Information
-
Patent Grant
-
6361342
-
Patent Number
6,361,342
-
Date Filed
Monday, September 11, 200023 years ago
-
Date Issued
Tuesday, March 26, 200222 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Sircus; Brian
- Hyeon; Hae Moon
Agents
- Bracewell & Patterson, L.L.P.
-
CPC
-
US Classifications
Field of Search
US
- 439 275
- 439 589
- 439 272
- 439 276
- 277 615
- 277 612
- 277 620
-
International Classifications
-
Abstract
An electric submersible pump is provided having a pothead connector for use to connect a downhole cable to an electric motor of the submersible pump. The pothead connector has a housing having an upper and a lower end. The downhole cable has electrical conductors which are separately covered by insulation layers. The downhole cable extends through the upper end and into the housing, and then is electrically connected to the electric motor through the lower end of the housing. Two insulating blocks are provided in the lower end of the housing for separating electrical conductors in alignment for mating with a connector mounted to the electric motor. A conductor pin is secured to the insulating block and to each of the conductors. An elastic sealing ring is disposed within the housing, intermediately between the two insulating blocks. An epoxy layer are disposed within the upper end of the housing.
Description
BACKGROUND OF THE INVENTION
The present invention relates in general to downhole electrical connectors for use in oil field applications, and in particular to a downhole pothead seal for connecting a motor lead to an electrical motor of a submersible pump assembly using pressure energized lip seals.
DESCRIPTION OF PRIOR ART
Electric submersible pumps have been used in oil wells to pump well fluids for many years. These types of prior art submersible pumps include electrical connectors for connecting the electric motors of the pumps to electrical conductors of downhole cables. These pumps are often used in corrosive environments such as wells that produce sour gas, and hydrogen sulfide (H
2
S). Electrical connectors for electric submersible pumps typically have elastomeric seals or pothead connectors.
A problem encountered with pothead connections is the movement of conductors within the connector during installation and/or handling. This movement can cause shear stress damage to the cable insulation and the insulation within the connector itself, either of which is likely lead to the failure of the electrical connection.
As is particularly well known in the oil industry, the maintenance of power to such a pump is critical and at the same time made difficult by reasons of the extreme in pressures and temperatures and the character and nature of the well fluids to which the portion of the electric feedthrough system at the pump motor is subjected. That many problems have resulted from such circumstances has been frequently exhibited in the prior art apparatus applied for the same purpose. These problems have stemmed from many factors, not the least of which has been design characteristics of prior art apparatus which in many cases include the requirement for complete bonding of insulators and dielectrics thereof to one another and to the conductors which they peripherally encase as well as to the shell or housing by which they themselves are encased. Such a requirement is most difficult to satisfy. Where the bonding is not perfect, the pressure and temperature conditions within a well will make the electric feedthrough apparatus subject to infiltration by and seepage therein of well fluids with many undesirable results: short circuiting of the pump or motor, and electrical arcing or fire.
The improvements of the present invention substantially obviate many of the aforementioned problems. The inventor is not aware of any prior art which is specially pertinent to the improvements of the present invention as herein set forth and specifically claimed.
SUMMARY OF THE INVENTION
A pothead connector for use with an electric submersible pump is provided to connect a downhole cable to an electrical motor of the submersible pump. The pothead connector has a housing having a rearward or upper end and a forward or lower end. The downhole cable has electrical conductors that are separately covered by insulation layers. The downhole cable extends through the upper end and into the housing, and then is electrically connected to the electric motor through the lower end of the housing.
Two insulating blocks are provided in the lower end of the housing for separating and holding the electrical conductors in alignment and to prevent lateral movement of the conductors within the housing. A bore is provided through both the insulating blocks for each of the conductors. Each bore is provided with annular shoulders that face each other, one in the upper block and one in the lower block, for supporting and enclosing a seal that is located between the two blocks within the housing. The sealing ring has inner and outer lips some of which face the upper end of the housing, and the remainder of which face the lower end of the housing.
The inner lips of the seal provide a seal against the electrical conductors, and the outer lip of the seal provides a seal against the housing in the embodiment shown. The seal has a central web where all of the inner lips are connected to the outer lip. The seal also has openings for receiving each electrical conductor to feed them to a downhole pump motor.
