U.S. patent application number 10/694557 was filed with the patent office on 2005-04-28 for composite material progressing cavity stators.
This patent application is currently assigned to Dyna-Drill Technologies, Inc.. Invention is credited to Delpassand, Majid S., Gallagher, James.
Application Number | 20050089429 10/694557 |
Document ID | / |
Family ID | 34522631 |
Filed Date | 2005-04-28 |
United States Patent
Application |
20050089429 |
Kind Code |
A1 |
Delpassand, Majid S. ; et
al. |
April 28, 2005 |
Composite material progressing cavity stators
Abstract
A progressing cavity stator is provided. The progressing cavity
stator includes a fiber reinforced composite component providing an
internal helical cavity having at least one helical groove and an
elastomeric liner disposed on an internal surface of the fiber
reinforced composite component. In various exemplary embodiments,
the fiber reinforced composite component includes a plurality of
fibers disposed in a matrix material, the plurality of fibers being
disposed such that distinct portions thereof follow correspondingly
distinct directions. Exemplary embodiments of this invention may
advantageously exhibit a prolonged service life in downhole
applications as compared to conventional progressing cavity
stators. A replaceable progressing cavity insert for a stator is
also provided. Methods for fabricating progressing cavity stators
and progressing cavity inserts are also provided.
Inventors: |
Delpassand, Majid S.;
(Houston, TX) ; Gallagher, James; (Little Compton,
RI) |
Correspondence
Address: |
W-H ENERGY SERVICES, INC.
10370 RICHMOND AVENUE
SUITE 990
HOUSTON
TX
77042
US
|
Assignee: |
Dyna-Drill Technologies,
Inc.
Houston
TX
|
Family ID: |
34522631 |
Appl. No.: |
10/694557 |
Filed: |
October 27, 2003 |
Current U.S.
Class: |
418/48 |
Current CPC
Class: |
F04C 13/008 20130101;
F04C 2/1075 20130101; F05C 2253/04 20130101 |
Class at
Publication: |
418/048 |
International
Class: |
F01C 001/10; F04C
018/00 |
Claims
We claim:
1. A method for fabricating a progressing cavity stator, the method
comprising: (a) providing a first core having at least one helical
groove on an outer surface thereof; (b) disposing a plurality of
fibers in each helical groove to form a fiber preform; (c)
inserting the fiber preform into a cylindrical tube; (d) injecting
a resin into the cylindrical tube to form an impregnated fiber
preform; (e) removing the first core from the impregnated fiber
preform thereby forming an internal helical cavity in the
impregnated fiber preform; (f) inserting a second core having at
least one helical groove on an outer surface thereof into the
internal helical cavity of the impregnated fiber preform, the
second core having a smaller diameter than that of the first core,
thereby forming a substantially helical annulus between the second
core and the impregnated fiber preform; (g) injecting an
elastomeric material into the helical annulus; and (h) removing the
second core.
2. The method of claim 1, wherein the first core comprises a number
of helical grooves in a range from two to about ten.
3. The method of claim 1, wherein fibers among the plurality
thereof are selected from the group consisting of fiber roving,
woven fibers, non-woven fibers, braided fibers, braided fiber
bundles, fiber bundles, fiber bundles wrapped in a braided fiber
tube, chopped fibers, stitched three-dimensional fabrics, and
combinations thereof.
4. The method of claim 1, wherein fibers among the plurality
thereof are selected from the group consisting of glass fibers,
carbon fibers, aramid fibers, boron fibers, polyester fibers,
polyethylene fibers, and combinations thereof.
5. The method of claim 1, wherein (b) comprises disposing fibers on
the first core such that distinct portions of the fibers follow
correspondingly distinct directions.
6. The method of claim 1, wherein (b) comprises disposing fibers on
the first core such that distinct portions of the fibers are
intertwined and follow correspondingly distinct directions.
7. The method of claim 1, wherein (b) further comprises: (1)
disposing a braided fiber layer about the first core; (2) disposing
one or more braided fiber tubes in each helical groove; and (3)
securing the braided fiber tubes in the helical grooves with fiber
windings deployed circumferentially around the braided fiber
tubes.
8. The method of claim 1, wherein (b) comprises disposing a three
dimensional fiber strand in each helical groove about the first
core, each three dimensional fiber strand having a profile
substantially complementing its corresponding helical groove.
9. The method of claim 1, wherein the cylindrical tube in (c)
comprises an inner diameter substantially equal to an outer
diameter of the fiber preform;
10. The method of claim 9, wherein the inner surface of the
cylindrical tube is substantially coated with a mold release
compound.
