U.S. patent number 3,894,583 [Application Number 05/496,173] was granted by the patent office on 1975-07-15 for artificial lift for oil wells.
Invention is credited to Thomas H. Morgan.
United States Patent |
3,894,583 |
Morgan |
July 15, 1975 |
Artificial lift for oil wells
Abstract
An apparatus for retrieving oil from a producing zone after the
bottom hole pressure has decreased to such an extent that
artificial lift is required for production. An accumulator is
provided by casing sealed off with a packer, or an accumulation
chamber located in the area of the casing where oil accumulates.
The uppermost portion of the accumulator is vented to atmosphere to
allow oil flow therein. A floating piston-type device may be
located immediately above the accumulator with a bypass from the
accumulator to the top of the floating piston. Pressure is
subsequently applied through the vent line to the accumulator to
force oil from the accumulator through a stinger tube above the
floating piston and subsequently raise the oil and floating piston
to the surface. Without the piston, a stinger tube and standing
valve may be used to accumulate oil in the production tubing. The
vent line may be located inside the production line with the upper
casing being used as a pressure storage tank.
Inventors: |
Morgan; Thomas H. (San Antonio,
TX) |
Family
ID: |
23971559 |
Appl.
No.: |
05/496,173 |
Filed: |
August 9, 1974 |
Current U.S.
Class: |
166/68; 166/106;
417/128; 417/118; 417/138 |
Current CPC
Class: |
E21B
43/121 (20130101); F04F 1/06 (20130101) |
Current International
Class: |
F04F
1/06 (20060101); E21B 43/12 (20060101); F04F
1/00 (20060101); F04F 001/06 (); F04F 003/00 ();
E31B 033/03 (); E21B 043/00 () |
Field of
Search: |
;166/67,68,106
;417/118,120,145,143,128,138 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Husar; C. J.
Assistant Examiner: Gluck; Richard E.
Attorney, Agent or Firm: Cox, Smith, Smith, Hale &
Guenther Incorporated
Claims
What is claimed is:
1. An artificial lift apparatus for a liquid producing well having
a well head and a well casing therein, said apparatus
comprising:
production tubing extending from the well head into the casing to a
level below which the liquid from a liquid producing zone will fill
through perforations in the casing;
accumulator means in the bottom of the well casing for collecting
liquid in the well;
gas tubing means extending from the well head into the accumulator
means for communication therewith from the well head;
first check valve means for only allowing flow of liquid into said
accumulator means;
standing valve means at essentially the bottom of said production
tubing to allow flow of said fluid only into said production
tubing, said bottom of said production tubing being near the bottom
of said accumulator means;
means for receiving and handling said liquid at said well head;
and
control valve for alternately venting and pressurizing said
accumulator means via said gas tubing means, liquid being allowed
to collect in said accumulator means via said first check valve
means during venting, thereafter in response to said pressurizing,
said liquid is moved through standing valve means into said
production tubing and raised to the well head;
plate means for sealing said well casing at the well head;
first packer means for sealing said well casing to said production
tubing above said liquid producing zone, annulus between said plate
means and said first packer means being used to store pressurized
gas for said pressurizing of said accumulator;
a source of compressed air for pressurizing said annulus, said
control valve alternately connecting said gas tubing to said
accumulator means.
2. The artificial lift apparatus as recited in claim 1 wherein said
gas tubing means is inside said production tubing, crossover means
inside said production tubing for separately connecting said gas
tubing means to said accumulator and said production tubing to said
standing valve means.
3. The artificial lift apparatus as recited in claim 2 further
includes a second packer means below said liquid producing zone,
said first check valve means located on said production tubing
between said first and second packer means to allow the liquid to
flow below said second packer means, the area inside said casing
below said second packer means forming said accumulator means.
4. The artificial lift apparatus as recited in claim 3 wherein the
lower part of said production tubing which contains said standing
valve means further includes a stinger tube means which extends to
near the bottom of the liquid producing well.
