Variable orifice gas lift valve assembly for high flow rates with detachable power source and method of using same

The present invention is a surface controlled gas lift valve designed for high flow rates and used in a subterranean well, comprising: a valve and actuating assembly for sealable insertion in a mandrel. The valve has a variable orifice which alternately permits, prohibits, or throttles fluid flow into the valve, and a detachable and/or remote actuator are disclosed. The valve may be actuated using momentary bursts of hydraulic pressure to the actuating assembly. Variable orifice opening settings are achieved by providing successive bursts of hydraulic pressure to the actuating assembly, which cause a cylindrical cam within the actuating assembly to be indexed between multiple support positions. The orifice valve and the actuator while operatively connected, may be separately installed in or retrieved from the mandrel by either wireline or coiled tubing intervention methods.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to subsurface well completion equipment and, 
more particularly, to an apparatus, or valve assembly, for lifting 
hydrocarbons from subterranean formations with gas at high production 
rates. Additionally, embodiments of independent and detachable actuators 
are disclosed. 
2. Description of the Related Art 
Artificial lift systems, long known by those skilled in the art of oil well 
production, are used to assist in the extraction of fluids from 
subterranean geological formations. The most ideal well for a company 
concerned with the production of oil, is one that flows naturally and 
without assistance. Often wells drilled in new fields have this advantage. 
In this ideal case, the pressure of the producing formation is greater 
than the hydrostatic pressure of the fluid in the wellbore, allowing the 
well to flow without artificial lift. However, as an oil bearing formation 
matures, and some significant percentage of the product is recovered, a 
reduction in the formation pressure occurs. With this reduction in 
formation pressure, the hydrocarbon issuance therefrom is likewise reduced 
to a point where the well no longer flows without assistance, despite the 
presence of significant volumes of valuable product still in place in the 
oil bearing stratum. In wells where this type of production decrease 
occurs, or if the formation pressure is low from the outset, artificial 
lift is commonly employed to enhance the recovery of oil from the 
formation. This disclosure is primarily concerned with one type of 
artificial lift called "Gas Lift." It should be noted, however, that a 
variety of fluid types can be used in accordance with the invention as 
will readily be perceived by one of ordinary skill in the art. 
Accordingly, the term "gas" as used herein should not be read as limiting 
the fluid to gases but, instead, should be read to include any of the 
variety of process fluids appropriate to artificial lift systems. 
Gas lift has long been known to those skilled in the art, as shown in U.S. 
Pat. No. 2,137,441 filed in November 1938. Other patents of some historic 
significance are U.S. Pat. Nos. 2,672,827, 2,679,827, 2,679,903, and 
2,824,525, all commonly assigned hereto. Other, more recent developments 
in this field include U.S. Pat. Nos. 4,239,082, 4,360,064 of common 
assignment, as well as U.S. Pat. Nos. 4,295,796, 4,625,941, and 5,176,164. 
While these patents all contributed to furthering the art of gas lift 
valves in wells, recent trends in drilling and completion techniques 
expose and highlight long felt limitations with this matured technology. 
The economic climate in the oil industry of the 1990's demands that oil 
producing companies produce more oil, which is now exponentially more 
difficult to exploit, that the oil be produced in less time, and without 
increasing prices to the consumer. One successful technique that is 
currently being employed is deviated and horizontal drilling, which more 
efficiently drains hydrocarbon bearing formations. This increase in 
production makes it necessary to use much larger production tubing sizes. 
For example, in years past, 23/8 inch production tubing was most common. 
Today, tubing sizes of offshore wells range from 41/2 to 7 inches. While 
much more oil can be produced from tubing this large, conventional gas 
lift techniques have reached or exceeded their operational limit as a 
result. 
In order for oil to be produced utilizing gas lift, a precise volume and 
velocity of the gas flowing upward through the tubing must be maintained. 
Gas injected into the hydrostatic column of fluid decreases the column's 
total density and pressure gradient, allowing the well to flow. As the 
tubing size increases, the volume of gas required to maintain the well in 
a flowing condition increases as the square of the increase in tubing 
diameter. If the volume of the gas lifting the oil is not maintained, the 
produced oil falls back down the tubing, and the well suffers a condition 
commonly known as "loading up." If the volume of gas is too great, the 
cost of compression and recovery of the lift gas becomes a significant 
percentage of the production cost. As a result, the size of a gas 
injection orifice in the gas lift valve is of crucial importance to the 
stable operation of the well. Prior art gas lift valves employ fixed 
diameter orifices in a range up to 3/4 inch, which may be inadequate for 
optimal production in large diameter tubing. This size limitation is 
geometrically limited by the gas lift valve's requisite small size, and 
the position of its operating mechanism, which prevents a full bore 
through the valve for maximum flow. 
