Patent Grant
9689242
Plungers are employed to facilitate removal of gas from oilfield wells, addressing challenges incurred by “liquid loading.” In general, a well may produce liquid and gaseous elements. When gas flow rates are high, the gas carries the liquid out of the well as the gas rises. However, as well pressure decreases, the flowrate of the gas decreases to a point below which the gas fails to carry the heavier liquids to the surface. The liquids thus fall back to the bottom of the well, exerting back-pressure on the formation, and thereby loading the well.
Plungers alleviate such loading by assisting in removing liquid and gas from the well, e.g., in situations where the ratio of liquid to gas is high. In operation, the plunger descends to the bottom of the well, where the loading fluid is picked up by the plunger and is brought to the surface as the plunger ascends in the well. The plunger may also keep the production tubing free of paraffin, salt, or scale build-up.
Embodiments of the disclosure may provide a plunger that includes a body having an upper end, a lower end, a bore extending axially from the upper end to the lower end, and a port therein that is in communication with at least a portion of the bore, and an obstructing member positioned in the bore, with the obstructing member including a valve stem. The obstructing member is movable between a closed position, in which the obstructing member substantially prevents fluid flow through the bore from the port to the upper end, and an open position, in which fluid flow through the bore from the port to the upper end is permitted. The plunger also includes an end nut connected to the lower end of the body, and a clutch assembly including a plurality of arcuate members that are positioned at least partially around and configured to engage the valve stem to impede movement thereof, with the clutch assembly being positioned at least partially within the end nut.
Embodiments of the disclosure may also provide a bypass valve assembly that includes a valve cage defining a bore extending axially therethough and a plurality of ports extending radially and communicating with the bore, an end nut received partially in the bore and coupled to the valve cage, and an obstructing member including a valve stem receivable through the end nut, and a head positioned in the valve cage, with the head being configured to be retained in the valve cage and to be movable between the end nut and the seat. The valve stem defines a helical groove extending along at least a portion of an outside surface thereof. The bypass valve assembly also includes a clutch assembly disposed at least partially around the valve stem and positioned within the bore of the valve cage. The clutch assembly having a split bobbin and at least one tension member disposed around the split bobbin. The at least one tension member is configured to press an inner surface of the split bobbin into engagement with the outside surface of the valve stem, to resist movement of the obstructing member.
Embodiments of the disclosure may also provide a gas-lift plunger that includes a unitary body having an upper end, a lower end, a bore extending axially therein, and a tapered bypass cage defining a port radially therein that is in communication with at least a portion of the bore, with the bore defining a seat therein. The plunger also includes an obstructing member positioned in the bore, and including a valve stem and a head. The obstructing member is movable between a closed position, in which the head engages the seat and substantially prevents fluid flow through the bore from the port to the upper end, and an open position, in which the head is separated from the seat such that fluid flow through the bore from the port to the upper end is permitted. The plunger also includes an end nut received at least partially into to the lower end of the body. The valve stem extends through the end nut at least when the obstructing member is in the open position, and wherein the end nut defines a window extending laterally therein. The plunger further includes a clutch assembly having a plurality of arcuate segments and a tension member positioned around the plurality of arcuate segments. The clutch assembly is aligned with the window and positioned at least partially within the end nut. The valve stem of the obstructing member is received through clutch assembly at least when the obstructing member is in the open position. The clutch assembly is configured to impede movement of the obstructing member by applying a radially-inward force on the valve stem.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present teachings, as claimed.
The accompanying drawing, which is incorporated in and constitutes a part of this specification, illustrates an embodiment of the present teachings and together with the description, serves to explain the principles of the present teachings. In the figures:
It should be noted that some details of the figure have been simplified and are drawn to facilitate understanding of the embodiments rather than to maintain strict structural accuracy, detail, and scale.
Reference will now be made in detail to embodiments of the present teachings, examples of which are illustrated in the accompanying drawing. In the drawings, like reference numerals have been used throughout to designate identical elements, where convenient. In the following description, reference is made to the accompanying drawing that forms a part thereof, and in which is shown by way of illustration one or more specific example embodiments in which the present teachings may be practiced.