11. The method of claim 1, wherein (d) comprises vacuum assisted
resin transfer molding.
12. The method of claim 1, wherein at least one of the first core
and the second core include a tapered outer diameter along a length
thereof.
13. The method of claim 1, further comprising: (i) separating the
impregnated fiber preform from the cylindrical tube.
14. The method of claim 13, further comprising: (j) machining an
outer surface of the impregnated fiber preform.
15. The method of claim 14, wherein 0) comprises machining at least
one groove on the outer surface of the impregnated fiber preform,
each groove sized and shaped for engagement with a corresponding
key deployed on an inner surface of a stator tube.
16. A replaceable progressing cavity insert for a stator, the
replaceable insert comprising: a fiber reinforced composite
component providing an internal helical cavity, the fiber
reinforced composite component having an internal surface, the
internal surface having at least one helical groove provided
thereon; an elastomeric liner disposed on the internal surface of
the fiber reinforced composite component; and the insert having an
outer surface, the outer surface sized and shaped for removable
receipt within a cylindrical tube.
17. The replaceable insert of claim 16, wherein the cylindrical
tube is couplable with a drill string.
18. The replaceable insert of claim 16, wherein: the outer surface
provides at least one longitudinal groove; an inner surface of the
cylindrical tube includes at least one corresponding longitudinal
key; and each corresponding pair of longitudinal grooves and keys
is sized and shaped for selective engagement and disengagement
during said removable receipt of the insert in the cylindrical
tube.
19. The replaceable insert of claim 16, wherein the outer surface
is sized and shaped for removable press fitting within the
cylindrical tube.
20. The replaceable insert of claim 16, wherein distinct portions
of the plurality of fibers follow correspondingly distinct
directions.
21. The replaceable insert of claim 16, wherein distinct portions
of the plurality of fibers are intertwined and follow
correspondingly distinct directions.
22. The replaceable insert of claim 16, wherein fibers among the
plurality thereof are selected from the group consisting of fiber
roving, woven fibers, non-woven fibers, braided fibers, braided
fiber bundles, fiber bundles, fiber bundles wrapped in a braided
fiber tube, chopped fibers, stitched three-dimensional fabrics, and
combinations thereof.
23. The replaceable insert of claim 16, wherein fibers among the
plurality thereof are selected from the group consisting of braided
fibers and braided fiber bundles.
24. The replaceable insert of claim 16, wherein fibers among the
plurality thereof are selected from the group consisting of glass
fibers, carbon fibers, aramid fibers, boron fibers, polyester
fibers, polyethylene fibers, and combinations thereof.
25. The replaceable insert of claim 16, wherein the matrix material
comprises an epoxy resin.
26. The replaceable insert of claim 16, wherein the elastomeric
liner has a non-uniform thickness, the non-uniform thickness
varying in directions of at least one of parallel to a cylindrical
axis of the replaceable insert and radially about the cylindrical
axis.
27. A progressing cavity stator comprising: a substantially
cylindrical tool body having a cylindrical axis and two ends; a
fiber reinforced composite component disposed in the tool body
substantially coaxially with the cylindrical axis, the fiber
reinforced composite component providing an internal helical
cavity, the fiber reinforced composite component having an internal
surface, the internal surface having at least one helical groove
provided thereon; an elastomeric liner disposed on the internal
surface; and the elastomeric liner having a non-uniform thickness,
the non-uniform thickness varying in directions of at least one of
parallel to the cylindrical axis and radially about the cylindrical
axis.
28. The progressing cavity stator of claim 27, wherein the
thickness of the elastomeric liner increases in a direction
parallel to the cylindrical axis from one end of the tool body to
the other end of the tool body.
29. The progressing cavity stator of claim 27, wherein the
elastomeric liner includes a substantially periodic thickness
variation radially about the cylindrical axis.
30. The progressing cavity stator of claim 27, wherein the fiber
reinforced composite component comprises a plurality of fibers
disposed in a matrix material, the plurality of fibers disposed
such that distinct portions thereof follow correspondingly distinct
directions.
31. The progressing cavity stator of claim 30, wherein the distinct
portions of the plurality of fibers are intertwined and follow
correspondingly distinct directions.
