Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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GAS PUMPING UNIT FOR OIL WELLS
BACKGROUND OF THE INVENTION
1. Field of the Invention.
The present invention relates to the field of
machinery, arrangements and devices used in the oil industry,
and more particularly it refers to a gas extracting and
transferring unit for oil wells that allows reducing pressure
W in the well annulus depending on the well gas contribution,
thus increasing the production of fluid from it. It is
emphasized that, this gas pumping unit is completely
independent from the systems commonly used for oil extraction,
such as, for example, AIB (Independent Pumping Unit, for its
abbreviation in Spanish) rod pumps, PCP, electro-submersible
pumps, "PLUNGER LIFT" type pumps, etc., and in turn, it allows
programming the required pressure in the well.
2. Description of the Prior Art.
AIB rod pumps are well known in the oil industry, and
are known to allow carrying out mechanical extraction of crude
oil from oil wells. Rod pumps are commonly used in many
oilfields, and depending on the size of the pump, 5 to more
than 50 m3 of a mixture of crude oil and water can generally
be produced in 24 hours. The size of the pump is also
determined by the depth and weight of the crude oil to be
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extracted, wherein a deeper extraction requires more energy to
move greater lengths of fluid column. A connecting rod-crank
mechanism converts the motor rotary motion into a
reciprocating vertical movement that moves the pump rod, and
produces the typical pitch movement. Thus, the AIB rod pump
allows the extraction of crude oil from wells.
As mentioned above, crude oil is accompanied by water
and gas in the oilfield. However, the gas in the well can be a
major problem for oil extraction. This can occur due to
excessive gas pressure inside the well, more particularly in
the annulus space between the casing and the pipe. The
presence of excessive gas pressure significantly decreases oil
production. As a result of the above, some arrangements have
been developed that allow extracting the gas from the well
annulus to reduce pressure and allow the normal production of
crude oil. Currently, beam-rocker compressors are used in
mechanical pumping for the transfer of gas, which are mounted
and operated in conjunction with the AIB rod pumps, using a
large piston and the extraction of gas depending on the number
of strokes performed by the AIB.
However, although the use of beam-rocker compressors
has proved to be practical in the field of the art, they have
drawbacks that limit oil production. One of these drawbacks is
the dependence on the movement of the head of the AIB to carry
out the extraction of gas, so if compressor requires some type
of maintenance, first the AIB should be stopped to carry out
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said maintenance, which entails losses of time and production.
Also, although the gas pressure may vary in the well annulus,
conventional compressors constantly extract equal amounts of
gas in each stroke, so gas pressure inside the well can vary
significantly affecting positively or negatively the
production of oil.
By virtue of the above, it would be very convenient to
have a new arrangement, device, machinery or means that may
allow extraction of gas from the oil well without affecting
the conditions of production of crude oil, allowing in turn an
adequate extraction of gas according to pressures existing in
the well.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to
provide a pumping unit for oil wells that allows gas
extraction independently from the AIB rod pumps.
It is still another object of the present invention to
provide a pumping unit that allows maintaining a constant gas
pressure in the well, since it has a pressure switch, pressure
transmitter and frequency converter that controls the speed of
the piston as a function of the gas flow rate to be extracted.
It is also another object of the present invention to
provide a pumping unit that, owing to its structural
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configuration, has a longer useful life and efficiency of the
pumping unit due to minor maintenance and repairs
It is another object of the present invention to
provide a gas pumping unit for oil wells that make it possible
for pressure in the well to be programmable.
It is still another object of the present invention to
provide a gas pumping unit for oil wells comprising at least
one compressor cylinder having at least one gas inlet in
connection with the well, at least one gas outlet, one
pivoting lower end and a double-acting piston whose drive
shaft is connected to a drive motor, which can be an electric,
hydraulic or combustion motor, said drive motor being
connected to a pressure transmitter operatively connected to a
pressure switch which is in turn operatively connected to the
well.
BRIEF DESCRIPTION OF THE DRAWINGS
For greater clarity and understanding of the object of
the present invention, it has been illustrated in several
figures, in which the invention has been represented in one of
the preferred embodiments, all by way of example, wherein:
Figure 1 shows an exemplary schematic view of the gas
pumping unit for oil wells according to the present invention,
wherein it has been illustrated, merely by way of example, in
connection with the corresponding parts installed in the well.