Further, notwithstanding that the numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein are to be understood to encompass any and all sub-ranges subsumed therein.
Embodiments of the present disclosure, in general, provide a gas lift plunger apparatus, including a bypass valve assembly that includes a clutch assembly-controlled “dart” or valve stem that reciprocates within a bypass valve “cage” and provides a mechanism for sealing the fluid passages through the bypass valve. One of the functions of the bypass valve is to allow fluid to flow through the valve in a controlled manner to control descent of the plunger assembly to the bottom of the well. Another function of the bypass valve assembly is to switch the valve configuration to seal the passages that allow the flow-through of fluid so that the plunger acts as a piston to seal the well bore and permit the gas pressure in the well to force the piston and accumulated fluids above it to the surface so that production from the well can resume.
Further, certain embodiments disclosed herein may include design features that improve the performance and durability of the bypass valve assembly in a gas lift plunger. For example, descent of the plunger assembly may be faster and/or better controlled, which may reduce shut-in time, e.g., approximately in half, thus more quickly restoring the well to production. Moreover, the superiority of the valve stem and clutch assembly configuration that is disclosed herein, which enables the switch from plunger bypass/descent to gas lift/ascent at the bottom of the well, is confirmed by performance in the field. In addition, the reliability and durability of the plunger and the bypass valve assembly is extended by the features to be described herein, thereby reducing downtime and maintenance costs.
To achieve the aforementioned advantages, the following features, among others, may be used in combination in the bypass valve assembly described herein: (a) elongated bypass openings or ports that are relieved at the upper and lower ends at an angle to reduce turbulence and improve flow as the plunger descends, providing a smoother and a more rapid descent; (b) helical disposition of the bypass openings around the body of the bypass valve assembly to impart a torque to the plunger, causing it to spin within the well casing as it descends, ensuring more uniform wear and longer life while providing a smoother descent; (c) a valve stem clutch assembly with a tension member (e.g., a spring or elastomeric band) that is more resistant to high temperatures and corrosive chemicals than metal and thus much less prone to failure; (d) calibrated surface roughness of the valve stem surface to improve the friction characteristics of the valve stem clutch assembly as it arrives at the bottom of the well and configures the plunger for its ascent to the surface; (e) machined grooves on the inner surface of the clutch assembly bobbin to allow sand particles to be flushed away from within the clutch assembly, thereby preventing undesired lock-up; and (f) shortened taper of the upper end of the plunger body that utilizes the improved bypass valve assembly, to ensure a more complete seal with minimum leakage of production fluids during ascent of the plunger to the surface.
Variations in the above features are contemplated to adapt the bypass valve assembly to different well circumstances. For example, the number of bypass openings or slots may be varied to provide different flow rates. The tension in the tension member of the clutch assembly may be varied or adjusted to adapt the clutch assembly clamping force to different descent velocities as the plunger contacts the bumper at the well bottom. The helical pitch may be varied within narrow limits to control the amount of spin imparted to the plunger. The profile of the machined grooves in the clutch assembly bobbin may be varied to accommodate different sand particle sizes. The surface roughness of the valve stem may be varied to optimize the friction applied by the clutch assembly. The tapered profile of the plunger body at the upper end may be varied to optimize ascending performance with different fluid viscosities, etc. Persons skilled in the art will understand that the bypass valve assembly described herein—the assembly of the cage, valve stem and clutch assembly—may be constructed in a variety of combinations of the above features and interchanged with other combinations to suit particular conditions of individual oil or gas wells. For example, the plunger and bypass valve assembly may be produced in several diameters for use in different size well tubing. Also, different length plungers may be provided. For example, a shorter bypass plunger is better able to negotiate well tubing that have curves or elbows, and because of its lower weight, it places less stress on the bumper spring at the bottom in wells that are relatively dry. A longer casing falls more easily through more fluid and provides a better sealing action. This adaptability is yet another advantage of the present invention. As is well known, performance of a gas lift plunger may be reduced if the configuration of the plunger is not well-matched to the conditions of a particular well.
