U.S. patent application number 14/553421 was filed with the patent office on 2016-05-26 for flexible graphite packer.
This patent application is currently assigned to BAKER HUGHES INCORPORATED. The applicant listed for this patent is Zhiyue Xu, Lei Zhao. Invention is credited to Zhiyue Xu, Lei Zhao.
Application Number | 20160145965 14/553421 |
Document ID | / |
Family ID | 56009687 |
Filed Date | 2016-05-26 |
United States Patent
Application |
20160145965 |
Kind Code |
A1 |
Zhao; Lei ; et al. |
May 26, 2016 |
FLEXIBLE GRAPHITE PACKER
Abstract
A packer includes a structure having a first part and a second
part, and a plurality of flexible carbon composite particles
arranged between the first and second parts.
Inventors: |
Zhao; Lei; (Houston, TX)
; Xu; Zhiyue; (Cypress, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Zhao; Lei
Xu; Zhiyue |
Houston
Cypress |
TX
TX |
US
US |
|
|
Assignee: |
BAKER HUGHES INCORPORATED
Houston
TX
|
Family ID: |
56009687 |
Appl. No.: |
14/553421 |
Filed: |
November 25, 2014 |
Current U.S.
Class: |
166/387 ;
166/196 |
Current CPC
Class: |
E21B 33/128 20130101;
E21B 33/1208 20130101 |
International
Class: |
E21B 33/128 20060101
E21B033/128; E21B 23/06 20060101 E21B023/06 |
Claims
1. A packer comprising: a structure including a first part and a
second part; and a plurality of flexible carbon composite particles
arranged between the first and second parts.
2. The packer according to claim 1, further comprising: a flexible
membrane extending between the first and second parts.
3. The packer according to claim 2, wherein the flexible membrane
is formed from a woven material.
4. The packer according to claim 3, wherein the woven material
includes one or more of a carbon fiber; a metal wire; an asbestos
material; a metal fiber; or a flexible graphite fiber.
5. The packer according to claim 2, wherein the flexible membrane
is formed from a degradable material.
6. The packer according to claim 5, wherein the degradable material
comprises a polymer fiber.
7. The packer according to claim 2, wherein the flexible membrane
comprises a tube, the plurality of carbon composite particles being
encased in the tube.
8. A subsurface exploration system comprising: an uphole system; a
downhole system operatively connected to the uphole system, the
downhole system including a downhole string having at least one
mandrel; and a packer supported on the at least one mandrel, the
packer comprising: a structure including a first part and a second
part; and a plurality of flexible carbon composite particles
arranged between the first and second parts.
9. The resource exploration system according to claim 8, further
comprising: a flexible membrane extending between the first and
second parts.
10. The subsurface exploration system according to claim 9, wherein
the flexible membrane is formed from a woven material.
11. The subsurface exploration system according to claim 10,
wherein the woven material includes one or more of a carbon fiber;
a metal wire; an asbestos material; a metal fiber; or a flexible
graphite fiber.
12. The subsurface exploration system according to claim 9, wherein
the flexible membrane is formed from a degradable material.
13. The subsurface exploration system according to claim 12,
wherein the degradable material comprises a polymer fiber.
14. The subsurface exploration system according to claim 9, wherein
the flexible membrane comprises a tube arranged in a coil extending
about the at least one tubular, the plurality of flexible carbon
composite particles being encased in the tube.
15. A method of setting a packer comprising: positioning a packer
including a metal structure including first and second parts onto a
mandrel; shifting at least one of the first and second parts
towards another of the first and second parts to compress a
plurality of flexible carbon composite particles; urging the
plurality of flexible carbon composite particles outwardly of the
first and second parts; and guiding the plurality of flexible
carbon composite particles towards a wellbore casing.
16. The method of claim 15, further comprising: constraining the
plurality of flexible carbon composite particles between the first
and second parts with a flexible membrane.
17. The method of claim 15, wherein urging the plurality of
flexible carbon composite particles outwardly of the first and
second parts includes expanding the flexible membrane.
18. The method of claim 16, wherein constraining the plurality of
flexible carbon composite particles between the first and second
parts with the flexible membrane includes positioning a flexible
membrane formed from one of a woven material and a degradable
material between the first and second parts.
19. The method of claim 15, wherein guiding the plurality of
flexible carbon composite particles toward the wellbore casing
includes shifting the first and second parts along an angled
surface section of the mandrel.
20. The method of claim 15, wherein guiding the plurality of
flexible carbon composite particles toward the wellbore casing
includes compressing the plurality of flexible carbon composite
particles encased in a hollow tube formed by the flexible membrane
coiled about the mandrel.
Description
BACKGROUND
[0001] Graphite is an allotrope of carbon and has a layered, planar
structure. In each layer, the carbon atoms are arranged in
hexagonal arrays or networks through covalent bonds. Different
carbon layers however are held together only by weak van der Waals
forces.
[0002] Graphite has been used in a variety of applications
including electronics, atomic energy, hot metal processing,
coatings, aerospace and the like due to its excellent thermal and
electrical conductivities, lightness, low friction, and high heat
and corrosion resistances. However, conventional graphite is not
elastic and has low strength, which may limit its further
applications such as forming packers employed in a downhole
environment.
[0003] Packers are used for securing production tubing inside of
casing or a liner within a borehole, for example. Packers are also
used to create separate zones within a borehole. A packer may take
the form of a flexible member mounted to a rigid support body, and
carried by a conveyance tubular (such as a production tubing
string) downhole to a desired position. The packer is then set or
expanded, within an annular space between the conveyance tubular
and the outer tubing, casing, or open-hole, and held in place by a
packer containment system. The industry would be receptive to
improvements in packer technology including a packer formed from a
material exhibiting enhanced flexibility, chemical stability,
corrosive resistance, as well as high temperature and high pressure
resistance properties.