32. A progressing cavity stator comprising: a fiber reinforced
composite component having a cylindrical axis, the fiber reinforced
composite component providing an internal helical cavity, the fiber
reinforced composite component having an internal surface, the
internal surface having at least one helical groove provided
thereon; an elastomeric liner disposed on the internal surface; and
the fiber reinforced composite component including a plurality of
fibers disposed in a matrix material, the plurality of fibers
disposed such that distinct portions thereof follow correspondingly
distinct directions.
33. The progressing cavity stator of claim 32, wherein the distinct
portions of the plurality of fibers are intertwined and follow
correspondingly distinct directions.
34. The progressing cavity stator of claim 32, wherein fibers among
the plurality thereof are selected from the group consisting of
fiber roving, woven fibers, non-woven fibers, braided fibers,
braided fiber bundles, fiber bundles, fiber bundles wrapped in a
braided fiber tube, chopped fibers, stitched three-dimensional
fabrics, and combinations thereof.
35. The progressing cavity stator of claim 32, wherein fibers among
the plurality thereof are selected from the group consisting of
braided fibers and braided fiber bundles.
36. The progressing cavity stator of claim 32, wherein fibers among
the plurality thereof are selected from the group consisting of
glass fibers, carbon fibers, aramid fibers, boron fibers, polyester
fibers, polyethylene fibers, and combinations thereof.
37. The progressing cavity stator of claim 32, wherein the matrix
material comprises an epoxy resin.
38. The progressing cavity stator of claim 32, wherein the fiber
reinforced composite component is deployed in a substantially
cylindrical tool body, the tool body being substantially coaxial
with the cylindrical axis of the fiber reinforced composite
component.
39. The progressing cavity stator of claim 38, wherein the
cylindrical tool body is couplable with a drill string.
40. The progressing cavity stator of claim 32, wherein the
elastomeric liner has a non-uniform thickness, the non-uniform
thickness varying in directions of at least one of parallel to the
cylindrical axis and radially about the cylindrical axis.
41. A progressing cavity stator, wherein the progressing cavity
stator is a product of the process comprising: (a) providing a
first core having at least one helical groove on an outer surface
thereof; (b) disposing a plurality of fibers in each helical groove
to form a fiber preform; (c) inserting the fiber preform into a
cylindrical tube; (d) injecting a resin into the cylindrical tube
to form an impregnated fiber preform; (e) removing the first core
from the impregnated fiber preform thereby forming an internal
helical cavity in the impregnated fiber preform; (f) inserting a
second core having at least one helical groove on an outer surface
thereof into the internal helical cavity of the impregnated fiber
preform, the second core having a smaller diameter than that of the
first core, thereby forming a substantially helical annulus between
the second core and the impregnated fiber preform; (g) injecting an
elastomeric material into the helical annulus; and (h) removing the
second core.
42. A downhole drilling motor comprising: a progressing cavity
stator including: a substantially cylindrical tool body having a
cylindrical axis; a fiber reinforced composite component disposed
in the tool body substantially coaxially with the cylindrical axis,
the fiber reinforced composite component providing an internal
helical cavity, the fiber reinforced composite component having an
internal surface having at least one helical groove provided
therein; an elastomeric liner disposed on the internal surface of
the fiber composite component; the fiber reinforced composite
component including a plurality of fibers disposed in a matrix
material, the plurality of fibers being disposed such that distinct
portions thereof follow correspondingly distinct directions; and a
helical rotor operational within the internal helical cavity of the
progressing cavity stator;
43. The downhole drilling motor of claim 42, wherein the fiber
reinforced composite component and the elastomeric liner form a
progressing cavity insert, the progressing cavity insert having an
outer surface sized and shaped for removable receipt within the
cylindrical tool body.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to progressing
cavity hydraulic drilling motors, typically for downhole use. This
invention more specifically relates to fiber reinforced composite
stators and methods for fabricating fiber reinforced composite
stators.
BACKGROUND OF THE INVENTION
[0002] Progressing cavity hydraulic motors and/or pumps are well
known in downhole drilling and artificial lift applications, such
as for oil and/or gas exploration. Such progressing cavity motors
make use of hydraulic power from drilling fluid to provide power,
for example, to a drill bit assembly. The power section of a
typical progressing cavity motor includes a helical rotor disposed
within the cavity of a corresponding stator and converts the
hydraulic power of high pressure drilling fluid to mechanical power
(e.g., torque). Flow of the high pressure drilling fluid down
through the rotor stator assembly rotates the rotor relative to the
stator (which is usually connected to a motor housing). The rotor
is typically coupled, for example, through a universal connection
and an output shaft to a drill bit assembly.
