SUBMERSIBLE PUMP UNIT DRIVE HEAT EXCHANGER HAVING A DIAPHRAGM COMPENSATOR

Abstract

A drive of a submersible pump having a housing, an oil-filled electric motor, a heat exchanger and a compensator hydraulically connected by an oil channel to the oil-filled cavity of the electric motor. The drive has channels to circulate oil in the drive for heat exchange between the oil and the well fluid. Inside the heat exchanger, there is a through channel of the heat exchanger for the well fluid flow. The compensator has a diaphragm placed in a cylindrical casing adjoining an outer side surface of the diaphragm to an inner side surface of the cylindrical casing. The through channel of the heat exchanger for the well fluid flow has an annular cross-section with an inner wall formed by the outer side surface of the cylindrical casing and with an outer wall formed by an inner surface of the cylindrical sleeve of the heat exchanger.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application claims priority from U.S. provisional patent application Ser. No. 63/283,343 filed on 26 Nov. 2021 by Anton Shakirov, et al. and entitled Submersible Pump Unit Drive with Heat Exchanger, which is hereby incorporated by reference in its entirety. This patent application claims priority from U.S. patent application Ser. No. 17/717,889 filed on Apr. 11, 2022 entitled A METHOD AND APPARATUS FOR A SUBMERSIBLE MULTISTAGE LABYRINTH-SCREW PUMP, which is hereby incorporated by reference herein in its entirety. This patent application also claims priority from U.S. Provisional patent application Ser. No. 63/298,734 by ANTON Shakirov entitled A METHOD AND APPARATUS FOR A SUBMERSIBLE MULTISTAGE LABYRINTH-SCREW PUMP filed on Jan. 12, 2022, which is hereby incorporated by reference herein in its entirety; this patent application also claims priority from U.S. Provisional patent application Ser. No. 63/283,340 by ANTON Shakirov entitled Submersible Oil-filled Permanent Magnet Electric Motor, filed on 26 Nov. 2021, which is hereby incorporated by reference herein in its entirety; this patent application also claims priority from U.S. Provisional patent application Ser. No. 63/283,342 by ANTON Shakirov entitled Axial Support Shoe Unit of Oil-Filled Submersible Motor filed on 26 Nov. 2021, which is hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

Downhole high-speed submersible centrifugal pumps are capable of operating in conditions where both the pumping mechanical section with stages and the drive part with an electric motor (oil-filled type) are completely submerged to a great depth in the well. Such pumps have to work for a long time without maintenance. To do this, in such pumps, the drive part with an electric motor is made with a heat exchanger and hydraulic protection, consisting of a protector and a compensator. Hydraulic protection is designed to protect submersible oil-filled electric motors from the penetration of well fluid into their internal cavity, as well as to compensate for oil leakage and thermal changes in its volume during the operation of the electric motor. For the drive part, it is also necessary to ensure the removal of a significant amount of heat, which is formed as a result of mechanical and electrical losses in the electric drive of the pump. For this, a dielectric coolant (dielectric oil) is used, which circulates in an electric motor with a heat exchanger. The coolant absorbs heat from the electric motor and transfers the heat from the electric motor to the surrounding fluid in the well. Design solutions for the pump drive, which ensure efficient heat removal from electric motors during the operation of the pumping unit in the well, reduce the likelihood of drive failure, and, accordingly, increase the operating life of the pumping unit as a whole. An increase in the service life of a pumping unit is one of the main factors ensuring the stability of oil production and reducing the cost of servicing the well stock.

