Information
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Patent Grant
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6666269
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Patent Number
6,666,269
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Date Filed
Wednesday, March 27, 200222 years ago
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Date Issued
Tuesday, December 23, 200320 years ago
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Inventors
-
Original Assignees
-
Examiners
Agents
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CPC
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US Classifications
Field of Search
US
- 166 68
- 166 105
- 166 1051
- 166 1054
- 166 304
- 166 311
- 166 369
- 137 13
- 417 54
- 417 65
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International Classifications
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Abstract
An electric submersible pumping system provides for the production of fluids from a well and for limiting the amount of sediment accumulation in the well. The apparatus includes an electric submersible pumping system lowered into a well on a production tubing. The electric submersible system includes an electric submersible pump having an intake at or near a lower end thereof. A seal is connected to the intake and a motor is connected to a lower end of the seal. The apparatus further includes an auxiliary pump having an auxiliary pump discharge at an upper end thereof and an auxiliary pump intake at a lower end thereof. The auxiliary pump is connected to the motor. The system is lowered into the well so that it is positioned below the perforations in a well which communicate a producing formation with the interior of the well. The auxiliary pump intake will receive fluid along with sediments that may be produced by the formation. The auxiliary pump will pump the fluid and sediments upwardly through the auxiliary pump discharge and through discharge tubes connected to the discharge. At least a portion of the fluids and sediment pumped upwardly by the auxiliary pump will be communicated into the production pump intake and produced upwardly through the production tubing along with other fluid from the well. Because the auxiliary pump is continuously taking in fluid, there is a downward flow of fluid past the motor in the well which will cool the motor in the electric submersible pumping system.
Description
BACKGROUND OF THE INVENTION
The present invention is directed to a submersible pump for producing fluid from well intersecting a producing formation, preferably a hydrocarbon-producing formation, and more particularly is directed to an apparatus for producing fluid from a well and for limiting the accumulation of sediment in wells in which the formation produces solids along with the production fluids.
It is well known that in producing oil and/or gas wells, the fluid in the well may be elevated to the surface by utilizing a pump installed in the well. One type of pump that is often utilized is an electric submersible pump. Electric submersible pumps may be used for a variety of reasons, such as for example in wells where artificial lift is required when formation intersected by the well does not provide the necessary lift to produce the fluid to the surface.
Electric submersible pumps, depending upon the application, are often deployed in wells with open rat holes. That is, the pumps are deployed in wells which have casing cemented in a wellbore to a certain depth and wherein the wellbore is drilled to a greater depth so that there is an uncased, or open rat hole below the casing. In some formations intersected by the well, the fluid produced therefrom will contain solids. The solids tend to get deposited in the rat hole, and over time the deposits, also referred to as sediment, can cause production problems such as reduced well productivity, and cause equipment problems, such as motor overheating. If the electric submersible pump system is deployed in the well below the perforations in the casing through which the formation fluid is communicated into the well, there may be insufficient flow of fluid around the motor in the electric submersible pumping system to cool the motor.
When an electric submersible pump is placed above the perforations, flowing well fluid will produce some motor cooling. When the system is placed below casing perforations, the motor in the electric submersible pumping system is generally not exposed to flowing well fluid. Thus, there is a need for a method and apparatus for limiting the accumulation of sediments in a rat hole and for providing cooling to a motor used in an electric submersible pumping system when the system is placed below perforations in a well.
SUMMARY OF THE INVENTION
The present invention provides a method and apparatus for producing fluid from a well, for limiting the accumulation of sediments in the well, and for providing cooling to motors used in electric submersible pump systems when the system is placed below perforations in the well. The apparatus comprises an electric submersible pumping system lowered into a well on a production tubing. The electric submersible pumping system includes a submersible production pump, a seal section connected to a lower end of the pump, and a submersible motor connected to the seal section for driving the production pump. A production pump intake is positioned at or near the lower end of the production pump above the seal section. A submersible auxiliary pump is connected below the motor. The auxiliary pump has an auxiliary pump intake at or near a lower end thereof, and includes an auxiliary pump discharge positioned between the submersible motor and the auxiliary pump. The auxiliary pump discharge is designed such that the motor is effectively sealed from the auxiliary pump discharge to prevent fluid from the auxiliary pump from being pumped or discharged into the submersible motor. The auxiliary pump discharge has at least one and preferably has a plurality of discharge ports.