One component of the clutch assembly, as mentioned above, is the tension member. In this description the use of the singular form of the term “tension member” is intended to mean that the tension member may be made of a single piece, or may be of multi-piece construction. For example, the tension member may be made of one or more resilient bands, which may be fabricated of an elastomeric material, a broad category of synthesized polymer materials that are commonly known as synthetic rubber. In another embodiment, the tension member may be made of one or more springs. The tension member may be configured to resist deformation or destruction in the presence of relatively high temperatures. Further, the tension member may resist corrosion and have high elasticity and reversibility (i.e., ability to return to and maintain its unstressed or relaxed configuration after being stressed). Some examples of materials for elastomeric embodiments of the tension member include neoprene, buna-N, respectively polychloroprene and acrylonitrile butadiene. An alternative is hydrogenated nitrile rubber. Another example is a fluoroelastomer such as a fluoronated hydrocarbon better known as VITON®, a registered trademark of the E. I. DuPont de Nemours and Company or its affiliates of Wilmington, Del., USA. In particular, the tension member may, for example, be made from an elastomeric material having a Shore A durometer of 60 to 90, e.g., a Shore durometer of 75 on the A scale. In some applications where the band(s) of the tension member are thicker or wider (greater cross sectional area), the durometer figure may be reduced. Similarly, if the band(s) of the tension member are thinner or narrower, the durometer figure thereof may be increased.
When installed on the valve stem, the split bobbin segments are disposed around the valve stem shaft, held in a clamping action against the valve stem shaft by the action of the tension member. The clamping force provided by the tension member may resist by friction of the bobbin segment against the valve stem the movement of the valve stem through the clutch assembly. This friction arises because of the clamping force from the tension member and the predetermined surface roughness formed into the surface of the valve stem shaft along the greater portion of its length. The function of the clutch assembly is to ensure that the valve stem remains in either (a) the lower-most position within the valve cage during descent of the plunger so that the plunger will fall freely through the fluid in the well casing and cause it to rotate smoothly during the descent; and (b) the upper-most position within the valve cage during ascent of the plunger to seal the bypass valve assembly so that the gas pressure in the well will cause the plunger to rise through the well casing, pushing the production ahead of it. The clutch assembly enables the valve stem to be held in the appropriate position during descent and ascent, and also to change the position of the valve stem from the lower-most position to the upper-most position when the plunger reaches the bottom of the well to configure the plunger for its ascent.
Turning now to the specific, illustrated embodiments,
The rotary bypass valve assembly 14 includes a valve cage 30, and an end nut 34, and a valve stem 102. The body 32 of the valve cage 30 may be threaded (see
As also shown in the cross section view of
Continuing with
Materials for fabricating the plunger 10 described herein include type 416 heat-treated stainless steel for the bypass valve stem 102 and the clutch assembly bobbin segments 72A, 72B. The remaining parts (plunger body 16, valve cage 30, and end nut 34) may be fabricated of type 4140 heat-treated alloy steel. In other embodiments, the 416 heat-treated stainless steel may be used to fabricate all of these parts. Both materials are readily available as solid “rounds” in a variety of diameters, as is well known in the art.
This angle results in an inward slope of the ends 54, 56 of the port 46 with both ends 54, 56 oriented toward the upper end 18 of the bypass plunger 10 as it is positioned within a well casing. This relief of the ends 54, 56 of the port 46 facilitates the flow of fluid through the port(s) 46 as the bypass plunger 10 falls through the well casing by gravity. In other embodiments, the angle may be varied to suit a particular implementation of the bypass valve assembly 14. For example, the angles may be different at opposite ends of the port(s) 46, the angles may be larger or smaller acute angles relative to the longitudinal axis 60, the angled surfaces may be rounded in profile for even smoother flow through the port(s) 46, etc. An additional relieved area, called ramp 58, further smooths the path for fluid flow at the lower end 54 of each port 46.
The surface of the ramp 58 shown in
Continuing with
The combination of the helical orientation of the ports 46, e.g., disposed at several uniform radial positions around the body of the valve cage 30, each having the relieved ends (ramps) 54, 56, 58, provides a rotary gas lift plunger that outperforms other bypass plungers by providing smoother, faster descent along with more uniform wear and extended life in the field.
