Note: Descriptions are shown in the official language in which they were submitted.
CA 02478953 2004-08-24
Method And Pump Apparatus For Removing Liquids From Wells
BACKGROUND OF THE INVENTION
Field of the Invention
[001] The present invention relates generally to methods and systems for
lifting fluids from
a well. More particularly, relating to a method and apparatus for removing
formation
fluid, such as water from a low production gas well to reduce static pressure
within the
well created by the formation fluid, thereby increasing production of gas from
the well.
Discussion of the Prior Art
[002] Many gas wells experience decreased gas production over the service time
of the well,
and some eventually cease gas production completely. Factors causing this
problem
include declining reservoir pressure and gas velocities, aj:fld increased
liquid production.
The increased liquid production can results in a column of liquid to
accumulating at the
bottom of the well, preventing reservoir fluids (gas) from entering the
wellbore. This
accumulation of liquid is called "liquid loading of the well".
[003] There are many systems available to restore a well that is "liquid
loaded" back to flow
production, such as a siphon string (or velocity string), a plunger lift, a
pump jack, and a
submersible pump.
[004] A siphon string is essentially a small diameter tubing string that is
lowered into the
production string of a well. The siphon string provides a reduced cross-
sectional flow
area which increase the gas velocity in the tubing. The higher gas velocity at
the bottom
of tubing provides more transport energy to lift fluid up out of the well.
Liquid no longer
accumulates at the bottom of the well, and production is sustained. Siphon
strings are
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CA 02478953 2004-08-24
very difficult to size properly so that the gas velocity meets or exceeds a
minimum or
critical velocity to prevent the well from loading up. The process of
determining the
correct size of the tubing string is well described by Turner et al. in
"Analysis and
Prediction of Minimum Flow Rate for the Continuous Removal of Liquid from Gas
Wells"; J. Pet. Tech (Sept. 1969) 1475-1481.
[005] A plunger lift is an artificial-lift method principally used in gas
wells to "unload"
relatively small volumes of liquid. An automated system is employed to control
the well
on an intermittent flow regime. When the well is shut-in, a plunger is dropped
down the
production string and then when the control system opens the well for
production, the
plunger and a column of fluid are carried up the tubing string. A surface
receiving
mechanism detects the plunger when it arrives at the surface and, through the
control
system, prepares for the next cycle. One deficiency of a plunger lift system
in the amount
of time required for each cycle of the system. Typically gas wells are medium
to deep
wells and plunger must travel a great distance up and down the well to lift
fluid.
[006] A pumpjack is another artificial lift method and basically includes a
plunger pump
submerged into the well below the volume of water and is actuated by a rod
string that
extends to the surface, which is reciprocated by a prime mover at the surface.
A pump
jack is an old fashion system and is prone to wear resulting in down time
required to
make necessary repairs.
[007] The use of a submersible pump is yet an additional method of "unloading"
the well,
which involves placing the pump at the bottom hole and positively pumping the
fluid to
the surface of to "unload" the well. Submersible pumps are limited to the
depth of the
well and become less efficient in operation the deeper the well is.
Additionally, electrical
submersible pumps are typically used which requires the drop-in of an electric
control
line and electric power line.
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CA 02478953 2004-08-24
[008] While the above described systems operate as intended, there exists a
need for a more
efficient method and apparatus for "unloading" a well, as such the method and
apparatus
of the instant invention provides such a method and apparatus which is more
efficient,
less costly to operate, experiences less wear, and has a reduced cycle time.
SUMMARY OF THE INVENTION
[009] In accordance with the present invention, an apparatus and method for
efficiently
removing fluid from a well is provided. The apparatus is relatively
inexpensive to
manufacture as it incorporates readily available components and is inexpensive
to operate
due to a low electrical load requirement, which can be met by using solar
power systems
or by a small electric generator. The low power requirement make the instant
invention
very conducive for operation with wells that do not have access to wired
electrical power.