[0003] Conventional stators typically include an elastomeric (e.g.,
rubber) contact surface bonded to the inner wall of a steel
housing. In order to form a progressing cavity, the elastomer is
typically thicker at the peaks of the helicoid. It has been
observed that working (i.e., flexing) of the elastomer (via
rotational contact between the rotor and stator) during operation
causes degradation thereof, particularly at thick regions at the
peaks of the helicoid. It is thought that such degradation results
from heat build up in the elastomer (due to the relatively low
thermal conductivity of elastomeric materials). The thicker regions
are believed to attain relatively higher temperatures than thinner
regions of the helicoids, and are hence more prone to degradation
and failure. Such degradation (or weakening) of the elastomer is
known to damage the seal between the rotor and stator and
eventually to cause failure of the stator. As a result, such
degradation tends to reduce the life of the stator and necessitate
replacement thereof at undue frequency and cost.
[0004] U.S. Pat. No. 6,183,226 to Wood et al. (hereafter referred
to as the Wood patent) discloses a stator including areas of
composite material, which are intended to act as a supportive
structure for the helicoid interface of a rubber elastomer. The
Wood patent discloses a filament winding process for forming the
composite material, which results in the composite fibers being
substantially aligned with the helical grooves along the length of
the stator. Such aligning of the fibers likely increases the
internal stress in the composite material and thereby reduces its
overall strength. Further, such aligning of the fibers likely
results in anisotropic mechanical properties, i.e., a relatively
high strength along the length of the fibers and a relatively low
strength in transverse directions. Therefore, there exists a need
for improved composite design for progressing cavity stators and
improved methods of fabricating such composite stators.
SUMMARY OF THE INVENTION
[0005] The present invention addresses one or more of the
above-described drawbacks of prior art progressing cavity motors
and/or pumps. Referring briefly to the accompanying figures,
aspects of this invention include a progressing cavity stator for
use in a progressing cavity motor, such as in a downhole drilling
assembly. The progressing cavity stator includes a fiber reinforced
composite component having a plurality of helical lobes disposed
along the inner surface thereof. The composite component includes a
plurality of fibers disposed in a matrix material, such as a
theremosetting resin. The fibers are disposed in the composite
component such that distinct portions of the fibers follow
correspondingly distinct directions, which may be advantageously
intertwined. In alternate embodiments, this invention includes a
progressing cavity composite insert for use in a progressing cavity
stator. Methods for fabricating progressing cavity stators and
progressing cavity composite inserts are also provided.
[0006] Exemplary embodiments of the present invention
advantageously provide several technical advantages. Various
embodiments of the progressing cavity stator of this invention may
exhibit a prolonged service life as compared to conventional
progressing cavity stators. Tools embodying this invention may thus
display improved reliability and thereby provide for potentially
significant cost savings. Various embodiments of the fabrication
procedure may also provide for the fabrication of a replaceable
composite stator insert. Such a composite stator insert
advantageously promotes field service flexibility. For example,
damaged inserts may be replaced in the field at considerable
savings of time and expense. Alternatively, an existing insert may
be changed to one having, for example, a different number of lobes
to optimize power section performance to current needs (e.g., with
respect to speed and power).
[0007] In one aspect this invention includes a method for
fabricating a progressing cavity stator. The method includes
providing a first core having at least one helical groove on an
outer surface thereof and disposing a plurality of fibers in each
helical groove to form a fiber preform. The method also includes
inserting the fiber preform into a cylindrical tube, injecting a
resin into the cylindrical tube to form an impregnated fiber
preform, and removing the first core from the impregnated fiber
preform thereby forming an internal helical cavity in the
impregnated fiber preform. The method further includes inserting a
second core, having at least one helical groove on an outer surface
thereof, into the internal helical cavity of the impregnated fiber
preform, the second core having a smaller diameter than that of the
first core, thereby forming a substantially helical annulus between
the second core and the impregnated fiber preform, injecting an
elastomeric material into the helical annulus, and removing the
second core.
[0008] In another aspect this invention includes a progressing
cavity stator including a fiber reinforced composite component that
provides an internal helical cavity having at least one helical
groove and an elastomeric liner disposed on an internal surface of
the composite component. In certain exemplary embodiments, the
fiber reinforced composite component includes a plurality of fibers
disposed in a matrix material, the plurality of fibers disposed
such that distinct portions thereof follow correspondingly distinct
directions. In other exemplary embodiments, the elastomeric liner
includes a non-uniform thickness, the non-uniform thickness varying
in directions of at least one of parallel to a cylindrical axis of
the stator and radially about the cylindrical axis of the stator.
