GAS LIFT VALVE

Abstract

A gas lift valve is provided with increased longevity and reliability for preventing backflow. A wide cylindrical sliding member stabilizes axial movement of a valve element in the gas lift valve. A wide spring around the sliding member biases the valve element toward closure during back flow. The spring is physically supported and guided by the sliding member and protected from gas flow injection by the same sliding member. A one-piece poppet version of the valve element provides a consistent closing seal, and the sliding member protects the valve seat and poppet from full force of an injected gas. A dart version of the valve element includes a hexagonal race for movement of the sliding member, which prevents rotational wear of components and provides a straight flow path for the injection gas with no sharp transitions to wear and no sharp angles to erode.

Description

BACKGROUND

Gas lift is a process in which a gas is injected from the annulus of a well into the production tubing of the well, to lower the density of oil being recovered, making the fluid easier to lift. “Annulus” as applied to a well casing refers to the space, lumen, or void around the outside of a central pipe within a larger pipe, tubing, or casing that immediately surrounds the central pipe. An annulus is the space between pipes when one pipe is inserted into another pipe. The injected gas aerates to lighten the well fluid for flow to the surface. Gas lift valves control the flow of gas during either an intermittent or continuous-flow gas lift operation. A principle of gas lift operation is differential pressure control with a variable orifice size to further constrain the maximum flow rate of gas. By incorporating a hydrostatic pressure chamber that can be charged with different pressures, injection pressure-operated gas lift valves and unloading valves can be configured so that an upper valve in the production string opens before a lower valve opens, even though both valves receive the injection gas from the same annulus. A gas lift valve is either fully open or fully closed, there is no intermediate valve state. Gas lift valves are often retrievable using a kick-off tool in the well. Back check is a critical component for gas lift valves to prevent the well fluid from recirculating back to the annulus of the casing.

SUMMARY

An example gas lift valve includes a first port for receiving a gas from a well annulus, a second port for transferring the gas to a well production tube, a valve seat, a poppet valve element for allowing a one-way flow of the gas past the valve seat and for preventing a back flow of the gas, a sliding barrel attached to the poppet valve element to maintain a sealing surface of the poppet valve element in alignment with a sealing surface of the valve seat, and a spring coiled around the outside diameter of the sliding barrel to bias the poppet valve element in a closed position against the valve seat. A one-piece poppet version of the valve element provides a consistent closing seal. A dart version of the valve element includes a hexagonal race to prevent rotational wear of components and a straight flow path for the injection gas with no sharp transitions and angles to wear and erode. An example method includes constructing a gas lift valve with a wide cylindrical sliding member to reliably seat a valve element and biasing the valve element toward a closed state with a wide spring around the wide cylindrical sliding member. This summary section is not intended to give a full description of the example gas lift valves. A detailed description with example embodiments follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an example gas lift operation using improved gas lift valves.

FIG. 2 is a diagram of an example gas lift valve assembly.

FIG. 3 is a diagram of a first embodiment of an example gas lift valve.

FIG. 4 is a diagram of a second embodiment of an example gas lift valve.

FIG. 5 is a diagram showing a cross-sectional view of the example gas lift valve of FIG. 4.

FIG. 6 is a flow diagram of an example method of constructing a gas lift valve.

DETAILED DESCRIPTION

This disclosure describes gas lift valves with improved features. For context, FIG. 1 depicts a gas lift system 100 that includes a production tubing 140 that extends into a wellbore. For purposes of gas injection, the system 100 includes a gas compressor 120 that is located at the surface of the well to pressurize gas to be communicated to an annulus 150 of the well. To control the communication of gas between the annulus 150 and a central passageway 170 of the production tubing 140, the system 100 may include several side pocket gas lift mandrels 160 (example gas lift mandrels 160a, 160b and 160c). Each of the gas lift mandrels 160 includes an associated gas lift valve 180 (such as example gas lift valves 180a, 180b and 180c) for establishing one-way fluid communication from the annulus 150 to the central passageway 170. Near the surface of the well, one or more of the gas lift valves 180 may be unloading valves. An unloading gas lift valve opens when the annulus pressure exceeds the production tubing pressure by a certain threshold, a feature that aids in pressurizing the annulus below the valve before the valve opens. Other gas lift valves 180 are located farther below the surface of the well and may not have an opening pressure threshold.

