Patent Grant
12037997
Not applicable.
This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present disclosure. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present disclosure. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.
The present disclosure relates to the field of hydrocarbon recovery operations. More specifically, the present invention relates to pumping systems for the production of hydrocarbon fluids, and to the optimization of operating cycles for a reciprocating downhole pump. Further still, the invention relates to a pumping system having an ultra-long stroke length.
In the drilling of oil and gas wells, a wellbore is formed using a drill bit that is urged downwardly at a lower end of a drill string. After drilling to a predetermined depth, the drill string and bit are removed and the wellbore is lined with a string of casing. An annular area is thus formed between the string of casing and the surrounding formation.
Particularly in a vertical wellbore, or the vertical section of a horizontal well, a cementing operation is conducted in order to fill or “squeeze” part or all of the annular area with cement. The combination of cement and casing strengthens the wellbore and facilitates the zonal isolation, and subsequent completion, of certain sections of potentially hydrocarbon-producing pay zones behind the casing.
In completing a wellbore, it is common for the drilling company to place a series of casing strings having progressively smaller outer diameters into the wellbore. These include a string of surface casing, at least one intermediate string of casing, and a production casing. The process of drilling and then cementing progressively smaller strings of casing is repeated until the well has reached total depth. In some instances, the final string of casing is a liner, that is, a string of casing that is not tied back to the surface. The final string of casing, referred to as a production casing, is also typically cemented into place.
To prepare the wellbore for the production of hydrocarbon fluids, a string of tubing is run into the casing. This tubing is referred to as a production tubing. A packer is set at a lower end of the production tubing to seal an annular area formed between the tubing and the surrounding strings of casing. The tubing then becomes a string of production pipe through which hydrocarbon fluids may be lifted.
In order to carry the hydrocarbon fluids to the surface, a pump may be placed at a lower end of the production tubing. This is known as “artificial lift.” In some cases, the pump may be an electrical submersible pump, or ESP. ESP's utilize a hermetically sealed motor that drives a multi-stage pump. The downside to ESP's is that an electrical power line is required to be run from the surface, down the wellbore, and to the pump. In addition, ESP's draw large amounts of power. If electrical connectivity is somehow lost along the power line, the ESP no longer works.
More conventionally, oil wells undergoing artificial lift use a downhole reciprocating plunger-type pump. The pump has one or more valves that capture fluid on a down stroke, and then lift the fluid on the upstroke. This is known as “positive displacement.” In some designs such as that disclosed in U.S. Pat. No. 7,445,435, the pump is able to both capture and lift fluid on each of the down stroke and the upstroke.
Conventional positive displacement pumps define a moving, or “traveling,” valve, that is reciprocated at the end of a “rod string.” The rod string comprises a series of long, thin joints of solid rods (referred to colloquially as sucker rods) that are typically threadedly connected through couplings. The rod string is attached to a pumping unit at the surface. The pumping unit causes the rod string to move up and down within the production tubing to incrementally lift production fluids from subsurface intervals to the surface.
In
The horse head 120 supports a polished rod 130. The horse head 120 and polished rod 130 are mechanically tethered by means of a harness system 135 (sometimes referred to as a “bridle”). Suitable packing is provided along the polished rod 130 to prevent production fluids from leaking out of the wellhead 110.
The polished rod 130 supports a plurality of so-called sucker rods 132 from the surface 150. Multiple sucker rod joints 132 extend down into the wellbore 170 in order to support the downhole pump (not shown). Each sucker rod is typically 25 to 35 feet in length, and resides within a string of production tubing 145. The production tubing 145, in turn, resides within strings of casing 125. It is understood that the rod string 132 may extend over 5,000 feet, or over 7,000 feet, from the surface 150.
In order to induce reciprocation of the horse head 120 and connected polished rod 130 (and sucker rods 132 and downhole pump), a prime mover 140 is provided. In the illustrative system 100 of
It is understood that the pumping system 100 of
Sucker rod pumping is the most widely used means for artificially lifting oil wells. Those of ordinary skill in the art will understand that, during reciprocation, the long sucker rod string undergoes tension and compression forces, creating strain along the metal or fiberglass sucker rod string. Strain waves travel at the acoustical velocity in the rod material at about 16,000 feet/second. These strain waves can be detected at the surface by means of a load cell, and converted into histograms. The histograms are presented, either physically or digitally, on so-called dynamometer cards. The dynamometer cards are then analyzed to understand downhole operating conditions.
The speed at which the rod string 132 and connected pump move up and down in the wellbore 170 may be controlled through a so-called pump-off controller.
In any instance, the process of cyclically lifting and lowering the rod string 132 and connected pump causes frictional wear between the rod string and the surrounding production tubing 145. Those of ordinary skill in the art will understand that wellbores are never perfectly vertical. The frictional engagement between the rod string and the production tubing can create holes in the tubing, particularly along areas of cork screw, which in turn leak into the annulus around the tubing. Some in the industry derisively refer to the rod string as a “hacksaw.”
Therefore, a need exists for a rod pumping system that provides for a longer stroke length, thereby reducing the number of stroke cycles required to produce the same amount of oil as a conventional pumping unit. This, in turn, reduces the frictional wear applied to the production tubing. Further, a need exists for such a pumping system that utilizes the mechanical advantage offered by sheaves, thereby increasing the efficiency of the pumping unit. Still further, a need exists for such a pumping system where movement of the sheaves and the connected polished rod can be stopped, started, or held in place at any given moment by the pump-off controller, or manually by an operator.
An oil well pumping unit is first provided herein. The oil well pumping unit is designed to move a polished rod up and down, cyclically, through a well head above a wellbore. A long string of sucker rods is connected to the polished rod, and moves up and down within the wellbore in response to movement of the polished rod. In addition, a so-called traveling valve is connected at the bottom of the sucker rod string, which is part of a downhole pump.
In one embodiment, the oil well pumping unit first comprises a horizontal support base. The horizontal support base is preferably fabricated from steel, and may comprise a metal frame. The horizontal support base may optionally be placed onto or secured to a cement pad. Preferably, the metal frame is bolted into the cement pad to form an integral support base system. In one aspect, the pad is mounted onto helical piers that extend into the ground.
The oil well pumping unit also includes a vertical support column. The vertical support column resides adjacent the horizontal support base at a generally transverse orientation. In one aspect, the vertical support column has a lower end that is affixed to the frame portion of the horizontal support base. Preferably, the horizontal support base and the vertical support column are connected by means of a hinged connection so that the vertical support column may be folded over onto the horizontal support base. This allows a service company to access the wellbore for workovers and other service without repositioning the horizontal support column away from the well. This also facilitates transport and storage of the pumping unit as the vertical support column may be very tall.
The vertical support column has a front face and a back face. The front face is designed to face towards the wellbore while the back face is away from the wellbore. Note that this is in contrast to known pumping units that use a structure positioned or extending directly over the wellbore.
The oil well pumping unit further comprises a standing sheave. The standing sheave is fixed proximate an upper end of the vertical support column. Preferably, the standing sheave comprises a pair of wheels located at the top of the vertical support column and sharing a common axle. Preferably, the upper end of the vertical support column comprises a crown. The crown supports an axle shared by the pair of wheels making up the standing sheave. Thus, the axle is rotationally connected to the crown.
In addition, the oil well pumping unit has at least one sheave configured to move up and down along the vertical support column. This sheave serves as a traveling sheave. Preferably, the traveling sheave also comprises a pair of wheels that also share a common axle. The traveling sheave resides and moves along the back face of the vertical support column. Preferably, each of the wheels of the standing sheave has a radius that is larger than a radius of each of the wheels of the traveling sheave.
