Inverted Tail Plug and Assembly for Gas Lift Valve

This application claims priority to provisional patent application Ser. No. 63/638,282 filed May 13, 2024, which is fully incorporated herein by reference.

Embodiments of the subject matter disclosed herein relate to an improved tail plug and assembly for a gas lift valve for use in oil and gas wells.

Those skilled in the art know that gas lift mandrels and valves play a crucial role in enhancing oil and gas production from wells, particularly in challenging conditions where traditional methods may fall short. These systems utilize the injection of gas to lighten the hydrostatic column of fluid in the wellbore, thereby reducing the pressure required to lift fluids to the surface. This method is especially beneficial in wells with low reservoir pressure or high fluid viscosity, where conventional pumping techniques may struggle.

At the core of gas lift systems are mandrels, which are tubular devices installed at various depths in the well. These mandrels serve as anchor points for the gas lift valves, which control the injection of gas into the produced fluids. The design of the mandrel allows for easy installation and retrieval of the valves, facilitating maintenance and adjustments without needing to pull the entire tubing string. This flexibility is a significant advantage in maximizing production efficiency and minimizing downtime.

The gas lift valves are strategically positioned within the mandrels to regulate gas flow based on the relative pressure between lift gas injected into the well and pressure and fluid levels in the well itself. When the reservoir pressure drops or when fluid levels are insufficient for natural flow, the valves can open to allow gas to enter the wellbore. This injection reduces the density of the fluid column, enabling the hydrostatic pressure to be overcome more easily. As a result, the mixture of gas and fluid can be lifted to the surface with less energy.

A key benefit of using gas lift systems is their adaptability. Operators can adjust the amount and timing of gas injection based on real-time data from the well. This ability to dynamically control production allows for optimization based on varying reservoir conditions, which can significantly improve recovery rates. In essence, gas lift systems can be tailored to fit the specific characteristics of a well, leading to enhanced production efficiency.

Another advantage of gas lift technology is its lower operational costs compared to other artificial lift methods. Unlike electric submersible pumps (ESPs) or rod pumps, gas lift systems do not require extensive electrical infrastructure or complex mechanical components. This simplicity translates to reduced maintenance costs and fewer failures, making gas lift an attractive option for operators seeking to minimize expenses while maximizing output.

Moreover, gas lift systems can be deployed in environments where other artificial lift methods may be impractical. For instance, in offshore applications or remote locations with limited access to power sources, gas lift provides a reliable alternative that can be implemented with minimal logistical challenges. This versatility enables operators to extend the productive life of their wells and make the most of available resources.

As the oil and gas industry continues to evolve, the integration of advanced monitoring and control technologies with gas lift systems offers evolving possibilities. By incorporating sensors and real-time data analytics, operators can achieve even greater precision in managing gas injection and production rates. This integration can lead to improved recovery factors and more efficient use of reservoir resources, ultimately enhancing the economic viability of oil and gas projects.

Heretofore, however, gas lift valves have suffered leaks that diminish the efficiency and operability of the valves themselves. As those skilled in the art know, the ability of a gas lift valve to maintain a predetermined (or set) pressure level is important to the efficient operation of the valve in a well. Indeed, beyond mere inefficiencies, valve failures can result in costly delays and equipment costs if the valve(s) must be replaced.

are perspective views of a gas lift valve. The top or upper portion of the valve, i.e., the portion of the valve closer to the surface of the well when installed, is identified at, whereas the bottom or lower portion of the valve, i.e., the portion of the valve closer to the bottom of the well when installed, is identified at. Those skilled in the art will appreciate how such valves are inserted, retrieved, and operate in a well.

illustrates a cross-section of an exemplary, prior art gas lift valve. As those skilled in the art will appreciate, such valves include (among other components) gas chamber, gas injection valve core, and tail plug. The gas lift valve is “charged” to a predetermined pressure level by injecting a gas into gas chambervia gas injection valve core, i.e., when tail plugis removed from gas lift valve, thereby providing a gas charging system access to gas injection valve core.

As described above, although it is desirable and important that gas chamberremain charged to its predetermined pressure level, such prior art gas lift valves can suffer from leakage of gas/pressure from chamber, principally on a path past gas injection valve coreand tail plugand on to the ambient outside gas lift valve. This gas/pressure leakage can occur despite efforts to design gas injection valve coreand tail plugto prevent such leakage. Reasons for the leakage can vary, including operators not properly torquing tail plugin place.

