Patent Application
20190330964
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,
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 Sampson 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 a crank arm 44 having a counterbalance weight 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+I2)}
As is typical, the pump jack 30 as in
Apart from all of the complications downhole, the slanted wellhead and wellbore present problems for a traditional pump jack at surface. One configuration of a pump jack 30 for use with a slanted well having an inclined wellhead 13 is shown in
This configuration alters the geometry of the four-bar linkage of the pump jack 30 so that the polished rod 15 can align with the inclined wellhead 13. Unfortunately, the 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, diagnostics of the downhole rod pump because calculations for these features are typically based on the standard four-bar linkage (K-R-P-C).
Another configuration of a pump jack 30 for use with a slanted well having an inclined wellhead 13 is shown in
The forward section of walking beam 50 is fabricated so its longitudinal axis is angled to address the inclination of the wellhead 13. In this way, the radius A from the centerline of the center bearing 35 to the arcuate face 54 of the horsehead 52 is tangent to the inclined polished rod 15. As disclosed, the non-linear bent walking beam 50 is described as providing a simple and effective means of addressing the angled wellhead 13 while preserving the operating characteristics of a prior art pumping unit. As also disclosed, the beam 50 is fabricated with the bend 53 that closes matches the wellhead angle. As further disclosed, the rearward section of the walking beam 50 from the saddle bearing 35 to the equalizer bearing 55, and the four-bar linkage system embodied by the pump jack, remains unchanged relative to a prior art pump jack intended for vertical wells.
Although slant well pump jacks of the prior art may have some benefits, operators are continually striving to increase the versatility of pump jack systems to meet the challenges of various implementations. 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.
A surface pumping unit disclosed herein is for reciprocating a rod load for a downhole pump in a well. The well has a wellbore axis intersecting at an inclination relative to surface. The unit comprises a frame and a beam. The frame is disposed at the surface and has a fulcrum point. The beam has first and second ends and defines a bend therebetween. The first end is connected to the rod load extending from the well at the inclination. The beam is pivotable at a pivot on the fulcrum point of the frame, and the pivot is disposed between the bend and the first end of the beam.
In one further configuration, the frame comprises a base and a post. The base is disposed at the surface, and the post extends from the base to the fulcrum point along an axial line from vertical. The first end of the beam comprises a straight section at the pivot of the fulcrum point, and the straight section is angled to intersect the axial line of the post at an acute forward angle. Orientation of the post, the straight section, and the pivot support a load of the beam with a force along the axial line reducing bending stress on the post.
In another further configuration, the unit comprises a head disposed on the first end of the beam. The head has a face circumscribing a segment at a radius relative to the fulcrum point, and the segment is tangential to the angles for the inclination of the wellbore axis. The unit is disposed at one of a plurality horizontal offsets from an intersection of the wellbore axis with the surface, and the face disposed with the base at the horizontal offsets accommodates a plurality of angles for the inclination of the wellbore axis.
The face can have a top end and a bottom end. At least seventy-percent or greater of the face from the top end can tangentially intersect the rod load along the wellbore axis for a largest of the angles of the inclination; and at least seventy-percent or greater of the face from the bottom end can tangentially intersect the rod load along the wellbore axis for a smallest of the angles of the inclination.
In various arrangements, the fulcrum point is disposed at a first vertical height (H) above the surface and is disposed at a horizontal offset from an intersection of the wellbore axis with the surface. The pivot can comprise a saddle bearing. The first end of the beam can comprise a first straight section having a first length, the second end of the beam can comprises a second straight section having a second length, and the bend can define an angle between the first and second straight sections and inclining the first straight section downward toward the frame.
In further configurations, the unit further comprises a prime mover, a crank arm, and a pitman arm. The prime mover is disposed adjacent the frame, and the crank arm connected to the prime mover is rotatable thereby about a crank point. The crank point is disposed at a first (K) dimension relative to the fulcrum point. The pitman arm has a second (P) dimension and connected between a first bearing point on the crank arm and a second bearing point on the second end of the beam. The first bearing point is disposed at a third (R) dimension from the crank point, and the second bearing point is disposed at a fourth (C) dimension relative to the fulcrum point. Therefore, 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. In fact, the unit can have a pair of crank arms and pitman arms, and the pitman arms can connect with an equalizer bar at the second bearing point.
In various arrangements, the first bearing point comprises a crank pin bearing, and the second bearing point comprises an equalizer bearing. The crank arm comprises a counterweight disposed thereon, and the first bearing point is disposed between the counterweight and the crank point.
In the further configuration, the unit can be disposed at one of a plurality horizontal offsets from an intersection of the wellbore axis with the surface. In this way, the unit keeping the first, second, third, and fourth dimensions and disposed at the horizontal offsets can accommodate a plurality of angles for the inclination of the wellbore axis.
In the further configuration, the unit having the first, second, third, and fourth dimensions can operate at the inclination of the wellbore axis inclined from the surface comparable to a pumping unit having the first, second, third, and fourth dimensions that operates at a vertical wellbore axis.
According to the present disclosure, a surface pumping unit reciprocates a rod load for a downhole pump in a well. Again, the well has a wellbore axis intersecting at an inclination relative to surface. The unit comprises a base, a post, a beam, and a head. The base is disposed at the surface at one of a plurality horizontal offsets from an intersection of the wellbore axis with the surface. The post extends from the base to a fulcrum point along an axial line from vertical.