The oil well pumping unit also includes a near-vertical linear actuator. The vertical linear actuator is preferably anchored along a bottom plate of the vertical support column and extends up the back face. The linear actuator has a distal end that moves cyclically away from and back towards the bottom plate.
In one aspect, the linear actuator comprises a hydraulic cylinder. The hydraulic cylinder is made up of a barrel and a reciprocating plunger, with the plunger being connected to a piston rod. Cyclical movement of the plunger and connected piston rod is imparted by pumping fluid, under pressure, into the barrel using a hydraulic pump. Alternatively, the linear actuator may be driven by a linear electric motor, an electrical roller screw drive.
In any embodiment, the linear actuator is designed to move the traveling sheave along the back face of the vertical support column, up and down. In one aspect, the upper end of the piston rod is operatively connected to an axle of the wheels that make up the traveling sheave.
The oil well pumping unit also includes a carrier bar. The carrier bar is configured to be attached to the polished rod along the front face of the vertical support column, such as through the use of a polished rod clamp.
The oil well pumping unit further includes at least two ropes. Preferably, these are wire ropes. Each of the wire ropes is connected at a first end to the carrier bar. The wire ropes are then wound over the standing sheave, and then wound under the traveling sheave. Preferably, a second end of the wire ropes is then pinned to an upper end of the vertical support column.
In operation, the cyclical movement of the linear actuator causes the traveling sheave to reciprocate up and down along the back face of the vertical support column. An upward movement of the traveling sheave produces a downstroke of the polished rod, while a downward movement of the traveling sheave produces an upstroke of the polished rod. As designed, the second end of the linear actuator remains in tension at all times during movement of the polished rod. As designed, the traveling sheave arrangement produces a 2:1 amplification of travel.
In a preferred arrangement, each of the polished rod, the axle of the traveling sheave and the axle of the standing sheave has a vertical center-line, with each center-line being offset from the other. The center-line of the traveling sheave is proximate the back face of the vertical support column, while the center-line of the polished rod is over the wellbore. The center-line of the standing sheave is somewhere in between, and along the vertical support column.
In a preferred embodiment, the oil well pumping unit also includes a controller. The controller is programmed to control movement of the linear actuator by (i) sending signals to start and stop movement of the linear actuator, and (ii) sending signals to control a speed of the upstroke of the polished rod, a speed of the downstroke of the polished rod, or both. In one aspect, the controller is configured to control the downstroke speed of the polished rod within established minimum and maximum downstroke speeds, and to control the upstroke speed of the polished rod within established minimum and maximum upstroke speeds. The controller may also adjust stroke length within defined limits.
In one embodiment, the controller autonomously detects both compressible and non-compressible pump fillage plus leakage rates downhole. By using a fluid pressure transducer, the controller is able to detect load changes as seen by the polished rod as it reciprocates above the wellbore. The system detects both polished rod position and supported load throughout the entirety of stroke travel, using sensors for pump optimization. In one aspect, a position sensor is associated with the polished rod or, optionally, with a vertical actuator. The controller is able to move the traveling valve to a position of close proximity to the standing valve in the wellbore on the downstroke, thereby improving the capture of fluids.
A method of producing oil using a surface rod pumping unit is also provided. In one aspect, the method first comprises providing a surface rod pumping unit. The surface rod pumping unit may be designed in accordance with the oil well pumping unit described above in its various embodiments. For example, the surface rod pumping unit may comprise:
Preferably, the standing sheave comprises a pair of wheels rotationally supported at the upper end of the vertical support column, while the traveling sheave also comprises a pair of wheels. The pair of wheels making up the standing sheave rotate together about an axis of rotation through the vertical center-line of the standing sheave, while the pair of wheels making up the traveling sheave rotate together about an axis of rotation through the vertical center-line of the traveling sheave. These two center-lines are offset from one another, providing load balancing along the vertical support column.
Upward movement of the linear actuator causes the traveling sheave to travel to an upper end of the vertical support column, defining a raised position. In one aspect, when the traveling sheave is in its raised position, the wire ropes form an angle that is between 4° and 8° relative to a center-line of the vertical support column. Downward movement of the linear actuator causes the traveling sheave to travel to a lower end of the vertical support column, defining a lowered position. In one aspect, when the traveling sheave is in its lowered position, the wire ropes form an angle that is between 1° and 4° relative to the center-line of the vertical support column.
Of interest, the second end of the linear actuator remains in tension at all times during movement of the traveling sheave and operatively connected polished rod. Preferably, each of the at least two ropes is a wire rope that has a second end opposite the first end. The second end is pinned to the vertical support column proximate an upper end of the vertical support column.
The method also includes cycling the linear actuator. In this arrangement, cycling the linear actuator causes the traveling sheave to reciprocate up and down along the back face of the vertical support column such that upward movement of the traveling sheave produces a downstroke of the polished rod, while downward movement of the traveling sheave produces an upstroke of the polished rod. Preferably, the distance of travel of the polished rod in each direction is at least 400 inches and, more preferably, at least 480 inches.
So that the manner in which the present inventions can be better understood, certain illustrations, charts and/or flow charts are appended hereto. It is to be noted, however, that the drawings illustrate only selected embodiments of the inventions and are therefore not to be considered limiting of scope, for the inventions may admit to other equally effective embodiments and applications.
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For purposes of the present application, it will be understood that the term “hydrocarbon” refers to an organic compound that includes primarily, if not exclusively, the elements hydrogen and carbon. Hydrocarbons may also include other elements, such as, but not limited to, halogens, metallic elements, nitrogen, oxygen, and/or sulfur.
As used herein, the term “hydrocarbon fluids” refers to a hydrocarbon or mixtures of hydrocarbons that are gases or liquids. For example, hydrocarbon fluids may include a hydrocarbon or mixtures of hydrocarbons that are gases or liquids at formation conditions or at surface conditions. Hydrocarbon fluids may include, for example, oil, natural gas, coalbed methane, shale oil, pyrolysis oil, pyrolysis gas, a pyrolysis product of coal, and other hydrocarbons that are in a gaseous or liquid state, or combination thereof.
As used herein, the term “wellbore fluids” means water, hydrocarbon fluids, formation fluids, or any other fluids that may be within a wellbore during a production operation. Wellbore fluids may include a weighting agent that is residual from drilling mud.
As used herein, the term “wellbore” refers to a hole in the subsurface made by drilling or insertion of a conduit into the subsurface. A wellbore may have a substantially circular cross section. The term “well,” when referring to an opening in the formation, may be used interchangeably with the term “wellbore.”
As used herein, the term “hydraulic pressure” when used in connection with the movement of a piston rod includes hydraulic pressure produced by a hydraulic pump, including changes in pressurized fluid flow rate.
The novel characteristic of the embodiments of the present application are set forth in the appended claims. However, the embodiments themselves and further objectives and advantages thereof, will best be understood by reference to the following detailed description when read in conjunction with the accompanying drawings, wherein:
An oil well pumping unit is provided. The oil well pumping unit is designed to move a polished rod up and down, cyclically, above a wellbore. A long string of sucker rods is operatively connected to the polished rod, and moves up and down within the wellbore in response to movement of the polished rod. For this reason, the pumping unit is referred to herein as a rod pumping unit.
It is understood that a downhole pump is attached to a lower end of the sucker rod string. The downhole pump represents a so-called traveling valve and plunger. The traveling valve operates in conjunction with a standing valve, which is secured within the production tubing downhole. Typically, the standing valve frictionally resides within a seating nipple (not shown).
The rod pumping unit 200 first comprises a horizontal support base 210. The horizontal support base 210 defines an elongated metal frame (seen at 213 in
The concrete pad 211 is preferably between 40 and 50 feet in length, though a smaller form could be employed where the concrete pad 211 is secured in the ground using pilings. The frame 213 is between 35 and 45 feet in length, in a preferred embodiment.
