U.S. patent application number 16/178965 was filed with the patent office on 2019-05-02 for heavy fluid and method of making it.
This patent application is currently assigned to Highland Fluid Technology, Ltd.. The applicant listed for this patent is Highland Fluid Technology, Ltd.. Invention is credited to Kevin Smith.
Application Number | 20190127623 16/178965 |
Document ID | / |
Family ID | 66245381 |
Filed Date | 2019-05-02 |
United States Patent
Application |
20190127623 |
Kind Code |
A1 |
Smith; Kevin |
May 2, 2019 |
Heavy Fluid and Method of Making It
Abstract
Heavy fluids are made from calcium bromide and at least one
hydrogen bond donor such as a low molecular weight polyol or an
organic acid. The combination of a hydrogen bond donor and calcium
bromide as a hydrogen bond acceptor in an appropriate molar ratio
forms a higher density clear completion fluid at a low temperature
not otherwise obtainable with heavy aqueous solutions of calcium
bromide such as are used in oilfield wells. A method of making the
fluid comprises mixing calcium bromide with the polyol(s) in the
presence of water and then reducing the water content, thus forming
a heavy fluid. A crystallization inhibitor such as
nitrilitriacetamide or a particulate silicate is included in the
formulation. When the heavy fluid "freezes," its physical form is
somewhat amorphous and pumpable rather than crystalline. The heavy
fluid is useful as a drilling fluid as well as a completion fluid
and for other purposes in oil recovery processes where extreme
density is beneficial.
Inventors: |
Smith; Kevin; (Bellaire,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Highland Fluid Technology, Ltd. |
Houston |
TX |
US |
|
|
Assignee: |
Highland Fluid Technology,
Ltd.
Houston
TX
|
Family ID: |
66245381 |
Appl. No.: |
16/178965 |
Filed: |
November 2, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62580813 |
Nov 2, 2017 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C09K 2208/22 20130101;
C09K 2208/32 20130101; C09K 8/12 20130101; C09K 8/845 20130101;
C09K 8/88 20130101; C09K 8/86 20130101; C09K 8/06 20130101 |
International
Class: |
C09K 8/06 20060101
C09K008/06; C09K 8/84 20060101 C09K008/84; C09K 8/86 20060101
C09K008/86 |
Claims
1. Method of making a clear, zinc-free heavy fluid comprising (a)
mixing (i) calcium bromide and 0% to 50% water by weight of the
total of calcium bromide and water with (ii) at least one hydrogen
donor in a mixture with up to 50% water by weight of the total of
said hydrogen donor and water, (b) adding a small amount of
crystallization inhibitor to the mixture of (a)(i) and (a)(ii), and
(c) removing water from said mixture to achieve a density of said
mixture of at least 16 pounds per gallon.
2. Method of claim 1 wherein said at least one hydrogen donor
comprises at least one polyol having from 2-6 carbon atoms and 2-6
hydroxyl groups or at least one organic acid.
3. Method of claim 1 wherein said calcium bromide in part (a)(i) is
a saturated solution of calcium bromide in said water.
4. Method of claim 1 wherein said calcium bromide in part (a)(i) is
solid calcium bromide.
5. Method of claim 1 wherein (1) step (a)(i) produces an aqueous
solution of calcium bromide having a density of 13.9 to 14.5 pounds
per gallon, (2) the mixture of part (a)(ii) comprises water and
9-11 percent of a polyol selected from ethylene glycol, propylene
glycol, glycerin and mixtures thereof based on the weight of the
CaBr.sub.2 solution, and (3) wherein, in step (c), 18-22 percent
water, based on the weight of the whole solution, is removed.
6. Method of claim 5 wherein the calcium bromide solution in
produced in step (a)(i) has a density of 14.1 to 14.3 pounds per
gallon.
7. Method of claim 5 wherein the mixture of part (a)(ii) comprises
9.8 to 10.2 percent ethylene glycol.
8. Method of claim 5 wherein, in step (c), 19.5 to 20.5 percent of
the solution is removed as water.