Continuing with
Also depicted in
As noted above, in at least one embodiment, the tension member 76 may be constructed from a synthetic rubber material. In such an embodiment, the tension member 76 may be impervious to the corrosive effects of most of the materials in the fluids found in oil and gas wells. As noted above, the tension member 76 may be fabricated from a synthetic rubber material having a durometer of between 60 and 90 on the Shore “A” Scale. Such material may provide tension when the tension member 76 is stretched over the rims 82, 84 of the split bobbin 72, applying a radially-inward force on the split bobbin 72 so as to secure the clutch assembly 70 around the valve stem 102. In some embodiments, the clutch assembly 70 is designed to resist a linear pull on the valve stem 102 of approximately 2.8 to 3.6 lbs. in this example, although adjustments to the tension may generally vary from 1.0 to 6.0 lbs. in other examples. The clutch assembly 70 may also be tailored to provide higher clamping forces. The performance of the clutch assembly 70 may also be dependent on the finish applied to the valve stem 62, as will be described below.
In other embodiments, the split bobbin may be lengthened to cover a greater portion of the valve stem 102. Further, the bobbin may be split into three or more segments (not shown). The split bobbin 132 illustrated in
Continuing with
Also depicted in
Returning now to
The body 1002 may further define a bypass valve cage 1006, extending at least partially from the lower end 1003B to the wipers 1004. The cage 1006 may be tapered inward, e.g., reducing in outer diameter as proceeding toward the lower end 1003B. Further, the cage 1006 may define ports 1008 therethrough, which may be shaped as elongated slots and may extend generally along a helical path to assist in rotary movement of the plunger 1000 during use, as explained above. An end nut 1010 may be coupled to the lower end 1003B of the body 1002 (e.g., to the cage 1006). The end nut 1010 may be threaded into the lower end 1003B and crimped, welded, pinned, or otherwise secured in place so as to prevent the end nut 1010 from backing out of connection with the body 1002.
An obstructing member 1102 may be positioned in the bore 1100. The obstructing member 1102 may have a head 1104 and a valve stem 1106, with the valve stem 1106 extending through a bore 1107 of the end nut 1010. Such obstructing members 1102 may be known as “darts” in some applications.
The obstructing member 1102 may be able to move between an open position and a closed position. In the closed position, as shown, the head 1104 may engage a tapered seat 1108 defined by the body 1002 in the bore 1100, e.g., above the ports 1008. When engaging the seat 1108, the head 1104 may prevent or at least obstruct fluid from flowing through the port 1008, up through the bore 1100, and out the upper end 1003A. The obstructing member 1102 may also be able to slide downwards into the open position, advancing the valve stem 1106 through the end nut 1010, displacing the head 1104 from the seat 1108. When the head 1104 is separated from the seat 1108, fluid flow may be permitted from the ports 1008, through the bore 1100, and out of the upper end 1003A. The head 1104 may be too large to fit through the bore 1107 of the end nut 1010, providing an end range for movement of the obstructing member 1102 away from the seat 1108.
When the obstructing member 1102 is in the open position, permitting fluid flow through the plunger 1000, the plunger 1000 may descend through fluid in the well. In this position, the obstructing member 1102 may protrude through the end nut 1010 in the open position. Thus, the obstructing member 1102 may reach a lower terminus of descent in the production tubing before the body 1002. Upon reaching such lower terminus, the obstructing member 1102 may be forced upwards in the bore 1100, e.g., by the inertia of the still-descending body 1002, into engagement with the seat 1108, thereby moving the obstructing member 1102 back to its closed position. The obstructing member 1102 may remain in the closed position as pressure builds below the plunger 1000, eventually forcing the plunger 1000 upward, toward an upper terminus, whereupon the obstructing member 1102 may be moved back to the open position to restart the cycle.
