U.S. patent application number 13/030817 was filed with the patent office on 2012-08-23 for apparatus and method for controlling gas lift assemblies.
This patent application is currently assigned to BAKER HUGHES INCORPORATED. Invention is credited to Christopher K. Clopper, Peter J. Fay, James H. Kritzler, Zhiyue Xu.
Application Number | 20120211239 13/030817 |
Document ID | / |
Family ID | 46651807 |
Filed Date | 2012-08-23 |
United States Patent
Application |
20120211239 |
Kind Code |
A1 |
Kritzler; James H. ; et
al. |
August 23, 2012 |
APPARATUS AND METHOD FOR CONTROLLING GAS LIFT ASSEMBLIES
Abstract
A production fluid control apparatus is disclosed. The apparatus
includes: a gas lift assembly in fluid communication with a
borehole production conduit, the gas lift assembly configured to
control a flow of pressurized gas between an annular region of a
borehole and the production conduit; and at least one plug disposed
in operable communication with the gas lift assembly, the at least
one plug configured to prevent fluid flow through the gas lift
assembly and configured to be actuated to allow fluid flow through
the gas lift assembly in response to exposure to a downhole
fluid.
Inventors: |
Kritzler; James H.;
(Pearland, TX) ; Clopper; Christopher K.; (Cabot,
AR) ; Xu; Zhiyue; (Cypress, TX) ; Fay; Peter
J.; (Houston, TX) |
Assignee: |
BAKER HUGHES INCORPORATED
Houston
TX
|
Family ID: |
46651807 |
Appl. No.: |
13/030817 |
Filed: |
February 18, 2011 |
Current U.S.
Class: |
166/372 ;
166/68 |
Current CPC
Class: |
E21B 43/122 20130101;
E21B 33/12 20130101 |
Class at
Publication: |
166/372 ;
166/68 |
International
Class: |
E21B 43/00 20060101
E21B043/00 |
Claims
1. A production fluid control apparatus comprising: a gas lift
assembly in fluid communication with a borehole production conduit,
the gas lift assembly configured to control a flow of pressurized
gas between an annular region of a borehole and the production
conduit; and at least one plug disposed in operable communication
with the gas lift assembly, the at least one plug configured to
prevent fluid flow through the gas lift assembly and configured to
be actuated to allow fluid flow through the gas lift assembly in
response to exposure to a downhole fluid.
2. The apparatus of claim 1, wherein the at least one plug is made
from a material configured to dissolve or corrode in the presence
of the downhole fluid.
3. The apparatus of claim 2, wherein the downhole fluid is selected
from at least one of water, salinated water and hydrocarbon
fluid.
4. The apparatus of claim 1, wherein the at least one plug is
disposed in a fluid path between the production conduit and the gas
lift assembly.
5. The apparatus of claim 1, the apparatus of claim 1, wherein the
gas lift assembly further includes a support component disposed in
a fixed position relative to the production conduit, and a flow
control device configured to control the flow of pressurized gas
through the gas lift assembly.
6. The apparatus of claim 5, wherein the at least one plug is
located within the flow control device
7. The apparatus of claim 5, wherein the at least one plug is
located in a fluid path between the flow control device and the
production conduit.
8. The apparatus of claim 2, wherein the material includes: a
substantially-continuous, cellular nanomatrix comprising a
nanomatrix material; a plurality of dispersed particles comprising
a particle core material that comprises Mg, Al, Zn or Mn, or a
combination thereof, dispersed in the cellular nanomatrix; and a
solid state bond layer extending throughout the cellular nanomatrix
between the dispersed particles.
9. The apparatus of claim 8, wherein the material includes a
plurality of dispersed second particles, wherein the dispersed
second particles are also dispersed within the cellular nanomatrix
and with respect to the dispersed particles.
10. The apparatus of claim 2, wherein the at least one plug is
formed from a sintered powder comprising a plurality of powder
particles, each powder particle having a particle core that upon
sintering comprises a dispersed particle and a single metallic
coating layer disposed thereon, and wherein the cellular nanomatrix
between adjacent ones of the plurality of dispersed particles
comprises the single metallic coating layer of one powder particle,
the bond layer and the single metallic coating layer of another of
the powder particles.
11. The apparatus of claim 2, wherein the at least one plug is
formed from a sintered powder comprising a plurality of powder
particles, each powder particle having a particle core that upon
sintering comprises a dispersed particle and a plurality of
metallic coating layers disposed thereon, and wherein the cellular
nanomatrix between adjacent ones of the plurality of dispersed
particles comprises the plurality of metallic coating layers of one
powder particle, the bond layer and plurality of metallic coating
layers of another of the powder particles, and wherein adjacent
ones of the plurality of metallic coating layers have different
chemical compositions.
12. A method of producing hydrocarbon fluid from a borehole,
comprising: disposing a production assembly in the borehole, the
production assembly including a production conduit and a gas lift
assembly in fluid communication with the production conduit, the
gas lift assembly configured to control a flow of pressurized gas
between an annular region of the borehole and the production
conduit, the gas lift assembly including at least one plug disposed
in operable communication therewith and configured to prevent fluid
flow through the gas lift assembly; exposing the at least one plug
to a downhole fluid; and actuating the at least one plug by
dissolving at least a portion of the at least one plug in response
to exposure to the downhole fluid to allow fluid to flow through
the gas lift assembly.
13. The method of claim 12, further comprising injecting the
pressurized gas into the annular region, and directing the annular
gas to the production conduit via the gas lift assembly.
14. The method of claim 13, wherein the downhole fluid is a
production fluid flowing through the production conduit.
15. The method of claim 12, wherein the at least one plug is made
from a material configured to dissolve or corrode in the presence
of the downhole fluid.
16. The method of claim 15, wherein the downhole fluid is selected
from at least one of water, salinated water and hydrocarbon
fluid.
17. The method of claim 12, wherein actuating the at least one plug
includes contacting the at least one plug with downhole fluid
flowing through the production conduit, and dissolving or corroding
the at least one plug over a pre-selected time period.
18. The method of claim 12, wherein the gas lift assembly further
includes a support component disposed in a fixed position relative
to the production conduit, and a flow control device configured to
control the flow of pressurized gas through the gas lift
assembly.
19. The method of claim 18, wherein the at least one plug is
located within the flow control device.
20. The method of claim 18, wherein the at least one plug is
located in a fluid path between the flow control device and the
production conduit.
Description
BACKGROUND
[0001] Hydrocarbon production systems typically rely on formation
pressure from subterranean reservoirs to produce hydrocarbon fluids
and gases. In a naturally flowing well, there is enough energy
stored in the high pressure reservoir to produce liquids and gases
to the surface. When this reservoir energy decreases, it is
generally necessary to apply some form of artificial lift to assist
in producing these liquids and gases to the surface.
[0002] Gas lift is a form of artificial lift that is used to assist
in producing boreholes that do not flow or cannot flow at optimum
or desired producing rates. Gas lift systems generally include a
mechanism for injecting high pressure gas from an annular region of
the well into a production conduit. A valve is typically used in
gas lift systems to control flow of the high pressure gas into the
production conduit.
[0003] Dummy valves are often loaded in side pocket mandrels when
they are installed in borehole completion systems to isolate a
borehole annulus from the production tubing where, for example,
pressurization is required to test the tubing, test the annulus,
set a hydraulic packer or activate an isolation device. If the
borehole requires gas lift to unload the completion fluid or assist
in producing production fluid, wireline intervention is typically
required to remove the dummy valves and install a live gas lift
device.
BRIEF DESCRIPTION OF THE INVENTION
[0004] A production fluid control apparatus includes: a gas lift
assembly in fluid communication with a borehole production conduit,
the gas lift assembly configured to control a flow of pressurized
gas between an annular region of a borehole and the production
conduit; and at least one plug disposed in operable communication
with the gas lift assembly, the at least one plug configured to
prevent fluid flow through the gas lift assembly and configured to
be actuated to allow fluid flow through the gas lift assembly in
response to exposure to a downhole fluid.