The production tubing preferably has a sufficient length so that the electric submersible pumping system is located in the well below the perforations that communicate the producing formation with the interior of the well. Fluid from the well will be drawn in through the auxiliary pump intake, will be pumped upwardly through the auxiliary pump discharge and then upwardly in the well above the submersible motor, which drives both the production pump and the auxiliary pump. In wells where the producing formation produces sediment along with the fluid, some of the sediment that will naturally flow downward in the well due to gravity will be drawn in through the auxiliary pump intake and will be pumped upwardly in the well along with the fluid pumped by the auxiliary pump.
The apparatus preferably includes at least one and preferably a plurality of discharge tubes or discharge tubings connected at a lower end to the auxiliary pump discharge. The discharge tubes extend upwardly in the well past the submersible motor. The tubes may extend upwardly past the production pump intake and may expel the fluid and sediments pumped upwardly therethrough into the interior of the well above the production pump intake. A portion of the fluid expelled from the discharge tubes along with a portion of the sediment will flow downwardly in the well. A portion of the fluid expelled from the discharge tubes along with a portion of the sediment will be taken in through the production pump intake and will, along with other fluid from the well, be produced upwardly by the production pump through the production tubing on which the system is lowered. In a separate embodiment, the upper ends of the discharge tubes may be communicated directly to the production pump intake so that all of the fluid and sediment taken in and pumped upwardly through the discharge tubes by the auxiliary pump will be received in the production pump intake and will be produced upwardly by the production pump through the production tubing. Because the auxiliary pump will pump sediments upwardly so that some sediment can be produced upwardly through the production tubing, the invention limits the accumulation of sediment in the well.
In addition to limiting the accumulation of sediment in the well the present invention provides a method and apparatus for cooling the submersible motor in an electric submersible pumping system when the system is placed below perforations in the well. The auxiliary pump of the present invention pumps fluid upwardly in the well which allows for downward flow of fluid in the well past the motor. The auxiliary pump preferably pumps fluid upwardly at a rate sufficient to create a downward flow in the well of preferably at least about 1 ft/second past the motor, so that the downward flow will provide efficient motor cooling.
It is therefore an object of this invention to provide a method for producing well fluid from a well in which the producing formation produces sediments along with fluid, and for limiting the accumulation of the sediments in the well. It is a further object of the invention to provide a method for producing fluid from a well in which the pumping system is located below the perforations and for cooling the motor utilized in the pumping system.
The foregoing and other objects, advantages and features of the present invention will become apparent upon reading the following detailed description in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
schematically shows the apparatus of the present invention lowered into a well.
FIG. 2
shows a second embodiment of the apparatus of the present invention.
FIG. 3
shows an embodiment of a discharge head of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings and more specifically
FIG. 1
, an apparatus
10
for producing fluid from a well
15
is shown and described. Apparatus
10
is shown lowered into a well
15
comprising a casing
20
cemented in a wellbore
25
. Casing
20
has a lower end
30
, and thus well
15
has an open or uncased rat hole
32
comprising the lower portion of wellbore
25
. Well
15
has a bottom
33
. Casing
20
defines a casing interior or well interior
34
. Production fluids are communicated into well interior
34
through perforations
36
, which communicate the interior
34
with producing formation
38
. Lower end
30
could be positioned above perforations
32
, or could extend below the cement. In the embodiment shown, lower end
30
is below perforations
36
. Casing
20
and apparatus
10
define an annulus
40
therebetween.
Apparatus
10
is shown lowered into well
15
on a production tubing
42
. Apparatus
10
includes an electric submersible pumping system
44
having an auxiliary pump
46
connected to a lower end thereof.
