Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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AQUEOUS-BASED INSULATING FLUIDS AND RELATED METHODS
BACKGROUND
The present invention relates to insulating fluids, and more particularly, to
aqueous-based insulating fluids that have greater stability at high
temperatures with lower
thermal conductivity that may be used, for example, in applications requiring
an insulating
fluid such as pipeline and subterranean applications (e.g., to insulate
petroleum production
conduits).
Insulating fluids are often used in subterranean operations wherein the fluid
is
placed into an annulus between a first tubing and a second tubing or the walls
of a well
bore. The insulating fluid acts to insulate a first fluid (e.g., a hydrocarbon
fluid) that may be
located within the first tubing from the environment surrounding the first
tubing or the
second tubing to enable optimum recovery of the hydrocarbon fluid. For
instance, if the
surrounding environment is very cold, the insulating fluid is thought to
protect the first fluid
in the first tubing from the environment so that it can efficiently flow
through the production
tubing, e.g., the first tubing, to other facilities. This is desirable because
heat transfer can
cause problems such as the precipitation of heavier hydrocarbons, severe
reductions in
flow rate, and in some cases, casing collapse. Additionally, when used in
packer
applications, a required amount of hydrostatic head pressure is needed. Thus,
higher
density insulating fluids are often used for this reason as well to provide
the requisite
hydrostatic force.
Such fluids also may be used for similar applications involving pipelines for
similar purposes, e.g., to protect a fluid located within the pipeline from
the surrounding
environmental conditions so that the fluid can efficiently flow through the
pipeline.
Insulating fluids can be used in other insulating applications as well wherein
it is desirable
to control heat transfer. These applications may or may not involve
hydrocarbons.
Beneficial insulating fluids preferably have a low inherent thermal
conductivity,
and also should remain gelled to prevent, inter alia, convection currents that
could carry
heat away. Additionally, preferred insulating fluids should be aqueous-based,
and easy to
handle and use. Moreover, preferred fluids should tolerate ultra high
temperatures (e.g.,
temperatures of 400 F or above) for long periods of time for optimum
performance.
Conventional aqueous-based insulating fluids have been subject to many
drawbacks. First, many have associated temperature limitations. Typically,
most aqueous-
based insulating fluids are only stable up to 240 F for relatively short
periods of time. This
can be problematic because it can result in premature degradation of the
fluid, which can
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cause the fluid not to perform its desired function with respect to insulating
the first fluid. A
second common limitation of many conventional aqueous-based insulating fluids
is their
density range. Typically, these fluids have an upper density limit of 12.5
ppg. Oftentimes,
higher densities are desirable to maintain adequate pressure for the chosen
application.
Additionally, most aqueous-based insulating fluids have excessive thermal
conductivities,
which means that these fluids are not as efficient or effective at controlling
conductive heat
transfer. Moreover, when a viscosified fluid is required to eliminate
convective currents,
oftentimes to obtain the required viscosity in current aqueous-based fluids,
the fluids may
become too thick to be able to pump into place. Some aqueous-based fluids also
can have
different salt tolerances that may not be compatible with various brines used,
which limits
the operators' options as to what fluids to use in certain circumstances.
In some instances, insulating fluids may be oil-based. Certain oil-based
fluids
may offer an advantage because they may have lower thermal conductivity as
compared to
their aqueous counterparts. However, many disadvantages are associated with
these fluids
as well. First, oil-based insulating fluids can be hard to "weight up,"
meaning that it may be
hard to obtain the necessary density required for an application. Secondly,
oil-based fluids
may present toxicity and other environmental issues that must be managed,
especially
when such fluids are used in sub-sea applications. Additionally, there can be
interface
issues if aqueous completion fluids are used. Another complication presented
when using
oil-based insulating fluids is the concern about their compatibility with any
elastomeric
seals that may be present along the first tubing line.
Another method that may be employed to insulate a first tubing involves using
vacuum insulated tubing. However, this method also can present disadvantages.
First,
when the vacuum tubing is installed on a completion string, sections of the
vacuum tubing
can fail. This can be a costly problem involving a lot of down time. In severe
cases, the first
tubing can collapse. Secondly, vacuum insulated tubing can be very costly and
hard to
place. Moreover, in many instances, heat transfer at the junctions or
connective joints in
the vacuum tubings can be problematic. These may lead to "hot spots" in the
tubings.
