Note: Descriptions are shown in the official language in which they were submitted.
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GAS DISPLACED CHAMBER LIFT SYSTEM WITH
CLOSED LOOP/MULTI-STAGE VENTS
TECHNICAL FIELD
The present invention relates to artificial lift systems. More particularly,
the present
invention relates to chamber lift systems which are used so as to deliver oil,
water and gas from a
well bore to a surface above the well bore. More particularly, the present
invention relates to gas-
displaced chamber lift systems.
BACKGROUND ART
At the present time, it is common to permit oil and gas wells to flow under
their own natural
pressure as long as they will do so and then to apply a mechanical
reciprocating pump to complete
the removal of the liquids. This method, although in general use, is
cumbersome and unsatisfactory.
Because suction will only raise oil for a distance of some thirty-five feet,
it is necessary to have the
pump near the bottom of the well so that it can exert pressure instead of
suction on the liquids
coming out of the well. This involves the use of pump rods of lengths of 5,000
feet or greater. In
many instances when the pump plunger or the valves become worn, it is
necessary to remove the
pump from that depth to replace the worn parts. Furthermore, the collars on
the pump rod wear
rapidly and all the pump parts do likewise because of the small particles of
grit that remain in the
liquid and the whole device is mechanically inefficient because of the
relatively long pump rods that
must be reciprocated to perform the pumping operation.
When the natural flow of liquid from a well has ceased or becomes too slow for
economical
production, artificial production methods are employed. In many cases, it is
advantageous, at least
during the first part of the artificial production period, to employ gas lift.
Numerous types of
equipment for producing liquid by gas lift are available, but they all rely
upon the same general
principles of operation. In the usual case, dry gas consisting essentially of
methane and ethane is
forced down the annulus between the tubing and the casing and into the liquid
in the tubing. As the
liquid in the tubing becomes mixed with gas, the density of the liquid
decreases, and eventually the
weight of the column of the gasified liquid in the tubing becomes less than
the pressure exerted on
the body of liquid in the well, and the flow of liquid occurs at the surface.
While, in some cases,
the dry gas may be introduced through the tubing so as to cause production
through the annulus, this
is not preferred unless special conditions are present.
One known gas lift technique injects gas into the casing, which has been
sealed or packed
off at the bottom of the hole relative to the production tubing. A gas lift
valve is placed in the
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production tubing at the production level, and the gas lift valve permits the
gas to be injected into
or bubbled very slowly into the liquid being produced from the well. This gas
then makes the liquid
in the production tube somewhat lighter and, hence, the natural formation
pressure will be sufficient
to push the liquid up and out of the well. This means that the well can be
produced at a greater rate.
This gas lift technique is known as continuous gas lift.
A further adaptation of this gas lift technique is known as intermittent gas
lift. In this
technique, rather than letting the gas enter the production tube slowly, the
gas is injected into the
production tubing very quickly, in short bursts, thereby forming a large slug
of liquid in the
production tubing above the injected gas bubble. The gas bubble then drives
the slug of liquid in
the production tubing upwardly. The technique is repeated successively,
thereby producing
successive slugs of liquid at the wellhead.
Another type of gas lift tool involves a procedure where a string of
production tubing
extending from the surface to the zone of interest is provided with a number
of gas lift valves
positioned at spaced intervals along the length of the tubing. Gas is injected
from the annulus
between the tubing and the well pipe through the gas lift valves and into the
tubing for the purpose
of forcing liquid upwardly to the surface and ultimately into a flowline that
is connected with the
production tubing. Gas lift systems for liquid production are quite expensive
due to the cumulative
expense of the number of gas lift valves that are ordinarily necessary for
each well. Moreover, each
of the gas lift valves must be preset for operation at differing pressures
because of the vertical
spacing thereof within the tubing string and because the valves must function
in an interrelated
manner to achieve lifting of liquid within the tubing string.
In the past, various patents have issued relating to such gas lift systems.
For example, U.
S. Patent No. 5,671,813, issued on September 30, 1997 to P. C. Lima describes
a method and
apparatus for the intermittent production of oil. In this method, two
production strings extend
downwardly from a wellhead of an oil well to a point adjacent a producing
region. The lower ends
of the two production strings are connected by a coupling which allows a
mechanical interface
launched adjacent to the wellhead of one of the production strings to descend
along the production
string through the coupling and upwardly through the other production string
to displace oil from
the production strings to a surge tank. High pressure gas is utilized to move
the mechanical
interface through the production strings and suitable valves are provided for
controlling the flow of
gas and oil through the production strings.
U. S. Patent No. 5,562,161, issued on October 8, 1996 to Hisaw et al.
describes a method
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of accelerating production from a well. This method includes the steps of
installing a venturi device
within the well. A gas is injected within the annulus and introduced into the
well. The venturi
device creates a zone of low pressure within the well as well as accelerating
the velocity of the
production fluid so that the inflow from the reservoir is increased.
U. S. Patent No. 5,407,010, issued on April 18, 1995 to M. D. Herschberger
teaches an
artificial lift system and method for lifting fluids from an underground
formation. This artificial lift
system includes a production tubing through which the fluid is carried from
the formation to the
surface and a pressure reducer, such as a venturi, connected to the production
tubing to artificially
raise the level of the fluid in the production tubing above the static level
associated with the head
pressure of the fluid in the formation.
U. S. Patent No. 5,217,067, issued on June 8, 1993 to Landry et al. describes
an apparatus
for increasing flow in an oil well which includes an injection valve so as to
enable gas to be inj ected
and to cause the oil or other liquid within the well to be lifted to the
surface. The valve has a valve
body having an inlet at one end and an outlet at the other end which are
adapted to be fitted into
conventional production oil tubing. A gas injection port opens into the outlet
of the valve body and
there is at least one gas inlet opening in a side of the valve body. This gas
inlet opening is
connected to the gas injection port. This enables compressed gas to be sent
down the well between
the casing and the tubing and injected through the gas injection port and into
the flow of oil.