[0005] A method of producing hydrocarbon fluid from a borehole
includes: disposing a production assembly in the borehole, the
production assembly including a production conduit and a gas lift
assembly in fluid communication with the production conduit, the
gas lift assembly configured to control a flow of pressurized gas
between an annular region of the borehole and the production
conduit, the production assembly including at least one plug
configured to prevent fluid flow through the gas lift assembly;
exposing the at least one plug to a downhole fluid; and actuating
the at least one plug by dissolving or corroding at least a portion
of the at least one plug in response to exposure to the downhole
fluid to allow fluid to flow through the gas lift assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] The following descriptions should not be considered limiting
in any way. With reference to the accompanying drawings, like
elements are numbered alike:
[0007] FIG. 1 depicts an embodiment of a downhole completion and/or
production system including a gas lift assembly;
[0008] FIG. 2 is a partial cross-sectional view of an exemplary
embodiment of a valve configured for use with the gas lift assembly
of FIG. 1;
[0009] FIG. 3 is a close-up view of a portion of an exemplary
embodiment of the valve of FIG. 2;
[0010] FIG. 4 is a partial cross-sectional view of an exemplary
embodiment of the gas lift assembly of FIG. 1;
[0011] FIG. 5 is a partial cross-sectional view of an exemplary
embodiment of the gas lift assembly of FIG. 1;
[0012] FIG. 6 is a photomicrograph of a powder as disclosed herein
that has been embedded in a potting material and sectioned;
[0013] FIG. 7 is a schematic illustration of an exemplary
embodiment of a powder particle as it would appear in an exemplary
section view represented by section 5-5 of FIG. 6;
[0014] FIG. 8 is a photomicrograph of an exemplary embodiment of a
powder compact as disclosed herein;
[0015] FIG. 9 is a schematic of illustration of an exemplary
embodiment of the powder compact of FIG. 8 made using a powder
having single-layer powder particles as it would appear taken along
section 7-7;
[0016] FIG. 10 is a schematic of illustration of another exemplary
embodiment of the powder compact of FIG. 8 made using a powder
having multilayer powder particles as it would appear taken along
section 7-7;
[0017] FIG. 11 is a schematic illustration of a change in a
property of a powder compact as disclosed herein as a function of
time and a change in condition of the powder compact environment;
and
[0018] FIG. 12 is a flow diagram depicting a method of controlling
production fluid in a borehole.
DETAILED DESCRIPTION OF THE INVENTION
[0019] There is provided apparatuses and methods for controlling
hydrocarbon production in a borehole in an earth formation. A
production assembly such as a production string is configured to be
disposed in a borehole and facilitate production of hydrocarbons
(e.g., oil and/or gas). A gas lift assembly is disposed in the
production assembly, and includes one or more ports configured to
allow pressurized gas to flow through the gas lift assembly and
into the production assembly, e.g., into a production conduit, to
provide lift and facilitate hydrocarbon production. At least one
plug that includes a material configured to react with downhole
fluids is disposed in fluid communication with the gas lift
assembly and prevents lift gas from flowing into the production
conduit. The plug is actuatable in response to exposure to downhole
fluid (e.g., salinated water and/or production fluids including
hydrocarbon liquids and/or gases) to allow the lift gas to flow
into the production conduit. In one embodiment, the plug is a
dissolvable plug configured to corrode, degrade, dissolve or go
into solution upon exposure to downhole fluids.
[0020] Referring to FIG. 1, an exemplary embodiment of a downhole
completion and/or production system 110 includes a borehole string
112 that is shown disposed in a borehole 114 that penetrates at
least one earth formation 116. The borehole 114 may be an open hole
or an at least partially cased hole, and may be generally vertical
or include a horizontal component. A "borehole string", as used
herein, refers to a production assembly including a production
string having a production conduit, and may also refer to any
structure or carrier suitable for lowering a tool or component
through a borehole and/or connecting a tool to the surface, and is
not limited to the structure and configuration described herein. A
"carrier" as described herein means any device, device component,
combination of devices, media and/or member that may be used to
convey, house, support or otherwise facilitate the use of another
device, device component, combination of devices, media and/or
member. Exemplary non-limiting carriers include borehole strings of
the coiled tube type, of the jointed pipe type and any combination
or portion thereof Other carrier examples include casing pipes,
wirelines, wireline sondes, slickline sondes, drop shots, downhole
subs, and bottom-hole assemblies.
[0021] The system 110 nay include a downhole packing tool 118 such
as an inflateable or expandable packer. The packing tool 118 is
configured to prevent production of formation sand or other
particulates as production fluid is produced from the formation
116, and aid in directing production fluid into the borehole string
112. The packing tool 118 may be incorporated in the borehole
string 112 as, for example, a packer sub or joint.
[0022] As shown in FIG. 1, the borehole string 112 includes a gas
lift assembly 120 configured to pump, inject or otherwise introduce
pressurized gas into a production conduit 122 in the borehole
string 112 to aid in forcing production fluid toward the surface.
The gas lift assembly 120 includes a support component in operable
communication with the production conduit 122 and with one or more
gas inlet ports 124. The gas inlet ports 124 provide fluid
communication between the gas lift assembly 120 and an annular
region of the borehole 112 into which pressurized gases are
injected from, for example, a surface injection, processing and/or
control unit 125. The support component is configured as, in one
embodiment, a tubular housing extending axially (i.e., extending at
least partially in a direction generally parallel to a longitudinal
axis of the borehole 114) along the borehole string 112. In one
embodiment, the support component includes a side pocket mandrel
126 that is held in a fixed position relative to the production
conduit 122. The mandrel 126 may be held in any suitable manner,
such as affixed by a mechanical connection such as a weld, screws
or by a latch located in a latch profile 128, by forming a conduit
in the borehole string wall. Although the support component is
described herein as the mandrel 126, the support component is not
so limited and may include any structures or configurations
sufficient to secure the gas lift assembly 120 in or with the
borehole string 112.
[0023] The mandrel 126, in one embodiment, includes one or more
cavities 130 configured to hold components of the gas lift assembly
120 and/or at least partially seal the components from the
production conduit 122.
[0024] Referring to FIG. 2, in one embodiment, the gas lift
assembly 120 includes a gas flow control device 132 that is
configured to control the flow of downhole fluid and/or the
pressurized gas through the gas lift assembly 120, the mandrel 126
and/or the ports 124. The gas flow control device 132 is configured
to seal in the cavities 130 and direct pressurized gas flow from an
annular area in fluid communication with the flow ports 124,
through flow ports 134 of the gas flow control device 132 and
through the flow control device 132. In one embodiment, pressurized
gas is directed from the flow ports 134 and into the production
conduit 122 via one or more outlet ports 136 located in, for
example, a nose section 138 of the gas flow control device 132.
[0025] In one embodiment, the gas flow control device 132 includes
one or more valve assemblies configured to control fluid flow
through the flow control device 132. For example, As shown in FIG.
3, a reverse flow check valve 140 is disposed in the flow control
device 132 to prevent pressurized gases from flowing backward
relative to the desired flow direction and/or prevent other
downhole fluids from flowing into the flow control device 132.
[0026] The gas lift assembly 120 also includes at least one plug
142 disposed in operable communication with the gas lift assembly
120 and configured to block the flow of fluid (including production
fluids and the pressurized gas used for the artificial lift)
between the production conduit 122 and other regions in the
borehole 114, such as an annular region around the production
conduit 122. The plug 142 is configured to be actuatable in
response to exposure to downhole fluids such as water and
production fluids including hydrocarbon liquids and/or gases.
[0027] The plug 142 is made at least partially from a material
configured to corrode, degrade, reduce, dissolve or go into
solution when in contact with a downhole fluid. In one embodiment,
the plug 142 is made of a material such that the plug 142 will at
least partially disappear or dissolve and allow the gas lift
assembly 120 and/or flow control device 132 to function as
designed. The gas lift plug 142 is manufactured from a material
which will provide a temporary positive barrier to pressurized gas
and downhole fluids and prevent them from flowing through the gas
lift assembly 120.
