CLAIM OF PRIORITY UNDER 35 U.S.C. § 119
BACKGROUND
Field
[0002] 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.
Description of the Related Art
[0003] 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.
[0004] 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.
[0005] 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.
[0006] 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
[0007] 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.
[0008] 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.
[0009] 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.
[0010] 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.
[0011] 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, the spring may alternatively occupy a space
in a variable volume valve chamber between the first and second stem components, without
being coupled to one or both stem component/s.
[0012] 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.
[0013] 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.
[0014] 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.
[0015] A valve for performing gas lift operations may be provided that incorporates two
edge-welded bellows and a ball-orifice closing mechanism. The gas lift valve may incorporate
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 may be divided into
two components. One of the stem components may be 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
may allow 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.
[0016] The invention includes one or more corresponding aspects, embodiments or features
in isolation or in various combinations whether or not specifically stated (including
claimed) in that combination or in isolation. For example, it will readily be appreciated
that features recited as optional with respect to the first aspect may be additionally
applicable with respect to the other aspects without the need to explicitly and unnecessarily
list those various combinations and permutations here (e.g. the valve of one aspect
may comprise features of any other aspect). Optional features as recited in respect
of a method may be additionally applicable to an apparatus; and vice versa. For example,
a valve may be configured to perform a step of a related method.
[0017] In addition, corresponding means for performing one or more of the discussed functions
are also within the present disclosure.
[0018] It will be appreciated that one or more embodiments/aspects may be useful in connecting
and/or disconnecting electricity, such as bus-bars.
[0019] The above summary is intended to be merely exemplary and non-limiting.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] 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.
[0021] FIG. 1 is a section view of a gas injection wellbore.
[0022] FIG. 2 is a section view of a side pocket mandrel incorporating a gas lift valve
in accordance with aspects of the present disclosure.
[0023] 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.
[0024] FIG. 4 is a flow diagram of example operations for performing downhole gas lift,
in accordance with aspects of the present disclosure.
DETAILED DESCRIPTION
[0025] 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.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] 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.
[0036] 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.
[0037] 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).
[0038] 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.
[0039] 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.
[0040] 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.
[0041] Once within the valve, the injection gas may be channeled first into a multicompartment
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.
[0042] 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.
[0043] 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).
[0044] 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.
[0045] 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.
[0046] 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.
[0047] 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.
[0048] 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.
[0049] 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.
[0050] 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.
[0051] 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.
[0052] 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.
[0053] 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.
[0054] 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.
[0055] 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.
[0056] 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.
[0057] 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.
[0058] 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.
[0059] 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.
[0060] 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.
[0061] 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.
[0062] 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.
[0063] 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.
[0064] 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.
[0065] 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.
[0066] 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.
[0067] 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.
[0068] 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.
[0069] 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.
[0070] 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.
[0071] 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.
[0072] 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
hupper-o in FIG. 3B to the smaller height
hupper-uc of the upper bellows in FIG. 3A.
[0073] 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
hlower-o in FIG. 3B to the greater height of the lower bellows
hlower-uc in FIG. 3A.
[0074] 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.
[0075] 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.
[0076] 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.
[0077] 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
hupper-ic in FIG. 3C to the larger height
hupper-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
hlower-ic in FIG. 3C to the smaller height of the lower bellows
hlower-o in FIG. 3B.
[0078] 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.
[0079] 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.
[0080] 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.
[0081] 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.
[0082] 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.
[0083] 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.
[0084] 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.
[0085] 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.
[0086] 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
hupper-ic in FIG. 3C to the smaller height
hupper-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
hlower-ic in FIG. 3C to the greater height of the lower bellows
hlower-uc in FIG. 3A.
[0087] 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.
[0088] 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.
[0089] 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.
[0090] 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.
[0091] It will be appreciated that any of the aforementioned apparatus may have other functions
in addition to the mentioned functions, and that these functions may be performed
by the same apparatus.
[0092] The applicant hereby discloses in isolation each individual feature described herein
and any combination of two or more such features, to the extent that such features
or combinations are capable of being carried out based on the present specification
as a whole in the light of the common general knowledge of a person skilled in the
art, irrespective of whether such features or combinations of features solve any problems
disclosed herein, and without limitation to the scope of the claims. The applicant
indicates that aspects of the present invention may consist of any such individual
feature or combination of features. It should be understood that the embodiments described
herein are merely exemplary and that various modifications may be made thereto without
departing from the scope of the invention.
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 or 2, 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 or 4, wherein the first and second stem components are mechanically
coupled by a spring.
6. The valve of any of claims 3 to 5, 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 any of claims 3 to 7, 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.
9. The valve of any preceding claim, wherein the valve is configured to operate in external
pressures of at least 10 000 psi.
10. 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.
11. The method of claim 10, 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.
12. The method of claim 10 or 11, 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.
13. The method of claim 12, 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.
14. The method of any of claims 10 to 13, wherein injecting the gas downhole compresses
the first bellows.
15. The method of any of claims 10 to 14, wherein the sealing element comprises a ball
disposed at a tip of the stem.