Note: Descriptions are shown in the official language in which they were submitted.
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SUBMERSIBLE PUMP HOUSING WITH SEAL BLEED PORTS
BACKGROUND
[0001] An electric
submersible pump (ESP) is often used in well
settings to artificially lift subsurface resources such as hydrocarbons and
water to the Earth's surface. Conventionally, the maximum pressure
rating of a given ESP housing is limited by the stresses in the threaded
end portion of the ESP housing. In a conventional centrifugal pump
housing (diffuser), for example, the housing is sealed at the head and at
the base with an 0-ring seal located at the end of the housing and
outboard of the end threads. Conventional arrangement of the end seals
in an ESP causes the circumferential or hoop stresses of the housing in
the threaded region to be the sum of the hoop stresses due to the thread
radial forces resulting from axial loads on the thread flank angle, and the
internal pressure differential from inside to outside the housing. The sum
of these hoop stresses determines the maximum pressure rating of a
conventional housing. Some conventional ESP housings have end seals
both inboard and outboard of the threaded ends of the conventional
housings. However, there is no fluid path from inside to outside the
housing between these two seals. Thus, this conventional arrangement
can trap the high internal pressure between the two seals and render the
conventional inboard seal ineffective.
SUMMARY
A submersible pump housing with seal bleed ports is described. In
an implementation, the submersible pump housing includes a housing,
an interior compartment of the housing for fluid at high thrust pressure, a
threaded end region of the housing, an inboard end seal to seal off the
threaded end region from the interior compartment; and at least one
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bleed hole or port outboard of the end seal for allowing leakage of fluid
from the interior compartment past the end seal to escape radially
through the housing. An example centrifugal pump housing may include
a diffuser for directing high thrust fluid accelerated by an impeller, an end
seal inboard of each threaded end of the centrifugal pump housing, and
at least one leak port outboard of each end seal to relieve a fluid seeping
from inside the centrifugal pump housing past each end seal. An
example method includes locating an end seal inboard of a threaded
portion of a centrifugal pump housing to seal internal pressure from the
threaded portion, and locating a radial bleed port outboard of the end
seal to relieve pressure of seepage past the end seal. This summary
section is not intended to give a full description of submersible pump
housings with seal bleed ports. A detailed description with example
embodiments follows.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0002] Fig. 1 is a diagram of an example electric submersible pump
(ESP) section with inboard end seals and seal bleed ports.
[0003] Fig. 2 is a diagram of a second example ESP section with
inboard end seals and seal bleed ports.
[0004] Fig. 3 is a diagram of an example ESP section with inboard
end seals, seal bleed ports, and a lockplate protector.
[0005] Fig. 4 is a flow diagram of an example method of increasing
the pressure rating of a submersible pump housing.
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DETAILED DESCRIPTION
[0006] This disclosure describes submersible pump housings with
seal bleed ports. Features, systems, and methods associated with
submersible pump housings with seal bleed ports represent possible
implementations and are included for illustration purposes and should not
be construed as limiting. Moreover, it will be understood that different
implementations can include all or different subsets of aspects described
below. Furthermore, the aspects described below may be included in
any order, and numbers and/or letters placed before various aspects are
done for ease of reading and in no way imply an order, or level of
importance to their associated aspects.
[0007] Fig. 1 shows a section of an example electric submersible
pump (ESP) 100 of the centrifugal type. The illustrated section shows a
base-end portion of the centrifugal ESP 100. An impeller region 102
inside the pump housing generates high thrust pressure as the impeller
accelerates fluid radially outward and axially upward, or toward a
wellhead of an ESP installation. At the periphery of the pump housing,
the fluid in the interior high pressure compartment 104 that includes the
impeller region 102 extends to a location at which the end seal 106 is
situated to seal off the high thrust pressure and highly mobilized fluid
from flowing out to the exterior of the pump housing or from flowing out to
the next component in a stack of components.
