US20200309112A1

US20200309112A1 - Pumping Unit Having Zero-Imbalanced Beam, Lagging Counterweights, and Setback Crank Point

Info

Publication number: US20200309112A1
Application number: US16/372,218
Authority: US
Inventors: Darius J. Yakimchuk; Don R. Connally
Original assignee: Weatherford Technology Holdings LLC
Current assignee: Weatherford Technology Holdings LLC
Priority date: 2019-04-01
Filing date: 2019-04-01
Publication date: 2020-10-01
Also published as: WO2020205270A1

Abstract

A surface unit can operate as a longer stroke unit to reciprocate a rod string for a downhole pump in a well. The unit has an end weight that gives the walking beam and head a zero-imbalance about the unit's fulcrum point. The unit can also operate as a phased unit in which the counterweights of the crank arms lag behind the pivot connection and/or the crank point is disposed rearward of the equalizer bearing of the walking beam.

Description

BACKGROUND OF THE DISCLOSURE

Reciprocating pump systems, such as sucker rod pump systems, extract fluids from a well and employ a downhole pump connected to a driving source at the surface. A rod string connects the surface driving force to the downhole pump in the well. When operated, the driving source cyclically raises and lowers the downhole pump, and with each stroke, the downhole pump lifts well fluids toward the surface.
For example, FIG. 1 shows a sucker rod pump system 10 used to produce fluid from a well. A downhole pump 14 has a barrel 16 with a standing valve 24 located at the bottom. The standing valve 24 allows fluid to enter from the wellbore, but does not allow the fluid to leave. Inside the pump barrel 16, a plunger 20 has a traveling valve 22 located at the top. The traveling valve 22 allows fluid to move from below the plunger 20 to the production tubing 18 above, but does not allow fluid to return from the tubing 18 to the pump barrel 16 below the plunger 20. A driving source (e.g., a pump jack or pumping unit 30) at the surface connects by a rod string 12 to the plunger 20 and moves the plunger 20 up and down cyclically in upstrokes and downstrokes.
During the upstroke, the traveling valve 22 is closed, and any fluid above the plunger 20 in the production tubing 18 is lifted towards the surface. Meanwhile, the standing valve 24 opens and allows fluid to enter the pump barrel 16 from the wellbore.
At the top of stroke, the standing valve 24 closes and holds in the fluid that has entered the pump barrel 16. Furthermore, throughout the upstroke, the weight of the fluid in the production tubing 18 is supported by the traveling valve 22 in the plunger 20 and, therefore, also by the rod string 12, which causes the rod string 12 to stretch. During the downstroke, the traveling valve opens, which results in a rapid decrease in the load on the rod string 12. The movement of the plunger 20 from a transfer point to the bottom of stroke is known as the “fluid stroke” and is a measure of the amount of fluid lifted by the pump 14 on each stroke.
At the surface, the pump jack 30 is driven by a prime mover 40, such as an electric motor or internal combustion engine, mounted on a pedestal above a base 32. Typically, a pump controller 60 monitors, controls, and records the pump unit's operation. Structurally, a Samson post 34 on the base 32 provides a fulcrum on which a walking beam 50 is pivotally supported by a saddle bearing assembly 35.
Output from the motor 40 is transmitted to a gearbox 42, which provides low-speed, high-torque rotation of a crankshaft 43. Both ends of the crankshaft 43 rotate crank arms 44 having counterbalance weights 46. Each crank arm 44 is pivotally connected to a pitman arm 48 by a crank pin bearing 45. In turn, the two pitman arms 48 are connected to an equalizer bar 49, which is pivotally connected to the rear end of the walking beam 50 by an equalizer bearing assembly 55.
A horsehead 52 with an arcuate forward face 54 is mounted to the forward end of the walking beam 50. As is typical, the face 54 may have tracks or grooves for carrying a flexible wire rope bridle 56. At its lower end, the bridle 56 terminates with a carrier bar 58, upon which a polished rod 15 is suspended. The polished rod 15 extends through a packing gland or stuffing box at the wellhead 13. The rod string 12 of sucker rods hangs from the polished rod 15 within the tubing string 18 located within the well casing and extends to the downhole pump 14.
As is known, pump jack operating characteristics are typically characterized by the American Petroleum Institute (“API”) Specifications, which expresses parameters as a function of the geometry of a pumping unit's four-bar linkage. Standardized API linkage geometry designates: dimension “A” as the distance from the center of the saddle bearing 35 to the centerline of the polished rod 15; dimension “C” as the distance from the center of the saddle bearing 35 to the center of the equalizer bearing 55; dimension “P” as the effective length of the pitman arm 48 as measured from the center of the equalizer bearing 55 to the center of the crank pin bearing 45; dimension “R” as the distance from the centerline 43 of the crankshaft to the center of the crank pin bearing 45; dimension “H” as the height from the center of the saddle bearing 35 to the bottom of the pump jack base 32; dimension “I” is the horizontal distance from the center of the saddle bearing 25 to the centerline 43 of the crankshaft; dimension “G” as the height from the centerline 43 of the crankshaft to the bottom of the pump jack base 32; and dimension “K” as the distance from the centerline 43 of the crankshaft to the center of the saddle bearing 35. Dimension “K” may be computed as:
K=√{square root over ((H−G)²+l²)}
Alteration of the four-bar linkage may have a significant effect on the operating characteristics of the pumping unit 30, such as changing the allowable polished rod load, changing the shape of the permissible load envelope, altering the length of the pumping stroke, inducing a phase angle shift in the counterbalance, etc. Moreover, the change in operating characteristics at surface may further affect controls, analysis, and diagnostics of the downhole rod pump because calculations for these features are typically based on the standard four-bar linkage (K-R-P-C).
A conventional rod pumping unit 10 as in FIG. 1 has considerable inertia effects inherent to the design. The crank arms 42 connected to the gear reducer 42 and having the counterweights 46 affixed to them must overcome the equivalent torque that is applied by the connected rod string 12 extending from the wellbore to the horsehead 52. These counterweights 46 are significantly large masses (˜1,800 lb. for a mid-range counterweight) so a considerable amount of torque from the prime mover 40 is needed to initiate their rotational motion. Additionally, the balance beam 50 and associated parts that convert the rotary motion of the crank arms 42 into articulating motion also have significant mass that also require torque from the prime mover 40 to sustain the desired rocking motion that lifts and lowers the rod string 12. Even though the conventional rod pumping unit 10 has been in use for over 80 years, some of the inertia effects of both the rotational and articulating elements are not as well-known as some might believe.
There are some pumping unit designs that are different than the conventional pumping unit 10 of FIG. 1. For example, it has been known for some time in the art to place weight at the rearward end of a walking beam for a surface pumping unit. As two examples, U.S. Pat. Nos. 2,175,588 and 2,408,200 have additional weight on the rearward end of the walking beam. The rearward end of the beam extends a considerable distance beyond the point of attachment of the pitman arms and is provided with a weight for counterbalancing the pumping loads.
Another type of pumping unit having a weight on the rearward end of the beam is a beam balanced unit. As opposed to a crank balanced unit as in FIG. 1, this type of beam balanced unit does not use counterweights on crank arms. Instead, the beam balanced unit only uses counterweight on the rearward end of the beam. Typically, the weight is adjustable so operators can determine the proper number or placement of weight to achieve the desired counterbalance. Such a beam balance unit has been used for low production installations, such as for producing a shallow well in a mature oilfield.
A curved beam pumping unit available from Schlumberger uses an adjustable weight positioned on the bent beam's rearward end. The conventional crank weight and the adjustable beam weight on the curved beam are intended to benefit the gearbox torque of this curved beam pumping unit.
The subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.