In still other exemplary embodiments, the combination of the fiber
reinforced composite component and the elastomeric liner form a
replaceable progressing cavity insert, of which the outer surface
is sized and shaped for removable receipt within a cylindrical
tube.
[0009] The foregoing has outlined rather broadly the features and
technical advantages of the present invention in order that the
detailed description of the invention that follows may be better
understood. Additional features and advantages of the invention
will be described hereinafter which form the subject of the claims
of the invention. It should be appreciated by those skilled in the
art that the conception and the specific embodiment disclosed may
be readily utilized as a basis for modifying or designing other
structures for carrying out the same purposes of the present
invention. It should also be realize by those skilled in the art
that such equivalent constructions do not depart from the spirit
and scope of the invention as set forth in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] For a more complete understanding of the present invention,
and the advantages thereof, reference is now made to the following
descriptions taken in conjunction with the accompanying drawings,
in which:
[0011] FIG. 1 is a schematic representation of an offshore oil
and/or gas drilling platform utilizing an exemplary embodiment of
the present invention.
[0012] FIG. 2 depicts a progressing cavity motor utilizing an
exemplary embodiment of the present invention.
[0013] FIG. 3 is a cross sectional view of one exemplary embodiment
of a progressing cavity stator according to this invention.
[0014] FIG. 4 is a cross sectional view as shown on FIG. 3.
[0015] FIG. 5, is a cross sectional view of another exemplary
embodiment of a progressing cavity stator according to this
invention.
[0016] FIG. 6 is a perspective, cut-away view of an exemplary
embodiment of a fiber preform used in the fabrication of various
embodiments of this invention.
[0017] FIG. 7 depicts one exemplary arrangement used in the
fabrication of various embodiments of this invention.
[0018] FIG. 8 is a cross sectional view of another arrangement used
in the fabrication of various embodiments of this invention.
[0019] FIG. 9 is a cross sectional view of yet another exemplary
embodiment of a progressing cavity stator according to this
invention.
[0020] FIG. 10 is a cross sectional view of still another exemplary
embodiment of a progressing cavity stator according to this
invention.
DETAILED DESCRIPTION
[0021] FIGS. 1 and 2 illustrate one exemplary embodiment of a
progressing cavity stator 100 according to this invention in use in
an offshore oil or gas drilling assembly, generally denoted 10 on
FIG. 1. In FIG. 1, a semisubmersible drilling platform 12 is
positioned over an oil or gas formation (not shown) disposed below
the sea floor 16. A subsea conduit 18 extends from deck 20 of
platform 12 to a wellhead installation 22. The platform may include
a derrick 26 and a hoisting apparatus 28 for raising and lowering
the drill string 30, which, as shown, extends into borehole 40 and
includes a progressing cavity motor 50 coupled to a drill bit
assembly 52. In FIG. 2, the progressing cavity motor 50 includes a
rotor 56 operational within a progressing cavity stator 100. As
described in more detail below, the stator 100 includes a fiber
reinforced composite component.
[0022] It will be understood by those of ordinary skill in the art
that the progressing cavity stator 100 of the present invention is
not limited to use with a semisubmersible platform 12 as
illustrated in FIG. 1. Progressing cavity stator 100 is equally
well suited for use with any kind of subterranean drilling and/or
pumping operation, either offshore or onshore. It will also be
understood that the progressing cavity stator of this invention is
not limited to downhole applications, but may be utilized in
substantially any application in which progressing cavity hydraulic
motors and/or pumps are used.
[0023] With reference now to FIGS. 3 and 4, one exemplary
embodiment of the progressing cavity stator 100 of this invention
includes an outer cylindrical member 102 (such as a steel tube),
which is typically couplable to a drill string when used for
downhole applications, an inner elastomeric layer 104, and a fiber
reinforced composite component 110 interposed between the
cylindrical member 102 and the elastomeric layer 104. The fiber
reinforced composite component 110 is shaped to define a plurality
of helical lobes 112 and grooves 114 on an inner surface 116
thereof. The fiber reinforced composite component 110 includes a
plurality of fibers disposed in a matrix material, such as a
theremosetting resin. The fibers are disposed in the composite
component 110 such that distinct portions of the fibers follow
correspondingly distinct directions. In certain embodiments,
distinct portions of the fibers may be advantageously intertwined.
