Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: Bearing Assembly Cooling Methods
BACKGROUND
[0001] Technical Field: The subject matter generally relates to systems and
techniques in the field of oil and gas operations. Reduction of heat in
rotating control
devices (RCDs) improves the life of such RCDs.
[0002] When a well site is completed, pressure control equipment may be
placed
near the surface of the earth. The pressure control equipment may control the
pressure in the wellbore while drilling, completing and producing the
wellbore. The
pressure control equipment may include blowout preventers (BOP), rotating
control
devices (RCDs), and the like. The RCD is a drill-through device with a
rotating seal
that contacts and seals against the drill string (drill pipe with tool joints,
casing, drill
collars, Kelly, etc.) for the purposes of controlling the pressure or fluid
flow to the
surface.
[0003] RCDs and other pressure control equipment are used in underbalanced
drilling (UBD) and managed pressure drilling (MPD), which are relatively new
and
improved drilling techniques, and work particularly well in certain offshore
drilling
environments. Both technologies are enabled by drilling with a closed and
pressurizable circulating fluid system as compared to a drilling system that
is open-
to-atmosphere at the surface. Managed pressure drilling is an adaptive
drilling
process used to more precisely control the annular pressure profile throughout
the
wellbore. MPD addresses the drill-ability of a prospect, typically by being
able to
adjust the equivalent mud weight with the intent of staying within a "drilling
window"
to a deeper depth and reducing drilling non-productive time in the process.
The
drilling window changes with depth and is typically described as the
equivalent mud
weight required to drill between the formation pressure and the pressure at
which an
underground blowout or loss of circulation would occur. The equivalent weight
of the
mud and cuttings in the annulus is controlled with fewer interruptions to
drilling
progress while being kept above the formation pressure at all times. An influx
of
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formation fluids is not invited to flow to the surface while drilling.
Underbalanced
drilling (UBD) is drilling with the hydrostatic head of the drilling fluid
intentionally
designed to be lower than the pressure of the formations being drilled,
typically to
improve the well's productivity upon completion by avoiding invasive mud and
cuttings damage while drilling. An influx of formation fluids is therefore
invited to flow
to the surface while drilling. The hydrostatic head of the fluid may naturally
be less
than the formation pressure, or it can be induced.
[0004] The thrust generated by the wellbore fluid pressure, the radial
forces on
the bearing assembly within the ROD and other forces cause a substantial
amount of
heat to build in the conventional RCD. The heat causes the seals and bearings
to
wear and subsequently require repair. The conventional ROD typically requires
an
external cooling system that circulates fluid and utilizes various valves and
hose
through the seals and bearings in order to remove the heat. However, risers,
used in
many oilfield operations, particularly subsea operations, may pose significant
obstacles to the use of external coolants, lubricants, lubricating systems
and/or
cooling systems.
[0005] Therefore, an improved system for cooling radial seals and the
bearing
section of an ROD is desired, particularly a system which is able to function
in
environments with or without an external control system. If the radial seals
are not
sufficiently cooled, the localized temperature at the sealing surface will
rise until the
temperature limitations of the seal material is reached and degradation of the
radial
seal begins. High pressure, velocity and temperature conditions at increasing
lengths
of time affect and reduce the length of usable life for a seal. In order to
obtain
sufficient life from radial seals, the rate of heat extraction should be fast
enough to
allow the temperature at the sealing surface to level off at a temperature
lower than
that of the seal material's upper limit.
[0006] US Pub. No. 2006/0144622 proposes a system and method for cooling a
ROD while regulating the pressure on its upper radial seal. Gas, such as air,
and
liquid, such as oil, are alternatively proposed for use in a heat exchanger in
the ROD.
A hydraulic control system is proposed to provide fluid to energize a bladder
of an
active seal to seal around a drilling string and to lubricate the bearings in
the ROD.
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10007]
BRIEF SUMMARY
[00081 The disclosure relates to apparatus and methods for cooling a RCD at a
welibore including a bearing assembly configured for operating in the RCD. A
fixed
latch with a heat exchanger system and a volume of a cooling medium is
configured
for reducing heat proximate the bearing assembly, an inner member, and one or
more seals between the bearing assembly and the inner member.
[0009] As used herein the term "RCD'' or "RCDs" and the phrases "pressure
control
equipment", "pressure control apparatus' or "pressure control device(s)" shall
refer to
well related pressure control equipment/apparatus/device(s) including, but not
limited
to, rotating-control-device(s), active rotating control devices, blowout
preventers
(B0Ps), and the like.
BRIEF DESCRIPTION OF THE FIGURES
[00101 The exemplary embodiments may be better understood, and numerous
objects, features, and advantages made apparent to those skilled in the art by
referencing the accompanying drawings. These drawings are used to illustrate
only
typical exemplary embodiments of this invention, and are not to be considered
limiting of its scope, for the invention may admit to other equally effective
exemplary
embodiments. The figures are not necessarily to scale and certain features and
certain views of the figures may be shown exaggerated in scale or in schematic
in
the interest of clarity and conciseness.