SUMMARY OF THE DISCLOSURE

According to one arrangement of the present disclosure, a surface pumping unit is operated by a prime mover for reciprocating a rod load for a downhole pump in a well. The unit comprises a frame, a beam, a crank arm, a counterweight, and a pitman art.
The frame is disposed at surface and has a fulcrum point. The beam is pivotable at the fulcrum point of the frame. The beam has a first end having a head connecting to the rod load extending from the well. The beam has a second end having a first bearing point. An end weight is disposed on the second end of the beam rearward of the first bearing point. A forward section of the first end of the beam and the head disposed forward of the fulcrum point has a forward weight. A rearward section of the second end of the beam and the end weight disposed rearward of the fulcrum point having a rearward weight. The forward weight is balanced relative to the rearward weight.
The crank arm is connected to the prime mover and is rotatable thereby about a crank point. The counterweight is disposed on the crankarm, and the pitman arm is connected between the first bearing point on the beam and a second bearing point on the crank arm. The second bearing point is disposed between the counterweight and the crank point.
The crank arm rotated by the prime mover about the crank point translates the pitman arm to oscillate the beam on the fulcrum point and reciprocates the rod load along the wellbore axis.
The frame can include: a base disposed at the surface; and a post extending from the base to the fulcrum point along a line from vertical.
The beam can define a straight axis having first and second sections. The first section from the fulcrum point to a face of the head can have a first length (A), and the second section from the fulcrum point to the first bearing point can have a second length (C). The first length (A) can be greater than the second length (C).
The fulcrum point can comprise a saddle bearing, the first bearing point can comprise an equalizer bearing, and the second bearing point can comprise a crank pin bearing. The unit can include another crank arm connected to the prime mover and rotatable thereby about another crank point; and another pitman arm connected between another first bearing point on the beam and another second bearing point on the other crank arm, wherein the pitman arms connect with an equalizer beam at the first bearing point. The unit can further comprise a gear reducer operably connecting the crank point to the prime mover.
In one configuration, the crank point can be centered vertically below the first bearing point on the beam when the beam is situated horizontally. For instance, the first bearing point can be disposed at a first horizontal dimension (C) along the beam relative to the fulcrum point, and the crank point can be disposed at a second horizontal dimension (I) relative to the fulcrum point. In this configuration, the second horizontal dimension (I) can be approximately equal to the first horizontal dimension (C).
For this configuration, the second bearing point can be disposed along a longitudinal axis defined by the crank arm. Alternatively, the second bearing point can be disposed offset at an angle from the longitudinal axis of the crank arm.
In another configuration, the crank point can be situated vertically rearward below the first bearing point on the beam when the beam is situated horizontally. For instance, the first bearing point can be disposed at a first horizontal dimension (C) along the beam relative to the fulcrum point, and the crank point can be disposed at a second horizontal dimension (I) relative to the fulcrum point. The second horizontal dimension (I) can be greater than the first horizontal dimension (C).
For this other configuration, the second bearing point can be disposed along a longitudinal axis defined by the crank arm. Alternatively, the second bearing point can be disposed offset at an angle from the longitudinal axis of the crank arm.
According to another arrangement of the present disclosure, a surface pumping unit is operated by a prime mover for reciprocating a rod load for a downhole pump in a well. The unit comprises a frame, a beam, a crank arm, a counterweight, and a pitman arm. The frame is disposed at the surface and has a fulcrum point. The beam is pivotable at the fulcrum point of the frame. A first end of the beam has a head connecting to the rod load extending from the well. A second end of the beam has a first bearing point and has an end weight disposed rearward of the first bearing point.
The crank arm is connected to the prime mover and is rotatable thereby about a crank point. The counterweight is disposed on the crankarm. The pitman arm is connected between the first bearing point on the beam and a second bearing point on the crank arm. The second bearing point is disposed between the counterweight and the crank point and is disposed offset at an angle from a longitudinal axis defined by the crank arm.
A forward section of the first end of the beam and the head disposed forward of the pivot point can have a forward weight. Meanwhile, a rearward section of the second end of the beam and the end weight disposed rearward of the pivot point can have a rearward weight, where the forward weight is balanced relative to the rearward weight about the pivot point.
The crank point can be situated vertically rearward below the first bearing point on the beam when the beam is situated horizontally. In this instance, the first bearing point can be disposed at a first horizontal dimension (C) along the beam relative to the fulcrum point, and the crank point can be disposed at a second horizontal dimension (I) relative to the fulcrum point, where the second horizontal dimension (I) can be greater than the first horizontal dimension (C).
This other arrangement of the pumping unit can include any of the additional features described above with reference to the previous arrangement.
According to yet another arrangement of the present disclosure, a reciprocating pump system is used for a well. The system comprises a downhole pump disposed in the well and comprises a pumping unit disposed at the surface and coupled to the downhole pump by a rod string. The pumping unit can include any of the various features of the pumping units described above.
The foregoing summary is not intended to summarize each potential embodiment or every aspect of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a reciprocating rod pump system known in the art.