SUMMARY
The present invention relates to insulating fluids, and more particularly, to
aqueous-based insulating fluids that have greater stability at high
temperatures with lower
thermal conductivity that may be used, for example, in applications requiring
an insulating
fluid such as pipeline and subterranean applications (e.g., to insulate
petroleum production
conduits).
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In one embodiment, the present invention provides a method comprising:
providing an annulus between a first tubing and a second tubing; providing an
aqueous-
based insulating fluid that comprises an aqueous base fluid, a water-miscible
organic
liquid, and a layered silicate; and placing the aqueous-based insulating fluid
in the annulus.
In some embodiments, the aqueous-based insulating fluid also includes a
polymer.
In one embodiment, the present invention provides a method comprising:
providing a tubing containing a first fluid located within a well bore such
that an annulus is
formed between the tubing and a surface of the well bore; providing an aqueous-
based
insulating fluid that comprises an aqueous base fluid, a water-miscible
organic liquid, and a
layered silicate; and placing the aqueous-based insulating fluid in the
annulus. In some
embodiments, the aqueous-based insulating fluid also includes a polymer.
In one embodiment, the present invention provides a method comprising:
providing a first tubing that comprises at least a portion of a pipeline that
contains a first
fluid; providing a second tubing that substantially surrounds the first tubing
thus creating an
annulus between the first tubing and the second tubing; providing an aqueous-
based
insulating fluid that comprises an aqueous base fluid, a water-miscible
organic liquid, and a
layered silicate; and placing the aqueous-based insulating fluid in the
annulus. In some
embodiments, the aqueous-based insulating fluid also includes a polymer.
In one embodiment, the present invention provides an aqueous-based insulating
fluid that comprises an aqueous base fluid, a water-miscible organic liquid,
and a layered
silicate. In some embodiments, the aqueous-based insulating fluid also
includes a
polymer.
In another embodiment, the present invention provides a method of forming an
aqueous-based insulating fluid comprising: mixing an aqueous base fluid and a
water-
miscible organic liquid to form a mixture; adding at least one layered
silicate to the mixture;
allowing the silicate to hydrate; placing the mixture comprising the layered
silicate in a
chosen location; allowing the mixture comprising the layered silicate to
activate to form a
gel therein. In some embodiments, a polymer may be added to the mixture and
allowed to
hydrate. Optionally, a crosslinking agent may be added to the mixture
comprising the
polymer to crosslink the polymer.
The features and advantages of the present invention will be readily apparent
to
those skilled in the art.
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BRIEF DESCRIPTION OF THE DRAWINGS
These drawings illustrate certain aspects of some of the embodiments of the
present invention, and should not be used to limit or define the invention.
Figure 1 illustrates data from a fluid that was heated to about 190 F for 5000
minutes to activate the crosslinking agent and provide an increase in
viscosity.
Figure 2 illustrates data from a fluid that was heated from approximately 100
F
to approximately 600 F for approximately 45,000 seconds at approximately
10,000 psi.
DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention relates to insulating fluids, and more particularly, to
aqueous-based insulating fluids that have greater stability at high
temperatures with lower
thermal conductivity that may be used, for example, in applications requiring
an insulating
fluid such as pipeline and subterranean applications (e.g., to insulate
petroleum production
conduits). The aqueous-based insulating fluids of the present invention may be
used in any
application requiring an insulating fluid. Preferably, they may be used in
pipeline and
subterranean applications.
The improved aqueous-based insulating fluids and methods of the present
invention present many potential advantages, only some of which are alluded to
herein.
One of these many advantages is that the fluids may have enhanced thermal
stability,
which enables them to be beneficially used in many applications. Secondly, in
some
embodiments, the aqueous-based insulating fluids of the present invention may
have
higher densities than conventional aqueous-based insulating fluids, and
therefore, present
a distinct advantage in that respect. Additionally, the aqueous-based
insulating fluids of the
present invention have relatively low thermal conductivity, which is thought
to be especially
beneficial in certain applications. In some embodiments, these fluids are
believed to be
very durable. Moreover, in some embodiments, the fluids of the present
invention offer
aqueous-based viscous insulating fluids with a broad fluid density range,
decreased
thermal conductivity, and stable gel properties at temperatures exceeding
those of current
industry standards (e.g., even at temperatures of about 600 F or more,
depending on the
organic liquid included). Another potential advantage is that these fluids may
prevent the
formation of hydrates within the insulating fluids themselves or the fluids
being insulated.
Other advantages and objects of the invention may be apparent to one skilled
in the art
with the benefit of this disclosure.