SUMMARY
[0004] A packer includes a structure having a first part and a
second part, and a plurality of flexible carbon composite particles
arranged between the first and second parts.
[0005] A subsurface exploration system includes an uphole system
and a downhole system operatively connected to the uphole system.
The downhole system includes a downhole string having at least one
tubular. A packer is supported on the at least one mandrel. The
packer includes a structure having a first part and a second part,
and a plurality of flexible carbon composite particles arranged
between the first and second parts.
[0006] A method of setting a packer includes positioning a packer
including a metal structure having first and second parts onto a
mandrel, shifting at least one of the first and second parts
towards another of the first and second parts to compress a
plurality of flexible carbon composite particles, urging the
plurality of flexible carbon composite particles outwardly of the
first and second parts, and guiding the plurality of flexible
carbon composite particles towards a wellbore casing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Referring now to the drawings wherein like elements are
numbered alike in the several Figures:
[0008] FIG. 1 is a scanning electron microscopic ("SEM") image of a
composition containing expanded graphite and a micro- or nano-sized
binder blended at room temperature and atmospheric pressure;
[0009] FIG. 2 is a SEM image of a carbon composite formed from
expanded graphite and a micro- or nano-sized binder under high
pressure and high temperature conditions according to one
embodiment of the disclosure;
[0010] FIG. 3 is a SEM image of carbon microstructures according to
another embodiment of the disclosure;
[0011] FIG. 4 is a schematic illustration of a carbon composite
according to an embodiment of the disclosure;
[0012] FIG. 5 shows stress-strain curves of (A) natural graphite;
(B) expanded graphite; (C) a mixture of expanded graphite and a
micro- or nano-sized binder, where the sample is compacted at room
temperature and high pressure; (D) a carbon composite according to
one embodiment of the disclosure compacted from a mixture of
expanded graphite and a micro- or nano-sized binder at a high
temperature and a low pressure (also referred to as "soft
composite"); and (E) a carbon composite according to another
embodiment of the disclosure formed from expanded graphite and a
micro- and nano-sized binder under high pressure and high
temperature conditions (also referred to as "hard composite");
[0013] FIG. 6 shows loop test results of a carbon composite at
different loadings;
[0014] FIG. 7 shows hysteresis results of a carbon composite tested
at room temperature and 500.degree. F. respectively;
[0015] FIG. 8 compares a carbon composite before and after exposing
to air at 500.degree. C. for 25 hours;
[0016] FIG. 9(A) is a photo of a carbon composite after a thermal
shock; FIG. 9(B) illustrates the condition for the thermal
shock;
[0017] FIG. 10 compares a carbon composite sample (A) before and
(B) after exposing to tap water for 20 hours at 200.degree. F., or
(C) after exposing to tap water for 3 days at 200.degree. F.;
[0018] FIG. 11 compares a carbon composite sample (A) before and
(B) after exposing to 15% HCl solution with inhibitor at
200.degree. F. for 20 hours, or (C) after exposing to 15% HCl
solution at 200.degree. F. for 3 days;
[0019] FIG. 12 shows the sealing force relaxation test results of a
carbon composite at 600.degree. F.;
[0020] FIG. 13 depicts a subsurface exploration system including a
tubular supporting a flexible graphite packer, in accordance with
an exemplary embodiment;
[0021] FIG. 14 depicts a partial cross-sectional view of the packer
of FIG. 1, in accordance with an aspect of an exemplary
embodiment;
[0022] FIG. 15 depicts a partial cross-sectional view of the packer
of FIG. 14 illustrating compression of a metal structure;
[0023] FIG. 16 depicts a partial cross-sectional view of the packer
of FIG. 15 shifting along the tubular engaging with a wellbore
casing;
[0024] FIG. 17 depicts a partial cross-sectional view of the packer
of FIG. 16 engaged with the wellbore casing;
[0025] FIG. 18 depicts a plan view of a packer, in accordance with
another aspect of an exemplary embodiment, in an un-deployed
configuration; and
[0026] FIG. 19 depicts a plan view of a packer of FIG. 17 in a
deployed configuration.
DETAILED DESCRIPTION
[0027] The inventors hereof have found that carbon composites
formed from graphite and micro- or nano-sized binders at high
temperatures have improved balanced properties as compared to
graphite alone, a composition formed from the same graphite but
different binders, or a mixture of the same graphite and the same
binder blended at room temperature under atmospheric pressure or
high pressures. The new carbon composites have excellent
elasticity. In addition, the carbon composites have excellent
mechanical strength, heat resistance, and chemical resistance at
high temperatures. In a further advantageous feature, the
composites keep various superior properties of the graphite such as
heat conductivity, electrical conductivity, lubricity, and the
alike.
[0028] Without wishing to be bound by theory, it is believed that
the improvement in mechanical strength is provided by a binding
phase disposed between carbon microstructures. There are either no
forces or only weak Van der Waals forces exist between the carbon
microstructures thus the graphite bulk materials have weak
mechanical strength. At high temperatures, the micro- and
nano-sized binder liquefies and is dispersed evenly among carbon
microstructures. Upon cooling, the binder solidifies and forms a
binding phase binding the carbon nanostructures together through
mechanical interlocking.
