacement pumps
- F04B19/22—Other positive-displacement pumps of reciprocating-piston type
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B47/00—Pumps or pumping installations specially adapted for raising fluids from great depths, e.g. well pumps
- F04B47/02—Pumps or pumping installations specially adapted for raising fluids from great depths, e.g. well pumps the driving mechanisms being situated at ground level
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
- F04B49/20—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00 by changing the driving speed
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
- F04B49/22—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00 by means of valves
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B9/00—Piston machines or pumps characterised by the driving or driven means to or from their working members
- F04B9/08—Piston machines or pumps characterised by the driving or driven means to or from their working members the means being fluid
- F04B9/10—Piston machines or pumps characterised by the driving or driven means to or from their working members the means being fluid the fluid being liquid
- F04B9/103—Piston machines or pumps characterised by the driving or driven means to or from their working members the means being fluid the fluid being liquid having only one pumping chamber
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B2203/00—Motor parameters
- F04B2203/02—Motor parameters of rotating electric motors
- F04B2203/0209—Rotational speed
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B2203/00—Motor parameters
- F04B2203/09—Motor parameters of linear hydraulic motors
- F04B2203/0903—Position of the driving piston
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B53/00—Component parts, details or accessories not provided for in, or of interest apart from, groups F04B1/00 - F04B23/00 or F04B39/00 - F04B47/00
- F04B53/16—Casings; Cylinders; Cylinder liners or heads; Fluid connections
Definitions
- This disclosure relates generally to equipment utilized and operations performed in conjunction with a subterranean well and, in one example described below, more particularly provides a well pumping system and associated method. Certain embodiments provide operational control of a wellsite pumping unit with displacement determination.
- Reservoir fluids can sometimes flow to the earth's surface when a well has been completed. However, with some wells, reservoir pressure may be insufficient (at the time of well completion or thereafter) to lift the fluids (in particular, liquids) to the surface. In those circumstances, technology known as "artificial lift" can be employed to bring the fluids to or near the surface (such as a subsea production facility or pipeline, a floating rig, etc.).
- a downhole pump is operated by reciprocating a string of "sucker" rods deployed in a well.
- An apparatus (such as, a walking beam-type pump jack or a hydraulic actuator) located at the surface can be used to reciprocate the rod string.
- CA2826593A1 describes an electronic control system that controls movement of the piston as it moves between the upper and lower rod positions.
- US 5996688 proposes a hydraulic pump jack drive system.
- FIG. 1 Representatively illustrated in FIG. 1 is a well pumping system 10 and associated method for use with a subterranean well, which system and method can embody principles of this disclosure.
- the well pumping system 10 and method are merely one example of an application of the principles of this disclosure in practice, and a wide variety of other examples are possible. Therefore, the scope of this disclosure is not limited at all to the details of the system 10 and method as described herein or depicted in the drawings.
- a power source 12 is used to supply energy to an actuator 14 mounted on a wellhead 16.
- the actuator 14 reciprocates a rod string 18 extending into the well, thereby operating a downhole pump 20.
- the rod string 18 may be made up of individual sucker rods connected to each other, although other types of rods or tubes may be used, the rod string 18 may be continuous or segmented, a material of the rod string 18 may comprise steel, composites or other materials, and elements other than rods may be included in the string.
- the scope of this disclosure is not limited to use of any particular type of rod string, or to use of a rod string at all. It is only necessary for purposes of this disclosure to communicate reciprocating motion from the actuator 14 to the downhole pump 20, and it is therefore within the scope of this disclosure to use any structure capable of such transmission.
- the downhole pump 20 is depicted in FIG. 1 as being of the type having a stationary or “standing” valve 22 and a reciprocating or “traveling" valve 24.
- the traveling valve 24 is connected to, and reciprocates with, the rod string 18, so that fluid 26 is pumped from a wellbore 28 into a production tubing string 30.
- the downhole pump 20 is merely one example of a wide variety of different types of pumps that may be used with the well pumping system 10 and method of FIG. 1 , and so the scope of this disclosure is not limited to any of the details of the downhole pump described herein or depicted in the drawings.
- the wellbore 28 is depicted in FIG. 1 as being generally vertical, and as being lined with casing 32 and cement 34.
- a section of the wellbore 28 in which the pump 20 is disposed may be generally horizontal or otherwise inclined at any angle relative to vertical, and the wellbore section may not be cased or may not be cemented.
- the scope of this disclosure is not limited to use of the well pumping system 10 and method with any particular wellbore configuration.
- the fluid 26 originates from an earth formation 36 penetrated by the wellbore 28.
- the fluid 26 flows into the wellbore 28 via perforations 38 extending through the casing 32 and cement 34.
- the fluid 26 can be a liquid, such as oil, gas condensate, water, etc.
- the scope of this disclosure is not limited to use of the well pumping system 10 and method with any particular type of fluid, or to any particular origin of the fluid.
- the casing 32 and the production tubing string 30 extend upward to the wellhead 16 at or near the earth's surface 40 (such as, at a land-based wellsite, a subsea production facility, a floating rig, etc.).
- the production tubing string 30 can be hung off in the wellhead 16, for example, using a tubing hanger (not shown).
- a tubing hanger not shown.
- FIG. 1 only a single string of the casing 32 is illustrated in FIG. 1 for clarity, in practice multiple casing strings and optionally one or more liner strings (a liner string being a pipe that extends from a selected depth in the wellbore 28 to a shallower depth, typically sealingly "hung off” inside another pipe or casing) may be installed in the well.
- a rod blowout preventer stack 42 and a stuffing box 44 are connected between the actuator 14 and the wellhead 16.
- the rod blowout preventer stack 42 includes various types of blowout preventers (BOP's) configured for use with the rod string 18.
- BOP's blowout preventers
- one blowout preventer can prevent flow through the blowout preventer stack 42 when the rod string 18 is not present therein
- another blowout preventer can prevent flow through the blowout preventer stack 42 when the rod string 18 is present therein.
- the scope of this disclosure is not limited to use of any particular type or configuration of blowout preventer stack with the well pumping system 10 and method of FIG. 1 .
- the stuffing box 44 includes an annular seal (not visible in FIG. 1 ) about an upper end of the rod string 18.
- a reciprocating rod member 50 of the actuator 14 connects to the rod string 18 above the annular seal, although in other examples a connection between the rod member 50 and the rod string 18 may be otherwise positioned.
- the power source 12 may be connected directly to the actuator 14, or it may be positioned remotely from the actuator 14 and connected with, for example, suitable electrical cables, mechanical linkages, hydraulic hoses or pipes. Operation of the power source 12 is controlled by a control system 46.
- the control system 46 may allow for manual or automatic operation of the actuator 14 via the power source 12, based on operator inputs and measurements taken by various sensors.
- the control system 46 may be separate from, or incorporated into, the actuator 14 or the power source 12.
- at least part of the control system 46 could be remotely located or web-based, with two-way communication between the actuator 14, the power source 12 and the control system 46 being via, for example, satellite, wireless or wired transmission.
- the control system 46 can include various components, such as a programmable controller, input devices (e.g., a keyboard, a touchpad, a data port, etc.), output devices (e.g., a monitor, a printer, a recorder, a data port, indicator lights, alert or alarm devices, etc.), a processor, software (e.g., an automation program, customized programs or routines, etc.) or any other components suitable for use in controlling operation of the actuator 14 and the power source 12.
- a programmable controller e.g., a keyboard, a touchpad, a data port, etc.
- output devices e.g., a monitor, a printer, a recorder, a data port, indicator lights, alert or alarm devices, etc.
- software e.g., an automation program, customized programs or routines, etc.
- the control system 46 causes the power source 12 to increase energy input to the actuator 14, in order to raise the rod string 18. Conversely, the energy input to the actuator 14 is reduced or removed, in order to allow the rod string 18 to descend. Thus, by alternately increasing and decreasing energy input to the actuator 14, the rod string 18 is reciprocated, the downhole pump 20 is actuated and the fluid 26 is pumped out of the well.
- a "balance" energy level may be maintained in the actuator 14 to nominally offset a load due to the rod string 18 being suspended in the well (e.g., a weight of the rod string, taking account of buoyancy, inclination of the wellbore 28, friction, well pressure, etc.).
- the power source 12 is not required to increase energy input to the actuator 14 from zero to that necessary to displace the rod string 18 upwardly (along with the displaced fluid 26), and then reduce the energy input back to zero, for each reciprocation of the rod string 18. Instead, the power source 12 only has to increase energy input to the actuator 14 sufficiently greater than the balance energy level to displace the rod string 18 to its upper stroke extent, and then reduce the energy input to the actuator 14 back to the balance energy level to allow the rod string 18 to displace back to its lower stroke extent.
- the balance energy level in the actuator 14 it is not necessary for the balance energy level in the actuator 14 to exactly offset the load exerted by the rod string 18. In some examples, it may be advantageous for the balance energy level to be somewhat less than that needed to offset the load exerted by the rod string 18. In addition, it can be advantageous in some examples for the balance energy level to change over time. Thus, the scope of this disclosure is not limited to use of any particular or fixed balance energy level, or to any particular relationship between the balance energy level, any other force or energy level and/or time.
- a reciprocation speed of the rod string 18 will affect a flow rate of the fluid 26.
- a fluid interface 48 in the wellbore 28 can be affected by the flow rate of the fluid 26 from the well.
- the fluid interface 48 could be an interface between oil and water, gas and water, gas and gas condensate, gas and oil, steam and water, or any other fluids or combination of fluids.
- the fluid interface 48 may descend in the wellbore 28, so that eventually the pump 20 will no longer be able to pump the fluid 26 (a condition known to those skilled in the art as "pump-off").
- a desired flow rate of the fluid 26 may change over time (for example, due to depletion of a reservoir, changed offset well conditions, water or steam flooding characteristics, etc.).
- a "gas-locked" downhole pump 20 can result from a pump-off condition, whereby gas is received into the downhole pump 20.
- the gas is alternately expanded and compressed in the downhole pump 20 as the traveling valve 24 reciprocates, but the fluid 26 cannot flow into the downhole pump 20, due to the gas therein.
- control system 46 can automatically control operation of the actuator 14 via the power source 12 to regulate the reciprocation speed, so that pump-off is avoided, while achieving any of various desirable objectives.
- Those objectives may include maximum flow rate of the fluid 26, optimized rate of electrical power consumption, reduction of peak electrical loading, etc.
- the scope of this disclosure is not limited to pursuing or achieving any particular objective or combination of objectives via automatic reciprocation speed regulation by the control system 46.