Other prior art gas lift valves employ pressure responsive adjustable flow 
valves that automatically or manually adjust the gas flow rate through the 
gas lift valve to attempt to maintain a certain pressure condition within 
the well bore and the gas lift valve. Other gas lift valves may further 
employ hydraulic, electric, and electric-hydraulic actuators either 
integral to or separate or even detachable from the gas lift valve to 
remotely actuate the valve and to control the extent to which the valve is 
opened or closed. Co-pending U.S. application Ser. No. 08/912,150 
discloses several embodiments of separate or detachable actuators, or 
power units, responsive to hydraulic pressure to control the size of the 
opening of the variable orifice valve of gas lift valves and is 
incorporated by reference herein the same as if set forth fully herein 
except to the extent the teachings are consistent. 
A number of existing variable orifice adjustable gas lift valves require 
maintenance and balance of hydraulic pressure within the gas lift valve or 
valve actuator to maintain a particular flow setting of the gas lift valve 
orifice. Position holders have been utilized, which attempt to maintain 
the position of the actuator relative to the gas lift valve to attempt to 
mechanically assure that the setting of the gas lift valve orifice remains 
in the position set by the operator if conditions in the hydraulic system 
change slightly in use. However, such prior position holders were not 
designed to securely hold the gas lift valve orifice in a set position 
without the continued supply of hydraulic pressure. 
U.S. Pat. No. 5,535,767 discloses a remotely actuated adjustable choke 
valve having a rotatably adjustable cam and follower arrangement axially 
disposed within the valve body to selectively govern the relative axial 
position of the valve stem of the choke valve with respect to the valve 
body. However, the placement of the cam and follower within the valve body 
may be undesirable in certain applications, for example, where increased 
flow through the valve body is desired. Moreover, the hydraulic actuation 
system used to actuate the cam and follower to select the axial position 
of the valve stem within the valve body is also provided within the valve 
body, which can provide an undesirably complex valve system and also 
further decrease the flow rate available through the choke valve. 
Because well conditions and gas lift requirements change over time, those 
skilled in the art of well operations are also constantly aware of the 
compromise of well efficiency that must be balanced versus the cost of 
intervention to install the most optimal gas lift valves therein as well 
conditions change over time. Well intervention is expensive, most 
especially on prolific offshore or subsea wells, so a valve that can be 
utilized over the entire life of the well, and whose orifice size and 
subsequent flow rate can be adjusted to changing downhole conditions, is a 
long felt and unresolved need in the oil industry. There is also a need 
for a novel gas lift valve that has a gas injection orifice that is large 
enough to inject a volume of gas adequate to lift oil in large diameter 
production tubing. There is also a need for differing and novel operating 
mechanisms for gas lift valves that will not impede the flow of injection 
gas therethrough and that can be remotely set using a power source without 
the need for a continued supply of power to maintain the desired setting 
of the gas lift valve orifice. 
SUMMARY OF THE INVENTION 
The present invention has been contemplated to overcome the foregoing 
deficiencies and meet the above described needs. In one aspect, the 
present invention is a gas lift assembly for use in a subterranean well, 
comprising: a gas lift mandrel having first and second bores; a valve body 
with a longitudinal bore therethrough for sealable insertion in the first 
bore of the mandrel; a variable orifice valve in the valve body for 
controlling fluid flow through the body; and an actuating assembly 
provided separate from and connected to the variable orifice valve. 
Another feature of this aspect of the present invention is that the 
actuating assembly may further include a mechanical position holder and 
the mechanical position holder may comprise an indexable cam and follower 
arrangement. 
Another feature of this aspect of the present invention is that the 
indexable cam and follower arrangement may include a cylindrical cam 
having a plurality of axial slots formed around the periphery thereof, 
each of the axial slots having different lengths. Yet another feature of 
this aspect of the invention is that the different lengths of the axial 
slots may correspond to different variable orifice valve positions. 