U. S. Patent No. 5,211,242, issued on May 18, 1993 to Coleman et al. describes
a chamber
in a well which is connected to two externally separate tubing strings to
unload liquid which is
applying backpressure against a formation so that the production of fluid from
the formation is
obstructed. Volumes of the liquid are intermittently collected in the chamber
and lifted out of the
well through one of the tubing strings in response to high pressure gas
injected solely into the
chamber through the other tubing string.
U. S. Patent No. 4,708,595, issued on November 24, 1987 to Maloney et al.
describes an
intermittent gas-lift apparatus and process of lifting liquids. This apparatus
includes a chamber on
the downhole end of a production tubing in communication with a sidestring
tube. The sidestring
tube is in communication with the high pressure gas stored within the casing
and above and below
a packer. A valve in the sidestring tube permits the entrance of a lifting gas
into the chamber to lift
the liquids flowing therein to the surface. A surface bleed-down system
minimizes the pressure in
the production tubing. This increases the pressure differential between the
formation and the
interior of the casing and lifting chamber during the operation of the
apparatus.
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German Patent No. 23 64 737, published on July 10, 1975, teaches a compressed
air lift
pump for deep wells in which the pump has a number of stages one above the
other. Liquid is raised
by air from the reservoir of one stage to the reservoir of the next. Each
stage has two air supply
pipes which contain three-way valves operated by an electronic timer to admit
and release air
alternately.
Soviet Patent No. 1204-700-A teaches an intermittent gas lift system for a
pump well which
includes a tubing, a packer, a substitution chamber and intake valve, lift
starter valves and working
valves with a seal and a seat over a space connected to the chamber. The
rising level of fluid in the
chamber raises the float so as to close off ports and thus raise pressure
above the diaphragm so as
to clear the valve and transfer gas to the chamber. This gas forces the fluid
into the tubing and uses
a pressure gradient to hold the ports closed. Gas eventually enters the tubing
after all fluid has been
expelled, thus opening the two ports by lowering the float back down. Gas is
removed entirely from
the chamber by the incoming fluid.
Soviet Patent No. 570697 teaches an oil production facility including a
displacement
chamber, two strings of compressor pipes of which one is coupled to the
surface drive. The gas
from the chamber is recuperated and expanded. When one vessel is empty, fluid
is drawn into the
displacement chamber. The second vessel pumps oil over into the empty vessel
so as to raise its
pressure to the point required to drive the hole fluid over into the lifting
string to the surface. Once
the fluid in the chamber reaches the bottom of the lift string, the motor
reverses so as to turn an
electric shaft and compress the gas in the first vessel to repeat the process
in a second hole.
U.S. Patent No. 3,617,152, issued on November 2, 1971 to Leslie L. Cummings,
discloses
a method and apparatus for the artificial lifting of well fluids. In
particular, this device utilizes an
automatic well pump which utilizes compressed power gas to displace well
production fluids from
the well bore to the earth surface. Power gas is exhausted from the pump so as
to be collected in
a chamber at a desired predetermined superatmospheric pressure to reduce the
energy required to
compress the air. This device utilizes gas assist lifting so as to move the
liquid, in stages, to the
surface. Also, the device uses the compressed gas, as opposed to the vented
gas, for the gas assist.
A publication of Otis Engineering Corporation, dated 1982, and entitled "Otis
Single and
Dual-Acting Gas Pumps" describes a gas assist system in which the pump
displaces a barrel of oil
with a barrel of gas volume at a lift depth pressure. When the gas pressures
are too low to lift wells
by positive displacement, the gas pump can be aligned with gas lift to lift
deeper with lower
pressures. The gas lift supply comes from the compressor at various stages
along the liquid string.
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Patent No. 5,S06,598, issued on Septeznber 15, 199s, to M. Ama_ni describes an
anpara.t'as for rellloving iluids from underu7ound wells, Thls dev7ce includes
a supply valve having
an open supply position to supply gas to the chamber and a closed supply
position. The device
further includes a vent valve having an open vent position to vent ~,as from
the chaniber and a closed
vent position. An actuator conununicates with a source of pressurized fluid at
the stirfacc for
actuating the supply and vent valves, The actuator moves the supply valve to
the open position and
the vent valve to the closed position, and alternately moves the vent valve to
the open position and
the supply valve to the closed supply position.
A major problem with the aforedescribed artificial lift systems is that they
do not worlc
effectively in deep well and sour gas enviroiu-iients. In particular, at
depths of d eater thzaz 10,000
feet, the tciuperature range encotuitered can be approximately 300 degrees
Fahrenheit. As such,
any mechanical pumping apparatus will not work effectively at such temperattu-
es, At such great
depths, the rod punip devices and subnlersible pttnip apparatus do not
effectively deliver oil and gas
to the surface. For exan-iple, at such great depths, the pun-ip rod will have
an extreme length which
cannot be easily reciprocated baclc and forth. Fttrthernzore, the cost
associated with such a lengthy
pumprodwouldnotallowforefficientproduction. Thehightenlperature andpressures
encountered
at such depth cause submersible pumps and hydraulic pumps to fail quicl:ly.
In those systenis in which the intermittent production of "slugs" of oil is
utilized, such
systems are ineffective at such depths. In each case in whicli a "slug" of oil
is produced, the gas
must be relied upon so as to deliver such a slug to the surface. At great
depths, this can take a great
deal of time so as to produce an economical anlouilt of oil. Furthermore, the
pressure and en.ergy
required so as to push such a slug to the stu=face may exceed the value of
t11c actual procluction.