- the power source 12 is used to variably supply energy to the actuator 14, so that the rod string 18 is displaced alternately to its upper and lower stroke extents. These extents do not necessarily correspond to maximum possible upper and lower displacement limits of the rod string 18 or the pump 20.
- valve rod bushing 25 above the traveling valve 24 it is typically undesirable for a valve rod bushing 25 above the traveling valve 24 to impact a valve rod guide 23 above the standing valve 22 when the rod string 18 displaces downward (a condition known to those skilled in the art as "pump-pound").
- the rod string 18 be displaced downward only until the valve rod bushing 25 is near its maximum possible lower displacement limit, so that it does not impact the valve rod guide 23.
- a desired stroke of the rod string 18 may change over time (for example, due to gradual lengthening of the rod string 18 as a result of lowering of a liquid level (such as at fluid interface 48) in the well, etc.).
- the control system 46 can automatically control operation of the power source 12 to regulate the upper and lower stroke extents of the rod string 18, so that pump-pound is avoided, while achieving any of various desirable objectives.
- Those objectives may include maximizing rod string 18 stroke length, maximizing production, minimizing electrical power consumption rate, minimizing peak electrical loading, etc.
- the scope of this disclosure is not limited to pursuing or achieving any particular objective or combination of objectives via automatic stroke extent regulation by the control system 46.
- the system 10 includes a continuous position sensor 52 in communication with the control system 46.
- the continuous position sensor 52 is capable of continuously detecting a position of a reciprocating member of the actuator 14 (such as the rod member 50 or another member).
- An output of the continuous position sensor 52 can be useful to achieve a variety of objectives, such as, controlling stroke distance, speed and extents to maximize production and efficiency, minimize electrical power consumption and/or peak electrical loading, maximize useful life of the rod string 18, etc.
- objectives such as, controlling stroke distance, speed and extents to maximize production and efficiency, minimize electrical power consumption and/or peak electrical loading, maximize useful life of the rod string 18, etc.
- the scope of this disclosure is not limited to pursuing or achieving any particular objective or combination of objectives via use of a continuous position sensor.
- the term “continuous” is used to refer to a substantially uninterrupted sensing of position by the sensor 52.
- the sensor 52 can detect the member's position during all portions of its reciprocating motion, and not just at certain discrete points (such as, at the upper and lower stroke extents).
- a continuous position sensor may have a particular resolution (e.g., .001-0.1 mm) at which it can detect the position of a member. Accordingly, the term “continuous" does not require an infinitely small resolution.
- the control system 46 can be provided with an accurate measurement of an actuator 14 member position at any point in the member's reciprocation, thereby dispensing with any need to perform calculations based on discrete detections of position. It will be appreciated by those skilled in the art that actual continuous position detection can be more precise than such calculations of position, since various factors (including known and unknown factors, such as, temperature, fluid compressibility, fluid leakage, etc.) can affect the calculations. However, such calculations of position may be used in keeping with the principles of this disclosure, either in conjunction with, or instead of, continuous position measurements.
- control system 46 By continuously sensing the position of a member of the actuator 14 at or near a top of the rod string 18, characteristics of the rod string's reciprocating displacement are communicated to the control system 46 at each point in the rod string's reciprocating displacement. The control system 46 can, thus, determine whether the rod string's 18 position, speed and acceleration correspond to desired preselected values.
- the control system 46 can change how energy is supplied to the actuator 14 by the power source 12, so that the reciprocating displacement will conform to the desired preselected values. For example, the control system 46 may change a level, timing, frequency, duration, etc., of the energy input to the actuator 14, in order to change the rod string's upper or lower stroke extent, or velocity or acceleration at any point in the rod string's reciprocating displacement.
- the desired preselected values may change over time. As mentioned above, it may be desirable to change the upper or lower stroke extent, or the pumping rate, during the pumping operation, for example, due to the level of the fluid interface 48 changing, reservoir depletion over time, detection of a pump-off, pump-pound or gas-lock condition, etc.
- actuators 14 that may be used with the system 10 and method are representatively illustrated. These examples are not limiting of the scope of this disclosure, but are instead provided to demonstrate that the principles disclosed herein are applicable to a wide variety of different actuator configurations.
- the actuator 14 includes a piston member 54 sealingly and reciprocably disposed in a generally cylindrical housing 56.
- the rod member 50 is connected to the piston member 54 and extends downwardly through a lower end of the housing 56.
- the power source 12 in this example comprises a hydraulic pressure source (such as, a hydraulic pump and associated equipment) for supplying energy in the form of fluid pressure to a chamber 58 in the housing 56 below the piston member 54.
- a hydraulic pressure source such as, a hydraulic pump and associated equipment
- hydraulic fluid at increased pressure is supplied to the chamber 58 from the power source 12.
- the pressure in the chamber 58 is reduced (with hydraulic fluid being returned from the chamber to the power source 12).
- the senor 52 is attached externally to the housing 56.
- the sensor 52 could be positioned internal to, or in a wall of, the housing 56.
- the scope of this disclosure is not limited to any particular position or orientation of the sensor 52.
- a magnet 60 is attached to, and displaces with, the piston member 54.
- a position of the magnet 60 (and, thus, of the piston member 54) is continuously sensed by the sensor 52 during reciprocating displacement of the piston member.
- a suitable magnet for use in the actuator 14 is a neodymium magnet (such as, a neodymium-iron-boron magnet) in ring form.
- a neodymium magnet such as, a neodymium-iron-boron magnet
- other types and shapes of magnets may be used in keeping with the principles of this disclosure.
- a suitable linear position sensor for use as the sensor 52 in the system 10 is available from Rota Engineering Ltd. of Manchester, United Kingdom.
- Other suitable position sensors are available from Hans Turck GmbH & Co. KG of Germany, and from Balluff GmbH of Germany.
- the scope of this disclosure is not limited to use of any particular sensor with the system 10.
- the senor 52 is not mounted external to the housing 56, but is instead positioned internal to another housing 62 at a lower end of the actuator 14. In this manner, the sensor 52 does not have to detect the position of the magnet 60 through a wall of the housing 62, and can be in closer proximity to the magnet.
- the magnet 60 in the FIG. 3 example is mounted to the rod member 50, instead of to the piston member 54.
- the position of any reciprocating member of the actuator 14 can be continuously detected using an appropriately configured sensor 52.
- the actuator 14 in the FIG. 3 example is not necessarily a hydraulic actuator.
- the actuator 14 comprises a cable, ribbon, tape, belt or other flexible member 64 stored on a spool 66.
- the flexible member 64 extends upwardly about a sheave member 68 and downwardly to a connection with the rod member 50.
- the spool 66 is driven by an electric motor 70 of the power source 12, so that the flexible member 64 is alternately wound and unwound about the spool, to thereby alternately raise and lower the rod member 50.
- the power source 12 and the actuator 14 may be conveniently combined, with the control system 46 controlling operation of the motor 70 to achieve a desired reciprocating displacement of the rod member 50 and rod string 18 connected thereto (see FIG. 1 ).
- the sensor 52 in the FIG. 4 example comprises a rotary encoder capable of continuously detecting a rotational position of the sheave member 68. In this manner, the position, velocity and acceleration of the sheave member 68, the flexible member 64 and the rod member 50 (and the upper end of the rod string 18) can be continuously known.
- FIG. 5 example is similar in some respects to the FIG. 4 example, but the actuator 14 in the FIG. 5 example comprises a hydraulic cylinder 72 for alternately raising and lowering the sheave member 68 to thereby alternately raise and lower the rod member 50.
- the FIG. 5 power source 12 comprises a hydraulic pressure source to alternately increase and decrease fluid pressure applied to the cylinder 72.
- the sensor 52 in the FIG. 5 example can comprise an infrared or ultrasonic sensor for sensing the position of the sheave member 68 as it reciprocates upward and downward.
- the sensor 52 could sense the position of another member of the actuator 14 as it reciprocably displaces.
- velocity profiles 74 that may be used with the system 10 and method are representatively illustrated as graphs of velocity versus position.
- the velocity profiles 74 may be used with other systems and methods, in keeping with the scope of this disclosure.
- the control system 46 can readily determine the velocity of the member at any point in the displacement of the member (velocity equals the derivative of position over time). This determination of velocity may be made by the control system 46, or in some examples the sensor 52 may provide an output of instantaneous velocity, as well as position. In other examples, acceleration (equal to the derivative of velocity over time) may also be determined by the control system 46, or may be provided as an output of the sensor 52.
- an upstroke begins at zero velocity and at a lower stroke extent 76.
- the velocity rapidly increases, and then levels off once the rod string 18 is displacing upward at a desired rate.
- the entire rod string 18 does not displace as an infinitely rigid member. Instead, the rod string 18 has some elasticity and there are dampening effects present (such as, friction between the rod string 18 and the tubing string 30, etc.), so that the reciprocating displacement of a lower end of the rod string at the downhole pump 20 is not the same as the reciprocating displacement of the upper end of the rod string at the surface.
- a wave equation in the rod string 18 can be solved, so that the velocity profile 74 to be maintained at the surface corresponds to a desired velocity profile at the downhole pump 20.
- the Everitt-Jennings algorithm may be used to solve the wave equation (see Everitt, T.A. and Jennings, J.W., An Improved Finite-Difference Calculation of Downhole Dynamometer Cards for Sucker-Rod Pumps, SPE 18189, February 1992 ).
- the full Everitt-Jennings algorithm produces a calculation of load versus position, the algorithm can be used to calculate velocity (and acceleration) as an intermediate step.
- solution of the wave equation produces a corresponding desired velocity profile at the surface (e.g., at a reciprocating member of the actuator 14, or an upper end of the rod string 18).
- the desired velocity profile (either the desired velocity profile at the surface, or the desired velocity profile at the downhole pump 20 if the wave equation is to be solved by the control system 46) may be input to the control system, and the control system can then operate the power source 12 and the actuator 14, so that any deviation of the velocity profile as detected by the sensor 52 from the desired velocity profile is minimized.
- the velocity rapidly decreases to zero velocity at the upper stroke extent 78.
- the profile 74 is depicted as being composed of straight line segments, in practice the profile would have smoother transitions.
- the downstroke in the FIG. 6 example is a mirror image of the upstroke. However, it is not necessary for this to be the case and, as discussed more fully below, it can be beneficial for there to be differences in the velocity profile 74 between the upstroke and the downstroke.
- a slope of the velocity profile 74 changes multiple times on the upstroke after the lower stroke extent 76 and prior to the upper stroke extent 78.
- the downstroke is again a mirror image of the upstroke, and so the velocity profile slope changes multiple times on the downstroke after the upper stroke extent 78 and prior to the lower stroke extent 76.