BRIEF DESCRIPTION OF THE DRAWINGS
The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein:
FIG. 1
is an elevational view of a well within which an electrical submersible pump is disposed;
FIG. 2
is a longitudinal cross sectional view depicting the interior of the pothead connector made according to the present invention, mounted to the motor lead of the downhole electric cable.
FIG. 3
is a partially exploded partially cross sectional view of the pothead connector of
FIG. 2
, with the sectional view of the seal being along line
3
—
3
of FIG.
4
.
FIG. 4
is a front view of the seal of FIG.
3
.
FIG. 5
is an isometric view of the seal and lower insulating block of FIG.
3
.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
FIG. 1
is an elevational section view of well
10
having electric submersible pump
12
disposed therein, mounted to tubing
14
. Pump
12
includes an electric motor
16
and a pump section comprising centrifugal pump assembly
18
. Cable
20
extends downhole, terminating in a motor lead to provide power to electric motor
16
. Pothead connector
22
is mounted to the motor lead of cable
20
, and electrically connects and secures the motor lead of cable
20
to housing
24
of motor
16
.
Referring to
FIG. 2
, the motor lead of cable
20
is a flat cable containing three electrical conductors
26
. Each conductor
26
is surrounded by one or more layers of conductor insulation
28
to protect and insulate the conductors from one another. Metal armor
34
encases and protects the elements of cable
20
.
Connector
22
has a cap
36
that joins a cylindrical base
38
, forming an outer housing. Cap
36
has a tapered interior end which extends around the exterior of armor
34
of cable
20
. The interior of cap
36
is filled with epoxy
40
, which acts as a retaining means to secure conductors
26
within cap
36
in alignment for extending into base
38
and provide strain relief for the cable. Epoxy
40
is a type of epoxy which is rated for high temperature service. The interior surface of cap
36
has a tapered profile, with the upper end periphery being smaller than the lower end periphery. After cap
36
is fastened to base
38
and layer of epoxy
40
is injected and cured, epoxy
40
will prevent movement of cap
36
and base
38
lower relative to armor
34
of cable
20
.
As shown in
FIG. 2
, armor
34
has been stripped back from the terminal end of cable
20
, so that armor
34
has a terminal end which is enclosed within the tapered portion of cap
36
.
An upper insulating block
42
is in base
38
near its upper end, with epoxy
40
being in contact with a upper side of insulating block
42
. The upper insulating block
42
is provided with a plurality of bores
43
(three in preferred embodiment) therethrough for receiving insulated conductors
26
and aligning them with the electrical leads of a pump motor or other downhole device requiring electrical power or control. Conductor insulation
28
of each conductor
26
extends through one of the bores
43
of upper insulating block
42
. As shown in
FIG. 3
, each bore
43
has a counterbore
43
a that is greater in diameter than the upper end of the bore
43
.
Upper insulating block
42
also has a cylindrical wall with an upper portion
42
a
and a lower portion
42
b
of slightly smaller diameter. The upper end of the upper insulating block
42
abuts a shoulder
36
a
in cap. The outer wall portion
42
a
fits closely in the inner diameter of cap
36
and a portion of base
38
.
The materials that are used to form the upper insulating block
42
include various hard engineering grade plastics. The objective of the formulation for the upper insulating block
42
is to obtain a material that will exhibit strength, hardness, and insulating capabilities in the downhole environment. It is preferable that the material will be polyetheretherketone (PEEK).
A seal
44
is located on the forward or lower side of the upper insulating block
42
. At least a portion of the exterior surfaces of insulation layers
28
into passages
45
of seal
44
. The material for the seal
44
is selected so that it will seal directly but not adhere to the insulation layers
28
, the upper insulating block
42
, and the base
38
. Each passage
45
also has an inner lower conical lip
45
a
cylindrical wall
47
c.
Outer conical lips
47
a,
47
b
diverge outward from each other and when installed in base
38
are deformed to a cylindrical shape. Outer upper lip
47
b
seals the inner diameter of base
38
. Seal web
44
a
provides continuity between the inner conical lips
45
a,
45
b
and the outer conical lips
47
a,
47
b.
The web
44
a
attaches to the inside the outer cylindrical wall
47
c
and to the outside of the inner conical lips
45
a,
45
b
between the upper and lower seal. The web
44
a
prevents gas or liquid from penetrating the area between the inner and outer lip seals.