Production at such a depth is fiu-Cher conlplicated by situatiozis in which a
corrosive sour gas
is encotuitered. This is particularly true in those cases in which oil atld
gas must be removed fronl
Smackover wells.
U.S. Patent No. 602] 849 Nvhich issued hebruary 8, 2000, to the present
applicant, descri.bes the original fornl of the ;;as displaced chamber lift
system. After
experimeiltation, study aud analysis, it was found that it was important to
have a gas displaced
chamber li-ft system that operated in a relatively conti.nuous mode. In the
single chamber gas
displaced chanzber lift system, liquid would acetuuulate in the single
ehamber, After sufficient
liquid llad acetunulated in the chamber, then the valve would open so as to
cause tlts pressurized gas
to pass through the power gas string v; ith sufficient pressure so as to
evacuate the chambcr of the
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iiquid anid to pass the liquid from the outlPt of tile chamber into the liquid
stni:a,. 2~fier tlie liqc.id
would pass to the liquid string, the pressurized `Tas from t1_ie uower vas
suing v,-ouid be blocl:::d and
the remaining ~as ~~,~ithin the chamber would be vented to the stufac.e. It
was found that duri:i`. the
process of evacuatir.`T the chrsnber and durinc, the process of venting the
_Qas, thPre vvas a period of
time in which production ceased. It was found to be desirable to allow
production (i.e, the
acctu.nulation of liquid in the chaYnber) to continue during the evacuation
and venting process, As
such, a. clouble chamber approach was devisecl and discloscd in this piior
application. Parent patent
application Scrial Number 09/201,017 described a double chaniber approach in
which one of tlle
chambers was stacked on top of the other chaniber or in which one chanzber was
located interior of
and in concentrie relationsliip with the other chamber. Afi:er experimentation
and analysis, it was
fotuld that such ail arrangement was difficult to configure within the well
bore. Additionally, the
stacked arrangements could occasionally produce varying quantities of liquid
within the respective
cllatnbers due to the head pressure within the well.
U.S. Patent No. 6237692 which issued May 29, 2001, to the present
Applicant describes a modified form ofthe gas displaced chamber liftsystem.
After experiment and
analysis, it was found that the efficiency of the subject matter of this
patent application could be
inlproved by utiliziilg the vented gases for the purposes of reducing the
weight of the liquid in the
liquid string. Since the gas displaced chamber lift system would veilt the
gases from the chanlber,
it was felt that the vented gases could be put to better use by sil-tlply
reinfecting such gases into the
liquid string. However, because of the pressures within the liquid string, the
gas could not be
injected, efficiently, into the liquid string when the pressures witlain the
liquid string are too great.
Ftu-thermore, U.S. Patent Application Serial No. 09/339,482 describes a
valving system placed
exterior to the liquid sti-ing. As such, in order to accormnodate botll the
shifting valve and the liquid
string, the shifting valve required a niiniinal aniount of space. Upon
fw.=tller experimentation and
analysis, it was fotuld that a better design could be achieved for the
placement of the shifting valve
within the well bore.
With the afore-described systems of the pz-csent inventor, all of the work
required for the
~cneration of the pressure in the power gas string n~ust be produced by the
compressor. As such,
the compressor will take arnbient air, and, through the tise of niultiple
stages, elevate such pressure
to greater than 5,000 p.s.i.. It would be desirable to improve the efficiency
of such a multi-stage
compressor by introducuig the pressurized gas from the do-\vnhole vented gas.
It is an object of the present invention to provide an artincial lift systenz
which wort.s
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effectively at depths of greater than 10,000 feet.
It is a further object of the present invention to provide an artificial lift
system which can
operate in a high temperature environment at the bottom of the well.
It is another object of the present invention to provide an artificial lift
system in which
production from the liquid string occurs continuously without the need for
transporting a "slug" of
oil to the surface.
It is another object of the present invention to provide an artificial lift
system which works
effectively in highly corrosive sour gas environments.
It is another object of the present invention to provide an artificial lift
system which can lift
liquid volumes of approximately 500 barrels per day.
It is a further object of the present invention to provide an artificial lift
system which can
operate in a very "gassy"/high API oil gravity environment.
It is still a further object of the present invention to provide an artificial
lift system which
can handle saturated brines of greater than 200,000 parts per million.
It is still another object of the present invention to provide a double
chamber gas displaced
chamber lift system in which at least one chamber is continuously available
for the accumulation
of liquid therein.
It is a fitrther object of the present invention to provide a double chamber
gas displaced
chamber lift system in which the chambers can be alternately evacuated and
vented without
interrupting production capacity.
It is still a further object of the present invention to provide a double
chamber gas displaced
chamber lift system which is easy to configure and easy to install within the
well bore and which
is not subject to varying head pressures within the well bore.
It is still a further object of the present invention to provide an artificial
lift system which
can improve efficiency by reinjecting the vented gas into the liquid string.
It is another object of the present invention to provide an artificial lift
system which
maximizes the space in the well bore available for the installation of the
shifting valve.
It is still a further object of the present invention to provide an artificial
lift system whereby
the pressurized gas is conserved and reused in an efficient and economical
manner.
These and other objects of the present invention will become apparent from a
reading of the
attached specification and appended claims.
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SUMMARY OF THE INVENTION
The present invention is an artificial lift system for use in a well bore that
comprises at least
one chamber having an inlet and an outlet, a power gas string in valved
communication with the
chamber, a liquid string in valved communication with the outlet of the
chamber, at least one vent
in valved communication with the chamber and adapted to pass a vented gas from
the chamber, a
compressor connected to the power gas string and adapted to pass a pressurized
gas into the power
gas string and a valve connected to the power gas string and to the chamber.