The frame 213 comprises a proximal end 212 and a distal end 214. A pair of brackets 217, 218 are welded (or otherwise secured onto) the frame 213. The first bracket 217 resides intermediate the proximal 212 and distal 214 ends of the frame 213, while the second bracket 218 resides along the proximal end 212 of the frame 213. The frame 213 and its brackets 217, 218 are preferably fabricated from steel.
The rod pumping unit 200 also includes a vertical support column 220. The vertical support column 220 resides adjacent the horizontal support base 210 at a generally transverse orientation. In one aspect, the vertical support column 220 extends 45 feet above the ground, or 65 feet above the ground, or even 100 feet above the ground, to accommodate the long polished rod 265. In one aspect, the polished rod 265 is carried through a 40-foot travel.
The vertical support column 220 also has a proximal end 222 and a distal end 224. The vertical support column 220 may be a so-called I-Beam (or, optionally, a W-Beam or other fabricated beam) having a front face 310 and a back face 320. The front face 310 faces towards the wellbore 170 while the back face 320 is away from the wellbore 170. Note that this is in contrast to known pumping units that use a vertical structure positioned directly over the wellbore and using bridles or belts.
The vertical support column 220 is a fixed, rigid member that supports the dead weight being lifted and lowered. In one aspect, the vertical support column 220 is fabricated using a combination of plate, bar, and angle gusset material to stiffen side members of the support column 220 so as to prevent buckling.
The proximal end 222 of the vertical support column 220 defines a bottom plate 227. The bottom plate 227 is essentially the bottom of the I-Beam or other structure making up the vertical support column 220. When the vertical support column 220 is in its raised position, the bottom plate 227 gravitationally rests on the cement pad 211.
The vertical support column 220 also includes a pair of base plates 228. The base plates 228 are welded onto the bottom plate 227 along the major axis of the vertical support column 220. The base plates 228 are positioned on opposing sides of the beam making up the vertical support column 220, and are transverse to the bottom plate 227. Beneficially, the base plates 228 serve to stiffen the bottom plate 227.
Of interest, the vertical support column 220 may be connected to the horizontal support base 210 by means of a pin 216. More specifically, a pair of pins 216 is used, as shown in
The rod pumping unit 200 also includes a crown 290. The crown 290 defines a metal plate (or plates) that extends up from the distal end 224 of the vertical support column 220. The crown is used to support an axle 235. In one arrangement, the axle 235 turns along a horizontal axis at the top of the crown 290. In a preferred embodiment, the axle 235 is held fixed while shaft bearings (not shown) rotate about the axle 235. Of course, an arrangement could be provided where the axle 235 turns within a fixed bearing housing.
The rod pumping unit 200 further includes a standing sheave 230. The standing sheave 230 defines a wheel having a central opening. The opening receives the axle 235. Preferably, the wheel making up the standing sheave 230 defines a metal plate, or a pair of metal plates, having a plurality of spokes 236. The spokes 236 are best seen in the perspective views of
In a preferred embodiment, the standing sheave 230 comprises a pair of wheels. These are indicated at 232 and 234 in
The rod pumping unit 200 also includes a traveling sheave 240. The traveling sheave 240 also defines a wheel having a central opening. The opening receives an axle 245 and also includes shaft bearings. Preferably, the wheel making up the traveling sheave 240 also defines a metal plate, or a pair of metal plates, having a plurality of spokes 246. The spokes 246 are best seen in the perspective view of
In a preferred embodiment, the traveling sheave 240 comprises a pair of wheels. These are indicated at 242 and 244 in
As the names imply, the standing sheave 230 remains in a stationary position relative to the concrete pad 211 during operation of the rod pumping unit 200. The only motion is the rotational movement of the wheels 232, 234 about (or with) the axle 235. At the same time, support rollers associated with the traveling sheave 240 roll up and down relative to the concrete pad 211. As will be explained, vertical movement of the wheels 242, 244 making up the traveling sheave 240 cause a polished rod 265 to reciprocate up and down along the front face 310 of the vertical support column 220.
To help support the vertical support column 220 relative to the concrete pad 211, a collection of axial support rods 226 (or stiff-legs) is provided. In the arrangement of
The axial support rods 226 add rigidity to the support column 220 and spread the supporting load to a wider portion of the bottom plate 227. As shown in
The various items of hardware described above, including the crown 290, the vertical support column 220, and the support rods 226 may be pre-welded together, or may be of a modular construction. In the latter instance, components of the rod pumping unit 200 may be assembled at the well site, after transport. The present inventions are not limited by how the rod pumping unit 200 is assembled or disassembled unless so stated in the claims.
The rod pumping unit 200 also includes a linear actuator 250. The linear actuator 250 resides along the back face 320 of the vertical support column 220 in a vertical orientation. The linear actuator 250 has a proximal end 252 that is anchored (or otherwise operatively connected to) to the bottom plate 227. Preferably, the proximal end 252 defines a hydraulic barrel that is pinned to the bottom plate 227. In a preferred embodiment, the linear actuator 250 is positioned to have a nearly parallel mounting orientation to the support column with a slight angle biased into the support column 220, perhaps being a one- to four-degree lean into the vertical support column 220. This helps provide stability to the linear actuator 250 as it pushes the traveling sheave 240 up the back face 320 of the vertical support column 220.
The linear actuator 250 also includes a distal end 254. The distal end 254 preferably defines a telescoping piston rod that moves in and out of the barrel 252. The piston rod 254 is pinned to the axle 245 of the traveling sheave 240. The pinned connection is further described below in connection with
In one aspect, the barrel 252 of the linear actuator 250 is between 20 and 40 feet in length, while the piston rod 254 is between 20 and 50 feet in length. These dimensions are a matter of designer's choice, depending on the ultimate length of the polished rod 265 used and ultimately the desired pump displacement downhole.
In operation, the piston rod 254 moves in and out of the barrel 252 cyclically. This cyclical movement of the piston rod 254 (and connected traveling sheave 240) is imparted in response to a volume of pressurized hydraulic fluid that is forced into or allowed to be released from the barrel 252 by a hydraulic pump (shown at 340 in
The rod pumping unit 200 is operated through a master control panel 400. The control panel 400 includes a control box 450. The control box 450 houses electronics such as a master controller 410, manual on-off switches 420 and a back-up battery 430. The control box 450 is optionally supported by a support pole 455. The support pole 455 is secured to a cement pad (not shown) or is otherwise cemented into position proximate to the rod pumping unit 200. As an alternate arrangement, the support pole 455 may be mounted onto or otherwise secured to a counter-weight powerhouse module (seen at 275).
The controller 410 regulates the energy flow of rotational torque thru the prime mover 330 into and out of the hydraulic pump (shown at 950 in
The controller 410 may monitor the input voltage supply to detect low-voltage events indicative of a brown-out. The controller 410 also regulates the hydraulic pump volumetric displacement (flow volume setting) as well as limiting minimum and maximum allowable working pressures on both sides of the hydraulic pump 340 working ports A and B. Beneficially, the controller 410 also acts as the rod pump “pump off controller” by detecting, storing and averaging actual weight transfer position. The controller 410 further detects, stores, and averages data related to changes in position and rates of change of weight transfer which occur during the rod pumping process.
The controller 410 may interface and use an existing off-the-shelf pump-off controller in producing downhole dynamometer cards. Such controllers are available from Delta Electronics, Inc. of Taipei City Taiwan (sold domestically through Delta Americas); Redhead Artificial Lift Ltd. of Lloydmaster, Canada; Petrolog Automation, Inc. of San Antonio, Texas; Weatherford Technology Holdings, LLC; and several others.