- Such changes in the velocity profile 74 may be used to account for the fact that progressively more of the rod string 20 is being displaced over time after the upper and lower stroke extents 78, 76, and that progressively more of the rod string is being slowed to zero velocity prior to the upper and lower stroke extents.
- the downstroke is a reversed mirror image of the upstroke, with multiple velocity profile slope changes after each of the lower and upper stroke extents 76, 78, and with a single velocity slope change prior to each of the lower and upper stroke extents.
- This example demonstrates that a wide variety of different shapes are possible for the velocity profile 74.
- a maximum velocity (absolute value) on the downstroke is much less than a maximum velocity on the upstroke.
- This velocity profile 74 can be beneficial in avoiding a gas-lock condition, since the reduced downstroke velocity can provide more time for the downhole pump 20 to fill, as well as provide more precise control over the lower stroke extent at the downhole pump (momentum effects on the downward moving rod string 18 are more controllable and predictable, as compared to the upstroke).
- a reduced velocity may be provided on the upstroke to reduce stresses in the rod string 18.
- the scope of this disclosure is not limited to any particular velocity profile, or to any particular relationship between upstroke and downstroke velocity profiles.
- control system 46 Since the control system 46 knows the velocity at any point during reciprocating displacement (the velocity being provided by the continuous position sensor 52 output, or being calculated by the control system based on the sensor output), the control system can at any point during the reciprocating displacement compare the detected velocity to the desired velocity, and vary operation of the power source 12 and the actuator 14 as needed to minimize any discrepancies. In this manner, the control system 46 can maintain a preselected desired velocity profile at a member of the actuator 14, the rod string 18 at the surface, and the rod string at the downhole pump 20.
- the velocity profile 74 can be changed as needed to achieve other objectives. For example, if it is desired to change the position of the lower and/or upper stroke extents 76, 78, the velocity profile 74 can be appropriately changed, and the control system 46 will accordingly change its operation of the power source 12 and the actuator 14. Similarly, the velocity profile 74 can be changed, if desired, to achieve increased efficiency, increased production, reduced rod string wear, increased rod string usable life, reduced electricity consumption or peak load, or in response to changed conditions (such as, depletion of a reservoir, pump-off, pump-pound, gas-lock, etc.).
- an example technique or method 80 for controlling operation of the well pumping system 10 is representatively illustrated in flowchart form.
- this method 80 it is desired to change one or both of the lower and upper stroke extents 76, 78 at the surface, in order to achieve a corresponding (although not necessarily equal) change in stroke extent(s) of the rod string 18 at the downhole pump 20.
- step 82 of the method 80 the stroke extents 76, 78 are detected at the surface (for example, using the continuous position sensor 52).
- the stroke extents 76, 78 in this example correspond to minimum and maximum displacement values detected by the sensor 52, and to positions at which the velocity is zero.
- the continuous position sensor 52 may detect the position of a member of the actuator 14 (such as, the rod member 50, the piston member 54, the sheave member 68 or another member), or the upper end of the rod string 18 (for example, by positioning the sensor 52 in or on the stuffing box 44).
- a member of the actuator 14 such as, the rod member 50, the piston member 54, the sheave member 68 or another member
- the scope of this disclosure is not limited to the position of any particular component being detected by the continuous position sensor 52.
- a desired change to one or both of the stroke extents 76, 78 is determined. For example, it may be desired to increase a stroke distance by changing one or both of the stroke extents 76, 78, in order to increase the pumping rate. As another example, it may be desired to raise the lower stroke extent at the downhole pump 20, in order to alleviate a pump-pound condition. As yet another example, it may be desired to change one or both of the stroke extents at the downhole pump 20, in order to increase a work output of the system 10.
- the determination of the desired change to one or both of the stroke extents 76, 78 may be made automatically by the control system 46 (for example, in response to detection of a pump-pound condition, detection of a pump-off condition, detection of a reduction in work output, etc.), or as part of a preprogrammed routine (for example, to periodically adjust the lower stroke extent, so that maximum compression is achieved on the downstroke to avoid gas-lock). Alternatively, the determination may be made elsewhere and then input to the control system 46 by a user.
- step 86 the control system 46 modifies the operation of the power source 12 and actuator 14 as needed to achieve the desired change. Since the continuous position sensor 52 provides to the control system 46 a continuous output of position during the reciprocating displacement in this example, the control system can make any appropriate changes in operation while the reciprocating displacement continues, and without any need to change the sensor's position relative to the actuator 14 or any other component of the system 10.
- the control system 46 can change operation of the power source 12 and actuator 14, for example, by varying a duration, level, relative timing, frequency, etc., of energy supplied to the actuator from the power supply 12. An example is described more fully below in relation to the graph illustrated in FIG. 12 .
- the step 84 of determining the desired change to the stroke extent(s) at the surface is more particularly expanded for a situation where it is desired to increase a work output at the downhole pump 20.
- work output at the downhole pump 20 may be monitored over time, and a decrease in work output can be indicative of a pump-pound condition.
- the method 80 can be used to change the stroke extent(s) as needed to alleviate the pump-pound condition and thereby increase the work output.
- the Elliott-Jennings algorithm may be used to solve the wave equation in the rod string 18 and determine load (force) versus position (displacement) at the downhole pump 20. Since work equals force applied over a distance, a force versus displacement curve at the downhole pump 20 (also known to those skilled in the art as a "downhole card”) can be integrated to determine work output.
- the lower stroke extent of the rod string 18 at the downhole pump 20 can be incrementally raised by the control system 46 to thereby alleviate the pump-pound condition and increase the work output. Steps 88-92 can be repeated for each increment, until the work output is sufficiently increased.
- control system 46 can monitor the work output in step 88.
- a desired change in the lower stroke extent (the amount of the incremental raising) at the downhole pump 20 is determined. This desired change in the lower stroke extent at the downhole pump 20 may be determined separately for each occurrence of a pump-pound condition, or it may be preselected (for example, by user input or initial programming of the control system 46).
- step 92 a desired change in the lower stroke extent at the surface corresponding to the desired change in the lower stroke extent at the downhole pump 20 is determined.
- the solution to the wave equation in the rod string 18 can be used to relate reciprocating displacement at the downhole pump 20 to reciprocating displacement at the surface (for example, using the Elliott-Jennings algorithm or another suitable algorithm), in order to determine the desired change in the lower stroke extent at the surface.
- the control system 46 can then modify operation of the power source 12 and actuator 14 as needed to achieve the desired change (as in step 86).
- the continuous position sensor 52 output will confirm whether the modified operation in fact achieves the desired change, and the control system 46 will make further modifications as needed to minimize any discrepancies between the detected change and the desired change in lower stroke extent at the surface.
- FIG. 12 an example graph of position and energy input versus time is representatively illustrated.
- the graph demonstrates how characteristics of the reciprocating displacement can be varied by modifying the energy input to the actuator 14 from the power source 12.
- control system 46 can control the energy input to the actuator 14 to achieve various objectives.
- an upper stroke extent e.g., of an actuator member, or the rod string 18 at the surface or at the downhole pump
- two different ways of achieving this objective are depicted in FIG. 12 .
- the position (for example, as detected by the continuous position sensor 52 and optionally resulting from a solution of the wave equation in the rod string 18) is depicted over time prior to modification of the energy input to the actuator 14.
- the energy input over time is also depicted as a solid line prior to modification.
- the upper stroke extent 78 occurs after the energy input periodically decreases to a minimum level
- the lower stroke extent 76 occurs after the energy input periodically increases to a maximum level. This is due to inertia and friction effects on the rod string 18, so that the rod string does not immediately begin to displace upward when the energy input is increased, and the rod string does not immediately begin to displace downward when the energy input is decreased.
- One technique of raising the upper stroke extent 78 is depicted in relatively long dashed lines in FIG. 12 .
- a duration of the maximum energy input level is increased, so that the rod string 18 displaces upward over a correspondingly increased duration. Since the rod string 18 displaces upward longer, the upper stroke extent 78 is raised.
- FIG. 12 Another technique of raising the upper stroke extent 78 is depicted in relatively short dashed lines in FIG. 12 .
- the maximum energy input level is increased, so that the acceleration and velocity of the rod string 18 on the upstroke is correspondingly increased. Since the rod string 18 displaces faster upward, the upper stroke extent 78 is raised.
- FIG. 12 demonstrates that a variety of different techniques and combinations of techniques may be used by the control system 46 to modify the reciprocating displacement characteristics of the rod string 18.
- Such techniques may be used to modify the velocity (including upstroke and downstroke velocity profiles), acceleration (including upstroke and downstroke acceleration profiles), lower and upper stroke extents, and stroke length of the rod string 18 at surface and at the downhole pump 20.
- FIG. 13 another example of the actuator 14 in the well pumping system 10 and associated method is representatively illustrated.
- the FIG. 13 example is similar in most respects to the FIG. 2 example, but the continuous position sensor 52 is not used in the FIG. 13 example.
- the continuous position sensor 52 could be used with the FIG. 13 example in keeping with the principles of this disclosure.
- a discrete position sensor 100 is used to detect when the magnet 60 (and, thus, the piston member 54 or another reciprocating member of the actuator 14, or the upper end of the rod string 18) is at a particular position.
- the sensor 100 is shown as being disposed between the upper and lower stroke extents of the piston 54, but in other examples, the sensor 100 could be located at or near the upper or lower stroke extent.
- a single sensor 100 is depicted in FIG. 13 .
- other numbers of sensors may be used.
- a sensor 100 could be located at or near the upper stroke extent, and another sensor 100 could be located at or near the lower stroke extent.
- the scope of this disclosure is not limited to use of any particular number or location of sensors in or on the actuator 14.
- a suitable magnetic field sensor for use as the sensor 100 is a Pepperl MB-F32-A2 magnetic flux sensing switch marketed by Pepperl+Fuchs North America of Twinsburg, Ohio USA.
- other magnetic field sensors or other types of discrete position sensors may be used in keeping with the principles of this disclosure.
- the sensor 10 is used in conjunction with a flowmeter 102 in the FIG. 13 example to continuously determine the position of the piston member 54 (or another reciprocating member of the actuator 14, or the upper end of the rod string 18).
- the flowmeter 102 measures flow of fluid between the power source 12 and the actuator 14.
- the flowmeter 102 may be a volumetric or mass flowmeter.
- the flowmeter 102 is a positive displacement volumetric flowmeter.
- other types of flow measurements may be made by the flowmeter 102 in keeping with the scope of this disclosure.
- a certain fluid volume will correspond to a certain displacement of the piston member 54 (displacement equals fluid volume divided by piston area). If a mass flowmeter is used, the fluid volume can be determined from the density of the fluid (volume equals mass divided by density).