Patent RU No. 2 464 691, published on Oct. 20, 2012 discloses an electric motor (oil-filled type—with a dielectric liquid (oil)) and a heat exchanger with a compensator installed in the heat exchanger. The heat exchanger of the electric motor is combined with the compensator in such a way that the piston of the compensator is located inside the separating body of the heat exchanger with a hot zone, formed by channels for the passage of hot oil from the oil-filled electric motor. The disadvantage of this technical solution provided by RU No. 2 464 691 is the insufficient efficiency of the heat exchanger, in particular, due to the presence of only one heat exchange circuit. The disadvantage is the low efficiency of heat exchange between the electric motor oil being cooled and the cooling well fluid due to the relatively small area of the heat exchange surface over which these fluids flow. As a result, in order to cool the electric motor oil to a temperature acceptable from the point of view of reliable operation of the electric motor, the heat exchanger in this design requires a significant length. In addition, the piston-type compensator has relatively higher breakaway friction losses (when its internal volume changes with hot oil), which can lead to significant pressure drops between the outer and inner cavities of the moving rings. In addition, in the RU No. 2 464 691 design, the compensator (piston) with elastomeric sealing rings does not have sufficient thermal protection and is close enough to the hot flow zone (with oil)—that this proximity to the hot flow zone leads to an increase in the likelihood of thermal damage to the compensator (in particular, its part made of elastomeric rings).

FIELD OF THE INVENTION

A particular illustrative embodiment of the invention relates to equipment for oil production and can be used in downhole multistage centrifugal pumps with high-speed drives, built on the basis of an oil-filled electric motor with a heat exchanger, hydraulic protection, and a compensator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a side view of a schematic representation of a drive submersible pumping unit with a heat exchanger located in the well; and

FIG. 2 depicts a side view of a schematic representation of a heat exchanger with an installed diaphragm compensator.

SUMMARY OF THE INVENTION

A drive of a submersible pump having a housing, an oil-filled electric motor, a heat exchanger and a compensator hydraulically connected by an oil channel to the oil-filled cavity of the electric motor. The drive has channels to circulate oil in the drive for heat exchange between the oil and the well fluid. Inside the heat exchanger, there is a through channel of the heat exchanger for the well fluid flow. The compensator has a diaphragm placed in a cylindrical casing adjoining the outer side surface of the diaphragm to the inner side surface of the cylindrical casing. The through channel of the heat exchanger for the well fluid flow has an annular cross-section with an inner wall formed by the outer side surface of the above cylindrical casing and with an outer wall formed by the inner surface of the cylindrical sleeve of the heat exchanger.

DETAILED DESCRIPTION OF AN ILLUSTRATIVE EMBODIMENT OF THE INVENTION

The specification and drawings are to be regarded in an illustrative rather than a restrictive sense. It will be evident that additions, subtractions, deletions, and other modifications and changes may be made thereunto without departing from the broader spirit and scope of the inventions as set forth in the claims set forth below. Accordingly, the inventions are therefore to be limited only by the scope of the appended claims. None of the claim language should be interpreted pursuant to 35 U.S.C. 112(f) unless the word “means” is recited in any of the claim language, and then only with respect to any recited “means” limitation. The drawings are drawn to scale.

In a particular illustrative embodiment of the invention, a submersible pump unit drive with a heat exchanger is disclosed. In a particular illustrative embodiment of the invention, the submersible pump unit drive with heat exchanger improves the design of a drive of a submersible pumping unit with an oil-filled electric motor and a heat exchanger, which is used in borehole multistage centrifugal pumps. This improvement is aimed at improving the reliability of the pump drive for a longer working life duration and is especially important for high-speed submersible pumping units with a valve drive operating at great depths with a high temperature of the well fluid.

In a particular illustrative embodiment of the invention, the invention increases the service life of an electric drive with a heat exchanger by increasing the efficiency of heat removal from an oil-filled drive motor while reducing the likelihood of thermal damage to the compensator (especially its elastomeric elements) associated with prolonged thermal high-temperature exposure to it. An additional advantage of this technical solution is the possibility of reducing the length of the drive by increasing the compactness of the heat exchanger (reducing the length of the heat exchanger) while reducing the likelihood of thermal damage to the compensator.