The vent is connected
to the compressor and is adapted to pass the vented gas into the compressor.
The valve is adapted
to selectively allow the pressurized gas to enter the chamber so as to cause a
liquid in the chamber
to pass through the outlet of the chamber and into the liquid string.
In the present invention, the vent comprises a first vent in valved
communication with the
chamber and connected to the compressor and a second vent in valved
communication with the
chamber. The first vent is adapted to pass vented gas of a first pressure
range from the chamber and
into the compressor. The second vent is adapted to pass vented gas of a second
pressure range into
the well bore. The first pressure range is greater than the second pressure
range.
In the present invention, the compressor is a multi-stage compressor. The vent
is connected
to one stage of the compressor. In particular, the compressor has a first
stage, a second stage and
a third stage. The third stage is connected to the power gas string. The vent
is connected to an inlet
of the third stage. The first pressure range includes pressures of greater
than 2,500 p.s.i. The second
vent is adapted to pass the vented gas of the second pressure range into the
annulus of the casing.
The annulus of the casing is connected to an inlet of the first stage such
that the vented gas of the
second pressure range passes into the compressor. The compressor is adapted to
pass pressurized
gas of greater than 5,000 p.s.i. into the pressurized gas string.
In the preferred embodiment of the present invention, the chamber comprises a
first chamber
having an inlet and an outlet, and a second chamber having an inlet and an
outlet. The second
chamber is arranged in parallel relation to the first chamber. The first
chamber is arranged in spaced
and separate relationship to the second chamber. The first chamber has an
approximately equal
volume as the second chamber. The first chamber has a top end aligned in a
horizontal plane with
a top of the second chamber. The first chamber has a bottom end aligned in a
horizontal plane with
a bottom of the second chamber. The valve is movable between a first position
and a second
position. The first position allows pressurized gas from the power gas string
into one of the first and
second chambers while blocking pressurized gas from entering another of the
first and second
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chambers. The second position allows presurized gas into
another of the first and second chambers while blocking
pressurized gas from entering the other chamber. The valve is
also adapted to switch between the first and second vents
relative to a pressure of the vented gas.
According to one aspect of the present invention,
there is provided an artificial lift system for use in a well
bore comprising: at least one chamber having an inlet and an
outlet; a power gas string in valved communication with said
chamber; a liquid string in valved communication with said
outlet of said chamber; a first vent in valved communication
with each said chamber; a second vent in valved communication
with each said chamber; a compressor connected to said power
gas string and adapted to pass a pressurized gas into said
power gas string, said first vent connected to said compressor
and adapted to pass vented gas of a first pressure range from
said chamber into said compressor, said second vent adapted to
pass vented gas of a second pressure range into the well bore;
and a valve connected to said power gas string and to said
chamber, said valve adapted to selectively allow the
pressurized gas to enter said chamber so as to cause a liquid
in said chamber to pass through said outlet of said chamber and
into said liquid string.
According to another aspect of the present
invention, there is provided an artificial lift system for use
in a well bore comprising: at least one chamber having an inlet
and an outlet; a power gas string in valved communication with
said chamber; a liquid string in valved communication with said
outlet of said chamber; at least one vent in valved
communication with said chamber, said vent adapted to pass a
vented gas from said chamber; a compressor connected to said
power gas string and adapted to pass a pressurized gas into
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said power gas string, said vent connected to said compressor
and adapted to pass the vented gas into said compressor, said
compressor having a first stage and a second stage and a third
stage, said third stage connected to said power gas string,
said vent connected to an inlet of said third stage; and a
valve connected to said power gas string and to said chamber,
said'valve adapted to selectively allow the pressurized gas to
enter said chamber so as to cause a liquid in said chamber to
pass through said outlet of said chamber and into said liquid
string.
According to still another aspect of the present
invention, there is provided an artificial lift system for use
in a well bore comprising: a first chamber having an inlet and
an outlet; a second chamber having an inlet and an outlet, said
second chamber being arranged in parallel relation to said fist
chamber, said first chamber having a top and aligned in a
horizontal plane with a top of said second chamber, said first
chamber having a bottom end aligned in horizontal plane with a
bottom of said second chamber; a power gas string in valved
communication with said first chamber and said second chamber;
a liquid string in valved communication with said outlet of
said first chamber and with said outlet of said second chamber;
at least one vent in valved communication with said fist
chamber and with said second chamber said vent adapted to pass
a vented gas from said fist and second chambers; a compressor
connected to said power gas string and adapted to pass a
pressurized gas into said power gas string said vent connected
to said compressor and adapted to pass the vented gas into said
compressor; and a valve connected to said power gas string and
to said first and second chambers said valve adapted to
selectively allow the pressurized gas to enter said first and
second chambers so as to cause a liquid in said first and
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second chambers to pass through the respective outlets of said
first and second chambers and into said liquid string.