Another feature of this aspect of the invention is that the actuating 
assembly may be hydraulically operated, and may further include: a 
hydraulic actuating piston located in the actuating assembly and 
operatively connected to the variable orifice valve; a spring, biasing the 
variable orifice valve in a full closed position; and at least one control 
line connected to the hydraulic actuating piston and extending to a 
hydraulic pressure source. 
Another feature of this aspect of the present invention is that either the 
valve body or the actuating assembly may be retrievably locatable within a 
side pocket mandrel by wireline and coiled tubing intervention tools. 
Further, either the gas lift valve or the actuating assembly may be 
selectively installed and retrievably detached from the actuating 
assembly. 
In another aspect, the present invention may be an actuating assembly for 
selectively setting the operating position of a variable orifice gas valve 
the gas valve having a valve stem and being positioned within a valve 
body, the actuating assembly comprising: an actuating assembly housing; an 
axially moveable piston disposed within the housing and operably connected 
to the orifice gas valve; an actuating device for selectively moving the 
moveable piston within the housing; and a mechanical position holder to 
retain the moveable piston in a desired operating position. A feature of 
this aspect of the invention is that the actuating device may comprise: a 
device for biasing the moveable piston to a first position; a hydraulic 
actuating chamber operably connected to the moveable piston; and a source 
of fluid pressure in fluid communication with the hydraulic actuating 
chamber for introduction of fluid pressure within the hydraulic actuating 
chamber to move the moveable piston to a second position, thereby moving 
the valve stem to a desired operating position within the valve body. 
Further, the mechanical position holder may be a rotatable cylindrical cam 
having: a plurality of axial slots disposed there around, each of the 
axial slots may have an intermediate slot connecting the axial slot to its 
neighboring axial slot; and the axial and intermediate slots may be 
adapted to receive a portion of an axially fixed follower engaged therein, 
whereby the follower will support the cylindrical cam and retain the 
moveable piston in a desired operating position. Another feature of this 
aspect of the present invention is that the cylindrical cam may be 
rotatably indexed so that the follower travels within the intermediate 
slot to be engaged within a neighboring axial slot. 
In another aspect, the present invention may be a gas lift valve assembly 
for use in a subterranean well, comprising: an elongated valve body having 
an injection gas port and a gas delivery port; an elongated valve stem 
disposed within said valve body for axial displacement relative thereto to 
adjust a rate of injection gas flow between the injection gas port and 
said gas delivery port as a function of a relative axial position of said 
valve stem with respect to said valve body; a cam disposed without said 
valve body and operably connected to the valve stem; said cam providing a 
plurality of axial displacement positions thereon to place said valve stem 
at a selected one of a plurality of relative axial positions with respect 
to said valve body; said cam operably connected to an actuating piston 
responsive to fluid pressure to reciprocate said actuating piston between 
cocked and set positions; said cam moving from a first axial displacement 
position to a second axial displacement position as said actuating piston 
is reciprocated, a difference between said first and second axial 
displacement positions thereby causing an adjustment of said rate of 
injection gas flow between said injection gas port and said gas delivery 
port. Another feature of this aspect of the present invention is that the 
cam and actuating piston may be disposed axially within an actuating 
housing separated from and detachably connected to the valve body.

While the invention will be described in connection with the preferred 
embodiments, it will be understood that it is not intended to limit the 
invention to those embodiments. On the contrary, it is intended to cover 
all alternatives, modifications, and equivalents as may be included within 
the spirit and scope of the invention as defined by the appended claims. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the description that follows, like parts are marked through the 
specification and drawings with like reference numerals, respectively. The 
figures are not necessarily drawn to scale, and in some instances, have 
been exaggerated or simplified to clarify certain features of the 
invention. One skilled in the art will appreciate many differing 
applications of the described apparatus. 
For the purposes of this discussion, the terms "upper" and "lower," "up 
hole" and "downhole," and "upwardly" and "downwardly" are relative terms 
to indicate position and direction of movement in easily recognized terms. 
Usually, these terms are relative to a line drawn from an upmost position 
at the surface to a point at the center of the earth, and would be 
appropriate for use in relatively straight, vertical wellbores. However, 
when the wellbore is highly deviated, such as from about 60 degrees from 
vertical, or horizontal, these terms do not make sense and therefore 
should not be taken as limitations. These terms are only used for ease of 
understanding as an indication of what the position or movement would be 
if taken within a vertical wellbore. 