The fibers may have substantially any suitable configuration, such
as fiber roving, woven and/or non-woven fibers, braided fibers,
fiber bundles, fiber bundles wrapped in a braided fiber sock,
stitched three-dimensional fabrics, combinations thereof, and the
like. The use of woven and/or braided fibers may be preferable for
some embodiments since such fiber configurations include distinct
intertwined fibers and/or fiber bundles that follow correspondingly
distinct directions. The use of such fiber configurations also
tends to result in a composite component having somewhat isotropic
mechanical properties, especially as compared to a composite
component in which the fibers are substantially aligned in one
direction (such as that formed in a typical filament winding
process, for example, as described in the Wood patent).
[0024] With further reference to FIGS. 3 and 4, it will be
appreciated that the composite component 110 may include short
strand fibers (e.g., chopped fibers). Such short strand fibers may
be blended, for example, with a suitable resin material and
injected into the lobe regions of the stator. Such a fabrication
procedure may include molding the composite component according to
known molding techniques and may advantageously result in a
composite having substantially isotropic mechanical properties. In
such embodiments it will be appreciated that the short strand
fibers, as dispersed in a matrix, are typically oriented in
substantially random directions so as to encourage isotropy.
[0025] With further reference to FIGS. 3 and 4, embodiments of the
composite component 110 may be fabricated from substantially any
fiber and matrix materials that are stable under downhole
conditions (e.g., up to about 200 degrees C. or more). For example,
desirable fibers may include glass fibers, carbon fibers, aramid
fibers, boron fibers, polyester fibers, polyethylene fibers,
combinations thereof, and the like. The matrix material is
typically formed from a combination of a thermosetting resin, such
as DER 331 epoxy resin, available from Dow Chemical Company,
Midland, Mich. or EPON 826 epoxy resin available from Resolution
Performance Products, and a hardener (or curing agent) such as
Amicure.RTM. PACM available from Air Products, Allentown, Pa. It
will be appreciated by those skilled in the art that various
optional modifiers and/or additives may be added to the epoxy resin
hardener blend. In a typical desirable embodiment, the composite
material includes various braided glass fibers disposed in an epoxy
resin matrix.
[0026] Referring now to FIG. 5, certain embodiments of the
progressing cavity stator 100' of this invention include a
composite stator insert 120 that is removable from an outer
cylindrical member 102' as shown at 131. In the event of
elastomeric degradation, for example, the composite stator insert
120 may be replaced in the field (e.g., at a drilling rig)
typically providing significant savings in time and expense. The
composite stator insert 120 (also referred to as a replaceable
composite stator) is similar to progressing cavity stator 100 on
FIGS. 3 and 4 in that it includes an elastomeric layer 104 disposed
on an inner surface of a composite component 110', which defines a
plurality of internal helical lobes 112 and grooves 114 as
described above. The composite stator insert 120 is coupleable to
an outer cylindrical member 102', for example, via a groove 122A
and corresponding key 122B machined into the composite component
110' and cylindrical member 102', respectively. The composite
stator insert 120 may alternatively (or additionally) be coupled to
outer cylindrical member 102' via a snap ring 124B and
corresponding groove 124A deployed on the insert 120 and
cylindrical member 102', respectively. It will be recognized that
composite stator insert 120 may also be coupled to cylindrical
member 102' by substantially other suitable arrangements, such as,
for example, by clamping, bonding via various adhesives, or press
fitting.
[0027] With continued reference to FIGS. 3 and 4 and further
reference to FIGS. 6 through 8, exemplary methods for fabricating
various embodiments of the composite stator of this invention are
described. FIG. 6 depicts, in cut away view, a fiber preform 150
used in the fabrication of a composite stator. A substantially
cylindrical core 152 is prepared (e.g., fabricated from a metallic
material such as a conventional carbon steel having a smooth
surface finish). It will be appreciated that the core 152 may be
substantially solid (e.g., formed from a solid bar) or include a
hollow interior along its longitudinal axis 155 (e.g., formed from
a tube). The core 152 includes at least one helical lobe 162 and
corresponding helical groove 164 formed in the outer wall 154
thereof. It will be appreciated that the core 152 may include
substantially any suitable number of helical lobes 162 and grooves
164 depending upon the requirements of the stator. Typical stators
include from 2 to about 10 or more helical lobes and corresponding
grooves, although the invention is not limited in this regard.
