Patent Application
20180283146
Many hydrocarbon wells are unable to produce at commercially viable levels without assistance in lifting the formation fluids to the earth's surface. In some instances, high fluid viscosity inhibits fluid flow to the surface. More commonly, formation pressure is inadequate to drive fluids upward in the wellbore. In the case of deeper wells, extraordinary hydrostatic head acts downwardly against the formation and inhibits the unassisted flow of production fluid to the surface.
A common approach for urging production fluids to the surface uses a mechanically actuated, positive displacement pump. Reciprocal movement of a string of sucker rods induces reciprocal movement of the pump for lifting production fluid to the surface. For example, a reciprocating rod lift system 20 of the prior art is shown in
The production fluid F may not produce naturally reach the surface so operators use the reciprocating rod lift system 20 to lift the fluid F. The system 20 has a surface pumping unit 22, a rod string 24, and a downhole rod pump 50. The surface pumping unit 22 reciprocates the rod string 24, and the reciprocating string 24 operates the downhole rod pump 50. The rod pump 50 has internal components attached to the rod string 24 and has external components positioned in a pump-seating nipple 31 near the producing zone and the perforations 15.
As best shown in the detail of
As the surface pumping unit 22 in
On the following downstroke, the standing valve 70 closes as the standing ball 72 seats upon the lower seat 74. At the same time, the traveling valve 90 opens so fluids previously residing in the chamber 62 can pass through the valve 90 and into the plunger 80. Ultimately, the produced fluid F is delivered by positive displacement of the plunger 80, out passages 61 in the barrel 60. The moved fluid then moves up the wellbore 10 through the tubing 30 as shown in
Some subsurface pumps may be considerably long and may have a number of subcomponents coupled together with threaded connections. Additionally, some subsurface pumps can be installed in deep wells that may be deviated. The combination of issues involving long plungers, long stroke lengths, and/or deviations of the well can eventually damage the subsurface pump. For instance, various features on the subsurface pump may be susceptible to stresses that eventually lead to failure after repeated reciprocation on the plunger in the barrel.
As one example, grooved-type of plungers may be susceptible to bending fatigue. One grooved-type plunger has a series of grooves disposed circumferentially about the plunger. These grooves may be empty or may hold sealing rings. Either way, both of these groove features are used to help with lubrication/sand control. Unfortunately, these grooves act as stress risers when a bending moment is introduced, as is the case when the wellbore is deviated. Additionally and as noted previously, plungers may be made up of multiple subcomponents coupled together with box and pin threads. The couplings between subcomponents can also introduce high bending stresses due to the change in stiffness across the coupling locations.
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 subsurface pump for a reciprocating system comprises a barrel, a plunger, and at least one joint. The barrel has a first valve allowing fluid passage into the barrel and restricting fluid passage out of the barrel. The plunger has a plurality of plunger portions arranged longitudinally. The plunger is reciprocally disposed in the barrel and has a second valve. The second valve allows fluid passage into an interior of the plunger and restricts fluid passage out of the interior.
The at least one joint longitudinally interconnects at least two of the plunger portions together. The at least one joint provides fluid communication between the interior of the at least two plunger portions and allows lateral displacement between the at least two plunger portions relative to one another.
The at least one joint can include a first end connected to a first of the at least two plunger portions and can include a second end connected to a second of the at least two plunger portions. At least one of the first and second ends is integrally connected to a respective one of the first and second plunger portions, and/or at least one of the first and second ends is threadingly connected to a respective one of the first and second plunger portions.
In one arrangement, the at least one joint comprises a stem being flexible and interconnected between the first and second ends. This flexible stem can have a wall thickness, length, and material configured for the desired lateral displacement between the plunger portions to reduce fatigue on the plunger reciprocated in the deviated well.
In another arrangement, the at least one joint comprises an articulable coupling between the first and second ends. For example, the articulable coupling can include a first member at the first end having a knuckle and can include a second member at the second end having socket mated with the knuckle. A shaft is affixed inside the second member and has a pivot engaged with a seat defined inside the first member.
Overall, a first of the at least two plunger portions can include a seal component of the plunger providing at least a portion of a first seal with the barrel. A second of the at least two plunger portions can include another seal component of the plunger providing at least another portion of the first seal.
Alternatively, a second of the at least two plunger portions can include a filter component of the plunger. The filter component can include a filter disposed on the plunger between the first seal and a second seal of the plunger with the barrel. The filter separates the interior of the plunger from an annulus between the plunger and the barrel. Yet, the filter permits fluid passage between the interior and the annulus and restricts particulate in the interior from passing into the annulus. The filter may include a wire-wrapped screen at least partially disposed about the plunger.