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In certain embodiments, the aqueous-based insulating fluids of the present
invention comprise an aqueous base fluid, a water-miscible organic liquid, and
a layered
silicate. In certain embodiments, the aqueous-based insulating fluids of the
present
invention comprise an aqueous base fluid, a water-miscible organic liquid, a
layered
5 silicate, and optionally a synthetic polymer. In some instances, the polymer
may be
crosslinked by using or adding to the fluid an appropriate crosslinking agent.
Thus, the term
"polymer" as used herein refers to oligomers, copolymers, terpolymers and the
like, which
may or may not be crosslinked. Optionally, the aqueous-based insulating fluids
of the
present invention may comprise other additives such as corrosion inhibitors,
pH modifiers,
biocides, glass beads, hollow spheres (e.g., hollow microspheres), rheology
modifiers,
buffers, hydrate inhibitors, breakers, tracers, additional weighting agents,
viscosifiers,
surfactants, and combinations of any of these. Other additives may be
appropriate as well
and beneficially used in conjunction with the aqueous-based insulating fluids
of the present
invention as may be recognized by one skilled in the art with the benefit of
this disclosure.
The aqueous base fluids that may be used in the aqueous-based insulating
fluids of the present invention include any aqueous fluid suitable for use in
insulating,
subterranean, or pipeline applications. In some instances, brines may be used,
for
example, when a relatively denser aqueous-based insulating fluid is desired
(e.g., density
of 10.5 ppg or greater); however, it may be observed that the fluids of the
present invention
may be less tolerant to higher concentrations of salts than other fluids, such
as those that
include a polymer as described herein but not a layered silicate as described
herein.
Suitable brines include, but are not limited to: NaCl, NaBr, KCI, CaCl2,
CaBr2, ZrBr2,
sodium carbonate, sodium formate, potassium formate, cesium formate, and
combinations
and derivatives of these brines. Others may be appropriate as well. The
specific brine
used may be dictated by the desired density of the resulting aqueous-based
insulating fluid
or for compatibility with other completion fluid brines that may be present.
Denser brines
may be useful in some instances. A density that is suitable for the
application at issue
should be used as recognized by one skilled in the art with the benefit of
this disclosure.
When deciding how much of an aqueous fluid to include, a general guideline to
follow is
that the aqueous fluid component should comprise the balance of a high
temperature
aqueous-based insulating fluid after considering the amount of the other
components
present therein.
The water-miscible organic liquids that may be included in the aqueous-based
insulating fluids of the present invention include water-miscible materials
having relatively
low thermal conductivity (e.g., about half as conductive as water or less). By
"water-
miscible", it is meant that about 5 grams or more of the organic liquid will
disperse in 100
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grams of water. Suitable water-miscible organic liquids include, but are not
limited to,
esters, amines, alcohols, polyols, glycol ethers, or combinations and
derivatives of these.
Examples of suitable esters include low molecular weight esters; specific
examples
include, but are not limited to, methylformate, methyl acetate, and ethyl
acetate.
Combinations and derivatives are also suitable. Examples of suitable amines
include low
molecular weight amines; specific examples include, but are not limited to,
diethyl amine,
2-aminoethanol, and 2-(dimethylamino)ethanol. Combinations and derivatives are
also
suitable. Examples of suitable alcohols include methanol, ethanol, propanol,
isopropanol,
and the like. Combinations and derivatives are also suitable. Examples of
glycol ethers
include ethylene glycol butyl ether, diethylene glycol methyl ether,
dipropylene glycol
methyl ether, tripropylene glycol methyl ether, and the like. Combinations and
derivatives
are also suitable. Of these, polyols are generally preferred in most cases
over the other
liquids since they generally are thought to exhibit greater thermal and
chemical stability,
higher flash point values, and are more benign with respect to elastomeric
materials.
Suitable polyols are those aliphatic alcohols containing two or more hydroxy
groups. It is preferred that the polyol be at least partially water-miscible.