According to yet another aspect of the present
invention, there is provided an artificial lift system for use
in a well bore comprising: a first chamber having an inlet and
an outlet; a second chamber having an inlet and an outlet, said
second chamber arranged in parallel relation to said first
chamber; a power gas string in valved communication with said
first and second chambers; a liquid string in valved
communication with said outlet of said first chamber and with
said outlet of said second chamber; a first vent connected to
said compressor and adapted to pass vented gas of a first
pressure range from said first and second chambers into said
compressor; a second vent adapted to pass vented gas of a
second pressure range from said first and second chambers; a
compressor connected to said power gas string and adapted to
pass a pressurized gas into said power gas string; a valve
connected to said power gas string and to said first and second
chambers, said valve adapted to selectively allow the
pressurized gas to enter said first and second chambers so as
to cause a liquid in said first and second chambers to pass
through the respective outlets of said first and second
chambers and into said liquid string, said valve movable
between a first position and a second position, said first
position allowing pressurized gas into one of said first and
second chambers while blocking pressurized gas from entering
another of said first and second chambers, said second position
allowing pressurized gas into said another of said first and
second chambers while blocking pressurized gas from entering
said one of said first and second chamber, said valve adapted
to switch between said first and second vents relative to a
pressure of the vented gas.
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According to a further aspect of the present
invention, there is provided an artificial lift system for use
in a well bore comprising: at least one chamber having an inlet
and an outlet; a power gas string in valved communication with
said chamber; a liquid string in valved communication with said
outlet of said chamber; a multi-stage compressor connected to
said power gas string and adapted to pass a pressurized gas of
greater than 5,000 p.s.i into said power gas string; a first
vent in valved communication with each said chamber, said first
vent connected to said multi-stage compressor and adapted to
pass vented gas of a first pressure range from each said
chamber and into said multi-stage compressor; a second vent in
valved communication with each said chamber, said second vent
adapted to pass vented gas of a second pressure range from each
said chamber; and a valve connected to said power gas string
and to said chamber, said valve adapted to selectively allow
the pressurized gas to,enter said chamber so as to cause a
liquid in said chamber to pass through said outlet of said
chamber and into said liquid string.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 is a diagrammatic cross-sectional view
showing the configuration of the artificial lift system of the
present invention.
FIGURE 2 is a cross-sectional view illustrating the
preferred embodiment of the artificial lift system in
accordance with the present invention.
FIGURE 3 is a diagrammatic illustration of the
arrangement of the multi-stage compressor.
FIGURE 4 is a flow diagram showing the operation of
the shifting valve in association with the preferred embodiment
of the present invention.
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DETAILED DESCRIPTION OF THE PRESENT INVENTION
Reffering to FIGURE 1, there is shown
diagrammatically the.artificial lift system 10 in accordance
with the teachings of the present invention. The artificial
lift system 10 is used for the extraction of oil, water and gas
from the well bore 12. The artificial lift system 10 includes
a chamber 14, a power gas string 16, a liquid string 18, a
first vent stack 20, a second vent stack 21, and a multi-stage
compressor 22. A suitable valving mechanism 24 is provided in
association with the chamber 14. The valving mechanism 24 will
be described in greater detail in connection with the
illustration of FIGURES 2 and 4.
It can be seen in FIGURE 1 that the chamber 14 is
located in the well bore 12 below perforations 26 that are
formed in the well bore 12. The chamber 14 could also be
positioned above the perforations 26 in the well bore 12. The
perforations 26 can be associated with perforations that are
formed in an existing casing or in an existing production
tubing. The power gas string 16 will extend from the third
stage 28 of multi-stage compressor 22 to the chamber 14. The
valving mechanism 24 is interactively connected with the power
gas string 16 so as to allow pressurized gas to enter the
chamber and to cause any liquid in the chamber 14 to pass
through an outlet in the chamber 14 and into the liquid
string 18. Any liquids within the chamber 14 will enter the
liquid string 18 in a continuous flow line along the liquid
string 18. The liquid string 18 extends from the chamber 14 to
the wellhead area 29. As such, liquid, such as oil, can be
removed from the well bore 12. Vent stack 20 is illustrated as
extending from the chamber 14. Vent stack 20 extends from
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chamber 14 so as to deliver spent pressurized gas through the well bore 12 and
up and into the
multi-stage compressor 22. In particular, the spent power gas delivered
through vent stack 20 is
delivered to the inlet of the third stage 28 of the multi-stage compressor 22.
The second vent stack
21 extends from the chamber 14 and upwardly through well bore 12. The vent
stack 21 should have
a suitable height so that the outlet 30 of the vent stack 21 resides in a
location above the perforations
26. The vent stack 21 does not have to extend to an above-earth location. As
can be seen in
FIGURE 1, the vent stack 21 releases spent power gas into the annulus 31 of
the casing of the well
bore 12. The spent power gas from the annulus 31 passes through low pressure
line 33 to the first
stage 35 of multi-stage compressor 22.
In FIGURE 1, the compressor 22 should be a compressor which can produce at
least 5,000
p.s.i. of gas pressure. This relatively large amount of gas pressure is
required so as to push the entire
line of liquid from the chamber 14 in a continuous ungasified line through the
liquid string 18. The
valving mechanisms and the associated tubing should have a suitable integrity
to withstand such
pressures. The compressor 22 is amulti-stage compressorhaving first stage 35,
second stage 37 and
third stage 28. A multi-stage compressor, which is known in the art, simply
causes the pressures
to increase between the stages. For example, first stage 35 may have a suction
pressure of 300
p.s.i.g., the second stage may have an inlet pressure of 800 p.s.i.g. and the
third stage may have an
inlet pressure of 2,200 p.s.i.g. The 5,000 p.s.i. of gas pressure emitted by
compressor 22 passes
from the outlet 39 of the third stage 28 into the power gas string 16.
Importantly, in the present invention, the power gas string 16, liquid string
18, and the vent
stack 20 can be formed of coiled tubing. Such coiled tubing can be run in and
pulled from the well
together as siamese strings. This provides an enormous efficiency in the
installation and removal
of such power gas and liquid strings.