More generally, the plurality of plunger portions can include an uphole seal component having an uphole seal, a downhole seal component having a downhole seal, and a valve component having the second valve. The uphole seal can use one or more wiper seals disposed outside the uphole seal component and engaging inside the barrel. For its part, the downhole seal can use a fluid seal formed with fluid disposed in the annulus between the barrel and the plunger or can use a wiper seal disposed between the barrel and the plunger.
The first valve of the barrel can include a check valve having a ball movable relative to a seat. Likewise, the second valve of the plunger can include a check valve having a ball movable relative to a seat. Other types of valves could also be used.
The disclosed subsurface pump can be used in a reciprocating rod system for a well. In addition to the subsurface pump, the system can include a surface unit reciprocating a rod in the well connected to the plunger of the pump. In operating the system to produce fluid in the well, fluid can be lifted in the well by reciprocating the plunger in the barrel disposed. Deviation in the reciprocation can be accommodated by laterally displacing at least two plunger portions of the plunger relative to one another with at least one joint longitudinally interconnecting the at least two plunger portions together.
The foregoing summary is not intended to summarize each potential embodiment or every aspect of the present disclosure.
At its downhole end, the barrel 110 has a standing valve 170, while the barrel 110 has an outlet 112 at its uphole end through which the pump rod 102 passes. The plunger 120 is disposed inside an interior 115 of the barrel 110. The plunger 120 defines an interior 125 as well and has a traveling valve 160.
The standing valve 170 permits fluid from the production tubing 30 to enter into the barrel's interior 115, but restricts fluid in the opposite direction. The traveling valve 160 permits fluid from the barrel's interior 115 (and especially a variable volume or chamber 114 between the valves 160 and 170) to enter the plunger's interior 125, but restricts fluid in the opposite direction. Reciprocation of the plunger 120 eventually allows for the volume of fluid above the traveling valve 160 to be lifted out of the barrel's outlet 112 and up the tubing 30.
As shown, the standing valve 170 can be a one-way valve, such as a check valve having a ball 172 movable relative to a corresponding seat 174. The traveling valve 160 can likewise be a one-way valve, such as a check valve having a ball 162 movable relative to a corresponding seat 164. Other types of one-way valves and check valves could be used, however.
A gap or annulus 113 is formed between the plunger 120 and the barrel 110, and the plunger 120 uses at least one seal to seal the annulus 113 with the barrel 110. In the present example, the plunger 120 using an uphole seal 123 and a downhole seal 127. For the uphole seal 123, more than one seal component 130A-B can be used. Each seal component 130A-B includes a mandrel 132 with an interior passage 135. Externally, the seal component 130A-B as shown here can use a mechanical seal having pressure-balanced wiper seals 134 or similar types of seals that are disposed in circumferential grooves about the outside of the seal component 130A-B to engage inside the barrel 110. During operation, the wiper seals 134 keep produced particulate uphole of the pump 100 from entering the annulus 113 between the plunger 120 and barrel 110.
The downhole seal 127 of the plunger 120 can be any type of suitable seal. For example, the downhole seal 127 can be a mechanical seal that allows for fluid slippage. As shown in
Typically, the inside surface of the barrel 110 and the outside surface of the plunger 130 have a tight clearance to create the fluid seal 127. The actual clearance can depend in part on the type of fluid to be encountered, such as heavy or light crude, expected particulate sizes, and other details of the pump 100 as discussed below. The fluid seal 127 can be a long hydrodynamic seal effective in extending the life of the pump 100.
Interposed between the seals 123 and 127, the plunger 120 can have one or more filter components 140. During operation, fluid within the plunger's interior 125 can pass through a filter 146 disposed in the interior 145 of the filter component's mandrel 142 and can pass into the annulus 113 through ports 148. To provide an external surface for the fluid seal 127 in the annulus 113, the plunger 120 can have one or more plunger components 150 coupled below the filter component 140. These components 140 and 150 can couple together and can couple to the seal component 130B and the traveling valve 160 in any acceptable manner, such as threaded connections as shown.
Although fluid can pass out of the filter component 140, the filter 146 restricts passage of at least some of the particulates inside the plunger 120 from passing into the annulus 113. The filter 146 can be a wire-wrapped screen, a perforated tubular portion, a mesh screen, or any suitable type of barrier, medium, or the like for restricting passage of particulate matter, such as sand, in downhole production fluid. Preferably, the filter 146 is a slotted, wire-wrapped screen having a circumferentially wound wire forming a number of slots. The wrapped wire can be profiled V-wire, which allows the slot's dimension to be precisely controlled. The narrower portion of the slotted openings preferably face the interior 145 of the mandrel 142 to help prevent particulate passing through the filter 146 from wedging in between the wires as it passes out to the annulus 113.