FIG. 2A illustrates an elevational view of a reciprocating rod pump system of the present disclosure.

FIG. 2B illustrates geometry of the disclosed reciprocating rod pump system.

FIG. 3A illustrates an elevational view of another reciprocating rod pump system of the present disclosure.

FIG. 3B illustrates geometry of the disclosed reciprocating rod pump system.

FIG. 3C illustrates another geometry of the disclosed reciprocating rod pump system.

DETAILED DESCRIPTION OF THE DISCLOSURE

Referring to FIG. 2A, a surface pumping unit 100 according to the present disclosure is used for reciprocating a rod string for a downhole pump in a well. Details of the well, wellhead, polished rod, carrier bar, downhole pump, and the like are not shown here for simplicity, but have been discussed previously.
The pumping unit 100 includes a frame having a base 110 and a Samson post 112. An actuator or prime mover 120 is disposed on the base 110, a crank assembly is connected to the prime mover 120, and a walking beam 150 is connected to the crank assembly and is supported by the Samson posts 112 on the base 110. Structurally, the Samson posts 112 on the base 110 provide a fulcrum point on which the walking beam 150 is pivotally supported by a saddle bearing assembly 116. In addition to the Samson posts 112, the frame on the base 110 may include one or more back posts 114 joined together forming an A-frame to support the walking beam 150.
The pumping unit 100 is driven by the prime mover 120, such as an electric motor or internal combustion engine, mounted on a pedestal above the base 110. A pump controller (not shown) monitors, controls, and records the pump unit's operation. Output from the prime mover 120 is transmitted to a gearbox 124, which provides low-speed, high-torque rotation of a crankshaft 132. Both ends of the crankshaft 132 rotate a respective crank arm 130 about the crankshaft's centerline. Disposed away from the crankshaft 132, the crank arms 132 each have a counterbalance weight 136. Each crank arm 130 is pivotally connected to a pitman arm 140 by a crank pin bearing 134, also called a wrist pin. In turn, the two pitman arms 140 are connected to an equalizer bar 142, which is pivotally connected toward the rear end 151 b of the walking beam 150 by an equalizer bearing assembly 156.
A horsehead 152 with an arcuate forward face 154 is mounted to the forward end 151 a of the walking beam 150. As is typical, the face 154 may have runners (tracks or grooves) for carrying a flexible wire rope bridle 56. At its lower end, the bridle 56 terminates with a carrier bar (not shown), upon which a polished rod (not shown) for a reciprocating rod system is suspended. As before, the polished rod typically extends through a packing gland or stuffing box at a wellhead for connection to downhole sucker rods and pump.
As the prime mover 120 rotates the crank arms 130, the walking beam 150 seesaws on the frame's bearing 116 so the polished rod reciprocates the rod system and downhole pump in the well. During operation, for example, the prime mover 120 and gearbox 124 rotate the crank arms 130, which causes the rearward end 151 b of the walking beam 150 to move up and down through the movement of the pitman arms 140. Up and down movement of the rearward end 151 b causes the walking beam 150 to pivot about the bearing assembly 116 resulting in downstrokes and upstrokes of the horsehead 152 on the forward end 151 a.
During an upstroke, for example, the prime mover 120 and gearbox 124 aided by the counterbalance weights 136 overcomes the weight and load on the horsehead 152 and pulls the polished rod string up from the wellbore, which reciprocates the rod string and downhole pump in the well to lift fluid. During a downstroke, the prime mover 120 aided by the weight and load on the horsehead 154 rotates the crank arms 130 to raise the counterbalance weights 136.
The pumping unit 100 may be used for specific pumping applications, calling for changes in its particular geometry and structure compared to a conventional unit. The unit 100 may also be used in pumping applications having particular requirements for rod loads, stroke length, and the like. For example, the unit 100 may have an oversized horsehead 152, an increased forward length (A) on the beam 150, or other changes to produce longer strokes with the unit 100.
The changes in the geometry and the structure, the changes in the particular rod loads, or the like can produce imbalance in the unit 100. To offset the imbalance, the unit 100 according to the present disclosure has an end weight 160 on the rearward end 151 b of the beam 150. The end weight 160 can include a unitary or modular unit and can have a fixed weight value. The end weight 160 can attach or affix to the end 151 b in a number of ways. For example, the end weight 160 can be attached to the rearward end of the beam 150 using techniques, such as welding, bolting, flanges, and the like. The attachment may be permanent or may allow for different end weights 160 with different weight values to be used interchangeably as needed on the end 151 of the beam 150.
The end weight 160 is configured to eliminate the imbalance of the beam 150 and the head 152 and allow the gear reducer 124 and the crank arm counterweights 136 to only have to lift the rod string. This configuration may allow the pumping unit 100 to pull higher loads than a conventional unit. Moreover, this configuration may allow for easier set-up of the unit 100 due to the zero-imbalance of the beam 150. For example, the beam 150 with head 152 and weight 160 can easily be adjusted with little force (inertia) during set up on the frame (112, 114), which may eliminate the need for heavier installation equipment. The reduced inertia may also reduce the amount of torque needed from the prime mover 120 to initiate motion and/or to sustain the desired motion that lifts and lowers the rod string.