[0028] In one embodiment, before the gas lift plug 142 is
sufficiently dissolved to allow fluid flow therethrough, the plug
142 causes the gas lift assembly 120 to act as a temporary dummy
valve. As described herein, a "dummy valve" refers to any device or
mechanism that is disposed in place of a borehole component and
acts to restrict fluid flow therethrough. A dummy valve is
generally replaced with the borehole component when the component
is needed. For example, the gas lift plug 142 isolates the annulus
from the production conduit 122 where pressurization is required to
perform actions such as testing the production string 112, testing
the annulus, setting a packer or activating an isolation
device.
[0029] FIG. 3. shows an exemplary embodiment of the gas lift plug
142. In this embodiment, the gas lift plug 142 is disposed within
the flow control device 132 (e.g., by being installed or
retro-fitted in the flow control device 132) to prevent fluid flow
in any direction therethrough. For example, the plug 142 is
disposed in a location proximate to the flow ports 36 so that the
plug 142 is exposed to downhole fluid in the production conduit
122. Such a location includes, but is not limited to, a location in
a nose portion 138 of the flow control device 132, between the flow
ports 136 and the reverse flow check valve 140.
[0030] FIGS. 4 and 5 show additional exemplary embodiments of the
gas lift plug 142. In these embodiments, the plug 142 is disposed
in a fluid path between the conduit 122 and the gas lift assembly
120 and/or the mandrel 126. In the embodiment shown in FIG. 4, the
plug is formed as a bar shape, a cylindrical shape and/or a tubular
shape, and is disposed outside of the flow control device 132 to
block the outlet ports 136 of the flow control device 132. In the
embodiment shown in FIG. 5, the plug 142 is formed as a hollow
cylindrical or toroidal shape having an outer diameter
substantially the same or similar to the inside diameter of a
length of the conduit 122. The plug 142 is held in place, for
example, by a side wall of the production conduit 122 (e.g., a
bottom swage 144) and the end of the fluid control device 132
and/or mandrel 126.
[0031] The configuration, size and shape of the plug 142 is not
limited to that described herein. In addition to the cylindrical
and annular or toroidal shapes described herein, the plug 142 may
take any shape such as tubular shapes configured to conform to any
conduits or cavities in or operably coupled to the gas lift
assembly 120.
[0032] In one embodiment, the gas lift plug 142 is made of a
material and shaped or otherwise configured to dissolve at a known
rate upon exposure to a downhole fluid, and accordingly block fluid
for an approximately known period of time. For example, the gas
plug material is a material that does not substantially react with
drilling mud or other fluids, and eloctrolytically decomposes in a
selected time, for example, 12-24 hours in salt water dependent
upon temperature and well conditions.
[0033] The gas lift plug material includes any material or
combination of materials that is configured to dissolve, corrode,
degrade, break up or otherwise reduce in size upon exposure to
downhole fluids. Such materials include metallic materials such as
magnesium and/or aluminum, which may be formed for example by
depositing layers of material by techniques such electrochemical
deposition and vapor deposition such as chemical vapor deposition
(CVD).
[0034] In one embodiment, the gas lift plug 142 includes or is at
least partially made from a corrodible or soluble material. The
materials in the gas lift plug 142 as described herein are
lightweight, high-strength metallic materials that may be used in a
wide variety of applications and application environments,
including use in various wellbore environments to make various
selectably and controllably disposable or degradable lightweight,
high-strength downhole tools or other downhole components, as well
as many other applications for use in both durable and disposable
or degradable articles. These lightweight, high-strength and
selectably and controllably degradable materials include
fully-dense, sintered powder compacts formed from coated powder
materials that include various lightweight particle cores and core
materials having various single layer and multilayer nanoscale
coatings. These powder compacts are made from coated metallic
powders that include various electrochemically-active (e.g., having
relatively higher standard oxidation potentials) lightweight,
high-strength particle cores and core materials, such as
electrochemically active metals, that are dispersed within a
cellular nanomatrix formed from the various nanoscale metallic
coating layers of metallic coating materials, and are particularly
useful in wellbore applications. These powder compacts provide a
unique and advantageous combination of mechanical strength
properties, such as compression and shear strength, low density and
selectable and controllable corrosion properties, particularly
rapid and controlled dissolution in various wellbore fluids. For
example, the particle core and coating layers of these powders may
be selected to provide sintered powder compacts suitable for use as
high strength engineered materials having a compressive strength
and shear strength comparable to various other engineered
materials, including carbon, stainless and alloy steels, but which
also have a low density comparable to various polymers, elastomers,
low-density porous ceramics and composite materials. As yet another
example, these powders and powder compact materials may be
configured to provide a selectable and controllable degradation or
disposal in response to a change in an environmental condition,
such as a transition from a very low dissolution rate to a very
rapid dissolution rate in response to a change in a property or
condition of a wellbore proximate an article formed from the
compact, including a property change in a wellbore fluid that is in
contact with the powder compact. The selectable and controllable
degradation or disposal characteristics described also allow the
dimensional stability and strength of articles, such as wellbore
tools or other components, made from these materials to be
maintained until they are no longer needed, at which time a
predetermined environmental condition, such as a wellbore
condition, including wellbore fluid temperature, pressure or pH
value, may be changed to promote their removal by rapid
dissolution. These coated powder materials and powder compacts and
engineered materials formed from them, as well as methods of making
them, are described further below.
[0035] Referring to FIG. 6, a metallic powder 210 includes a
plurality of metallic, coated powder particles 212. Powder
particles 212 may be formed to provide a powder 210, including
free-flowing powder, that may be poured or otherwise disposed in
all manner of forms or molds (not shown) having all manner of
shapes and sizes and that may be used to fashion precursor powder
compacts and powder compacts 400 (FIGS. 9 and 10), as described
herein, that may be used as at least a portion of the gas lift plug
142.
[0036] Each of the metallic, coated powder particles 212 of powder
210 includes a particle core 214 and a metallic coating layer 216
disposed on the particle core 214. The particle core 214 includes a
core material 218. The core material 218 may include any suitable
material for forming the particle core 214 that provides powder
particle 212 that can be sintered to form a lightweight,
high-strength powder compact 400 having selectable and controllable
dissolution characteristics. Suitable core materials include
electrochemically active metals having a standard oxidation
potential greater than or equal to that of Zn, including as Mg, Al,
Mn or Zn or a combination thereof These electrochemically active
metals are very reactive with a number of common wellbore fluids,
including any number of ionic fluids or highly polar fluids, such
as those that contain various chlorides. Examples include fluids
comprising potassium chloride (KCl), hydrochloric acid (HCl),
calcium chloride (CaCl.sub.2), calcium bromide (CaBr.sub.2) or zinc
bromide (ZnBr.sub.2). Core material 218 may also include other
metals that are less electrochemically active than Zn or
non-metallic materials, or a combination thereof Suitable
non-metallic materials include ceramics, composites, glasses or
carbon, or a combination thereof Core material 218 may be selected
to provide a high dissolution rate in a predetermined wellbore
fluid, but may also be selected to provide a relatively low
dissolution rate, including zero dissolution, where dissolution of
the nanomatrix material causes the particle core 214 to be rapidly
undermined and liberated from the particle compact at the interface
with the wellbore fluid, such that the effective rate of
dissolution of particle compacts made using particle cores 214 of
these core materials 218 is high, even though core material 218
itself may have a low dissolution rate, including core materials
220 that may be substantially insoluble in the wellbore fluid.
[0037] With regard to the electrochemically active metals as core
materials 218, including Mg, Al, Mn or Zn, these metals may be used
as pure metals or in any combination with one another, including
various alloy combinations of these materials, including binary,
tertiary, or quaternary alloys of these materials. These
combinations may also include composites of these materials.
Further, in addition to combinations with one another, the Mg, Al,
Mn or Zn core materials 218 may also include other constituents,
including various alloying additions, to alter one or more
properties of the particle cores 214, such as by improving the
strength, lowering the density or altering the dissolution
characteristics of the core material 218.
