GAS LIFT VALVE WITH BALL-ORIFICE CLOSING MECHANISM AND FULLY COMPRESSIBLE DUAL EDGE-WELDED BELLOWS

Abstract

A valve for performing gas lift operations is provided that incorporates two edge-welded bellows and a ball-orifice closing mechanism. The gas lift valve incorporates features enabling enhanced compression of one of the bellows, beyond an initial closure point of the valve. For example, a stem with the sealing ball is divided into two components, wherein one of the stem components is configured to continue moving in relation to the other stem component with the ball, which is fixed in position when the ball seals the orifice and initially closes the valve. This continued movement allows one of the bellows to be fully compressed in the ultimately closed valve position, thereby protecting the bellows from high pressures and potential failure that could occur to bellows in a partially compressed state.

Description

CLAIM OF PRIORITY UNDER 35 U.S.C. §119

This application claims benefit of U.S. Provisional Patent Application No. 61/650,632, filed May 23, 2012 and entitled “Dual Edge-Welded Gas Lift Valve with Deep Compression Bellows Assembly,” which is herein incorporated by reference in its entirety.

BACKGROUND

1. Field

Aspects of the present disclosure generally relate to high pressure valves and, more particularly, to valves for use in hydrocarbon wells configured for gas lift operations.

2. Description of the Related Art

To obtain hydrocarbon fluids from an earth formation, a wellbore is drilled into the earth to intersect an area of interest within a formation. The wellbore may then be “completed” by inserting casing within the wellbore and setting the casing therein using cement. In the alternative, the wellbore may remain uncased (an “open hole” wellbore), or may be only partially cased. Regardless of the form of the wellbore, production tubing is typically run into the wellbore primarily to convey production fluid (e.g., hydrocarbon fluid, as well as water) from the area of interest within the wellbore to the surface of the wellbore.

Often, pressure within the wellbore is insufficient to cause the production fluid to rise naturally through the production tubing to the surface of the wellbore. Thus, to force the production fluid from a reservoir to the surface of the wellbore, artificial lift means are sometimes employed. Gas lift and steam injection are examples of artificial lift means for increasing production of oil and gas from a wellbore.

Gas lift systems are often the preferred artificial lifting systems because operation of gas lift systems involves fewer moving parts than operation of other types of artificial lift systems, such as sucker rod lift systems. Moreover, because no sucker rod is required to operate the gas lift system, gas lift systems are usable in offshore wells having subsurface safety valves that would interfere with a sucker rod.

Gas lift systems commonly incorporate valves in side pocket mandrels to enable the lifting of production fluid to the surface. Ideally, the gas lift valves allow gas from the tubing annulus to enter the production tubing through the valve, but prevent reverse flow of production fluid from the tubing to the annulus.

SUMMARY

Certain aspects of the present disclosure provide a gas lift valve incorporating two edge-welded bellows assemblies. The gas lift valve incorporates features enabling enhanced compression of one of the bellows, beyond an initial closure point of the valve.

Certain aspects of the present disclosure provide a valve for downhole gas lift operations. The valve generally includes a housing having an inlet and an outlet for fluid flow; a seat disposed in the housing for controlling the fluid flow from the inlet to the outlet; a stem configured to move in the housing, wherein a sealing element associated with the stem is configured to mate with an orifice in the seat to prevent the fluid flow from the inlet to the outlet, thereby closing the valve; first bellows coupled to the housing and to the stem; and second bellows coupled to the housing and to a movable piston of a variable volume dome in the housing, wherein the second bellows are fully compressed when the valve is closed.

Certain aspects of the present disclosure provide a method for performing downhole gas lift operations. The method generally includes providing a valve and opening the valve. The valve generally includes a housing having an inlet and an outlet for fluid flow; a seat disposed in the housing for controlling the fluid flow from the inlet to the outlet; a stem configured to move in the housing, wherein a sealing element associated with the stem is configured to mate with an orifice in the seat to prevent the fluid flow from the inlet to the outlet, thereby closing the valve; first bellows coupled to the housing and to the stem; and second bellows coupled to the housing and to a movable piston of a variable volume dome in the housing, wherein the second bellows are fully compressed when the valve is closed. Opening the valve generally involves injecting gas downhole, wherein an injected gas pressure is greater than a dome gas pressure in the variable volume dome, such that the stem moves away from the seat to allow the fluid flow between the inlet and the outlet via the orifice.

Certain aspects of the present disclosure provide a system for downhole gas lift operations. The system generally includes casing disposed in a wellbore; production tubing disposed in the casing; and at least one valve. The at least one valve generally includes a housing having an inlet and an outlet for fluid flow, wherein the fluid flow enters the inlet from an annulus between the casing and the production tubing and exits the outlet into the production tubing; a seat disposed in the housing for controlling the fluid flow from the inlet to the outlet; a stem configured to move in the housing, wherein a sealing element associated with the stem is configured to mate with an orifice in the seat to prevent the fluid flow from the inlet to the outlet, thereby closing the valve; first bellows coupled to the housing and to the stem; and second bellows coupled to the housing and to a movable piston of a variable volume dome in the housing, wherein the second bellows are fully compressed when the valve is closed.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the various aspects, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.