Description
BACKGROUND OF THE INVENTION
This invention relates to oil recovery devices and, more
specifically, to an artificial lift for recovering oil from wells
that do not have sufficient bottom hole pressure to raise the oil
to the surface. The apparatus includes an accumulator to receive
the oil in the casing and a vent line to the surface which may
subsequently be pressurized to raise the oil contained in the
accumulator into the production tubing and, subsequently, to the
well head. The upper casing may be pressurized for gas lift of a
piston type device (or plunger), or used as a pressure storage
tank.
DESCRIPTION OF THE PRIOR ART
This invention is an improvement over U.S. Pat. application Ser.
No. 476,212 filed on June 4, 1974 and having the same inventor as
the present application.
There are several stages in the productive life of an oil well that
should be reviewed before going into the details of the present
invention. When a hydrocarbon producing well (oil well) is drilled,
the initial stage of production normally does not require any type
of lift mechanism to raise the oil from the producing formation to
the well head. The pressure on the oil itself is normally
sufficient to raise the petroleum (gas and oil) to the well head.
As oil is produced from the oil reservoir, the bottom hole pressure
will continue to drop until it reaches a point where the bottom
hole pressure is no longer sufficient to raise the column of oil to
the well head.
Once the bottom hole pressure has reduced to such an extent that it
will no longer raise the column of oil to the well head, steps can
be taken to reduce the weight of the column. A column of fluid from
the oil reservoir to the well head that does not contain gas weighs
more than a column that does contain gas. Therefore, a system
called gas lift and commonly used by the petroleum industry is to
bubble gas up through the column of oil thereby reducing the weight
of the column and causing the oil from the well to continue to
flow. Now the bottom hole pressure is sufficient to raise the
lightened column to the well head for a normal production flow.
This continues until the bottom hole pressure is again reduced to a
greater degree so that it is no longer sufficient to raise the
lightened column to the surface of the well.
The next stage in the productive life of an oil well under present
day operating conditions would be to allow the oil to accumulate in
the tubing and then to pressurize the casing. By having a gas lift
valve below the oil accumulated in the tubing, a blob of oil could
be raised to the surface. Thereafter, the pressure on the casing
would be relieved and oil would be allowed to accumulate again in
the tubing. This process is repeated again and again by allowing
oil to accumulate in the tubing, pressurizing the casing and
raising the blob of oil to the well head and relieving the pressure
to allow oil to accumulate again in the tubing. This process has
been aided somewhat by the use of swabs or subsurface plungers
(commonly called free floating pistons) with the swabs or plungers
allowing the oil to accumulate above their location in the
production tubing. Thereafter, further pressure increases in the
casing would raise both the oil and the swab or plunger to the
surface. Subsequently, the swab or plunger would be allowed to fall
back to its original position in the tubing and the cycle
repeated.
Because the casing, which is alternately pressurized and
depressurized, can only stand a certain amount of pressure, even
the type of gas lift just described has limited application. At
this stage of the productive life of the well, some type of
subsurface pump is needed to raise oil to the surface of the well.
Bottom hole pumps are very expensive, wear out and must be replaced
periodically. It becomes a matter of economics as to when the
bottom hole pressure is no longer sufficient to discharge enough
oil from the well to justify the cost of maintaining the costly
well equipment. At this point in time, the well is usually
abandoned unless other drastic steps such as flooding the
production zone are used. At this particular point the bottom hole
pressure has dropped to substantially zero.
Some production has occurred in old petroleum fields by drilling
holes below the productive zone. Actions such as latent water
drives, formation compression, gravity and many other contributing
factors may cause oil to gradually fill the holes drilled below the
productive zone. However, to remove the oil that has accumulated in
the hole drilled below the productive zone (commonly called sump
bores) is very costly, again requiring some type of subsurface pump
to raise the oil to the surface of the well. Such production is
normally economically unfeasible.
It should be noted in the previously described gas lift systems
that a gas source may be necessary. Because all the gas cannot be
recovered, gas lift systems are costly to run because the gas lost
is the same as lost income, or operating costs. Atmosphere could
not be used because mixing of atmosphere and oil will cause an
emulsion that is very detrimental to the oil produced.
