Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/06—Lubrication
  • F04D29/061—Lubrication especially adapted for liquid pumps
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D13/00—Pumping installations or systems
  • F04D13/02—Units comprising pumps and their driving means
  • F04D13/06—Units comprising pumps and their driving means the pump being electrically driven
  • F04D13/08—Units comprising pumps and their driving means the pump being electrically driven for submerged use
  • F04D13/10—Units comprising pumps and their driving means the pump being electrically driven for submerged use adapted for use in mining bore holes
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/58—Cooling; Heating; Diminishing heat transfer
  • F04D29/5806—Cooling the drive system

Definitions

• This invention relates in general to electrical submersible subsea booster pumping systems, and in particular to reducing the temperature of a subsea submersible electric pump motor through heat exchange with a frame structure having a non-heat exchange related primary function.
• the ESP typically has at least one electrical motor that normally is a three-phase, AC motor.
• the motor drives a centrifugal pump that may contain a plurality of stages, with each stage comprising an impeller and a diffuser that increases the pressure of the well fluid.
• the motor has a housing that is filled with a dielectric lubricant or oil that both provides lubrication and aids in the removal of heat from the motor during operation of the ESP.
• a seal section is typically located between the pump and the motor for equalizing the pressure of the lubricant contained within the motor with the hydrostatic pressure of the well fluid on the exterior.
• the ESP is typically run within the well with a workover rig.
• the ESP is run on the lower end of a string of production tubing. Once in place, the ESP may be energized to begin producing well fluid that is discharged into the production string for pumping to the surface.
• One of the most important properties of the motor oil is to lubricate the bearings and thrust bearing of the motor.
• the oil is also generally vital in dissipating heat from the bearings and thrust bearings in order to help maintain the motor within its rated temperature, and thus maintain motor reliability. Rejection of heat from the oil to the surrounding well fluid, however, is usually limited due to the well fluid's high temperature, and also its poor heat transfer characteristics due to its high viscosity.
• the heat from the oil is rejected to the seawater and the cooled oil is reintroduced to the motor via a cooled oil line that communicates with the seal section.
• the heat exchanger arrangement reduces the temperature of an ESP motor, thus allowing the motor to operate longer and more reliably.
• various embodiments of the present invention advantageously provide systems and methods for cooling a motor of an electrical submersible pump (ESP) assembly employed in an electrical submersible subsea booster pumping system by cooling the motor lubricant that does not require the addition of an independent external heat exchange unit.
• ESP electrical submersible pump
• various embodiments of the present invention utilize a subsea supporting frame structures having a different or unrelated primary function, such as, for example, an ESP mounting skid or top end assembly of a caisson, modified to also function as a surrogate external heat exchanger to cool oil circulating through a motor of an ESP.
• an example of an embodiment of a system for cooling a motor of an ESP assembly employed in an electrical submersible subsea booster pumping system can comprise an ESP assembly including a subsea ESP having one or more pump stages, a motor, and a seal section located between the one or more pump stages and the motor.
• the motor housing can include a dielectric lubricant outlet port extending through a first portion of the housing and a dielectric lubricant inlet port extending through a second portion of the housing.
• a containment vessel or capsule is positioned about at least major portions of the ESP assembly to contain the ESP.
• the system can also include a subsea supporting frame structure in the form of a modified ESP mounting skid or top-end assembly of a caisson.
• a subsea supporting frame structure in the form of a modified ESP mounting skid or top-end assembly of a caisson.
• Each of a plurality of elongate main structural members of the supporting frame structure have or have been modified or otherwise configured to have a main body containing a fluid conduit formed at least partially, but more typically completely therethrough along a longitudinal axis thereof.