[0038] Among the electrochemically active metals, Mg, either as a
pure metal or an alloy or a composite material, is particularly
useful, because of its low density and ability to form
high-strength alloys, as well as its high degree of electrochemical
activity, since it has a standard oxidation potential higher than
Al, Mn or Zn. Mg alloys include all alloys that have Mg as an alloy
constituent. Mg alloys that combine other electrochemically active
metals, as described herein, as alloy constituents are particularly
useful, including binary Mg--Zn, Mg--Al and Mg--Mn alloys, as well
as tertiary Mg--Zn--Y and Mg--Al--X alloys, where X includes Zn,
Mn, Si, Ca or Y, or a combination thereof These Mg--Al--X alloys
may include, by weight, up to about 85% Mg, up to about 15% Al and
up to about 5% X. Particle core 214 and core material 218, and
particularly electrochemically active metals including Mg, Al, Mn
or Zn, or combinations thereof, may also include a rare earth
element or combination of rare earth elements. As used herein, rare
earth elements include Sc, Y, La, Ce, Pr, Nd or Er, or a
combination of rare earth elements. Where present, a rare earth
element or combinations of rare earth elements may be present, by
weight, in an amount of about 5% or less.
[0039] Particle core 214 and core material 218 have a melting
temperature (Tp). As used herein, T.sub.P includes the lowest
temperature at which incipient melting or liquation or other forms
of partial melting occur within core material 218, regardless of
whether core material 218 comprises a pure metal, an alloy with
multiple phases having different melting temperatures or a
composite of materials having different melting temperatures.
[0040] Particle cores 214 may have any suitable particle size or
range of particle sizes or distribution of particle sizes. For
example, the particle cores 214 may be selected to provide an
average particle size that is represented by a normal or Gaussian
type unimodal distribution around an average or mean. In another
example, particle cores 214 may be selected or mixed to provide a
multimodal distribution of particle sizes, including a plurality of
average particle core sizes, such as, for example, a homogeneous
bimodal distribution of average particle sizes. The selection of
the distribution of particle core size may be used to determine,
for example, the particle size and interparticle spacing 215 of the
particles 212 of powder 210. In an exemplary embodiment, the
particle cores 214 may have a unimodal distribution and an average
particle diameter of about 5 .mu.m to about 300 .mu.m, more
particularly about 80 .mu.m to about 120 .mu.m, and even more
particularly about 100 .mu.m.
[0041] Particle cores 214 may have any suitable particle shape,
including any regular or irregular geometric shape, or combination
thereof In an exemplary embodiment, particle cores 214 are
substantially spheroidal electrochemically active metal particles.
In another exemplary embodiment, particle cores 214 are
substantially irregularly shaped ceramic particles. In yet another
exemplary embodiment, particle cores 214 are carbon or other
nanotube structures or hollow glass microspheres.
[0042] Each of the metallic, coated powder particles 212 of powder
210 also includes a metallic coating layer 216 that is disposed on
particle core 214. Metallic coating layer 216 includes a metallic
coating material 220. Metallic coating material 220 gives the
powder particles 212 and powder 210 its metallic nature. Metallic
coating layer 216 is a nanoscale coating layer. In an exemplary
embodiment, metallic coating layer 216 may have a thickness of
about 25 nm to about 2500 nm. The thickness of metallic coating
layer 216 may vary over the surface of particle core 214, but will
preferably have a substantially uniform thickness over the surface
of particle core 214. Metallic coating layer 216 may include a
single layer, as illustrated in FIG. 7, or a plurality of layers as
a multilayer coating structure. In a single layer coating, or in
each of the layers of a multilayer coating, the metallic coating
layer 216 may include a single constituent chemical element or
compound, or may include a plurality of chemical elements or
compounds. Where a layer includes a plurality of chemical
constituents or compounds, they may have all manner of homogeneous
or heterogeneous distributions, including a homogeneous or
heterogeneous distribution of metallurgical phases. This may
include a graded distribution where the relative amounts of the
chemical constituents or compounds vary according to respective
constituent profiles across the thickness of the layer. In both
single layer and multilayer coatings 216, each of the respective
layers, or combinations of them, may be used to provide a
predetermined property to the powder particle 212 or a sintered
powder compact formed therefrom. For example, the predetermined
property may include the bond strength of the metallurgical bond
between the particle core 214 and the coating material 220; the
interdiffusion characteristics between the particle core 214 and
metallic coating layer 216, including any interdiffusion between
the layers of a multilayer coating layer 216; the interdiffusion
characteristics between the various layers of a multilayer coating
layer 216; the interdiffusion characteristics between the metallic
coating layer 216 of one powder particle and that of an adjacent
powder particle 212; the bond strength of the metallurgical bond
between the metallic coating layers of adjacent sintered powder
particles 212, including the outermost layers of multilayer coating
layers; and the electrochemical activity of the coating layer
216.
[0043] Metallic coating layer 216 and coating material 220 have a
melting temperature (T.sub.C). As used herein, T.sub.C includes the
lowest temperature at which incipient melting or liquation or other
forms of partial melting occur within coating material 220,
regardless of whether coating material 220 comprises a pure metal,
an alloy with multiple phases each having different melting
temperatures or a composite, including a composite comprising a
plurality of coating material layers having different melting
temperatures.
[0044] Metallic coating material 220 may include any suitable
metallic coating material 220 that provides a sinterable outer
surface 221 that is configured to be sintered to an adjacent powder
particle 212 that also has a metallic coating layer 216 and
sinterable outer surface 221. In powders 210 that also include
second or additional (coated or uncoated) particles 232, as
described herein, the sinterable outer surface 221 of metallic
coating layer 216 is also configured to be sintered to a sinterable
outer surface 221 of second particles 232. In an exemplary
embodiment, the powder particles 212 are sinterable at a
predetermined sintering temperature (T.sub.S) that is a function of
the core material 218 and coating material 220, such that sintering
of powder compact 400 is accomplished entirely in the solid state
and where T.sub.S is less than T.sub.P and T.sub.C. Sintering in
the solid state limits particle core 214/metallic coating layer 416
interactions to solid state diffusion processes and metallurgical
transport phenomena and limits growth of and provides control over
the resultant interface between them. In contrast, for example, the
introduction of liquid phase sintering would provide for rapid
interdiffusion of the particle core 214/metallic coating layer 216
materials and make it difficult to limit the growth of and provide
control over the resultant interface between them, and thus
interfere with the formation of the desirable microstructure of
particle compact 400 as described herein.
[0045] In an exemplary embodiment, core material 218 will be
selected to provide a core chemical composition and the coating
material 220 will be selected to provide a coating chemical
composition and these chemical compositions will also be selected
to differ from one another. In another exemplary embodiment, the
core material 218 will be selected to provide a core chemical
composition and the coating material 220 will be selected to
provide a coating chemical composition and these chemical
compositions will also be selected to differ from one another at
their interface. Differences in the chemical compositions of
coating material 220 and core material 218 may be selected to
provide different dissolution rates and selectable and controllable
dissolution of powder compacts 400 that incorporate them making
them selectably and controllably dissolvable. This includes
dissolution rates that differ in response to a changed condition in
the wellbore, including an indirect or direct change in a wellbore
fluid. In an exemplary embodiment, a powder compact 400 formed from
powder 210 having chemical compositions of core material 218 and
coating material 220 that make compact 400 is selectably
dissolvable in a wellbore fluid in response to a changed wellbore
condition that includes a change in temperature, change in
pressure, change in flow rate, change in pH or change in chemical
composition of the wellbore fluid, or a combination thereof The
selectable dissolution response to the changed condition may result
from actual chemical reactions or processes that promote different
rates of dissolution, but also encompass changes in the dissolution
response that are associated with physical reactions or processes,
such as changes in wellbore fluid pressure or flow rate.