A second or lower insulating block
46
formed of a hard engineering grade plastic is mounted at the forward or lower end of base
38
. The lower insulating block
46
is fixed within base
38
to prevent axial movement of the block within the housing. Insulating block
46
is provided with a plurality of bores
72
(three in preferred embodiment) therethrough for receiving insulated conductors
26
and aligning them with the electrical leads of a pump motor or other downhole device requiring electrical power or control. As shown in
FIG. 3
, each bore
72
, has a counterbore
72
a
that is greater in diameter than the lower end of the bore
72
.
Lower insulating block
46
also has a cylindrical wall with both an upper portion
46
a
and a lower portion
46
b
of slightly smaller diameter than the middle portion
46
c.
The lower end of the lower insulating block
46
abuts a shoulder
38
a
in the base
38
. The outer wall portions
46
b,
46
c
fit closely in the inner diameter of the base
38
.
The materials that are used to form the lower insulating block
46
include various hard engineering grade plastics. The objective of the formulation for the lower insulating block
46
is to obtain a material that will exhibit strength, hardness, and insulating capabilities in the downhole environment. It is preferable that the material will be polyetheretherketone (PEEK).
The lower ends of electrical insulation layers
28
may be disposed within lower insulating block
46
. At the lower end of base
38
, insulation layers
28
are stripped from conductors
26
to provide a terminal end of cable
20
. Connector pins
50
are soldered over the terminal ends of conductors
26
. Connector pins
50
are provided for mating with electrical connectors in electric motor
16
of submersible pump
12
(shown in FIG.
1
). Conductor pin
50
is preferably an elongated cylindrical member. The terminal end of conductor
26
is fixed in opening
55
of pin
50
by a solder weld. As described above, it is preferable that conductor insulation
28
on conductor
26
be stripped back so that conductor
26
may be inserted into and affixed with conductor pin
50
. However, sufficient conductor insulation
28
should be left in place so that as cable
20
is inserted into lower insulating block bore
72
, a portion of conductor insulation
28
is inserted into bore
72
along with conductor
26
. Preferably, conductor insulation
28
will abut against upper end of conductor pin
50
. Conductor pins
50
protrude from base
38
.
Base
38
, insulation
28
, and seal
44
are to be selected of compatible corrosion resistant materials so that seal
44
will seal to the interior perimeter of base
38
and the exterior surface of conductor insulation
28
. The material for seal
44
should also chosen so that the integrity of the seal is not lost due to contraction and/or expansion of the seal
44
under the extreme temperatures that may be encountered downhole.
With reference to
FIG. 2
, assembly of the pothead connector
22
onto cable
20
is now described. Cap
36
is first placed over the terminal end of cable
20
and pushed onto cable
20
, away from the terminal end. Components of cable
20
are then stripped from the terminal end.
The first component of cable
20
which is stripped from the terminal end is metal armor
34
. Armor
34
is stripped far enough from terminal end so that electrical connectors
26
may be separated within cap
36
and aligned for extending into base
38
, for passing into the bores
43
of upper insulating block
42
and bores
72
of lower insulating block
46
.
Conductor insulation
28
is preferably made of a material to which epoxy
40
will bond, such as E.P.D.M. Conductor insulation
28
is stripped from conductors
26
at a distance so that electrical conductors
26
will extend within lower insulating block
46
. The terminal end of conductor insulation
28
will be within lower insulating block
46
.
It is preferable that the elements shown in
FIG. 3
be preassembled. Specifically, seal
44
should be inserted between upper insulating block
42
and lower insulating block
46
. Conductors
26
should then be fed through the two blocks and seal combination, and installed in the base
38
. The base
38
should be attached to the cap
36
. Bolts (not shown) secure cap
36
to base
38
. Conductor
26
should be soldered in place within opening
55
of conductor pin
50
. Conductor pin
50
is then inserted into bore
72
of lower insulating block
46
. Conductors
26
are prevented from lateral movement within the housing due to their immobilization in the lower insulating block
46
. The upper outer cylindrical lip
47
b
seals and fits between the lower portion of the cylindrical wall
42
b
of the upper insulating block
42
and the inside diameter of the upper end of the base
38
. The upper inner conical lips
45
b
seal and fit between the conductors
26
and the counterbores
43
a
in the upper insulating block
42
. The lower outer cylindrical lip
47
a
seals and fits between the upper portion of the cylindrical wall
46
a
of the lower insulating block
46
and the inside diameter of the lower end of the base
38
. The lower inner conical lips
45
a
seal and fit between the conductors
26
and the counterbores
72
a
in the lower insulating block
46
. Liquid epoxy is then poured into cap
36
to provide epoxy layer
40
within cap
36
. Epoxy layer
40
holds electrical conductors
26
in position within cap
36
. Epoxy layer
40
will stabilize conductors
26
to prevent them from moving around and damaging seal
44
.