• Each fluid conduit is positioned in fluid communication with at least one other of a plurality of fluid conduits corresponding to the plurality of elongate main structural members to form a closed fluid circuit.
• At least one of the plurality of elongate main structural members include a fluid inlet port in fluid communication with the dielectric lubricant outlet port in the containment vessel of the ESP assembly via a hot or heated lubricating fluid conduit or line either extending therethrough or connected thereto. At least one of the plurality of elongate main structural members also include a fluid outlet port in fluid communication with the dielectric lubricant inlet port in the containment vessel of the ESP assembly via a cold or cooled lubricating fluid conduit or line either extending therethrough or connected thereto.
• the supporting frame includes a plurality of different dielectric lubricant pathways (similar in form to that of a manifold) extending between the fluid inlet and the fluid outlet of the supporting frame structure and through a corresponding different set of one or more of the plurality of fluid conduits defining the pathways.
• the plurality of different dielectric lubricant pathways provided by the supporting frame structure in conjunction with the relatively large exterior surface area and relatively high thermal conductivity of the main structural members, facilitates a transfer of heat energy in the dielectric lubricant circulating through the plurality of different dielectric lubricant pathways to the surrounding seawater.
• heat energy is readily transferred to seawater flowing through the subsea supporting frame structure and across exterior surfaces of the elongate main structural members when the supporting frame structure and ESP assembly are operationally deployed, to thereby reduce temperature of the dielectric lubricant, and thus, the temperature of the motor.
• the system also includes at least one fluid conduit or line extending between the motor housing dielectric lubricant outlet port and the supporting frame structure fluid inlet to thereby form a heated dielectric lubricant discharge pathway therebetween.
• the system further includes at least one fluid conduit extending between the supporting frame structure fluid outlet and the motor housing dielectric lubricant inlet port to thereby form a cooled dielectric lubricant return pathway therebetween.
• a fluid moving device is positioned to circulate the dielectric lubricant for the motor through the heated dielectric lubricant discharge pathway, through the plurality of different dielectric lubricant pathways provided by the supporting frame structure, and through the cooled dielectric lubricant return pathway, to be cooled by the seawater flowing past and through the structural members of the supporting frame structure.
• a total quantity of the dielectric lubricant circulated within the fluid conduits in the elongate main structural members of the supporting frame structure in the form of either an ESP mounting skid or a top-end assembly of a caisson (forming a surrogate heat exchanger) exceed a dielectric lubricant capacity of the dielectric lubricant circulation components contained within the confines of the motor housing, alone, by at least a factor of at least three or four, but more typically by a factor of between about five to ten, to thereby enhance cooling of the motor.
• various embodiments of the present invention also include methods of cooling a motor of an ESP assembly employed in an electrical submersible subsea booster pumping system.
• the method can include the steps of providing a ESP assembly in a vicinity of a sea floor comprising an ESP having a motor and at least one pump housed within a containment vessel, and employing or otherwise providing a subsea supporting frame structure comprising either a mounting skid configured to frame at least major portions of the ESP assembly or a top end assembly of a subsea caisson, as a surrogate heat exchanger. Examples of configurations of the ESP and subsea supporting frame structure configured to provide a closed fluid circuit for cooling motor lubricant were described previously.
• the steps can also include circulating dielectric lubricant from a dielectric lubricant outlet port of the motor housing to a fluid inlet of the supporting frame structure, removing heat from the dielectric lubricant circulating through the plurality of elongate main structural members flowing through a plurality of different pathways between the fluid inlet and a fluid outlet of the supporting frame structure, and circulating the dielectric lubricant from the outlet port of the supporting frame structure to the dielectric lubricant inlet port of the motor housing.