[0046] As illustrated in FIGS. 7 and 8, particle core 214 and core
material 218 and metallic coating layer 216 and coating material
220 may be selected to provide powder particles 212 and a powder
210 that is configured for compaction and sintering to provide a
powder compact 400 that is lightweight (i.e., having a relatively
low density), high-strength and is selectably and controllably
removable from a wellbore in response to a change in a wellbore
property, including being selectably and controllably dissolvable
in or in contact with an appropriate wellbore fluid, including
various wellbore fluids as disclosed herein. In one embodiment, the
gas lift plug 142 is at least partially formed from the powder
compact 400.
[0047] Powder compact 400 includes a substantially-continuous,
cellular nanomatrix 416 of a nanomatrix material 420 having a
plurality of dispersed particles 414 dispersed throughout the
cellular nanomatrix 416. The substantially-continuous cellular
nanomatrix 416 and nanomatrix material 420 formed of sintered
metallic coating layers 216 is formed by the compaction and
sintering of the plurality of metallic coating layers 216 of the
plurality of powder particles 212. The chemical composition of
nanomatrix material 420 may be different than that of coating
material 220 due to diffusion effects associated with the sintering
as described herein. Powder metal compact 400 also includes a
plurality of dispersed particles 414 that comprise particle core
material 418. Dispersed particle cores 414 and core material 418
correspond to and are formed from the plurality of particle cores
214 and core material 218 of the plurality of powder particles 212
as the metallic coating layers 216 are sintered together to form
nanomatrix 416. The chemical composition of core material 418 may
be different than that of core material 218 due to diffusion
effects associated with sintering as described herein.
[0048] As used herein, the use of the term substantially-continuous
cellular nanomatrix 416 does not connote the major constituent of
the powder compact, but rather refers to the minority constituent
or constituents, whether by weight or by volume. This is
distinguished from most matrix composite materials where the matrix
comprises the majority constituent by weight or volume. The use of
the term substantially-continuous, cellular nanomatrix is intended
to describe the extensive, regular, continuous and interconnected
nature of the distribution of nanomatrix material 420 within powder
compact 400. As used herein, "substantially-continuous" describes
the extension of the nanomatrix material throughout powder compact
400 such that it extends between and envelopes substantially all of
the dispersed particles 414. Substantially-continuous is used to
indicate that complete continuity and regular order of the
nanomatrix around each dispersed particle 414 is not required. For
example, defects in the coating layer 216 over particle core 214 on
some powder particles 212 may cause bridging of the particle cores
214 during sintering of the powder compact 400, thereby causing
localized discontinuities to result within the cellular nanomatrix
416, even though in the other portions of the powder compact the
nanomatrix is substantially continuous and exhibits the structure
described herein. As used herein, "cellular" is used to indicate
that the nanomatrix defines a network of generally repeating,
interconnected, compartments or cells of nanomatrix material 420
that encompass and also interconnect the dispersed particles 414.
As used herein, "nanomatrix" is used to describe the size or scale
of the matrix, particularly the thickness of the matrix between
adjacent dispersed particles 414. The metallic coating layers that
are sintered together to form the nanomatrix are themselves
nanoscale thickness coating layers. Since the nanomatrix at most
locations, other than the intersection of more than two dispersed
particles 414, generally comprises the interdiffusion and bonding
of two coating layers 216 from adjacent powder particles 212 having
nanoscale thicknesses, the matrix formed also has a nanoscale
thickness (e.g., approximately two times the coating layer
thickness as described herein) and is thus described as a
nanomatrix. Further, the use of the term dispersed particles 414
does not connote the minor constituent of powder compact 400, but
rather refers to the majority constituent or constituents, whether
by weight or by volume. The use of the term dispersed particle is
intended to convey the discontinuous and discrete distribution of
particle core material 418 within powder compact 400.
[0049] Powder compact 400 may have any desired shape or size,
including that of a cylindrical billet or bar that may be machined
or otherwise used to form any desired plug shape or size. The
pressing used to form precursor powder compact and sintering and
pressing processes used to form powder compact 400 and deform the
powder particles 212, including particle cores 214 and coating
layers 216, to provide the full density and desired macroscopic
shape and size of powder compact 400 as well as its microstructure.
The microstructure of powder compact 400 includes an equiaxed
configuration of dispersed particles 414 that are dispersed
throughout and embedded within the substantially-continuous,
cellular nanomatrix 416 of sintered coating layers. This
microstructure is somewhat analogous to an equiaxed grain
microstructure with a continuous grain boundary phase, except that
it does not require the use of alloy constituents having
thermodynamic phase equilibria properties that are capable of
producing such a structure. Rather, this equiaxed dispersed
particle structure and cellular nanomatrix 416 of sintered metallic
coating layers 216 may be produced using constituents where
thermodynamic phase equilibrium conditions would not produce an
equiaxed structure. The equiaxed morphology of the dispersed
particles 414 and cellular network 416 of particle layers results
from sintering and deformation of the powder particles 212 as they
are compacted and interdiffuse and deform to fill the interparticle
spaces 215. The sintering temperatures and pressures may be
selected to ensure that the density of powder compact 400 achieves
substantially full theoretical density.
[0050] In an exemplary embodiment as illustrated in FIGS. 9 and 10,
dispersed particles 414 are formed from particle cores 214
dispersed in the cellular nanomatrix 416 of sintered metallic
coating layers 216, and the nanomatrix 416 includes a solid-state
metallurgical bond 417 or bond layer 419, as illustrated
schematically in FIG. 9, extending between the dispersed particles
414 throughout the cellular nanomatrix 416 that is formed at a
sintering temperature (T.sub.S), where T.sub.S is less than T.sub.C
and T.sub.P. As indicated, solid-state metallurgical bond 417 is
formed in the solid state by solid-state interdiffusion between the
coating layers 216 of adjacent powder particles 212 that are
compressed into touching contact during the compaction and
sintering processes used to form powder compact 400, as described
herein. As such, sintered coating layers 216 of cellular nanomatrix
416 include a solid-state bond layer 419 that has a thickness (t)
defined by the extent of the interdiffusion of the coating
materials 220 of the coating layers 216, which will in turn be
defined by the nature of the coating layers 216, including whether
they are single or multilayer coating layers, whether they have
been selected to promote or limit such interdiffusion, and other
factors, as described herein, as well as the sintering and
compaction conditions, including the sintering time, temperature
and pressure used to form powder compact 400.
[0051] As nanomatrix 416 is formed, including bond 417 and bond
layer 419, the chemical composition or phase distribution, or both,
of metallic coating layers 216 may change. Nanomatrix 416 also has
a melting temperature (T.sub.M). As used herein, T.sub.M includes
the lowest temperature at which incipient melting or liquation or
other forms of partial melting will occur within nanomatrix 416,
regardless of whether nanomatrix material 420 comprises a pure
metal, an alloy with multiple phases each having different melting
temperatures or a composite, including a composite comprising a
plurality of layers of various coating materials having different
melting temperatures, or a combination thereof, or otherwise. As
dispersed particles 414 and particle core materials 418 are formed
in conjunction with nanomatrix 416, diffusion of constituents of
metallic coating layers 216 into the particle cores 214 is also
possible, which may result in changes in the chemical composition
or phase distribution, or both, of particle cores 214. As a result,
dispersed particles 414 and particle core materials 418 may have a
melting temperature (T.sub.DP) that is different than T. As used
herein, T.sub.DP includes the lowest temperature at which incipient
melting or liquation or other forms of partial melting will occur
within dispersed particles 414, regardless of whether particle core
material 418 comprise a pure metal, an alloy with multiple phases
each having different melting temperatures or a composite, or
otherwise. Powder compact 400 is formed at a sintering temperature
(T.sub.S), where T.sub.S is less than T.sub.C, T.sub.P, T.sub.M and
T.sub.DP.