FIGURE 2 shows the preferred embodiment of the artificial lift system 40 of
the present
invention. The artificial lift system 40 is located in a well bore 42. In this
embodiment 40 of the
present invention, a first chamber 44 is positioned within the well bore 42
adjacent to a second
chamber 46. The chambers 44 and 46 have approximately the same volume or
capacity. The
chambers 44 and 46 are arranged in side-by-side and parallel relationship. As
can be seen, the top
48 of chamber 44 is aligned in the same horizontal plane with the top 50 of
chamber 46. Similarly,
the bottom 52 of chamber 44 is located in the same horizontal plane with the
bottom 54 of chamber
46. It has been found that this side-by-side relationship of the chambers 44
and 46 can be more
easily installed within the well bore without undue mechanical manipulation or
structural
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engineering. Furthermore, the positioning of the chambers 44 and 46, at
approximately the same
location within the well bore avoids any differences in the loading of the
chambers 44 and 46
because of the head pressure within the well. The arrangement of the chambers
44 and 46 in the
side-by-side spaced relationship facilitates the automatic and continual
cycling of the artificial lift
system 40 without uneven liquid accumulation within the chambers 44 and 46.
As can be seen in FIGURE 2, a power gas string 56 is arranged so as to be in
valved
communication with each of the chambers 44 and 46. A liquid string 58 also
extends so as to be
in valved communication with each of the chambers 44 and 46. A first vent
stack 60 is further
connected so as to be in valved communication with the chambers 44 and 46. The
vent stack 60
extends through the well bore 42 so as to be connected with the compressor (as
described herein
previously in association with FIGURE 1). A second vent stack 62 is also
connected in valved
communication with the chambers 44 and 46. The outlet 64 of the second vent
stack 62 should be
located above the perforations 66 in the casing of the well bore 42. As such,
the vent 62 is suitable
for venting gas into the annulus 68 of the well bore 42.
So as to allow the liquids from the annulus 68 of the well bore 42 to enter
the chambers 44
and 46, a series ofpassageways and check valves are provided. Chamber 44 has
an inlet 66 located
at bottom of the bottom packing 69 of the system 40. A check valve 70 is
affixed over inlet 67. As
such, liquid from the annulus 68 will be free to enter the passageway 72
through the inlet 67 and the
check valve 70. This liquid will flow through passageway 72, through
passageway 74 and into the
interior of the first chamber 44. During the injection of pressurized gas from
the power gas string
56 into the chamber 44, any liquids on the interior of the chamber 44 will
exit through passageway
74, through passageway 76, through check valve 78, through passageway 80 and
into the liquid
string 58. Similarly, liquids will be able to enter the second chamber 46
through the inlet 82 located
at the bottom of the bottom packing 69. The liquid will enter inlet 82 and
flow through passageway
84, through check valve 86, through passageway 88, through passageway 90 and
into the interior
of chamber 46. Check valve 86 will assure that liquids do not flow downwardly
through chamber
46 and outwardly through the inlet 82. During the injection of pressurized gas
from the power gas
string 56, any liquids within chamber 46 will flow outwardly therefrom and
into the liquid string
58 through passageway 90, through passageway 92 and outwardly into the liquid
string 58 through
check valve 94. Check valve 94 will assure that the liquids in the liquid
string 58 do not flow
backwardly into the second chamber 46. A shifting valve 100 is provided so as
to have an action
similar to that described herein previously. Although a shifting valve can
have any number of
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configurations, the technology for the formation of shifting valve 100 is
readily available. The
shifting valve 100 should be wireline retrievable from the surface. Unlike the
parent application to
the present application, shifting valve 100 is placed directly in the liquid
string 58 rather than in a
side pocket mandrel. Upon experimentation, it was found that the space
requirements for the
shifting valve 100 can be greatly increased if the shifting valve 100 is
placed directly in the liquid
string 58. It can be seen that a bypass 102 is formed in the liquid string 58
so as to assure that the
liquids will flow continuously therethrough. The placement of the shifting
valve 100 within the
liquid string 58 will allow a shifting valve having a diameter of 21/4 inches
to be used rather than the
1 1/4 inch diameter shifting valve required when used in the side pocket
mandrel.
In its simplest form, the shifting valve 100 is movable between two positions.
When the
shifting valve 100 is in its first position, it connects the power gas string
56 to connect to the first
chamber 44 through passageway 104. In the same position, passageways 106 and
108 are blocked
from communication with the chamber 44. When the shifting valve 100 is in this
first position, it
connects passageways 106 and 108 of vent stacks 60 and 62, respectively, with
the second chamber
46. As such, the valve will operate so as to vent any pressurized gases
through passageways 106
and 108 from chamber 46. In this position, passageway 110 of the power gas
string 56 is blocked
from passageway 112 associated with the second chamber 46. This will prevent
chamber 46 from
connecting to the power gas string 56. When the shifting valve is in this
first position, power gas
will displace any liquids in the chamber 44 and into the liquid string 58.
Chamber 46 will
depressurize and allow any gases to flow therefrom into the vent stacks 60 and
62. Simultaneously,
chamber 46 will begin to be filled with liquid from the annulus 68 of the well
bore 42.
When the shifting valve 100 switches to a second position, the connections are
reversed.
In other words, chamber 44 will communicate with the vent stacks 60 and 62
through passageways
104, 106 and 108. Chamber 46 will communicate with the power gas string 56
through
passageways 110 and 112. In this manner, the present invention is able to
achieve simultaneous
displacement of one chamber while the other chamber is being depressurized and
refilled. It is
believed that this double chamber configuration can lift twice as much liquid
as a single chamber
arrangement. Production capacity is not interfered with since at least one of
the chambers 44 and
46 will be continuously receiving liquid from the annulus 68 through
respective inlets 67 and 82.