FIG. 1 is a section view of a gas injection wellbore.

FIG. 2 is a section view of a side pocket mandrel incorporating a gas lift valve in accordance with aspects of the present disclosure.

FIGS. 3A, 3B, and 3C are vertical cross-sectional illustrations of an example gas lift valve in different operating states, in accordance with aspects of the present disclosure.

FIG. 4 is a flow diagram of example operations for performing downhole gas lift, in accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

A typical gas lift completion 10 illustrated in FIG. 1 may include a wellhead 12 atop a casing 14 that passes through a formation. Production tubing 20 positioned in the casing 14 may have a number of side pocket mandrels 30 and a production packer 22. To conduct a gas lift operation, operators conventionally install gas lift valves 40 in the side pocket mandrels 30.

With the valves 40 installed, compressed gas G from the wellhead 12 may be injected into the annulus 16 between the production tubing 20 and the casing 14. In the side pocket mandrels 30, the gas lift valves 40 then act as one-way valves by opening in the presence of high-pressure injection gas, thereby allowing the gas to flow from the annulus 16 to the tubing 20. When pressure is reduced as a result of discontinued pumping of gas at the surface, the valve closes to prevent reverse production fluid flow from the tubing 20 to the annulus 16.

Downhole, the production packer 22 forces upwards travel through the production tubing 20 of produced fluid P entering casing perforations 15 from the formation. Additionally, the packer 22 keeps the gas flow in the annulus 16 from entering the tubing 20.

The injected gas G passes down the annulus 16 until it reaches the side pocket mandrels 30. Entering the mandrel's inlet ports 35, the gas G first passes through the gas lift valve 40 before it can pass into the production tubing 20. Once in the tubing 20, the gas G can then rise to the surface, lifting production fluid in the production tubing in the process.

Aspects of the present disclosure provide design features for a gas lift valve that may help to prevent material damage of valve bellows exposed to high pressure.

Certain gas lift valve designs incorporate a ball sealing element that, in a closed position, covers and seals an orifice in a seat and conduit (designed to channel gas flow from the annulus 16 and valve interior to the production tubing 20 when the valve is open). The ball sealing element may be coupled to a stem or other similarly configured valve component configured to variably move based on the net upwards or downwards expansion force of pressurized gas in opposing valve chambers or compartments. The ball sealing element may be composed of tungsten carbide (WC) or any other suitable material that is very hard and wear-resistant.

In the absence of injection gas, these movable components travel in a closing direction due to dominance of a biasing pressure. In the presence of injection gas (at a sufficient pressure to overcome the biasing force), these movable components shift in an opening direction.

Commonly, these gas lift valves employ bellows assemblies which are compressed and expanded with the downwards and upwards movement of valve components. However, in many cases, the valve configuration results in the bellows being subjected to high pressures. At the same time, the valve configuration may result in the bellows not being fully volumetrically compressed due to physical limitations imposed by closure of the valve.

When bellows are subjected to high pressure, their material durability may be significantly reduced if the bellows are prevented from being fully compressed. As used herein, the term “fully compressed” generally refers to the individual washers of the bellows being flattened to form a stack of washers that effectively forms a solid tube of metal. In a partially compressed state (where the individual washers are not flattened) the bellows may be subject to collapse in the presence of very high pressures, possibly leading to failure of the valve.

Prolonged operation of bellows under high pressure in an intermediately compressed state may result in material degradation or failure of the bellows and a corresponding loss of valve functionality. Aspects of the present disclosure, however, may take advantage of the feature that bellows may exhibit impressive durability when maintained in a fully compressed state under high pressure.

Aspects of the present disclosure provide a bellows arrangement that allows the bellows to be maintained in a fully compressed state when the gas lift valve is closed.

As will be described in greater detail below, the gas lift valve may involve a ball sealing element, upper and lower stem components, upper and lower bellows, and a spring element configured so to avoid physical restrictions that might otherwise impede full compression of the upper bellows upon valve closure. The upper bellows may be maintained in a state of heightened compression for so long as the valve continues to be closed, thereby making the upper bellows less vulnerable to material failure.

FIG. 2 is a diagram showing an example disposition of a gas lift valve 300 of the present disclosure in a side pocket mandrel 30. As depicted, an entrance port 302 (an inlet) of the gas lift valve may be placed adjacent a mandrel port 35 such that pressurized injection gas may enter the valve from the annulus 16, and flow through the valve into the production tubing. Packing seals 202, 204 may be used between the valve 300 and the walls of the side pocket mandrel 30 on either side of the entrance port 302 and the mandrel port 35. Also depicted in FIG. 2 are upper bellows 310 (shown in an expanded state), lower bellows 304 (shown in a compressed state), an upper stem component 308, a lower stem component 318, an exit conduit 324, and an exit port 325 (an outlet).

FIGS. 3A, 3B, and 3C illustrate the gas lift valve 40 in different operating states. FIG. 3A shows the valve when in an ultimately closed state, with a top bellows fully compressed. FIG. 3B shows the valve in an open state. FIG. 3C shows the valve in an initially closed state, with the valve sealed, but the upper bellows only partially compressed.