FIGS. 1A-1C together depict a semidiagrammatic cross section of a gas lift 
valve assembly 8 shown in the closed position, used in a subterranean well 
(not shown), illustrating: a valve body 10 with a longitudinal bore 12 for 
sealable insertion in a side pocket mandrel 14, a variable orifice valve 
16 in the body 10 which alternately permits, prohibits, or throttles fluid 
flow (represented by item 18--see FIG. 3) into said body through injection 
gas ports 13 in the mandrel 14 and out of said body into the well bore 
through a plurality of gas delivery ports 85, and an actuating means, or 
actuator assembly, shown generally by numeral 36 that is hydraulically 
operated. Further illustrated is: a lower hydraulic actuating piston 38 
located in a downhole housing 40 and operatively connected to a moveable 
piston 42, which is operatively connected to the variable orifice valve 16 
and upper hydraulic actuating piston 39. A spring 44, biases said moveable 
piston 42 and thereby biases said variable orifice valve 16 to the full 
closed position, and control lines 46 communicate with both the lower and 
upper hydraulic actuating pistons 38, 39, respectively, and extends to a 
hydraulic pressure source (not shown). When it is operationally desirable 
to open the variable orifice valve 16, hydraulic pressure is applied from 
the hydraulic pressure source (not shown), which communicates down the 
hydraulic control lines 46 to the upper and lower hydraulic actuating 
pistons 38, 39, respectively, thereby moving the moveable piston 42 uphole 
against the normal biasing force of spring 44, which opens the variable 
orifice valve 16 that is operatively connected thereto. The variable 
orifice valve 16 may be stopped at intermediate positions between fully 
open and fully closed to adjust the flow of lift or injection gas 31 
therethrough, and is held in place by a position holder 33, which is 
configured as described further below to mechanically assure that the 
actuating assembly 36 remains in the desired position as set by the 
operator even if hydraulic pressure provided by hydraulic control lines 46 
is not present in the hydraulic system. The orifice valve 16 is closed by 
indexing of the position holder 33 to a fully closed setting, which will 
allow the spring 44 to fully bias the moveable piston 42 and therefore the 
variable orifice valve 16 operably connected thereto back to the closed 
position. 
As shown in FIG. 1B, the variable orifice valve 16 may include a carbide 
stem 17 and seat 19 to effectively prevent gas flow through the gas lift 
valve assembly 8 into the well conduit when the variable orifice valve 16 
is in the fully closed position. The gas lift valve 8 may also be provided 
with one-way check valves 29 to prevent any fluid flow from the well 
conduit into the gas lift valve 8. The gas lift valve 8 may also be 
provided with a latch 27 so the valve may be remotely installed and/or 
retrieved by well known wireline or coiled tubing intervention methods. As 
shown in FIG. 2, this embodiment of the present invention may also be 
provided with a valve connection collet 11, the structure and operation of 
which are well known to those of ordinary skill in the art. As shown in 
FIG. 6, the actuator assembly, or power unit 36 may also be provided with 
a latch 27 so the actuator assembly, or power unit 36 may be remotely 
installed and/or retrieved by well known wireline or coiled tubing 
intervention methods separate and discrete from the gas lift valve body 8. 
In an embodiment not shown, a position holder 33 may also be provided in 
the gas lift valve body 8 and operably connected to valve stem 17 to 
permit wireline or other removal of the actuator assembly 36 while 
permitting the orifice valve 16 to remain in a selected open position. 
The position holder 33 of the present invention may preferably include a 
rotatable cylindrical sleeve member, or cylindrical cam 33, having first 
and second opposing ends. However, it should be noted that the position 
holder 33 need not be a cylindrical cam and follower arrangement and other 
cam arrangements can be readily perceived by one of ordinary skill in the 
art to function as a selectable and indexable variable position holder 
such as cylindrical cam 33. The cylindrical cam 33 is held in position 
around and affixed to upper actuating piston 39. The cylindrical cam 33 is 
affixed to the upper actuating piston 39, which is in turn affixed to 
moveable piston 42 so that axial movement of either the hydraulic 
actuating piston 38 or the moveable piston 42 will cause a corresponding 
axial movement of the cylindrical cam 33 within the actuator assembly 36. 