Various fibers are disposed in the helical grooves 164 and around
the outer wall 154 of the core 152. For example, in the exemplary
fiber preform 150 shown on FIG. 6, a braided fiber layer 172 is
disposed about the core 152. The helical grooves 164 of the core
152 are then partially or fully filled with one or more braided
fiber tubes (or ropes) 174. The braided fiber tubes 174 may be
secured in place (i.e., in the helical grooves 164), for example,
via circumferential fiber windings 176 and a second braided fiber
layer 178. Depending upon the depth of the helical lobes 164 and
the diameter of the braided fiber tubes 174, the fiber preform 150
may include several repeating layers of braided fiber tubes 174,
circumferential fiber windings 176, and braided fiber layers 178.
Fibers are typically applied to the fiber preform 150 until the
helical grooves 164 have been substantially filled and/or until the
fiber preform 150 attains some predetermined thickness.
Alternatively, a custom braided fiber strand having a profile
(cross section) similar to that of the helical grooves in the core
may be utilized. Such a custom braided fiber rope may be
advantageous in that the helical groove in the core (e.g., groove
164 in core 152) will be effectively completely filled with fiber
material. In another alternative embodiment, an impregnated fiber
composite strand having a profile similar to that of the helical
groove may be utilized. Such a fiber composite strand may be
formed, for example, via a conventional pultrusion process in which
impregnated fibers are pulled through a heated die.
[0028] With continued reference to FIGS. 6 through 8, the fiber
preform 150 may be inserted into a steel tube 180 (e.g.,
cylindrical member 102 in FIG. 3). In one exemplary fabrication
method shown in FIG. 7, the ends of the tube are sealed with
appropriate end fittings 182 and 183 having various ports 184 and
185 disposed therein. A liquid thermosetting resin, such as Dow
Chemical DER 331 epoxy resin, is injected into the tube 180, for
example, via port 185, to substantially impregnate the fibers and
displace any air in the tube 180. The artisan of ordinary skill
will readily recognize that substantially any suitable injection
method may be utilized, such as conventional resin transfer molding
and/or various known vacuum molding techniques (e.g., by evacuating
the tube 180 at port 185). Vacuum techniques are typically
desirable, as they tend to promote air displacement. Upon
completion of the injection procedure, the ports 184 and 185 are
sealed and the tube 180 may be heated to cure the resin. Such
impregnation of the fibers and subsequent curing results in a solid
fiber reinforced composite material. After curing of the resin, the
core 152 (FIG. 6) is extracted from the fiber reinforced composite
material resulting in a composite component having an internal
helicoid cavity (e.g., composite component 110 on FIGS. 3 and 4).
The core 152 may be treated with a mold release, such as honey wax
mold release, to promote such extraction.
[0029] After removal of the core 152 (FIG. 6), the inner surface
116' of the composite component 110' (FIG. 8) may be prepared by
one of numerous techniques, including cleaning with various
solvents and/or metal blasting and/or abrading techniques. Such
preparation of the inner surface 116' of the composite component
110" is intended to promote adhesion of an elastomeric material to
the composite component 110". A second core 192, having a smaller
outer diameter than core 152, is then inserted substantially
coaxially into the cavity of the composite component 110". An
elastomeric material (e.g., rubber) is injected into the helical
annulus 194 between the second core 192 and the composite component
110'. After curing of the elastomeric material, the second core 192
is removed from the stator, which is subsequently ready for final
machining or other finishing operations (if required). The second
core 192 may also be treated with a mold release to promote such
extraction.
[0030] With continued reference to FIGS. 6 through 8, a similar
procedure may be utilized to fabricate a composite stator insert
(such as composite stator insert 120 shown in FIG. 5). A fiber
preform may be formed and impregnated as described above with
respect to FIGS. 6 and 7. The impregnated fiber preform (e.g.,
fiber preform 150 after resin impregnation) is removed from tube
180 after curing of the resin. This may be accomplished, for
example, by treating the inner surface of the tube 180 with mold
release to substantially prevent the impregnated fiber preform from
bonding to the tube 180. The interior surface of the impregnated
fiber preform may then be prepared and an elastomeric layer
disposed thereon, for example, as described above with respect to
FIG. 8. Alternatively, the impregnated fiber preform may be removed
from tube 180 after injection and curing of the elastomeric layer.
After removal from the tube 180, the outer surface of the
impregnated fiber preform may be machined, for example, to form a
key (e.g., groove 122A shown on FIG. 5) and/or for final sizing and
shaping (e.g., to accommodate press fitting of the insert into a
stator tube).