This arrangement allows continuous cycling of the various components rather
than the on/off
arrangement associated with a single chamber arrangement.
Within the concept of the present invention, it is to be noted that the
shifting valve 100 can
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move to other positions, if desired. Under certain circumstances, it may be
desirable that the
pressurized gas accumulate within the power gas string 56 before being
introduced into either of the
chambers 44 and 46. As such, the shifting valve 100 can move to a third
position in which
pressurized gas flow is blocked from entering either of chambers 44 and 46. In
such an
arrangement, the chambers 44 and 46 can simultaneously vent to the atmosphere
or be filled with
liquid from the annulus 68. Another position of the shifting valve 66 would
have chambers 44 and
46 communicating with each other and not in communication with vent stacks 62
and 64 nor the
power gas string 58. This position of the shifting valve 66 would allow the
flow from one chamber
to the other. This position of the shifting valve 66 might occur at the point
in the lift cycle in which
one chamber had completed the displacement of liquids into the liquid string
60 (filled with power
gas) and the other chamber had been vented and filled with liquids from the
annulus 70. The flow
of gas from the just displaced chamber would "precharge" the liquid filled
chamber with high
pressure gas and thus raise the pressure in said liquid filled chamber. This
precharge would reduce
the volume of power gas that would be required to raise the pressure in the
liquid filled chamber to
the pressure required to displace liquids from the chamber to the liquid
string 60. The precharge
stage will reduce the energy requirements of the system and thus make it more
efficient.
It is also important to note that the valve 100 can be constructed so as to
assure that a first
pressure of vented gas from the chambers 44 and 46 will pass through vent
stack 60 and that a
second range of pressures of vented gases from the chambers 44 and 46 will
pass through vent stack
62 into the annulus 68. In order to achieve the efficiencies of the present
invention, the shifting
valve 100 should move, in such a manner, that vented gases of greater than
2,500 p.s.i. are
delivered, initially, into the vent stack 60 for delivery to the third stage
of the compressor 22. When
the pressures have diminished to a certain level, the shifting valve 100 can
move downwardly so
as to assure that the gases with pressures of less than 2,500 p.s.i. or vented
to the annulus 68.
Although this valving arrangement associated with the vent stacks 60 and 62
can be carried out by
the shifting valve 100, it is also possible to carry out such shifting at the
surface, as associated with
a single vent stack, or otherwise within the well bore 42. In other words, a
valve can be used so as
to shift gas flow from one vent to the other when the pressure of the gas
within the particular vent
has increased to the desired range of pressure. It is to be noted that when
the shifting valve 100
initially shifts, then very high pressure gases from the respective chambers
44 and 46 are initially
released. This initial release of pressure should be passed into the vent
stack 60. The residual
pressure release should go through the second vent stack 62. As such, rather
than being pressure-
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based, the shifting valve 100 can be responsive to timing.
FIGURE 3 diagrammatically illustrates the configuration of the compressor 22.
It can be
seen that in FIGiJRE 3 that the compressor 22 has a first stage 35, a second
stage 37, and a third
stage 28. The third stage 28 is connected so as to deliver pressurized gas of
greater than 5,000 p.s.i.
to the power gas string 16 and ultimately to the chambers within the
artificial lift system 10 of the
present invention. The third stage 28 will receive, at its suction side, the
pressurized gases emitted
from the outlet 120 of the second stage 37. These pressurized gases will pass
along line 122 into
the suction side 124 of the third stage 28. Additional pressurized gases will
be received from the
vent stack 60. As such, the present invention conserves pressure requirements
by introducing such
pressures at the area between the second stage 37 and the third stage 28, or,
as stated otherwise, to
the inlet (or suction side 124) of the third stage 28.
The first stage 35 has its outlet 126 delivering pressure to the suction side
128 of the second
stage 37. The first stage 35 has its inlet (or suction side) 130 connected to
conduit 33. Conduit 33
is connected to the casing annulus so as to draw the residual pressure from
the interior of the well
bore 12. As such, gases emitted by the second vent stack 62 can be introduced
to the first stage 35
of the multi-stage compressor 22.
An analysis conducted of the present invention revealed that the present
invention greatly
diminishes horse power requirements while improving lifting efficiency. The
empirical data as
shown on the following table:
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TABLE I
V y Z = N b
O
V ot7 .K.
a p p f
W = f T P P f Y N N I!~
Z x
W
Z q _
ZpFe~=3 ~~f n n
M H
a
qx x O O a Y N a N Y~ N
~ N ~~" lit Y f f f !
ar
UW o~m
ip n N ~O h YI O u.~
(~ J p ~p (A n õ Y N N '
~ U 3 N r ,~f l ~ O
~.a.. N rl N 10 10 0~ ^
z
w
x
C> K- r . n m N o ~ n ~ a
< LL = O1 e n C m
A o~ O V ^ ~ ~ N A a 0 n N
y a f 4'~ T r n ~b9 1'!
~ Q IlJ.U ~ f
N LL s
~7 ^ (7 a w O f ~m' ~ . 3 ~= O O
a C7 w t~a~a g n n n.-
a p a
N y Z~ D`.
}'`~! a
J W y 7 y
O m Z f' Z
m a J LL 3 ¾¾¾L x_ n n - n f f W
U " iy
C W Q LL~ y~j y <
W llWllll
U N q z
~ m W
J IL >
1~- LL `i C7 y~ N Np~ la1 ~pV1 o O W
a YI O 0 u l'1 i~' ^ CI ~ A 1Il Y 2
p C7 < $ U ~.. x
4 ~ r
~
w r
3 ]_ c1 m W
ri O Y f
r
m r- m f,2j
w Uj a = p U 4 y~ ^ ^ ^ o o e o =
0 ~ m a m W V Z
y 2_ G 4u W z o
n O o
H p rZ m lL W F 1~
> Q LL ~ z N Z G
Q LL d' (zL N u p
a Z D
O W
O ~ W a ~Q~( Gpq !Lq!~~ O ~ O O S O
m a m W i~1 m _" =~ t Q n Cl N N
q u! K a d
H ~ u 4 - a U
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According to the data shown on the attached sheet, it can be seen that the use
of the multi-stage vent
system of the present invention reduces horse power from 540 horse power to
343 horse power.