SUMMARY OF THE INVENTION
The present invention is directed towards an economical means and
apparatus for continuing production of an oil well after it becomes
economically unfeasible using normal production techniques. An
accumulator is positioned in the oil that naturally drains into the
oil well. A vent line allows the accumulator to be at the same
pressure as atmosphere so that the oil will fill the accumulator.
Thereafter, the accumulator is pressurized through the vent line,
forcing the oil through a standing valve and stinger tube into the
production tubing. The vent line is located inside the production
tubing with a crossover device being provided above the
accumulator. Packers seal off the upper casing which can be used as
a storage tank. Packers also may seal off a sump area of the lower
casing to be used as the accumulation chamber.
In the embodiment using a floating piston or swab, a bypass line
moves the oil above the free floating piston or swab. By using a
crossover type device and packer, the upper casing may be
pressurized. As the pressure of the column of oil increases, a
differential pressure valve will operate allowing the pressurized
air in the upper casing to rapidly move the piston to the well
head. The oil accumulated above the piston will also rise to the
surface of the well. Once the piston has reached the top of the
well and pressure in the production tubing is vented, the piston is
allowed to fall back into its position above the accumulator. As
oil again collects in the accumulator, the previously mentioned
cycle is repeated.
A ball float valve in the air line tells an electronic control
circuit through an associated pressure switch when the accumulator
has been filled; therefore, it is time to pressurize the
accumulator and raise the oil to the surface. An appropriate clock
mechanism is used to time the cycle to control the compressed air
in and out of the accumulator.
In another embodiment, the stinger tube simply feeds through a
crossover seal area above the accumulator into the accumulator. The
accumulator is a lower sump area sealed off by packers. Upon
pressurizing the accumulator, oil moves through the standing valve,
stinger tube and crossover into the production tubing. Pressure is
then relieved and oil again collects in the accumulator with the
standing valve preventing the previous collected oil from feeding
back from the production tubing into the accumulator. By
alternately venting and pressurizing the accumulator, the oil is
moved up the production tubing to the well head. Once the oil has
been collected in the accumulator, it is never lost, and once the
oil enters the production tubing, it never reenters the
accumulator. The upper casing, if strong enough, may be used as an
air storage tank.
Therefore, it is an object of the present invention to provide an
apparatus for gathering oil from a well once the well has stopped
flowing due to a decrease in pressure of the reservoir.
It is a further object of the present invention to provide
artificial lift for an oil well that utilizes the minimum of
equipment so that is is economically feasible to continue
production from an oil well in ranges of approximately one barrel
per day.
It is still another object of the present invention to position an
accumulator in oil that would naturally accumulate in the bottom of
the well, vent the top of the accumulator to the atmosphere to
allow oil to flow through a check valve into the accumulator.
Subsequently, the accumulator is pressurized, thereby forcing oil
up through a stinger tube and bypass tube to a position above a
free floating piston or swab. A differential gas lift valve will
raise the free floating piston or swab with the oil contained
thereabove to the well head.
It is yet another object of the present invention to use a ball
float valve in the vent line in combination with a pressure switch
and choke located at the surface to give a signal indication when
the accumulator is full of oil. The signal is then used to trigger
control circuitry that would be used to pressurize the
accumulator.
It is still another object of the present invention to use a
differential gas lift valve underneath the free floating piston or
swab so that the pressure differential between the column of oil
above the piston and in the upper casing (blocked off from the
producing zone by a packer) reaches a given point, the differential
gas lift valve will operate and the free floating piston or swab
will begin to rise to the surface.
It is yet another object of the present invention to provide a
retrievable apparatus to allow direct access to the accumulator and
to the bottom of the well.
It is yet another object of the present invention to provide a
system that can be used in the production of an oil field wherein
each of the wells in the oil field have a low volume output and
require some type of artificial lift.
Yet another object of the present invention is to provide an
accumulator located in the oil that collects in the casing, the
accumulator being alternately vented to the atmosphere to collect
oil and pressurized to force the oil through a standing valve in a
stinger tube into the production tubing, the oil column in the
production tubing continually increasing until it reaches the well
head and flows with each cycle.