The end nut 1010 may include a clutch assembly 1110, which may impede the movement of the obstructing member 1102 between the open and closed positions. The clutch assembly 1110 may include two or more arcuate bodies (e.g., similar to the split bobbin segments discussed above), which may, when assembled, extend around the valve stem 1106. The clutch assembly 1110 may also include one or more tension members, such as one or more resilient springs, bands, snap-rings, tension rings, or the like, which may apply a radially-inward gripping force on the valve stem 1106. The gripping force may result in friction that resists relative movement between the clutch assembly 1110 and the valve stem 1106. In some embodiments, the outer diameter surface of the valve stem 1106 and/or an inner surface of the clutch assembly 1110 may include grit, teeth, a roughened-surface, or other features tending to increase the coefficient of friction between the clutch assembly 1110 and the valve stem 1106.
The clutch assembly 1110 may be received into a window 1200 formed laterally in a portion of the shank 1208 of the end nut 1010. The end nut 1010 may thus be unitary, while providing for a lateral assembly of the clutch assembly 1110 into position therein. In an embodiment, the window 1200 may be arcuate in shape, e.g., extending about 180 degrees (although larger or small angular intervals are contemplated) and may intersect with the bore 1107, e.g., providing an opening through the clutch assembly 1110 into the bore 1107. A recess 1202 may be defined in the end nut 1010, e.g., within the shank 1208, and aligned with the window 1200. In an embodiment, the recess 1202 may extend circumferentially between the circumferential ends of the window 1200. Accordingly, when the clutch assembly 1110 is received into the window 1200, at least a portion of at least one of the arcuate members thereof may be aligned with (e.g., extend at least partially through) the window 1200, while at least another portion of at least one of the arcuate members may be received into the recess 1202.
The end nut 1010 may also include a thread relief 1204, e.g., in the shank 1208, proximal to the head 1206. The lower end 1003B of the body 1002 may be pressed (e.g., crimped) into the thread relief 1204, so as to prevent the end nut 1010 from backing out of the threaded connection with the body 1002.
A tension member 1220 may be received around the clutch assembly 1110. The tension member 1220 may apply a radially inward force on the clutch assembly 1110, causing the clutch assembly 1110, which may be made of two or more arcuate members as explained above, to press against the valve stem 1106 of the obstructing member 1102. The tension member 1220 may be an elastomeric band, as shown, but in other embodiments, may be two or more bands, may be a spring (e.g., composite or metallic), or may be otherwise formed as any suitable resilient member capable of performing the aforementioned function.
While the present teachings have been illustrated with respect to one or more implementations, alterations and/or modifications may be made to the illustrated examples without departing from the spirit and scope of the appended claims. In addition, while a particular feature of the present teachings may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular function. Furthermore, to the extent that the terms “including,” “includes,” “having,” “has,” “with,” or variants thereof are used in either the detailed description and the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.” Further, in the discussion and claims herein, the term “about” indicates that the value listed may be somewhat altered, as long as the alteration does not result in nonconformance of the process or structure to the illustrated embodiment. Finally, “exemplary” indicates the description is used as an example, rather than implying that it is an ideal.
Other embodiments of the present teachings will be apparent to those skilled in the art from consideration of the specification and practice of the present teachings disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the present teachings being indicated by the following claims.
This application is a continuation-in-part of U.S. patent application Ser. No. 14/754,382, filed on Jun. 29, 2015, which is a continuation of U.S. patent application Ser. No. 13/871,642, filed on Apr. 26, 2013, which claims priority to U.S. Provisional Patent Application Ser. No. 61/720,451, filed on Oct. 31, 2012. Further, this application claims priority to U.S. Provisional Patent Application No. 62/416,808, which was filed on Nov. 3, 2016. Each of these priority applications is incorporated herein by reference in its entirety.
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| Number | Date | Country | |
|---|---|---|---|
| 20170107802 A1 | Apr 2017 | US |
| Number | Date | Country | |
|---|---|---|---|
| 61720451 | Oct 2012 | US | |
| 62416808 | Nov 2016 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13871642 | Apr 2013 | US |
| Child | 14754382 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14754382 | Jun 2015 | US |
| Child | 15395548 | US |