Although the configuration can be incorporated into any size of the unit 100, the benefits may be best suited for the pumping unit 100 when head heavy, as is typically found in a larger stroke unit. Some installations require pumping units having larger or longer strokes compared to conventional arrangements. The typical stroke length of a conventional pumping unit may be from about 50-in to about 240-in, whereas the stroke length for a larger stroke, conventional pumping unit installation may be from about 150-in to 300-in. (Reference to larger stroke here is not meant to be confused with those “long stroke pumping units” that use a belt drive.)
For the larger stroke pumping units, the length of the walking beam ahead of the fulcrum point 116 has to be increased so as to provide the larger stroke. This results in a longer arm dimension “A” for the distance from the center of the saddle bearing 116 to the centerline of the polished rod. In general, the arm dimension (A) from the fulcrum point 116 to the face 154 of the head 152 is greater than the other beam dimension (C) from the fulcrum point 116 to the equalizer bearing point 156. For the larger stroke pumping unit 100 disclosed here, the forward dimension (A) can be about two times longer than the rearward dimension (C), but other variations can be used. In general, the ratio of the forward dimension (A) relative to the rearward dimension (C) can be between approximately 0.8 to just over 2 (e.g., about 2.05). In addition to the additional arm length, the longer stroke unit also requires a longer runner for the wire rope bridle so that the head 152 must be larger, which results in more weight. The longer moment arm (A) and head weight create a large structural imbalance in the beam 150.
In the unit 100 having a longer moment arm (A) and an oversized horsehead 152 and/or having a significant increase in the imbalance due to other secondary effects, additional counterweight 136 could be added to the crank arms 130 to offset the imbalance. Increasing the counterweight 136 on the crank arms 130 would add to the rotational inertia effects, which may not be desirable. Instead, the present arrangement adds the additional weight to the rearward end 151 b of the beam 150 using the end weight 160. This added weight 160 to the end 151 b of the beam 150 changes the articulating inertia effects, which may have benefits in some implementations.
In many installations, for example, the prime mover 120 is driven with a variable speed drive. This tends to keep the rotational speed of the gear reducer 124 and the crank arms 130 at nearly a constant rate. Therefore, any rotational inertia effects are reduced considerably and may be of concern only during start-up and shut-down operations. However, if such a unit were allowed to operate in an out-of-balance condition, the rotational inertia effects can become more pronounced. The end weight 160 on the end 151 b of the beam 150 opposite the horsehead 152 to overcome the imbalance will tend to increase the articulating inertia. However, the beam 150 is supported on (and rotates about) the saddle bearing assembly 116, which may tend to reduce the net effect.
In particular, even though the articulating inertia is increased, the requirement to overcome the imbalance with the counterweights affixed to the crank arms is reduced. In turn, the net torque required from the prime mover to operate the unit 100 is reduced. Essentially, the added weight to the end of the walking beam to offset the imbalance increases the articulating inertia slightly and reduces the rotational inertia. More significantly, the amount of counterweight torque required is reduced. Example calculations show that the additional weight 160 on the end of the walking beam 150 may reduce the counterweight torque on the order of about 30%, which is a big savings when it comes to motor power requirements. Additionally, the example calculations show that the net inertia effects of the articulating members do not increase enough to raise any other concerns.
Additional features of the pumping unit 100 are discussed with reference to FIG. 2B, which schematically depicts the geometric arrangement of the unit 100. In this depiction, the frame, actuator, arms, and the like are not shown. Instead, the fulcrum point for the walking beam 150 is represented as a pivot point for the bearing assembly 116.
As shown in the geometry of FIG. 2B, the rearward end 151 b of the beam 150 has the bearing point (i.e., equalizer bearing assembly 156) and has the additional end weight 160 disposed rearward of the bearing point 156. Because the beam 150 is pivotable at the fulcrum point of the saddle bearing assembly 116 on the frame, a forward section 153 a of the forward end of the beam 150 and the head 152 disposed forward of the pivot point 116 has a forward weight (WF+WH), whereas a rearward section 153 b of the rearward end of the beam 150 and the end weight 160 disposed rearward of the pivot point 116 has a rearward weight (WR+WE).
For the disclosed pumping unit 100, the forward weight (WF+WH) is intended to be balanced relative to the rearward weight (WF+WE) about the fulcrum point 116. Accordingly, the weight value (WE) for the end weight 160 is selected to achieve this balance by countering any increased weight from an increased length (A) of the forward beam end and from an increased size for the head 152 so the pumping unit 150 can be used for longer stroke applications.