• the heat removal process can be accomplished by transferring heat energy in the dielectric lubricant to seawater naturally flowing through the subsea supporting frame structure and across exterior surfaces of its elongate main structural members to thereby reduce the temperature of the dielectric lubricant.
• the cooled dielectric lubricant When introduced back into the confines of the housing of the motor, the cooled dielectric lubricant then functions to cool internal motor components more effectively.
• the life of the motor is advantageously extended and its reliability is advantageously increased.
• FIG. 1 is a schematic diagram of a system for cooling a motor of an electrical submersible pump (ESP) assembly employed in an electrical submersible subsea booster pumping system according to an embodiment of the present invention
• ESP electrical submersible pump
• FIG. 2 is a perspective view of a top-end assembly of a caisson illustrating the addition of fluid conduits and resulting fluid flow patterns according to an embodiment of the present invention
• FIGS. 3A-3B are a perspective view of a system for cooling a motor of an ESP assembly employed in an electrical submersible subsea booster pumping system according to an embodiment of the present invention
• FIG. 4 is a schematic diagram of a capsule for containing an ESP according to the embodiment of the present invention shown in FIG. 3A;
• FIG. 5 is a schematic diagram of a system for cooling a motor of an ESP assembly employed in an electrical submersible subsea booster pumping system according to an embodiment of the present invention
• FIG. 6 is a schematic diagram illustrating connections and ports adjacent an upper end of an ESP according to the embodiment of the present invention shown in FIG. 5;
• FIG. 7 is a schematic diagram illustrating connections and ports adjacent a lower end of an ESP according to the embodiment of the present invention shown in FIG. 5;
• FIG. 8 is a schematic diagram illustrating connection of an external hot oil line to an upper end of an ESP motor according to the embodiment of the present invention shown in FIG. 5.
• FIGS. 1-8 illustrate various embodiments of a system 30, 30' and methods for cooling the motor of an ESP/pump assembly employed in an electrical submersible subsea booster pumping system, by cooling motor lubricant (e.g., lubricating oil).
• cooling motor lubricant e.g., lubricating oil
• a supporting frame structure such as the top end assembly of a caisson (FIG. 1) or ESP mounting skid (FIG. 3A) having structural members exposed to environmental seawater, is formed/modified to have fluid conduits within the structural members that establish lubricant pathways for lubricant to flow.
• a heated/hot lubricant line (single or multiple conduits) connects between a lubricant inlet port in the supporting frame structure and a lubricant outlet port in the motor housing of the ESP.
• a cooled lubricant line connects between a lubricant outlet port in the supporting frame structure and a lubricant inlet port in the motor housing.
• a pump/thrust bearing/impeller and/or other fluid moving device generally connected adjacent to or within the motor housing circulates the lubricant from within the motor (motor housing) to the lubricant pathways within the supporting frame structure, whereby the seawater passing over external surfaces of the structural members cools the lubricant contained therein.
• the cooled lubricant is then circulated back into the motor (motor housing) to assist in cooling the components of the motor located within the housing, particularly those in direct contact with the motor lubricant.
• FIG. 1 illustrates an example of a system 19 to cool the dielectric lubricant used to lubricate a motor 22 of an ESP 20 to thereby cool the motor 22 of the ESP 20.
• the ESP 20, illustrated in a standard arrangement can be part of a subsea boosting system located on or adjacent a seabed. Note, the ESP 20 may be horizontally mounted, inclined, or vertically mounted within a caisson 21 in the seafloor according to various configurations. It also may be alternatively positioned in an inverted arrangement depending upon the desired direction of flow of the production fluid. Orientation of the ESP 20 within a caisson 21 and various fluid pathway configurations for production fluid is described in more detail, for example, in U.S. Patent Application No. 12/825,141 filed June 28, 2010, titled "Heat Exchanger for ESP Motor.”