For clarity and explanatory purposes only, and in accordance with the depiction in FIGS. 3A, 3B, and 3C, all further discussion of gas lift valves in the present disclosure will assume that the gas lift valve is mounted vertically, that opening the valve entails primarily upwards movements of movable valve components, and that closing the valve entails primarily downwards movement of these valve components. However, this convention is not meant to restrict the scope of this disclosure, and the embodiments described herein admit of any orientation, dimensions, and direction of valve operations, from slightly off-vertical to fully horizontal.

The gas lift valve 300 may be configured to allow only one-way flow of pressurized injection gas from the annulus 16, through the valve and into the production tubing 20. The valve may be configured such that injection gas flowing in the one-way direction may freely enter the gas lift valve from the annulus 16 through the entrance port 302.

Once within the valve, the injection gas may be channeled first into a multi-compartment variable volume valve chamber 326. If the gas pressure is sufficiently high so that the valve is opened, as shown in FIG. 3B, the gas may then flow freely through the orifice 322 and into the exit conduit 324.

The orifice 322 may form the valve end of the exit conduit 324, and the seating element 323 (or seat) having the orifice may be composed of tungsten carbide or any other suitable material (e.g., a very hard and wear-resistant material). The injection gas may then be channeled out of the valve and into the production tubing 20 through the exit conduit and the exit port 325 in the nose of the valve.

The gas lift valve 300 may be configured to enable pressurized flow in the one-way direction (as shown in FIG. 3B) and to restrict backflow through the operation of a ball sealing element 320 which may be rigidly disposed at the lowest point (e.g., the tip) of the lower stem component 318 (when in the initially closed state as shown in FIG. 3C or in the ultimately closed state as shown in FIG. 3A).

The sliding stem may be divided into an upper stem component 308 and a lower stem component 318 for reasons which are described in detail below. For some embodiments, the lower stem component may be linked to the upper stem component via a spring element 316. For other embodiments, the spring element 316 may alternatively occupy space in the variable volume valve chamber 326 between the upper and lower stem components, without being coupled to either stem component.

For some embodiments, the valve may be configured with a variably engaged slot-pin mechanism 358 comprising a slot 356 in the lower stem component 318 and a pin 354 or other protuberance associated with the upper stem component 308 and disposed in the slot. The mechanism 358 may comprise more than one slot-pin combination, such as another slot-pin combination opposite the slot 356 depicted in FIGS. 3A-3C or two more slot-pin combinations spaced 120° apart. The upper and lower stem components 308, 318 may variably interact through the spring element 316 and the slot-pin mechanism 358 when it is engaged. The slot-pin mechanism may further serve to prevent rotational or horizontal displacement of the upper stem component 308 relative to the lower stem component 318, and vice versa.

As shown in FIG. 3A, the gas lift valve 300 may close to restrict backflow through downwards displacement of the upper stem component 308, the lower stem component 318, and the ball sealing element 320. This downwards displacement of the ball sealing element 320 may result in the ball sealing element abutting the sealing element 323 and partially entering the orifice 322 from above, thereby sealing the orifice and closing the valve. The contact between the ball sealing element 320 and the seating element 323 may also immediately impede further downwards movement of the lower stem component 318, thereby imposing a “mechanical stop” on the lower stem component. Thereafter, and with the valve 300 remaining sealed, the upper stem component 308 may, for a time, continue to be displaced downwards against the spring element 316 to facilitate increased compression of the upper bellows 310.

The gas lift valve 300 may include a sealed, variable volume dome 314 containing a pressurized gas (e.g., charged nitrogen gas) to provide a biasing force to close the valve in the absence of injection gas. The variable volume dome 314 may be configured such that the pressurized gas constantly imparts a biasing force on the upper stem component 308 which urges the upper stem component in a downwards, sealing direction. As will be explained in greater detail below, the gas lift valve 300 may be configured such that the upper stem component 308 may distribute the biasing force to the lower stem component 318 through the engaged slot-pin mechanism 358, through the spring element 316, or a combination of the slot-pin mechanism and spring element.

For some embodiments, with the valve open and the magnitude of counteracting gas pressure forces in the valve sufficiently small, the urging of the biasing force may be sufficient to cause valve closure. Valve closure may occur in two distinct, but consecutive stages of movement. The first stage may primarily involve the upper and lower stem components 308, 318 being pushed downwards by the biasing force towards an initially closed position in which the ball sealing element 320 contacts the seating element 323 and seals the orifice 322, as shown in FIG. 3C. The second stage may involve the lower stem component 318 and the ball sealing element 320 being held fast to remain in position, with the ball sealing element 320 being pushed down against the seating element 323 and the sealed orifice 322. Simultaneously, and while the slot-pin mechanism 358 may be at least initially disengaged, the upper stem component 308 is forced downwards, and the spring element 316 is compressed until the upper bellows 310 are fully compressed and the downwards movement is physically stopped, illustrated by the ultimately closed valve configuration depicted in FIG. 3A.

As described above, during gas lift operations when the annulus 16 is pressurized with injection gas, the injection gas may enter the valve from the annulus and pressurize variable volume valve chamber 326. The valve may be configured such that pressurized injection gas in the variable volume valve chamber 326 opposes the biasing force by imparting an upwards force directly upon the upper stem component 308.