In one implementation, for example, the walking beam 150 has a weight (WF+WR) of about 6,500-lbs, and the head 152 has a weight (WH) of about 3500-lbs. The equalizer beam 142 can be about 1,300-lbs. For this implementation, the weight value (WE) for the end weight 160 can be about 6,500-lbs. In this instance, the extra weight value (WE) provided by the end weight 160 can be about ⅓ of the total weight of the assembly (walking beam 150, head 152, equalizer beam 142, and end weight 160). Of course, as one skilled in the art will appreciate with the benefit of the present disclosure, the weight value (WE) for the end weight 160 will vary depending on the lengths (A) and (C) of the beam 150 and other variables, dimensions, and weights of elements on the pumping unit 100.
The face 154 connects to the polished rod extending along the wellbore axis WA from the wellhead. The prime mover (120) is not shown, but the crank arm (130) is depicted as radius (R) connected between a crank point of the crank pin 132 and a first bearing point for the wrist pin 134. The pitman arm (140) is depicted as linkage (P) connected between the first bearing point 134 and a second bearing point for the equalizer bearing assembly 152 on the walking beam 150.
The crank point 132 is disposed at a first dimension (K) relative to the fulcrum point 116 (i.e., the distance from the centerline of the crankshaft to the center of the saddle bearing), and the pitman arm (130) has a length of a second dimension (P) (i.e., the effective length of the pitman arm (130) as measured from the center of the equalizer bearing 156 to the center of the crank pin bearing 134). The first bearing point 134 is disposed at a third dimension (R) from the crank point 132 (i.e., the distance from the centerline 132 of the crankshaft to the center of the crank pin bearing 134), and the second bearing point 156 is disposed at a fourth dimension (C) relative to the fulcrum point 116 (i.e., the distance from the center of the saddle bearing 116 to the center of the equalizer bearing 156). This completes the four-bar linkage of the unit 100.
Other geometric measures include the dimension (A), heights (H) and (G), and separation (I). The dimension (A) is the distance from the center of the saddle bearing 116 to the centerline of the polished rod represented by the wellbore axis WA and defines the radius at which the face 154 arcs along (circumscribes) a segment at a radius relative to the fulcrum point 116, the segment being tangential to the wellbore axis (WA). The height (H) is the fixed elevation of the fulcrum point 116 from the surface S on which the base (110) is supported, and the height (G) is the fixed elevation of the crank point 134 from the surface S. Finally, the separation (I) is the fixed vertical distance between the fulcrum point 116 and the crank point 132.
As noted, the unit 100 operates as a kinematic four-bar linkage (KPRC), in which each of four rigid links (KPRC) is pivotally connected to two other of the four links (KPRC) to form a closed polygon. In the mechanism, the link (K) is fixed as the ground link. The two links (C, R) connected to the ground link (K) are referred to as grounded links, and the remaining link (P) not directly connected to the fixed ground link (K) is referred to as the coupler link. The grounded link (R) rotated by the prime mover about the crank point 132 translates the coupler link (P) arm to oscillate the grounded link (C) for the beam 150 on the fulcrum point 116. This in turn oscillates the radius (A) at which the face 154 arcs along (circumscribes) the segment.
Configuring the four-bar linkage (KPRC) of the unit 100 may configure the operating characteristics of the pumping unit 100, such as defining the allowable polished rod load, defining the shape of the permissible load envelope, defining the length of the pumping stroke, inducing a phase angle shift in the counterbalance, etc. Moreover, the configured operating characteristics at surface may further defines controls, analysis, and diagnostics of the downhole rod pump because calculations for these features are typically based on the four-bar linkage (K-R-P-C).
Arranged for longer stroke applications, the unit 100 may have a forward beam dimension (A) that is increased compared to a standard stroke pumping unit. The head 152 may also be larger, having an increase weight (WH) and having a face 154 that may define a greater segment compared to a standard stroke pumping unit. However, the end weight 160 on the rearward end 151 b of the beam 150 that produces the zero-imbalance of the beam 150 can allow the unit 100 to operate efficiently as a kinematic four-bar linkage (KPRC) using many of the same or similar components (i.e., prime mover 120, gearbox 124, crank arms 130, counterweights 136, pitman arms 140, and the like) as used for a conventional longer stroke pumping unit. This provides the unit 100 with flexibility to meet the needs of various pumping implementations.