[0010] In one embodiment, the apparatus essentially includes a pump body
having an
exterior surface and an axial bore comprising a first charnber and a second
chamber
which are separated by a diametrically reduced section of the axial bore. The
pump body
further includes at least one gas vent which extends from the exterior surface
of the pump
body into the first chamber, a fluid inlet port extending from the exterior
into the second
chamber, and a fluid discharge port extending from the exterior surface and
into the
second chamber. A hydraulic head is attached to the pump body and a
displacement
plunger extends from the hydraulic head through the axial bore. A hydraulic
circuit is
attached to the hydraulic head and is operated to control reciprocation of the
displacement
plunger within the axial bore by the hydraulic head. A vent passage extends
through a
distal end of the displacement plunger for venting gas therethrough from the
second
chamber into the first chamber and then finally through the gas vent of the
pump body. A
fluid discharge conduit is connected to the fluid discharge port and includes
a first check
valve connected inline therewith allowing fluid to be discharge in only one
direction from
the second chamber out of the discharge port and into a lift tube, which is
connected to
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CA 02478953 2004-08-24
the fluid discharge conduit. A second check valve is connected to the fluid
inlet port for
allowing formation fluid to flow in one direction into the first chamber of
the pump body.
[0011] In a second embodiment, the apparatus essentially includes a pump body
having
an exterior surface and an axial bore. A fluid inlet port extends from the
exterior surface
of the pump body into the axial bore, a fluid discharge port extends from the
exterior
surface into the axial bore, and a vent port extends from the exterior surface
into said
axial bore. A hydraulic head is attached to the pump body and a displacement
plunger
extends from the hydraulic head through the axial bore. A hydraulic circuit
attached to
the hydraulic head and operated the same to reciprocate the displacement
plunger within
the axial bore. A fluid discharge conduit is connected to the fluid discharge
port and a
first check valve is connected inline therewith to allow fluid to flow in only
one direction
out of the fluid discharge port and into a lift tube connected the fluid
discharge conduit.
A second check valve connected to said fluid inlet port to allow formation
fluid to flow in.
one direction into the axial bore and a vent valve is attached to the vent
port for venting
gas therethrough and out of the axial bore.
[0012] There has thus been outlined, rather broadly, the more important
features of the
invention in order that the detailed description thereof that follows may be
better
understood and in order that the present contribution to the art may be better
appreciated.
[0013] Numerous objects, features and advantages of the present invention will
be readily
apparent to those of ordinary skill in the art upon a reading of the following
detailed
description of presently preferred, but nonetheless illustrative, embodiments
of the present
invention when taken in conjunction with the accompanying drawings. The
invention is
capable of other embodiments and of being practiced and. carried out in
various ways.
Also, it is to be understood that the phraseology and terminology employed
herein are for
the purpose of descriptions and should not be regarded as limitirig.
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CA 02478953 2004-08-24
[0014] As such, those skilled in the art will appreciate that the conception,
upon which
this disclosure is based, may readily be utilized as a basis for the designing
of other
structures, methods and systems for carrying out the several purposes of the
present
invention. It is important, therefore, that the claims be regarded as
including such
equivalent constructions insofar as they do not depart from the spirit and
scope of the
present invention.
[0015] For a better understanding of the invention, its operating advantages
and the
specific objects attained by its uses, reference should be had to the
accompanying
drawings and descriptive matter in which there is illustrated preferred
embodiments of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The invention will be better understood and objects other than those
set forth
above will become apparent when consideration is given to the following
detailed
description thereof. Such description makes reference to the annexed drawings
wherein:
[0017] Figure 1 is a diagrammatic view of the preferred embodiment of the
method and
apparatus for removing fluids from wells constructed in accordance with the
principles of
the present invention;
[0018] Figure 2a is a side elevation view of a first embodiment of a pump
apparatus of
the present invention shown in a first position;
[0019] Figure 2b is a side elevation view of the pump apparatus of Figure 2a
shown in a
second position;
CA 02478953 2004-08-24
[0020] Figure 3a is a side elevation view of a second exnbodiment of the pump
apparatus
of the present invention shown in a first position; and
[0021] Figure 3b is a side elevation view of the pump apparatus of Figure 3a
shown in a
second position.
[0022] The same reference numerals refer to the same parts throughout the
various
figures.