To achieve the claimed technical result in a known drive of a submersible pumping unit with a heat exchanger containing a housing, an oil-filled electric motor, a heat exchanger attached to it, located below the electric motor, a compensator installed in the heat exchanger and hydraulically connected by an oil channel with an oil-filled cavity of the electric motor, channels providing oil circulation in the drive for heat exchange between oil and well fluid, a through channel of the heat exchanger is provided inside of the heat exchanger for the flow of well fluid. The heat exchanger has an inlet for the flow of well fluid from the annulus into the heat exchanger and an outlet for the flow of the well fluid out of the heat exchanger and into the annulus. The inlet and outlet of the heat exchanger are provided respectively in the lower and upper parts of the heat exchanger. In a particular illustrative embodiment of the invention, the compensator has a diaphragm made of elastomeric material, which is placed in a cylindrical casing made of heat-conducting material adjoining the outer side surface of the diaphragm to a corresponding inner side surface of the cylindrical casing.

The above through channel of the heat exchanger for the flow of well fluid is a channel of an annular cross-section with an inner wall formed by an outside surface of the above cylindrical casing and with an outer wall formed by the inside surface of the cylindrical sleeve of the heat exchanger. The heat exchanger comprises a circulation channel for oil from the electric motor for heat exchange between oil and well fluid, formed between the outer surface of the heat exchanger sleeve and the inner surface of the heat exchanger housing. In a particular illustrative embodiment of the invention, the diaphragm is made in the form of a two-bag diaphragm, and the heat exchanger has lower and upper flanges, in which the inlet and outlet of the through channel of the inner contour of the heat exchanger for the well fluid flow are made, respectively.

Turning now to FIG. 1, in a particular illustrative embodiment of the invention, a drive of a submersible pumping unit with a heat exchanger contains an electric motor 1 filled with a dielectric liquid (protector (not specified)) is located above the electric motor), a heat exchanger 2 attached to the electric motor from below with a built-in compensator 12. The drive is placed in the well (see FIG. 1) and surrounded downhole fluid in the annulus 36 (a predominantly annular space between the outer surface of the submersible part of the pumping unit and the walls of the well).

A double-circuit heat exchanger with a compensator is attached to the power section (electric motor section) using a mounting flange 3 to the power section, studs 5, nuts 6. The double-circuit heat exchanger (also referred to as “heat exchanger” in the description of an illustrative embodiment of the invention) contains oil channels 25, 26 separated by a bushing 4. The double-circuit heat exchanger 2 with a compensator contains an upper flange 7, a lower flange 16, a body 8, and a heat exchanger sleeve 10. Sleeve 10 can be made of metal with a helical wire winding of its outer surface to intensify heat exchange processes—if its outer surface forms part of the surface of the oil channel (with flow direction 24).

In a particular illustrative embodiment of the invention, a compensator with a compensator diaphragm in the form of a first bag (diaphragm) 12 and a second bag (diaphragm) 40 is attached using bushings 9, 14 and 27 and sleeves 11. The compensator diaphragm is elongated in the vertical direction and is preferably made of an elastomeric material. The outer surface of the compensator is limited by a rigid cylindrical casing 13 made of a heat-conducting material (usually made of metal) mounted on a mount 15. In the flanges 7 and 16, oil inlet and outlet sections (also referred to herein as “channels”) 19 and 20 are provided for providing a circulation channel for oil thereby enabling a circulation flow in the direction of the oil flow 24 (downward) of a motor for heat exchange between oil and well fluid formed between the outer surface of the heat exchanger sleeve 10 and the inner surface of the heat exchanger body 8. Such a passage preferably has an annular cross-section.

Also, in the flanges 7 and 16 an outlet channel opening and an inlet channel opening are provided for supplying fluid output to the through channel for the well fluid in the heat exchanger, respectively, for the flow of the well fluid 17 and 18 (the outlet and inlet of the well fluid flow from the annulus 36). The direction of the well fluid flows is indicated by arrows 21, 22, the direction of the oil flows 23 and 24. Rubber rings 28, 29, 30, 31, 32 and 33 are provided to seal the internal cavity of the electric motor and rings 35 are used to separate the oil flows.