As shown in more detail inand in(which is an enlarged version of detail A in), prior art gas lift valveincludes gas injection valve coremounted in the body of gas lift valve. Since these valve cores are known to be a potential source of leakage from gas chamber, tail plugis used to further prevent such leakage as well as protect valve core. As shown and described for the prior art device shown in, tail plugis inserted into the bore of the gas valve using a straight thread on the lower end of tail plug. This further serves to inhibit leakage from gas chamberto the ambient. To prevent leakage of gas even further (across the interface between tail plugand the bore of gas valve), O-ring sealand crush washerare deployed, as best shown in. As those skilled in the art appreciate, the O-ring seeks to create an airtight boundary across which it is difficult for gases/liquids to pass, whereas the crush washer seeks to serve the same purpose by its deformations filling leak spots/paths when the tail plug is installed and tightened into place to a degree that the washer crushes between the tail plug and body of valve.

Despite these efforts, it has been observed that gas/pressure still can leak from gas chamberthrough and/or around gas injection valve coreand across the interface between the bore in gas lift valveand tail plugto the ambient outside the gas lift valve. Again, reasons for these leaks can vary, including the failure of operators to properly torque tail pluginto gas lift valve, inconsistencies in the manufactured thicknesses of crush washer, the placement of O-ringtoo close to an open surface of gas lift valve(where it can literally extrude from the gas lift valve due to extreme pressures), etc. Whatever the reason, the present inventor has discovered a new and improved tail plug and assembly for gas lift valves that better prevents the heretofore described leaks and other problems associated with such valves.

Various features and advantageous details are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the description herein. Descriptions of well-known starting materials, processing techniques, components, and equipment are omitted so as not to unnecessarily obscure the invention. It should be understood, however, that the detailed description and the specific examples, while indicating embodiments of the invention, are given by way of illustration only, and not by way of limitation. Various substitutions, modifications, additions, and/or rearrangements within the spirit and/or scope of the underlying inventive concept will become apparent to those skilled in the art from this disclosure.

The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those skilled in the relevant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those skilled in the art, is intended or implied. To the extent that a term or phrase is intended to have a special meaning, i.e., a meaning other than that understood by skilled artisans, such special definition will be expressly set forth in the specification in a definitional manner that directly and unequivocally provides the special definition for the term or phrase.

The present exemplary embodiments describe an improved tail plug and assembly for a gas lift valve. Those skilled in the art will appreciate that other embodiments are contemplated. For example,illustrates a cross-section of an exemplary embodiment of gas lift valveincluding an embodiment of the present invention. As shown, valvemay include (among other components/portions) gas chamberand tail plug. (Those skilled in the art will appreciate other standard components of a gas lift valve not shown here.)

In this embodiment, of which there are others within the scope of the present invention, gas lift valveincludes a bore at its top/upper end for receiving tail plug. This bore in gas lift valvemay be a bore in gas lift valveitself or another component of the gas lift valve, such as a removable dome cap. As those skilled in the art will appreciate, a dome cap can be a removable portion of the gas lift valve, which can be threaded into a bore in the top of the gas lift valve and itself having a bore for receiving a tail plug and perhaps even the gas injection valve core. An example of a dome cap is described in co-pending patent application Ser. No. 18/925,487, which is incorporated herein by reference. Thus, the bore for receiving the tail plug can be in the gas lift valve itself or the gas lift valve's dome cap. In other words, a bore in the dome cap is also considered a bore in the gas lift valve itself. While not shown in, those skilled in the art will appreciate that a gas injection valve core is mounted in the bore of the gas lift valve shown in(or perhaps in the bore of the dome cap as described) above gas chamberas discussed above in connection with. As with the prior art gas lift valves, gas lift valvecan be “charged” to a predetermined pressure level by injecting a gas into gas chambervia the gas injection valve core.

As shown in more detail in(which is an enlarged version of detail B in), tail plug(which may be made of brass in one embodiment or another material in other embodiments) is inserted into the upper bore of gas lift valve(using an NPT thread in one embodiment or a straight thread in other embodiments). As shown (see also), the threads on tail plugthat hold it in the gas lift valve are located on the upper portion of the tail plug, as opposed to the lower portion of the prior art tail plug shown in. Likewise, the mating threads in gas lift valveare located on the upper portion of the valve's bore, as opposed to below the upper portion of the bore in the prior art valve as shown in. As those skilled in the art appreciate, a straight thread has a uniform diameter along its length, meaning it remains the same size from one end to the other, typically used for non-tapered applications. In contrast, an NPT (National Pipe Tapered) thread features a tapered design, which means the diameter gradually decreases along the length of the thread. This tapering allows for a tighter seal when connecting pipes, making NPT threads ideal for plumbing and fluid transfer applications, where preventing leaks is essential.