Even another object of the present invention is to provide an
artificial lift mechanism wherein a packer is contained between the
casing and the production tubing so that the upper portion of the
casing may be used as an air storage tank. A crossover type of
device is located near the packer and immediately above the stinger
tube so that only one tubing extends through the packer with the
other tubing being contained therein. An accumulator chamber may be
formed below the producing zone by having another packer located
below the oil producing zone with a standing valve allowing the oil
to flow into the lower region. A stinger tube would then extend
into the lower region which acts as an accumulator so that upon
pressurization the oil is forced up through the stinger tube and
the crossover device, and the oil may be subsequently raised to the
surface of the well.
Another object of the present invention is to use a differential
pressure valve in conjunction with the crossover device so that
when the pressure differential between the column of oil above the
piston and the pressure in the casing decreases below a given point
the differential pressure valve will operate thereby forcing the
plunger to the surface of the well.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1a is an elevated sectional view of the well head portion of
the artificial lift apparatus of the present invention and the
associated control mechanisms.
FIG. 1b is an elevated sectional view of the down-in-the-hole
portion of the artificial lift apparatus of the present
invention.
FIG. 2 is an elevated sectional view of an alternative embodiment
of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIGS. 1a and 1b in combination, there is shown a
hydrocarbon producing well represented generally by the reference
numeral 10. Because the present invention is directed towards
hydrocarbon producing wells that produce oil, it will hereinafter
be referred to as oil well 10. The oil well 10 has the normal
casing 12 that extends into the earth formation 14 and is held in
place by cement 16 as is the case in most oil wells. The casing 12
extends down into the oil producing zone 18. Inside the casing 12 a
production tubing 20 also extends down to the oil producing zone in
a manner common in the oil producing industry.
The oil well 10 is the type wherein the well head is sealed by
means of plate 22 extending around the production tubing 20 to the
casing 12. Located in the earth formation 14 just above the oil
producing zone 18 is a packer 24 that again seals the production
tubing 20 to the casing 12. Therefore, the space between production
tubing 20 and casing 12 from the plate 22 to the packer 24 may be
used as a pressure tank and is represented generally by the
reference numeral 26. A vent/pressure line 28 extends through the
plate 22 and seals therewith. The vent/pressure line 28 also
extends down inside the oil well 10 to a point just above packer 24
where the vent/compressor line 28 is connected to the production
tubing 20 through opening 30.
In the lower portion of the production tubing 20 immediately above
packer 24 is located a plunger 32 that is free floating inside of
the production tubing 20. The plunger 32 may be a swab type or a
free floating piston commonly referred to as the McMurray piston.
The plunger 32 will allow a small amount of flow therethrough, but
stop all flow therethrough upon sensing a large pressure
differential across plunger 32. Immediately below the plunger 32 is
a spring 34 to absorb the shock of the plunger 32 as it falls to
its lowermost position, such position being shown in FIG. 1b.
Immediately below the spring 34 is located a hook 36 that may be
used to retrieve apparatus contained in the production tubing 20 as
will be subsequently described. The hook 36 is attached to housing
38 having slots 40 contained therein for communication with the
space in the production tubing 20 immediately below plunger 32.
Attached to housing 38 below slots 40 are hold downs 42 and 44 that
rest against seating nipples of the production tubing 20. The
seating nipples of the production tubing 20 are not illustrated due
to close tolerances, but are commonly used in the oil producing
industry. Inside of the hold downs 42 and 44, which form a good
seal with the production tubing 20, is located a differential
pressure valve 46. The upper portion of the differential pressure
valve 46 has a bellows 48 that is in communication with chamber 50
located inside housing 38 by means of hole 52. The valve element 54
normally rests against seat 56. The valve element 54 and seat 56
are contained inside of housing 58 with chamber 60 being in
communication with annulus 62 by means of cross bore 64. Annulus 62
is in turn in fluid communication with pressure tank 26 by means of
holes 66. Hence the pressure developed across differential pressure
valve 46 is the difference between the pressure immediately below
the plunger 32 and the pressure inside of casing 12 represented by
pressure tank 26. As this differential pressure decreases below a
predetermined amount, the differential pressure valve 46 will open
as will be subsequently described.