An additional upwards force may, at times, be contributed by gas present in the exit conduit 324 which may be a product of the gaseous environment in the production tubing 20. Gas in the exit conduit may create a tubing pressure which may be directly imparted on the lower stem component 318 primarily when the valve is closed. Some of this upwards force may be transmitted to the upper stem component 308 through the spring element 316. For brevity, the combination of any tubing pressure and injection gas pressure affecting the upper stem component at a moment of time will be referred to herein as “injection gas pressure” or “injection gas pressure in the variable volume valve chamber,” even though this may be a simplification of actual conditions.

When the injection gas pressure in the variable volume valve chamber 326 is sufficiently high, this pressure may counteract and dominate the biasing force from the pressurized variable volume dome 314. The upper stem component 308 may be initially raised in isolation by the injection gas pressure for a short distance, and the spring element 316 may expand upwards. This isolated upwards displacement may occur until the pin 354 engages the upper end of the slot 356. Alternatively, the valve may be configured such that the upper stem component 308 may rise in isolation until the spring element 316 is extended.

Thereafter, an engaged slot-pin mechanism 358 or extended spring element 316 may result in the lower stem component 318 being pulled upwards with the upper stem component 308 by the force of the injection pressure, thereby opening the valve for one-way flow of injection gas into the production tubing 20. This open position is depicted in FIG. 3B.

As will be understood by descriptions below of example valve operations, the open position of FIG. 3B may be the state when injection gas pressure in the valve is sustained above a pressure threshold such that it dominates over the biasing pressure. The pressure threshold may be the pressure above which the injection gas pressure forces overcome the opposing biasing force and first begin to raise the upper stem component 308. The pressure threshold may be a function of the pressure of the gas in the variable volume dome 314 and other physical characteristics of the valve components.

The ultimately closed position of FIG. 3A may be the equilibrium, steady-state configuration of the valve in the absence of injection gas (or when injection gas pressure in the valve is below the pressure threshold) such that the biasing forces dominate and force the valve closed.

The initially closed position of FIG. 3C may, thus, not be a steady-state of the valve, despite the orifice 322 being sealed and the exit conduit 324 being blocked in this configuration. Rather, this condition may be only a transitory state of the valve as certain valve components transition from the open position to the ultimately closed position with the upper bellows 310 fully compressed.

Upwards and downwards movements of the upper stem component 308 may be influenced by, and may occur in conjunction with, expansion and compression of the upper bellows 310 and the lower bellows 304. The bellows assemblies may be formed of bellows elements (e.g., a stack of washers or other metal discs) residing within a column of damping fluid. The bellows elements may be edge-welded together (e.g., the metal discs may be welded at both the inner diameter and the outer diameter, or the inner diameter of one bellows element may be welded to an inner surface of the next bellows element). The bellows assemblies may act as a compressible and resilient gas seal interface between the gas in the variable volume dome 314 and any gas present in the valve, such as injection gas in the variable volume valve chamber 326.

One end of the upper bellows 310 may be coupled (e.g., welded) to a widened horizontal flange portion 312 of the upper stem component, which may act as a piston for the variable volume dome 314. For other embodiments, the flange portion 312 may be a component separate from, but coupled to the upper stem component 308 The other end of the upper bellows 310 may be coupled to a rigid bellows adapter 360. In this manner, when the biasing pressure is the dominant force, compression of the upper bellows may occur in conjunction with the downwards travel of the upper stem component 308. When injection gas pressure in the variable volume valve chamber 326 is dominant, the upper bellows may expand upwards in conjunction with the travel of the upper stem component 308.

The lower bellows 304 may be coupled (e.g., welded) to a lower portion of the upper stem component 308. One end of the lower bellows 304 may be coupled to a lower horizontal protrusion 350 of the upper stem component. The other end of the lower bellows may be coupled (e.g., welded) to the rigid bellows adapter 360. In this manner, when the upper stem component 308 is raised, the lower bellows 304 may be contracted upwards. When the upper stem component 308 is pushed downwards, the lower bellows 304 may be expanded downwards.

The upper and lower bellows 310, 304 may also serve to dampen the displacement of the upper and lower stem components 308, 318. With the upper and lower stem components travelling upwards during valve opening, the lower bellows may serve as a mechanical stop which imposes an upper limit on the travel of the upper stem component, which may also curtail lower stem component travel.

The upper and lower bellows 310, 304 may be linked through a fluid passage 370 routed through the upper stem component 308 (i.e., a portion of the upper stem component is hollow and forms a chamber, which may be filled with a fluid). The fluid passage may serve to transport damping fluid from one bellows assembly to the other, thereby preventing chatter in the bellows. The fluid passage 370 may be configured such that when either the upper or lower bellows are compressed, damping fluid flows from the compressing bellows to the other bellows, which is expanding. Composed of a non-compressible fluid (e.g., silicone oil), the damping fluid protects the upper and lower bellows 310, 304 from damage when the bellows are exposed to external gas pressures. The transfer rate of the damping fluid between the upper and lower bellows can be controlled by flow area adjustments in the fluid passage 370.