[0029] Further without wishing to be bound by theory, for the
composites having both improved mechanical strength and improved
elasticity, it is believed that the carbon microstructures
themselves are laminar structures having spaces between the stacked
layers. The binder only selectively locks the microstructures at
their boundaries without penetrating the microstructures. Thus the
unbounded layers within the microstructures provide elasticity and
the binding phase disposed between the carbon microstructures
provides mechanical strength.
[0030] The carbon microstructures are microscopic structures of
graphite formed after compressing graphite into highly condensed
state. They comprise graphite basal planes stacked together along
the compression direction. As used herein, carbon basal planes
refer to substantially flat, parallel sheets or layers of carbon
atoms, where each sheet or layer has a single atom thickness. The
graphite basal planes are also referred to as carbon layers. The
carbon microstructures are generally flat and thin. They can have
different shapes and can also be referred to as micro-flakes,
micro-discs and the like. In an embodiment, the carbon
microstructures are substantially parallel to each other.
[0031] There are two types of voids in the carbon composites--voids
or interstitial spaces between carbon microstructures and voids
within each individual carbon microstructures. The interstitial
spaces between the carbon microstructures have a size of about 0.1
to about 100 microns, specifically about 1 to about 20 microns
whereas the voids within the carbon microstructures are much
smaller and are generally between about 20 nanometers to about 1
micron, specifically about 200 nanometers to about 1 micron. The
shape of the voids or interstitial spaces is not particularly
limited. As used herein, the size of the voids or interstitial
spaces refers to the largest dimension of the voids or interstitial
spaces and can be determined by high resolution electron or atomic
force microscope technology.
[0032] The interstitial spaces between the carbon microstructures
are filled with a micro- or nano-sized binder. For example, a
binder can occupy about 10% to about 90% of the interstitial spaces
between the carbon microstructures. However, the binder does not
penetrate the individual carbon microstructures and the voids
within carbon microstructures are unfilled, i.e., not filled with
any binder. Thus the carbon layers within the carbon
microstructures are not locked together by a binder. Through this
mechanism, the flexibility of the carbon composite, particularly,
expanded carbon composite can be preserved.
[0033] The carbon microstructures have a thickness of about 1 to
about 200 microns, about 1 to about 150 microns, about 1 to about
100 microns, about 1 to about 50 microns, or about 10 to about 20
microns. The diameter or largest dimension of the carbon
microstructures is about 5 to about 500 microns or about 10 to
about 500 microns. The aspect ratio of the carbon microstructures
can be about 10 to about 500, about 20 to about 400, or about 25 to
about 350. In an embodiment, the distance between the carbon layers
in the carbon microstructures is about 0.3 nanometers to about 1
micron. The carbon microstructures can have a density of about 0.5
to about 3 g/cm.sup.3, or about 0.1 to about 2 g/cm.sup.3.
[0034] As used herein, graphite includes natural graphite,
synthetic graphite, expandable graphite, expanded graphite, or a
combination comprising at least one of the foregoing. Natural
graphite is graphite formed by Nature. It can be classified as
"flake" graphite, "vein" graphite, and "amorphous" graphite.
Synthetic graphite is a manufactured product made from carbon
materials. Pyrolytic graphite is one form of the synthetic
graphite. Expandable graphite refers to graphite having
intercallant materials inserted between layers of natural graphite
or synthetic graphite. A wide variety of chemicals have been used
to intercalate graphite materials. These include acids, oxidants,
halides, or the like. Exemplary intercallant materials include
sulfuric acid, nitric acid, chromic acid, boric acid, SO.sub.3, or
halides such as FeCl.sub.3, ZnCl.sub.2, and SbCl.sub.5. Upon
heating, the intercallant is converted from a liquid or solid state
to a gas phase. Gas formation generates pressure which pushes
adjacent carbon layers apart resulting in expanded graphite. The
expanded graphite particles are vermiform in appearance, and are
therefore commonly referred to as worms.
[0035] Advantageously, the carbon composites comprise expanded
graphite microstructures. Compared with other forms of the
graphite, expanded graphite has high flexibility and compression
recovery, and larger anisotropy. The composites formed from
expanded graphite and micro- or nano-sized binder under high
pressure and high temperature conditions can thus have excellent
elasticity in addition to desirable mechanical strength.
[0036] In the carbon composites, the carbon microstructures are
held together by a binding phase. The binding phase comprises a
binder which binds carbon microstructures by mechanical
interlocking. Optionally, an interface layer is formed between the
binder and the carbon microstructures. The interface layer can
comprise chemical bonds, solid solutions, or a combination thereof.
When present, the chemical bonds, solid solutions, or a combination
thereof may strengthen the interlocking of the carbon
microstructures. It is appreciated that the carbon microstructures
may be held together by both mechanical interlocking and chemical
bonding. For example the chemical bonding, solid solution, or a
combination thereof may be formed between some carbon
microstructures and the binder or for a particular carbon
microstructure only between a portion of the carbon on the surface
of the carbon microstructure and the binder. For the carbon
microstructures or portions of the carbon microstructures that do
not form a chemical bond, solid solution, or a combination thereof,
the carbon microstructures can be bounded by mechanical
interlocking. The thickness of the binding phase is about 0.1 to
about 100 microns or about 1 to about 20 microns. The binding phase
can form a continuous or discontinuous network that binds carbon
microstructures together.