Each gas lift valve 180 may contain a check valve element that opens to allow fluid flow (gas) from the annulus 150 into the production tubing 140 and closes when the fluid would otherwise back flow in the opposite direction. For example, the production tubing 140 may be pressurized for purposes of setting a packer, actuating a tool, performing a pressure test, and so forth. Thus, when the pressure in the production tubing 140 exceeds the annulus pressure, the valve element is closed to ideally form a seal to prevent flow from the tubing 140 to the annulus 150. However, it is possible that this seal may leak, and if leakage does occur, well operations that rely on production tubing pressure may not be able to be completed or performed. The leakage may require an intervention, which is costly, especially for a subsea well.

FIG. 2 shows a gas lift valve assembly 200 in accordance with some embodiments of the example gas lift valves. In general, the gas lift valve assembly 200 includes an example gas lift valve 180 that includes a valve element (described further below) to control fluid communication between the annulus 150 of the well and the central passageway 170 of the production tubing 140. The example gas lift valve 180 resides inside a longitudinal passageway 204 of a mandrel 206. In addition to the longitudinal passageway 204, the mandrel 206 includes a separate longitudinal passageway 208 that has a larger cross-section than passageway 204, is eccentric to passageway 204, and forms part of the production tubing string (140). As depicted in FIG. 2, the longitudinal passageways 204 and 208 are generally parallel to each other. The mandrel 206 includes at least one radial port 210 to establish communication between the longitudinal passageways 204 and 208 and also includes at least one radial port 212 to establish fluid communication between the longitudinal passageway 204 and the annulus 150 of the well that surrounds the mandrel 206.

In general, the gas lift valve 180 is configured to control fluid communication between the longitudinal passageway 208 and the annulus 150 of the well. In this regard, the gas lift valve 180 includes an upper seal 214 and a lower 216 seal (for example, o-ring seals, v-ring seals, or a combination) that circumscribe the outer surface housing of the example gas lift valve 180 to form a sealed region that contains radial ports 218 of the example gas lift valve 180 and the radial ports 212 of the mandrel 206. One or more lower ports 220 (located near a lower end 222 of the longitudinal passageway 204) of the gas lift valve 180 are located below the lower seal 216 and are in fluid communication with the radial ports 210 near the lower end 222. The longitudinal passageway 204 is sealed off (not shown) to complete a pocket to receive the example gas lift valve 180. In this arrangement, the example gas lift valve 180 is positioned to control fluid communication between the radial ports 210 (i.e., the central passageway of the production tubing string 140) and radial ports 212 (of the mandrel 206, in fluid communication with the annulus 150). During operation, the example gas lift valve 180 establishes a one-way communication path from the annulus 150 to the central passageway 170 of the production tubing 140. Thus, when enabled, the gas lift valve 180 permits gas flow from the annulus 150 to the production tubing 140 and ideally prevents flow in the opposite direction.

The gas lift valve 180 may be installed or removed by a wireline operation in the well. Thus, in accordance with some embodiments, the example gas lift valve assembly 200 may include a latch 224 (located near an upper end 226 of the mandrel 206) that may be engaged with a wireline tool (not shown) for installing the example gas lift valve 180 in the mandrel 206 or removing the example gas lift valve 180 from the mandrel 206.

The example gas lift valve assembly 200 may be used in a subterranean well or in a subsea well, depending on a particular embodiment.

In an implementation, the example gas lift valve 180 has a general design that is depicted in FIG. 3. Radial ports 218 of the example gas lift valve 180 may be formed in a tubular housing 302 of the example gas lift valve 180. The tubular housing 302 may be connected to an upper concentric housing section 304 of the gas lift valve 180 that extends to the latch 224 (not shown in FIG. 3).

The housing 302 includes an interior space 305 for receiving gas that flows in from the radial ports 218. Injection gas that enters the radial ports 218 flows into the interior space 305 and through an orifice 306, which may be connected to the lower end of the housing 70. The orifice 306 may by cylindrical, square-edged, or streamlined for venture effects, for example. The housing around the orifice 306 may be partially circumscribed by the lower end of the housing 302 and may be sealed to the housing 302 with one or more seals 308, such as o-rings, for example. The housing of the orifice 306 may extend inside an upper end of a lower housing 310 that is concentric with the housing 302 and extends further downhole. The housings 310 and 302 may be sealed together via one or more seals 312, such as o-rings. As also depicted in FIG. 3, the lower seal 216 (formed from one or more v-type seals, o-rings, etc.) may circumscribe the outer surface of the housing 310 in some embodiments. The orifice 306 is in communication with a lower passageway 314 that extends through the housing 310.