In a particular illustrative embodiment of the invention, the device works as follows. The oil in the motor absorbs the heat from the running motor and conducts the absorbed heat to the well fluid. Oil flows through the electric motor and the heat exchanger. Namely, oil (dielectric coolant) from the motor circulates through channels (oil lines) circulating oil in the drive for heat exchange between oil and well fluid (for example, an oil circulating pump). The oil circulation is ensured, in particular, by an inlet channel 19 connected to the oil-filled cavity of the engine and ensuring the flow of oil into the annular channel for oil circulation in the direction 24 through the heat exchanger. Oil channel 26 also provides the operation of a compensator with a diaphragm containing additional dielectric oil in its internal cavity to compensate for the thermal expansion of oil in the motor cavity (and to compensate for the inevitable oil leakage from the oil-filled zone of the electric motor).

In the through channel of the heat exchanger (part of the internal contour of the heat exchanger) for the flow of well fluid through the inlet 18 (channel in the flange), well fluid from the annulus with well fluid 36 enters. With a wall formed by the outer side surface of the cylindrical casing 13 and with an outer wall formed by the inner surface of the cylindrical sleeve of the heat exchanger 10. This flow simultaneously provides: cooling of the compensator with first bag (diaphragm) 12 (through a thin-walled (for example, less than 2 mm thick) cylindrical steel casing 13), and a second bag or diaphragm 40, wherein such cooling prolongs the life of the diaphragm compensator.

In a particular illustrative embodiment of the invention, the diaphragm is made of an elastomeric material (rubber type), creating a more favorable temperature regime for the diaphragm. Thermal insulation of the compensator from the hot zone is provided by the circulation channel for oil from the electric motor for heat exchange between oil from the electric motor and the well fluid, formed between the outer surface of the heat exchanger sleeve 10 and the inner surface of the heat exchanger housing 8, which also creates a more favorable temperature regime for the diaphragm—primarily for its elastomeric elements (bag (diaphragm)). A particular illustrative embodiment of the invention contributes to the cooling of the above oil circulation path (with flow 24) from the electric motor for heat exchange between the oil and the well fluid.

In a particular illustrative embodiment of the invention, the creation of such a second (internal) circuit with a through channel for the flow of well fluid in the heat exchanger) can increase the heat exchange surface by almost 2 times while maintaining the length of the heat exchanger.

In a primary (outer) loop, the passing oil flow in direction 24 in the oil circulation path from the electric motor for heat exchange between oil and well fluid (formed between the sleeve and the heat exchanger housing) is also cooled by the well fluid flow in the annulus in direction 21 (i.e. in the opposite direction to the well fluid flow).

In a particular illustrative embodiment of the invention, location of the motor heat exchanger below the motor may be advantageous when the pumping unit is located in the wellbore above the zone of perforations (′perforations' may be provided in the casing at desired locations to allow formation fluids to enter the casing). With this arrangement, the fluid drawn into the wellbore passes, in particular, over the outside of the heat exchanger before it is heated by the engine. This contributes to the more efficient operation of the heat exchanger.

In a particular illustrative embodiment of the invention, the term “forced cooling system” refers to the double-circuit heat exchangers (also referred to herein as heat exchanger having a “two-bag” or “double-bag” diaphragm compensator) described herein and is preferred because of the small size of the power unit and intense heat generation within it. In such a system, an efficient heat exchanger and the creation of an intensive circulation of flows (oil and well fluid) through it are always preferred. Since this design reduces the amount of oil (when using a single bag compensator 12) that heats up and expands when the motor is running, a larger oil volume compensator (double bag (diaphragm) compensator, a first bag (diaphragm) 12 and a second bag (diaphragm) 40) is preferred. Therefore, it is highly desirable to make the compensator as a two-bag compensator, in which the design of the connection of the bags provides for the minimum size of the product.

In a particular illustrative embodiment of the invention, a double-circuit heat exchanger with a compensator is made of pipes with a calculated length corresponding to a required cooling of the power unit or motor when operating in the nominal mode. All the main structural elements of the heat exchanger, except for the compensator diaphragm, in particular, the lower 16 and upper flanges 7, the cylindrical casing 13, the cylindrical sleeve of the heat exchanger 10, the cylindrical casing 8 can be made of steel—in particular, carbon steel or (for corrosion-resistant design) stainless steel.