Immediately below the differential pressure valve 46 and housing 58
are located hold downs 68 and 70 that again mate with seating
nipples of the production tubing 20. Inside of the hold downs 68
and 70 is located a cap 72 of housing 58 that seals the lowermost
portion of chamber 60 so that pressure inside of the production
tubing above hold downs 68 and 70 is not reflected below hold downs
68 and 70. Immediately below hold down 70 is a housing 74 having
slots 76 cut therein so that fluid communications can be
transmitted through vent/pressure line 28, opening 30 into chamber
78.
Immediately below chamber 78 is located a float valve 80 which
comprises a ball float 82, seat 84 and chamber 86. Chamber 86 is
formed by hold downs 88 and 90 that rest against appropriate
seating nipples in the production tubing 20. Chamber 86 is always
in communication with crossover line 92 due to the slots 94 cut in
flange seat 96. The crossover line 92 extends through chamber 98
that has slots 100 cut therein for fluid communication with annulus
102. From annulus 102 a bypass 104 communicates through openings
106 and 108 so that oil contained in chamber 98 may be moved around
plunger 32 and other apparatus contained in production tubing 20
via bypass tubing 104 and back into the upper portion of production
tubing 20 as will be described in more detail subsequently.
Crossover 92 communicates directly with production tubing 20 and
the annulus 110 formed between the production tubing 20 and the
stinger tube 112. Chamber 98 communicates with stinger tube 112 via
tubing 114 which extends through hold downs 116 and 118 that rest
on seating nipples of the production tubing 20. The crossover line
92 and the tubing 114 both extend through the hold downs 116 and
118 to form the crossover portion of the present invention
represented generally by the reference numeral 120. The reason for
having the crossover portion 120 is because of the packer 24 that
isolates the upper internal portion of casing 12 from the lower
internal portion so that the upper portion may be pressurized
without having any effect on the lower portion that is located in
the oil producing zone 18.
The lower portion of the casing 12 has perforations 122 to allow
oil from the oil producing zone 18 to flow into the lower part of
casing 12. Attached to the bottom of production tubing 12 and in
the oil producing zone 18 is located an accumulator 124 that
extends some distance along the lower portion of the casing 12. The
length of the accumulator 124 could be as much as 100 feet or even
more. The stinger tube 112 extends to almost the bottom of
accumulator 124 and has a check valve 126 located therein
represented generally by a ball 128 and seat 130. In the bottom of
the accumulator 124 is a retrievable standing valve 132 having a
fishing neck 134, housing 136 with slots 138 cut therein and ball
138 with the mating seat 140. Standing Valve 132 allows flow upward
in a manner very similar to a check valve, but not vice-versa. The
entire retrievable standing valve 132 is maintained in position by
hold downs 142 and 144 with corresponding seating nipples for lower
extension 146 of accumulator 124, the lower extension being of
approximately the same radius as the production tubing 20 or less.
Upon attaching a line to the fishing neck 134 the entire apparatus
contained in lower extension 146 may be retrieved to the surface of
the oil well 10. Also, immediately above the accumulator 124 and
directly below the packer 24 is located a gas vent valve 148 which
allows the flow of gas inside of the casing 12 into the production
tubing 20 by lifting the ball 150 off of seat 152. The gas vent
valve 144 allows for additional venting of gas from the oil
producing zone 18 so that the oil and gas may be more readily
separated before entry into the accumulator 124.
Referring back to FIG. 1a, the upper production casing 154 extends
above plate 122 with a pneumatic bellows 156 being located at the
top thereof. The pneumatic bellows 156 may be pushed upward and air
forced out through hole 158 by the plunger 32 as will be
subsequently described. Simultaneously, a sliding valve 160 will be
moved upward, thereby establishing communications between tubing
162, hole 164 and the internal portion of production tubing 20.