[0008] In the example centrifugal ESP 100 with seal bleed ports
108, the end seals 106 are inboard of the threaded end regions 110 of
the pump housing in order to contain the high pressure compartment 104
and prevent the threaded end region 110 from participating in the interior
high pressure compartment(s) of the ESP 100. This arrangement of
having the end seals 106 inboard of the threads 110 increases the
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maximum pressure rating of the pump housing, because the threaded
end regions 110 of conventional pumps are subject to increased stresses
over the non-threaded regions of conventional pump housings when
subjected to interior pump pressures. In Fig. 1, the bleed ports 108 or
vent ports are located just outboard of the end seal 106 to provide a leak
path for fluid that seeps or blows by the end seal 106. The terms "port"
and "hole" as used herein, are used representatively to mean a fluid path,
passageway, port, hole, lumen, channel, vent, etc., enabling the
movement of fluid from one location to another. The vent ports do not
have to be "holes," such as a round, straight passages as drilled by a bit.
For example, the term bleed ports 108 can mean a vent passage that is a
milled castellation(s) in the end face of either the housing or end cap
(base or head).
[0009] In an implementation, the vent passage, leak path, or seal
bleed ports 112 may be located outboard of the threaded end region 110,
instead of just outboard of the end seal 106 as seal bleed ports 108 are.
Locating the bleed ports 112 outboard of the threads 110 utilizes the threads
110 to dissipate leakage fluid pressure and minimize jetting velocity of fluid
that
has escaped the end seal 106.
[0010] The term "outboard" or "outboard of' as used herein, means
"outside" or "on the other side of a designated feature that is closer to, or
more "inboard," to the pump's high thrust pressure compartments or to
the fluids being accelerated by the pump. Correspondingly, "inboard," as
used herein, means "inside of," in first contact with, or in closer contact
with the high thrust pressure generated by the pump than a designated
feature that is therefore more "outboard."
[0011] Fig. 2 shows an example centrifugal ESP 200 with cutaway
housing 202. The illustrated section shows a head-end portion of the
example centrifugal ESP 200. The example centrifugal ESP 200
includes one or more impeller regions 204 in a high thrust pressure
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compartment. An end seal 206 is positioned inboard of one or more fluid
bleed ports 208. The end seal 206 is also positioned inboard of a
threaded end region 210. The illustrated bleed ports 208 are radially-
directed to form a leak path from outboard of the end seal 206 to the
exterior of the housing 202. In this manner, an internal pressure
differential caused by the pumping action of the example centrifugal ESP
200 is sealed off from the end threads 210, and the hoop stresses in the
same threaded region 210 are significantly reduced to enable a higher
maximum pressure rating for the overall housing 202 of the example
centrifugal ESP 200. Any fluid leakage that does seep past the end seal
206 on account of the high pressure that is inboard of the end seal 206 is
allowed to escape the housing 202 without building up at the threaded
region 210.
[0012] The bleed
ports 208 form a leak path that is situated from
inside to outside the housing 202 just outboard of the end seal 206. The
leak path can be implemented so that a very small leakage of fluid past
the end seal 206 does not pressure the space or volume that may exist
between the end seal 206 and the contact face between the head (or the
base) and the centrifugal pump housing 202. If this volume is pressured,
then the same undesired stress state that exists in conventional housings
occurs. In an implementation, the leak path can be created by drilling
small radial holes in the housing 202 just downstream (outboard) of the
end seal(s) 206. In an implementation, the seal bleed ports 214 may be
located to form a leak path outboard of the threaded end region 210,
instead of just outboard of the end seal 206 as seal bleed ports 208 are.
Locating the bleed ports 214 outboard of the threads 210 utilizes the threads
210 to dissipate leakage fluid pressure and minimize jetting velocity of fluid
that
has escaped the end seal 206. The head-end of compression ring (CR)
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style pumps also requires a bleed path, such as port 212, for weepage
that may occur past the compression ring-to-head seal.