This increases lifting efficiency from 40% to 63%. In order to do this, the
pressure in the chamber
would have to be reduced from the initial pressure of 6,190 p.s.i. to 2,500
p.s.i. by flowing this
volume of gas up the vent stack 60 to the third stage 28 of the compressor 22.
This improvement
in efficiency is dramatic and is applicable to both single and double chamber
systems.
FIGURE 4 illustrates diagrammatically the operation of the shifting valve 100
and how it
operates so as to pass the gases from and into the system. The table, as
follows, describes the
operation of the shifting valve, or valves, associated with the operation of
the present invention.
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TABLE II
DESCRIPTION OF LIFT CYCLE
GDCL-DOUBLE CHAMBER
PRECHARGE OF CHAMBERS & GAS LIFT ASSIST OR CLOSED LOOP/MULTISTAGE VENT
STAGE # STATUS OF CHAMBERS POSITION OF VALVES
CHAMBER A CIiAMBER B #l #2 # 3 #4 #5 #6 #7
CYCLE BEGINS WITH CHAMBER A VENTED, REFILLED WITH LIQUID AND READY FOR
DISPLACEMENT AND CHAMBER B HAVING BEEN DISPLACED AND READY FOR VENTING
ONE PRECHARGED BY STEP 1 OF VENT- C C C C C C 0
CHAMB B PRECHARGE
CHAMB A
TWO DISPLACING W/ STEP 2 OF VENT- 0 C C C 0 C C
POWER GAS GAS LIFT ASSIST
OR iNTERSTAGE
OF COMPRESSOR
THREE DISPLACING W/ STEP 3 OF VENT- 0 C C 0 C C C
POWER GAS VENT REMAINING
GAS TO ANNULUS
AND FILL CHAMB
W/ LIQUID
FOUR STEP I OF VENT- PRECHARGED BY C C C C C C 0
PRECHARGE CHAMB A
CHAMB B
FIVE STEP 2 OF VENT- DISPLACING W/ C 0 C C C 0 C
GAS LIFT ASSIST POWER GAS
OR INTERSTAGE
OF COMPRESSOR
SIX STEP 3 OF VENT- DISPLACING W/ C C 0 C C 0 C
VENT REMAINING POWER GAS
GAS TO ANNULUS
AND FILL CHAMB
W/ LIQUID
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As stated herein previously, the present invention achieves enormous energy
and economic
efficiencies by reducing the power requirements of the compressor. By
utilizing the high pressure
gas already introduced into the chambers, the horse power requirements of the
compressor are
greatly reduced. By introducing the high pressure gas into the third stage and
the lower pressure
gas into the first stage, the compressor has to work less to produce the high
pressure (greater than
5,000 p.s.i.) required for the evacuation of the respective chambers of
liquid. Additionally, since
the same gas is used that was introduced into the respective chambers for the
evacuation of the
liquid therefrom, the gases used for the operation of the present invention
are effectively conserved
and reused. This is particularly important if special gases are used for the
operation of the present
invention. For example, in many well operations, inert gases are used so as to
avoid corrosion of
the downhole equipment. These inert gases can be expensive to use. If such
expensive gases are
used, then the operation of the present invention can effectively conserve
such gases and reduce
costs associated with the provision of such gases.
The artificial lift system of the present invention is particularly useful for
restoring
production in depleted high condensate yield sour gas wells. In particular,
this system can be
applied to Smackover wells. The present invention achieves flowing bottom hole
pressures of
approximately 600 p.s.i. at 13,000 feet with flowing wellhead pressures of 300
p.s.i. The
configuration of the present invention employs an apparatus that can withstand
bottomhole
temperatures of greater than 300 F. The present system can handle produced
gas volumes of 3,000
MCFD. The present invention can achieve the production of liquid volumes
exceeding 500 barrels
per day. The present invention is suitable for operating in a very "gassy"
high API oil gravity
environment. Since the wells in which the present invention are intended to be
used for producing
in sour gas environments, the present invention minimizes the downhole parts.
As a result, the
present invention avoids the destructive effects of the corrosive environment
into which it is placed.
The downhole moving parts are wireline retrievable. The present invention can
work with saturated
brines having greater than 200,000 parts per million chlorides. The present
invention is compatible
with conventionally-sized production casing. Despite the fact the present
invention can be used at
very deep volumes, the present invention is cost competitive with other forms
of lift. It is possible
that the present invention can be utilized in depths of up to 25,000 feet and
can lift higher volumes
of up to 2,000 barrels per day. Unlike intermittent systems, the present
invention pushes an entire
line of liquid through the liquid string. As such, the transit time of
individual "slugs" of liquid is
avoided. The liquid string continuously allows the outflow of liquid
therefrom. The ability to
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control and utilize high gas pressures allows for the necessary "brute" force
so as to deliver the
continuous string of liquid from the liquid string.
The foregoing disclosure and description of the invention is illustrative and
explanatory
thereof. Various changes in the details of the illustrated construction or in
the steps of the described
method can be made within the scope of the appended claims without departing
from the true spirit
of the invention. The present invention should only be limited by the
following claims and their
legal equivalents.