Also, a tubing 166 which has a check valve 168 located therein
receives oil from the production tubing 20 and delivers it to the
oil tank as will be subsequently described.
The vent/compressor line 28 is connected via a three-way solenoid
valve 170 that is operated by means of winding 172 and core 174.
The three-way valve 170 has a lever arm 176 that is pivotally
connected at pivot point 177. When the winding coil 172 is not
energized, the three-way valve 170 will be in the position as shown
with ball 178 resting against seat 180. When the winding coil 172
is energized, ball 178 will move away from seat 180 and ball 182
will seal against seat 184.
In the embodiment shown in FIGS. 1a and 1b vent/compressor line 28
is in communication through three-way valve 170, conduit 186
through choke 188 to atmosphere. A pop-off valve 190, common in the
petroleum producing industry, is also connected to conduit 186 to
relieve pressure above a predetermined point in addition to the
venting through choke 188.
The casing 12 is connected to a source of pressurized air via
conduit 192 which has a branch conduit 194 that extends to the
three-way valve 170 and ball 178 and seat 180. The source of
pressurized air would normally be a compressor with the casing 12
being the storage tank 26 to provide a large volume of compressed
air.
Located in conduit 186 is a pressure switch 196 that is connected
to a source of power that may be used to operate the three-way
valve 170. The source of power is connected through pressure switch
196 to a clock mechanism 198 and timer 200 to a pressure switch 202
that is responsive to pressure in conduit 192. If the contacts in
pressure switch 196 that are responsive to pressure in conduit 186
are closed, and the contacts in pressure switch 202 are closed, the
winding coil 172 of three-way valve 170 will be energized for a
predetermined period of time as controlled by timer 200.
METHOD OF OPERATION
During the normal operation of the present invention, the storage
tank 26 inside of casing 12 will be pressurized by compressed air
from a compressor through conduit 192 until pressurized to a
predetermined point. During initial pressurization vent/pressure
line 28 and production tubing 20 must be blocked at the well head.
Once the casing 12 is pressurized to a predetermined point, the
blocking of vent/pressure line 28 and production tubing 20 is
removed to practice the present invention. Referring now to FIGS.
1a and 1b in combination, the plunger 32 is located in the position
as shown and oil from oil producing zone 18 flows through
perforations 122 into the casing 12. The oil in the casing 12 then
flows up through standing valve 132 into accumulator 124. Excess
gas pressure may enter either through standing valve 132 or gas
vent valve 148 into accumulator 124. The gas in accumulator 124 is
vented through vent/pressure line 28 via crossover line 92 and
float valve 80. Since the vent/pressure line 28 is connected at the
well head through three-way valve 170 (as shown) to conduit 186 and
choke 188 to atmosphere, the pressure inside of the accumulator is
only slightly higher than atmospheric pressure with the difference
being controlled by the choke 188. Once the oil from the oil
producing zone 18 enters the casing 12 and the accumulator 124
through standing valve 132, it is trapped. As the oil continues to
collect in accumulator 124, it will fill the accumulator 124 and
begin to fill production tubing 24 up to float valve 80. As the oil
accumulates in float valve 80, the ball 82 will come to rest
against seat 84, thereby preventing a further venting through
vent/pressure line 28, three-way valve 170 and choke 188 to
atmosphere. Once the ball 82 comes to rest against the seat 84, the
small remaining pressure in vent-pressure line 28 and conduit 186
will be vented through choke 188 to atmosphere, thereby causing
pressure switch 196 to close. Pressure switch 196 is set to close
when the small amount of pressure contained in conduit 186 is lost,
which occurs when float valve 80 closes, thereby indicating the
accumulator 124 is full of oil.