[0011] Figure 1 depicts a schematic view of a well site having pressure
control
devices for sealing an item or piece of oilfield equipment.
Figure 2 depicts a cross sectional view of a pressure control device
embodiment having a fixed latch with a heat exchanger therein and a heat
exchanger system.
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Figure 3 depicts a cross sectional view of half of a pressure control device
embodiment having a carrier having a pressure reduction system and a heat
exchanger profile.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT(S)
[0012] The
description that follows includes exemplary apparatus, methods,
techniques, and instruction sequences that embody techniques of the inventive
subject matter. However, it
is understood that the described exemplary
embodiments may be practiced without these specific details.
f00131 Figure 1 depicts a schematic view of a well site 100 having pressure
control
devices 102 for sealing a rotating drill string or other piece of oilfield
equipment 122.
The well site 100 may have a vvellbore 106 formed in the earth and lined with
a
casing 108. At the Earth's surface or sea floor 110 (see, for example, US
publication
no, 2014/0027129 Figs. 1, 1A and 1B and accompanying description depicting
exemplary schematic views of fixed offshore rig and land wellsites which is
incorporated herein by reference) the one or more pressure control devices 102
may
control pressure in the wellbcre 106. The pressure control devices 102 may
include,
but are not limited to, BOPs, RCDs, and the like. Risers 107 may be positioned
above, with and/or below the pressure control devices 102. The risers 107 may
present challenges to introducing lubricants, coolants, lubrication systems
and/or
cooling systems for the pressure control devices 102. As shown, the top
pressure
control device 102 is an ROD 1.14. A staged seal 116 may be part of a bearing
assembly 117a located in the RCD 114. The staged seal 116 may be a radial seal
having a pressure reduction system 118. The pressure reduction system 118 may
be
a closed piston system configured to stage pressure across the staged seal
116.
Further, the staged seal 116 may be configured to engage and seal an inner
member 104 during oilfield operations. The inner member 104 may be any
suitable.
rotatable equipment to be sealed by the staged seal 116.
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100141 A pressure control device 102 is located directly below the RCD 114 (as
shown) and may be a sealing device 119. The sealing device 119 may have
stripper rubbers 120 for sealing against the rotating drill string or piece of
oilfield
equipment 122, and a bearing assembly 117b. The bearing assembly 117b
includes a bearing 128. The pressure control device 102 may have a fixed latch
(or
RCD body) 126 configured to engage the bearing assembly 117b. The stripper
rubbers 120 may engage the rotating drill string 122 as the drill string 122
is
inserted into the wellbore 106. The fixed latch 126 may have a heat exchanger
130
(see Figure 2) built into the latch in order to cool the latch as will be
discussed in
more detail below. The RCD 114 with the staged seal 116 does not necessarily,
although can be, used above or with the RCD 114 with the sealing device 119.
100151 Figure 2 depicts a cross sectional view of the pressure control device
102
having the fixed latch 126 with a heat exchanger profile 400 therein. A
bearing
assembly 402 includes an outer member 105 and an inner member 104 rotatably
mounted within the outer member 105. The fixed latch 126 may secure the
bearing
assembly 402 within the pressure control device 102. The fixed latch 126 may
allow the inner member 104 to rotate relative to the fixed latch 126 as the
drill
string 122 is run through the pressure control device 102. As the inner member
104 rotates with the drill string 122, the motion creates friction between the
inner
member 104 and an inner surface 407 of the bearing assembly 402. The friction
may cause heating in both the bearing assembly 402 and the seals or shaft
seals
406, which lie between the outer member 105 and the inner member 104. The
increased heat decreases life span of the seals 406 and the bearing assembly
402.
The bearing assembly 402 and the seals 406 may respectively be any suitable
bearing assembly and seals used in the pressure control device 102 including
those described herein.
[00161 The heat exchanger profile 400 may cool the fixed latch 126, and
bearing
assembly 402 during operation thereby extending the life of the seals 406 and
bearing assembly 402. This may further allow the bearing assembly 402 to
operate
or be operational with a self-contained lubricant (i.e. an integral bearing
assembly
402 with lubricant without any external lubrication system or without any
lubrication
system running through a riser 107 to the surface). The heat exchanger
profiles 400
may be fluid passages 401 through the interior surface area 403 of the fixed
latch
126. The fluid passages 401 may be configured to maximize the interior surface
area
403 that is cooled in the fixed latch 126. Any suitable heat exchanger shape
or
channel way for paths/fluid passages 401 may be used for the heat exchanger
profile 400 so long as the fixed latch 126 is cooled. By way of example only,
in the
embodiment shown, there is one inlet 415a and one outlet 415b, to the
path/fluid
passages 401.
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[0017] The heat exchanger profile 400 may be coupled to or integral with a
heat
exchanger system 408 and may cool through or from either side of the RCD 114.