DETAILED DESCRIPTION OF THE PREFERRED ElVIBODIMENTS
[0023] Referring now to the drawings, and particularly to Figures 1-3, a
preferred
embodiment of the pump apparatus 10 is illustrated. The pumping apparatus 10
is
employed to lift formation fluid 12 from the well 14 to "unload" the well and
restore it
back to flow production. The formation fluid 12 can be water, oil or any other
liquid gas
mixture which is present downhole the well 14 to be pumped from one location
to
another. In addition, while the pump apparatus 10 is shown to be lifting the
formation
fluid 12 from a conventional gas well 14, the pump appaxatus 10 will work as
well in any
other environment where its particular features would be beneficial.
[0024] The pump apparatus 10 essentially includes a pump body 18, a hydraulic
head 20
connected to the pump body, a reciprocating displacement plunger 22 connected
to and
operated by the hydraulic head 20 to reciprocate within the pump body to draw-
in
formation fluid 12 and displace it from the pump body to the surface of the
well 14.
[0025] The hydraulic head 20 is connected to a hydraulic circuit 24 having a
prime mover
26 which is positioned at the surface of the well 14. The prime mover 26 can
be of any
know device for establishing pressure within the hydraulic lines of a
hydraulic system,
such as a pump. Due to the design of the pump apparatus 10, the power
requirements to
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CA 02478953 2007-12-21
operate the pump apparatus are very low and can be sttpPlied by one of a
numerous
sources, such as a small portable electric generator or preferable, a solar
energy
conversion system 15.
[00261 ReTezring now to Figure 2a, the construction of the pump apparatus 10
will be
described in more detail. The pump body 18 has an axial bore 28 defining a
first rliamber
30, a diametrically reduced section 32, and a second chamber 34. At least one
gas ve.nt
port 36 is forrned througb, the side wall 38 of the pwrnp body 18 and into the
first chamber
30. Preferably, the gas vent port 36 is formed through the side wall 38 normal
to the axial
bore 28. A fluid in-let port 40 is formed through the side wal138 of the pump
body 18
and into the second chamber 34. Preferably, the fluid in-let port 40 is formed
through the
side wall 38 normal to the axial bore 28. A t]uid discharge port 42 is also
formed through
the pump body 18 and into the second chamber 34. Preferably, the fluid
discharge port
42 is formed axially through an end 44 the pump body 18.
[0027] The hydraulic head 20 is attached to the pump body 18 opposite of end
44 and the
displacement plunger 22 extends from, the hydraulic head into the axial bore
28 through
the first chamber 30, the diametrically reduced section 32 and into the second
chaniber
34. The displacement plunger 22 seals the first chamber 30 from the second
chamber 34
when passed through the diacnetrically reduced section 32. A sea146 is
positioned
between the displacement plunger 22 and the diametrical.ly reduced section 32
to insure
the flrst chamber 30 and the second chamber 34 remained sealed from on
another.
Preferable the stroke of the displacement pluxager 22 is about equal to the
length of the
second chamber 34. The stroke ofthe displacement plunger 22 is such, when in a
fully
retracted position tbLe bottom end thereof is flush with the diametrically
reduced section
32 on the second chamber 34 side, as illustratW in Figure 2a. When, the
displace,nent
plunger 22 is in a fally extended position, the bottom eiid is in close
tolerance to the end
50 of the second chamber 34_
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CA 02478953 2007-12-21
[00281 Preferably, the diameter of the displacement plnnger 22 is less then
the diameter
o:f the axial bore 28 so that the displacernent plunger does not contact the
surface of the
axial bore to reduce wear and to eliminate the need to lubricate the
displacement plunger.
[0029] A vent passage 52 is formed through the bottom end of the displacement
plunger
22 such that fluid, gas or air is allowed to pass through the bottom end and
out of the gas
vent port 36 when the displacement plunger is in th.e fully retracted position
as shown in
Figuire 2a.
[0030] A fluid discharge conduit 54 is attached to the fluid discharge port 42
and includes
a first check valve 56 connected in-line therewith to allow formation fluid 12
displaced
from the pump body 18 by the displacement pump to only flow in one direction
through
the discharge conduit and to prevent backflow of the foxzzxation fluid into
the pump body,
which has already been displaced by the displacement plunger.
[0031] A li.ft tube 58 is provided and is in connected to the discharge
conduit 54 to carry
the formatyoii fluid 12 to the surface of the well 14.