Electric submersible pumping system
44
includes an electric submersible pump
48
having upper end
50
connected to production tubing
42
and having a lower end
52
. An intake
54
, having intake ports
55
, is connected to the lower end
52
of electric submersible pump
48
, which may also be referred to as production pump
48
. Intake
54
has upper end
56
and lower end
58
. Production pump intake
54
may be connected to or may be integrally formed with production pump
48
. A motor
60
for driving production pump
48
is connected in electric submersible pumping system
44
below intake
54
. Motor
60
is connected to a power source (not shown) with power cable
61
. The motor
60
has an upper end
62
and a lower end, or motor base
64
. A seal section
66
is connected between motor
60
and intake
54
. Seal section
66
is connected at its upper end
68
to intake
54
and at its lower end
70
to motor
60
. Motor
60
is thus connected to the lower end of pump
48
with seal section
66
and intake
54
. Production pump
48
, intake
54
, motor
60
and seal section
66
are all known in the art.
Auxiliary pump
46
is connected at its upper end
71
to the lower end
64
of motor
60
with an auxiliary pump discharge
72
, which may be referred to as a pump discharge head
72
. Auxiliary pump
46
can be a standard electric submersible pump connected to the lower end
64
of motor
60
at auxiliary pump discharge
72
, so that auxiliary pump
46
pumps in the same direction as production pump
48
. The arrangement can be reversed if desired. Auxiliary pump discharge
72
has upper end
74
connected to motor
60
and lower end
76
connected at upper end
71
of auxiliary pump
46
. Auxiliary pump discharge
72
incorporates a high pressure mechanical seal which connects to motor base
64
. Auxiliary pump
46
has an auxiliary pump intake
78
comprising a plurality of intake ports
80
connected to the lower end
81
thereof. Pump intake
78
may be integrally formed with or it may be connected to auxiliary pump
46
in any manner known in the art.
Apparatus
10
includes at least one, and in the embodiment shown includes two, discharge tubings
82
. Discharge tubings
82
have a lower end
84
and an upper end
86
. Lower end
84
is connected with auxiliary pump discharge
72
at discharge ports
85
. Discharge tubing
82
extends upwardly therefrom and terminates at upper end
86
above seal
66
. In the embodiment shown in
FIG. 1
, upper end
86
is positioned above intake ports
55
in intake
54
.
FIG. 2
shows an embodiment of the present invention in which upper ends
86
are connected directly to intake
54
.
An embodiment of an auxiliary pump discharge
72
is shown in FIG.
3
. Auxiliary pump discharge
72
may comprise an upper portion
90
threadably connected to a lower portion
92
. A shaft portion
94
extends through both upper portions
90
and
92
and as understood in the art will be connected to a shaft that extends upwardly into and through motor
60
to drive electric submersible pump
48
and will also extend downwardly into and will drive auxiliary pump
46
. A spider bearing
96
supports shaft portion
94
and, as known in the art, will allow fluid flow upwardly through discharge head
72
. Shaft portion
94
is sealingly disposed in upper portion
90
with a high pressure seal
98
. As set forth previously, auxiliary pump discharge
72
is connected at its upper end
74
, which is defined on upper portion
90
to motor
60
. Auxiliary pump discharge
72
is connected at its lower end
76
to auxiliary pump
46
.
The operation of apparatus
10
is as follows. Apparatus
10
is lowered into the well is on a production tubing
42
until it is positioned below perforations
36
. Fluid from formation
38
is communicated into well interior through perforations
36
. Sediment in fluids from formation
38
may also be communicated into well interior
34
through perforations
36
. Once apparatus
10
is in place, motor
60
is actuated. Motor
60
drives production pump
48
and also drives auxiliary pump
46
. Once motor
60
is actuated to drive pumps
48
and
46
, production pump
48
will draw fluid from interior
34
through intake
54
. Auxiliary pump
46
will draw fluid from interior
34
through ports
80
in intake
78
. Fluid drawn in through intake
78
is discharged through discharge ports
85
in auxiliary pump discharge
72
into discharge tubings
82
through the lower ends
84
thereof.
In the embodiment shown in
FIG. 1
, well fluid from auxiliary pump
46
is discharged out the upper ends
86
of discharge tubings
82
. A portion of the well fluid expelled from discharge tubing
82
will be drawn in through intake
54
and will, along with other well fluid drawn in through intake
54
, be produced up production tubing
42
with production pump
48
. A portion of the fluid expelled from the upper end
86
of tubings
82
will, due to gravity, flow downwardly in the well, some of which will again be taken in through intake
78
along with other fluid in the well. Production pump
48
will produce additional fluid from the well through intake
54
and production tubing
42
, along with the fluid and any sediment pumped upwardly by auxiliary pump
46
.