Examples of
suitable polyols that may be used in the aqueous-based insulating fluids of
this invention
include, but are not limited to, water-soluble diols such as ethylene glycols,
propylene
glycols, polyethylene glycols, polypropylene glycols, diethylene glycols,
triethylene glycols,
dipropylene glycols and tripropylene glycols, combinations of these glycols,
their
derivatives, and reaction products formed by reacting ethylene and propylene
oxide or
polyethylene glycols and polypropylene glycols with active hydrogen base
compounds
(e.g., polyalcohols, polycarboxylic acids, polyamines, or polyphenols). The
polyglycols of
ethylene generally are thought to be water-miscible at molecular weights at
least as high as
20,000. The polyglycols of propylene, although giving slightly better grinding
efficiency than
the ethylene glycols, are thought to be water-miscible up to molecular weights
of only about
1,000. Other glycols possibly contemplated include neopentyl glycol,
pentanediols,
butanediols, and such unsaturated diols as butyne diols and butene diols. In
addition to the
diols, the triol, glycerol, and such derivatives as ethylene or propylene
oxide adducts may
be used. Other higher polyols may include pentaerythritol. Another class of
polyhydroxy
alcohols contemplated is the sugar alcohols. The sugar alcohols are obtained
by reduction
of carbohydrates and differ greatly from the above-mentioned polyols.
Combinations and
derivatives of these are suitable as well.
The choice of polyol to be used is largely dependent on the desired density of
the fluid. Other factors to consider include thermal conductivity. For higher
density fluids
(e.g., 10.5 ppg or higher), a higher density polyol may be preferred, for
instance, triethylene
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glycol or glycerol may be desirable in some instances. For lower density
applications,
ethylene or propylene glycol may be used. In some instances, more salt may be
necessary
to adequately weight the fluid to the desired density. In certain embodiments,
the amount of
polyol that should be used may be governed by the thermal conductivity ceiling
of the fluid
and the desired density of the fluid. If the thermal conductivity ceiling is
0.17 BTU/hft F,
then the concentration of the polyol may be from about 40% to about 99% of a
high
temperature aqueous-based insulating fluid of the present invention. A more
preferred
range could be from about 70% to about 99%.
Examples of layered silicates that may be suitable for use in the present
invention include, but are not limited to, smectite, vermiculite, swellable
fluoromica,
montmorillonite, beidellite, hectorite, and saponite. A high-temperature,
electrolyte stable
synthetic hectorite may be particularly useful in some embodiments. An example
of a
synthetic hectorite clay for use in accordance with this invention is
"LAPONITE(TM) RD"
commercially available from Laporte Absorbents Company of Cheshire, United
Kingdom.
Mixtures of any of these of silicates may be suitable as well. In preferred
embodiments, the
silicate may be at least partially water soluble. In some embodiments, the
layered silicate
may be a natural layered silicate or a synthetic layered silicate. In certain
embodiments, the
silicate should comprise from about 0.1% to about 15% weight by volume of the
fluid, and
more preferably, from about 0.5% to about 4% weight by volume of the fluid.
Inclusion of a synthetic polymer may be useful, inter alia, to produce fluids
that
exhibit gelation behavior. Examples of synthetic polymers that optionally may
be suitable
for use in the present invention include, but are not limited to, acrylic acid
polymers, acrylic
acid ester polymers, acrylic acid derivative polymers, acrylic acid
homopolymers, acrylic
acid ester homopolymers (such as poly(methyl acrylate), poly(butyl acrylate),
and poly(2-
ethylhexyl acrylate)), acrylic acid ester co-polymers, methacrylic acid
derivative polymers,
methacrylic acid homopolymers, methacrylic acid ester homopolymers (such as
poly(methyl methacrylate), polyacrylamide homopolymer, n-vinyl pyrrolidone and
polyacrylamide copolymers, poly(butyl methacrylate), and poly(2-ethylhexyl
methacrylate)),
n-vinyl pyrrolidone, acrylamido-methyl-propane sulfonate polymers, acrylamido-
m ethyl-
propane sulfonate derivative polymers, acrylamido-methyl-propane sulfonate co-
polymers,
and acrylic acid/acrylamido-methyl-propane sulfonate copolymers, and
combinations
thereof. Copolymers and terpolymers may be suitable as well. Mixtures of any
of these of
polymers may be suitable as well. In preferred embodiments, the polymer should
be at
least partially water soluble. Suitable polymers can be cationic, anionic,
nonionic, or
zwitterionic. In certain embodiments, the polymer should comprise from about
0.1% to
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about 15% weight by volume of the fluid, and more preferably, from about 0.5%
to about
4%.
To obtain the desired gel characteristics and thermal stability for an aqueous-
based insulating fluid of the present invention, the polymer included in the
fluid may be
crosslinked by an appropriate crosslinking agent. In those embodiments of the
present
invention wherein it is desirable to crosslink the polymer, optionally and
preferably, one or
more crosslinking agents may be added to the fluid to crosslink the polymer.