In the present arrangement of FIGS. 2A-2B, the gear reducer 124 operably connecting the prime mover 120 to the crankshaft 132 is situated in a conventional manner. In particular, the gear reducer 124 has a slow-speed shaft—i.e., the crankshaft 132 about which the crank arms 130 rotate. For this conventionally situated reducer, the center of this slow-speed crankshaft 132 is situated relative to the unit's fulcrum point 116 so that the crankshaft 132 may sit directly under the center of the equalizer bearing 156. Accordingly, in the arrangement of FIGS. 2A-2B, the crank point of the crankshaft 134, which is the slow-moving shaft of the reducer 124, can be centered vertically below the rearward bearing point (i.e., equalizer bearing 156) on the beam 150 when the beam 150 is situated horizontally. In other words, the horizontal distance (I) between the saddle bearing 116 and the crank point 132 may the same as or approximately close to the horizontal distance (C) between the saddle bearing 116 and the equalizing bearing 156.
The values of these horizontal distances (I) and (C) depend on the particulars of the implementation, such as the other dimensions (e.g., KPRAGH) of the unit 100, rod loads, counterweight values, etc. In general, the horizontal distances (I) and (C) can be approximately equal with the difference being approximately between 0 to 10%. In fact, the horizontal distances (I) can be equal to about the distance from the fulcrum point 116 to the end 151 b of the beam 150, which is typically about 9% greater than the distance (C). Such an arrangement dictates some of the other dimensions for the interconnected links (KPRC) of the unit 100.
Additionally, the cranks' bearing point or wrist pin 134 on the crank arm 130 is disposed on the arm's longitudinal axis 131, as seen in FIG. 2B. In particular, the crankpin holes in the pumping unit 100 run parallel to the longitudinal axis 131 of the crank arm 130. Therefore, the counterweights 136 on the crank arms 130 do not lag relative to the pivot connection (wrist pins 134) between the crank arms 130 and the pitman arms 140 as the crank arms 130 rotate clockwise. The pumping unit 100 could run either clockwise or counterclockwise.
The arrangement of the various elements of the disclosed unit 100 is preferably configured so that the pitman arms (140) operate in tension. The counterbalance weight 136 is selected based on the weight and load of the reciprocating rod system (i.e., the force required to lift the reciprocating rod and fluid above the downhole pump in the wellbore). In one embodiment, the counterbalance weight 136 may be selected so that one or more components of the pumping unit 100 have substantially symmetrical acceleration and/or velocity during upstrokes and downstrokes. The component may be any moving part of the pumping unit 100, such as the pitman arm 140, the wrist pin assembly 134, the crank arm 130, the equalizer beam 142, the walking beam 150, the horsehead 152, etc.
Turning to FIG. 3A, another arrangement of a pumping unit 100 is illustrated. Many features of this pumping unit 100 are similar to those discussed previously. Again, the surface pumping unit 100 is operated by a prime mover 120 for reciprocating a rod load for a downhole pump in a well. The unit 100 includes a frame 112, 114, a beam 150, a crank arm 130, a counterweight 136, and a pitman arm 140. The frame 112, 114 is disposed at the surface and has a fulcrum point 116, about which the beam 150 is pivotable at a pivot point. A forward end 151 a of the beam 150 has a head 152 connecting to the rod load extending from the well. The second or rearward end 151 b has a first bearing point 156 and has an end weight 160 disposed rearward of the first bearing point 156.
The crank arms 130 are connected to the prime mover 120 and are rotatable thereby about a crank point 132. The counterweights 136 are disposed on the crank arms 130. The pitman arms 140 are connected between the first bearing point 156 on the beam 150 and second bearing points or wrist pins 134 on the crank arm 130. The second bearing points 134 are disposed on the crank arm 130 between the counterweights 136 and the crank points 132.
The unit 100 includes these and other features similar to those disclosed previously with reference to FIG. 2A. In addition to having the zero-imbalance beam 150 with the end weight 150, the present configuration is a phased pumping unit where the crank arms 130 are designed with the counterweights 136 lagging behind the attachment point (i.e., wrist pins 134) of the pitman arms 140.
A geometric arrangement of the unit 100 is schematically depicted in FIG. 3B. As with the previous arrangement of FIG. 2B, a forward section 153 a of the forward end of the beam 150 and the head 152 disposed forward of the pivot point 116 has a forward weight (WF+WH), whereas a rearward section 153 b of the rearward end of the beam 159 and the end weight 160 disposed rearward of the pivot point 116 has a rearward weight (WR+WE). The forward weight (WF+WH) can be balanced relative to the rearward weight (WF+WE) about the pivot point 116 so that the benefits of the previous arrangement can be achieved. Accordingly, the weight value (WE) for end weight 160 is selected to achieve this balance by countering any increased weight from an increased length (A) of the forward beam end and from an increased size for the head 152 so the pumping unit 150 can be used for longer stroke applications.