[0032] A second check valve 60 is connected to the fluid in-let port 40and
allows
formation fluid only flow into the pump body 18 through the fluid in-let port.
[0033] Additionally, the pump apparatus 10 can include a casxng 62 enclosing
the pump
body 18, the hydraulic head 20, and any other element of the pump apparatus as
so
desired within an interior volume 64. Preferable, all of the elements are
enclosed by the
casing 62 and positioned within the interior volume thereof. The casing 62
including a
pair of fluid passages 66 which are formed through the sidewa1168 of the
casing placing
the interior voluzx.te 64 of the casing in fluid communication with the well
14. Most
preferably, the pair of fluid passages 66 are foimed tbsough the casing 62 at
opposite ends
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CA 02478953 2004-08-24
thereof.
[0034] When the casing 62 is included in the pump apparatus 10, the lift tube
58 is
connected to the exterior of the casing and is sealed from the interior volume
64 thereof,
with the fluid discharge conduit 54 connected to the lift tube and the
hydraulic control
lines 70 run down the lift tube and connect to the hydraulic head 20.
[0035] Referring now to Figures 2a and 2b, the purnp apparatus 10 is
preferably placed
downhole below or about the perforations 72 of the well 14 and into a column
of
formation fluid 12. The displacement plunger 22 is first fully retracted
establishing fluid
communication between the first chamber 30 and the second chamber 34 by the
vent
passage 52 formed into the displacement plunger. In this position, formation
fluid 12 is
hydrostatically forced by well pressure into the pump body 18 through the
fluid in-let port
40 and into the second chamber 34. If any gas is admixed with the formation
fluid 12 it
flows from the second chamber 34 through the vent passage 52 into the first
chamber 30
and then out of the gas vent port 36. The displacement plunger is held in the
retracted
position for a predetermined time that is sufficient for a desired volume of
formation fluid
12 to collect within the second chamber 34.
[0036] When the predetermined time as been met, the displacement plunger 22 is
operated by the hydraulic head 20 and is extended into the second chamber 34.
As the
displacement plunger 22 travels into the second chamber 34, the first chamber
30 and the
second chamber are fluidically disconnected and the formation fluid 12 present
within the
second chamber is displaced by the displacement plunger out of the fluid
discharge port
42, into the fluid discharge conduit 54, and then into the lift tube 58, where
it travels to
the surface of the well 14.
[0037] Once the displacemerit plunger 22 has completed the stroke, it is then
reset into
the retracted position and the cycle is reinitiated. The pump apparatus 10 is
operated in
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CA 02478953 2004-08-24
this manner until enough formation fluid 12 is lifted from the well to
"unload" the well
and reestablish gas production from the well.
[0038] Referring now to Figures 3a and 3b, a second embodiment of the pump
apparatus
is illustrated and will be described. In this embodiment, the pump apparatus
10 is of
the basic construction as the first embodiment and includes a pump body 18, a
hydraulic
head 20 connected to the pump body, and a reciprocating displacement plunger
connected
to and operated by the hydraulic head 20 to reciprocate within the pump body
to draw-in
formation fluid 12 and displace it from the pump body to the surface of the
well 14. The
main difference between the first and second embodiments is the first chamber
30, the
diametrically reduced section 32, and the second chamber 34 are eliminated in
the second
embodiment, and a vent valve is added to control the venting of formation
fluid 12 from
the pump body 18.
[0039] More particularly in the second embodiment, the pump body 18 has an
axial bore
28, a gas vent port 36 formed through the side wall 38 of pump body, a fluid
in-let port 40
formed through the side wall, and a fluid discharge port 42 formed through the
side wall.
Most preferably, the gas vent port 36 is formed through the side wall 38
normal to the
axial bore 28, the fluid in-let port 40 is formed through the side wall 38
normal to the
axial bore 28, and the fluid discharge port 42 is formed axially through an
end 44 of the
pump body 18.
[0040] The hydraulic head 20 is attached to the pump body 18 opposite of end
44 and the
displacement plunger 22 extends from the hydraulic head into the axial bore
28.
Preferable the stroke of the displacement plunger 22 is about equal to the
length of the
axial bore 28. Most preferably, the diameter of the displacement plunger 22 is
less then
the diameter of the axial bore 28 so that the displacement plunger does not
contact the
surface of the axial bore to reduce wear and to eliminate the need to
lubricate the
displacement plunger.