The beam has first and second ends and defines a bend therebetween. The beam is pivotable at a pivot on the fulcrum point of the frame. The pivot is disposed between the bend and the first end of the beam. The first end of the beam has a straight section at the pivot of the fulcrum point. The straight section is angled to intersect the axial line of the post at an acute forward angle; and
The head is disposed on the first end of the beam and is connected to the rod load extending from the well at the inclination. The head has a face circumscribing a segment at a radius relative to the fulcrum point. The segment is tangential to the angles for the inclination of the wellbore axis. The face disposed with the base at the horizontal offsets accommodates a plurality of angles for the inclination of the wellbore axis.
The present disclosure disclosed a reciprocating pump system for a well having a wellbore axis intersecting at an inclination relative to surface. 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 unit can include any of the various configurations outlined herein.
The foregoing summary is not intended to summarize each potential embodiment or every aspect of the present disclosure.
Referring now to
The pumping unit 100 includes a frame having a base 110 and a Sampson post 112. An actuator 120 is disposed on the base 110, a crank assembly is connected to the actuator 120, and a walking beam 150 is connected to the crank assembly and is supported by the Sampson posts 112 on the base 110. Structurally, the Sampson 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 Sampson 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 a prime mover 122, such as an electric motor or internal combustion engine, mounted on a pedestal above the base 110. A pump controller 125 monitors, controls, and records the pump unit's operation. Output from the motor 122 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 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. In turn, the two pitman arms 140 are connected to an equalizer bar 142, which is pivotally connected to the rear end 151b 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 151a of the walking beam 150. As is typical, the face 154 may have tracks or grooves for carrying a flexible wire rope bridle (not shown). At its lower end, the bridle (not shown) 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 an inclined wellhead for connection to downhole sucker rods and pump.
As is typical and best shown in
As the actuator 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 motor 122 and gearbox 124 rotates the crank arms 130, which causes the rearward end 151b of the walking beam 150 to move up and down through the pitman arms 140. Up and down movement of the rearward end 151b 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 151a.
During an upstroke, for example, the motor 122 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 motor 122 aided by the weight and load on the horsehead 154 rotates the crank arms 130 to raise the counterbalance weights 136.
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.
As can be seen in
As can best be see in
The geometric arrangement of the unit 100 is schematically depicted in
The face 154 connects to the polished rod extending along the wellbore axis WA from the wellhead at an inclination angle θ. The prime mover is not shown, but the crank arm 130 is connected to the prime mover at a crank point of the crank pin 132 and is connected to the pitman arm 140 at a first bearing point for the wrist pin 134. The pitman arm 140 is 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 142 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 SG. 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 SG.
In general, the unit 100 may have dimensions (C) and (A) dimension that are increased compared to a comparable vertical well pumping unit. The head 152 also has a face 154 that may be longer compared to a comparable vertical well pumping unit. However, various dimensions are adjusted proportionally so that the unit 100 can operate comparably to the kinematic four-bar linkage (KPRC) used for a vertical well pumping unit. In this way, the disclosed unit 100 can use many of the same or similar components (i.e., motor 122, gearbox 124, crank arms 130, counterweights 136, pitman arms 140, control unit 125, and the like) as used for a comparable vertical well pumping unit. Even the saddle bearing 116 and the equalizer bearing 156 can be the same or similar. This provides the unit 100 with flexibility to meet the needs of various pumping implementations.
The forward section 151a of the beam 150 comprises a first straight section having a first length, and the rearward section 151b of the beam 150 comprises a second straight section having a second length. In one example, the bend 153 defines a bend angle α□ of about 46-degrees between the first and second straight sections 151a-b, although the bend angle α can vary. The bend angle α can define the minimum inclination θmin of the pumping unit 100. In general, the first length of the forward section 151a is longer than the second length of the rearward section 151b.
Because the walking beam 150 defines the bend 153 between rearward and forward portions 151a-b and because the forward section 151a has the head 152, the beam 150 defines a center of gravity that is more forward heavy. The center of gravity location can vary, however, based on the mass of the beam 150 and how that mass is distributed along its length following from the head 152, the forward portion 151a, the bend 153, and the rearward portion 151b.
The unit 100 with the same dimensions (K, P, R, C & A) outlined above can be disposed at a range of horizontal offsets (O) to accommodate a range of inclination angles θ relative to the vertical surface S. In general, the offset (O) could be measured from the edge 111 of the base 110, or it can be measured from the vertical location of the fulcrum point 116 or from some other given point.
The chart below provides example inclination angles θ at offsets (O) measured from the edge 111 of the base 110.
As shown in
Turning now to
Line 161 shows the tangent to the inclined line 163 of the greatest inclination angle θmax, and line 164 shows the tangent to the inclined line 165 of the smallest inclination angle θmin. In general, the run area for the greatest inclination angle θmax preferably encompasses an arc 162 on the upper face 152 of at least 70% or greater (preferably about 80% or greater) of the total run area 160. Similarly, the run area for the smallest inclination angle θmin encompasses an arc 165 of at least 70% or greater (preferably about 80% or greater) of the total run area 160.
In the particular example shown, line 161 is the tangent for the largest inclination angle θmax of 56-degress, and line 164 is the tangent for the smallest inclination angle θmin of 46-degress. These two lines 161, 164 therefore define an arc of 10-degrees on the face 154 of the horsehead 152. Overall, the maximum run area 160 of the horsehead can define the arc 160 of about 51.4-degrees. Therefore, the run area for the largest inclination angle θmax encompasses the arc 162 of about 41.1-degrees—i.e., 20.7-degrees on either side of this point of tangency. Similarly, the run area for the smallest inclination angle θmin encompasses the arc 165 of about 41.1-degrees—i.e., 20.7-degrees on either side of the point of tangency.
Typically, as shown in
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.