The controller 410 includes circuitry (not shown) that resides within a sealed housing for implementing a control algorithm. The algorithm varies the pump cycle rate of the downhole positive displacement pump located at the moving end of the polished rod string 132 in response to the amount of fluid produced from the pump and the position of the master fluid valve. In one aspect, the controller 410 increases the pumping cycle speed of strokes-per-minute in user-defined steps. For example, if a pump appears to have low pump fillage on a previous downstroke or average of previous downstrokes (as measured by the load cell or a hydraulic fluid pressure transducer, and polished rod position), described as weight transfer position, then a signal will be generated to either not lift the polished rod as far on the proceeding pump cycle or average of pump cycles, or to decrease pump speed (pump cycles per minute) or dwelling at the top of the next pump intake stroke in any combination. This allows additional time to fill the downhole pump during its intake stroke. This decrease in pump speed reduces the pump output, which in turn should increase the pump fillage percentage of volume as it provides both additional time for the well annulus to fill the downhole pump or by decreasing the downhole pump's effective cubic inch displacement per running minute.
When a decrease in speed does not produce a proportional increase in pump fillage, the rod pump controller is able to decrease the total travel distance that the traveling valve and plunger are lifted. This causes a decrease in volumetric pump displacement at the bottom of the well and adds time in the pump intake stroke by dwelling at the top of the pump intake stroke. The controller 410 may iteratively slow the upstroke speed until the desired pump fillage is achieved. Reciprocally, if a pump appears to have complete pump fillage on a downstroke (as measured by the load cell or other means) by detecting weight transfer position, then a signal may be generated to increase pump speed. This enables the pumping system 200 to capture more wellbore fluids each stroke.
The controller 410 continually evaluates the pump fillage, generating speed increase/decrease signals, total linear travel distance/volumetric pump displacement per pump stroke and time dwell increased or decreased at the top of each pump intake stroke movement as needed to keep the pump fillage within desired set-points.
Preferably, the controller 410 is capable of starting and stopping the movement of the traveling sheave 240 at any point of travel along the vertical support column 220. The controller 410 may also hold the movement of the traveling sheave 240 by stopping movement of the linear vertical actuator 250 in place. Preferably, the controller 410 is further capable of regulating maximum velocity and motion profiles of movement including acceleration and deceleration in both directions and limiting the minimum and maximum amount of force generated by the vertical linear actuator 250. Further, the controller 410 can hold the traveling sheave 240 at any given position while supporting the instantaneous load. In one aspect, this can be done using a remote control device that sends signals to the controller 410 through wireless signals.
In another aspect, this may be done autonomously such as when detecting pump fillage or when testing for traveling valve assembly leakage or standing valve leakage. Traveling valve assembly leakage testing includes the autonomous stopping and holding of the polished rod 265 during an upstroke. Alternatively, traveling valve assembly leakage testing may include the autonomous determination of a rate of change in the polished rod load, or the autonomous determination of a traveling valve leakage factor. Standing valve leakage testing includes the autonomous stopping and holding of the polished rod during a down stroke after weight transfer, the autonomous determination of a rate of change in the polished rod load, and the autonomous determination of a standing valve leakage factor. U.S. Pat. No. 8,844,626 describes a controlled system for the autonomous stopping and holding of the polished rod 265. The '626 patent is incorporated herein in its entirety.
Because wheels 242, 244 are used to move the polished rod 265, the controller 410 can effectuate accelerating and decelerating of the traveling sheave 240 speed in a smooth manner. Through the knowledge of weight transfer position, rate of change during weight transfer position in the downhole pump, knowledge of current pump cycle and of previous pump cycles, the controller 410 is able to optimize pump performance. This optimization can occur in various ways such as by lifting the polished rod string assembly and fluid column load only as far as required as compared to liquid fillage volume and gas compression travel of the downhole pump. Having the ability to vary the bottom of stroke turn around position can increase or decrease pump compression ratio. Stopping and dwelling at the top of the stroke for a brief instance allows additional downhole pump fillage across the standing valve.
Reciprocally, the controller 410 can slow the speed of the downhole pump as the polished rod 265 reaches the point of previous weight transfer position. This allows weight transfer to occur with reduced fluid pound. As an additional feature of the rod pumping unit 200 and its controller 410, energy regeneration can be acquired during the downstroke. This is provided by spinning an electric motor shaft residing within the counter-weight powerhouse module 275. The electric motor shaft is spun faster than its synchronous speed, thereby generating electrical energy during the downstroke of the polished rod 265.
It is again observed that the pumping system 200 is biased in the downstroke position. When the counterweight powerhouse module 275 is used, the electrical energy may optionally be generated from the falling polished rod string and fluid weight by virtue of the pressurized fluid stream passing through the main pump (seen at 950 in
Returning to
As noted above, the rod pumping unit 200 also includes a plurality of wire ropes 255. Each wire rope 255 has a proximal end 251 and a distal end 259. The proximal end 251 is secured to the carrier bar 260. This is best seen in
Each wire rope 255 is wound over the standing sheave 230 and under the traveling sheave 340. In a preferred arrangement, the standing sheave 230 comprises a pair of wheels 232, 234, while the traveling sheave 240 also comprises a pair of wheels 242, 244. Each wheel 232, 234 has grooves 238 for receiving a respective wire rope 255. Similarly, each wheel 242, 244 has grooves 248 for receiving a respective wire rope 255.
Preferably, the standing sheave 230 has three separate grooves 238 for receiving three respective wire ropes 255. At the same time, and preferably, the traveling sheave 240 has three separate grooves 238 for receiving three respective wire ropes 255. Of interest, because of the weight of the carrier bar 260, polished rod 265 and supported rod string 132 and fluid load, the wire ropes 255 remain in tension at all times. Of even greater interest, the piston rod 254 of the vertical linear actuator 250 remains in tension at all times as it supports the carrier bar 260, the polished rod 265, the rod string 132 and the wellbore fluid load (together, the “polished rod string assembly”).
The pair of traveling sheaves 242, 244 produces a 2:1 wire rope and sheave mechanical advantage arrangement. The mechanical advantage is provided through the tension force used while lifting the polished rod string assembly. This may be referred to as a “travel amplifier.” By having one end 259 of the multiple ropes 255 anchored to the support column 220, the proximal end 251 of the multiple ropes 255 all move twice the distance. Thus, one foot of mechanism travel produces two feet of wire rope travel, which translates to two feet of polished rod travel.
In a preferred arrangement, each of the wire ropes 255 is identical in length and in construction. Each wire rope 255 may be fabricated from small wires woven into strands, which are then woven into a single rope. The individual wires may be of lower tensile strength, giving them better flexibility. The wire ropes 255 may optionally be pre-stretched before operation of the rod pumping unit 200.
It is also observed that the polished rod 265 reciprocates vertically, through the stuffing box 268. The vertical line of movement of the polished rod 265 is also offset from the center-lines CLSS, CLTS, CLSC.
In a preferred arrangement, each of the wheels 232, 234 making up the standing sheave 230 has a radius that is larger than a radius of each of the wheels 242, 244 making up the traveling sheave 240. The radii are tuned to create a relative angle between the wire ropes 255 and the center-line CLSC of the vertical support column 220. In the view of
Keeping these two angles at essentially the same value provides load balancing along the vertical support column 220 CLSC. This, in turn, minimizes the side load exerted into the support column 220 while the traveling sheave wheels 242, 244 move through their range of motion from top to bottom, and back up.