[0052] Dispersed particles 414 may comprise any of the materials
described herein for particle cores 214, even though the chemical
composition of dispersed particles 414 may be different due to
diffusion effects as described herein. In an exemplary embodiment,
dispersed particles 414 are formed from particle cores 214
comprising materials having a standard oxidation potential greater
than or equal to Zn, including Mg, Al, Zn or Mn, or a combination
thereof, may include various binary, tertiary and quaternary alloys
or other combinations of these constituents as disclosed herein in
conjunction with particle cores 214. Of these materials, those
having dispersed particles 414 comprising Mg and the nanomatrix 416
formed from the metallic coating materials 216 described herein are
particularly useful. Dispersed particles 414 and particle core
material 418 of Mg, Al, Zn or Mn, or a combination thereof, may
also include a rare earth element, or a combination of rare earth
elements as disclosed herein in conjunction with particle cores
214.
[0053] In another exemplary embodiment, dispersed particles 414 are
formed from particle cores 214 comprising metals that are less
electrochemically active than Zn or non-metallic materials.
Suitable non-metallic materials include ceramics, glasses (e.g.,
hollow glass microspheres) or carbon, or a combination thereof, as
described herein.
[0054] Dispersed particles 414 of powder compact 400 may have any
suitable particle size, including the average particle sizes
described herein for particle cores 214.
[0055] Dispersed particles 214 may have any suitable shape
depending on the shape selected for particle cores 214 and powder
particles 212, as well as the method used to sinter and compact
powder 210. In an exemplary embodiment, powder particles 212 may be
spheroidal or substantially spheroidal and dispersed particles 414
may include an equiaxed particle configuration as described
herein.
[0056] The nature of the dispersion of dispersed particles 414 may
be affected by the selection of the powder 210 or powders 210 used
to make particle compact 400. In one exemplary embodiment, a powder
210 having a unimodal distribution of powder particle 212 sizes may
be selected to form powder compact 400 and will produce a
substantially homogeneous unimodal dispersion of particle sizes of
dispersed particles 414 within cellular nanomatrix 416, as
illustrated generally in FIG. 8. In another exemplary embodiment, a
plurality of powders 210 having a plurality of powder particles
with particle cores 214 that have the same core materials 218 and
different core sizes and the same coating material 220 may be
selected and uniformly mixed as described herein to provide a
powder 210 having a homogenous, multimodal distribution of powder
particle 212 sizes, and may be used to form powder compact 400
having a homogeneous, multimodal dispersion of particle sizes of
dispersed particles 414 within cellular nanomatrix 416. Similarly,
in yet another exemplary embodiment, a plurality of powders 210
having a plurality of particle cores 214 that may have the same
core materials 218 and different core sizes and the same coating
material 220 may be selected and distributed in a non-uniform
manner to provide a non-homogenous, multimodal distribution of
powder particle sizes, and may be used to form powder compact 400
having a non-homogeneous, multimodal dispersion of particle sizes
of dispersed particles 414 within cellular nanomatrix 416. The
selection of the distribution of particle core size may be used to
determine, for example, the particle size and interparticle spacing
of the dispersed particles 414 within the cellular nanomatrix 416
of powder compacts 400 made from powder 210.
[0057] Nanomatrix 416 is a substantially-continuous, cellular
network of metallic coating layers 216 that are sintered to one
another. The thickness of nanomatrix 416 will depend on the nature
of the powder 210 or powders 210 used to form powder compact 400,
as well as the incorporation of any second powder 230, particularly
the thicknesses of the coating layers associated with these
particles. In an exemplary embodiment, the thickness of nanomatrix
416 is substantially uniform throughout the microstructure of
powder compact 400 and comprises about two times the thickness of
the coating layers 216 of powder particles 212. In another
exemplary embodiment, the cellular network 416 has a substantially
uniform average thickness between dispersed particles 414 of about
50 nm to about 5000 nm.
[0058] Nanomatrix 416 is formed by sintering metallic coating
layers 216 of adjacent particles to one another by interdiffusion
and creation of bond layer 419 as described herein. Metallic
coating layers 216 may be single layer or multilayer structures,
and they may be selected to promote or inhibit diffusion, or both,
within the layer or between the layers of metallic coating layer
216, or between the metallic coating layer 216 and particle core
214, or between the metallic coating layer 216 and the metallic
coating layer 216 of an adjacent powder particle, the extent of
interdiffusion of metallic coating layers 216 during sintering may
be limited or extensive depending on the coating thicknesses,
coating material or materials selected, the sintering conditions
and other factors. Given the potential complexity of the
interdiffusion and interaction of the constituents, description of
the resulting chemical composition of nanomatrix 416 and nanomatrix
material 420 may be simply understood to be a combination of the
constituents of coating layers 216 that may also include one or
more constituents of dispersed particles 414, depending on the
extent of interdiffusion, if any, that occurs between the dispersed
particles 414 and the nanomatrix 416. Similarly, the chemical
composition of dispersed particles 414 and particle core material
418 may be simply understood to be a combination of the
constituents of particle core 214 that may also include one or more
constituents of nanomatrix 416 and nanomatrix material 420,
depending on the extent of interdiffusion, if any, that occurs
between the dispersed particles 414 and the nanomatrix 416.
[0059] In an exemplary embodiment, the nanomatrix material 420 has
a chemical composition and the particle core material 418 has a
chemical composition that is different from that of nanomatrix
material 420, and the differences in the chemical compositions may
be configured to provide a selectable and controllable dissolution
rate, including a selectable transition from a very low dissolution
rate to a very rapid dissolution rate, in response to a controlled
change in a property or condition of the wellbore proximate the
compact 400, including a property change in a wellbore fluid that
is in contact with the powder compact 400, as described herein.
Nanomatrix 416 may be formed from powder particles 212 having
single layer and multilayer coating layers 216. This design
flexibility provides a large number of material combinations,
particularly in the case of multilayer coating layers 216, that can
be utilized to tailor the cellular nanomatrix 416 and composition
of nanomatrix material 420 by controlling the interaction of the
coating layer constituents, both within a given layer, as well as
between a coating layer 216 and the particle core 214 with which it
is associated or a coating layer 216 of an adjacent powder particle
212. Several exemplary embodiments that demonstrate this
flexibility are provided below.
[0060] As illustrated in FIG. 9, in an exemplary embodiment, powder
compact 400 is formed from powder particles 212 where the coating
layer 216 comprises a single layer, and the resulting nanomatrix
416 between adjacent ones of the plurality of dispersed particles
414 comprises the single metallic coating layer 216 of one powder
particle 212, a bond layer 419 and the single coating layer 216 of
another one of the adjacent powder particles 212. The thickness (t)
of bond layer 419 is determined by the extent of the interdiffusion
between the single metallic coating layers 216, and may encompass
the entire thickness of nanomatrix 416 or only a portion thereof In
one exemplary embodiment of powder compact 400 formed using a
single layer powder 210, powder compact 400 may include dispersed
particles 414 comprising Mg, Al, Zn or Mn, or a combination
thereof, as described herein, and nanomatrix 216 may include Al,
Zn, Mn, Mg, Mo, W, Cu, Fe, Si, Ca, Co, Ta, Re or Ni, or an oxide,
carbide or nitride thereof, or a combination of any of the
aforementioned materials, including combinations where the
nanomatrix material 420 of cellular nanomatrix 416, including bond
layer 419, has a chemical composition and the core material 418 of
dispersed particles 414 has a chemical composition that is
different than the chemical composition of nanomatrix material 416.