[0037] Exemplary binders include SiO.sub.2, Si, B, B.sub.2O.sub.3,
a metal, an alloy, or a combination comprising at least one of the
foregoing. The metal can be aluminum, copper, titanium, nickel,
tungsten, chromium, iron, manganese, zirconium, hafnium, vanadium,
niobium, molybdenum, tin, bismuth, antimony, lead, cadmium, and
selenium. The alloy includes the alloys of aluminum, copper,
titanium, nickel, tungsten, chromium, iron, manganese, zirconium,
hafnium, vanadium, niobium, molybdenum, tin, bismuth, antimony,
lead, cadmium, and selenium. In an embodiment, the binder comprises
copper, nickel, chromium, iron, titanium, an alloy of copper, an
alloy of nickel, an alloy of chromium, an alloy of iron, an alloy
of titanium, or a combination comprising at least one of the
foregoing metal or metal alloy. Exemplary alloys include steel,
nickel-chromium based alloys such as Inconel*, and nickel-copper
based alloys such as Monel alloys. Nickel-chromium based alloys can
contain about 40-75% of Ni, about 10-35% of Cr. The nickel-chromium
based alloys can also contain about 1 to about 15% of iron. Small
amounts of Mo, Nb, Co, Mn, Cu, Al, Ti, Si, C, S, P, B, or a
combination comprising at least one of the foregoing can also be
included in the nickel-chromium based alloys. Nickel-copper based
alloys are primarily composed of nickel (up to about 67%) and
copper. The nickel-copper based alloys can also contain small
amounts of iron, manganese, carbon, and silicon. These materials
can be in different shapes, such as particles, fibers, and wires.
Combinations of the materials can be used.
[0038] The binder used to make the carbon composite is micro- or
nano-sized. In an embodiment, the binder has an average particle
size of about 0.05 to about 10 microns, specifically, about 0.5 to
about 5 microns, more specifically about 0.1 to about 3 microns.
Without wishing to be bound by theory, it is believed that when the
binder has a size within these ranges, it disperses uniformly among
the carbon microstructures.
[0039] When an interface layer is present, the binding phase
comprises a binder layer comprising a binder and an interface layer
bonding one of the at least two carbon microstructures to the
binder layer. In an embodiment, the binding phase comprises a
binder layer, a first interface layer bonding one of the carbon
microstructures to the binder layer, and a second interface layer
bonding the other of the microstructures to the binder layer. The
first interface layer and the second interface layer can have the
same or different compositions.
[0040] The interface layer comprises a C-metal bond, a C--B bond, a
C--Si bond, a C--O--Si bond, a C--O-metal bond, a metal carbon
solution, or a combination comprising at least one of the
foregoing. The bonds are formed from the carbon on the surface of
the carbon microstructures and the binder.
[0041] In an embodiment, the interface layer comprises carbides of
the binder. The carbides include carbides of aluminum, titanium,
nickel, tungsten, chromium, iron, manganese, zirconium, hafnium,
vanadium, niobium, molybdenum, or a combination comprising at least
one of the foregoing. These carbides are formed by reacting the
corresponding metal or metal alloy binder with the carbon atoms of
the carbon microstructures. The binding phase can also comprise SiC
formed by reacting SiO.sub.2 or Si with the carbon of carbon
microstructures, or B.sub.4C formed by reacting B or B.sub.2O.sub.3
with the carbon of the carbon microstructures. When a combination
of binder materials is used, the interface layer can comprise a
combination of these carbides. The carbides can be salt-like
carbides such as aluminum carbide, covalent carbides such as SiC,
B.sub.4C, interstitial carbides such as carbides of the group 4, 5,
and 5 transition metals, or intermediate transition metal carbides,
for example the carbides of Cr, Mn, Fe, Co, and Ni.
[0042] In another embodiment, the interface layer comprises a solid
solution of carbon and the binder. Carbon have solubility in
certain metal matrix or at certain temperature range, which helps
both wetting and binding of metal phase onto carbon
microstructures. Through heat-treatment, high solubility of carbon
in metal can be maintained at low temperature. These metals include
Co, Fe, La, Mn, Ni, or Cu. The binder layer can also comprises a
combination of solid solutions and carbides.
[0043] The carbon composites comprise about 20 to about 95 wt. %,
about 20 to about 80 wt. %, or about 50 to about 80 wt. % of
carbon, based on the total weight of the composites. The binder is
present in an amount of about 5 wt. % to about 75 wt. % or about 20
wt. % to about 50 wt. %, based on the total weight of the
composites. In the carbon composites, the weight ratio of carbon
relative to the binding is about 1:4 to about 20:1, or about 1:4 to
about 4:1, or about 1:1 to about 4:1.
[0044] FIG. 1 is a SEM image of a composition containing expanded
graphite and a micro- or nano-sized binder blended at room
temperature and atmospheric pressure. As shown in FIG. 1, the
binder (white area) is only deposited on the surface of some of the
expanded graphite worms.
[0045] FIG. 2 is a SEM image of a carbon composite formed from
expanded graphite and a micro- or nano-sized binder under high
pressure and high temperature conditions. As shown in FIG. 2, a
binding phase (light area) is evenly distributed between the
expanded graphite microstructures (dark area).
[0046] A SEM image of carbon graphite microstructures are shown in
FIG. 3. An embodiment of a carbon composite is illustrated in FIG.
4. As shown in FIG. 4, the composite comprises carbon
microstructures 1 and binding phase 2 locking the carbon
microstructures. The binding phase 2 comprises binder layer 3 and
an optional interface layer 4 disposed between the binder layer and
the carbon microstructures. The carbon composite contains
interstitial space 5 among carbon microstructures 1. Within carbon
microstructures, there are unfilled voids 6.
[0047] The carbon composites can optionally comprise a filler.