In operation, the cyclical movement of the linear actuator 250 causes the traveling sheave 240 to reciprocate up and down along the vertical support column 220. An upward movement of the wheels 242, 244 of the traveling sheave 240 produces a downstroke of the polished rod 265, while a downward movement of the wheels 242, 244 of the traveling sheave 240 produces an upstroke of the polished rod 265. The radius of the wheels 242, 244 and the location of the pins 291 along the crown 290 are design features that provide side load balancing during operation of the rod pumping unit 200.
A key to minimizing the side load exerted into the vertical support column 220 while the wheels 242, 244 of the traveling sheave 240 move throughout their range of motion from top to bottom of total distance traveled is the unique placement and balanced angles of wire rope entrance and departure to the traveling sheave pair. In addition, the location of the anchor pivot point 291 is tuned in relation to the two sheave pairs of different centerlines CLSS, CLTS and outside diameters during operation.
In one aspect:
each rope 255 has a first angle of deviation defined by the angle of the rope 255 as it approaches the traveling sheave 240 relative to the center-line CLSC of the vertical support column 220;
each rope 255 also has a second angle of deviation defined by the angle of the rope 255 as it exits the traveling sheave 240 relative to the center-line CLSC of the vertical support column 220; and the angles of deviation for the two ropes are within 10 degrees of each other, and more preferably within 2 degrees of each other, at all times.
Thus, in
It is noted that during vertical motion of the traveling sheave wheels 242, 244, the wire rope 255 entrance and departure angles vary, but at the same time remain nearly equal—equal but opposite to each other—to provide the desired load balancing. Because the angles are near-equivalent, the resultant force differential caused from the offset rotating center-lines CLSS, CLTS, and different outside diameters of the stationary sheave wheels 232, 234 versus the traveling sheave wheels 242, 244 in relation to the center-line of the support column CLSC is controlled. This load balancing is effectuated even though the lifting loads imposed on the wire ropes 255 are extremely high.
Because of the wire rope working angles and free rope operating distances between both sheave pair sets, the resulting side load force transferred into the support column 220 also varies and is directly correlated to the traveling sheave pair operating position. The greatest net effective side load force (least balanced) is with the traveling sheave wheels 242, 244 in their lowest position.
As observed above, the piston rod 254 and operatively connected wire ropes 255 and polished rod 265 remain in tension at all times during operation. This is due to the weight of the rod string 132 connected to the polished rod 265. The result is that the rod pumping unit 200 is gravitationally biased in its downstroke position. Thus, the work required to move the traveling sheave 240 resides in pulling the traveling sheave 240 back down the back side 320 of the vertical support column 220, thereby pulling the rod string assembly out of the wellbore.
To provide this energy, and as an optional feature, the rod pumping unit 200 may include a counter-weight system 270. The counter-weight system 270 is seen in each of
The counter-weight system 270 also includes a counter-weight 272. In the arrangement of
Each of the plates 272 may weigh between 1,000 pounds and 30,000 pounds. The selected amounts will depend on the weight of the polished rod 265, the rod string 132, the connected traveling valve, and the fluid being lifted. The weight of the fluid, in turn, is dependent on the diameter of the downhole pump assembly, the length of the rod and tubing string within wellbore, and the density of the fluids being produced.
A pair of support braces (referred to as stiff-legs) 276 may provide lateral support to the working beam 274. The stiff-legs 276 are secured at proximal ends to a powerhouse module 275. The stiff-legs 276 are secured at distal ends to the working beam 274.
It should be mentioned here that the powerhouse module 275 is an optional feature used to house various components of the rod pumping unit 200. These may include the main prime mover and hydraulic pumps, high voltage motor controls, the control panel box 400 and its 24 volt dc control system, plus the hydraulic fluid pumping system 300 as shown in
In operation, the counter-weight plates 272 move up the working beam 274 when the polished rod 265 and connected rod string 132 move down into the wellbore 170. The weight of the polished rod 265 and connected rod string 132 and fluid loads pull the traveling sheave 240 up the vertical support column 220. This is before the weight transfer takes place downhole. In this raised position, the piston rod 254 of the linear actuator 250 extends out of the barrel 252. This is shown in
It is once again seen that six wire ropes 255 are wound over the wheels 232, 242, 234, 244. The ropes 255 are pinned at their distal ends 259 using pin 291. It is understood that pin 291 receives three wire ropes 255 on one side of the crown 290, and then three ropes 255 on the opposing side of the crown 290.
The pin 291 holding the distal end 259 of the wire ropes 255 on one side of the crown 290 is seen. Note again that a relative angle is provided between the wire ropes 255 and the center-line CLSC of the vertical support column 220. In this position, the relative angle of the wire ropes 255 is about 1.5 degrees.
It is noted that the angle of the wire rope 251 between the standing sheave 230 and the carrier bar 260 is always 0 degrees relative to CLSC.
Additional features of the rod pumping unit 200 are also more readily visible in
In the arrangement of
It can be seen that a box 241 connects the piston rod 252 to the axle 245. The box 241 has a first opening (not visible) that receives the axle 245. The bearing wheels 249 reside on opposing ends of the box 241. The box 241 has a second opening 247 that receives a pre-threaded flange 243. The flange 243 is threaded onto an end of the piston rod 252 using a male x female thread connection, with the smaller bolts being threaded in and tightened down onto the flange 243 using a ratchet 201. A hardened flat washer (not shown) may be placed between the threaded connection and the flange 243. As the bolts are threaded into place, the hardened flat washer is pushed down. This serves to pre-load the male threads associated with the piston rod 252 and the female pre-threaded flange 243.
Other features of note that are well-visible in
Using the same crane, the counter-weight system 270 with its powerhouse 275 are lifted onto a concrete base 271. The counter-weight system 270 is also positioned and anchored adjacent the horizontal support base 210.
Once the counter-weight powerhouse system 270 is in position and anchored to its concrete base 271, the crane pivots the working beam 274 to its vertical working position. Both stiff legs 276 are swung into place and are bolted tightly into position. The crane hook is released, and is now ready for the counter-weight plates 272. The crane lifts and swings the plates 272 into position, with the field technician providing final guidance of each plate 272 onto the working beam 274. The plates 272 are then pinned into place so that they do not fall away from the axle of the working beam 274.
Rotation of the vertical support column 220 of the rod pumping unit 200 over onto the horizontal support base 210 is by means of pin 216. The horizontal cylinder 282 is used to raise the large vertical support column 220 so that the front face 310 faces a wellhead 110. Once both modules, that is, the rod pumping unit 200 and the counter-weight powerhouse system 270, are in place, the modules are fluidly connected together through pipes and flexible conductors (or hoses).
The carrier bar 260 is secured onto the polished rod 265 using polished rod clamps securely fastened to the polished rod 265 above the carrier bar 260. This will require lowing the carrier bar 260.
Of interest, the controller 410 allows the operator to manipulate the position of the carrier bar 260. Conventional oilfield practice on adjusting pump spacing requires the use of two sets of polished rod clamps or means of holding the polished rod in place as the top clamp position is measured and re-positioned in correct location. Once the polished rod is able to be moved by the surface unit, another set of rod clamps is secured below the carrier bar. The carrier bar is then lowered either to contact the well head or approved load support device able to hold the weight of the polished rod, thus unweighting the carrier bar. The top rod clamp(s) are loosened, the carrier bar is moved up or down on the polished rod, then the top rod clamps are tightened. This setting changes the position of the traveling valve in relation to the standing valve at full bottom of stroke.
Once the carrier bar 260 is connected to the polished rod 265 in the right position, the oilfield operator has the ability to start, stop and hold the position of the carrier bar 260 and connected polished rod string 265 at any position. This may be done through a remote control unit that communicates with the controller 410 through wireless signals or that is tethered with a physical cable connection.