Epoxy layer
40
is then cured by heating to 175 degrees Fahrenheit (80 deg. C.) for 1.5 hours, and then heating to 275 degrees Fahrenheit (135 deg. C.) for 45 minutes.
After pothead connector
22
is cooled, a sealing boot (not shown) is secured around a lower lip of base
38
and provides a seal between base
38
and the housing of electric motor
16
of pump
12
. After being connected to motor
16
, dielectric oil is pumped into motor
16
. The oil migrates around pin
50
into bore
72
, and up against seal
44
. This eliminates void spaces that could later cause problems due to high pressure differential between the exterior of connector
22
and the internal spaces in connector
22
. In use, the dielectric oil is maintained at a pressure equal to the external hydrostatic pressure by a pressure equalizer.
The present invention has several advantages over prior art electric submersible pumps having pothead connectors in hostile service applications. The base design allows filling of all voids with a dielectric fluid.
The seal
44
seals between the housing and the conductor insulation, encasing the electrical conductors, providing a seal which is impervious to liquid and gas leakage. The epoxy layer stabilizes the conductors so that they are fixed in place and physically contained to protect the electrical insulation against decompression damage.
Although the invention has been described with reference to a specific embodiment, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiment as well as alternative embodiments of the invention will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that the appended claims will cover any such modifications or embodiments that fall within the true scope of the invention.
Claims
- 1. A device for attaching an end of an electric cable to the head of a motor, the electric cable having at least one conductor, the device comprising in combination:a housing; an upper insulating block, contained within the housing, having at least one bore therethrough for receiving a conductor; a lower insulating block, contained within the housing, having at least one bore therethrough for receiving the conductor, and wherein the bores of the upper insulating block and the lower insulating block share the same axis; a seal assembly of an elastomeric material, contained within the housing between the blocks, having at least one passage sharing the same axis as the bores of the upper and lower insulating blocks, the seal assembly having at least one inner lip that while in an undeformed condition has an inner surface that tapers radially inward relative to the axis of the bores of the upper and lower insulating blocks for sealing around the conductor, the seal assembly having an outer periphery that seals against the housing.
- 2. The device of claim 1, wherein the outer periphery of the seal assembly comprises an outer lip encircling and sealing between an outer portion of one of the blocks and the housing, the outer lip, while in an undeformed condition, having an outer surface tapering radially outward relative to an axis of the housing.
- 3. The device of claim 1, wherein the inner surface of the inner lip is cylindrical when installed and sealing against the conductor.
- 4. The device of claim 1, wherein each of the bores of the upper and lower insulation blocks has a cylindrical counterbore of enlarged diameter and the inner lip extends into the counterbore of said one of the bores.
- 5. The device of claim 1, wherein said at least one inner lip comprises first and second inner lips facing in opposite directions, the first inner lip extending into the bore of the upper insulating block, the second one of the inner lips extending into the lower insulating block.
- 6. The device of claim 2, wherein the inner lip and the outer lip are joined by a central web.
- 7. The device of claim 1, wherein the outer periphery of the seal assembly comprises a first outer lip encircling and sealing between an outer portion of the upper insulating block and the housing and a second outer lip encircling and sealing between an outer portion of the lower insulating block and the housing, each of the first and second outer lips having an outer surface tapering radially outward while in an undeformed condition relative to an axis of the housing.
- 8. The device of claim 7, wherein said at least one inner lip comprises first and second inner lips, the first inner lip extending into the bore of the upper insulating block, the second inner lip extending into the bore of the lower insulating block, and said inner lips and said outer lips join at a central web.