In contrast to the previous arrangement, the second bearing points or wrist pins 134 are disposed offset at an angle (α) from the longitudinal axes 131 of the crank arms 130. In particular, the crankpin holes in a conventional pumping unit run parallel to the longitudinal axis 131 of the crank arm 130. For this phased unit 100, however, the crankpin holes for the wrist pin 134 are placed at an offset angle (α) from the longitudinal axis 131 of the crank arm 130. (The value of the offset angle (α) depends on the particulars of the implementation, such as the dimensions (e.g., KPRCAGHI) of the unit 100, rod loads, counterweight values, etc. In general, the offset angle (α) can be about 5-deg., but could be between 4-deg. and 15-deg. in most implementations.) Therefore, the counterweights 136 on the crank arms 130 lag behind the pivot connection (wrist pins 134) between the crank arms 130 and the pitman arms 140 as the crank arms 130 rotate clockwise. The phased pumping unit 100 must rotate clockwise. The length (P+) of the pitman arm 140 may be different than the previous arrangement due to the lagging counterweight (136).
Another geometric arrangement of the unit 100 is schematically depicted in FIG. 3C. This arrangement is similar to those discussed above with reference to FIGS. 2B and 3B. Again, a forward section 153 a of the forward end of the beam 150 and the head 152 disposed forward of the pivot point 116 has a forward weight (WF+WH), whereas a rearward section 153 b of the rearward end of the beam 159 and the end weight 160 disposed rearward of the pivot point 116 has a rearward weight (WR+WE). The forward weight (WF+WH) can be balanced relative to the rearward weight (WF+WE) about the pivot point 116 so that the benefits of the previous arrangement can be achieved. Accordingly, the weight value (WE) for the end weight 160 is selected to achieve this balance by countering any increased weight from an increased length (A) of the forward beam end and from an increased size for the head 152 so the pumping unit 150 can be used for longer stroke applications.
In addition to having the zero-imbalance beam 150 with the end weight 160, the present configuration is a phased pumping unit where the crank arms 130 are designed with the counterweights 136 lagging behind the attachment points (i.e., wrist pins 134) of the pitman arms 140. For example, similar to the previous arrangements, the second bearing point or wrist pin 134 is disposed offset at an angle (α) from a longitudinal axis 131 of the crank arm 130. In particular, the crankpin holes for this phased unit 100 are placed at an offset angle (α) from the longitudinal axis 131 of the crank arm 130. Therefore, the counterweights 136 on the crank arms 130 lag behind the pivot connection (wrist pins 134) between the crank arms 130 and the pitman arms 140 as the crank arms 140 rotate clockwise. (Again, the offset angle (α) can be about 5-deg. or between 4-deg. and 15-deg. in most implementations.) The phased pumping unit 100 must rotate clockwise. The length (P+) of the pitman arm 140 may be different than the previous arrangement due to the lagging counterweight (136).
In contrast to the previous arrangements, the gear reducer 124 for this unit 100 in FIG. 3B is placed further back from the walking beam pivot point (i.e., saddle bearing assembly 116). In other words, the crank point of the crankshaft 132 is situated vertically rearward below the bearing point 156 on the beam 150 when the beam 150 is situated horizontally. In particular and as noted previously, the gear reducer 124 has a slow-speed shaft—i.e., the crankshaft 132 about which the crank arms 130 rotate. For a conventionally situated reducer, the center of this slow-speed crankshaft would be situated relative to the unit's fulcrum point so that the crankshaft may sit directly under the center of the equalizer bearing shaft. In this phased pumping unit 100, however, the gear reducer 124 is situated further back from the fulcrum point 116. Therefore, the slow-speed crankshaft 132 of the gear reducer 124 on the phased unit 100 sits rearward of the equalizer bearing 156. The horizontal separation (I+) of the crank point 132 from the fulcrum point 116 may be different than the previous arrangement. In other words, the horizontal distance (I+) between the saddle bearing 116 and the crank point 132 is greater than the horizontal distance (C) between the saddle bearing 116 and the equalizing bearing 156. Again, the values of these horizontal distances (I+) and (C) depend on the particulars of the implementation, such as the other dimensions (e.g., KPRAGH) of the unit 100, rod loads, counterweight values, etc. In general, the horizontal distance (I+) can be greater in length than the beam's horizontal distance (C). In other words, the horizontal distance (I+) can be greater than approximately 10%) in length than the beam's horizontal distance (C). Such an arrangement dictates some of the other dimensions for the interconnected links (KPRC) of the unit 100.
As the geometries of Figs. Although not explicitly shown, the feature of the gear reducer 124 situated further back from the fulcrum point 116 (as in FIG. 3B) could be used with crankpin holes that are aligned along the longitudinal axis 131 of the crank arm 130 (as in FIG. 2B).
The foregoing description of preferred and other embodiments is not intended to limit or restrict the scope or applicability of the inventive concepts conceived of by the Applicants. It will be appreciated with the benefit of the present disclosure that features described above in accordance with any embodiment or aspect of the disclosed subject matter can be utilized, either alone or in combination, with any other described feature, in any other embodiment or aspect of the disclosed subject matter.
In exchange for disclosing the inventive concepts contained herein, the Applicants desire all patent rights afforded by the appended claims. Therefore, it is intended that the appended claims include all modifications and alterations to the full extent that they come within the scope of the following claims or the equivalents thereof.