As shown in FIGS. 4B, 5B, and 7A-7C, cylindrical cam 33 preferably includes 
a plurality of axial slots 60 of varying length disposed circumferentially 
around the cylindrical cam 33, which are each adapted to selectively 
receive a portion of follower 34 (FIG. 1B) provided at a fixed location on 
the actuator assembly 36. Because the moveable piston 42 is normally 
biased downward with respect to the follower 34, the follower 34 will 
normally be engaged within an upper portion of at least one of the axial 
slots 60 of the cylindrical cam 33, retaining cam 33 thereby supporting 
the cylindrical cam 33 and the moveable piston 42 affixed thereto and 
preventing downward movement of the moveable piston 42 beyond a distance 
determined by the length of the particular axial slot 60 in which the 
follower 34 is disposed. The particular axial slot 60 in which the 
follower 34 is disposed can be selected by the operator, as described 
further below. Therefore, by selecting an axial slot 60 having a desired 
length, the operator can select the desired resting position of the 
moveable piston 42 axially within the actuator assembly 36, which will 
select the desired orifice opening of the variable orifice valve 16, which 
is itself determined by the axial location of the moveable piston 42 
within the actuator assembly 36. 
A particular axial slot 60 having a desired length may be selected by an 
operator by momentarily providing hydraulic pressure through control lines 
46 to either or both of hydraulic chamber 45 and hydraulic actuating 
piston 38, which will cause upward movement of the moveable piston 42 and 
upper and lower acting pistons 38, 39 within the actuator assembly 36. As 
previously described, upward movement of the moveable piston 42 will cause 
cylindrical cam 33 to also move upward axially within the actuator 
assembly 36 relative to the follower 34. A lower portion 60B of each of 
the axial slots 60 on cylindrical cam 33 has a smaller diameter than the 
upper portion 60A of axial slot 60 and is, thereby, recessed from the 
upper portion thereof as best illustrated in FIG. 7B. Therefore, as the 
cylindrical cam 33 is moved upward with respect to the follower 34, the 
follower 34 travels downward with respect to the cylindrical cam 33 and 
into the recessed lower portion 60B of the axial slot 60. The upper 
portion 60A of axial slot 60 is, itself, recessed from the upper portion 
61 of tapered intermediate slot 62 connecting the upper portion 60A of 
axial slot 60 to the successive axial slot 60 immediately neighboring 
axial slot 60, which has a different length 1 from axial slot 60. 
Follower 34 is biased against cylindrical cam 33 by a spring arrangement 
(not shown) so that on subsequent downward movement of the cylindrical cam 
33 with respect to the follower 34 the follower 34 is prevented from 
returning directly to the upper portion of cylindrical cam 33 and, 
instead, is directed against an arcuate portion 63 of axial slot 60 
separating the recessed lower portion 60B of axial slot 60 from the 
elevated upper portion 60A of axial slot 60. The bearing force of the 
follower 34 against the arcuate portion 63 on downward motion of the 
cylindrical cam 33 with respect to the follower 34 is then translated into 
rotatable motion of the cylindrical cam 33 with respect to the follower 
34, which then continues to be engaged within a tapered intermediate slot 
62 of cylindrical cam 33. Each axial slot 60 has an associated tapered 
intermediate slot 62, which connects that axial slot 60 with its 
immediately neighboring axial slot 62 having a different length. 
The tapered intermediate slot 62 of cylindrical cam 33 is tapered from the 
recessed position of the lower portion 60B of axial slot 60 to an elevated 
position having a greater diameter than either the upper portion 60A or 
lower portion 60B of axial slot 60. The tapered intermediate slot 62 also 
has an arcuate path so that as the cam and follower movement translates 
the bearing force of the follower 34 against the arcuate portion 63 of 
axial slot 60, the follower 34 continues along the arcuate path of tapered 
intermediate slot 62, the upward force thereof then being translated along 
a wall of tapered intermediate slot 62 to continue the rotatable movement 
of cylindrical cam 33 with respect to the follower 34. The follower 34 is 
thereby moved along the arcuate path of tapered intermediate slot 62 
toward the immediately neighboring axial slot 60 to select a new axial 
position of moveable piston 42. As the follower 34 enters the immediately 
neighboring axial slot 60, it drops into the recessed upper portion 60A of 
the immediately neighboring axial slot 60, which is recessed from the 
upper portion 61 of the tapered intermediate slot 62 of axial slot 60 so 
that follower 34 cannot immediately return along the arcuate path of the 
tapered intermediate slot 62 from which it had immediately traveled. 