9. Method of claim 5 wherein, in step (c), said water is removed by
evaporation.
10. Method of making a phase controlled heavy fluid comprising (a)
mixing at least one low molecular weight polyol with calcium
bromide in the presence of water or dilute brine, and (b) reducing
the water concentration in the mixture of step (a) to obtain a
fluid having (i) a crystallization point lower than a fluid of the
same proportions of the same ingredients made by mixing without
removing water, and (ii) a density of at least 15 pounds per
gallon.
11. Method of claim 10 wherein said crystallization point is lower
than 40.degree. F.
12. Method of claim 10 wherein said low molecular weight polyol
comprises ethylene glycol.
13. Method of claim 10 wherein, step (a) comprises mixing said low
molecular weight polyol with an aqueous solution of calcium
bromide.
14. Method of claim 10 wherein step (a) comprises mixing in at
least some of said calcium bromide as a dry salt.
15. A clear fluid having a density of at least 15 pounds per
gallon, said fluid comprising ethylene glycol, calcium bromide, a
small amount of crystallization inhibitor, and water, said fluid
having a crystallization temperature lower than a fluid of the same
composition and proportions made without reducing its water
content.
16. The clear fluid of claim 15 wherein said crystallization
inhibitor comprises nitrilotriacetamide.
17. The clear fluid of claim 15 including at least one additive
selected from viscosity enhancing agents, corrosion inhibitors,
antibacterial agents, viscosity adjusters, and hydrate
inhibitors.
18. The clear fluid of claim 15 including at least one low
molecular weight polyol of the formula
OHCH.sub.2C(OH).sub.2CH.sub.2X, where X is H or OH in a ratio of 1
said low molecular weight polyol:3-9 ethylene glycol.
19. Method of drilling a wellbore with a drill bit comprising
circulating a fluid of claim 15 around said drill bit to remove
drill cuttings.
20. Method of completing a well comprising circulating a clear
fluid of claim 15 through said well.
Description
RELATED APPLICATION
[0001] This application claims the full benefit of Provisional
Application 62/580,813 filed Nov. 2, 2017.
TECHNICAL FIELD
[0002] Heavy fluids are made from calcium bromide and at least one
low molecular weight polyol which acts as a hydrogen bond donor.
The combination of a hydrogen bond donor and calcium bromide as a
hydrogen bond acceptor in an appropriate molar ratio forms a higher
density clear completion fluid at a low temperature not otherwise
obtainable with heavy aqueous solutions of calcium bromide such as
are used in oilfield wells. A method of making the fluid comprises
mixing calcium bromide with the polyol(s) in the presence of water
and then reducing the water content, thus forming a heavy fluid.
When the heavy fluid "freezes," its physical form is somewhat
amorphous and pumpable rather than crystalline. The heavy fluid is
useful as a drilling fluid as well as a completion fluid and for
other purposes in oil recovery processes.
BACKGROUND OF THE INVENTION
[0003] It is desirable for a clear completion fluid used in oil
well processing to have a high density in order to impose a high
hydrostatic pressure on the well and counteract formation pressure.
Aqueous calcium bromide solutions are commonly used because of
their weight, but simply increasing the concentration of CaBr.sub.2
to obtain more weight elevates the crystallization point--the
temperature at which a solid is formed, rendering the material
unpumpable, thus frustrating the fluid's usefulness.
[0004] Zinc bromide can be mixed with calcium bromide to yield
higher density, but zinc bromide is a marine pollutant and highly
corrosive. Fluids containing zinc bromide are highly corrosive both
to skin and to metal. There is a compelling need to replace zinc
bromide both for HSE (health, safety and environmental) reasons and
to mitigate downhole corrosion. By comparison, calcium bromide that
does not contain zinc bromide has a good HSE profile and low
corrosion rates. But the fluid must have the properties needed for
the work to be done.