Upon the closing of the pressure switch 196 and pressure switch
202, as was previously closed when casing 12 was pressurized to
fill storage tank 26, power is fed through the clock 198 and timer
200 to energize the three-way valve 170. Upon energization of the
three-way valve 170 the core 174 inside of winding 172 moves
downward thereby raising lever 176 to seat ball 182 against seat
184 and unseat ball 178 from seat 180. Now the vent/pressure line
28 is connected to the pressure tank 26. The pressure from pressure
tank 26 flows directly through conduit 192 and branch conduit 194,
through the three-way valve 170 into the vent/pressure line 28. The
pressurized air pushes against the oil inside of float valve 80 and
forces it back down through crossover 92 into accumulator 124. At
the same time the oil in accumulator 124 is being forced up through
check valve 126 and into stinger tube 112. From the stinger tube
112 the oil is being forced upward through chamber 98, bypass
tubing 104 and back into production tubing 20 at a location above
plunger 32. The pressurized air through vent/pressure line 28
continues to force the oil up through the stinger tube 112 in the
manner just previously described until the timer 200 has expired,
thereby changing the position of three-way valve 170.
As previously described, any pressure inside of pressure tank 26 is
felt immediately below differential pressure valve 46 by means of
cross bore 64 and holes 66. The plunger 32, which may be the
McMurray type, allows the oil contained in production tubing 20 to
flow through the plunger 32 at a very slow rate. Therefore, the
weight of the column of oil generates a pressure which will be
reflected below plunger 32 through chamber 50 and hole 52 to
bellows 48 of differential valve 46. Once the weight of the column
of oil above plunger 32 reaches a predetermined amount so that a
given pressure differential exists across differential pressure
valve 46, the valve 46 will be open for any pressure differential
below that predetermined pressure differential. Upon opening the
pressure differential valve 46, pressurized air inside of casing 12
will force the plunger 32 and the column of oil to the surface of
the oil well 10. The valves inside of plunger 32 close when hit by
a large amount of pressurized air, thereby forcing the plunger 32
and the column of oil to the well head without the oil flowing down
through the plunger 32. At the surface of the oil well 10 the oil
immediately above the plunger 32 will flow through check valve 168
and tubing 166 into the oil storage tank. The plunger 32, however,
will continue beyond tubing 66 of the upper production casing 154
to hit pneumatic bellows 156 thereby opening sliding valve 160. The
sliding valve 160 would then vent any air below the plunger 32 to a
separator through tubing 162. The plunger 32 will be held into
position against the pneumatic bellows 156 until essentially all
the pressurized air has been removed from production tubing 20.
It is important that the timer 200 be set so that just enough time
will be allowed to raise the column of oil and the plunger to the
well head upon deenergizing the three-way valve 170. Once the
three-way valve 170 is deenergized, it will return to the position
shown in FIG. 1a thereby terminating the connection between the
vent/pressure line 28 and storage tank 26, and reestablishing the
communication between vent/pressure line 28 and atmosphere. After
the pressure in production tubing 20 has been relieved, the plunger
32 will fall back to its position shown in FIG. 1b and the cycle
will begin to repeat itself by oil collecting in the accumulator
124.
ALTERNATIVE EMBODIMENT
Referring now to FIG. 2 of the drawings, there is shown an
alternative embodiment of the present invention with the control
portion not being shown in detail because it is substantially
identical to the controls shown and described in conjunction with
FIG. 1a. Numbers that were used in conjunction with the previous
description of FIGS. 1a and 1b will be used in FIG. 2 where
appropriate. Again the oil well 10 has casing 12 that is located in
the earth formation 14 and held in place by means of cement 16 and
extends all the way to the oil producing zone 18. Inside of the
casing 12 is located production tubing 20 with the area between the
production tubing 20 and the casing 12, and above packer 24, being
pressure storage tank 26. Again the top of the oil well 12 is
sealed by means of a plate 22 so that only the production tubing 20
extends therethrough. Internal to the production tubing 20 is
located vent/pressure line 28 that was contained on the outside
thereof in FIGS. 1a and 1b. The vent/pressure line again connects
to three-way valve 170 in the manner previously described in
conjunction with FIGS. 1a and 1b.
The vent/pressure line 28 extends down through the production
tubing 20 to the float valve 80 which has a ball float 82 contained
inside of housing 204 and a seat 84 contained at the top thereof.