Poppet Back Check Valve Embodiment

In an implementation, the lower end of the housing 310 forms a valve seat 316, a seat that is opened and closed (for purposes of controlling the one-way flow through the gas lift valve 180) via a valve element 322 of a check valve assembly 318. The check valve assembly 318 may be spring-loaded using, for example, spring 320 in a guided spring assembly. The check valve assembly 318 may be anchored or secured via a socket-type connection to a movable, sliding, hollow cylindrical member, such as a piston or barrel 324 surrounded by the inside diameter of coils of the spring 320. The check valve assembly 318 moves as a unit depending on the injected gas pressure, allowing pressurized gas to flow through the valve end of the barrel 324 in a controlled manner.

In an implementation, a poppet-shaped version of the valve element 322 (“poppet valve element” 322) allows gas flow, or closes off gas flow as the case may be, controlling fluid communication through the valve seat 316. The check valve assembly 318 exerts an “upward” bias force (towards the surface, i.e., toward closure of the example gas lift valve 180 against back pressure) on the valve element 322 for biasing the valve element 322 to close off fluid communication through the valve seat 316.

The particular mushroom-like geometry of a poppet-shaped disk, when used as the valve element 322, provides a concerted valve closure all the way around the sealing perimeter of the poppet valve element 322 when the poppet valve element 322 shuts during pressure scenarios that would cause backflow. In an implementation, a one-piece poppet valve element 322 ensures alignment of the seal surface when it closes.

Besides this consistent evenness of the closing seal due to the poppet geometry, the poppet valve element 322 also provides reliability in the seal that is created between the poppet valve element 322 and the valve seat 316. The poppet-shaped valve element 322, as guided by the piston or barrel 324 that supports the spring 320, moves smoothly and reliably in one axial direction for opening and closing. The relatively large bore of the barrel 412 located just inside the coils of the spring 406 provides strength and smoothness to the axial movement of the dart valve element 404, and removes unnecessary play, as compared with conventional back check valves that use a spindly support member for movement of a conventional valve element.

In an implementation, the cross-sectional diameter of the barrel 324 may be substantially the same diameter as that of the poppet valve element 322 to maintain a sealing surface of the poppet valve element 322 in good or perfect parallel-planar alignment with a sealing surface of the valve seat 316. Thus, the geometry of the check valve assembly 318 affords the poppet valve element 322 reliable and smooth movement, so that the poppet valve element 322 makes a consistent leak-proof seal. Thus, the poppet valve element 322 snaps shut against the valve seat 316 in consistent alignment making a quick and reliable seal when the pressure in the production tubing 140 becomes greater than the pressure in the annulus 150.

When, however, the annulus pressure is sufficient (relative to the production tubing pressure) to exert a force on the poppet valve element 322 to overcome the bias of the spring 320, then the poppet valve element 322 retracts (opens downward) to permit gas fluid to flow from the annulus 150 into the production tubing 140 to effect gas lift.

The lower end of the lower housing 310 may be sealed via an o-ring 328 for example, to a nose housing or end housing 326 that extends further downward toward the lower port(s) 220 of the example gas lift valve 180. An interior space 330 inside the end housing 326 is in communication with the production tubing side (140 and 170) of the example gas lift valve 180 and receives the injected gas via the annulus 150 that opens the check valve assembly 318 and flows through the valve seat 316.

An example gas lift valve 180 that includes the poppet valve element 322 provides several other advantages. A wide spring 320 can be used and the inside diameter (ID) of the spring 320 can be disposed around and guided by the piston or barrel 324, as shown. This arrangement provides steady and reliable movement of the poppet valve element 322 as compared with conventional spring-loaded valve elements that either rely on an unsupported spring or rely on a narrow spring that imparts too much play in the side-to-side movement of a conventional valve element. In FIG. 3, the spring 320 is also protected from the flow stream, adding to longevity and reliable function of the spring 320. The design and geometry of the example gas lift valve 180 also avoids direct high speed flow past the sealing surface, which can provide a valve closure for preventing backflow that is more sensitive to smaller backflow pressures. In an implementation, the movement of the open poppet valve element 322 is stopped by the poppet valve element 322 itself contacting the nose housing or end housing 326 of the example gas lift valve 180, as compared with conventional techniques of having movement limited by other components attached to a valve element, which could cause the valve element to stick at an open position.

Ideally, fluid cannot flow from the production tubing side of the check valve assembly 318 to the annulus side, because of the poppet valve element 322 closing and making a seal against the valve seat 316.