- the position of the piston member 54 at every point in its reciprocating displacement can be readily determined (current position equals previous position plus displacement).
- the sensor 100 can also be used for calibration of the flowmeter 102, for example, to compensate for compressibility of the fluid, leakage of fluid, etc.
- the position, displacement, velocity (derivative of displacement over time) and acceleration (derivative of velocity over time) of the piston member 54 can be known continuously during the reciprocation of the rod string 18.
- the control system 46 can use this information as described above to control the reciprocating displacement of the rod string 18.
- a pressure sensor 104 can be used to monitor pressure in the chamber 58, so that compressibility of the fluid can be compensated for in the displacement calculation.
- a temperature sensor 106 can also be used to monitor the temperature of the fluid, for example, in the event that a gas is entrained in the fluid (so that its volume changes substantially in response to temperature changes), or the fluid is of a type (such as silicone-based hydraulic fluid) that has a relatively high coefficient of thermal expansion. If a mass flowmeter is used for the flowmeter 102, it will be appreciated that volume calculations will be aided by the temperature measurements provided by the temperature sensor 106 (since for most fluids density changes in response to temperature changes).
- FIG. 14 another example of the actuator 14 in the system 10 is representatively illustrated.
- the FIG. 14 example is similar in most respects to the example of FIG. 3 , but in the FIG. 14 example multiple discrete position sensors 100 are used in place of the continuous position sensor 52, and the flowmeter 102, pressure sensor 104 and temperature sensor 106 are used for improved accuracy.
- one of the position sensors 100 is located at or near each of the upper and lower stroke extents of the magnet 60.
- position calculations based on measurements made by the flowmeter 102 are more readily calibrated.
- the piston area of the piston member 54 multiplied by the known distance between the sensors 100 equals the change in volume of the chamber 58. If the change in volume calculated based on the flowmeter 102 measurements does not equal the change in volume detected based on the output of the sensors 100, an appropriate calibration coefficient can be applied as needed.
- Another type of discrete position sensor that may be used for the sensors 100 in the FIG. 14 example is a photoelectric sensor.
- an optically discernible member such as, a member having a color, texture, refractive index or other optical characteristic different from the surrounding environment
- the scope of this disclosure is not limited to use of any particular type of sensor, or to any particular technique for detecting position.
- any number of sensors may be used in keeping with the principles of this disclosure.
- the sensors 100 are described above as being located at or near the upper and lower stroke extents of the magnet 60, the sensors may be otherwise located.
- the scope of this disclosure is not limited to any of the details of the sensor(s) 100 placement, quantity, configuration or arrangement as depicted in FIGS. 13 & 14 , or as described above.
- any of the sensors 52, 100, 102, 104, 106 described above may be used alone or in combination with any of the other sensors.
- the flowmeter 102 could be used alone to determine the position, displacement, velocity and acceleration of a member of the actuator 14 (or the upper end of the rod string 18) with acceptable accuracy in some situations.
- One discrete position sensor 100 would provide for convenient initialization and calibration of the displacement determinations, and multiple sensors 100 provide for enhanced accuracy, but use of these sensors is not necessary in keeping with the principles of this disclosure.
- the well pumping system 10 can be precisely controlled, in part by utilizing the continuous position sensor 52 to provide substantially continuous output of position to the control system 46 as the actuator 14 reciprocates the rod string 18.
- the flowmeter 102, discrete position sensor(s) 100 and/or other sensors 104, 106 may be used instead of, or in addition to, the continuous position sensor 52 for determining displacement of a member of the actuator 14 or an upper end of the rod string 18.
- the system 10 can include an actuator 14 that reciprocably displaces a rod string 18, a flowmeter 102 that measures flow of a fluid between a power source 12 and the actuator 14, and a control system 46 that modifies reciprocal displacement of the rod string 18 by the actuator 14, in response to an output of the flowmeter 102.
- the well pumping system 10 can also include at least one discrete position sensor 100 that detects when a member (e.g., rod member 50, piston member 54, magnet 60) of the actuator 14 or an upper end of the rod string 18 is at a predetermined position.
- a member e.g., rod member 50, piston member 54, magnet 60
- the control system 46 may modify a stroke extent of a member (e.g., rod member 50, piston member 54, magnet 60) of the actuator 14, or a stroke extent of the rod string 18 at surface or proximate a downhole pump 20, in response to the output of the flowmeter 102.
- a member e.g., rod member 50, piston member 54, magnet 60
- the control system 46 may maintain a preselected velocity profile 74 of a member of the actuator 14, or of the rod string 18 at surface or at a downhole pump 20, in response to the output of the flowmeter.
- a well pumping method 80 is also provided to the art by the above disclosure.
- the method 80 can include reciprocably displacing a rod string 18, continuously determining a velocity profile 74 of the rod string 18, and modifying the velocity profile 74 while the rod string 18 reciprocably displaces, in response to an output of a flowmeter 102.
- the modifying step can comprise changing a duration of the velocity profile 74.
- the changing may be performed while the rod string 18 reciprocably displaces.
- the modifying step can comprise changing a position at which an actuator member velocity is zero, the position being detected based on the output of the flowmeter 102.
- the changing may be performed while the rod string 18 reciprocably displaces.
- the modifying step may comprise changing a position at which the rod string 18 velocity is zero at a downhole pump 20.
- the changing can comprise solving a wave equation in the rod string 18.
- the modifying step may comprise minimizing differences between the detected velocity profile and a preselected velocity profile.
- the modifying step may comprise maintaining acceleration of the rod string 18 less than a preselected level.
- the method comprises reciprocably displacing a rod string 18 with an actuator 14, continuously determining displacement in response to an output of a flowmeter 102, and modifying reciprocating displacement of the rod string 18 by the actuator 14, in response to the output of the flowmeter 102.
- the determined displacement may be calibrated in response to an output of at least one discrete position sensor 100.
- the modifying step may comprise varying a periodic energy input to the actuator 14 relative to the reciprocating displacement of the rod string 18.
- the varying can comprise varying a duration of the energy input and/or varying a level of the energy input.
- the modifying step may comprise varying a stroke extent.
- the varying can include displacing the stroke extent until either: a) the stroke extent is positioned at a preselected stroke extent, or b) the stroke extent has displaced a preselected distance.
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Description
- This disclosure relates generally to equipment utilized and operations performed in conjunction with a subterranean well and, in one example described below, more particularly provides a well pumping system and associated method. Certain embodiments provide operational control of a wellsite pumping unit with displacement determination.
- Reservoir fluids can sometimes flow to the earth's surface when a well has been completed. However, with some wells, reservoir pressure may be insufficient (at the time of well completion or thereafter) to lift the fluids (in particular, liquids) to the surface. In those circumstances, technology known as "artificial lift" can be employed to bring the fluids to or near the surface (such as a subsea production facility or pipeline, a floating rig, etc.).
- Various types of artificial lift technology are known to those skilled in the art. In one type of artificial lift, a downhole pump is operated by reciprocating a string of "sucker" rods deployed in a well. An apparatus (such as, a walking beam-type pump jack or a hydraulic actuator) located at the surface can be used to reciprocate the rod string.
- The inventors have appreciated that improvements are continually needed in the arts of constructing and operating artificial lift systems. Such improvements may be useful for lifting oil, water, gas condensate or other liquids from wells, may be useful with various types of wells (such as, gas production wells, oil production wells, water or steam flooded oil wells, geothermal wells, etc.), and may be useful for any other application where reciprocating motion is desired.
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CA2826593A1 describes an electronic control system that controls movement of the piston as it moves between the upper and lower rod positions. -
US 5996688 proposes a hydraulic pump jack drive system. - Aspects of the invention are set out in the accompanying claims
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FIG. 1 is a representative partially cross-sectional view of an example of a well pumping system and associated method which can embody principles of this disclosure. -
FIGS. 2-5 are representative views of actuator examples and continuous position sensor examples. -
FIGS. 6-9 are representative graphs of example velocity profiles. -
FIGS. 10 & 11 are representative flowcharts for techniques of controlling operation of the well pumping system. -
FIG. 12 is a representative example graph of position and energy input versus time, with modifications thereof. -
FIGS. 13 & 14 are representative views of further actuator examples. - Representatively illustrated in
FIG. 1 is a wellpumping system 10 and associated method for use with a subterranean well, which system and method can embody principles of this disclosure. However, it should be clearly understood that the well pumpingsystem 10 and method are merely one example of an application of the principles of this disclosure in practice, and a wide variety of other examples are possible. Therefore, the scope of this disclosure is not limited at all to the details of thesystem 10 and method as described herein or depicted in the drawings. - In the
FIG. 1 example, apower source 12 is used to supply energy to anactuator 14 mounted on awellhead 16. In response, theactuator 14 reciprocates arod string 18 extending into the well, thereby operating adownhole pump 20. - The
rod string 18 may be made up of individual sucker rods connected to each other, although other types of rods or tubes may be used, therod string 18 may be continuous or segmented, a material of therod string 18 may comprise steel, composites or other materials, and elements other than rods may be included in the string. Thus, the scope of this disclosure is not limited to use of any particular type of rod string, or to use of a rod string at all. It is only necessary for purposes of this disclosure to communicate reciprocating motion from theactuator 14 to thedownhole pump 20, and it is therefore within the scope of this disclosure to use any structure capable of such transmission. - The
downhole pump 20 is depicted inFIG. 1 as being of the type having a stationary or "standing"valve 22 and a reciprocating or "traveling"valve 24. Thetraveling valve 24 is connected to, and reciprocates with, therod string 18, so thatfluid 26 is pumped from awellbore 28 into aproduction tubing string 30. However, it should be clearly understood that thedownhole pump 20 is merely one example of a wide variety of different types of pumps that may be used with the wellpumping system 10 and method ofFIG. 1 , and so the scope of this disclosure is not limited to any of the details of the downhole pump described herein or depicted in the drawings. - The
wellbore 28 is depicted inFIG. 1 as being generally vertical, and as being lined withcasing 32 andcement 34. In other examples, a section of thewellbore 28 in which thepump 20 is disposed may be generally horizontal or otherwise inclined at any angle relative to vertical, and the wellbore section may not be cased or may not be cemented. Thus, the scope of this disclosure is not limited to use of the wellpumping system 10 and method with any particular wellbore configuration. - In the
