Note: Descriptions are shown in the official language in which they were submitted.
WO 2012/015927 CA 02806109 2013-01-18PCT/US2011/045543
DHM4-50226W0 (INT0363PCT)
DOWNHOLE SEAL AND METHOD OF LUBRICATING A DOWNHOLE TOOL
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of both U.S. Provisional Patent
Application
No. 61/367,976 filed July 27, 2010 and U.S. Provisional Patent Application
61/371,281 filed
August 6, 2010, the entire contents of which are incorporated herein by
reference.
BACKGROUND
[0002] Elastomeric parts such as downhole seals, for example, that are used to
dynamically seal to other components located within a borehole of an earth
formation often
have durability issues. These durability issues are often due to wear
resulting from frictional
engagement between parts. Those who practice in downhole industries would
welcome
devices and methods to increase the useful life of downhole seals.
BRIEF DESCRIPTION
[0003] Disclosed herein is a downhole seal. The seal includes a body
configured to
dynamically seal to a portion of a downhole tool and a lubricant
microencapsulated in a
plurality of shells to form a plurality of micro particles dispersed within
the body.
[0004] Further disclosed herein is a method of lubricating a downhole tool.
The
method includes, microencapsulating lubricant within a plurality of shells,
distributing the
plurality of shells microencapsulating lubricant within at least one of a
first component and a
second component that dynamically seal to one another, rupturing at least some
of the
plurality of shells microencapsulating lubricant, and releasing the lubricant
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] The following descriptions should not be considered limiting in any
way.
With reference to the accompanying drawings, like elements are numbered alike:
[0006] FIG. 1 depicts a sectioned view of a portion of a downhole mud motor
with a
downhole seal disclosed herein employed in the mud motor as a stator having
two parts;
[0007] FIG. 2 depicts a sectioned view of a portion of the downhole mud motor
of
FIG. 1 showing the downhole seal disclosed herein in relation to a rotor;
[0008] FIG. 3 depicts a sectioned view of a mud motor having an alternate
downhole
seal disclosed herein having a single body; and
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DHM4-50226W0 (INT0363PCT)
[0009] FIG. 4 depicts a sectioned view of an alternate embodiment of a seal
disclosed
herein.
DETAILED DESCRIPTION
[0010] A detailed description of one or more embodiments of the disclosed
apparatus
and method are presented herein by way of exemplification and not limitation
with reference
to the Figures.
[0011] Referring to Figure 1, an embodiment of a downhole seal disclosed
herein is
illustrated generally at 10 as a stator of a motor, such as a mud motor.
Alternately, the stator
could also be employed in a pump while still remaining within the scope
disclosed herein.
The stator 10, in this embodiment includes, a plurality of parts with a first
part 14A being
illustrated as a first layer 14A and a second part 14B being illustrated as a
second layer,
although alternate embodiments may have more layers or as few as one layer.
The stator 10
is fixedly attached to a housing 16 and allows a rotor 18 engaged therewith to
rotate relative
thereto in response to fluid flowing between the stator 10 and the rotor 18.
Since a number of
lobes 22 (5 in the Figure) of the stator 10 is different than a number of
lobes 26 (4 in the
Figure) of the rotor 18, rotation of the rotor 18 results in one of the lobes
22 moving
sequentially relative to one of the lobes 26 then to another and to another,
and so on. This
movement defines relative motion between the stator 10 and the rotor 18.
[0012] This relative motion causes some points along the first layer 14A of
the stator
to repeatedly make and break contact with the rotor 18 while at other points
the first layer
14A slides tangentially relative to the rotor 18. Dynamic sealing between the
first layer 14A
and the rotor 18 at points of contact and sliding is desirable for improved
operation of the
motor. The repeated contacting and sliding, however, causes wear of the
components. The
first layer 14A, as disclosed herein, is made primarily of an elastomer while
the rotor 18 is
made of metal. The difference in hardnesses of these materials typically
causes the first layer
14A to wear more quickly than the rotor 18. Lubrication between a surface 28
of the first
layer 14A and a surface 29 of the rotor 18 can increase the useful life of the
first layer 14A,
however, fluid flowing between the first layer 14A and the rotor 18 tends to
purge lubrication
from the surfaces 28, and 29.