The heat exchanger system 408 may include, but is not limited to, a heat
exchanger
410, a tank 411 for containing a volume of cooling medium or coolant 405, a
pump
412, an optional separate condenser 409, and one or more conduits 414. The
heat
exchanger 410 may be any suitable device for cooling the fluid, a quantity or
volume
of cooling medium 405, circulating through the conduit 414 including, but not
limited
to, the exposed sea temperature on the conduit 414, a shell and tube
exchanger,
and the like. The pump 412 may be any suitable device for circulating the
quantity of
cooling medium 405 from the tank 411 through the conduit 414. The optional
separate condenser 409 may be included to condense any gases or fluids after
having circulated the fluid passages 401 and conduits 414. By way of example
only,
the optional separate condenser 409 may be located near the outlet 415b but
could
also be located near the inlet 415a or intermediate thereto. The pump 412 may
be
any suitable device for delivering the quantity of cooling medium 405 through
the
heat exchanger system 408 including, but not limited to, a centrifugal pump, a
reciprocating pump, and the like. The quantity of cooling medium 405 may be
any
suitable medium for cooling the heat exchanger system 408 including, but not
limited
to, water, sea water, refrigerant, refrigerant mixtures, liquids (including
those that
remain in a liquid state during the heat exchange process) or gasses, air, oil
and/or
the like.
[0018] The inner member 104 may further include an insulating coating 416 on
the
inner surface 142 of the inner member 104. The insulating coating 416 may be
configured to reduce heat transfer from the inner surface 142 of the inner
member
104 caused by heated wellbore fluids to the seals 406. This additional cooling
may
prevent the wear on the seals 406. By way of example only, in one embodiment,
the
insulating coating 416 may be made of ceramic, refractory, hard rubber,
fiberglass,
composite, elastomer, and/or thermal/electrical materials of suitable
thickness for
insulating a passage of inner member 104. In addition, the insulating coating
416
may extend to one or more surfaces on the stripper rubber mount 132 to which
the
stripper rubber(s) 120 are attached to.
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[0019] Figure 3 depicts a cross sectional view of half of a pressure control
device
102 embodiment having a carrier 500 (see US Provisional Appl. No. 61/986,544,
filed on April 30, 2014, which is herein incorporated by reference) having the
pressure reduction system 118 and in the heat exchanger profile 400. The
carrier
500 as shown is configured to support a seal element 502 for engaging the
drill
string 122. The seal element 502 may be configured to seal drill string 122 as
the
drill pipe is run into or out of the wellbore 106 (as shown in Figure 1). The
carrier 500
may be located below, above or within the bearing assembly 117 of an RCD 114.
In
one embodiment, the pressure reduction system 118 may operate in the same
manner as described in US Provisional Appl. No. 61/986,544, in order to apply
pressure to the outer radial surface 504 of the seal element 502. In another
embodiment, the pressure reduction system 118 may be controlled by a hydraulic
unit or controller in order to maintain the pressure on the outer radial
surface 504 of
the seal element 502.
[0020] The heat exchanger profile 400 may operate in the same manner as
described in conjunction with Figure 2. To this end, the heat exchanger
profile 400
may be a part of the heat exchanger system 408 and have the heat exchanger
410,
the pump 412 and the conduit 414 (as shown in Figure 2). A carrier inlet 510
and a
carrier outlet (not pictured) may continue or extend the heat exchanger
profiles 400
from the fixed latch 126 into the carrier 500 (or from another heat exchanger
profile
400 independent of the fixed latch 126), allowing the cooling medium 405 to
circulate
through the carrier 500. The heat exchanger profile 400 in the carrier 500 may
reduce the heat in the carrier 500 and thereby reduce the temperature of the
volume
of fluid 303 applying pressure to the seal element 502. Further, the carrier
500 may
have a layer of insulating coating 506 on the carrier's surfaces 508 (by way
of
example on the outer or exterior surface) to help reduce heat transfer caused
by
heated wellbore fluids. The decreased temperature applied to the seal element
502
may reduce wear and increase the life of the seal element 502.
[0021] In addition, the heat exchanger system 408, heat exchanger profile 400,
and
carrier 500 may be a closed hydraulic control system 420, thereby eliminating
the
need for an external cooling system to control the temperature of the pressure
control device 102. A closed hydraulic system 420 may relieve demand on
limited
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resources, and further, addresses difficulty in installing and maintaining an
external
cooling system in extreme environments. Risers 107, used in subsea operations,
may also pose significant obstacles to the use of external cooling systems.
[0022] While the exemplary embodiments are described with reference to various
implementations and exploitations, it will be understood that these exemplary
embodiments are illustrative and that the scope of the inventive subject
matter is not
limited to them. Many variations, modifications, additions and improvements
are
possible. For example, although the exemplary embodiments have thus far been
depicted and described with a closed hydraulic control system 420, the
exemplary
embodiments described within may also be utilized in conjunction with an open
or
external hydraulic control system. Further, the implementations and techniques
used herein may be applied to any strippers, seals, or packer members at the
well
site, such as the BOP, and the like.
[0023] Plural
instances may be provided for components, operations or structures
described herein as a single instance. In general, structures and
functionality
presented as separate components in the exemplary configurations may be
implemented as a combined structure or component. Similarly, structures and
functionality presented as a single component may be implemented as separate
components. These
and other variations, modifications, additions, and
improvements may fall within the scope of the inventive subject matter.
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