FIG. 1 example, thefluid 26 originates from anearth formation 36 penetrated by thewellbore 28. Thefluid 26 flows into thewellbore 28 viaperforations 38 extending through thecasing 32 andcement 34. Thefluid 26 can be a liquid, such as oil, gas condensate, water, etc. However, the scope of this disclosure is not limited to use of the wellpumping system 10 and method with any particular type of fluid, or to any particular origin of the fluid. - As depicted in
FIG. 1 , thecasing 32 and theproduction tubing string 30 extend upward to thewellhead 16 at or near the earth's surface 40 (such as, at a land-based wellsite, a subsea production facility, a floating rig, etc.). Theproduction tubing string 30 can be hung off in thewellhead 16, for example, using a tubing hanger (not shown). Although only a single string of thecasing 32 is illustrated inFIG. 1 for clarity, in practice multiple casing strings and optionally one or more liner strings (a liner string being a pipe that extends from a selected depth in thewellbore 28 to a shallower depth, typically sealingly "hung off" inside another pipe or casing) may be installed in the well. - In the
FIG. 1 example, a rodblowout preventer stack 42 and astuffing box 44 are connected between theactuator 14 and thewellhead 16. The rodblowout preventer stack 42 includes various types of blowout preventers (BOP's) configured for use with therod string 18. For example, one blowout preventer can prevent flow through theblowout preventer stack 42 when therod string 18 is not present therein, and another blowout preventer can prevent flow through theblowout preventer stack 42 when therod string 18 is present therein. However, the scope of this disclosure is not limited to use of any particular type or configuration of blowout preventer stack with the wellpumping system 10 and method ofFIG. 1 . - The
stuffing box 44 includes an annular seal (not visible inFIG. 1 ) about an upper end of therod string 18. A reciprocatingrod member 50 of theactuator 14 connects to therod string 18 above the annular seal, although in other examples a connection between therod member 50 and therod string 18 may be otherwise positioned. - The
power source 12 may be connected directly to theactuator 14, or it may be positioned remotely from theactuator 14 and connected with, for example, suitable electrical cables, mechanical linkages, hydraulic hoses or pipes. Operation of thepower source 12 is controlled by acontrol system 46. - The
control system 46 may allow for manual or automatic operation of theactuator 14 via thepower source 12, based on operator inputs and measurements taken by various sensors. Thecontrol system 46 may be separate from, or incorporated into, theactuator 14 or thepower source 12. In one example, at least part of thecontrol system 46 could be remotely located or web-based, with two-way communication between theactuator 14, thepower source 12 and thecontrol system 46 being via, for example, satellite, wireless or wired transmission. - The
control system 46 can include various components, such as a programmable controller, input devices (e.g., a keyboard, a touchpad, a data port, etc.), output devices (e.g., a monitor, a printer, a recorder, a data port, indicator lights, alert or alarm devices, etc.), a processor, software (e.g., an automation program, customized programs or routines, etc.) or any other components suitable for use in controlling operation of theactuator 14 and thepower source 12. The scope of this disclosure is not limited to any particular type or configuration of a control system. - In operation of the well
pumping system 10 ofFIG. 1 , thecontrol system 46 causes thepower source 12 to increase energy input to theactuator 14, in order to raise therod string 18. Conversely, the energy input to theactuator 14 is reduced or removed, in order to allow therod string 18 to descend. Thus, by alternately increasing and decreasing energy input to theactuator 14, therod string 18 is reciprocated, thedownhole pump 20 is actuated and thefluid 26 is pumped out of the well. - Note that, when energy input to the
actuator 14 is decreased to allow therod string 18 to displace downward (as viewed inFIG. 1 ), the energy input may not be decreased to zero. Instead, a "balance" energy level may be maintained in theactuator 14 to nominally offset a load due to therod string 18 being suspended in the well (e.g., a weight of the rod string, taking account of buoyancy, inclination of thewellbore 28, friction, well pressure, etc.). - In this manner, the
power source 12 is not required to increase energy input to theactuator 14 from zero to that necessary to displace therod string 18 upwardly (along with the displaced fluid 26), and then reduce the energy input back to zero, for each reciprocation of therod string 18. Instead, thepower source 12 only has to increase energy input to theactuator 14 sufficiently greater than the balance energy level to displace therod string 18 to its upper stroke extent, and then reduce the energy input to theactuator 14 back to the balance energy level to allow therod string 18 to displace back to its lower stroke extent. - Note that it is not necessary for the balance energy level in the
actuator 14 to exactly offset the load exerted by therod string 18. In some examples, it may be advantageous for the balance energy level to be somewhat less than that needed to offset the load exerted by therod string 18. In addition, it can be advantageous in some examples for the balance energy level to change over time. Thus, the scope of this disclosure is not limited to use of any particular or fixed balance energy level, or to any particular relationship between the balance energy level, any other force or energy level and/or time. - A reciprocation speed of the
rod string 18 will affect a flow rate of the fluid 26. Generally speaking, the faster the reciprocation speed at a given length of stroke of therod string 18, the greater the flow rate of the fluid 26 from the well (to a point). - It can be advantageous to control the reciprocation speed, instead of reciprocating the
rod string 18 as fast as possible. For example, afluid interface 48 in thewellbore 28 can be affected by the flow rate of the fluid 26 from the well. Thefluid interface 48 could be an interface between oil and water, gas and water, gas and gas condensate, gas and oil, steam and water, or any other fluids or combination of fluids. - If the flow rate is too great, the
fluid interface 48 may descend in thewellbore 28, so that eventually thepump 20 will no longer be able to pump the fluid 26 (a condition known to those skilled in the art as "pump-off"). On the other hand, it is typically desirable for the flow rate of the fluid 26 to be at a maximum level that does not result in pump-off. In addition, a desired flow rate of the fluid 26 may change over time (for example, due to depletion of a reservoir, changed offset well conditions, water or steam flooding characteristics, etc.). - A "gas-locked"
downhole pump 20 can result from a pump-off condition, whereby gas is received into thedownhole pump 20. The gas is alternately expanded and compressed in thedownhole pump 20 as the travelingvalve 24 reciprocates, but the fluid 26 cannot flow into thedownhole pump 20, due to the gas therein. - In the
FIG. 1 well pumpingsystem 10 and method, thecontrol system 46 can automatically control operation of theactuator 14 via thepower source 12 to regulate the reciprocation speed, so that pump-off is avoided, while achieving any of various desirable objectives. Those objectives may include maximum flow rate of the fluid 26, optimized rate of electrical power consumption, reduction of peak electrical loading, etc. However, it should be clearly understood that the scope of this disclosure is not limited to pursuing or achieving any particular objective or combination of objectives via automatic reciprocation speed regulation by thecontrol system 46. - As mentioned above, the
power source 12 is used to variably supply energy to theactuator 14, so that therod string 18 is displaced alternately to its upper and lower stroke extents. These extents do not necessarily correspond to maximum possible upper and lower displacement limits of therod string 18 or thepump 20. - For example, it is typically undesirable for a
valve rod bushing 25 above the travelingvalve 24 to impact avalve rod guide 23 above the standingvalve 22 when therod string 18 displaces downward (a condition known to those skilled in the art as "pump-pound"). Thus, it is preferred that therod string 18 be displaced downward only until thevalve rod bushing 25 is near its maximum possible lower displacement limit, so that it does not impact thevalve rod guide 23. - On the other hand, the longer the stroke distance (without impact), the greater the productivity and efficiency of the pumping operation (within practical limits), and the greater the compression of fluid between the standing and traveling
valves 22, 24 (e.g., to avoid gas-lock). In addition, a desired stroke of therod string 18 may change over time (for example, due to gradual lengthening of therod string 18 as a result of lowering of a liquid level (such as at fluid interface 48) in the well, etc.). - In the
FIG. 1 well pumpingsystem 10 and method, thecontrol system 46 can automatically control operation of thepower source 12 to regulate the upper and lower stroke extents of therod string 18, so that pump-pound is avoided, while achieving any of various desirable objectives. Those objectives may include maximizingrod string 18 stroke length, maximizing production, minimizing electrical power consumption rate, minimizing peak electrical loading, etc. However, it should be clearly understood that the scope of this disclosure is not limited to pursuing or achieving any particular objective or combination of objectives via automatic stroke extent regulation by thecontrol system 46. - In the
FIG. 1 example, thesystem 10 includes acontinuous position sensor 52 in communication with thecontrol system 46. Thecontinuous position sensor 52 is capable of continuously detecting a position of a reciprocating member of the actuator 14 (such as therod member 50 or another member). - An output of the
continuous position sensor 52 can be useful to achieve a variety of objectives, such as, controlling stroke distance, speed and extents to maximize production and efficiency, minimize electrical power consumption and/or peak electrical loading, maximize useful life of therod string 18, etc. However, the scope of this disclosure is not limited to pursuing or achieving any particular objective or combination of objectives via use of a continuous position sensor. - As used herein, the term "continuous" is used to refer to a substantially uninterrupted sensing of position by the
sensor 52. For example, when used to continuously detect the position of therod member 50, thesensor 52 can detect the member's position during all portions of its reciprocating motion, and not just at certain discrete points (such as, at the upper and lower stroke extents). However, a continuous position sensor may have a particular resolution (e.g., .001-0.1 mm) at which it can detect the position of a member. Accordingly, the term "continuous" does not require an infinitely small resolution. - Using the
continuous position sensor 52, thecontrol system 46 can be provided with an accurate measurement of anactuator 14 member position at any point in the member's reciprocation, thereby dispensing with any need to perform calculations based on discrete detections of position. It will be appreciated by those skilled in the art that actual continuous position detection can be more precise than such calculations of position, since various factors (including known and unknown factors, such as, temperature, fluid compressibility, fluid leakage, etc.) can affect the calculations. However, such calculations of position may be used in keeping with the principles of this disclosure, either in conjunction with, or instead of, continuous position measurements. - By continuously sensing the position of a member of the
actuator 14 at or near a top of therod string 18, characteristics of the rod string's reciprocating displacement are communicated to thecontrol system 46 at each point in the rod string's reciprocating displacement. Thecontrol system 46 can, thus, determine whether the rod string's 18 position, speed and acceleration correspond to desired preselected values. - If there is a discrepancy between the desired preselected values and the rod string's reciprocating displacement as detected by the
sensor 52, thecontrol system 46 can change how energy is supplied to theactuator 14 by thepower source 12, so that the reciprocating displacement will conform to the desired preselected values. For example, thecontrol system 46 may change a level, timing, frequency, duration, etc., of the energy input to theactuator 14, in order to change the rod string's upper or lower stroke extent, or velocity or acceleration at any point in the rod string's reciprocating displacement. - Note that the desired preselected values may change over time. As mentioned above, it may be desirable to change the upper or lower stroke extent, or the pumping rate, during the pumping operation, for example, due to the level of the