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Figure 2 shows a perspective view of the gas pumping
unit for oil wells according to the present invention; and
Figures 3 and 4 show a sectional view of the gas
pumping unit according to the present invention, wherein the
direction of advancement of the piston can be observed
allowing gas entry and simultaneous compression/discharge
thereof.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the figures, it is seen that the
invention consists of a new gas pumping unit for oil wells
which is an unit independent from the AIB rod pumps that
allows regulated extraction of gas to keep the gas pressure
constant inside the well and thus allow the extraction of oil
without any inconvenience. For exemplary purposes and to
further improve the understanding of the present invention,
Figure 1 illustrates the pumping unit in connection with the
respective parts of the well. As mentioned above, as it is an
exemplary scheme, both the separation distances and the
dimensions of the illustrated components have been illustrated
disproportionately, it being understood that this is not a
limitation for the invention and that in practice it correctly
adapts to the demands of the place.
Thus, and according to figures 1 to 4, the pumping
unit for oil wells of the present invention is indicated by
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the general reference 1 and comprises at least one compressor
cylinder 2 having an upper part 3 on which an upper sealing
cover 4 is mounted and a lower part 5 on which a lower sealing
cover 6 is mounted, both covers 4 and 6 being fixed to the
cylinder 2 by respective bolts, pins or similar fixing
elements. Likewise, said compressor cylinder 2 comprises an
upper gas cylinder inlet/outlet mouth 7 provided in the upper
part 3 and a lower gas cylinder inlet/outlet mouth 8 provided
in the lower part 5.
Internally, the compressor cylinder 2 comprises a
double-acting piston 9 whose drive shaft 10 passes through the
upper cover 4 and has a proximal end that has a connection
element 11 provided with a bearing 12 on which a connecting
shaft 13 is fixed, said connecting shaft 13 allowing the
connection between said driving shaft 10 and a respective
connecting rod 14 which is connected to a drive motor 15-
reducer 16 by means of the shaft 17 of the latter. The drive
motor 10 may be a combustion, hydraulic or electric drive
motor, but it is preferably an electric motor which is
operatively connected to a pressure switch 18 by a pressure
transmitter 41 which is used to control the speed of said
motor -reducer, the pressure switch 18 being used to set or
establish the start/stop pressure and being operatively
connected to the well, more particularly to the annulus space
between the casing and the extraction pipe. In this way, the
pressure in the well can be programmable without any
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inconvenience, this not being possible by any of the
conventional devices of the prior art since they operate with
the beam pump stroke and there is no way of being able to
program the pressure required in the well.
The pressure transmitter 41 measures the pressure in
the annulus and regulates the rotational revolution of the
motor so that the piston moves at a greater or lower speed
inside the compressor cylinder. This allows the extraction of
gas in accordance with gas pressure existing inside the
annulus. By way of example, but not limiting the invention, if
the gas pressure existing within the annulus space exceeds the
maximum pressure limit necessary to allow the extraction of
oil, the pressure transmitter 41 sends a signal to the
variable speed drive of the motor so that it rotates at higher
revolutions and thus generating a greater speed in the piston
movement, consequently extracting a greater amount of gas from
the annulus in order to reduce the pressure existing in it.
Likewise, the use of the pressure transmitter makes it
possible to know the pressure in the annulus and to maintain
the ideal pressure therein on a constant basis. In turn, owing
to the pressure switch arrangement and the pressure
transmitter, the required pressure inside the well can be
programmable according to the operating conditions of the
moment.
For its part, the connecting rod 14 provides an
eccentric movement rectilinear to the drive shaft 10 of the
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piston 9 which moves longitudinally inside the compressor
cylinder 2 to allow the entry of gas as well as,
simultaneously, its compression and discharge. When said
driving shaft 10 performs a rectilinear eccentric movement, it
causes the compressor cylinder 2 to pivot in a tilting manner.
To facilitate the tilting movement of the compressor cylinder
2, a pivoting lower end is provided which comprises a lower
arm 19 provided with a bearing 20 through which a shaft 21
passes whose ends are fixed to respective lateral support
plates (not shown) provided with bearings (not shown) and
which are mounted on a frame (not shown) that supports the
general structure of the unit of the invention. In this way,
pivoting from the lower end is allowed accompanying the
eccentric rectilinear movement of the drive shaft 10 and the
tilting movement of the cylinder 2.
On the other hand, the invention comprises at least
one main gas inlet 22 in connection with the well annulus and
at least one main gas outlet 23 in connection with the gas
production line and/or related reservoirs. Although, according
to the direction illustrated in Figures 1 to 4, it has been
indicated that the main gas inlet 22 is on the right, while
the main gas outlet is on the left, this does not imply that
the invention is limited to said configuration, but other
arrangements can be considered and used without any
inconvenience.