Claims

What is claimed is:

1. A surface pumping unit operated by a prime mover for reciprocating a rod load for a downhole pump in a well, the unit comprising:

a frame disposed at surface and having a fulcrum point;

a beam being pivotable at the fulcrum point of the frame, the beam having first and second ends, the first end having a head connecting to the rod load extending from the well, the second end having a first bearing point and having an end weight disposed rearward of the first bearing point, a forward section of the first end of the beam and the head disposed forward of the fulcrum point having a forward weight, a rearward section of the second end of the beam and the end weight disposed rearward of the fulcrum point having a rearward weight, the forward weight being balanced relative to the rearward weight;

a crank arm connected to the prime mover and rotatable thereby about a crank point;

a counterweight disposed on the crankarm; and

a pitman arm connected between the first bearing point on the beam and a second bearing point on the crank arm, the second bearing point being disposed between the counterweight and the crank point.

2. The unit of claim 1, wherein the crank arm rotated by the prime mover about the crank point translates the pitman arm to oscillate the beam on the fulcrum point and reciprocates the rod load along the wellbore axis.

3. The unit of claim 1, wherein the frame comprises:

a base disposed at the surface; and

a post extending from the base to the fulcrum point along a line from vertical.

4. The unit of claim 1, wherein the beam defines a straight axis having first and second sections, the first section from the fulcrum point to a face of the head having a first length (A), the second section from the fulcrum point to the first bearing point having a second length (C);

and wherein the first length (A) is greater than the second length (C).

5. The unit of claim 1, wherein the fulcrum point comprises a saddle bearing; wherein the first bearing point comprises an equalizer bearing; and wherein the second bearing point comprises a crank pin bearing.

6. The unit of claim 1, further comprising:

another crank arm connected to the prime mover and rotatable thereby about another crank point; and

another pitman arm connected between another first bearing point on the beam and another second bearing point on the other crank arm,

wherein the pitman arms connect with an equalizer beam at the first bearing point.

7. The unit of claim 1, further comprising a gear reducer operably connecting the crank point to the prime mover.

8. The unit of claim 1, wherein the crank point is centered vertically below the first bearing point on the beam when the beam is situated horizontally.

9. The unit of claim 8, wherein the first bearing point is disposed at a first horizontal dimension (C) along the beam relative to the fulcrum point; and wherein the crank point is disposed at a second horizontal dimension (I) relative to the fulcrum point, the second horizontal dimension (I) being approximately equal to the first horizontal dimension (C).

10. The unit of claim 8, wherein the crank arm defines a longitudinal axis, the second bearing point being disposed along the longitudinal axis of the crank arm.

11. The unit of claim 8, wherein the crank arm defines a longitudinal axis, the second bearing point being disposed offset at an angle from the longitudinal axis of the crank arm.

12. The unit of claim 1, wherein the crank point is situated vertically rearward below the first bearing point on the beam when the beam is situated horizontally.

13. The unit of claim 12, wherein the first bearing point is disposed at a first horizontal dimension (C) along the beam relative to the fulcrum point; and wherein the crank point is disposed at a second horizontal dimension (I) relative to the fulcrum point, the second horizontal dimension (I) being greater than the first horizontal dimension (C).

14. The unit of claim 12, wherein the crank arm defines a longitudinal axis, the second bearing point being disposed along the longitudinal axis of the crank arm.

15. The unit of claim 12, wherein the crank arm defines a longitudinal axis, the second bearing point being disposed offset at an angle from the longitudinal axis of the crank arm.

16. A surface pumping unit operated by a prime mover for reciprocating a rod load for a downhole pump in a well, the unit comprising:

a frame disposed at the surface and having a fulcrum point;

a beam being pivotable at the fulcrum point of the frame, the beam having first and second ends, the first end having a head connecting to the rod load extending from the well, the second end having a first bearing point and having an end weight disposed rearward of the first bearing point;

a crank arm defining a longitudinal axis, the crank arm connected to the prime mover and rotatable thereby about a crank point;

a counterweight disposed on the crankarm; and

a pitman arm connected between the first bearing point on the beam and a second bearing point on the crank arm, the second bearing point being disposed between the counterweight and the crank point and being disposed offset at an angle from the longitudinal axis of the crank arm.

17. The unit of claim 16, wherein a forward section of the first end of the beam and the head disposed forward of the pivot point having a forward weight, a rearward section of the second end of the beam and the end weight disposed rearward of the pivot point having a rearward weight, the forward weight being balanced relative to the rearward weight about the pivot point.

18. The unit of claim 16, wherein the crank point is situated vertically rearward below the first bearing point on the beam when the beam is situated horizontally.

19. The unit of claim 18, wherein the first bearing point is disposed at a first horizontal dimension (C) along the beam relative to the fulcrum point; and wherein the crank point is disposed at a second horizontal dimension (I) relative to the fulcrum point, the second horizontal dimension (I) being greater than the first horizontal dimension (C).

20. A reciprocating pump system for a well, the system comprising:

a downhole pump disposed in the well; and

a pumping unit according to claim 1 or claim 16 disposed at the surface and coupled to the downhole pump by a rod string.