fluid interface 48 changing, reservoir depletion over time, detection of a pump-off, pump-pound or gas-lock condition, etc. - Referring additionally now to
FIGS. 2-5 , examples ofdifferent actuators 14 that may be used with thesystem 10 and method are representatively illustrated. These examples are not limiting of the scope of this disclosure, but are instead provided to demonstrate that the principles disclosed herein are applicable to a wide variety of different actuator configurations. - In
FIG. 2 , theactuator 14 includes apiston member 54 sealingly and reciprocably disposed in a generallycylindrical housing 56. Therod member 50 is connected to thepiston member 54 and extends downwardly through a lower end of thehousing 56. - The
power source 12 in this example comprises a hydraulic pressure source (such as, a hydraulic pump and associated equipment) for supplying energy in the form of fluid pressure to achamber 58 in thehousing 56 below thepiston member 54. To raise thepiston member 54, therod member 50 and therod string 18, hydraulic fluid at increased pressure is supplied to thechamber 58 from thepower source 12. To cause thepiston member 54,rod member 50 androd string 18 to descend, the pressure in thechamber 58 is reduced (with hydraulic fluid being returned from the chamber to the power source 12). - In this example, the
sensor 52 is attached externally to thehousing 56. In other examples, thesensor 52 could be positioned internal to, or in a wall of, thehousing 56. The scope of this disclosure is not limited to any particular position or orientation of thesensor 52. - A
magnet 60 is attached to, and displaces with, thepiston member 54. A position of the magnet 60 (and, thus, of the piston member 54) is continuously sensed by thesensor 52 during reciprocating displacement of the piston member. A suitable magnet for use in theactuator 14 is a neodymium magnet (such as, a neodymium-iron-boron magnet) in ring form. However, other types and shapes of magnets may be used in keeping with the principles of this disclosure. - A suitable linear position sensor (or linear variable displacement transducer) for use as the
sensor 52 in thesystem 10 is available from Rota Engineering Ltd. of Manchester, United Kingdom. Other suitable position sensors are available from Hans Turck GmbH & Co. KG of Germany, and from Balluff GmbH of Germany. However, the scope of this disclosure is not limited to use of any particular sensor with thesystem 10. - In the
FIG. 3 example, thesensor 52 is not mounted external to thehousing 56, but is instead positioned internal to anotherhousing 62 at a lower end of theactuator 14. In this manner, thesensor 52 does not have to detect the position of themagnet 60 through a wall of thehousing 62, and can be in closer proximity to the magnet. - In addition, the
magnet 60 in theFIG. 3 example is mounted to therod member 50, instead of to thepiston member 54. Thus, the position of any reciprocating member of theactuator 14 can be continuously detected using an appropriately configuredsensor 52. Note that theactuator 14 in theFIG. 3 example is not necessarily a hydraulic actuator. - In the
FIG. 4 example, theactuator 14 comprises a cable, ribbon, tape, belt or otherflexible member 64 stored on aspool 66. Theflexible member 64 extends upwardly about asheave member 68 and downwardly to a connection with therod member 50. - The
spool 66 is driven by anelectric motor 70 of thepower source 12, so that theflexible member 64 is alternately wound and unwound about the spool, to thereby alternately raise and lower therod member 50. In this example, thepower source 12 and theactuator 14 may be conveniently combined, with thecontrol system 46 controlling operation of themotor 70 to achieve a desired reciprocating displacement of therod member 50 androd string 18 connected thereto (seeFIG. 1 ). - The
sensor 52 in theFIG. 4 example comprises a rotary encoder capable of continuously detecting a rotational position of thesheave member 68. In this manner, the position, velocity and acceleration of thesheave member 68, theflexible member 64 and the rod member 50 (and the upper end of the rod string 18) can be continuously known. - The
FIG. 5 example is similar in some respects to theFIG. 4 example, but theactuator 14 in theFIG. 5 example comprises ahydraulic cylinder 72 for alternately raising and lowering thesheave member 68 to thereby alternately raise and lower therod member 50. Similar to theFIG. 2 example, theFIG. 5 power source 12 comprises a hydraulic pressure source to alternately increase and decrease fluid pressure applied to thecylinder 72. - The
sensor 52 in theFIG. 5 example can comprise an infrared or ultrasonic sensor for sensing the position of thesheave member 68 as it reciprocates upward and downward. Alternatively, thesensor 52 could sense the position of another member of theactuator 14 as it reciprocably displaces. - Referring additionally now to
FIGS. 6-9 , examples ofvelocity profiles 74 that may be used with thesystem 10 and method are representatively illustrated as graphs of velocity versus position. The velocity profiles 74 may be used with other systems and methods, in keeping with the scope of this disclosure. - Since the position of a reciprocating member of the actuator 14 (or an upper end of the rod string 18) can be detected at any point in the displacement of the member, the
control system 46 can readily determine the velocity of the member at any point in the displacement of the member (velocity equals the derivative of position over time). This determination of velocity may be made by thecontrol system 46, or in some examples thesensor 52 may provide an output of instantaneous velocity, as well as position. In other examples, acceleration (equal to the derivative of velocity over time) may also be determined by thecontrol system 46, or may be provided as an output of thesensor 52. - In the
FIG. 6 example, an upstroke begins at zero velocity and at alower stroke extent 76. The velocity rapidly increases, and then levels off once therod string 18 is displacing upward at a desired rate. Note that theentire rod string 18 does not displace as an infinitely rigid member. Instead, therod string 18 has some elasticity and there are dampening effects present (such as, friction between therod string 18 and thetubing string 30, etc.), so that the reciprocating displacement of a lower end of the rod string at thedownhole pump 20 is not the same as the reciprocating displacement of the upper end of the rod string at the surface. - Accordingly, a wave equation in the
rod string 18 can be solved, so that thevelocity profile 74 to be maintained at the surface corresponds to a desired velocity profile at thedownhole pump 20. The Everitt-Jennings algorithm may be used to solve the wave equation (see Everitt, T.A. and Jennings, J.W., An Improved Finite-Difference Calculation of Downhole Dynamometer Cards for Sucker-Rod Pumps, SPE 18189, February 1992). Although the full Everitt-Jennings algorithm produces a calculation of load versus position, the algorithm can be used to calculate velocity (and acceleration) as an intermediate step. - Thus, working "backward" from a desired velocity profile at the
downhole pump 20, solution of the wave equation produces a corresponding desired velocity profile at the surface (e.g., at a reciprocating member of theactuator 14, or an upper end of the rod string 18). The desired velocity profile (either the desired velocity profile at the surface, or the desired velocity profile at thedownhole pump 20 if the wave equation is to be solved by the control system 46) may be input to the control system, and the control system can then operate thepower source 12 and theactuator 14, so that any deviation of the velocity profile as detected by thesensor 52 from the desired velocity profile is minimized. - Referring again to the
velocity profile 74 ofFIG. 6 , it will be appreciated that, when the velocity increases rapidly from thelower stroke extent 76, the upper end of therod string 18 will begin displacing before the lower end of the rod string. Thus, the rapid velocity increase can be used to obtain displacement of the lower end of therod string 18 relatively quickly, and then the velocity can level off once the entire rod string is displacing. - Near an end of the upstroke, the velocity rapidly decreases to zero velocity at the
upper stroke extent 78. Note that there is desirably a slope to theprofile 74 prior to the upper stokeextent 78, instead of an abrupt reversal of direction, which would be inefficient and possibly damaging to system components. Similarly, although theprofile 74 is depicted as being composed of straight line segments, in practice the profile would have smoother transitions. - The downstroke in the
FIG. 6 example is a mirror image of the upstroke. However, it is not necessary for this to be the case and, as discussed more fully below, it can be beneficial for there to be differences in thevelocity profile 74 between the upstroke and the downstroke. - In the
FIG. 7 example, a slope of thevelocity profile 74 changes multiple times on the upstroke after thelower stroke extent 76 and prior to theupper stroke extent 78. The downstroke is again a mirror image of the upstroke, and so the velocity profile slope changes multiple times on the downstroke after theupper stroke extent 78 and prior to thelower stroke extent 76. - Such changes in the
velocity profile 74 may be used to account for the fact that progressively more of therod string 20 is being displaced over time after the upper andlower stroke extents - In the
FIG. 8 example, the downstroke is a reversed mirror image of the upstroke, with multiple velocity profile slope changes after each of the lower andupper stroke extents velocity profile 74. - In the
FIG. 9 example, a maximum velocity (absolute value) on the downstroke is much less than a maximum velocity on the upstroke. Thisvelocity profile 74 can be beneficial in avoiding a gas-lock condition, since the reduced downstroke velocity can provide more time for thedownhole pump 20 to fill, as well as provide more precise control over the lower stroke extent at the downhole pump (momentum effects on the downward movingrod string 18 are more controllable and predictable, as compared to the upstroke). In other examples, a reduced velocity may be provided on the upstroke to reduce stresses in therod string 18. Thus, the scope of this disclosure is not limited to any particular velocity profile, or to any particular relationship between upstroke and downstroke velocity profiles. - Since the
control system 46 knows the velocity at any point during reciprocating displacement (the velocity being provided by thecontinuous position sensor 52 output, or being calculated by the control system based on the sensor output), the control system can at any point during the reciprocating displacement compare the detected velocity to the desired velocity, and vary operation of thepower source 12 and theactuator 14 as needed to minimize any discrepancies. In this manner, thecontrol system 46 can maintain a preselected desired velocity profile at a member of theactuator 14, therod string 18 at the surface, and the rod string at thedownhole pump 20. - In addition, the
velocity profile 74 can be changed as needed to achieve other objectives. For example, if it is desired to change the position of the lower and/orupper stroke extents velocity profile 74 can be appropriately changed, and thecontrol system 46 will accordingly change its operation of thepower source 12 and theactuator 14. Similarly, thevelocity profile 74 can be changed, if desired, to achieve increased efficiency, increased production, reduced rod string wear, increased rod string usable life, reduced electricity consumption or peak load, or in response to changed conditions (such as, depletion of a reservoir, pump-off, pump-pound, gas-lock, etc.). - Referring additionally now to
FIGS. 10 & 11 , an example technique ormethod 80 for controlling operation of thewell pumping system 10 is representatively illustrated in flowchart form. In thismethod 80, it is desired to change one or both of the lower andupper stroke extents rod string 18 at thedownhole pump 20. - Similar methods or techniques may be used to achieve other changes in the reciprocating displacement of the
rod string 18 at thedownhole pump 20. For example, similar methods may be used to change velocity, acceleration or stroke length of therod string 18 at thedownhole pump 20. Thus, the scope of this disclosure is not limited to any particular change made in the reciprocating displacement of therod string 18. - In
step 82 of themethod 80, thestroke extents sensor 52, and to positions at which the velocity is zero. - The
continuous position sensor 52 may detect the position of a member of the actuator 14 (such as, therod member 50, thepiston member 54, thesheave member 68 or another member), or the upper end of the rod string 18 (for example, by positioning thesensor 52 in or on the stuffing box 44). The scope of this disclosure is not limited to the position of any particular component being detected by thecontinuous position sensor 52. - In