The lower stem component 318 may interact with the upper stem component 308 through the spring element 316. The spring element 316 may be formed of a strong vertically-mounted spring disposed within the variable volume valve chamber 326. The spring element 316 may also be formed of any compressible medium or linkage exhibiting compressibility and resilience properties similar to those of a strong spring. The spring element 316 may enable the lower stem component 318 to be pulled upwards or pushed downwards by forces imparted on the upper stem component 308 and distributed, though the spring element, to the lower stem component 318. The spring element 316 may also serve to provide a buffering feature by preventing forces imparted on the lower stem component 318 from being fully distributed to the upper stem component 308 (when the slot-pin mechanism 358 is not engaged). In this manner, the spring element 316 may enable the upper stem component 308 to move downwards and towards the lower stem component 318 following initial valve closure, when downwards movement of the lower stem component and the ball sealing element 320 is fully resisted by the seating element 323.

The upper and lower stem components 308, 318 may at times be mutually influenced by temporary contact enabled by engagement of the slot-pin mechanism 358. Lower engagement of the slot-pin mechanism may enable the biasing force to be distributed from the upper stem component 308 to the lower stem component 318, at times resulting in the lower stem component being pushed downwards with the upper stem component. Upper engagement of the slot-pin mechanism 358 may result in the lower stem component 318 being pulled upwards by a rising upper stem component 308 (e.g., due to an injection gas pressure in the chamber 326). In this manner, when the dominant force raises or lowers the upper stem component 308, the upper and lower stem components may move in tandem.

The slot-pin mechanism 358 may also be configured so as to be disengaged at initial valve closure. Through this disengagement, the slot-pin mechanism may further serve to prevent the physical stop force imparted on the lower stem component 318 from being distributed to the upper stem component 308. This situation may facilitate further downwards movement of the upper stem component 308 towards the stationary lower stem component 318, which in turn may enable continued compression of the upper bellows 310.

The slot-pin mechanism 358 may include at least one pin 354, which may be a rigid extension of the upper stem component 308. The lower portion of the upper stem component 308 may extend into a cavity, shaft or other opening (not shown) in the top of the lower stem component 318. Each of the pins 354 may extend into a vertically oriented slot 356 within the lower stem component 318. With the pin 354 not in contact with the upper or lower edge of the slot 356, the upper stem component 308 may move vertically without engaging the slot-pin mechanism 358, and without transmitting force through the pin to the lower stem component 318.

However, upwards movement of the upper stem component 308 may eventually result in the pin 354 contacting the upper slot edge, causing the slot-pin mechanism 358 to engage. Continued upwards displacement of the upper stem component 308 past this point of upper engagement may result in the lower stem component 318 being pulled along by the upper stem component 308. From an unengaged position, downwards displacement of the upper stem component 308 may result in the pin 354 contacting the lower slot edge, causing the slot-pin mechanism 358 to engage. Continued downwards displacement by the biasing force of the upper stem component 308 past this point of lower engagement may result in the lower stem component 318 being pushed along with the upper stem component 308.

An upper portion of the lower stem component 318 may be configured to fit within a cavity in the bottom portion of the upper stem component 308. In this configuration, when the pin 354 is not engaged, upwards and downwards movement of the upper stem component 308 relative to the lower stem component 318 may alter the portion of the lower stem component 318 which is surrounded by the upper stem component.

The variable volume valve chamber 326 may be configured to include the space between the lower stem component 318 and the rigid valve housing 328, as well as a cylindrical volume of space containing the spring element 316. The horizontal protrusion 350 of the upper stem component 308 may encapsulate the variable volume valve chamber 326 from above. In this way, the horizontal protrusion 350 may enable the force of injection gas in the variable volume valve chamber 326 to be directly imparted upon the upper stem component 308, and to raise the upper stem component when that force is dominant. Thus, the encapsulation of the variable volume valve chamber 326 by the horizontal protrusion may enable the valve chamber to expand in conjunction with upwards displacement of the upper stem component 308 at times when the injection gas pressure is dominant. When the biasing pressure is dominant, the variable volume valve chamber 326 may contract in conjunction with downwards displacement of the upper stem component 308.

The variable volume dome 314 may also be configured to expand and contract based on the dominant gas pressure force in the valve. Furthermore, the variable volume dome 314 may be hermetically sealed, thereby enabling the mass of pressurized gas in the variable volume dome to be maintained at a constant or near-constant level. A horizontal flange portion 312 (of the upper stem component 308) may provide a variable, encapsulating lower surface of—and may act as a piston for—the variable volume dome. The flange portion 312 may be urged to move up or down with the upper stem component 308, depending on the dominant gas pressure force in the valve 300. Downwards displacement of the upper stem component 308 expands the variable volume dome 314, while upwards displacement contracts the dome.

So that operations of gas lift valve 300 may be understood in greater detail, the following paragraphs will describe an example sequence of valve operations. Because it is common for gas lift valves to be in the ultimately closed position before gas lift operations begin, this configuration will be described first.

With the valve in the ultimately closed position of FIG. 3A, high pressure gas may be injected into the annulus 16 when gas lift operations commence. Upon reaching the subsurface depth at which the gas lift valve 300 is disposed, the pressurized injection gas may enter the valve through the entrance port 302 and flow into the variable volume valve chamber 326, thereby increasing the valve chamber pressure.