In a particular illustrative embodiment of the invention, the typical thickness of the cylindrical sleeve 10 is from 2 mm to 6.5 mm, the typical thickness of the cylindrical casing 13 is from—0.5 to 2 mm, the typical thickness of the housing 8—from 4 to 7 mm. The range of outside diameters of the housing 8 is for example, from 103 mm to 185 mm. Diameters of input and output channels 7.18— from 3 to 15 mm. The typical thickness range of the oil pipeline flow channel is from 1.5 to 3 mm.

The location of the motor heat exchanger below the motor may be advantageous in applications where the pumping unit is located in the wellbore above the zone of perforations (′perforations' may be provided in the casing at desired locations to allow formation fluids to enter the casing). With this arrangement, the fluid drawn into the wellbore passes, in particular, over the outside of the heat exchanger before it is heated by the motor. In a particular illustrative embodiment of the invention, a water protector is placed above the motor. In other cases, the use of the use of forced flow casing is preferred.

In a particular illustrative embodiment of the invention, a submersible pump unit drive with heat exchanger is disclosed, comprising a housing; an oil-filled electric motor contained in the housing; a heat exchanger connected to the electric motor and located below the electric motor; a compensator installed in the heat exchanger; an oil channel hydraulically connected with an oil-filled cavity in the electric motor, wherein the oil channel provides oil circulation in the electric motor for heat exchange between oil and well fluid; a through channel inside of the heat exchanger for flow of well fluid through the heat exchanger, wherein the through channel has an inlet for flow of well fluid from an annulus and an outlet for the flow of well fluid into the annulus, wherein the inlet and the outlet are made in an lower and upper parts of the heat exchanger respectively; a diaphragm made of elastomeric material, which is placed in a cylindrical casing adjoining an outer side surface of the diaphragm to a corresponding inside surface of an outside surface of the cylindrical casing; and a cylindrical sleeve surrounding the cylindrical casing of the heat exchanger wherein the through channel of the heat exchanger for the flow of the well fluid is a channel of an annular cross section with an inner wall formed by an outer surface of the cylindrical casing and with an outer wall formed by an inner surface of the cylindrical sleeve of the heat exchanger, while the heat exchanger contains a circulation channel for oil from the electric motor for heat exchange between oil and well fluid, formed between the outer surface of the heat exchanger sleeve and the inner surface of the heat exchanger housing.

In another particular illustrative embodiment of the invention the diaphragm further comprises a two-bag diaphragm, and wherein the heat exchanger has lower and upper flanges, in which the inlet and outlet of the through channel of the heat exchanger are made, respectively, for the flow of well fluid, wherein the two-bag diaphragm is placed in a cylindrical casing between a first flange and a second flange. In a particular illustrative embodiment of the invention, a submersible pump unit drive with a heat exchanger is disclosed, comprising a housing; an oil-filled electric motor contained in the housing; a heat exchanger connected to the electric motor and located below the electric motor; a compensator installed in the heat exchanger; an oil channel hydraulically connected with an oil-filled cavity in the electric motor, wherein the oil channel provides oil circulation in the electric motor for heat exchange between the oil in oil-filled cavity in the electric motor and well fluid; and a through channel inside of the heat exchanger for a flow of the well fluid through the heat exchanger, wherein the through channel has an inlet for flow of well fluid from an annulus and an outlet for the flow of well fluid into the annulus, wherein the inlet and the outlet are made in a lower and upper part of the heat exchanger respectively.

In another particular illustrative embodiment of the invention the submersible pump unit drive further comprises a two-bag diaphragm made of elastomeric material, which is placed in a cylindrical casing adjoining an outer side surface of the diaphragm to a corresponding inside surface of an outside surface of the cylindrical casing.