Of interest,
After a period of production, the vertical support column 220 may be rotated back onto the horizontal support base 210. This allows a working crew to access the wellhead 170. This also facilitates transportation of the rod pumping unit 200 off of the cement pad 211 and to another well, or to a storage yard if desired.
Of interest, a tension strap 261 may be used in transport, and anytime well workover is demanded, to secure the wire ropes 255 and the carrier bar 260 in place. Specifically, the strap 261 has a proximal end 262 secured to the vertical support column 220 and a distal end secured to the carrier bar 260. In the transport position, the traveling sheave 240 is moved to its lowered position and secured in place with mechanical connections. This is shown best in
Once the tension strap 261 is connected to the carrier bar 260, it is lifted to approximately 85% of its raised position. This puts tension into the straps 261, keeping the wire ropes 255 in place. This is done by lowering traveling sheave wheels 242, 244 along the back side 320 of the vertical support column 220. This reduces the center of gravity of the vertical support column 220 making it safer to pivot.
To assist in the controlled rotation of the vertical support column 220, either up or down, a near-horizontal actuator 280 may be provided. The horizontal actuator 280 resides along and on top of the horizontal support base 210. The horizontal actuator 280 has a proximal end 282 that is operatively connected to the frame 213 of the horizontal support base 210. Preferably, the proximal end 282 defines a hydraulic barrel. The proximal end 282 is connected to a bracket 217 by means of a pin 281. In this way, a hinged connection is formed. (Again, some may refer to this as a rod-eye clevis arrangement.) Alternatively, the cylinder 282 may mounted using a front trunnion style of cylinder mounting to reduce piston rod loading stress and strain.
The horizontal actuator 280 also includes a distal end 284. The distal end 284 preferably defines a telescoping rod, or piston rod that extends and retracts out of the barrel 282. The piston rod 284 is pinned to the base plates 228 by pin 288. Pin 288 is best seen in
Hydraulic fluid resides in the barrel 282. Fluid may be pumped under pressure against a plunger 287 (shown in
In the view of
As noted above, a separate plunger 257 is also shown in
Movement of each of pistons 257, 287 may be by means of the application of hydraulic fluid under pressure.
In the arrangement of
Also as discussed above, the vertical support column 220 is raised and lowered at least in part by motion of the horizontal actuator 280. The hydraulic actuator is operated within the open loop hydraulic system. The horizontal actuator 280 is also shown in
Components of the hydraulic fluid pumping system 300 primarily reside within the powerhouse module 275. The powerhouse module 275, in turn, is supported on the cement pad 371. In the view of
The hydraulic fluid pumping system 300 first includes a prime mover 330. The prime mover 330 provides power to the fluid pump 340. The prime mover 330 may be a gasoline engine, a diesel engine, or other internal combustion engine. More preferably, the prime mover 330 is an electric motor. The electric motor 330 may receive three-phase power from the grid, or may be powered by a so-called industrial gen-set. When the prime mover 330 is started, it activates the fluid pump 340. Changing the operating speed of the prime mover 330 will vary the output of the pump 340. Alternatively, different types of control such as regulating actual pump displacement and direction of fluid flow or valving can be used to vary the hydraulic output flow and direction with a fixed RPM in the pump 340.
The hydraulic fluid pumping system 300 also includes the fluid pump 340. In one aspect, the pump 340 serves to pump fluid into oil lines 365 and 368. Oil line 365 is used to move the piston rod 254 of the vertical linear actuator 250, while oil line 368 is used to move the piston rod 284 of the horizontal linear actuator 280. Of course, it is understood that a separate hydraulic pump or other power system could be used to move the piston rod 284 of the horizontal linear actuator 280. It is also understood that the horizontal linear actuator 280 could be part of a closed loop hydraulic system as is shown in the more preferred arrangement of
In the embodiment shown in
In the arrangement of
The hydraulic fluid pumping system 300 further includes a master fluid valve 350. The master fluid valve 350 is controlled by the controller 410. In the arrangement of
The controller (such as controller 410 of
The controller 410 may also adjust the stroke length of the polished rod within defined limits. This allows an operator to select a desired pump size, or to limit stroke length if pump fillage is only partial.
The hydraulic fluid pumping system 300 also includes a pair of return lines 355, 358. The return lines 355, 358 are essentially vent lines. The return lines 355, 358 receive air and any leaked oil during operation of the rods 254, 284. Return line 355 returns fluid into the valve stack 350 from below the plunger 257. At the same time, return line 358 returns fluid back to the valve stack 350 from above the plunger 287.
The hydraulic fluid pumping system 300 also includes a fluid reservoir 360. The reservoir 360 holds the working fluid for the system 300. Preferably, the fluid is a clean oil. Oil lines 365, 368 deliver fluid from the fluid reservoir 360 to the barrel 352 and the barrel 382, respectively as an open loop system.
In operation, the pump 340 causes oil to be moved from the fluid reservoir 360, through oil line 365, and into an annular area within the barrel 352. The oil acts against the plunger 257, causing the plunger 257 and connected piston rod 254 to be lowered. This accomplishes the upstroke of the polished rod 265 and the mechanically connected rod string 132 and downhole pump. To effectuate the downstroke, oil is vented back through vent line 355 and into the fluid reservoir 360 (or, optionally, into a barrel associated with the counter-weight system 370. Rate of descent of the polished rod assembly may again be controlled through the valve stack 350 through settings provided by controller 410.
In each of
Also shown is an oil line OS. The oil line OS is in fluid communication with the barrel 252 by means of an oil port PS. In the view of
The second linear actuator is linear actuator 970. This vertical linear actuator is used to move the counterweight plates 272 up and down along the working beam pole (shown at 274 in various figures). Vertical linear actuator 970 also includes a barrel 972, a plunger 977 and a piston rod 974. In one aspect, the piston rod 974 is offset within the barrel 972 in accordance with the hydraulic lift system taught in U.S. Pat. No. 8,083,499, although a conventional centered design may also be employed.
Also shown in
It is observed that for the barrel 252 associated with the vertical linear actuator 250, the oil line port PS is located above the plunger 257. In contrast, for the barrel 972 associated with the vertical linear actuator 950, the oil line port PP is located below the plunger 977. The result is that movement of oil from barrel 972 into barrel 252 causes both of plungers 257 and 977 to move down together.
By virtue of the placement of the ports PP and PS and the movement of fluid through the hydraulic pump 950, the two plungers 257, 977 move down together. The result in
The hydraulic fluid pumping system 900 also includes the powerhouse module 275. The powerhouse module 275 houses a hydraulic pump 950. The hydraulic pump 950 moves oil in two different directions. The first direction is shown in
In
Oil moves through oil line OS and into the hydraulic pump 950. From there, oil is pumped into the barrel 972 associated with the counter-weight plates 272. Oil then moves through oil line OP, through port PP, and into the barrel 972. Increased pressure below the plunger 977 will move the plunger 977 and connected piston rod 974 upward. This, in turn, moves the counter-weight plates 272 upward in accordance with arrow “P.”
The result of the pumping of oil in
The energy to pump oil through oil lines OP and OS is provided by a prime mover 330. The prime mover 330 provides rotational torque energy to the pump shaft. The prime mover 330 is preferably an electric motor, although it may alternatively be a diesel engine or may run off of natural gas or natural gas liquids. When the prime mover 330 is an electric motor, energy is acquired from the power grid to initially power the closed loop pump 950. In any instance, the pump 950 is an over-center variable displacement high pressure pump capable of providing bi-directional variable flow.
The powerhouse module 275 also includes a precision metering valve 955. The valve 955 is referred to in the industry as a direct operated zero overlap servo valve. In the view of
It is understood that the powerhouse module 275 includes a number of other components that make up a fluid circuit. These may include a fluid reservoir 360 and various conductor lines, sensors, solenoids and transducers (not shown).