• the caisson 21 can be partially or completely submerged in the seabed and can be several hundred feet deep.
• the caisson 21 can be used to separate gas in the production fluid to thereby increase pumping efficiency. In such configuration, the well fluid would flow into the top of the caisson, then down to the open bottom end of the capsule, where it would be pumped upward by the ESP 20.
• the ESP 20 can include a motor 22 and a pump 23 with a seal section 24 located in between.
• the seal section 24 typically contains a thrust bearing and a pressure equalizer (not shown) to equalize the pressure of lubricant in the motor 22 with the hydrostatic pressure within the caisson 21.
• a containment vessel in the form of a shroud or capsule 25 houses the ESP 20 within the fluid collector 26 positioned within a caisson housing 27.
• the capsule 25 has a cap or barrier 32 at one end having a discharge port 33 extending therethrough, and an intake port 36 at the other end.
• the capsule 25 in this example is located on the sea floor and is vertical.
• the cap 32 can have various types of ports and connections depending on the configuration of the ESP 20 within the capsule 25.
• the motor 22 and pump 23 are in the standard position such that the base of the motor 22 faces the intake port 36 end of the capsule 25.
• the motor 22 is located below the pump 23 such that the base of the motor 22 is at the end of the capsule 25 opposite the cap 32 and a seal section 24 is located between the motor 22 and pump 23.
• Production fluid discharge tubing 42 connects to a flow line or riser 43 extending through the discharge port 33 to carry production fluid from a well. That is, in this example, the pump 23 discharges the production fluid through a piece of discharge tubing 42 that passes through the discharge port 33 in the cap 32.
• the discharge tubing 42 can connect to a flow line or riser 43 extending up through a pumped liquid outlet 47 in the top portion of the housing 27 of the caisson 21 to a top and assembly 45 of the caisson 21.
• a power cable 48 runs through an electrical penetrator 50 in the cap 32 and connects to motor 22 to energize it.
• a hot oil conduit or line 51 extends down through a lubricating oil outlet port 53 in the cap 32 and into the capsule 25 and further extends into an oil outlet port 55 in an upper portion of the motor housing 57 to communicate with the top of the motor 22.
• a cooled oil line 52 extends down through lubricating oil inlet port 59 in the cap 32 and into the capsule 25 and further extends into an oil inlet port 61 in a bottom portion of the motor housing 57. In this example, the cooled oil line 52 returns the cooled oil from the top end assembly 45 to the base of the motor 22.
• outlet ports 53, 55 and inlet ports 59, 61 are illustrated according to an exemplary configuration and that other locations can be selected.
• hot oil conduit or line 51 and cooled oil conduit or line 52 are each illustrated as a single conduit, one of ordinary skill in the art would understand that the conduits or lines 51, 52 can be continuous, segmented into multiple separate conduits, or a combination thereof.
• the top end assembly 45 can include a plurality of elongate main structural members 71 having an exterior surface substantially exposed to seawater when positioned in a subsea environment.
• a main body of each of the structural members 71 can be modified to include a fluid conduit 73 formed at least partially therethrough along a longitudinal axis thereof.
• the structural members 71 are in the form of tubes.
• the plurality of fluid conduits 73 and corresponding plurality of elongate main structural members 71 can be connected to form a plurality of different dielectric lubricant pathways 75 between a fluid inlet 77 in one of the members 71 connected to the hot oil conduit or line 51 and an outlet 79 in one of the members 71 connected to the cooled oil conduit or line 52.
• the ESP 20 can be modified to include or is otherwise provided a throw-out bearing, impeller, oil pump and/or other pumping means (collectively “oil pump”) 63 having sufficient pressure to circulate the lubricating oil in the loop formed by the housing 57 of the motor 22, the hot and cooled oil conduit or lines 51, 52, and the fluid pathways 75 formed within the top end assembly 45.
• oil pump oil pump
• the temperature of the motor oil inside the motor 22 and circulating through the seal section 24 rises. Reducing the temperature of the motor oil to thereby cool the motor 22 advantageously extends the life and increases the reliability of the motor 22. Accordingly, employing the top end assembly 45 as a surrogate heat exchanger located externally to the capsule 25 (or on a skid that supports a capsule similar to capsule 25, described later) can be accomplished to cool the motor oil.