The difference in the chemical composition of the nanomatrix
material 420 and the core material 418 may be used to provide
selectable and controllable dissolution in response to a change in
a property of a wellbore, including a wellbore fluid, as described
herein. In a further exemplary embodiment of a powder compact 400
formed from a powder 210 having a single coating layer
configuration, dispersed particles 414 include Mg, Al, Zn or Mn, or
a combination thereof, and the cellular nanomatrix 416 includes Al
or Ni, or a combination thereof
[0061] As illustrated in FIG. 10, in another exemplary embodiment,
powder compact 400 is formed from powder particles 212 where the
coating layer 216 comprises a multilayer coating layer 216 having a
plurality of coating layers, and the resulting nanomatrix 416
between adjacent ones of the plurality of dispersed particles 414
comprises the plurality of layers (t) comprising the coating layer
216 of one particle 212, a bond layer 419, and the plurality of
layers comprising the coating layer 216 of another one of powder
particles 212. In FIG. 10, this is illustrated with a two-layer
metallic coating layer 216, but it will be understood that the
plurality of layers of multi-layer metallic coating layer 216 may
include any desired number of layers. The thickness (t) of the bond
layer 419 is again determined by the extent of the interdiffusion
between the plurality of layers of the respective coating layers
216, and may encompass the entire thickness of nanomatrix 416 or
only a portion thereof In this embodiment, the plurality of layers
comprising each coating layer 216 may be used to control
interdiffusion and formation of bond layer 419 and thickness
(t).
[0062] Sintered and forged powder compacts 400 that include
dispersed particles 414 comprising Mg and nanomatrix 416 comprising
various nanomatrix materials as described herein have demonstrated
an excellent combination of mechanical strength and low density
that exemplify the lightweight, high-strength materials disclosed
herein. Examples of powder compacts 400 that have pure Mg dispersed
particles 414 and various nanomatrices 416 formed from powders 210
having pure Mg particle cores 214 and various single and multilayer
metallic coating layers 216 that include Al, Ni, W or
Al.sub.2O.sub.3, or a combination thereof These powders compacts
400 have been subjected to various mechanical and other testing,
including density testing, and their dissolution and mechanical
property degradation behavior has also been characterized as
disclosed herein. The results indicate that these materials may be
configured to provide a wide range of selectable and controllable
corrosion or dissolution behavior from very low corrosion rates to
extremely high corrosion rates, particularly corrosion rates that
are both lower and higher than those of powder compacts that do not
incorporate the cellular nanomatrix, such as a compact formed from
pure Mg powder through the same compaction and sintering processes
in comparison to those that include pure Mg dispersed particles in
the various cellular nanomatrices described herein. These powder
compacts 400 may also be configured to provide substantially
enhanced properties as compared to powder compacts formed from pure
Mg particles that do not include the nanoscale coatings described
herein. Powder compacts 400 that include dispersed particles 414
comprising Mg and nanomatrix 416 comprising various nanomatrix
materials 420 described herein have demonstrated room temperature
compressive strengths of at least about 37 ksi, and have further
demonstrated room temperature compressive strengths in excess of
about 50 ksi, both dry and immersed in a solution of 3% KCl at
200.degree. F. In contrast, powder compacts formed from pure Mg
powders have a compressive strength of about 20 ksi or less.
Strength of the nanomatrix powder metal compact 400 can be further
improved by optimizing powder 210, particularly the weight
percentage of the nanoscale metallic coating layers 216 that are
used to form cellular nanomatrix 416. Strength of the nanomatrix
powder metal compact 400 can be further improved by optimizing
powder 210, particularly the weight percentage of the nanoscale
metallic coating layers 216 that are used to form cellular
nanomatrix 416. For example, varying the weight percentage (wt. %),
i.e., thickness, of an alumina coating within a cellular nanomatrix
16 formed from coated powder particles 212 that include a
multilayer (Al/Al.sub.2O.sub.3/Al) metallic coating layer 16 on
pure Mg particle cores 214 provides an increase of 21% as compared
to that of 0 wt % alumina.
[0063] Powder compacts 400 comprising dispersed particles 414 that
include Mg and nanomatrix 416 that includes various nanomatrix
materials as described herein have also demonstrated a room
temperature sheer strength of at least about 20 ksi. This is in
contrast with powder compacts formed from pure Mg powders, which
have room temperature sheer strengths of about 8 ksi.
[0064] Powder compacts 400 of the types disclosed herein are able
to achieve an actual density that is substantially equal to the
predetermined theoretical density of a compact material based on
the composition of powder 210, including relative amounts of
constituents of particle cores 214 and metallic coating layer 216,
and are also described herein as being fully-dense powder compacts.
Powder compacts 400 comprising dispersed particles that include Mg
and nanomatrix 416 that includes various nanomatrix materials as
described herein have demonstrated actual densities of about 1.738
g/cm.sup.3 to about 2.50 g/cm.sup.3, which are substantially equal
to the predetermined theoretical densities, differing by at most 4%
from the predetermined theoretical densities.
[0065] Powder compacts 400 as disclosed herein may be configured to
be selectively and controllably dissolvable in a wellbore fluid in
response to a changed condition in a wellbore. Examples of the
changed condition that may be exploited to provide selectable and
controllable dissolvability include a change in temperature, change
in pressure, change in flow rate, change in pH or change in
chemical composition of the wellbore fluid, or a combination
thereof An example of a changed condition comprising a change in
temperature includes a change in well bore fluid temperature. For
example, powder compacts 400 comprising dispersed particles 414
that include Mg and cellular nanomatrix 416 that includes various
nanomatrix materials as described herein have relatively low rates
of corrosion in a 3% KCl solution at room temperature that range
from about 0 to about 11 mg/cm.sup.2/hr as compared to relatively
high rates of corrosion at 200.degree. F. that range from about 1
to about 246 mg/cm.sup.2/hr depending on different nanoscale
coating layers 216. An example of a changed condition comprising a
change in chemical composition includes a change in a chloride ion
concentration or pH value, or both, of the wellbore fluid. For
example, powder compacts 400 comprising dispersed particles 414
that include Mg and nanomatrix 416 that includes various nanoscale
coatings described herein demonstrate corrosion rates in 15% HCl
that range from about 4750 mg/cm.sup.2/hr to about 7432
mg/cm.sup.2/hr. Thus, selectable and controllable dissolvability in
response to a changed condition in the wellbore, namely the change
in the wellbore fluid chemical composition from KCl to HCl, may be
used to achieve a characteristic response as illustrated
graphically in FIG. 11, which illustrates that at a selected
predetermined critical service time (CST) a changed condition may
be imposed upon powder compact 400 as it is applied in a given
application, such as a wellbore environment, that causes a
controllable change in a property of powder compact 400 in response
to a changed condition in the environment in which it is applied.
For example, at a predetermined CST changing a wellbore fluid that
is in contact with powder contact 400 from a first fluid (e.g. KCl)
that provides a first corrosion rate and an associated weight loss
or strength as a function of time to a second wellbore fluid (e.g.,
HCl) that provides a second corrosion rate and associated weight
loss and strength as a function of time, wherein the corrosion rate
associated with the first fluid is much less than the corrosion
rate associated with the second fluid. This characteristic response
to a change in wellbore fluid conditions may be used, for example,
to associate the critical service time with a dimension loss limit
or a minimum strength needed for a particular application, such
that when a wellbore tool or component formed from powder compact
400 as disclosed herein is no longer needed in service in the
wellbore (e.g., the CST) the condition in the wellbore (e.g., the
chloride ion concentration of the wellbore fluid) may be changed to
cause the rapid dissolution of powder compact 400 and its removal
from the wellbore. In the example described above, powder compact
400 is selectably dissolvable at a rate that ranges from about 0 to
about 7000 mg/cm.sup.2/hr. This range of response provides, for
example the ability to remove a 3 inch diameter ball formed from
this material from a wellbore by altering the wellbore fluid in
less than one hour. The selectable and controllable dissolvability
behavior described above, coupled with the excellent strength and
low density properties described herein, define a new engineered
dispersed particle-nanomatrix material that is configured for
contact with a fluid and configured to provide a selectable and
controllable transition from one of a first strength condition to a
second strength condition that is lower than a functional strength
threshold, or a first weight loss amount to a second weight loss
amount that is greater than a weight loss limit, as a function of
time in contact with the fluid. The dispersed particle-nanomatrix
composite is characteristic of the powder compacts 400 described
herein and includes a cellular nanomatrix 416 of nanomatrix
material 420, a plurality of dispersed particles 414 including
particle core material 418 that is dispersed within the matrix.
Nanomatrix 416 is characterized by a solid-state bond layer 419,
which extends throughout the nanomatrix. The time in contact with
the fluid described above may include the CST as described above.