[0013] Fig. 3 shows a centrifugal pump housing 302 with inboard
seal 306, bleed port 308, and an example housing lockplate protector
310. The lockplate protector 310 covering the bleed port 308 shown in
Fig. 3 can be used to protect the well casing from any damage due to
fluid leaking from the radial bleed port 308 in the housing 302. The
lockplate protector 310 can be a standard lockplate except that the
housing-facing side of the lockplate can be stepped to allow bleed fluid to
be deflected axially along the housing 302 rather radially toward the bore
of the well casing.
[0014] In an implementation, an example submersible pump
includes a housing, an interior compartment of the housing for fluid at
high thrust pressure, a threaded end region of the housing, an inboard
end seal to seal off the threaded end region from the interior
compartment, and at least one bleed port or hole outboard of the end
seal for allowing leakage of fluid from the interior compartment past the
end seal to escape radially from the end seal through the housing.
[0015] The example submersible pump may comprise a centrifugal
electric submersible pump (ESP) for the oil and gas industries. The
housing may comprise a diffuser of the centrifugal ESP. The inboard end
seal protects the threads to increase the pressure rating of the housing.
The at least one bleed port can relieve a pressure between the end seal
and a contact face between the submersible pump housing and a head
or a base connecting to the submersible pump.
[0016] A lockplate protector over the bleed port can protect a well
casing from the leakage of fluid from the interior compartment past the
end seal. The lockplate protector can be stepped to deflect fluid axially
along the housing instead of radially toward a bore of the well casing.
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[0017] When the submersible pump is a compression ring (CR)
style pump, a leak port can be used for weepage past a compression
ring-to-head seal.
[0018] A centrifugal ESP may operate at temperatures of up to
approximately 149 degree Celsius and pressures of up to approximately
6,000 pounds per square inch or approximately 41 megapascals in a
downhole environment of up to approximately 12,000 feet or 3.7
kilometers deep. The centrifugal ESP can use up to approximately 1000
horsepower or 750 kilowatts of power and has a speed of rotation of a
rotor of up to approximately 4000 revolutions per minute. Even in such
harsh conditions, the end seal protects the threaded end region from the
fluid at high thrust pressure in the interior compartment of the centrifugal
ESP.
[0019] In an implementation, a centrifugal pump housing includes a
diffuser for directing high thrust fluid accelerated by an impeller, an end
seal inboard of each threaded end of the centrifugal pump housing, and
at least one leak port outboard of each end seal to relieve a fluid seeping
from inside the centrifugal pump housing past each end seal. Each leak
port can relieve a pressure between a respective end seal and a contact
face between the centrifugal pump housing and a head or a base.
[0020] A lockplate protector can be used over the leak port. The
lockplate protector protects the well casing from a fluid leaking from the
leak port. The lockplate protector can be stepped to deflect fluid axially
along the centrifugal pump housing instead of allowing the fluid to escape
radially toward a bore of the well casing.
Example Method
[0021] Fig. 4 shows an example method 400 of increasing the
pressure rating of a submersible pump housing. In an implementation,
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,
the submersible pump can be a centrifugal ESP. In the flow diagram,
operations are shown in individual blocks.
[0022] At block 402, an end seal is located inboard of the
threaded
portion of a submersible pump housing to seal internal pressure from the
threaded portion.
[0023] At block 404, radial bleed ports are located outboard of
the
end seal to relieve pressure of small blow-by or seepage past the end
seal.
[0024] The example method enables an internal pressure
differential of the submersible pump to be sealed from the end threads,
and the hoop stresses in the threaded region of the housing to be
significantly reduced, achieving a higher pressure rating for the example
submersible pump housing.
Conclusion
[0025] Although only a few example embodiments have been
described in detail above, those skilled in the art will readily appreciate
that many modifications are possible in the example embodiments
without materially departing from the subject matter. Accordingly, all such
modifications are intended to be included within the scope of this
disclosure as defined in the following claims. In the claims, means-plus-
function clauses are intended to cover the structures described herein as
performing the recited function and not only structural equivalents, but
also equivalent structures. It is the express intention of the applicant not
to invoke 35 U.S.C. 112, paragraph 6 for any limitations of any of the
claims herein, except for those in which the claim expressly uses the
words 'means for' together with an associated function.
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