One type of suitable crosslinking agent is a combination of a phenolic
component (or a phenolic precursor) and formaldehyde (or formaldehyde
precursor).
Suitable phenolic components or phenolic precursors include, but are not
limited to,
phenols, hydroquinone, salicylic acid, salicylamide, aspirin, methyl-p-
hydroxybenzoate,
phenyl acetate, phenyl salicylate, o-aminobenzoic acid, p-aminobenzoic acid, m-
aminophenol, furfuryl alcohol, and benzoic acid. Suitable formaldehyde
precursors may
include, but are not limited to, hexamethylenetetramine, glyoxal, and 1,3,5-
trioxane. This
crosslinking agent system needs approximately 250 F to thermally activate to
crosslink the
polymer. Another type of suitable crosslinking agent is polyalkylimine. This
crosslinking
agent needs approximately 90 F to activate to crosslink the polymer. This
crosslinking
agent may be used alone or in conjunction with any of the other crosslinking
agents
discussed herein.
Another type of crosslinking agent that may be used includes non-toxic organic
crosslinking agents that are free from metal ions. Examples of such organic
cross-linking
agents are polyalkyleneimines (e.g., polyethyleneimine),
polyalkylenepolyamines and
mixtures thereof. In addition, water-soluble polyfunctional aliphatic amines,
arylalkylamines
and heteroarylalkylamines may be utilized.
When included, suitable crosslinking agents may be present in the fluids of
the
present invention in an amount sufficient to provide, inter alia, the desired
degree of
crosslinking. In certain embodiments, the crosslinking agent or agents may be
present in
the fluids of the present invention in an amount in the range of from about
0.0005% to
about 10% weight by volume of the fluid. In certain embodiments, the
crosslinking agent
may be present in the fluids of the present invention in an amount in the
range of from
about 0.001% to about 5% weight by volume of the fluid. One of ordinary skill
in the art,
with the benefit of this disclosure, will recognize the appropriate amount of
crosslinking
agent to include in a fluid of the present invention based on, among other
things, the
temperature conditions of a particular application, the type of polymer(s)
used, the
molecular weight of the polymer(s), the desired degree of viscosification,
and/or the pH of
the fluid.
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Although any suitable method for forming the insulating fluids of the present
invention may be used, in some embodiments, an aqueous-based insulating fluid
of the
present invention may be formulated at ambient temperature and pressure
conditions by
mixing water and a chosen water-miscible organic liquid. The water and water-
miscible
organic liquid preferably may be mixed so that the water-miscible organic
liquid is miscible
in the water. The chosen silicate may then be added and mixed into the water
and water-
miscible organic liquid mixture until the silicate is hydrated. Any chosen
additives may be
added at any, including a polymer. Preferably, any additives are dispersed
within the
mixture. If desired, a crosslinking agent may be added. If used, it should be
dispersed in
the mixture. Crosslinking, however, generally should not take place until
thermal activation,
which preferably, in subterranean applications, occurs downhole; this may
alleviate any
pumping difficulties that might arise as a result of activation before
placement. Activation
results in the fluid forming a gel. The term "gel", as used herein, and its
derivatives refer to
a semi-solid, jelly-like state assumed by some colloidal dispersions. Once
activated, the
gel should stay in place and be durable with negligible syneresis.
In some embodiments, the gels formed by hydrating the silicate may have a
zero sheer viscosity of about 100,000 centipoise measured on an Anton Paar
Controlled
Stress Rheometer at standard conditions using standard operating procedure.
Once gelled, if the fluid contains polymer, one method of removing the gel may
comprise diluting or breaking the crosslinks and/or the polymer structure
within the gel
using an appropriate method and/or composition to allow recovery or removal of
the gel.
Another method could involve physical removal of the gel by, for example, air
or liquid.
In some embodiments, the aqueous-based insulating fluids of the present
invention may be prepared on-the-fly at a well-site or pipeline location. In
other
embodiments, the aqueous-based insulating fluids of the present invention may
be
prepared off-site and transported to the site of use. In transporting the
fluids, one should be
mindful of the activation temperature of the fluid.