If pressure in the variable volume valve chamber 326 increases sufficiently to overcome the biasing force exerted by the variable volume dome 314, the upwards pressure exerted on the horizontal protrusion 350 may initially lift the upper stem component 308 in isolation, while the lower stem component 318 may remain in position against the seating element (as a result of compression of the sprint element 316 and/or the contemporary disengagement of the slot-pin mechanism 358). The isolated lifting of the upper stem component may cause the spring element 316 to expand and may raise the pin 354 in the slot 356 until the pin reaches the upper edge of the slot. Thereafter, further raising of the upper stem component 308 may pull the lower stem component upwards by way of the engaged slot-pin mechanism 358 and/or the spring element, thereby lifting the ball sealing element 320 out of the orifice 322 and opening the valve for the passage of injected gas, as illustrated in FIG. 3B. Thereafter, and for as long as the valve remains open, pressurized gas may continuously flow freely from the annulus 16, through the entrance port 302, into the variable volume valve chamber 326, through the exit conduit 324, out of the exit port 325, and into the production tubing 20.

The upwards movement of the upper stem component 308 may also result in expansion of the variable volume valve chamber 326 and the upper bellows 310, as well as contraction of the variable volume dome 314 and compression of the lower bellows 304. Accordingly, the upper bellows may be extended in the open valve configuration. This expansion of the upper bellows 310 may be understood by comparison of the larger height of the upper bellows h_upper-o in FIG. 3B to the smaller height h_upper-uc of the upper bellows in FIG. 3A.

After a certain amount of upwards travel of the upper stem component 308 and lower stem component 318, the lower bellows 304 may be fully compressed and may then retard the upwards travel of the upper stem component 308. The compression of the lower bellows 304 may be understood by comparison of the smaller height of the lower bellows k_lower-o in FIG. 3B to the greater height of the lower bellows h_lower-uc in FIG. 3A.

The resulting open position of the valve is depicted in FIG. 3B. FIG. 3B depicts that the orifice 322 (and hence, the exit conduit 324) may be unobstructed by the ball sealing element 320, which may be temporarily disposed above and clear of the orifice. The upper bellows 310 may be in an expanded state, and the variable volume dome 314 may be in a contracted state resulting from the previous upwards travel of the upper stem component 308 and associated horizontal flange portion 312. As shown, the spring element 316 may be in an uncompressed state, and the pin 354 may be in a position at or near the top edge of the slot 356. The valve 300 may remain in this open position for as long as the injection pressure in the variable volume valve chamber 326 is sufficient to resist the biasing force of the pressurized gas in the variable volume dome 314.

When the pumping of injection gas into the annulus 16 ceases, the injection pressure in the variable volume valve chamber 326 may diminish. If injection pressure drops below the pressure threshold, the biasing pressure may once again become dominant and may initially drive the upper stem component 308 and the lower stem component 318 downwards, with the lower stem component 318 being pushed by the upper stem component 308 via the spring element 316. The downwards movement of the upper stem component 308 may be accompanied by compression of the upper bellows 310, expansion of the lower bellows 304, expansion of the variable volume dome 314, and contraction of the variable volume valve chamber 326.

This tandem downwards movement may persist until the preliminary closed position is reached when the ball sealing element 320 contacts the seating element 323 and closes off the orifice 322, sealing the valve. The disposition of the gas lift valve components at initial closure is depicted in FIG. 3C.

As depicted in FIG. 3C, when the valve reaches the initially closed position, the lower stem component 318 may again be physically prevented from moving downwards by rigid contact between the ball sealing element 320 and the seating element 323. As a result of the previous downwards displacement of the upper stem component 308, the upper bellows 310 and the lower bellows 304 may be partially compressed and partially expanded, respectively. The partial compression of the upper bellows 310 at the point of initial valve closure may be understood by comparing the smaller height of the upper bellows h_upper-ic in FIG. 3C to the larger height h_upper-o of the upper bellows in FIG. 3B. The partial expansion of the lower bellows 304 may be understood by comparing the greater height of the lower bellows h_lower-ic in FIG. 3C to the smaller height of the lower bellows k_lower-o in FIG. 3B.

When the valve components reach the initially closed position, the pin 354 may be positioned between the upper and lower edges of the slot 356, resulting in disengagement of the slot-pin mechanism 358. The spring element 316 may therefore be (further) compressed in response to the resistance of the physical stop imparted on the lower stem component 318 and the continued downwards biasing force imparted on the upper stem component 308. In this way, the spring element 316 may enable continued downwards movement of the upper stem component 308 by buffering the upper stem component from the force of the physical stop being imparted on the lower stem component.

Consequently, the biasing force may continue to push the upper stem component 308 downwards towards the stagnated lower stem component 318. The downwards movement of the upper stem component 308 towards the lower stem component 318 may also cause the pin 354 to move downwards in the slot 356.

This additional downwards movement of the upper stem component 308 may further compress the upper bellows 310 and further expand the lower bellows 304. The downwards movement may continue for so long as the biasing force is sufficient to overcome the upwards forces resulting from the increasing resistance of the compressed spring element 316 or until the upper bellows 310 are fully compressed to solid.