In another particular illustrative embodiment of the invention the submersible pump unit drive further comprises, a cylindrical sleeve surrounding the cylindrical casing of the heat exchanger wherein the through channel of the heat exchanger for the flow of the well fluid is a channel of an annular cross section with an inner wall formed by an outer surface of the cylindrical casing and with an outer wall formed by an inner surface of the cylindrical sleeve of the heat exchanger, while the heat exchanger contains a circulation channel for oil from the electric motor for heat exchange between oil and well fluid, formed between an outer surface of the heat exchanger cylindrical sleeve and the inner surface of the heat exchanger housing.

In another particular illustrative embodiment of the invention the submersible pump unit drive further comprises a method for cooling a submersible pump unit drive, the method comprising circulating oil in an oil-filled electric motor contained in a submersible pump unit drive through an oil channel hydraulically connected with an oil-filled cavity in the electric motor, wherein the oil channel provides oil circulation in the electric motor between the electric motor and a heat exchanger for heat exchange between the oil and a well fluid.

In another particular illustrative embodiment of the invention the method for cooling a submersible pump unit drive further comprises, flowing well fluid through channel inside of the heat exchanger for flow of well fluid through the heat exchanger, wherein the through channel has an inlet for flow of well fluid from an annulus and an outlet for the flow of well fluid into the annulus, wherein the inlet and the outlet are made in a lower and upper part of the heat exchanger respectively.

In another particular illustrative embodiment of the invention the method for cooling a submersible pump unit drive, a first diaphragm made of elastomeric material, which is placed in a cylindrical casing adjoining an outer side surface of the diaphragm to a corresponding inside surface of an outside surface of the cylindrical casing.

In another particular illustrative embodiment of the invention the method for cooling a submersible pump unit drive, a cylindrical sleeve surrounding the cylindrical casing of the heat exchanger wherein the through channel of the heat exchanger for a flow of the well fluid is a channel of an annular cross section with an inner wall formed by an outer surface of the cylindrical casing and with an outer wall formed by an inner surface of the cylindrical sleeve of the heat exchanger, while the heat exchanger contains a circulation channel for oil from the electric motor for heat exchange between oil and well fluid, formed between the outer surface of the heat exchanger sleeve and the inner surface of a heat exchanger housing.

In another particular illustrative embodiment of the invention the method for cooling a submersible pump unit drive, a second diaphragm made of elastomeric material, is placed in a cylindrical casing adjoining an outer side surface of the diaphragm to a corresponding inside surface of an outside surface of a cylindrical casing.

In a particular illustrative embodiment of the invention, the drive with the specified heat exchanger provides an increase in heat transfer. It provides an increased rate of heat transfer along the internal contour. The use of an electric drive of a submersible pump with such a heat exchanger provides an increase in the compactness of the heat exchanger for a submersible oil-filled electric motor and effective maintenance of a given operating temperature range of an oil-filled electric motor, which ultimately prolongs the service life of the pumping unit.

Claims

1. A submersible pump unit drive with heat exchanger, comprising:

a housing;

an oil-filled electric motor contained in the housing;

a heat exchanger connected to the electric motor and located below the electric motor;

a compensator installed in the heat exchanger;

an oil channel hydraulically connected with an oil-filled cavity in the electric motor, wherein the oil channel provides oil circulation in the electric motor for heat exchange between oil and well fluid;

a through channel inside of the heat exchanger for flow of well fluid through the heat exchanger, wherein the through channel has an inlet for flow of well fluid from an annulus and an outlet for the flow of well fluid into the annulus, wherein the inlet and the outlet are made in an lower and upper parts of the heat exchanger respectively.

2. The submersible pump unit drive with heat exchanger of claim 1, further comprising:

a diaphragm made of elastomeric material, which is placed in a cylindrical casing adjoining an outer side surface of the diaphragm to a corresponding inside surface of an outside surface of the cylindrical casing.