In one embodiment, the present invention provides a method comprising:
providing a first tubing; providing a second tubing that substantially
surrounds the first
tubing thus creating an annulus between the first tubing and the second
tubing; providing
an aqueous-based insulating fluid that comprises an aqueous base fluid, a
polyol, and a
layered silicate; and placing the aqueous-based insulating fluid in the
annulus. In some
embodiments, the aqueous-based insulating fluid also includes a polymer. The
tubings
may have any shape appropriate for a chosen application. In some instances,
the second
tubing may not be the same length as the first tubing. In some instances, the
tubing may
comprise a portion of a larger apparatus. In some instances, the aqueous-based
insulating
CA 02716450 2012-07-13
fluid may be in contact with the entire first tubing from end to end, but in
other situations,
the aqueous-based insulating fluid may only be placed in a portion of the
annulus and thus
only contact a portion of the first tubing. In some instances, the first
tubing may be
production tubing located within a well bore. In some instances, the tubings
may be located
5 in a geothermal well bore. The production tubing may be located in an off-
shore location. In
other instances, the production tubing may be located in a cold climate. In
other instances,
the first tubing may be a pipeline capable of transporting a fluid from one
location to a
second location.
In one embodiment, the present invention provides a method comprising:
10 providing a first tubing; providing a second tubing that substantially
surrounds the first
tubing thus creating an annulus between the first tubing and the second
tubing; providing
an aqueous-based insulating fluid that comprises an aqueous base fluid, a
water-miscible
organic liquid, and a layered silicate; and placing the aqueous-based
insulating fluid in the
annulus. In some embodiments, the aqueous-based insulating fluid also includes
a
polymer.
In one embodiment, the present invention provides a method comprising:
providing a tubing containing a first fluid located within a well bore such
that an annulus is
formed between the tubing and a surface of the well bore; providing an aqueous-
based
insulating fluid that comprises an aqueous base fluid, a water-miscible
organic liquid, and a
layered silicate; and placing the aqueous-based insulating fluid in the
annulus. In some
embodiments, the aqueous-based insulating fluid also includes a polymer.
In one embodiment, the present invention provides a method comprising:
providing a first tubing that comprises at least a portion of a pipeline that
contains a first
fluid; providing a second tubing that substantially surrounds the first tubing
thus creating an
annulus between the first tubing and the second tubing; providing an aqueous-
based
insulating fluid that comprises an aqueous base fluid, a water-miscible
organic liquid, and a
layered silicate; and placing the aqueous-based insulating fluid in the
annulus. In some
embodiments, the aqueous-based insulating fluid also includes a polymer.
In one embodiment, the present invention provides an aqueous-based insulating
fluid that comprises an aqueous base fluid, a water-miscible organic liquid,
and a layered
silicate. In some embodiments, the aqueous-based insulating fluid also
includes a polymer.
In another embodiment, the present invention provides a method of forming an
aqueous-based insulating fluid comprising: mixing an aqueous base fluid and a
water-
miscible organic liquid to form a mixture; adding at least one layered
silicate to the mixture;
allowing the layered silicate to hydrate; placing the mixture comprising the
layered silicate
in a chosen location; allowing the mixture comprising the layered silicate to
activate to form
CA 02716450 2012-07-13
11
a gel therein. In some embodiments, a polymer may be added to the mixture and
allowed
to hydrate. Optionally, a crosslinking agent may be added to the mixture
comprising the
polymer to crosslink the polymer.
To facilitate a better understanding of the present invention, the following
examples of certain aspects of some embodiments are given. In no way should
the
following examples be read to limit, or define, the entire scope of the
invention.
EXAMPLES
Example 1
We studied the formulation and testing of various combinations of inorganic,
organic, clay and polymeric materials for use as viscosifying/gelling agents
in aqueous
based fluids for insulating fluids. We conducted a series of tests in which
the solubility,
thermal conductivity, thermal stability, pH, gelling properties, rheological
behavior, and
toxicity of the various fluids were evaluated and compared. Perhaps most
importantly, the
thermal stability ranges from 37 F to 280 F and above were evaluated. These
tests were
conducted over short and long term periods. Table A lists the materials used
in the
formulations and the amounts tested. This in no way should be construed as an
exhaustive example with reference to the invention or as a definition of the
invention in any
way.