Exemplary filler includes carbon fibers, carbon black, mica, clay,
glass fiber, ceramic fibers, and ceramic hollow structures. Ceramic
materials include SiC, Si.sub.3N.sub.4, SiO.sub.2, BN, and the
like. The filler can be present in an amount of about 0.5 to about
10 wt. % or about 1 to about 8%.
[0048] The composites can have any desired shape including a bar,
block, sheet, tubular, cylindrical billet, toroid, powder, pellets,
or other form that may be machined, formed or otherwise used to
form useful articles of manufacture. The sizes or the dimension of
these forms are not particularly limited. Illustratively, the sheet
has a thickness of about 10 .mu.m to about 10 cm and a width of
about 10 mm to about 2 m. The powder comprises particles having an
average size of about 10 .mu.m to about 1 cm. The pellets comprise
particles having an average size of about 1 cm to about 5 cm.
[0049] One way to form the carbon composites is to compress a
combination comprising carbon and a micro- or nano-sized binder to
provide a green compact by cold pressing; and to compressing and
heating the green compact thereby forming the carbon composites. In
another embodiment, the combination can be pressed at room
temperature to form a compact, and then the compact is heated at
atmospheric pressure to form the carbon composite. These processes
can be referred to as two-step processes. Alternatively, a
combination comprising carbon and a micro- or nano-sized binder can
be compressed and heated directly to form the carbon composites.
The process can be referred to as a one-step process.
[0050] In the combination, the carbon such as graphite is present
in an amount of about 20 wt. % to about 95 wt. %, about 20 wt. % to
about 80 wt. %, or about 50 wt. % to about 80 wt. %, based on the
total weight of the combination. The binder is present in an amount
of about 5 wt. % to about 75 wt. % or about 20 wt. % to about 50
wt. %, based on the total weight of the combination. The graphite
in the combination can be in the form of chip, powder, platelet,
flake, or the like. In an embodiment, the graphite is in the form
of flakes having a diameter of about 50 microns to about 5,000
microns, preferably about 100 to about 300 microns. The graphite
flakes can have a thickness of about 1 to about 5 microns. The
density of the combination is about 0.01 to about 0.05 g/cm.sup.3,
about 0.01 to about 0.04 g/cm.sup.3, about 0.01 to about 0.03
g/cm.sup.3 or about 0.026 g/cm.sup.3. The combination can be formed
by blending the graphite and the micro- or nano-sized binder via
any suitable methods known in the art. Examples of suitable methods
include ball mixing, acoustic mixing, ribbon blending, vertical
screw mixing, and V-blending.
[0051] Referring to the two-step process, cold pressing means that
the combination comprising the graphite and the micro-sized or
nano-sized binder is compressed at room temperature or at an
elevated temperature as long as the binder does not significantly
bond with the graphite microstructures. In an embodiment, greater
than about 80 wt. %, greater than about 85 wt. %, greater than
about 90 wt. %, greater than about 95 wt. %, or greater than about
99 wt. % of the microstructures are not bonded in the green
compact. The pressure to form the green compact can be about 500
psi to about 10 ksi and the temperature can be about 20.degree. C.
to about 200.degree. C. The reduction ratio at this stage, i.e.,
the volume of the green compact relative to the volume of the
combination, is about 40% to about 80%. The density of the green
compact is about 0.1 to about 5 g/cm.sup.3, about 0.5 to about 3
g/cm.sup.3, or about 0.5 to about 2 g/cm.sup.3.
[0052] The green compact can be heated at a temperature of about
350.degree. C. to about 1200.degree. C., specifically about
800.degree. C. to about 1200.degree. C. to form the carbon
composites. In an embodiment, the temperature is above the melting
point of the binder, for example, about 20.degree. C. to about
100.degree. C. higher or about 20.degree. C. to about 50.degree. C.
higher than the melting point of the binder. When the temperature
is higher, the binder becomes less viscose and flows better, and
less pressure may be required in order for the binder to be evenly
distributed in the voids between the carbon microstructures.
However, if the temperature is too high, it may have detrimental
effects to the instrument.
[0053] The temperature can be applied according to a predetermined
temperature schedule or ramp rate. The means of heating is not
particularly limited. Exemplary heating methods include direct
current (DC) heating, induction heating, microwave heating, and
spark plasma sintering (SPS). In an embodiment, the heating is
conducted via DC heating. For example, the combination comprising
the graphite and the micro- or nano-sized binder can be charged
with a current, which flows through the combination generating heat
very quickly. Optionally, the heating can also be conducted under
an inert atmosphere, for example, under argon or nitrogen. In an
embodiment, the green compact is heated in the presence of air.
[0054] The heating can be conducted at a pressure of about 500 psi
to about 30,000 psi or about 1000 psi to about 5000 psi. The
pressure can be a superatmospheric pressure or a subatmospheric
pressure. Without wishing to be bound by theory, it is believed
that when a superatmospheric pressure is applied to the
combination, the micro- or nano-sized binder is forced into the
voids between carbon microstructures through infiltration. When a
subatmospheric pressure is applied to the combination, the micro-
or nano-sized binder can also be forced into the voids between the
carbon microstructures by capillary forces.
[0055] In an embodiment, the desirable pressure to form the carbon
composites is not applied all at once. After the green compact is
loaded, a low pressure is initially applied to the composition at
room temperature or at a low temperature to close the large pores
in the composition. Otherwise, the melted binder may flow to the
surface of the die. Once the temperature reaches the predetermined
maximum temperature, the desirable pressure required to make the
carbon composites can be applied. The temperature and the pressure
can be held at the predetermined maximum temperature and the
predetermined maximum temperature for 5 minutes to 120 minutes.
