IMPROVED AQUEOUS-BASED INSULATING FLUIDS
AND RELATED METHODS
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation in part of U.S. Patent Application
Number 11/685,909 entitled "Improved Aqueous-Based Insulating Fluids and Related
Methods," filed on March 14, 2007, the entirety of which is herein incorporated by reference,
and from which priority is claimed pursuant to 35 U.S.C. § 120.
BACKGROUND
[0002] 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).
[0003] 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.
[0004] 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.
[0005] 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.
[0006] 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 240oF for relatively short periods of
time. This can be problematic because it can result in premature degradation of the fluid,
which can 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.
[0007] 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.
[0008] 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
[0009] 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).
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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.
[0015] The features and advantages of the present invention will be readily
apparent to those skilled in the art. While numerous changes may be made by those skilled in
the art, such changes are within the spirit of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] 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.
[0017] Figure 1 lists the materials used in the formulations and the amounts
thereof as described in Example 1 in the Examples section.
[0018] Figure 2 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.
[0019] Figure 3 lists the materials that may be used in the formulations and
the approximate amounts thereof as described in Example 2 in the Examples section.
[0020] Figure 4 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
[0021] 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.
[0022] 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.
[0023] 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 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.
[0024] 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, KCl, 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.
[0025] 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 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 sure 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.
[0026] 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.
[0027] 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 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%.
[0028] 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 "LAPONITETM 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.
[0029] 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-methyl-
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 about 15% weight by
volume of the fluid, and more preferably, from about 0.5% to about 4%.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] 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.
[0036] 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.
[0037] 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.
[0038] 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 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 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.
[0039] 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 armulus 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.
[0040] 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
armulus 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.
[0041] 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.
[0042] 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.
[0043] 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 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.
[0044] 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
[[[Ryan - Conflrm that these examples were performed exactly as written below.]]]
Example 1
[0045] 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. Figure 1 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.
[0046] 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.
[0047] In addition to the static tests, Sample 4 was evaluated using a high-
temperature viscometer to examine the thermal activation of crosslinking agents (Figure 2).
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.
1 Measurements obtained from reading observed on Fann 35 viscometer, sample temperature 120°F.
2 Measurements obtained by KD2-Pro Thermal Properties Analyzer.
Table 2. IPF Formulations and Properties After 60 Days Static Aging at 280°F.
3 Fluids gelled, off-scale measurement.
[0048] 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 °F, 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 °F as shown in Tables 1 and 2.
EXAMPLE 2
[0049] 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. Figure 3 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.
[0050] 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 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 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.
Table 3. IPF Formulations and Properties Before Static Aging
Table 4. IPF Formulations and Properties After 72 Hours Static Aging at 450°F.
[0051] 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 ppg
are expected to exhibit values for K of 0.3 to 0.2 BTU/hr ft °F, 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 °F as shown in Tables 3 and 4.
[0052] 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, as the present invention may be modified and practiced
in different but equivalent manners apparent to those skilled in the art having the benefit of
the teachings herein. Furthermore, no limitations are intended to the details of construction or
design herein shown, other than as described in the claims below. It is therefore evident that
the particular illustrative embodiments disclosed above may be altered or modified and all
such variations are considered within the scope and spirit of the present invention. All
numbers and ranges disclosed above may vary by any amount (e.g., 1 percent, 2 percent, 5
percent, or, sometimes, 10 to 20 percent). 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.
What is claimed is:
1. 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.
2. The method of claim 1 wherein the aqueous-based insulating fluid further
comprises a polymer.
3. The method of claim 1 wherein the aqueous-based insulating fluid further
comprises at least one additive selected from the group consisting of: a corrosion inhibitor, a
pH modifier, a biocide, a glass bead, a hollow sphere, a hollow microsphere, a rheology
modifier, a buffer, a hydrate inhibitor, a breaker, a tracer, an additional weighting agent, a
viscosifier, and a surfactant.
4. The method of claim 1 wherein the aqueous base fluid comprises at least one
brine selected from the group consisting of: NaCl, NaBr, KCl, CaCl2, CaBr2, ZrBr2, sodium
carbonate, sodium formate, potassium formate, and cesium formate, and a derivative thereof
5. The method of claim 1 wherein the water-miscible organic liquid comprises at
least one liquid selected from the group consisting of: an ester, an amine, an alcohol, a
polyol, a glycol ether, and a derivative thereof.