[0031] Turning now to FIG. 9, another exemplary embodiment of a
progressing cavity stator 200 is shown. Stator 200 is similar to
stator 100 shown in FIGS. 3 and 4, in that it includes a fiber
reinforced composite component 210 interposed between an inner
elastomeric layer 204 and an outer cylindrical member 102. Stator
200 differs from stator 100 in that the composite component 210 and
the elastomeric layer 204 are tapered along the longitudinal axis
205 of the stator 200. In the embodiment shown on FIG. 9, the
radial thickness 222 of elastomeric layer 204 increases from the
top 201 to the bottom 202 of the stator 200, while the radial
thickness 224 of the composite component 210 (e.g., at lobes 212)
decreases from the top 201 to the bottom 202 of the stator 200,
such that internal radial dimensions 226 and 228 remain unchanged
along the longitudinal axis 205 of the stator 200. It will be
appreciated that stator composite component 210 and the elastomeric
layer 204 may include substantially any taper and that internal
radial dimensions 226 and 228 may also vary along the longitudinal
axis. For example, radial thicknesses 222 and 224 may increase
together along the longitudinal axis 205 from the top 201 to the
bottom 202 of the stator 200. Alternatively, the radial thickness
222 of the elastomeric layer 204 may vary along the longitudinal
axis 205, while that of the composite component 210 remains
substantially unchanged. Terms used in this disclosure, such as
"top" and "bottom", are intended merely to show relative positional
relationships of various components and are not limiting of the
invention in any way.
[0032] With continued reference to FIG. 9, stator 200 may be
advantageous for various downhole drilling applications in that
having a relatively thicker elastomeric layer 204 at the bottom 202
of the stator 200 provides increased flexibility to absorb loads
induced by the eccentric path of the rotor while having a
relatively thinner elastomeric layer 204 at the top 201 of the
stator 200 increases rigidity and therefore increasing the output
torque of the progressing cavity motor.
[0033] With reference now to FIG. 10, still another exemplary
embodiment of a progressing cavity stator 300 is shown. Stator 300
is similar to stator 100 shown in FIGS. 3 and 4, in that it
includes a fiber reinforced composite component 310 interposed
between an inner elastomeric layer 304 and an outer cylindrical
member 102. Stator 300 differs from stator 100 in that the radial
thickness 322 of the elastomeric layer 304 varies circumferentially
about the stator 300. Such a variation in the radial thickness 322
may advantageously be periodic (e.g., radially symmetric about a
cylindrical axis (not shown in FIG. 10) of the stator). The
composite lobes 312 may be shaped to accommodate the varying radial
thickness 322 of the elastomeric layer such that the shape of the
internal cavity 305 in stator 300 is substantially identical to
that of the internal cavity of stator 100. Alternatively, the
second core 192 (FIG. 8) may be skewed slightly with respect to the
impregnated fiber preform thereby resulting in the formation of an
uneven elastomer layer around each lobe of the composite. Stator
300 may be advantageous for certain applications in that regions of
the stator that are subject to higher stresses (e.g., the leading
edge of the lobes) may include a relatively thicker elastomeric
layer.
[0034] Progressing cavity stators 200 and 300 may be fabricated
using a similar procedure to that described above with respect to
FIGS. 6 through 8. In the fabrication of embodiments of stator 100
(using the procedure described above with respect to FIGS. 6
through 8) the first 152 and second 192 cores have substantially
the same profiles (i.e., the shape of the lobes and grooves are
substantially the same). The primary difference between the two
cores is that the second core 192 has a smaller diameter than the
first core 152. Thus the thickness of the elastomeric layer 104
(FIGS. 3 and 4) is substantially uniform and substantially equal to
the difference between the two diameters. In such a manufacturing
procedure, the use of cores having different profiles generally
results in an elastomeric layer with a non-uniform thickness. For
example, stator 200 may be fabricated using a tapered first core
(i.e., a core in which the outer diameter increases from one end to
the other). Such a tapered core results in a composite component
having a tapered inner diameter. The use of a second core having a
uniform outer diameter then results in a stator in which the
thickness of the elastomeric layer increases along the cylindrical
axis. Similarly stator 300 may be fabricated, for example, using a
first core in which the shapes of the lobes and/or grooves differ
from that of the second core. The artisan of ordinary skill will
readily recognize that the above described procedure advantageously
permits fabrication of stators having substantially any variation
in the thickness of the elastomeric layer and/or the composite
component.
[0035] Although the present invention and its advantages have been
described in detail, it should be understood that various changes,
substitutions and alternations can be made herein without departing
from the spirit and scope of the invention as defined by the
appended claims.
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