[0056] The reduction ratio at this stage, i.e. the volume of the
carbon composite relative to the volume of the green compact, is
about 10% to about 70% or about 20 to about 40%. The density of the
carbon composite can be varied by controlling the degree of
compression. The carbon composites have a density of about 0.5 to
about 10 g/cm.sup.3, about 1 to about 8 g/cm.sup.3, about 1 to
about 6 g/cm.sup.3, about 2 to about 5 g/cm.sup.3, about 3 to about
5 g/cm.sup.3, or about 2 to about 4 g/cm.sup.3.
[0057] Alternatively, also referring to a two-step process, the
combination can be first pressed at room temperature and a pressure
of about 500 psi to 30,000 psi to form a compact; the compact can
be further heated at a temperature higher than the melting point of
the binder to make the carbon composite. In an embodiment, the
temperature can be about 20.degree. C. to about 100.degree. C.
higher or about 20.degree. C. to about 50.degree. C. higher than
the melting point of the binder. The heating can be conducted at
atmospheric pressure.
[0058] In another embodiment, the carbon composite can be made from
the combination of the graphite and the binder directly without
making the green compact. The pressing and the heating can be
carried out simultaneously. Suitable pressures and temperatures can
be the same as discussed herein for the second step of the two-step
process.
[0059] Hot pressing is a process that applies temperature and
pressure simultaneously. It can be used in both the one-step and
the two-step processes to make carbon composites.
[0060] The carbon composites can be made in a mold through a
one-step or a two-step process. The obtained carbon composites can
be further machined or shaped to form a bar, block, tubular,
cylindrical billet, or toroid. Machining includes cutting, sawing,
ablating, milling, facing, lathing, boring, and the like using, for
example, a miller, saw, lathe, router, electric discharge machine,
and the like. Alternatively, the carbon composite can be directly
molded to the useful shape by choosing the molds having the desired
shape.
[0061] Sheet materials such as web, paper, strip, tape, foil, mat
or the like can also be made via hot rolling. In an embodiment, the
carbon composite sheets made by hot rolling can be further heated
to allow the binder to effectively bond the carbon microstructures
together.
[0062] Carbon composite pellets can be made by extrusion. For
example, a combination of the graphite and the micro- or nano-sized
binder can be first loaded in a container. Then combination is
pushed into an extruder through a piston. The extrusion temperature
can be about 350.degree. C. to about 1400.degree. C. or about
800.degree. C. to about 1200.degree. C. In an embodiment, the
extrusion temperature is higher than the melting point of the
binder, for example, about 20 to about 50.degree. C. higher than
the melting point of the binder. In an embodiment, wires are
obtained from the extrusion, which can be cut to form pellets. In
another embodiment, pellets are directly obtained from the
extruder. Optionally, a post treatment process can be applied to
the pellets. For example, the pellets can be heated in a furnace
above the melting temperature of the binder so that the binder can
bond the carbon microstructures together if the carbon
microstructures have not been bonded or not adequately bonded
during the extrusion.
[0063] Carbon composite powder can be made by milling carbon
composites, for example a solid piece, through shearing forces
(cutting forces). It is noted that the carbon composites should not
be smashed. Otherwise, the voids within the carbon microstructures
may be destroyed thus the carbon composites lose elasticity.
[0064] The carbon composites have a number of advantageous
properties for use in a wide variety of applications. In an
especially advantageous feature, by forming carbon composites, both
the mechanical strength and the elastomeric properties are
improved.
[0065] To illustrate the improvement of elastic energy achieved by
the carbon composites, the stress-strain curves for the following
samples are shown in FIG. 5: (A) natural graphite, (B) expanded
graphite, (C) a mixture of expanded graphite and a micro- or
nano-sized binder formed at room temperature and atmospheric
pressure, (D) a mixture of expanded graphite and a micro- or
nano-sized binder formed by at a high temperature and atmospheric
pressure; and (E) a carbon composite formed from expanded graphite
and a micro- and nano-sized binder under high pressure and high
temperature conditions. For the natural graphite, the sample was
made by compressing natural graphite in a steel die at a high
pressure. The expanded graphite sample was also made in a similar
manner.
[0066] As shown in FIG. 5, the natural graphite has a very low
elastic energy (area under the stress-strain curve) and is very
brittle. The elastic energy of expanded graphite and the elastic
energy of the mixture of expanded graphite and a micro- or
nano-sized binder compacted at room temperature and high pressure
is higher than that of the natural graphite. Conversely, both the
hard and soft carbon composites of the disclosure exhibit
significantly improved elasticity shown by the notable increase of
the elastic energy as compared to the natural graphite alone, the
expanded graphite alone, and the mixture of expanded graphite and
binder compacted at room temperature and high pressure. In an
embodiment, the carbon composites have an elastic elongation of
greater than about 4%, greater than about 6%, or between about 4%
and about 40%.
[0067] The elasticity of the carbon composites is further
illustrated in FIGS. 6 and 7. FIG. 6 shows loop test results of a
carbon composite at different loadings. FIG. 7 shows hysteresis
results of a carbon composite tested at room temperature and
500.degree. F. respectively. As shown in FIG. 7, the elasticity of
the carbon composite is maintained at 500.degree. F.