Hex Dart Back Check Valve Embodiment

FIG. 4 shows an example hex dart gas lift valve 402, which includes an example valve race 502 (FIG. 5) that has a hexagonal cross-section, and includes a dart style back check valve element 404 (“dart valve element” 404). This example embodiment of a gas lift valve 402 provides several advantages, including a gas flow path that is relatively free from sharp angular transitions, to reduce wear and increase longevity. The hexagonal geometry of the hex dart gas lift valve 402 counteracts erosion at sharp corners, especially when some impurities or abrasives also flow through the valve components with the injected gas. The hex dart gas lift valve 402 uses a spring 406 that is fully guided on its inside diameter (ID) for stability. The hex-shaped race 502 (FIG. 5) of the hex dart gas lift valve 402 can also prevent rotation of the dart valve element 404 and connected components (and thus prevent valve sticking) caused by high velocity gas flow.

In FIG. 4, a lower housing 408 of the example gas lift valve 402 provides the structure for a valve seat 410. The valve seat 410 opens or closes for controlling one-way flow through the example gas lift valve 402 via the dart valve element 404. A piston, hollow cylindrical member, or barrel 412 may be spring-loaded using, for example, spring 406 around the outside diameter of the barrel 412 in a guided spring assembly. The dart valve element 404 may be anchored or secured via a socket-type connection 414 to the piston or barrel 412 that is surrounded by the inside diameter of the spring 406.

The dart valve element 404, connector 414, and barrel 412 move as a unit to open against the expansive bias of the spring 406, which is set to keep the valve closed, opening when injected gas pressure overcomes the force of the spring 406. Orifice openings near the connector 414 may allow control of the amount of pressurized gas that can flow through the valve seat 410 at a given time, thereby adding control and sensitivity to the valve.

The dart valve element 404 is guided in its movement by the barrel 412 that stabilizes and guides the spring 406. The relatively large bore of the barrel 412 located just inside the coils of the spring 406 provides strength and smoothness to the axial movement of the dart valve element 404, and removes unnecessary play, as compared with conventional back check valves that use a spindly support member for movement of a conventional valve element. In an implementation, the diameter of the barrel 412 may be substantially the same diameter as that of the dart valve element 404. The relatively wide spring 406 and the geometry of the hex race 502 and wide barrel 412 member affords the dart valve element 404 reliable and smooth movement, so that the dart valve element 404 makes a consistent leak-proof seal. The dart valve element 404 shuts against the valve seat 410 in consistent alignment making a reliable seal when the pressure in the production tubing 140 becomes greater than the pressure in the annulus 150, resulting in a potential back flow condition.

When the annulus pressure is sufficient (relative to the production tubing pressure) to exert a force on the dart valve element 404 to overcome the bias of the spring 406, then the dart valve element 404 is pushed back (opens downward) to permit gas fluid to flow from the annulus 150 into the production tubing 140 to effect gas lift.

The lower end of the lower housing 408 may be sealed via an o-ring 416 for example, to a nose housing or end housing 418 that extends further downward toward the lower port(s) 420 of the example hex dart gas lift valve 402. An interior space 422 inside the end housing 418 is in communication with the production tubing side (140 and 170) of the example hex dart gas lift valve 402 and receives the injected gas via the annulus 150 that opens the dart valve element 404 and flows through the valve seat 410.

FIG. 5 shows an example cross-section of a hexagonal race 502 of the hex dart gas lift valve 402, as viewed from the plane in FIG. 4 designated (in 2D) by line C-C. Depending on implementation, part of the barrel 412 may be hexagonal and ride in the hexagonal race 502, or in some implementations the entire barrel 412 may have a hexagonal outside sliding surface, or in still other implementations, the entire valve element assembly, including the dart valve element 404 may have hexagonal outer presentations. The hexagonal race 502 prevents rotation of the dart valve element 404 and associated components, and thus prevents extra surface wear and potential valve sticking that can be caused by high velocity gas flow.

EXAMPLE METHOD

FIG. 6 is a flow diagram of an example method 600 of constructing a gas lift valve. In the flow diagram the individual operations are shown as blocks.

At block 602, a gas lift valve is constructed to include a wide cylindrical sliding member to reliably seat a valve element. The wide cylindrical sliding member, or barrel, is attached to the valve element. Because the barrel moves within a large bore, the barrel has very stable movement in an axial direction with very little play in other movement directions. This assures a strong and correctly aligned seal mating between the valve element and the valve seat.

At block 604, the valve element is biased toward a closed state with a wide spring around the wide cylindrical sliding member. The wide spring is both supported by the wide cylindrical sliding member and protected from the gas being injected by the wide cylindrical sliding member.

The wide cylindrical sliding member and the spring may have a cross-sectional diameter substantially the same as a largest diameter of the valve element in order to maintain a sealing interface of the valve element and a valve seat in a parallel-planar alignment with each other with very little deviation to a side. The wide cylindrical sliding member can also protect the valve element and a valve seat from full force of a gas injection flow.