CA 02478953 2004-08-24
[0041] A fluid discharge conduit 54 is attached to the fluid discharge port
42and includes
a first check valve 56 connected in-line therewith to allow formation fluid 12
displaced
from the pump body 18 by the displacement pump to only flow in one direction
through
the discharge conduit and to prevent backflow of the formation fluid into the
pump body.
[0042] A lift tube 58 is provided and is in connected to the discharge conduit
54 to carry
the formation fluid 12 to the surface of the well 14.
[0043] A second check valve 60 is connected to the fluid in-let port 40 and
allows
formation fluid only flow into the pump body 18 througli the fluid in-let
port.
[0044] A vent valve 74 is attached to the gas vent port 36 and is operative to
control
venting of fluid from the gas vent. Preferably, the vent valve 74 is a
normally closed
valve and is operated to open based upon a predetermined pressure present
within the
hydraulic circuit 24.
[0045] As in the previous embodiment, the pump apparatus 10 can also
optionally
include a casing 62 enclosing the pump body 18, the hydraulic head 20, and any
other
element of the pump apparatus as so desired within an interior volume 64.
Preferable, all
of the elements are enclosed by the casing 62 and positioned within the
interior volume
thereof. The casing 62 including a pair of fluid passages 66 which are formed
through the
sidewal168 of the casing placing the interior volume 64 of the casing in fluid
communication with the well 14. Most preferably, the pair of fluid passages 66
are
formed through the casing 62 at opposite ends thereof.
[0046] When the casing 62 is included in the pump apparatus 10, the lift tube
58 is
connected to the exterior of the casing and is sealed from the interior volume
64 thereof,
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CA 02478953 2004-08-24
with the fluid discharge conduit 54 connected to the lift tube and the
hydraulic control
lines 70 run down the lift tube and connect to the hydraulic head 20.
[0047] In operation, the displacement plunger 22 is first set at a full
retracted position for
a predetermined time and formation fluid 12 is allowed to enter the pump body
through
the fluid in-let port 40. The hydraulic circuit 24 is pressurized to a
predetermined
pressure opening the gas vent port 36 to vent any gas admixed with the
formation fluid
drawn into the pump body.
[00481 When the predetermined time is met, the gas vent valve 74 is isolated
and closed,
and the displacement plunger 22 is operated by the hydraulic head 20 and is
extended into
the axial bore 28. As the displacement plunger is extended into the axial bore
28, the
formation fluid 12 is displaced by the displacement plunger out of the fluid
discharge port
42, into the fluid discharge conduit 54, and then into the lift tube 58, where
it travels to
the surface of the well 14.
[0049] Once the displacement plunger 22 has completed the stroke, it is then
reset into
the retracted position and the cycle is reinitiated. The pump apparatus 10 is
operated in
this manner until enough formation fluid 12 is lifted from the well to
"unload" the well
and reestablish gas completion from the well.
[0050] In either embodiment, the operation of the pump apparatus 10 can be a
manual
control through the incorporation of manually actuated valves in the hydraulic
circuit 24,
or preferably, a progralnmable logic controller 76 is used and is programmed
to control
the operation of the pump apparatus. It is believed that no further discussion
of the
manual or controller operation of the pump apparatus is rieeded as it is in
the knowledge
of one of ordinary skill to incorporate such control systems into a hydraulic
circuit to
operate a hydraulic plunger.
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CA 02478953 2004-08-24
[0051] A method of removing formation fluids from a well to "unload" the well
is also
provided. The method involves the steps of providing a hydraulically operated
fluid
displacement pump connected to a hydraulic circuit, positioning the fluid
displacement
pump downhole, operating the fluid displacement pump intermittently to vent
the pump
of gas, load the pump with formation fluid and to discharge the formation
fluid to the
surface of the well. The displacement pump comprising any one of the two above
described embodiments.
[0052] A number of embodiments of the present invention have been described.
Nevertheless, it will be understood that various modifications may be made
without
departing from the spirit and scope of the invention. Accordingly, other
embodiments are
within the scope of the followi.ng claims.
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