In wells where sediments are produced with fluid from the producing formation, the fluid drawn into auxiliary pump
46
will contain some sediments and will thus keep the sediments from falling to the bottom of the rat hole. Fluid that enters the auxiliary pump, along with the sediments therein, will be pressurized and produced through the discharge tubing
82
. In the embodiment shown in
FIG. 1
, a portion of that fluid including some of the sediment therein, will be drawn in through intake
54
and produced up the production tubing
42
. In the embodiment shown in
FIG. 2
, all of the fluid and all of the sediment taken in through intake
78
is communicated through discharge tubings
82
directly into intake
54
, so that all of the fluid and sediment drawn in through intake
78
will be produced upwardly by production pump
48
through tubing
42
.
In addition to limiting the amount of sediment that will collect at the bottom of the rat hole, the present design provides for motor cooling in electric submersible pumping systems positioned below perforations. The system may be designed such that pump
46
draws fluid into intake
78
at a rate such that downward flow of the fluid in the well is at a sufficient velocity, preferably at least about 1 ft/second, past the motor. In the embodiment shown in
FIG. 2
, the auxiliary pump may also act as a charge pump since the fluid therein will have little or no free gas and is communicated directly into intake
54
and thus will reduce the gas fraction feed into the production pump that might otherwise cause gas locking in wells having a high amount of gas.
While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown in the drawings and have been described in detail by way of example only. It is understood that the invention is not intended to be limited by the particular forms or embodiments disclosed. Rather, the invention covers all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.
Claims
- 1. An apparatus for producing fluid from a well intersecting a fluid producing formation, the apparatus comprising:a first submersible pump having a first intake for receiving fluid from said well, wherein the fluid received in the first intake is pumped upwardly in said well by the first submersible pump; a seal section connected to said first submersible pump; a motor connected to said seal section for driving said first submersible pump; a second submersible pump positioned below said motor, said second submersible pump having a second intake at or near a lower end thereof for receiving fluid from said well; a pump discharge located between said motor and said second intake, said pump discharge defining at least one discharge port; and at least one discharge tubing connected to said pump discharge and extending upwardly therefrom in said well, said discharge tubing being communicated with said at least one discharge port, wherein said second submersible pump urges the fluid received in the second intake upwardly through said at least one discharge tubing.
- 2. The apparatus of claim 1, wherein the fluid urged upwardly through said discharge tubing is discharged from said discharge tubing above said motor.
- 3. The apparatus of claim 2, wherein the fluid urged upwardly through said discharge tubing is discharged directly into said first intake of the first submersible pump.
- 4. The apparatus of claim 2, wherein said fluid urged upwardly through said at least one discharge tubing is expelled through an open end thereof into an interior of said well above said motor.
- 5. The apparatus of claim 1, wherein said pump discharge comprises a plurality of discharge ports, each said discharge port having a discharge tubing communicated therewith.
- 6. The apparatus of claim 1, wherein each of said first and second submersible pumps is adapted to produce sediment upwardly.
- 7. A method of producing fluid from a cased well, the cased well defining a well interior, the casing having perforations therethrough to communicate fluid from a formation intersected by said well into the well interior, the method comprising:lowering an electric submersible pumping system into the well on a production tubing, the electric submersible pumping system comprising a production pump, a motor for driving said production pump, said motor being positioned below said pump, and an auxiliary pump positioned below said motor; urging fluid from the well interior upwardly through at least one discharge tube with said auxiliary pump; discharging the fluid from said at least one discharge tube above said motor; and pumping fluid from the well interior upwardly through said production tubing with said production pump, wherein the fluid pumped upwardly through the production tubing comprises at least a portion of the fluid discharged from the discharge tube and additional fluid drawn into the production pump from the well interior.
- 8. The method of claim 7, wherein said discharging step comprises discharging said fluid from said at least one discharge tube directly into an intake of said production pump.
- 9. The method of claim 7 further comprising positioning said electric submersible pumping system below said perforations in said well.
- 10. The method of claim 9, wherein said auxiliary pump draws fluid from the well interior into an auxiliary pump intake at a rate sufficient to cause a flow of fluid in the well interior downwardly past said motor to cool said motor.