By allowing the upper stem component 308 to continue moving independently of the jammed lower stem component 318, the valve is prevented from stagnating in a steady-state, closed configuration which leaves the upper bellows 310 partially compressed and thus vulnerable to material degradation. Without the spring element 316 and/or another compressible joining mechanism capable of preventing the mechanical stop force from being fully imparted onto the upper stem component 308, the mechanical stop would result in this stagnated steady-state, closed configuration.

Valves that exhibit this stagnation may place unnecessary material strain on the upper bellows because the mechanical stop prevents complete bellows compression while the biasing force is still being exerted on the upper bellows. Thus, the upper bellows would endure this compression force despite being in a partially compressed state. In such a state, the bellows may be expected to exhibit poorer material durability and be subject to more rapid material failure, as compared to the structural solidity exhibited when the bellows are fully compressed.

Returning now to FIG. 3C, continued downwards movement of the upper stem component 308 and compression of the upper bellows 310 beyond the initially closed state of FIG. 3C may eventually be restricted when the upper bellows 310 reach a fully compressed (or near fully compressed) state. The resulting valve configuration may be the ultimately closed configuration depicted in FIG. 3A and described above. The ultimately closed configuration of the valve may be characterized in that the spring element 316 may be at least partially compressed. Furthermore, due to the continued physical stop imparted on the ball sealing element 320 and the lower stem component 318, the position of the lower stem component may be unchanged from its position at the time of initial closure.

FIG. 3A further illustrates that, relative to the initially closed configuration of FIG. 3C, the upper stem component 308 may be at a lower position in the valve. As described previously, this component may be driven to this lower position during the valve's transition to the ultimately closed configuration by the continued downwards force of the biasing pressure. The lower position of the upper stem component 308 relative to its position at initial closure may be a consequence of previous buffering provided by downwards compression of the spring element 316 against the physically stopped lower stem component 318.

Furthermore, the upper bellows 310 are shown in a state of compression that is greater than the upper bellows compression depicted in FIG. 3C. This enhanced compression may also be a consequence of the biasing force, buffering of the spring element, and the resultant continued downwards movement of the upper stem component subsequent to the initially closed configuration. Thus, as depicted in FIG. 3A, the compression of the upper bellows 310 may be a result of the compression of the spring element 316 subsequent to the initially closed configuration. Accordingly, the spring element 316 is depicted in a state of increased compression relative to the depiction of the spring element in FIG. 3C. Additionally, the lower bellows 304 may be in an extended state.

This enhanced compression of the upper bellows 310 in the ultimately closed valve configuration may be understood by comparison of the larger height of the upper bellows h_upper-ic in FIG. 3C to the smaller height h_upper-uc of the upper bellows in FIG. 3A. The extension of the lower bellows 304 in the ultimately closed valve configuration may be understood by comparison of the smaller height of the lower bellows h_lower-ic in FIG. 3C to the greater height of the lower bellows h_loweruc in FIG. 3A.

FIG. 4 is a flow diagram of example operations 400 for performing downhole gas lift, in accordance with aspects of the present disclosure. The operations 400 may begin, at 402, by providing a valve. The valve generally includes a housing having an inlet and an outlet for fluid flow; a seat disposed in the housing for controlling the fluid flow from the inlet to the outlet; a stem configured to move in the housing, wherein a sealing element associated with the stem is configured to mate with an orifice in the seat to prevent the fluid flow from the inlet to the outlet, thereby closing the valve; first bellows coupled to the housing and to the stem; and second bellows coupled to the housing and to a movable piston of a variable volume dome in the housing, wherein the second bellows are fully compressed when the valve is closed.

At 404, the valve may be opened by injecting gas downhole. An injected gas pressure may be greater than a dome gas pressure in the variable volume dome, such that the stem moves away from the seat to allow the fluid flow between the inlet and the outlet via the orifice. For certain aspects, injecting the gas downhole compresses the first bellows.

At 406, the operations may further include closing the valve by discontinuing to inject the gas downhole. The dome gas pressure may be greater than an external gas pressure external to the housing, such that the stem moves and the sealing element mates with the orifice in the seat.

According to certain aspects, the stem includes a first stem component and a second stem component mechanically coupled to the first stem component. The first and second stem components may be configured to move in relation to one another. For certain aspects, the first stem component is mechanically stopped by the seat when closing the valve, and the second stem component continues to travel until the second bellows are fully compressed (providing a second mechanical stop). For certain aspects, the first stem component has a slot, and the second stem component has a pin configured to travel within the slot as the first or the second stem component moves in relation to the other stem component. The first and second stem components may be mechanically coupled by a spring. For certain aspects,

According to certain aspects, the first stem component is mechanically stopped by the seat when the sealing element mates with the orifice. The second stem component may be configured to continue moving in relation to the first stem component until the second bellows are fully compressed.

According to certain aspects, a portion of the second stem component is hollow and is filled with a non-compressible fluid for protecting at least one of the first or second bellows from damage when the bellows are exposed to gas pressures. For certain aspects, the non-compressible fluid is silicone oil. For certain aspects, the non-compressible fluid is configured to prevent chatter in at least one of the first or second bellows as the non-compressible fluid is transferred between the first and second bellows via the hollow portion of the second stem component.