The hydraulic fluid pumping system 300 may also optionally include a so-called iron lung (not shown). The iron lung provides a breathing function for the system 900, allowing for expansion and contraction of fluid as ambient temperature changes, and providing a barrier to prevent moisture and contaminants from entering the reservoir.
As can be seen, an improved rod pumping unit is provided. The rod pumping unit offers ultra-long pump strokes, scalable to even greater lengths. In one aspect, the rod pumping unit offers at least 480 inches of polished rod travel. Increased pump stroke length combined with use of a larger pump enables increased fluid displacement capability downhole. Increased pump stroke length also reduces rod reversals, thereby preserving the life of the rod string and surrounding downhole tubing.
As part of the rod pumping unit, a unique traveling sheave arrangement is provided. The wheels of the traveling sheave are configured to cancel out the majority of non-lifting forces. The vertical support column guides the traveling sheave wheels up and down in inverse relation to movement of the polished rod, which provides linear travel amplification. Of interest, the vertical support column does not support the counter-weight mechanism.
The rod pumping unit may be delivered to a well site in two separate modules, those representing the surface pumping unit and the counter-weight system. The rod pumping unit and its modularity of design allows multiple types of force and travel generating input mechanisms to power and reciprocate the traveling sheave. These include the use of counter weight plates (such as plates 272), an electric motor and a hydraulic fluid pump.
In one aspect, the rod pumping unit includes the ability to harvest the energy provided by gravity and the weight of the rod string during the down stroke by using an electrical regenerating turbine. Such “free” energy may be stored in a battery, a capacitor, a bank of super capacitors, or combinations thereof (collectively, an “energy storage device”). During the upstroke, current is sent from the energy storage device to an electric motor associated with the counter-weight system. The electric motor serves as the prime mover 330, which in turn drives the hydraulic pump 340. Such technology is described further in U.S. Pat. No. 8,562,308, which is incorporated herein by reference in its entirety.
Referring back to
In addition to the rod pumping unit, a method of producing oil using a surface rod pumping unit is also provided. In one aspect, the method first comprises providing a surface rod pumping unit. The surface rod pumping unit may be designed in accordance with the rod pumping unit 200 described above, in its various embodiments. For example, the surface rod pumping unit may comprise:
Preferably, the sheave of the standing sheave comprises a pair of wheels rotationally fixed above or to opposing sides of the vertical support column, while the traveling sheave also comprises a pair of wheels, wherein the pair of wheels of the traveling sheave reciprocate along the vertical support column together. The pair of wheels making up the standing sheave rotate together about an axis of rotation through the vertical center-line of the standing sheave, while the pair of wheels making up the traveling sheave rotate together about an axis of rotation through the vertical center-line of the traveling sheave.
Preferably, the wheels of the standing sheave and the wheels of the traveling sheave each have an axle. In an aspect, the axles are stationary while the wheels bearingly rotate about the respective axles.
Preferably, each of the at least two ropes is a wire rope. Each wire rope has a second end opposite the first end that is pinned to the vertical support column proximate an upper end of the vertical support column. In one aspect, a crown is provided at the top of the vertical support column. The crown supports the axle for the standing sheave. The crown also receives pins that hold the distal end of the wire ropes. In this instance, the upper end of the vertical support column is the crown.
In the method, the vertical linear actuator may comprise a first end fixed relative to the horizontal support base, and a second end affixed to the traveling sheave. Of interest, the second end remains in tension at all times during movement of the polished rod. The fixed end may comprise a barrel while the second end is a piston rod. The piston has a plunger that resides within the barrel. Movement of the piston rod is accomplished by applying hydraulic force against the plunger.
The method also includes cycling the linear actuator. In this arrangement, cycling the linear actuator in order to cause the traveling sheave to reciprocate up and down along the vertical support column such that upward movement of the traveling sheave produces a downstroke of the polished rod, while downward movement of the traveling sheave produces an upstroke of the polished rod.
In a preferred arrangement, each of the polished rod, the traveling sheave and the standing sheave has a vertical center-line, with each center-line being offset from the other. In addition, the vertical support column defines a vertical center-line. The center-line of the traveling sheave is proximate the back face of the vertical support column. The center-line of the traveling sheave and the standing sheave are offset from the center-line of the vertical support column so that the wire ropes create side load forces supported by the vertical support column in a generally balanced position throughout the movement cycles.
Preferably, the linear actuator has a distal end that is operatively connected to the traveling sheave. Upward movement of the linear actuator causes the traveling sheave to travel to an upper end of the vertical support column, defining a raised position. In one aspect, when the traveling sheave is in its raised position, the wire ropes form an angle that is between 4° and 8° relative to the center-line of the vertical support column. Downward movement of the linear actuator causes the traveling sheave to travel to a lower end of the vertical support column, defining a lowered position. In one aspect, when the traveling sheave is in its lowered position, the wire ropes form an angle that is between 1° and 4° relative to the center-line of the vertical support column.
The method 1000 first comprises providing a rod pumping unit for a well. This is shown in Box 1005 of
The method 1000 also includes connecting the vertical linear actuator to the traveling sheave. This is provided in Box 1010. Preferably, the vertical linear actuator comprises a hydraulically actuated piston that reciprocates in and out of a barrel. This occurs in response to pressure applied by hydraulic fluid against a plunger. The proximal end of the barrel may be pinned to the horizontal support base using a clevis arrangement. Alternatively, a front trunnion connection may be provided. Similarly, a distal end of the piston may be pinned to an axle of the traveling sheave.
The method 1000 also includes providing a polished rod along a front face of the vertical support column. This is seen in Box 1015. The polished rod is clamped or otherwise connected to a carrier bar such that movement of the carrier bar imparts reciprocating motion to the polished rod.
The method 1000 further comprises operatively connecting the traveling sheave to the polished rod. This step is provided in Box 1020 of
In the step of Box 1020, the traveling sheave is operatively connected to the polished rod using a plurality of ropes. The ropes may be pinned at one end to the vertical support column, then be spooled under the traveling sheave, and then over the standing sheave. A distal end of the ropes is then connected to a carrier bar. The carrier bar is clamped to the polished rod as is known in the art of artificial lift.
The method 1000 additionally includes providing a power system. This is seen in Box 1025. The power system is used to reciprocate the polished rod of the rod pumping unit 200. In one aspect, the power system is a hydraulic power system having an electric motor, a master fluid valve, and a hydraulic pump. The hydraulic power system may be either an open loop or a closed loop system. A closed loop system is preferred as it is more energy efficient. Particularly, a closed loop system is able to recoup the kinetic energy generated by the falling polished rod string and re-use it with minimal losses.
The electric motor serves as a prime mover to the hydraulic pump, while a controller 410 controls position of the master fluid valve. Movement of the master fluid valve, in turn, regulates the pump swashplate which directs fluid into and out of the barrel of the near-vertical linear actuator, thereby moving the traveling sheave.
Preferably, actuation of the electric motor and movement of the master fluid valve are controlled by the same controller. Thus, the method 1000 also comprises providing a controller for the rod pumping unit. This is seen in Box 1030 of
In one aspect, the controller 410 causes the electric motor to move the master fluid valve between an upstroke pumping mode and a downstroke pumping mode. This is provided in the step of Box 1035, which addresses activating the electric motor as a prime mover of the hydraulic pump.
In the upstroke pumping mode, the controller sends a signal to move the master fluid valve into a first position. This is indicated at Box 1040. Hydraulic fluid is pumped through the master fluid valve, through an oil line, into the barrel of the vertical linear actuator, and against the plunger. This pushes the piston of the near-vertical linear actuator into the barrel downward, and produces an upstroke of the polished rod. Note that the first position is infinitely variable.