The CST may include a predetermined time that is desired or
required to dissolve a predetermined portion of the powder compact
200 that is in contact with the fluid. The CST may also include a
time corresponding to a change in the property of the engineered
material or the fluid, or a combination thereof In the case of a
change of property of the engineered material, the change may
include a change of a temperature of the engineered material. In
the case where there is a change in the property of the fluid, the
change may include the change in a fluid temperature, pressure,
flow rate, chemical composition or pH or a combination thereof Both
the engineered material and the change in the property of the
engineered material or the fluid, or a combination thereof, may be
tailored to provide the desired CST response characteristic,
including the rate of change of the particular property (e.g.,
weight loss, loss of strength) both prior to the CST (e.g., Stage
1) and after the CST (e.g., Stage 2), as illustrated in FIG.
11.
[0066] Without being limited by theory, powder compacts 400 are
formed from coated powder particles 212 that include a particle
core 214 and associated core material 218 as well as a metallic
coating layer 216 and an associated metallic coating material 220
to form a substantially-continuous, three-dimensional, cellular
nanomatrix 416 that includes a nanomatrix material 420 formed by
sintering and the associated diffusion bonding of the respective
coating layers 216 that includes a plurality of dispersed particles
414 of the particle core materials 418. This unique structure may
include metastable combinations of materials that would be very
difficult or impossible to form by solidification from a melt
having the same relative amounts of the constituent materials. The
coating layers and associated coating materials may be selected to
provide selectable and controllable dissolution in a predetermined
fluid environment, such as a wellbore environment, where the
predetermined fluid may be a commonly used wellbore fluid that is
either injected into the wellbore or extracted from the wellbore.
As will be further understood from the description herein,
controlled dissolution of the nanomatrix exposes the dispersed
particles of the core materials. The particle core materials may
also be selected to also provide selectable and controllable
dissolution in the wellbore fluid. Alternately, they may also be
selected to provide a particular mechanical property, such as
compressive strength or sheer strength, to the powder compact 400,
without necessarily providing selectable and controlled dissolution
of the core materials themselves, since selectable and controlled
dissolution of the nanomatrix material surrounding these particles
will necessarily release them so that they are carried away by the
wellbore fluid. The microstructural morphology of the
substantially-continuous, cellular nanomatrix 416, which may be
selected to provide a strengthening phase material, with dispersed
particles 414, which may be selected to provide equiaxed dispersed
particles 414, provides these powder compacts with enhanced
mechanical properties, including compressive strength and sheer
strength, since the resulting morphology of the
nanomatrix/dispersed particles can be manipulated to provide
strengthening through the processes that are akin to traditional
strengthening mechanisms, such as grain size reduction, solution
hardening through the use of impurity atoms, precipitation or age
hardening and strength/work hardening mechanisms. The
nanomatrix/dispersed particle structure tends to limit dislocation
movement by virtue of the numerous particle nanomatrix interfaces,
as well as interfaces between discrete layers within the nanomatrix
material as described herein. This is exemplified in the fracture
behavior of these materials. A powder compact 400 made using
uncoated pure Mg powder and subjected to a shear stress sufficient
to induce failure demonstrated intergranular fracture. In contrast,
a powder compact 400 made using powder particles 212 having pure Mg
powder particle cores 214 to form dispersed particles 414 and
metallic coating layers 216 that includes Al to form nanomatrix 416
and subjected to a shear stress sufficient to induce failure
demonstrated transgranular fracture and a substantially higher
fracture stress as described herein. Because these materials have
high-strength characteristics, the core material and coating
material may be selected to utilize low density materials or other
low density materials, such as low-density metals, ceramics,
glasses or carbon, that otherwise would not provide the necessary
strength characteristics for use in the desired applications,
including wellbore tools and components.
[0067] FIG. 12 illustrates a method 500 of controlling production
in a borehole. The method is performed in conjunction with a gas
lift tool such as the gas lift assembly 120. The method 500
includes one or more stages 510-550. Although the method is
described in conjunction with the tool 120, the method can be
utilized in conjunction with any gas lift device or system.
[0068] In the first stage 510, in one embodiment, the production
string 112 and the gas lift assembly 120 is deployed to a downhole
location. In one embodiment, the gas lift assembly 120 is assembled
and secured in a portion of the production string or other carrier
prior to deployment. The gas lift assembly 120 is then disposed
with the production string 112. At this stage, the gas lift valve
is configured as a dummy valve until the gas lift plug 142 is
actuated.
[0069] In the second stage 520, hydrocarbon fluids and/or gases are
produced to the surface via the production conduit 122. Stage 520
is performed in any suitable manner and may include various
production methods and facilitating methods such as perforating the
casing and/or borehole wall and fracing. Production may include
various additional procedures that may be performed to facilitate
production. For example, after the completion and gas lift
assemblies are disposed in the well, it may be desirable to test
the annulus or tubing to insure the pressure integrity of the
completion. In addition, some completion scenarios include
circulating cement of other fluid down the tubing or annulus of the
well. During these production procedures, the gas lift assembly 120
acts as a blank or dummy to prevent any circulation through the gas
lift assembly 120 and between annular regions and the production
conduit 122.
[0070] In the third stage 530, the gas lift plug 142 is exposed to
downhole fluids, such as production fluids and water to actuate the
gas lift plug 142 and cause the pressurized gas to enter the
production conduit. In one embodiment, the gas lift plug is made
from a corrodible or dissolvable material. During production,
production fluid, which may include water, hydrocarbon fluids
and/or hydrocarbon gases (as well as other gases and chemical
constituents) contacts the dissolvable/corrodable plug 142.
Depending on the configuration and/or size of the plug 142, the
plug 142 dissolves over a period of time until the plug 142
completely dissolves/corrodes or is at least sufficiently reduced
in size so that the pressurized gas can force the plug away from
the gas lift assembly 120 and/or the production fluid can dislodge
the plug 142 and carry it away.
[0071] In the fourth stage 540, over a period of time at least a
portion of the gas lift plug 142 will dissolve, corrode and/or be
removed without mechanical intervention to allow the gas lift
assembly 120 to function as designed. In one embodiment, the plug
is made of a material(s) having an approximately known dissolution
or corrosion rate in the presence of the downhole fluids, and is
shaped, sized or otherwise configured to dissolve or corrode over a
pre-determined period of time.
[0072] In the fifth stage 550, the gas lift procedure may be
commenced. Gas lift may be started at any time after the plug is
dissolved. This may be immediately or soon after the plug 142 is
dissolved, or may be commenced at some later time dependent on, for
example, the production pressure or flow rate of the fluid being
produced through the production conduit 122.
[0073] In one embodiment, the gas lift procedure includes injecting
pressurized gas from an annular area in the borehole 114 through
the gas lift assembly 120, e.g., through the ports 124. The
pressurized gas flows through the gas lift assembly 120, and into
the production conduit 122, where the pressurized gas displaces
and/or aeriates the production fluids and gases an enables them to
flow to the surface. In one embodiment, the gas lift valve 132 is
used to control flow of pressurized gas into the production
conduit.
[0074] The apparatuses and methods described herein provide various
advantages over prior art techniques. For example, in instances
where it is desirable to install the gas lift assembly after the
production assembly is deployed downhole, the gas lift plug allows
the gas lift assembly to act as a dummy or blank for a period of
time. This eliminates the need to for using a separate dummy or
blank which would require subsequent installation (e.g., slickline
intervention) after the completion to remove the dummy valves and
install live gas lift assemblies.
[0075] While the invention has been described with reference to
exemplary embodiments, it will be understood by those skilled in
the art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications will be
appreciated by those skilled in the art to adapt a particular
instrument, situation or material to the teachings of the invention
without departing from the essential scope thereof Therefore, it is
intended that the invention not be limited to the particular
embodiment disclosed as the best mode contemplated for carrying out
this invention, but that the invention will include all embodiments
falling within the scope of the appended claims.
* * * * *