According to certain aspects, the sealing element is a ball disposed at a tip of the stem. The ball may be composed of tungsten carbide (WC), for example, or any other suitable material (e.g., a very hard and wear-resistant material). For certain aspects, at least one of the first and second bellows are edge-welded bellows. For certain aspects, the first bellows are fully compressed when the valve is open. When the bellows are fully compressed, the bellows cannot be damaged by external pressures (up to very high values), since the bellows cannot travel any further to compression after being fully compressed. Thus, the valve may be configured to operate in external pressures of up to 10,000 psi or higher.

While the foregoing is directed to embodiments of the present disclosure, other and further embodiments may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

1. A valve for downhole gas lift operations, comprising:

a housing having an inlet and an outlet for fluid flow;

a seat disposed in the housing for controlling the fluid flow from the inlet to the outlet;

a stem configured to move in the housing, wherein a sealing element associated with the stem is configured to mate with an orifice in the seat to prevent the fluid flow from the inlet to the outlet, thereby closing the valve;

first bellows coupled to the housing and to the stem; and

second bellows coupled to the housing and to a movable piston of a variable volume dome in the housing, wherein the second bellows are fully compressed when the valve is closed.

2. The valve of claim 1, wherein the sealing element comprises a ball disposed at a tip of the stem.

3. The valve of claim 1, wherein the stem comprises a first stem component and a second stem component mechanically coupled to the first stem component, and wherein the first and second stem components are configured to move in relation to one another.

4. The valve of claim 3, wherein the first stem component has a slot and wherein the second stem component has a pin configured to travel within the slot as the first or the second stem component moves in relation to the other stem component.

5. The valve of claim 3, wherein the first and second stem components are mechanically coupled by a spring.

6. The valve of claim 3, wherein a portion of the second stem component is hollow and is filled with a non-compressible fluid for protecting at least one of the first or second bellows from gas pressures.

7. The valve of claim 6, wherein the non-compressible fluid comprises silicone oil.

8. The valve of claim 6, wherein the non-compressible fluid is configured to prevent chatter in at least one of the first or second bellows as the non-compressible fluid is transferred between the first and second bellows via the hollow portion of the second stem component.

9. The valve of claim 3, wherein the first stem component is mechanically stopped by the seat when the sealing element mates with the orifice and wherein the second stem component is configured to continue moving in relation to the first stem component until the second bellows are fully compressed.

10. The valve of claim 1, wherein at least one of the first or second bellows are edge-welded bellows.

11. The valve of claim 1, wherein the valve is configured to operate in external pressures of at least 10,000 psi.

12. The valve of claim 1, wherein the first bellows are fully compressed when the valve is open.

13. A method for performing downhole gas lift operations, comprising:

providing a valve, comprising: a housing having an inlet and an outlet for fluid flow; a seat disposed in the housing for controlling the fluid flow from the inlet to the outlet; a stem configured to move in the housing, wherein a sealing element associated with the stem is configured to mate with an orifice in the seat to prevent the fluid flow from the inlet to the outlet, thereby closing the valve; first bellows coupled to the housing and to the stem; and second bellows coupled to the housing and to a movable piston of a variable volume dome in the housing, wherein the second bellows are fully compressed when the valve is closed; and

opening the valve by injecting gas downhole, wherein an injected gas pressure is greater than a dome gas pressure in the variable volume dome, such that the stem moves away from the seat to allow the fluid flow between the inlet and the outlet via the orifice.

14. The method of claim 13, further comprising closing the valve by discontinuing to inject the gas downhole, wherein the dome gas pressure is greater than an external gas pressure external to the housing such that the stem moves and the sealing element mates with the orifice in the seat.

15. The method of claim 13, wherein the stem comprises a first stem component and a second stem component mechanically coupled to the first stem component, and wherein the first and second stem components are configured to move in relation to one another.

16. The method of claim 15, wherein the first stem component is mechanically stopped by the seat when closing the valve and wherein the second stem component continues to travel until the second bellows are fully compressed.

17. The method of claim 15, wherein injecting the gas downhole compresses the first bellows.

18. A system for downhole gas lift operations, comprising:

casing disposed in a wellbore;

production tubing disposed in the casing; and

at least one valve, comprising: a housing having an inlet and an outlet for fluid flow, wherein the fluid flow enters the inlet from an annulus between the casing and the production tubing and exits the outlet into the production tubing; a seat disposed in the housing for controlling the fluid flow from the inlet to the outlet; a stem configured to move in the housing, wherein a sealing element associated with the stem is configured to mate with an orifice in the seat to prevent the fluid flow from the inlet to the outlet, thereby closing the valve; first bellows coupled to the housing and to the stem; and second bellows coupled to the housing and to a movable piston of a variable volume dome in the housing, wherein the second bellows are fully compressed when the valve is closed.

19. The system of claim 18, wherein the stem comprises a first stem component and a second stem component mechanically coupled to the first stem component, and wherein the first and second stem components are configured to move in relation to one another.

20. The system of claim 19, wherein the first stem component has a slot, wherein the second stem component has a pin configured to travel within the slot as the first or the second stem component moves in relation to the other stem component, and wherein the first and second stem components are mechanically coupled by a spring

21. The system of claim 18, wherein the at least one valve is disposed in a side pocket mandrel of the production tubing.