Produced fluid from the formation enters the production tubing 30 downhole of the pump 100. As the reciprocating rod system reciprocates the rod 24 attached to the plunger rod 102, the produced fluid is lifted above the pump 100 and is eventually produced at the surface through the tubing 30. During a downstroke by the pump rod 102, for example, the standing valve 170 closes. At the same time, the traveling valve 160 opens so fluid previously residing in the variable volume chamber 114 can pass through the open valve 160 and into the plunger's interior 125.
During the downstroke, the wiper seals 134 maintain a barrier between the uphole and downhole portions of the pump 100 and keep produced particulate above the pump 100 from entering the annulus 113 between the plunger 120 and the barrel 110. Head pressure is present inside the barrel 110 above and below the plunger 120, inside the plunger 120, and in the pressure-balance region outside the filter component 140 below the wiper seals 134. (As is known, head pressure refers to the pressure exerted by weight of the column of fluid above a given point.) Therefore, pressure is balanced across the wiper seals 134 so that there is no slippage (i.e., fluid does not pass between the seals 134 and the surrounding surface of the barrel 110 engaged thereby). At the same time, pressure is also balanced across the second fluid seal 127 in the annulus 113 so that there is no slippage either.
During the upstroke by the pump rod 102, the traveling valve 160 closes, and movement of the closed traveling valve 160 upward creates reduced pressure within the variable volume chamber 114. In turn, the standing valve 170 opens so production fluid and any particulate downhole of the pump 100 can be drawn into the pump's chamber 114. Head pressure is present inside the barrel 110 above the plunger 120 and in the pressure-balance region outside the filter component 140 below the wiper seals 134. As before, the wiper seals 134 are pressure-balanced so there is no slippage. In this way, the wiper seals 134 maintain the barrier between the uphole and downhole portions of the pump 100 and keep produced sand above the pump 100 from entering the annulus 113 between the plunger 130 and barrel 110.
During the upstroke, fluid slippage can occur in the annulus 113 between the inside of the barrel 110 and the outside of the plunger 120, and fluid passes from the interior 125 of the plunger 125 to the annulus 113 through the filter 146 to maintain the hydrodynamic seal 127. As a result, a pressure differential occurs, reducing the pressure in the expanding pump chamber 114 to draw new production fluid and particulate into the barrel 110 past the standing valve 170.
As noted above, slippage fluid is filtered through the filter 146 on the upstroke. In particular, the filter 146 allows some of the lifted fluid in the plunger's interior 125 to pass through and enter the annulus 113 to maintain the hydrodynamic seal 127. Yet, the filter 146 limits the size of particulate matter that can enter the hydrodynamic sealing annulus 113. In this way, larger particulates cannot enter the annulus 113 and abrade the surfaces, which would compromise the pump's operation. The annulus 113 is preferably sized larger than the particulate matter permitted to pass through the filter 146 so that the screened matter can pass through the hydrodynamic sealing annulus 113 without abrading the sealing surfaces forming the fluid seal 127. To achieve this, the average clearance of the annulus 113 is preferably equal to or greater than the width of the openings (i.e., slots) in the filter 146 and any particulates that the filter 146 may pass.
The upstroke and down stroke cycles are repeated, causing fluid to be lifted upward through the production tubing 30 and ultimately to the earth's surface. Flow through the pump 100 continuously washes the interior surface of the filter 146, which can keep it from fouling. With this arrangement, sandy fluids produced from the formation will produce less wear on the sealing surfaces and will be produced with the well fluids. Being able to lift the sand with the production fluids means that any produced sand below the pump 100 will not foul a downhole screen or fill up the rathole.
As noted previously, the filter 146 installs at the pressure-balancing region of the plunger 120. The pump 100 can be constructed with the filter 146 integrally formed as part of the filter component 140, or a separate screen assembly can be installed as an add-on. The filter component 140 can be a subcomponent that couples upper and lower sections of the plunger 120 together. The pump 100 can extend the life of a reciprocating rod lift system, reduce well maintenance costs, and increase overall production of an oil and gas well.