[0013] Referring to Figure 2, a majority of the first layer 14A is made of an
elastomer
30. In one embodiment, embedded in the elastomer 30 is at least one lubricant
34; small
quantaties of which are microencapsulated within shells 38. A multitude of
microcapsules
42, filled with the lubricant 34, are dispersed throughout a volume of the
first layer 14A. In
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DHM4-50226W0 (INT0363PCT)
this embodiment, the dispersion is accomplished by mixing the microcapsules 42
in with the
elastomeric compound prior to molding the first layer 14A. In alternate
embodiments the
lubricant 34 can be introduced as coated micro or nano particles of
carbonaceous
nanoparticles, for example, with the coating defining the shell 38. In such an
embodiment the
nanoparticles can include, carbon nanotubes (CNT), single-walled carbon
nanotubes
(SWCNT), double-walled carbon nanotubes (DWCNT), and non-nanotube
configurations
such as graphenes, fullerenes and diamonds, for example. The lubricant could
also be
molybdenum disulfide, hexagonal boron nitride, polytetrafluoroethylene (PTFE),
or graphite.
Regardless of whether the lubricant 34 is solid or fluid, such as a liquid
lubricant like oil, the
shell 38 is constructed to sufficiently isolate the lubricant 34 from the
elastomer 30 during
manufacture to minimize degrading the material properties, such as, strength
and thermal
conductivity, for example, of the first layer 14A. Yet the shell 38 is
fractured when exposed
to loads generated as the surfaces 28, 29 contact and/or slide relative to one
another. Upon
fracturing of the shell 38 the lubricant 34 is released from the microcapsules
42 and is able to
form a lubricating film 46 on one or both of the surfaces 28 and 29. As the
lubricating film
46 is washed away, the surface 28 wears, and new microcapsules 42 are exposed
to loads that
fracture the shells 38 thereby releasing additional quantities of the
lubricant 34 thereby
slowing the wear rate of the fist layer 14A.
[0014] Referring to FIG. 3, an alternate embodiment of a downhole seal
disclosed
herein is illustrated at 60. The downhole seal 60 differs from the downhole
seal 10 primarily
in that the seal 60 is a single body 64, whereas the seal 10 is made of the
first layer 14A and
the second layer 14B. As such, the seal 60 has the microcapsules 42 of the
lubricant 34
dispersed throughout the elastomer 30 of the entire seal 60. Each of these two
embodiments
may have advantages over the other. For example, the seal 60 may be less
expensive to
fabricate since it doesn't require assembly of two different portions.
Alternatively, the seal
may have advantages in durability since the second layer 14B can be made of a
material
having more robust mechanical properties and fluid chemical resistance while
the first layer
14A is made of material, as described above, that has better friction and wear
properties due
to the lubricant 34 dispersed therein.
[0015] Referring to FIG. 4, a cross section of an embodiment of a mud motor
disclosed herein is illustrated at 110. The mud motor 110 includes, a stator
114 with a
contoured surface 118 configured to functionally engage with a complementary
surface 122
of a rotor 126. In this embodiment the rotor 126 has two parts, an outer layer
126A and an
inner layer 126B, with at least the outer layer 126A including a plurality of
the microcapsules
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42. Alternate embodiments could have the entirety of the rotor 126A and 126B
filled with
the microcapsules 42 instead of just the outer layer 126A and the structure
could be a single
part as opposed to being the two-part configuration illustrated herein.
Additionally, the stator
114 can also be a single piece structure or a two-piece structure having the
inner layer 114A
and the outer layer 114B as is illustrated in this embodiment. The material of
the stator 114
can vary with one embodiment being steel with an abrasion resistant coating on
the surface
118. In embodiments wherein the stator 114 is metal the part material
configuration is
essentially reversed to that of the embodiments illustrated in Figures 1 and
3.
[0016] While the invention has been described with reference to an exemplary
embodiment or embodiments, it will be understood by those skilled in the art
that various
changes may be made and equivalents may be substituted for elements thereof
without
departing from the scope of the invention. In addition, many modifications may
be made to
adapt a particular situation or material to the teachings of the invention
without departing
from the essential scope thereof. Therefore, it is intended that the invention
not be limited to
the particular embodiment disclosed as the best mode contemplated for carrying
out this
invention, but that the invention will include all embodiments falling within
the scope of the
claims. Also, in the drawings and the description, there have been disclosed
exemplary
embodiments of the invention and, although specific terms may have been
employed, they
are unless otherwise stated used in a generic and descriptive sense only and
not for purposes
of limitation, the scope of the invention therefore not being so limited.
Moreover, the use of
the terms first, second, etc. do not denote any order or importance, but
rather the terms first,
second, etc. are used to distinguish one element from another. Furthermore,
the use of the
terms a, an, etc. do not denote a limitation of quantity, but rather denote
the presence of at
least one of the referenced item.
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