- 11. An apparatus for producing well fluid from a well intersecting a producing formation, the well having a casing therein, the casing having perforations for communicating fluid from said formation into a well interior, the apparatus comprising:a production pump lowered into said well on a production tubing; a motor positioned below said production pump for driving said production pump; an auxiliary pump connected to a lower end of said motor; an auxiliary pump intake for receiving said well fluid; and an auxiliary pump discharge for discharging said well fluid received in said auxiliary pump intake.
- 12. The apparatus of claim 11, further comprising at least one discharge tube connected at a first end to said auxiliary pump discharge, said at least one discharge tube having a second end, said second end being located above said motor.
- 13. The apparatus of claim 12, wherein said second end of said at least one discharge tube is connected to an intake of said production pump, so that all of said well fluid discharged from said discharge tube is communicated into said intake of said production pump.
- 14. The apparatus of claim 12, wherein said well fluid received in said auxiliary pump intake is discharged through said second end of said at least one discharge tube into the well interior above said motor.
- 15. The apparatus of claim 12, wherein said well fluid received in the auxiliarm pump intake is discharged through said second end of said at least one discharge tube into said well interior above an intake for said production pump.
- 16. The apparatus of claim 11, wherein said motor drives said auxiliary pump.
- 17. The apparatus of claim 11, wherein said production tubing has a length such that said production pump is positioned below said perforations in said casing.
- 18. A method for limiting the accumulation of sediment in the bottom of a well in which a producing formation produces sediment along with a production fluid, the well having perforations to communicate said producing formation with said well, the method comprising:lowering an electric submersible pumping system into said well on a production tubing, the electric submersible pumping system comprising a production pump, an auxiliary pump, and a motor between said production pump and said auxiliary pump; positioning said electric submersible pumping system below said perforations; pumping production fluid in said well, along with sediment falling downwardly in said well, upwardly with said auxiliary pump past said motor; and producing at least a portion of said production fluid and sediment pumped by said auxiliary pump upwardly through a production tubing with said production pump.
- 19. The method of claim 18, wherein all of said production fluid and sediment pumped by said auxiliary pump is produced upwardly by said production pump.
- 20. The method of claim 18, further comprising:expelling said production fluid and sediment pumped by said auxiliary pump into said well above said motor; and allowing a portion of said production fluid and said sediment pumped by said auxiliary pump to flow downwardly in said well past said motor.
- 21. The method of claim 18, further comprising producing additional production fluid from said well through said production tubing with said production pump along with said at least a portion of said production fluid and sediment pumped upwardly by said auxiliary pump.
- 22. A method for producing fluid from a well intersecting a producing formation, comprising:lowering an electric submersible pumping system into said well, the pump system comprising a first submersible pump, a second submersible pump positioned below said first submersible pump, and a motor between said first and second submersible pumps for driving both said pumps; withdrawing fluid from said well with said second submersible pump to create a downward flow in the well past said motor at a rate sufficient to cool said motor; discharging said fluid withdrawn by said second submersible pump into said well above said motor; and producing fluid from said well upwardly through a production tubing with said first submersible pump, wherein the fluid produced upwardly through the production tubing comprises fluid received from the well in an intake for the first submersible pump.
- 23. The method of claim 22, said discharging step comprising:communicating said fluid withdrawn by said second submersible pump upwardly past said motor through at least one discharge tube; and expelling said fluid withdrawn by said second submersible pump from said at least one discharge tube above said motor.
- 24. The method of claim 23, said expelling step comprising expelling said fluid from said at least one discharge tube directly into an intake of said first submersible pump.
- 25. The method of claim 23, said expelling step comprising expelling said fluid from said at least one discharge tube into an interior of said well above said motor.
- 26. The method of claim 22, wherein said second pump withdraws sediment along with fluid, and wherein at least a portion of the fluid and sediment discharged into said well above said motor is produced upwardly through the production tubing by said first submersible pump, along with additional fluid from the well.
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Kind |
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Plummer et al. |
Apr 1986 |
A |
4749034 |
Vandevier et al. |
Jun 1988 |
A |
5845709 |
Mack et al. |
Dec 1998 |
A |
6260627 |
Rivas |
Jul 2001 |
B1 |