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Table A
Base Fluids % by Vol
Fresh Water, (FW) 1 to 60
Monovalent Brines 1 to 60
Divalent Brines 1 to 60
Propylene Glycol, (PG) 40 to 99
Ethylene Glycol, (EG) 40 to 99
Glycerol 40 to 99
I
Polymers % Wt
Polyacrylamide (M.W. 5- 10 x 1 & g/mol), (PAM) 0.1 to 5
Polyacrylamide copolymer A (M.W. 510 x 16 g/mol) 0.1 to 5
Polyacrylamide copolymer B (MW 2.02.5 x 16 g/mol) 0.1 to 5
Polyaaylamideterpolymer C (MW 0.2-1c g/mol) 0.1 to 5
System I Crosslinkers System 2 Crosslinker % by Wt
(primary) PPm
Hydroquinone, (HQ) 500- 7000 Polyethylenimine (PEI) .0005 to 10 %
Phenol 500- 7000 Polyalkylimine .0005 to 10 %
Aspirin 500- 7000
Phenyl Acetate 500-1000
Amino- benzoic Acid, (ABA) 500- 7000
AnthranilicAcid 500- 7000
System 1 Crosslinkers
(secondary) ppm
Hexamethylenetetramine, 500- 7000
(HMTA)
Formaldehyde, (FM) 500- 7000
Trademark
Thermal stability and static aging: All formulations of fluids were statically
aged
at temperatures >_ about 280 F for two months. Formulations and properties for
the tested
fluids are shown in Tables 1 and 2 below. Most of the fluids appeared to
remain intact,
with the crosslinked systems showing an increase in viscosity and what
appeared to be
complete gelation behavior. We believe that these systems appeared to exhibit
more
desirable stability properties than other fluids, which included numerous
biopolymers (e.g.,
xanthan, welan, and diutan gums) and inorganic clays and were generally
destroyed after 3
days at 250 F. In addition, as to the thermal stability of these formulations
tested, less than
1 % syneresis was observed for any of the samples.
CA 02716450 2012-07-13
13
In addition to the static tests, Sample 4 was evaluated using a high-
temperature
viscometer to examine the thermal activation of crosslinking agents (Figure
1). The fluid
was subjected to a low shear rate at 190 F, with viscosity measurements
showing an
increase with time to reach the maximum recordable level around 5000 minutes.
Table 1. IPF Formulations and Properties Before Static Aging.
Formulations
Sample 1 2 3 4
Density, ppg 8.5 10.5 12.3 11.3
Water, % vol 20 10 --- 1
Glycerol, % vol --- 90 78.5 90
PG, % vol 80 --- --- ---
Brine, % vol --- --- 21.5 9
Polymer A, % wt 1 1 1 ---
Polymer B, % wt --- --- --- 1.25
Aldehyde, ppm 5000 5000 5000 ---
HQ, ppm 5000 5000 5000 ---
PEI, % wt --- --- --- 2
Properties
300 rpm' 280 285 270 82
Shear Strength, lb/100 ft2 13.4 20.65 20.65 >13.4
Thermal Conducitivty , BTU/hftF 0.141 0.172 0.154 0.158
1 Measurements obtained from reading observed on Fann 35 viscometer, sample
temperature 120 F.
2 Measurements obtained by KD2-Pro Thermal Properties Analyzer.
CA 02716450 2012-07-13
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Table 2. IPF Formulations and Properties After 60 Days Static Aging at 280 F.
Formulations
Sample 1 2 3 4
Density, ppg 8.5 10.5 12.3 11.3
Water, % vol 20 10 --- 1
Glycerol, % vol --- 90 78.5 90
PG, % vol 80 --- --- ---
Brine, % vol --- --- 21.5 9
Polymer A, % wt 1 1 1 ---
Polymer B, % wt --- --- --- 1.25
Aldehyde, ppm 5000 5000 5000 ---
HQ, ppm 5000 5000 5000 ---
PEI, % wt --- --- --- 2
Properties
300 rpm max max max max
Shear Strength, lb/100 ft2 >50 >50 >50 >50
Thermal Conducitivty , BTU/hftF 0.141 0.172 0.154 0.158
3 Fluids gelled, off-scale measurement.
Thermal conductivity measurements: The importance of a low thermal
conductivity (K) is an important aspect of the success of insulating fluids.
For effective
reduction of heat transfer, aqueous-based packer fluids in the density range
of 8.5 to 12.3
ppg are expected to exhibit values for K of 0.3 to 0.2 BTU/hr ft OF, and
preferably would
have lower values. From the various formulations listed above, using these
formulations
fluid densities of 8.5 to 14.4 ppg were observed, all of which have a thermal
conductivity of
< 0.2 BTU/hr ft OF as shown in Tables 1 and 2.