Applicant has discovered (among other things disclosed here and as will be appreciated by those skilled in the art by reading the present application) that an embodiment using an NPT thread to connect a brass tail plug to a stainless-steel bore in the gas lift valve (or dome cap as the case may be) creates a better barrier against leaks of the type described above in the prior art. Aside from the enhanced leak-proof barrier provided by the NPT thread itself, this enhanced barrier appears to be particularly efficient at eliminating leaks in embodiments where the brass tail plug includes male threads and the stainless-steel bore/dome cap includes female threads since the softer brass tail plug's male threads crush and deform into the bore/dome cap's harder stainless-steel female threads. Applicant has discovered that the leak-proof nature of this design is not as susceptible to operators not properly torquing the tail plug into the bore/dome cap as was the case in the prior art. Note, however, that the present invention is not limited to using a brass tail plug, a stainless-steel bore/dome cap, and/or straight or NPT threads.

In still other/alternate embodiments, the leak path may be further enhanced against leaks by including crush washerand/or O-ring sealin the path as shown in the exemplary embodiment of. In that regard, as shown in, an embodiment of tail plugmay have crush washer groove, which can be a portion of tail plughaving a reduced diameter relative to other diameters of the tail plug, thereby forming a shoulder on the tail plug that mates with a corresponding shoulder in the bore of gas lift valve. Likewise, as shown in, tail plugcan have an O-ring seal groove, which can be a portion of tail plughaving a reduced diameter relative to other diameters of the tail plug, thereby forming a groove to hold O-ring seal.

Notably, in one embodiment, the order of crush washerand O-ring sealas arranged on tail plugis reversed with respect to that of the prior art (compareto), which applicant also has discovered enhances the leak-proof nature of the tail plug. In other words, in the embodiment of(as opposed to the prior art embodiments shown in) the crush washer is placed closer to the top/upper end of the tail plug than the O-ring. This further precludes the prior art problem (described above) of the O-ring extruding through the interface between the tail plug and the gas lift valve in extreme pressure conditions.

are perspective views of tail plug(from), whereasis a side view thereof,is a top view thereof, andis a bottom view thereof. Collectively,illustrate an exemplary embodiment of tail plug. For example,show O-ring seal groovefor housing O-ring, crush washer groovefor housing crush washer, and the male portion of threadsthat interface with the corresponding female threads in the bore of the gas lift valve (or dome cap as the case may be), as best shown in. For embodiments not including crush washerand/or O-ring seal,could be modified to not include regions for housing one or both of those components.shows that this particular embodiment of tail plugincludes a hexagonal head suitable for interfacing with a standard wrench to insert and remove the tail plug from the gas lift valve.

Finally,is a perspective view of crush ringshown inand;is a front view thereof; andis a side view thereof. In an embodiment, this crush ring can be made from copper.

Although the invention(s) is/are described herein with reference to specific embodiments, various modifications and changes can be made without departing from the scope of the present invention(s), as set forth in the claims below. Accordingly, the specification and Figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present invention(s). Any benefits, advantages, or solutions to problems that are described herein with regard to specific embodiments are not intended to be construed as a critical, required, or essential feature or element of any or all the claims.

Unless stated otherwise, terms such as “first” and “second” are used to arbitrarily distinguish between the elements such terms describe. Thus, these terms are not necessarily intended to indicate temporal or other prioritization of such elements. The terms “coupled” or “operably coupled” are defined as connected, although not necessarily directly, and not necessarily mechanically. The terms “a” and “an” are defined as one or more unless stated otherwise. The terms “comprise” (and any form of comprise, such as “comprises” and “comprising”), “have” (and any form of have, such as “has” and “having”), “include” (and any form of include, such as “includes” and “including”) and “contain” (and any form of contain, such as “contains” and “containing”) are open-ended linking verbs. As a result, a system, device, or apparatus that “comprises,” “has,” “includes” or “contains” one or more elements possesses those one or more elements but is not limited to possessing only those one or more elements. Similarly, a method or process that “comprises,” “has,” “includes” or “contains” one or more operations possesses those one or more operations but is not limited to possessing only those one or more operations.

Accordingly, the protection sought herein is as set forth in the claims below.