In the downstroke pumping mode, the controller sends a signal to move the master fluid valve into a second position. This is shown at Box 1055. Hydraulic fluid is released from the barrel and through the oil line, allowing the piston to extend back out of the barrel upward. This, in turn, allows the polished rod to gravitationally fall in a downstroke. Note that this second position is also infinitely variable.
The controller 410 is programmed to know a wide number of variables associated with the rod pumping unit 200. These may include a length of the rod string and a location of the traveling valve in the wellbore. In one aspect, the controller 410 is able detect the dynamic lifting and lowering loads generated by the carrier bar 260 and the polished rod string assembly. At the same time, the controller 410 can monitor actual position of the polished rod string assembly with a high degree of resolution and sample rate while the rod pumping unit is lifting and lowering the polished rod string assembly and fluid column loads. This is indicated at Box 1045. In this way, the controller 410 can move the traveling valve down to within inches of the standing valve during the down stroke. Beneficially, this forces the travelling valve to open more efficiently and helps regulate actual tag force when bottom pump spacing is brought to zero space.
Position feedback may be provided by a location sensor 984 associated with the polished rod 265. The location (or position) sensor 984 may be mounted alongside or even inside the piston rod of the near-vertical linear actuator 250.
The controller 410 also gathers data during the pump cycles related to load. Such data includes both weight transfer position and rate of change during the weight transfer. The step of monitoring a force sensor is shown in Box 1050. The force sensor may be a pressure transducer 982 placed along hose 965, as shown in
With all this information, the controller 410 is able to optimize pumping performance of the rod pumping unit. The optimization can occur in various ways. These include lifting the polished rod string assembly and fluid column load only as far as required to optimize liquid fillage volume, and then lowering the polished rod string assembly as far as possible to increase gas compression under the traveling valve and plunger assembly within the downhole pump. Note that this also reduces energy usage by the prime mover as the prime mover is not moving the stroke length more than is necessary. Stopping and dwelling at the top of the stroke for a brief instant allows additional downhole pump fillage across the standing valve.
Preferably, the polished rod may be held at any position along the upstroke or the downstroke. This is provided at Box 1060 of
In operation, the rod pumping unit uses the near-vertical linear actuator to cyclically move the traveling sheave up and down along the vertical support column. This is shown at Box 1065. In one novel aspect, the vertical linear actuator remains in tension during the entire cycle by virtue of being operatively connected to the polished rod string assembly. Beneficially, the force and position sensors allow the controller 410 to perform autonomous dynamometer testing using the technology of U.S. Pat. No. 8,844,626 discussed above. In another novel aspect, a counter-weight is provided to work with the plunger of the vertical linear actuator. The counter-weight reduces the amount of work required to raise the polished rod during the upstroke pumping mode.
A benefit of the optimization provided by the controller 410 is reducing fluid pound downhole. The controller 410 knows where the polished rod position weight transfer occurred on previous downstrokes. The controller 410 can then adjust a rate of descent of the polished rod assembly during a subsequent downstroke and transition into a slower speed, allowing weight transfer to occur more slowly with less shock caused from the plunger/traveling valve contacting the fluid volume within the working barrel of the down hole pump. This is provided in connection with Box 1070, which shows the controller sending a signal to the hydraulic pump to change a pump speed while lowering the polished rod string into the well. This is done by slowing a rate of release of hydraulic fluid during the fluid releasing mode.
In one aspect, the controller 410 is capable of detecting and accepting current plus previous pumping cycle feedback conditions such as polished rod position, polished rod supported force, and rates of change of polished rod supported force over time. In another aspect, the controller 410 is capable of evaluating performance of the current pump cycle, and then computing and outputting a tailored control signal for optimizing the next pumping cycle(s). Regulating the down stroke motion of the pumping cycle allows for total regenerated energy level output or capture, hence, reducing energy usage. This is provided in connection with Box 1075, which shows the controller sending a signal to the hydraulic pump to change a pump speed during the downstroke.
Optionally, the controller 410 may regulate tagging forces to mechanically assist the traveling valve during extreme gas interference operating wells. The step of Box 1080 demonstrates a signal being sent to the master fluid valve to change from a first position to a second position during the downstroke pumping mode. Having the ability to regulate force of impact at the bottom of the well allows tagging as a reliable method to off seat the traveling valve with minimal damage. These processes can save lifting energy by reducing total travel lifted or speed of lifting thru the travel distance plus managing energy levels, both input and output energy flow.
In one aspect, the controller is configured to control movement of the polished rod by sending a signal to the hydraulic pump to (i) increase a pump rate during an upstroke pumping mode, thereby increasing a speed of the upstroke; (ii) decrease a pump rate during the upstroke pumping mode, thereby decreasing a speed of the upstroke; and (iii) stop pumping during an upstroke or during a downstroke, thereby holding the polished rod in a fixed position.
In another aspect, the controller receives signals from the position sensor and the load sensor and, in response, adjusts (i) a speed of the upstroke of the polished rod, (ii) a speed of the downstroke of the polished rod, (iii) a length of the upstroke; (iv) a length of the downstroke; and any time delay at the top of pump intake movement.
In summary, the controller 410 is capable of commanding the rod pumping unit 200 how far to lift, how fast to lift, whether to dwell at the top of stroke, how fast to lower, one or more speeds to lower, distance to lower at selected speed and how far to lower in that current pump stroke cycle.
The particular embodiments disclosed above are illustrative only, as the embodiments may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. It is therefore evident that the particular embodiments disclosed above may be altered or modified, and all such variations are considered within the scope and spirit of the application. For example, instead of using a hydraulic piston-and-barrel arrangement for the linear actuator, the linear actuator may be any of:
It is understood that these items could also be driven by an internal combustion engine. However, it is preferred to use a variable displacement over-center type pump due to ease of starting, stopping, controlling direction, controlling velocity or variable velocity including controlled accelerations and decelerations in addition to limiting maximum pressure levels of discharge fluid and regulating minimum pressure levels during low side intake fluid pressure levels.
It is also noted that the present inventions are not limited by the top of rod pump controller used for cycling the polished rod and supported traveling valve. Numerous examples of controllers for optimizing pump rate and/or stroke length exist, such as those described in U.S. Pat. No. 11,162,331 (entitled “System and Method for Controlling Oil and Gas Production”); U.S. Pat. No. 10,947,833 (entitled “Diagnostics of Downhole Dynamometer Data for Control and Troubleshooting of Reciprocating Rod Lift Systems”); and U.S. Pat. No. 10,422,205 (entitled “Low Profile Rod Pumping Unit With Pneumatic Counterbalance for the active Control of the Rod String”). Each of these patents is incorporated herein by reference in its entirety.
In the claims which follow, the word “comprising” is used in its inclusive sense and does not exclude other elements being present. The indefinite articles “a” and “an” before a claim feature do not exclude more than one of the feature being present. Each one of the individual features described here may be used in one or more embodiments and is not, by virtue only of being described here, to be construed as essential to all embodiments as defined by the claims.
This application claims the benefit of U.S. Ser. No. 63/178,445 filed Apr. 22, 2021. That application is entitled “ULRPSU Ultra-Long Rod Pump Surface Unit.” This application also claims the benefit of U.S. Ser. No. 63/299,793 filed Jan. 14, 2022. That application is entitled “Rod Pumping Surface Unit.” This application also claims the benefit of U.S. Ser. No. 63/313,157 filed Feb. 23, 2022. That application is also entitled “Rod Pumping Surface Unit.” Each of these provisional patent applications is incorporated herein in its entirety by reference.
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