step 84, a desired change to one or both of thestroke extents stroke extents downhole pump 20, in order to alleviate a pump-pound condition. As yet another example, it may be desired to change one or both of the stroke extents at thedownhole pump 20, in order to increase a work output of thesystem 10. - The determination of the desired change to one or both of the
stroke extents control system 46 by a user. - In
step 86, thecontrol system 46 modifies the operation of thepower source 12 andactuator 14 as needed to achieve the desired change. Since thecontinuous position sensor 52 provides to the control system 46 a continuous output of position during the reciprocating displacement in this example, the control system can make any appropriate changes in operation while the reciprocating displacement continues, and without any need to change the sensor's position relative to theactuator 14 or any other component of thesystem 10. - The
control system 46 can change operation of thepower source 12 andactuator 14, for example, by varying a duration, level, relative timing, frequency, etc., of energy supplied to the actuator from thepower supply 12. An example is described more fully below in relation to the graph illustrated inFIG. 12 . - In
FIG. 11 , thestep 84 of determining the desired change to the stroke extent(s) at the surface is more particularly expanded for a situation where it is desired to increase a work output at thedownhole pump 20. For example, work output at thedownhole pump 20 may be monitored over time, and a decrease in work output can be indicative of a pump-pound condition. Thus, if a decrease in work output at thedownhole pump 20 is detected, themethod 80 can be used to change the stroke extent(s) as needed to alleviate the pump-pound condition and thereby increase the work output. - As mentioned above, the Elliott-Jennings algorithm may be used to solve the wave equation in the
rod string 18 and determine load (force) versus position (displacement) at thedownhole pump 20. Since work equals force applied over a distance, a force versus displacement curve at the downhole pump 20 (also known to those skilled in the art as a "downhole card") can be integrated to determine work output. - In one technique, the lower stroke extent of the
rod string 18 at thedownhole pump 20 can be incrementally raised by thecontrol system 46 to thereby alleviate the pump-pound condition and increase the work output. Steps 88-92 can be repeated for each increment, until the work output is sufficiently increased. - For example, the
control system 46 can monitor the work output instep 88. Instep 90, a desired change in the lower stroke extent (the amount of the incremental raising) at thedownhole pump 20 is determined. This desired change in the lower stroke extent at thedownhole pump 20 may be determined separately for each occurrence of a pump-pound condition, or it may be preselected (for example, by user input or initial programming of the control system 46). - In
step 92, a desired change in the lower stroke extent at the surface corresponding to the desired change in the lower stroke extent at thedownhole pump 20 is determined. Again, the solution to the wave equation in therod string 18 can be used to relate reciprocating displacement at thedownhole pump 20 to reciprocating displacement at the surface (for example, using the Elliott-Jennings algorithm or another suitable algorithm), in order to determine the desired change in the lower stroke extent at the surface. - The
control system 46 can then modify operation of thepower source 12 andactuator 14 as needed to achieve the desired change (as in step 86). Thecontinuous position sensor 52 output will confirm whether the modified operation in fact achieves the desired change, and thecontrol system 46 will make further modifications as needed to minimize any discrepancies between the detected change and the desired change in lower stroke extent at the surface. - Referring additionally now to
FIG. 12 , an example graph of position and energy input versus time is representatively illustrated. The graph demonstrates how characteristics of the reciprocating displacement can be varied by modifying the energy input to the actuator 14 from thepower source 12. - As discussed above, the
control system 46 can control the energy input to theactuator 14 to achieve various objectives. In theFIG. 12 example, an upper stroke extent (e.g., of an actuator member, or therod string 18 at the surface or at the downhole pump) is desired to be raised, and two different ways of achieving this objective are depicted inFIG. 12 . - In a solid line, the position (for example, as detected by the
continuous position sensor 52 and optionally resulting from a solution of the wave equation in the rod string 18) is depicted over time prior to modification of the energy input to theactuator 14. The energy input over time is also depicted as a solid line prior to modification. - Note that the
upper stroke extent 78 occurs after the energy input periodically decreases to a minimum level, and thelower stroke extent 76 occurs after the energy input periodically increases to a maximum level. This is due to inertia and friction effects on therod string 18, so that the rod string does not immediately begin to displace upward when the energy input is increased, and the rod string does not immediately begin to displace downward when the energy input is decreased. - One technique of raising the
upper stroke extent 78 is depicted in relatively long dashed lines inFIG. 12 . In this technique, a duration of the maximum energy input level is increased, so that therod string 18 displaces upward over a correspondingly increased duration. Since therod string 18 displaces upward longer, theupper stroke extent 78 is raised. - Another technique of raising the
upper stroke extent 78 is depicted in relatively short dashed lines inFIG. 12 . In this technique, the maximum energy input level is increased, so that the acceleration and velocity of therod string 18 on the upstroke is correspondingly increased. Since therod string 18 displaces faster upward, theupper stroke extent 78 is raised. - The example of
FIG. 12 demonstrates that a variety of different techniques and combinations of techniques may be used by thecontrol system 46 to modify the reciprocating displacement characteristics of therod string 18. Such techniques may be used to modify the velocity (including upstroke and downstroke velocity profiles), acceleration (including upstroke and downstroke acceleration profiles), lower and upper stroke extents, and stroke length of therod string 18 at surface and at thedownhole pump 20. - As mentioned above, use of the
continuous position sensor 52 with thesystem 10 is not necessary. In further examples described below, other methods of determining the position of a member of theactuator 14 or an upper end of therod string 18 are provided. However, it should be clearly understood that the scope of this disclosure is not limited to any particular method or technique for determining position, displacement, velocity, acceleration or any other characteristic of reciprocating motion. - Referring additionally now to
FIG. 13 , another example of theactuator 14 in thewell pumping system 10 and associated method is representatively illustrated. TheFIG. 13 example is similar in most respects to theFIG. 2 example, but thecontinuous position sensor 52 is not used in theFIG. 13 example. However, thecontinuous position sensor 52 could be used with theFIG. 13 example in keeping with the principles of this disclosure. - As depicted in
FIG. 13 , adiscrete position sensor 100 is used to detect when the magnet 60 (and, thus, thepiston member 54 or another reciprocating member of theactuator 14, or the upper end of the rod string 18) is at a particular position. Thesensor 100 is shown as being disposed between the upper and lower stroke extents of thepiston 54, but in other examples, thesensor 100 could be located at or near the upper or lower stroke extent. - Only a
single sensor 100 is depicted inFIG. 13 . However, in other examples, other numbers of sensors may be used. For example, asensor 100 could be located at or near the upper stroke extent, and anothersensor 100 could be located at or near the lower stroke extent. The scope of this disclosure is not limited to use of any particular number or location of sensors in or on theactuator 14. - A suitable magnetic field sensor for use as the
sensor 100 is a Pepperl MB-F32-A2 magnetic flux sensing switch marketed by Pepperl+Fuchs North America of Twinsburg, Ohio USA. However, other magnetic field sensors or other types of discrete position sensors may be used in keeping with the principles of this disclosure. - The
sensor 10 is used in conjunction with aflowmeter 102 in theFIG. 13 example to continuously determine the position of the piston member 54 (or another reciprocating member of theactuator 14, or the upper end of the rod string 18). Theflowmeter 102 measures flow of fluid between thepower source 12 and theactuator 14. - The
flowmeter 102 may be a volumetric or mass flowmeter. In this example, theflowmeter 102 is a positive displacement volumetric flowmeter. However, other types of flow measurements may be made by theflowmeter 102 in keeping with the scope of this disclosure. - Assuming that the fluid displaced into and out of the
chamber 58 is incompressible and there is no fluid leakage, a certain fluid volume will correspond to a certain displacement of the piston member 54 (displacement equals fluid volume divided by piston area). If a mass flowmeter is used, the fluid volume can be determined from the density of the fluid (volume equals mass divided by density). - Combined with the position sensing provided by the
sensor 100, the position of thepiston member 54 at every point in its reciprocating displacement can be readily determined (current position equals previous position plus displacement). Thesensor 100 can also be used for calibration of theflowmeter 102, for example, to compensate for compressibility of the fluid, leakage of fluid, etc. - Thus, using the
sensor 100 andflowmeter 102, the position, displacement, velocity (derivative of displacement over time) and acceleration (derivative of velocity over time) of thepiston member 54 can be known continuously during the reciprocation of therod string 18. Thecontrol system 46 can use this information as described above to control the reciprocating displacement of therod string 18. - If the assumption that the fluid is incompressible results in an unacceptable level of inaccuracy in calculating and controlling the reciprocating displacement, additional sensors may be used to improve accuracy. For example, a
pressure sensor 104 can be used to monitor pressure in thechamber 58, so that compressibility of the fluid can be compensated for in the displacement calculation. Atemperature sensor 106 can also be used to monitor the temperature of the fluid, for example, in the event that a gas is entrained in the fluid (so that its volume changes substantially in response to temperature changes), or the fluid is of a type (such as silicone-based hydraulic fluid) that has a relatively high coefficient of thermal expansion. If a mass flowmeter is used for theflowmeter 102, it will be appreciated that volume calculations will be aided by the temperature measurements provided by the temperature sensor 106 (since for most fluids density changes in response to temperature changes). - Referring additionally now to
FIG. 14 , another example of theactuator 14 in thesystem 10 is representatively illustrated. TheFIG. 14 example is similar in most respects to the example ofFIG. 3 , but in theFIG. 14 example multiplediscrete position sensors 100 are used in place of thecontinuous position sensor 52, and theflowmeter 102,pressure sensor 104 andtemperature sensor 106 are used for improved accuracy. - As depicted in
FIG. 14 , one of theposition sensors 100 is located at or near each of the upper and lower stroke extents of themagnet 60. By detecting arrival of themagnet 60 at multiple relatively widely spaced apart locations, position calculations based on measurements made by the flowmeter 102 (with or without use of theother sensors 104, 106) are more readily calibrated. For example, it will be appreciated that the piston area of thepiston member 54 multiplied by the known distance between thesensors 100 equals the change in volume of thechamber 58. If the change in volume calculated based on theflowmeter 102 measurements does not equal the change in volume detected based on the output of thesensors 100, an appropriate calibration coefficient can be applied as needed. - Another type of discrete position sensor that may be used for the
sensors 100 in theFIG. 14 example is a photoelectric sensor. In that case, an optically discernible member (such as, a member having a color, texture, refractive index or other optical characteristic different from the surrounding environment) could be used in place of themagnet 60. The scope of this disclosure is not limited to use of any particular type of sensor, or to any particular technique for detecting position. - Although two