A poppet valve element connected to the wide cylindrical sliding member reliably closes the gas lift valve during a back flow condition. Alternatively, a dart valve element in the gas lift valve prevents a back flow condition and when used with a hexagonal race or bore for the wide cylindrical sliding member, rotational wear of the valve components caused by a high velocity gas flow can be prevented. The hexagonal race also provides a flow path for the injected gas that is free from sharp angular transitions counteracts erosion at sharp corners.

Conclusion

Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from the subject matter. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. §112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function.

Claims

1. A gas lift valve, comprising: a first port for receiving a gas from a well annulus;a second port for transferring the gas to a well production tube;a valve seat;a poppet valve element for allowing a one-way flow of the gas past the valve seat and for preventing a back flow of the gas;a sliding barrel attached to the poppet valve element to maintain a sealing surface of the poppet valve element in alignment with a sealing surface of the valve seat; anda spring coiled around the outside diameter of the sliding barrel to bias the poppet valve element in a closed position against the valve seat.

2. The gas lift valve of claim 1, wherein the sliding barrel and the spring have a wide cross-sectional diameter substantially the same as a diameter of the poppet valve element to maintain a sealing interface of the poppet valve element and the valve seat in parallel-planar alignment with each other.

3. The gas lift valve of claim 1, wherein the poppet valve element comprises a one-piece member for alignment of a sealing surface of the poppet valve element with a sealing surface of the valve seat.

4. The gas lift valve of claim 1, wherein the spring is protected from a main flow of the gas by the barrel.

5. The gas lift valve of claim 1, wherein a sealing interface between the poppet valve element and the valve seat is protected from a direct high speed flow of the gas by at least one valve component.

6. The gas lift valve of claim 1, wherein a maximum open state of the poppet valve element is determined by the poppet valve element contacting an end housing of the gas lift valve.

7. A gas lift valve, comprising: a first port for receiving a gas from a well annulus;a second port for transferring the gas to a well production tube;a valve seat;a dart valve element for allowing a one-way flow of the gas past the valve seat and for preventing a back flow of the gas;a sliding barrel attached to the dart valve element to maintain a sealing surface of the dart valve element in alignment with a sealing surface of the valve seat;a spring coiled around the outside perimeter of the sliding barrel to bias the poppet valve element in a closed position against the valve seat; anda race of hexagonal cross-section for a movement of the sliding barrel.

8. The gas lift valve of claim 7, further comprising a flow path for gas substantially free from sharp angular transitions.

9. The gas lift valve of claim 7, wherein a hex dart configuration counteracts erosion at sharp corners.

10. The gas lift valve of claim 7, wherein the spring is fully-guided on an inside diameter (ID) of the spring for stability.

11. The gas lift valve of claim 7, wherein a hex dart configuration prevents a rotation of a valve component caused by high velocity gas flow.

12. The gas lift valve of claim 7, wherein the sliding barrel and the spring have a wide cross-sectional diameter substantially the same as a diameter of the dart valve element to maintain a sealing interface of the dart valve element and the valve seat in parallel-planar alignment with each other.

13. The gas lift valve of claim 7, wherein the spring is protected from a main flow of the gas by the barrel.

14. The gas lift valve of claim 7, wherein a sealing interface between the dart valve element and the valve seat is protected from a direct high speed flow of the gas by at least one valve component.

15. A method, comprising: constructing a gas lift valve with a wide cylindrical sliding member to reliably seat a valve element; andbiasing the valve element toward a closed state with a wide spring around the wide cylindrical sliding member.

16. The method of claim 15, wherein the wide cylindrical sliding member and the spring have a cross-sectional diameter substantially the same as a largest diameter of the valve element to maintain a sealing interface of the valve element and a valve seat in a parallel-planar alignment with each other; and wherein the wide cylindrical sliding member protects the valve element and a valve seat from a full force of a gas injection flow.

17. The method of claim 15, wherein the spring is protected from a main flow of an injection gas by the wise cylindrical sliding member.

18. The method of claim 15, further comprising attaching a one-piece poppet-shaped valve element to the wide cylindrical sliding member to reliably close the gas lift valve during a back flow condition.

19. The method of claim 15, further comprising: incorporating a dart valve element in the gas lift valve to prevent a back flow condition; andincorporating a hexagonal race for the wide cylindrical sliding member in the gas lift valve to prevent a rotation of the valve components caused by a high velocity gas flow.

20. The method of claim 19, wherein the hexagonal race provides a flow path for a gas substantially free from sharp angular transitions; and wherein the hexagonal race counteracts erosion at sharp corners.