• Portions of the hot oil line 51 pass through the connector/outlet port 53 that passes through the cap 32 to allow the hot oil line 51 to communicate with the top of the motor 22.
• the hot oil line 51 allows hot motor oil from the motor 22 to be circulated to the fluid pathways 75 in the top end assembly 45. Once inside the top end assembly 45, the hot oil is circulated through the fluid conduits 73 of the members 71 externally exposed to the seawater 80. A substantial amount of heat absorbed by the oil from within the motor 22 is thus transferred to the seawater 80 and the cooled oil is reintroduced to the motor 22 via the cooled oil line 52.
• the cooled oil line 52 passes through connector/oil inlet port 59 and through oil inlet port 61 in the housing 57 of the motor 22.
• the oil pump 63 is located inside and at the top end of the motor 22. According to a specific exemplary configuration, the oil pump 63 is driven by a shaft in the motor 22 and circulates the oil in the loop formed by the motor 22, oil conduit or lines 51, 52 and the conduits 73 within the top end unit 45. Further, in this exemplary configuration, due to the overall size of the structural members 71 and the length of the oil conduits or lines 51, 52, the fluid carrying volume of such external components in relation to the volume of the fluid conduits within the motor housing 57 can be on the order of five to ten times greater, or more.
• FIGS. 3A and 3B illustrate an alternate embodiment of the present invention whereby the subsea supporting frame structure providing surrogate heat exchanger functionality comprises an ESP mounting skid 101 positioned in a vicinity of the sea floor.
• FIGS. 3A and 3B illustrate an alternate embodiment of the present invention whereby the subsea supporting frame structure providing surrogate heat exchanger functionality comprises an ESP mounting skid 101 positioned in a vicinity of the sea floor.
• each of the capsules 103 can include both an inline production fluid connection port 111 and a radially oriented production fluid connection port 113 facilitates positioning of the pair of capsules 103 within the confines of the mounting skid 101.
• FIG. 5 illustrates a sectional view of the mounting skid 101 having multiple elongate main structural members 121 directly or indirectly connected to a base 122 and framing a single ESP 20 contained in a capsule or other containment vessel 123 having an in-line production fluid inlet/port 125 and a production fluid discharge outlet/port 127.
• Each of the structural members 121 have an exterior surface substantially exposed to seawater 50.
• a main body of each of a set of the structural members 121 are modified to include a fluid conduit 133 formed therethrough along a longitudinal axis thereof.
• the structural members 121 provided to include the fluid conduits 133 are in the form of tubes.
• the plurality of fluid conduits 133 and corresponding plurality of elongate main structural members 121 can be connected to form a plurality of different dielectric lubricant pathways 135 between a fluid inlet 137 in one of the members 121 connected to the hot oil conduit or line 151, and an outlet 139 in one of the members 121 connected to the cooled oil conduit or line 152.
• the capsule 123 includes an end cap 161 having outlet port 163 that accommodates hot oil conduit or line 151 along with production outlet/port 127, and includes an end cap 167 having inlet port 169 that accommodates cooler oil conduit or line 152 along with production inlet/port 125.
• the hot oil conduit or line 151 extends down from inlet 137 through a lubricating oil outlet port 163 in the end cap 161 and into the capsule 123 and further extends into the oil outlet port 55' in an upper portion of the motor housing 57 to communicate with the top of the motor 22.
• the cooled oil line 152 extends up from outlet 139, through lubricating oil inlet port 169 in the end cap 167 and into the capsule 123 and further extends into an oil inlet port 6 in a bottom portion of the motor housing 57.
• the cooled oil line 152 returns the cooled oil from the lower end of mounting skid 101 to the base of the motor 22.
• outlet ports 55', 139, 163 and inlet ports 6 , 137, 169 are illustrated according to an exemplary configuration and that other locations can be selected.