3. The submersible pump unit drive with heat exchanger of claim 2, further comprising:

a cylindrical sleeve surrounding the cylindrical casing of the heat exchanger wherein the through channel of the heat exchanger for the flow of the well fluid is a channel of an annular cross section with an inner wall formed by an outer surface of the cylindrical casing and with an outer wall formed by an inner surface of the cylindrical sleeve of the heat exchanger, while the heat exchanger contains a circulation channel for oil from the electric motor for heat exchange between oil and well fluid, formed between the outer surface of the heat exchanger sleeve and the inner surface of the heat exchanger housing.

4. The submersible pump unit drive of claim 3, wherein the diaphragm further comprises a two-bag diaphragm, and wherein the heat exchanger has lower and upper flanges, in which the inlet and outlet of the through channel of the heat exchanger are made, respectively, for the flow of well fluid, wherein the two-bag diaphragm is placed in a cylindrical casing between a first flange and a second flange.

5. A submersible pump unit drive with a heat exchanger, comprising:

a housing;

an oil-filled electric motor contained in the housing;

a heat exchanger connected to the electric motor and located below the electric motor;

a compensator installed in the heat exchanger;

an oil channel hydraulically connected with an oil-filled cavity in the electric motor, wherein the oil channel provides oil circulation in the electric motor for heat exchange between the oil in oil-filled cavity in the electric motor and well fluid; and

a through channel inside of the heat exchanger for a flow of the well fluid through the heat exchanger, wherein the through channel has an inlet for flow of well fluid from an annulus and an outlet for the flow of well fluid into the annulus, wherein the inlet and the outlet are made in a lower and upper part of the heat exchanger respectively.

6. The submersible pump unit drive of claim 5, further comprising:

a two-bag diaphragm made of elastomeric material, which is placed in a cylindrical casing adjoining an outer side surface of the diaphragm to a corresponding inside surface of an outside surface of the cylindrical casing.

7. The submersible pump unit drive of claim 6, further comprising:

a cylindrical sleeve surrounding the cylindrical casing of the heat exchanger wherein the through channel of the heat exchanger for the flow of the well fluid is a channel of an annular cross section with an inner wall formed by an outer surface of the cylindrical casing and with an outer wall formed by an inner surface of the cylindrical sleeve of the heat exchanger, while the heat exchanger contains a circulation channel for oil from the electric motor for heat exchange between oil and well fluid, formed between an outer surface of the heat exchanger cylindrical sleeve and the inner surface of the heat exchanger housing.

8. A method for cooling a submersible pump unit drive, the method comprising:

circulating oil in an oil-filled electric motor contained in a submersible pump unit drive through an oil channel hydraulically connected with an oil-filled cavity in the electric motor, wherein the oil channel provides oil circulation in the electric motor between the electric motor and a heat exchanger for heat exchange between the oil and a well fluid.

9. The method of claim 8, the method further comprising:

flowing well fluid through channel inside of the heat exchanger for flow of well fluid through the heat exchanger, wherein the through channel has an inlet for flow of well fluid from an annulus and an outlet for the flow of well fluid into the annulus, wherein the inlet and the outlet are made in a lower and upper part of the heat exchanger respectively.

10. The method of claim 9, wherein a first diaphragm made of elastomeric material, which is placed in a cylindrical casing adjoining an outer side surface of the diaphragm to a corresponding inside surface of an outside surface of the cylindrical casing.

11. The method of claim 10, wherein a cylindrical sleeve surrounding the cylindrical casing of the heat exchanger wherein the through channel of the heat exchanger for a flow of the well fluid is a channel of an annular cross section with an inner wall formed by an outer surface of the cylindrical casing and with an outer wall formed by an inner surface of the cylindrical sleeve of the heat exchanger, while the heat exchanger contains a circulation channel for oil from the electric motor for heat exchange between oil and well fluid, formed between the outer surface of the heat exchanger sleeve and the inner surface of a heat exchanger housing.

12. The method of claim 11 wherein a second diaphragm made of elastomeric material, is placed in a cylindrical casing adjoining an outer side surface of the diaphragm to a corresponding inside surface of an outside surface of a cylindrical casing.