As can be seen in this example, the subsurface pump 100 is considerably long and has a number of subcomponents 130, 140, 150, and 160 coupled together with threaded connections. Additionally, the subsurface pump 100 can be installed in a deep well that may be deviated. The combination of issues involving the long plunger 120, long stroke length, and/or deviation of the well can eventually damage the subsurface pump 100. In fact, various features on the subsurface pump 100 may be susceptible to stresses that eventually lead to failure after repeated reciprocation on the plunger 120 in the barrel 110.
For example, the uphole seal 123 may be susceptible to bending fatigue due to the series of grooves disposed circumferentially about the plunger 120 for holding the wiper seals 134. As noted, these grooves act as stress risers when a bending moment is introduced, as is the case when the wellbore is deviated. Additionally and as noted previously, the plunger 120 is made up of multiple subcomponents 130, 140, 150, and 160 coupled together with threaded connections. The couplings between these subcomponents 130, 140, 150, and 160 can also introduce high bending stresses due to the change in stiffness across the coupling locations.
To deal with these and other possible challenges associated with the pump 100, the disclosed plunger 120 includes one or more joints 200 according to the present disclosure disposed at point(s) along the longitudinal length of the plunger 120. As shown in the example of
In general, the joint 200 is a flexible coupling or articulable coupling for the plunger 120. In the present context, the joint 200 used with the seal components 130A-C can effectively allow for an increased longitudinal length of sealing area for the first seal 123, while avoiding a high concentration of vulnerable transitions susceptible to the forms of fatigue that result from the grooves and threaded couplings of the more than one seal component 130A-B.
Moreover, the joint 200 can help mitigate damage to the plunger 120 caused by deviations of the barrel 110 in the well. For example,
Particular details of the joint 200 in the present example are provided in
The flexible stem 203 has a wall thickness T defined by the difference between the stem's inner and outer diameters ID, OD. The inner diameter ID is generally dictated by the dimensions of the pump (100) and the overall flow area for the pump (100). The thickness T as well as the overall length L and the material of the joint 200 can each be selected and configured for a desired strength, stiffness, flexure, and the like to meet the particular location of the joint's use on the plunger (120) and to suit the particular implementation of the plunger (120).
Overall, the outer diameter OD of the stem 203 is smaller than the overall plunger's outer dimension, and large transitions 207 are preferably used between the change in dimensions between the ends 202, 204 and the stem 203 to reduce stress concentrations. As will be appreciated, the thin wall and the reduced outer dimension of the joint's stem 203 allow for much greater flexibility and lower stress. Sufficient length of the joint 200 can allow for low-stress cycling and can help reduce fatigue failure. The large radius at the transitions 207 is selected to reduce high stress concentration. Finally, the surfaces of the joint 200 can be shot-peened or treated in other ways and the material of the joint 200 can be select to increase the bending fatigue.
As noted above, the joint 200 can interconnect any one of the various subcomponents of the pump's plunger (120). In
Moreover,
In previous embodiments, the joint 200 was flexible. Other types of joints can be used. In particular,
Particular details of the joint 300 in the present example are provided in
In general, the articulable coupling of the joint 300 can use a configuration of a ball and a socket, a swivel, and the like that allow for fluid communication through the joint 300 and provide coupling under compressive and tensile loads. In the present example, lapped surfaces on the members 310, 320 form a knuckle 312 and a socket 322 mated together to provide a pivot and seal. Internally, the joint 300 has a pivot shaft 330 affixed with threads 332 inside the lower member 320. A pivot or ball 331 on the head of the shaft 330 fits against a lapped seat 314 inside the upper member 310 and provides a pivot and seal. A thrust washer 316 supported by a snap ring 315 provides a face contact for the threaded connection of the upper member 310 with a plunger subcomponent (not shown) of the plunger (120). The internal and external pivot connections enable the members 310, 320 to articulate relative to one another, but to also stay connected in the pushing and pulling experienced between the members 310, 320 when the plunger (120) is reciprocated.
The joint 300 can be configured with sufficient length and material to allow for low-stress cycling and can help reduce fatigue failure. Features of the joint 300 can be selected to reduce high stress concentration and increase the bending fatigue. Finally, features can be included to enhance the seals of the joint 300 in light of potential wear.
As will be appreciated with the benefit of the present disclosure, the teachings of the present disclosure and the disclosed joint can be used with any number of types of subsurface plungers. Accordingly, even though the discussion may have provided examples of multiple sections of a plunger assembly for a sand tolerant pump, the teachings of the present disclosure and the disclosed joint can also be used in conjunction with straight, non-grooved plungers and without a filter to reduce stresses at the plunger connections and/or side loading within the barrel.
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.