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The main gas inlet 22 bifurcates and projects into a lower
gas inlet 24 which is in connection with the lower gas cylinder
inlet/outlet 8 of the lower part 5 of the cylinder 2 through a
unidirectional check valve 25, and in a upper gas inlet 26 which is
connected to the upper gas cylinder inlet/outlet 7 of the upper
part 3 of the compressor cylinder 2 by another unidirectional check
valve 27. In turn, the present invention has a lower gas outlet 28
which is connected to the lower gas cylinder inlet/outlet 8 by a
unidirectional check valve 29 and an upper gas outlet 30 which is
connected to the upper gas cylinder inlet/outlet 7 through another
unidirectional check valve 31, both gas outlets 28 and 30 extending
and being connected to the main gas outlet 23.
It is noted that projections and bifurcations
mentioned above include tubes or pipes 32 as well as bends 33,
shut-off valves, connectors, flanges, seals, stuffing boxes,
etc., as best illustrated in Figures 1 to 4. Likewise, the
main gas inlet 22 and the main gas outlet 23 have connectors
34 and are connected to the well and reservoir/production line
respectively by means of a conduit 40 or conduits such as
duct(s), pipe(s), hose(s) or the like. More particularly, and
in accordance with Figure 1, it can be seen that the main gas
inlet 22 is in connection with a suction gas outlet 35 from
which the gas of the well annulus comes, while said main
outlet of gas 23 is in connection with a discharge gas inlet
36 which is projected towards the gas production line and/or
related reservoirs. Also, in said figure 1 some components of
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those parts that are usually used in wells have been
illustrated for exemplary and helping purposes for a better
understanding of the present invention. Wherein, said
components that are illustrated are the "casing" 37, pipe 38
and rod 39 among many others.
By way of example, but not limiting the invention,
according to what is illustrated in Figure 3, when the piston
9 moves upwards, the gas entering through the main gas inlet
22 is projected entering the cylinder 2 through of the lower
gas inlet 24 - lower gas inlet/outlet 8. Simultaneously, it
can be seen that the gas that was previously inside the
cylinder is compressed and discharged through the upper gas
cylinder inlet/outlet 7, passing through the upper gas outlet
30 and finally being discharged through the main gas outlet
23.
On the other hand, figure 4, when the piston 9 moves
down, the gas entering through the main gas inlet 22 is
projected entering the cylinder 2 through the upper gas inlet
26 - upper gas cylinder inlet/ outlet 7. Simultaneously, it
can be seen that the gas that previously entered the cylinder,
according to figure 3, is compressed and discharged through
the lower gas cylinder inlet/outlet 8, passing through the
lower gas outlet 28, and finally being discharged through the
main gas outlet 23.
The use of the unidirectional check valves 25, 27, 29
and 31, define the direction of gas flow for both the entry
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and exit from/to the cylinder, thus avoiding the possible
return of the gas. Likewise, both the direction of gas
circulation and the main gas inlet and outlet are not limited
to what has been described above, but can be adapted for
having other configurations without any inconvenience.
By way of example, but not limiting the invention,
some tables are attached showing the results obtained by the
pumping unit of the invention:
Discharge flow tables: thousands of cubic feet of gas
under standard conditions per day (MSCF/D - thousand standard
cubic feet per day)
Calculation equation:
8.73 x /0-5 x D2 x L x RPM x Q - PS;
Calculations should be made with absolute pressures.
Piston diameter 6"
Piston Revolution per
netminute (RPM) in
suction
stroke gear box outlet
(inches) (psig) 10 20 30
0 4.7 9.42 14.1
5 6.3 12.6 18.8-
10 7.8 15.7 23.5
10 15 9.4 18.8 28.3'
11.0 21.9 -32.9
12.6 25.1 -37.7
14.1 28.3 42.4
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Piston diameter 8"
Piston Revolution per
netminute (RPM) in
suction
stroke gear box outlet
(inches) (psig) 10 20 30
0 13.4 26.8 40.2
17.9 35.8 53.6
22.3 44.7 67.0
16 15 26.8 53.6 80.4
31.2 62.5 93.7
35.7 71.5 107.2
40.2 80.4 120.7
Torque table: (depending on pressure difference,
diameter and effective stroke of the piston) Newton-meter
5 Calculation equation:
# N - m = 4.44 x 10-2x D2 x L (Pd - Ps);
wherein, pressure difference: Discharge pressure -
Suction pressure.