[0068] In addition to mechanical strength and elasticity, the
carbon composites can also have excellent thermal stability at high
temperatures. FIG. 8 compares a carbon composite before and after
exposing to air at 500.degree. C. for 5 days. FIG. 9(A) is a photo
of a carbon composite sample after a thermo shock for 8 hours. The
condition for the thermal shock is shown in FIG. 9(B). As shown in
FIGS. 8 and 9(A), there are no changes to the carbon composite
sample after exposing to air at 500.degree. C. for 25 hours or
after the thermal shock. The carbon composites can have high
thermal resistance with a range of operation temperatures from
about -65.degree. F. up to about 1200.degree. F., specifically up
to about 1100.degree. F., and more specifically about 1000.degree.
F.
[0069] The carbon composites can also have excellent chemical
resistance at elevated temperatures. In an embodiment, the
composite is chemically resistant to water, oil, brines, and acids
with resistance rating from good to excellent. In an embodiment,
the carbon composites can be used continuously at high temperatures
and high pressures, for example, about 68.degree. F. to about
1200.degree. F., or about 68.degree. F. to about 1000.degree. F.,
or about 68.degree. F. to about 750.degree. F. under wet
conditions, including basic and acidic conditions. Thus, the carbon
composites resist swelling and degradation of properties when
exposed to chemical agents (e.g., water, brine, hydrocarbons, acids
such as HCl, solvents such as toluene, etc.), even at elevated
temperatures of up to 200.degree. F., and at elevated pressures
(greater than atmospheric pressure) for prolonged periods. The
chemical resistance of the carbon composite is illustrated in FIGS.
10 and 11. FIG. 10 compares a carbon composite sample before and
after exposing to tap water for 20 hours at 200.degree. F., or
after exposing to tap water for 3 days at 200.degree. F. As shown
in FIG. 10, there are no changes to the sample. FIG. 11 compares a
carbon composite sample before and after exposing to 15% HCl
solution with inhibitor at 200.degree. F. for 20 hours, or after
exposing to 15% HCl solution at 200.degree. F. for 3 days. Again,
there are no changes to the carbon composite sample.
[0070] The carbon composites are medium hard to extra hard with
harness from about 50 in SHORE A up to about 75 in SHORE D
scale.
[0071] As a further advantageous feature, the carbon composites
have stable sealing force at high temperatures. The stress decay of
components under constant compressive strain is known as
compression stress relaxation. A compression stress relaxation test
also known as sealing force relaxation test measures the sealing
force exerted by a seal or O-ring under compression between two
plates. It provides definitive information for the prediction of
the service life of materials by measuring the sealing force decay
of a sample as a function of time, temperature and environment.
FIG. 12 shows the sealing force relaxation test results of a carbon
composite sample 600.degree. F. As shown in FIG. 12, the sealing
force of the carbon composite is stable at high temperatures. In an
embodiment, the sealing force of a sample of the composite at 15%
strain and 600.degree. F. is maintained at about 5800 psi without
relaxation for at least 20 minutes.
[0072] The carbon composites described above may be useful for
preparing articles for a wide variety of applications including,
but not limited to electronics, hot metal processing, coatings,
aerospace, automotive, oil and gas, and marine applications.
Exemplary articles include seals, bearings, bearing seats, packers,
valves, engines, reactors, cooling systems, and heat sinks. Thus,
in an embodiment, an article comprises the carbon composites. The
carbon composites may be used to form all or a portion of a
downhole article as will be discussed more fully below.
[0073] A subsurface exploration system, in accordance with an
exemplary embodiment, is indicated generally at 200, in FIG. 13.
Subsurface exploration system 200 includes an uphole system 204
operatively connected to a downhole system 206. Uphole system 204
may include pumps 208 that aid in completion and/or extraction
processes as well as a fluid storage portion 210. Fluid storage
portion 210 may contain a fluid that is introduced into downhole
system 206. Downhole system 206 may include a downhole string 220
that is extended into a wellbore 221 formed in formation 222.
Wellbore 221 may include a wellbore casing 223. Downhole string 220
may include a number of connected downhole tubulars 224. One of
tubulars 224 may support a mandrel 226 which, in turn, may support
a packer 228. Mandrel 226 may include a hollow or solid
cross-section and an angled surface section 230 (FIG. 14) adjacent
packer 228. Packer 228 may be positioned to isolate one portion of
wellbore 221 from another portion of wellbore 221 or as part of a
CO2 sequestration system.
[0074] As shown in FIG. 14, packer 228 includes a structure 240
having a first backup or part 242 and a second backup or part 244.
First part 242 includes a first or inner end 250 arranged adjacent
mandrel 226 and a second, cantilevered outer end 252. Second part
244 includes a first or inner end 254 arranged adjacent tubular 224
and a second, cantilevered outer end 256. First and second parts
242 and 244 extend annularly about mandrel 226. A plurality of
flexible carbon composite particles 260 is arranged between first
and second parts 242 and 244. Structure 240 is formed from an
expandable metal. It should be understood that the plurality of
flexible carbon composite particles 260 are formed from the carbon
composites described above.
[0075] In further accordance with an exemplary embodiment, packer
228 also includes a flexible membrane 270 that extends between
first and second parts 242 and 244. More specifically, flexible
membrane 270 includes a first end section 274 coupled to first part
242, a second end section 276 coupled to second part 244, and an
intermediate portion 278. Intermediate portion 278 extends between
first end section 274 and second end section 276. In accordance
with an aspect of an exemplary embodiment, flexible membrane 270
may be formed from a woven material including, for example, carbon
fibers, metal wires, asbestos fibers, metal fibers, expandable
carbon composite fibers, and the like, that may withstand a high
temperature, high pressure (HTHP) environment such as found
downhole. The woven material should also be capable of withstanding
a corrosive downhole environment. In accordance with another aspect
of an exemplary embodiment, flexible membrane 270 may be formed
from a material, such as a polymer fiber, that may degrade or
decompose when exposed to a downhole environment or injected
chemicals for that purpose.