- 9. In a power cable for supplying power to a downhole electric motor of a well pump, the power cable having a plurality of electrical insulated conductors, a connector for interconnecting each insulated conductor to an electrical connection of the motor, the connector comprising:a housing; an upper insulating block, contained within the housing, having a plurality of bores therethrough, each of the bores for receiving one of the conductors; a lower insulating block, contained within the housing, having a plurality of bores therethrough, each of the bores of the lower insulating block for receiving one of the conductors, each of the bores of the upper insulating block aligning with one of the bores of the lower insulating block, the insulating blocks having cylindrical outer wall portions spaced radially inward from the housing; an inner lip seal sealing around each of the conductors, having an inner upper lip that extends into one of the bores of the upper insulating block and an inner lower lip that extends into one of the bores of the lower insulating blocks, each of the inner upper and lower lips having an inner surface that tapers radially inward, while in an undeformed condition, relative to the an axis of the bore into which each of the inner upper and lower lips extend; and an outer lip seal having an outer upper lip that is between the cylindrical wall portion of the upper insulating block and the housing and an outer lower lip that is between the cylindrical wall portion of the lower insulating block and the housing, each of the outer upper and lower lips having an outer surface tapering radially outward, while in an undeformed condition, relative to an axis of the housing, and when installed sealing against the housing.
- 10. The connection of claim 9, wherein the inner surfaces of each of the inner upper and lower lips and the outer surface of each of the outer upper and lower lips are cylindrical when installed.
- 11. The connection of claim 9, wherein each of the insulation blocks has an enlarged outer diameter portion that is closely received by the housing.
- 12. The connection of claim 9, wherein said inner lip seals and said outer lip seals join at a central web.
- 13. The connection of claim 9, wherein the housing comprises a base portion that contains the upper and lower blocks and a cap portion, and wherein the cap portion of the housing is epoxy filled.
- 14. In a power cable for supplying power to a downhole electric motor of a well pump, the power cable having a plurality of electrical insulated conductors, a connector for interconnecting each insulated conductor to an electrical connection of the motor, the connector comprising:a housing; an upper insulating block, contained within the housing, having a plurality of bores therethrough, each of the bores for receiving one of the conductors; a lower insulating block, contained within the housing, having a plurality of bores therethrough, each of the bores of the lower insulating block for receiving one of the conductors, each of the bores of the upper insulating block aligning with one of the bores of the lower insulating block, the insulating blocks having cylindrical outer wall portions spaced radially inward from the housing; an inner lip seal sealing around each of the conductors, having an upper lip that extends into one of the bores of the upper insulating block and a lower lip that extends into one of the bores of the lower insulating blocks; an outer lip seal having an upper lip that seals to the housing between the cylindrical wall portion of the upper insulating block and the housing and a lower lip seal that seals to the housing between the cylindrical wall portion of the lower insulating block and the housing; and wherein each of the bores has a counterbore of enlarged diameter and each of upper and lower lips of each of the inner lip seals extends into the counterbore of said one of the bores.
- 15. The connection of claim 14, wherein each of the counterbores of the upper and lower insulating blocks is cylindrical.
- 16. In a power cable for supplying power to a downhole electric motor of a well pump, the power cable having a plurality of electrical insulated conductors, a connector for interconnecting each insulated conductor to an electrical connection of the motor, the connector comprising:a housing having a shoulder at the upper end and a shoulder at the lower end; an upper insulating block, contained within and resting on the shoulder at the upper end of the housing and having an enlarged outer diameter portion that is closely received by the housing, the upper insulating block having a plurality of bores therethrough, each of the bores for receiving one of the conductors and having a counterbore of enlarged diameter; a lower insulating block, contained within and resting on the shoulder at the lower end of the housing and having an enlarged outer diameter portion that is closely received by the housing, the lower insulating block having a plurality of bores therethrough, each of the bores of the lower insulating block for receiving one of the conductors and having a counterbore of enlarged diameter, each of the bores of the upper insulating block aligning with one of the bores of the lower insulating block; an inner lip seal, conical in an undeformed condition and cylindrical when installed, sealing around each of the conductors, having an upper lip that extends into one of the counterbores of the upper insulating block and a lower lip that extends into one of the counterbores of the lower insulating block; an outer lip seal, conical in an undeformed condition and cylindrical when installed, having an upper lip that seals to the housing between the cylindrical wall portion of the upper insulating block and the housing and a lower lip seal that seals to the housing between the cylindrical wall portion of the lower insulating block and the housing.
- 17. The connection of claim 16, wherein said inner lip seals and said outer lip seals join at a central web.
- 18. The connection of claim 16, wherein the housing comprises a base portion that contains the upper and lower blocks and a cap portion, and wherein the cap portion of the housing is epoxy filled.
US Referenced Citations (12)