The lower portion of the housing 204 is connected to a crossover
line 92 by means of a flange seat 96 having slots 94 cut therein so
that chamber 86 will be in continual communication with crossover
line 92. Immediately below chamber 86 is a chamber 98 having slots
100 cut therein to allow communication with annulus 102. From
annulus 102 there is direct communication with the annular space
between production tubing 20 and the vent/pressure line 28.
The crossover line 92 extends through hold downs 116 and 118 that
rest against seating nipples of the production tubing 20. Also,
chamber 98 communicates through the hold downs 116 and 118 via
tubing 114. Immediately below the crossover portion 120 is located
the packer 24. The packer 24 should be located at or near the top
of the oil producing zone 18. Immediately below the packer 24 is a
standing valve 206 that is represented pictorially by ball 208 and
seat 210. The standing valve 206 allows communication from the oil
producing zone 18, annulus 212 into the production tubing 20. Near
the bottom of the oil producing zone 18 is located another packer
214 that seals off the lower portion 216 of the oil well 10. The
lower portion 216 can now serve as the accumulator that was
previously described in conjunction with FIG. 1b. Though the
production tubing 20 will probably extend to the bottom of the
lower portion 216 it contains perforations 218 to allow free flow
of oil through the production tubing 20. The casing 12 will extend
to the bottom of the oil well 10.
Also extending from the crossover portion 20 and through packers 24
and 214 is stinger tube 112. The stinger tube extends to
substantially the bottom of the accumulator formed by the lower
portion 216 and has a check valve 126 located therein that is
represented pictorially by ball 128 and seat 130.
METHOD OF OPERATION OF THE ALTERNATIVE EMBODIMENT
In the alternative embodiment again the casing 12 is pressurized to
provide pressure in the pressure storage tank 26 formed by the
upper portion of the casing 12. Again the accumulator represented
by lower portion 216 is vented to atmosphere via vent/pressure line
28 and crossover line 92 in a manner previously described in
conjunction with FIGS. 1a and 1b. Oil from the oil producing zone
18 flows through the perforations 122 into annulus 212. From
annulus 212 the oil flows through standing valve 206 into
production tubing 20 and down into the accumulator formed by the
lower portion 216 of the casing 12. Once the lower portion 216 is
filled with oil, the oil will begin to fill production tubing 20
until it reaches float valve 80 located immediately above packer
24. The ball float 82 will float on top of the surface of oil and
come to rest against seat 84, thereby terminating the venting
through vent/pressure line 28. In a manner previously described in
conjunction with FIGS. 1a and 1b, the three-way valve 70 will now
be energized thereby unseating ball valve 178 and seating ball
valve 182. Pressure from the pressure tank 26 now flows through the
vent/pressure line 80 to force the oil back down through crossover
line 92, production tubing 20 and up through stinger 112. In this
case the timer is set so that enough time is allowed to force
essentially all of the oil contained in lower portion 216 up into
stinger tube 112. Thereafter the three-way valve 170 is deenergized
and the pressure contained in the lower portion 216 is vented
through vent/pressure line 28 and oil is again allowed to
accumulate from oil producing zone 18. Notice that check valve 206
does not allow the pressurized air to be felt against the oil
producing zone 18. Once enough oil has again accumulated in the
lower portion 216 and production tubing 20 to shut the float valve
80 the cycle will be repeated. Again the oil will be forced up
through the stinger tube 112 in the manner previously described for
the earlier cycle. This process is repeated again and again until
the column of oil in the production tubing 20 will reach the
surface of the oil well 10. Thereafter, for each cycle of
operation, oil will flow through tubing 166 to the oil storage
tank. Once oil has been received in the stinger tube 112, it cannot
flow back into the lower portion 216 because of check valve
126.
As the oil well 10 is brought into production, the cycle of the
timer may have to be adjusted due to the increased weight of the
oil column contained in production tubing 20. As the weight of the
column of oil increases additional time will be necessary to insure
that essentially all of the oil contained in the lower portion 216
has been forced into the stinger tube 112.
* * * * *