[0076] In accordance with an aspect of an exemplary embodiment,
after being positioned downhole, a first force 320 may be applied
to first part 242 and a second, opposing force 324 may be applied
to second part 244, as shown in FIG. 15. First and second forces
320 and 324 guide first and second parts 242 and 244 toward each
other along mandrel 226. Of course, it should be understood that
one of first and second parts 242 and 244 may be moved toward
another of first and second parts 242 and 244. As first and second
parts 242 and 244 are moved toward each other, plurality of
flexible carbon composite particles 260 is compressed forming a
bulge region 326.
[0077] Another force 328 shifts structure 240 along mandrel 226, as
shown in FIG. 16. Force 328 guides structure 240 along angled
surface section 230 causing bulge region 326 to contact wellbore
casing 223. Further shifting along angled surface section 230
results in a compressive force being imparted to plurality of
flexible carbon composite particles 260, as shown in FIG. 17. The
compressive force causes plurality of flexible carbon composite
particles 260 to deform. As plurality of flexible carbon composite
particles 260 include relatively slippery surfaces, the deformation
results in little or no tension being created between flexible
carbon composite particles 260 during compression. As first and
second parts 242 and 244 compress against wellbore casing 223,
plurality of flexible carbon composite particles 260 deform further
and become more compressed. As plurality of carbon composite
particles 260 includes relatively slippery surfaces, the
deformation results in the formation of a flexible carbon composite
compact 350 that is substantially tension free. Further, plurality
of flexible carbon composite particles 260 possess high
malleability and elasticity properties that result in a resilient,
corrosive resistant, HTHP seal to isolate portions of wellbore
221.
[0078] Reference will now follow to FIGS. 18 and 19, wherein like
numbers represent corresponding parts in the respective views, in
describing a packer 360 formed in accordance with another aspect of
an exemplary embodiment. Packer 360 includes a structure 370
including a first backup or part 372 and a second backup or part
374. First part 372 includes a first or inner end 380 arranged
adjacent mandrel 226 and a second, cantilevered outer end 382.
Second part 374 includes a first or inner end 384 arranged adjacent
tubular 224 and a second, cantilevered outer end 386. First and
second parts 372 and 374 extend annularly about mandrel 226.
[0079] Packer 360 also includes a flexible membrane 390 extending
between first and second parts 372 and 374. Flexible membrane 390
is formed in a tube 394 having an interior portion 396. Tube 394
extends or wraps about tubular 224 in a series of coils 398. In
accordance with an aspect of an exemplary embodiment, coils 398 are
joined to reduce leakage. However, it should be understood that
coils 398 may also be separate from one another. In either case,
tube 394 may be flexible. In a manner similar to that described
above, tube 394 may be formed from a woven material including, for
example, carbon fibers, metal wires, asbestos fibers, metal fibers,
expandable carbon composite fibers, and the like, that may
withstand a high temperature, high pressure (HTHP) environment such
as found downhole. The woven material should also be capable of
withstanding a corrosive downhole environment.
[0080] A plurality of flexible carbon composite particles 420 is
within interior portion 396. With this arrangement, a force 440 is
exerted on first part 372. Force 440 guides first part 372 toward
second part 374 compressing coils 398. As coils 398 compress, first
and/or second parts 372 and 374 shift along a surface 450 of
mandrel 226 causing flexible membrane 390 to expand. Second part
374 may be fixed or constrained by a stop 470 causing flexible
membrane 390 and the plurality of flexible carbon composite
particles 420 to compress and form a seal against wellbore casing
223. Of course, it should be understood that one of first and
second parts 372 and 374 may be also guided along an angled surface
section causing coils 398 to expand radially outwardly and seat
against wellbore casing 223. Once seated, a second stop or body
lock 474 is secured to surface 450 locking first part 372 in place
to tubular 224 to isolate a first part of formation 222 from a
second part of formation 222.
[0081] All ranges disclosed herein are inclusive of the endpoints,
and the endpoints are independently combinable with each other. The
suffix "(s)" as used herein is intended to include both the
singular and the plural of the term that it modifies, thereby
including at least one of that term (e.g., the colorant(s) includes
at least one colorants). "Or" means `and/or." "Optional" or
"optionally" means that the subsequently described event or
circumstance can or cannot occur, and that the description includes
instances where the event occurs and instances where it does not.
As used herein, "combination" is inclusive of blends, mixtures,
alloys, reaction products, and the like. All references are
incorporated herein by reference.
[0082] The use of the terms "a" and "an" and "the" and similar
referents in the context of describing the invention (especially in
the context of the following claims) are to be construed to cover
both the singular and the plural, unless otherwise indicated herein
or clearly contradicted by context. Further, it should further be
noted that the terms "first," "second," and the like herein do not
denote any order, quantity, or importance, but rather are used to
distinguish one element from another. The modifier "about" used in
connection with a quantity is inclusive of the stated value and has
the meaning dictated by the context (e.g., it includes the degree
of error associated with measurement of the particular
quantity).
[0083] While one or more embodiments have been shown and described,
modifications and substitutions may be made thereto without
departing from the spirit and scope of the invention. Accordingly,
it is to be understood that the present invention has been
described by way of illustrations and not limitation.
* * * * *