• hot oil conduit or line 151 and cooled oil conduit or line 152 are each illustrated as a single conduit, one of ordinary skill in the art would understand that the conduits or lines 151, 152 can be continuous, segmented into multiple separate conduits, or a combination thereof.
• the ESP 20 shown in FIG. 5 is modified to include or is otherwise provided various pumping means (collectively "oil pump” 63) having sufficient pressure to circulate the lubricating oil in the loop formed by the housing 57 of the motor 22, the hot and cooled oil conduit or lines labeled 151, 152 in FIGS. 5-8, and the fluid pathways 135 formed within the mounting skid 101.
• oil pump various pumping means having sufficient pressure to circulate the lubricating oil in the loop formed by the housing 57 of the motor 22, the hot and cooled oil conduit or lines labeled 151, 152 in FIGS. 5-8, and the fluid pathways 135 formed within the mounting skid 101.
• the mounting skid 101 modified to include passageways 135 can be employed as a surrogate heat exchanger to cool the motor oil.
• Portions of the hot oil line 151 passes through the connector/outlet port 163 that passes thru the end cap 127 to allow the hot oil line 151 to communicate with the top of the motor 22.
• the hot oil line 151 allows hot motor oil from the motor 22 to be circulated to the fluid pathways 135 in the established in the mounting skid 101.
• the hot oil is circulated through the fluid conduits 133 of the members 121 externally exposed to the seawater 80.
• a substantial amount of heat absorbed by the oil from within the motor 22 is thus transferred to the seawater 80 and the cooled oil is reintroduced to the motor 22 via the cooled oil line 152.
• the cooled oil line 152 passes thru connector/oil inlet port 169 and through oil inlet port 6 in the housing 57 of the motor 22.
• an oil pump or the other pumping means 63 is located inside and at the top end of the motor 22.
• the oil pump 63 is driven by a shaft in the motor 22 and circulates the oil in the loop formed by the motor 22, oil conduit or lines 151, 152 and the conduits 133 within the mounting skid 101.
• the fluid carrying volume of such external components in relation to the volume of the fluid conduits within the motor housing 57 can be on the order of five to ten times greater, or more.
• the motor 22 not only operates at a cooler temperature and can operate longer and more reliably as a result of utilization of a the external surrogate heat exchanger, but also operates at such improved conditions due to the increased volume of lubricating oil available to perform the cooling function and the extended life of the lubricating oil resulting from such utilization of a substantially larger volume than that previously possible.
• Various embodiments of the present invention includes several advantages.
• Various embodiments of the present invention provide system components and process steps to circulate motor lubricating fluid/oil for a deployed ESP through the frame of a skid or caisson head. While the lubricating fluid/oil travels through the frame, the motor lubricating fluid/oil is cool down by the sea water around the frame. The cooled lubricating fluid/oil is then used to cool components of the motor located within the motor housing—reducing overall motor temperature and correspondingly increasing the life of the equipment.
• utilization of the frame of the mounting skid or casing head is accomplished by manufacturing multiple structural and/or nonstructural members of the respective frame, generally in tubular form (e.g., hollow along substantial portions of the length of the member), using materials having a high thermal conductivity.
• utilization of a modified version of an existing frame, rather than employing an entirely system heat exchange component can reduce capital costs, need for additional real estate, etc., and, due to the size of the frame, can provide a large seawater contact surface area and a cooling lubricant volume capability (e.g., 5- 10 times fluid capacity) beyond that previously thought of, and thus, a cooling capability beyond that previously possible.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Mining & Mineral Resources (AREA)
• Structures Of Non-Positive Displacement Pumps (AREA)
• Motor Or Generator Cooling System (AREA)
• Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (2)

Family

ID=47357687

Family Applications (1)

Country Status (2)

Cited By (3)

Citations (4)

• 2012
  • 2012-06-12 WO PCT/US2012/042042 patent/WO2012173985A2/en active Application Filing
  • 2012-06-12 BR BR112013031974-7A patent/BR112013031974B1/pt not_active IP Right Cessation

Patent Citations (4)

Also Published As

Similar Documents

Legal Events