Instead, follower 34 is permitted to travel only in one circumferential 
direction along cylindrical cam 33 and within the axial and intermediate 
slots, 60, 62 therein. The cylindrical cam 33 can thereby be selectively 
and successively indexed between each of the axial slots 60 to selectively 
choose the desired axial slot length 1 and, accordingly, the desired axial 
resting position of moveable piston 42 within actuator assembly 36. 
The upward and downward movement of moveable piston 42 and the 
corresponding indexing of cylindrical cam 33 within the actuator assembly 
36 may be provided by a combination of a continual compressive spring 
force acting against the moveable piston 42 to: (1) bias the moveable 
piston 42 and, consequently, to bias the variable orifice valve 16 toward 
a closed position; and (2) a momentary pressure force acting upward on 
moveable piston 42 and lower hydraulic actuating piston 38 to momentarily 
resist the biasing spring force and axially move the moveable piston 42 
and the cylindrical cam 33 toward an open position to index the 
cylindrical cam 33 to a desired cam position to hold the variable orifice 
valve 16 in a desired position. Because the fluid pressure force is 
provided merely to index the cylindrical cam 33 to a desired cam position 
and because the follower 34 supports the moveable piston 42 in the desired 
operating position against the biasing force of spring 44, the hydraulic 
fluid pressure can be removed after indexing the cylindrical cam 33 to the 
desired cam position. It should be noted that either or both of the 
moveable piston 42 and the lower hydraulic actuating piston 38 can be 
provided with fluid pressure so that the pistons 42, 38 can act either 
together or independently to move the moveable piston 42 toward an open 
position and to select a desired cam position to hold the variable orifice 
valve 16 in a desired position. 
By way of illustration, the operation of the gas lift valve 8 between the 
open and closed positions when the position holder 33 is in open and 
closed cam positions, respectively is shown in FIGS. 4A-5B. FIG. 4A shows 
the position of the variable orifice valve 16 and the operation of the 
one-way check valves 29 when the cylindrical cam 33 is indexed to a fully 
closed position. As shown in FIG. 4B, a slot 60 having slot length 1, 
sized sufficient to permit full downward travel of the valve stem 17, is 
selected to close the variable orifice valve 16 to a fully closed 
position. Injection gas 18 is provided through injection gas port 13 and 
is prevented from delivery through gas delivery ports 85 by seals 15 and 
the sealing engagement between valve stem 17 and valve seat 19. Wellbore 
fluid is prevented from entering the gas valve body 8 by one-way check 
valves 29 held into sealing engagement with the valve body 8 by springs 
86. As shown in FIG. 5B, a slot 60 having slot length l, sized sufficient 
to permit full downward travel of the valve stem 17, is selected to permit 
the variable orifice valve 16 to open to an open position. Injection gas 
18 is provided through injection gas port 13 and is delivered through gas 
delivery ports 85 as valve stem 17 is moved upward from sealing engagement 
with valve seat 19. Wellbore fluid is prevented from entering the gas 
valve body 8 by the fluid pressure of injection gas 18. The injection gas 
18 is allowed to flow through one-way check valves 29 because the pressure 
force of the injection gas 18 is sufficient to overcome both the spring 
force of spring 86 and the hydraulic pressure of the well bore fluid 
acting against the one-way check valves 29, thus opening one-way check 
valves 29 to permit the injection gas to flow through gas delivery ports 
85 and into the well bore. 
It should be noted that the preferred embodiments described herein employ a 
well known valve mechanism generically known as a poppet valve to those 
skilled in the art of valve mechanics. It can, however, be appreciated 
that several well known valve mechanisms may obviously be employed and 
still be within the scope and spirit of the present invention. Rotating 
balls or plugs, butterfly valves, rising stem gates, and flappers are 
several other generic valve mechanisms which may obviously be employed to 
accomplish the same function in the same manner. Further, in the 
embodiment in which a position holder may be provided in the gas lift 
valve body, the axial and intermediate slot arrangement of the cylindrical 
cam may be provided in an outer wall of the valve stem with a follower or 
lug adapted to engage within the slots of the valve stem to provide a 
position holder within the valve body without unnecessarily restricting 
the fluid flow within the valve body and maintaining a dual gas discharge 
ports located at opposing ends of the valve body. 
Whereas the present invention has been described in particular relation to 
the drawings attached hereto, it should be understood that other and 
further modifications, apart from those shown or suggested herein, may be 
made within the scope and spirit of the present invention. Accordingly, 
the invention is therefore to be limited only by the scope of the appended 
claims.