position sensors 100 are depicted inFIG. 14 , any number of sensors may be used in keeping with the principles of this disclosure. Although thesensors 100 are described above as being located at or near the upper and lower stroke extents of themagnet 60, the sensors may be otherwise located. Thus, the scope of this disclosure is not limited to any of the details of the sensor(s) 100 placement, quantity, configuration or arrangement as depicted inFIGS. 13 & 14 , or as described above. - Note that any of the
sensors flowmeter 102 could be used alone to determine the position, displacement, velocity and acceleration of a member of the actuator 14 (or the upper end of the rod string 18) with acceptable accuracy in some situations. Onediscrete position sensor 100 would provide for convenient initialization and calibration of the displacement determinations, andmultiple sensors 100 provide for enhanced accuracy, but use of these sensors is not necessary in keeping with the principles of this disclosure. - It may now be fully appreciated that the above disclosure provides significant advancements to the arts of monitoring and controlling operation of a well pumping system. In examples described above, the
well pumping system 10 can be precisely controlled, in part by utilizing thecontinuous position sensor 52 to provide substantially continuous output of position to thecontrol system 46 as theactuator 14 reciprocates therod string 18. In other examples, theflowmeter 102, discrete position sensor(s) 100 and/orother sensors continuous position sensor 52 for determining displacement of a member of theactuator 14 or an upper end of therod string 18. - The above disclosure provides to the art a
well pumping system 10. In one example, thesystem 10 can include anactuator 14 that reciprocably displaces arod string 18, aflowmeter 102 that measures flow of a fluid between apower source 12 and theactuator 14, and acontrol system 46 that modifies reciprocal displacement of therod string 18 by theactuator 14, in response to an output of theflowmeter 102. - The
well pumping system 10 can also include at least onediscrete position sensor 100 that detects when a member (e.g.,rod member 50,piston member 54, magnet 60) of theactuator 14 or an upper end of therod string 18 is at a predetermined position. - The
control system 46 may modify a stroke extent of a member (e.g.,rod member 50,piston member 54, magnet 60) of theactuator 14, or a stroke extent of therod string 18 at surface or proximate adownhole pump 20, in response to the output of theflowmeter 102. - The
control system 46 may maintain a preselectedvelocity profile 74 of a member of theactuator 14, or of therod string 18 at surface or at adownhole pump 20, in response to the output of the flowmeter. - A well pumping
method 80 is also provided to the art by the above disclosure. In one example, themethod 80 can include reciprocably displacing arod string 18, continuously determining avelocity profile 74 of therod string 18, and modifying thevelocity profile 74 while therod string 18 reciprocably displaces, in response to an output of aflowmeter 102. - The modifying step can comprise changing a duration of the
velocity profile 74. The changing may be performed while therod string 18 reciprocably displaces. - The modifying step can comprise changing a position at which an actuator member velocity is zero, the position being detected based on the output of the
flowmeter 102. The changing may be performed while therod string 18 reciprocably displaces. - The modifying step may comprise changing a position at which the
rod string 18 velocity is zero at adownhole pump 20. The changing can comprise solving a wave equation in therod string 18. - The modifying step may comprise minimizing differences between the detected velocity profile and a preselected velocity profile. The modifying step may comprise maintaining acceleration of the
rod string 18 less than a preselected level. - Another well pumping method is disclosed above. In this example, the method comprises reciprocably displacing a
rod string 18 with anactuator 14, continuously determining displacement in response to an output of aflowmeter 102, and modifying reciprocating displacement of therod string 18 by theactuator 14, in response to the output of theflowmeter 102. - The determined displacement may be calibrated in response to an output of at least one
discrete position sensor 100. - The modifying step may comprise varying a periodic energy input to the
actuator 14 relative to the reciprocating displacement of therod string 18. The varying can comprise varying a duration of the energy input and/or varying a level of the energy input. - The modifying step may comprise varying a stroke extent. The varying can include displacing the stroke extent until either: a) the stroke extent is positioned at a preselected stroke extent, or b) the stroke extent has displaced a preselected distance.
- Although various examples have been described above, with each example having certain features, it should be understood that it is not necessary for a particular feature of one example to be used exclusively with that example. Instead, any of the features described above and/or depicted in the drawings can be combined with any of the examples, in addition to or in substitution for any of the other features of those examples. One example's features are not mutually exclusive to another example's features. Instead, the scope of this disclosure encompasses any combination of any of the features.
- Although each example described above includes a certain combination of features, it should be understood that it is not necessary for all features of an example to be used. Instead, any of the features described above can be used, without any other particular feature or features also being used.
- It should be understood that the various embodiments described herein may be utilized in various orientations, such as inclined, inverted, horizontal, vertical, etc., and in various configurations, without departing from the principles of this disclosure. The embodiments are described merely as examples of useful applications of the principles of the disclosure, which is not limited to any specific details of these embodiments.
- In the above description of the representative examples, directional terms (such as "above," "below," "upper," "lower," "raised," "lowered," etc.) are used for convenience in referring to the accompanying drawings. However, it should be clearly understood that the scope of this disclosure is not limited to any particular directions described herein.
- The terms "including," "includes," "comprising," "comprises," and similar terms are used in a non-limiting sense in this specification. For example, if a system, method, apparatus, device, etc., is described as "including" a certain feature or element, the system, method, apparatus, device, etc., can include that feature or element, and can also include other features or elements. Similarly, the term "comprises" is considered to mean "comprises, but is not limited to."
- Of course, a person skilled in the art would, upon a careful consideration of the above description of representative embodiments of the disclosure, readily appreciate that many modifications, additions, substitutions, deletions, and other changes may be made to the specific embodiments, and such changes are contemplated by the principles of this disclosure. For example, structures disclosed as being separately formed can, in other examples, be integrally formed and vice versa. Accordingly, the foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the scope of the invention being limited solely by the appended claims.
Claims (13)
- A well pumping system (10), comprising:an actuator (14) configured to reciprocably displace a rod string (18);a flowmeter (102) which measures flow of a fluid between a power source (12) and the actuator (14); anda control system (46) configured to modify reciprocal displacement of the rod string (18) by the actuator (14) by modifying a stroke extent of a member (50) of the actuator (14), in response to an output of the flowmeter (102) while well fluid is being pumped by the well pumping system (10).
- The well pumping system (10) of claim 1, further comprising at least one discrete position sensor (52) configured to detect when a member (50) of the actuator (14) or an upper end of the rod string (18) is at a predetermined position.
- The well pumping system (10) of claim 1, wherein the control system (46) is configured to modify a stroke extent of the rod string (18) at surface, in response to the output of the flowmeter (102).
- The well pumping system (10) of claim 1, wherein the control system (46) is configured to modify a stroke extent of the rod string (18) proximate a downhole pump (20), in response to the output of the flowmeter (102).
- The well pumping system (10) of claim 1, wherein the control system (46) is configured to maintain a preselected velocity profile of a member (50) of the actuator (14), in response to the output of the flowmeter (102).
- The well pumping system (10) of claim 1, wherein the control system (46) is configured to maintain a preselected velocity profile of the rod string (18) at surface, in response to the output of the flowmeter (102).
- The well pumping system (10) of claim 1, wherein the control system (46) is configured to maintain a preselected velocity profile of the rod string (18) proximate a downhole pump (20), in response to the output of the flowmeter (102).
- A well pumping method, comprising:reciprocably displacing a rod string (18) with an actuator (14);continuously determining displacement in response to an output of a flowmeter (102) which measures flow of a fluid between a power source (12) and the actuator (14); andmodifying reciprocating displacement of the rod string (18) by the actuator (14), in response to the output of the flowmeter (102), wherein said modifying comprises varying a stroke extent of a member (50) of the actuator (14) while well fluid is being pumped.
- The well pumping method of claim 8, wherein the determined displacement is calibrated in response to an output of at least one discrete position sensor (52).
- The well pumping method of claim 8, wherein the modifying comprises varying a periodic energy input to the actuator (14) relative to the reciprocating displacement of the rod string (18).
- The well pumping method of claim 8, wherein the varying comprises varying the stroke extent until either:a) the stroke extent is a preselected stroke extent, orb) the stroke extent has changed by a preselected amount.
- The well pumping method of claim 8, wherein the modifying comprises maintaining a preselected velocity profile of a member (50) of the actuator (14).
- The well pumping method of claim 8, wherein the modifying comprises maintaining a preselected velocity profile, during the reciprocating displacement of the rod string (18).
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US14/947,839 US20170146006A1 (en) | 2015-11-20 | 2015-11-20 | Operational control of wellsite pumping unit with continuous position sensing |
US14/991,253 US20170146007A1 (en) | 2015-11-20 | 2016-01-08 | Operational control of wellsite pumping unit with displacement determination |
Publications (2)
Publication Number | Publication Date |
---|---|
EP3170968A1 EP3170968A1 (en) | 2017-05-24 |
EP3170968B1 true EP3170968B1 (en) | 2019-10-30 |
Family
ID=57348606
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP16199698.8A Not-in-force EP3170968B1 (en) | 2015-11-20 | 2016-11-18 | Well pumping system and method |
Country Status (2)
Country | Link |
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US (1) | US20170146007A1 (en) |
EP (1) | EP3170968B1 (en) |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
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CA3013084C (en) | 2016-02-10 | 2024-01-16 | Dreco Energy Services Ulc | Anti-extrusion seal arrangement and ram-style blowout preventer |
BR112019001538B1 (en) | 2016-07-26 | 2023-05-09 | Dreco Energy Services Ulc | METHOD AND APPARATUS FOR REVERSIBLY MODIFYING A PRODUCTION WELL HEAD ASSEMBLY IN A WELL BORE SUBJECT TO INCREASED PRESSURES FROM UNDERGROUND FRACTURING OPERATIONS ADJACENT TO THE WELL HEAD ASSEMBLY |
WO2018129620A1 (en) | 2017-01-16 | 2018-07-19 | Dreco Energy Services Ulc | Multifunction blowout preventer |
US20190040696A1 (en) * | 2017-05-26 | 2019-02-07 | David MCADAM | Method and apparatus for rod alignment |
US10941628B2 (en) | 2017-09-25 | 2021-03-09 | Dreco Energy Services Ulc | Adjustable blowout preventer and methods of use |
US10648246B2 (en) | 2018-07-13 | 2020-05-12 | Norris Rods, Inc. | Gear rod rotator systems |
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Also Published As
Publication number | Publication date |
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US20170146007A1 (en) | 2017-05-25 |
EP3170968A1 (en) | 2017-05-24 |
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