6. The method of claim 5 wherein the polyol comprises at least one polyol
selected from the group consisting of: a water-soluble diol; ethylene glycol; propylene
glycol; polyethylene glycol; polypropylene glycol; diethylene glycol; triethylene glycol;
dipropylene glycol; tripropylene glycol; a reaction product formed by reacting ethylene and
propylene oxide with an active hydrogen base compound; a reaction product formed by
reacting polyethylene glycol and polypropylene glycol with an active hydrogen base
compound; neopentyl glycol; a pentanediol; a butanediol; an unsaturated diol; a butyne diol;
a butene diol; a triol; glycerol; an ethylene adduct, a propylene oxide adduct; pentaerythritol;
a sugar alcohol; and a derivative thereof
7. The method of claim 1 wherein the layered silicate comprises at least one
layered silicate selected from the group consisting of smectite, vermiculite, swellable
fluoromica, montmorillonite, beidellite, hectorite, and saponite.
8. The method of claim 7 wherein the layered silicate is a synthetic layered
silicate.
9. The method of claim 7 wherein the layered silicate is present in the fluid in an
amount in the range of from about 0.1% to about 15% by weight of the fluid.
10. The method of claim 7 wherein the water-miscible organic liquid is present in
the fluid in an amount in the range of from about 40% to about 99% by weight of the fluid.
11. A method comprising:
providing an apparatus comprising a tubing that comprises 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.
12. The method of claim 11 wherein the aqueous-based insulating fluid further
comprises a polymer.
13. The method of claim 11 wherein the aqueous base fluid comprises at least one
brine selected from the group consisting of: NaCl, NaBr, KCl, CaCl2, CaBr2, ZrBr2, sodium
carbonate, sodium formate, potassium formate, cesium formate, and a derivative thereof.
14. The method of claim 11 wherein the water-miscible organic liquid comprises
at least one liquid selected from the group consisting of: an ester, an amine, an alcohol, a
polyol, a glycol ether, and a derivative thereof.
15. The method of claim 14 wherein the polyol comprises at least one polyol
selected from the group consisting of: a water-soluble diol; ethylene glycol; propylene
glycol; polyethylene glycol; polypropylene glycol; diethylene glycol; triethylene glycol;
dipropylene glycol; tripropylene glycols a reaction product formed by reacting ethylene and
propylene oxide with an active hydrogen base compound, a reaction product formed by
reacting polyethylene glycol and polypropylene glycol with an active hydrogen base
compound; neopentyl glycol; a pentanediol; a butanediol; an unsaturated diol; a butyne diol;
a butene diol; a triol; glycerol; an ethylene oxide adduct, a propylene oxide adduct;
pentaerythritol; a sugar alcohol; and any derivative thereof
16. The method of claim 11 wherein the layered silicate comprises at least one
layered silicate selected from the group consisting of: smectite, vermiculite, swellable
fluoromica, montmorillonite, beidellite, hectorite, and saponite.
17. The method of claim 12 wherein the layered silicate is a synthetic layered
silicate.
18. 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,
19. The method of claim 18 wherein the aqueous-based insulating fluid further
comprises a polymer.
20. The method of claim 18 wherein the layered silicate comprises at least one
layered silicate selected from the group consisting of: smectite, vermiculite, swellable
fluoromica, montmorillonite, beidellite, hectorite, and saponite.
21. The method of claim 18 wherein the water-miscible organic liquid comprises
at least one liquid selected from the group consisting of: an ester, an amine, an alcohol, a
polyol, a glycol ether, and a derivative thereof
22. The method of claim 21 wherein the polyol comprises at least one polyol
selected from the group consisting of: a water-soluble diol; ethylene glycol; propylene
glycol; polyethylene glycol; polypropylene glycol; diethylene glycol; triethylene glycol;
dipropylene glycol; tripropylene glycol; a reaction product formed by reacting ethylene and
propylene oxide with an active hydrogen base compound; a reaction product formed by
reacting polyethylene glycol and polypropylene glycol with an active hydrogen base
compound; neopentyl glycol; a pentanediol; a butanediol; an unsaturated diol; a butyne diol;
a butene diol; a triol; a glycerol; an ethylene oxide adduct; a propylene oxide adduct;
pentaerythritol; a sugar alcohol; and a derivative thereof
23. The method of claim 18 wherein the layered silicate is present in the fluid in
an amount in the range of from about 0.1% to about 15% by weight of the fluid and the
water-miscible organic liquid is present in the fluid in an amount in the range of from about
40% to about 99% by weight of the fluid.
24. An aqueous-based insulating fluid comprising:
an aqueous base fluid,
a water-miscible organic liquid, and
a layered silicate.

Provided herein are methods and compositions that include 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. A composition provided
includes an aqueous-based insulating fluid comprising an aqueous base fluid, a water-miscible organic liquid, and a layered silicate.