Pressure
Piston diameter: 6 Piston diameter: 8
difference
inches inches
(psi)
AP 10 12 14 16 10 12 14 16
5 80 96 112 128 142 , 170 199 227
10 160 192 224 256 284 341 398 454
15 240 287 335 383 426 511 596 681
20 319 383 447 511 568 681 795 909
25 399 479 559 639 710 852 994 1136
H 0
30 479 575 671 767 852 1022 1193 1363
35cla
559 671 783 894 994 1193 1391 1590 FcC
U
639 767 894 1022 1136 1363 1590 1817 H
1-1
719 862 1006 1150 1278 1533 1789 2044 rt
799 958 1118 1278 1420 1704 1988 2272
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Well tests
Prior to the use of the pumping unit of the invention:
The selected well had a production of 02 BO x 0 BW, in
October 2016, taking the following physical measurement:
Production before compressor Current production with compressor
Incremental =Suction Remark
Compressor Well P Tbg P Csg
Oil Water P Tbg 2 Csg Manometric Oil Water Manometric de
Oil
(psi) (Psi) (psi) (Psi)
10 - 280 20- 300 Operating
BMCG - 20 -
compressor,
4453 2 0 10 3 psi/2 min 8 0 -4 psi/
30 6 -4 psi
GMP-09 60
having no
40 sec sec.
, problem
Total Production Increase 6
As it can be seen from the table above, the pressure
without the compressor or pumping unit was 3 psi, changing to
-4 (four negative) psi by using the compressor or pumping unit
of the present invention, resulting consequently that, that
difference of vacuum pressure allows a greater production.
Using the pumping unit of the invention:
Fluid
Date Well details l Dynamometricevel
PPRL Torque Remarks Recommendation
card
(FLAP)
10 0
October
Decrease
22"' October 4533 pf72, 2.9 1374. 36" 3.58 24 1345 29.
29' 1,993 15,977 fl=p=d. t= working time
2016
40. ro 20 x 4.
One can remarkably observe an increase of the production
from 2 BOPD to 8 BOPD, operating 24 hours under the same extraction
conditions as those prior to the use of the pumping unit, thus
obtaining better manometric tests.
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In this way, the pumping unit for oil wells of the present
invention is constituted and constructed, which is independent from
the operation of the AIB rod pump and in turn, it allows the
variation of the piston moving speed to extract a greater or lesser
amount of gas in accordance with the existing pressure in the well
annulus owing to the novel arrangement of the pressure transmitter
and pressure switch. That is to say, the pressure is programmable,
this being not possible with any conventional mechanism of the
prior art. It is emphasized that the gas extraction cycle is
continuous during the period of oil extraction.
Furthermore, some of the advantages of the unit of the
present invention lie in:
The use of an external and independent pumping unit instead
of a traditional reciprocating gas compressor CGBD (mechanical
pumping), allows to further reduce gas pressure in the well annulus
since its action is not limited by the geometry of the pumping rod
unit, nor the low GPM (<9), wherein independence of frequency of
action of the pumping unit allows it to be smaller;
The pumping unit allows maintaining a constant gas pressure
in the well, since it has the pressure switch and pressure
transmitter that controls the piston speed according to the gas
flow to be extracted, pressure being programmable;
Higher gas extraction capacity;
Increases production, with less flowing pressure;
Increase in recoverable reserves (vacuum in annulus);
Easy installation and transfer of the pumping unit;
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It does not generate imbalance in alignment and balancing
in a mechanical pumping unit;
Totally compact pumping unit (small dimensions) reducing
the risk of accidents (there is no work at height);
Easy acquisition of spare parts;
Durability of materials used in its manufacture;
In case of maintenance of the compressor cylinder, it is
replaced in approximately 30 minutes by another backup unit;
It is not necessary to stop the AIB rod pump;
The unit of the invention is environment friendly since it
does not generate excessive noise;
It is not obstructive as it occupied little physical space
in the well's location;
Compact compressor cylinder (fewer parts and flanges with
uniform adjustment); improved metallurgy (high quality steel and
aluminum), last generation seals (in stuffing box, flanges and
piston)
Graphite Teflon seals for greater efficiency and
durability;
Compressor accessories (horizontal check valves, bends,
tee's, tubes, etc.) designed to work in media with gas flow;
Decrease in manufacturing cost; and
Longer useful life and efficiency of the pumping unit due
to less maintenance and repairs, among many other advantages.
Thus, the invention allows varying the piston drive amount
according to what we want by means of the variable speed drive that
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drives the motor and without depending on the frequency of
actuation of the mechanical pumping as it occurs with the units of
the prior art. In turn, the unit of the invention allows the
compressor to be smaller since there being more frequency a smaller
compressor is needed, thus allowing regulating the gas pressure of
the well as desired owing to the arrangement of the pressure switch
and pressure transmitter connected to the casing that, according to
the desired programmed pressure, varies the speed of the motor that
drives the compressor and therefore extracts more or less gas.
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