EXAMPLE 2
We studied the formulation and testing of various combinations of inorganic,
organic, clay and polymeric materials for use as viscosifying/gelling agents
in aqueous
based fluids for insulating fluids. We conducted a series of tests in which
the solubility,
thermal conductivity, thermal stability, pH, gelling properties, rheological
behavior, and
toxicity of the various fluids were evaluated and compared. Perhaps most
importantly, the
thermal stability ranges from 37 F to 500 F and above were evaluated. These
tests were
conducted over short and long term periods. Table B lists the materials used
in the
CA 02716450 2012-07-13
formulations and the amounts tested. This in no way should be construed as an
exhaustive example with reference to the invention or as a definition of the
invention in any
way.
Table B
Base Fluids % by Vol
Fresh Water, (FW) 1 to 60
Monovalent Brines 1 to 60
Divalent Brins 1 to 60
Propylene Glycol, (PG) 40 to 99
Ethylene Glycol, (EG) 40 to 99
Glyceral 40 to 99
5
Viscosifiers/Gellants % Wt
Synthetic Silicates 0.1 to 5
Thermal stability and static aging: All formulations of fluids were statically
aged
at temperatures >_ about 400 F for 3 day intervals. Formulations and
properties for the
10 tested fluids are shown in Tables 3 and 4 below. Most of the fluids
appeared to remain
intact, with the crosslinked systems showing an increase in viscosity and what
appeared to
be complete gelation behavior. We believe that these systems appeared to
exhibit more
desirable stability properties than other fluids, which included numerous
biopolymers (e.g.,
xanthan, welan, and diutan gums) and inorganic clays and were generally
destroyed after 3
15 days at 250 F. In addition, as to the thermal stability of these
formulations tested, less than
1 % syneresis was observed for any of the samples.
CA 02716450 2012-07-13
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Table 3. IPF Formulations and Properties Before Static Aging
Sample 1 2
Thermal conductivity, BTU/(hft F) 0.166 0.177
Density, lb/gal 10.5 9.5
Fann 35 Viscometer, 150 F 150 F
600 rpm 160 161
300 rpm 125 126
200 rpm 109 102
100 rpm 84 88
6 rpm 37 40
3 rpm 34 38
PV 35 35
YP 90 91
Table 4. IPF Formulations and Properties After 72 Hours Static Aging at 450 F.
Sample 1 2
Thermal conductivity, BTU/(hft F) 0.166 0.177
Density, lb/gal 10.5 9.5
Fann 35 Viscometer, 150 F 150 F
600 rpm 163 159
300 rpm 127 122
200 rpm 111 104
100 rpm 82 86
6 rpm 40 41
3 rpm 36 37
PV 36 35
YP 91 85
Thermal conductivity measurements: The importance of a low thermal
conductivity (K) is an important aspect of the success of insulating fluids.
For effective
reduction of heat transfer, aqueous-based packer fluids in the density range
of 8.5 to 10.5
CA 02716450 2012-07-13
17
ppg are expected to exhibit values for K of 0.3 to 0.2 BTU/hr ft OF, and
preferably would
have lower values. From the various formulations listed above, using these
formulations
fluid densities of 8.5 to 10.5 ppg were observed, all of which have a thermal
conductivity of
< 0.2 BTU/hr ft OF as shown in Tables 3 and 4.
Therefore, the present invention is well adapted to attain the ends and
advantages mentioned as well as those that are inherent therein. The
particular
embodiments disclosed above are illustrative only. Furthermore, no limitations
are
intended to the details of construction or design herein shown, other than as
described in
the claims below. Whenever a numerical range, R, with a lower limit, RL, and
an upper
limit, RU, is disclosed, any number falling within the range is specifically
disclosed. In
particular, the following numbers within the range are specifically disclosed:
R=RL+k* (RU-
RL), wherein k is a variable ranging from 1 percent to 100 percent with a 1
percent
increment, i.e., k is 1 percent, 2 percent, 3 percent, 4 percent, 5
percent,..., 50 percent, 51
percent, 52 percent,..., 95 percent, 96 percent, 97 percent, 98 percent, 99
percent, or 100
percent. Moreover, any numerical range defined by two R numbers as defined in
the
above is also specifically disclosed. Moreover, the indefinite articles "a" or
"an", as used in
the claims, are defined herein to mean one or more than one of the element
that it
introduces. Also, the terms in the claims have their plain, ordinary meaning
unless
otherwise explicitly and clearly defined by the patentee.