[0005] In offshore wells, particularly in deep water, a completion
fluid is likely to be exposed to temperatures in the range of
30.degree. to 40.degree. F. for extended periods of time at the mud
line; thus a True Crystallization Temperature (TCT) in the
completion fluid higher than 30 degrees F. is not useful in that
situation. Also, pressure can increase the TCT, compounding the
need for a fluid with a low built-in TCT.
[0006] In the past, well engineers have focused on the weight
concentration of calcium bromide in water when designing a
completion fluid. That is, for example, a 54.2% by weight
CaBr.sub.2 solution in water has a TCT of -1.degree. F. but weighs
only 14.2 pounds per gallon. Increasing the concentration of
CaBr.sub.2 to make a 14.6 ppg solution elevates the TCT to
30.degree. F., and increasing the weight (density) further by
simply adding more CaBr.sub.2 to obtain a 15.3 ppg solution will
elevate the TCT to 68.degree. F., which is useless in many wells,
especially deep offshore wells. Elevated concentrations of calcium
bromide in aqueous solution are not the answer. A desirable
practical goal is a density in the range of 15.0-15.5 pounds per
gallon, as it could still be handled (with appropriate precautions)
and its performance is greatly enhanced by the increased density,
if its TCT can be controlled.
[0007] There is a need for a clear completion fluid which is very
dense, free of zinc bromide, and also has a low crystallization
temperature or is still pumpable when crystals form in the
fluid.
[0008] As further background for the description of the invention
to follow, it is of interest to remember that while pure ethylene
glycol will "freeze" at about 11 or 12 degrees Fahrenheit, a
60%/40% by weight mixture of ethylene glycol and water freezes at
about -49.degree. F.; the 60/40 mixture achieves the lowest freeze
point of all ratios of the two materials. Similarly, as the ratio
of glycerol to water is increased from 0/100% to 100%/0, the freeze
point follows a curve from 0.degree. C. to about -46.degree. C., at
a ratio of about 66% glycerol to 34% water by weight, then
increases on a substantially straight line as the ratio of glycerol
to water is increased, to the undiluted glycerol freeze point of
about 17.6.degree. C.
SUMMARY OF THE INVENTION
[0009] My invention includes a fluid having two basic components:
calcium bromide and a hydrogen donor such as an organic acid or a
low molecular weight polyol. While I do not intend to be bound by
any theories, I believe that, because of the way the composition is
made, a portion of each ingredient is combined with some of the
other to form a composition including a nonsymmetric ion which is
not present in a simple mixture or solution. The formation of the
nonsymmetric ion takes place by hydrogen bonding--that is, the
polyol acts as a hydrogen bond donor and the calcium bromide is a
hydrogen bond acceptor. In order to achieve this, water must be
removed after the mixture is made. Where substantially all the free
water is removed from the mixture, any water remaining appears to
be bound to the calcium bromide. The invention includes a method of
making the fluid, and the use of the fluid as a drilling fluid or
as a clear completion fluid in hydrocarbon recovery.
[0010] The novel fluid includes, in addition, a small amount of
nitrilotriacetamide ("NTA"), which acts as a crystallization
inhibitor; it is added at a specified point in the fluid's
preparation, which is explained further below. Alternative
crystallization inhibitors such as functionalized or other fine
particle silica, may be added after the hydrogen bonding is
accomplished. The new dense fluid may also be used as a drilling
fluid. The likely formation of the nonsymmetric ion may be part of
the novel method.
[0011] I am able to incorporate a high percentage of calcium
bromide in my fluid by eliminating or minimizing the use of water
as a solvent or carrier (although some may be added later for other
reasons) as a vehicle for introducing the CaBr.sub.2 to the
composition. In one method of making my heavy fluid, water may be
used first to dissolve the calcium bromide so that it can be
intimately mixed with the hydrogen donor. A readily understood
example, and a quite useful and practical one, is the combination
of CaBr.sub.2 and ethylene glycol (EG), OHCH.sub.2CH.sub.2OH. After
the CaBr.sub.2 is dissolved in water, the ethylene glycol is mixed
with the solution in a molar ratio of CaBr.sub.2 to EG of 1:1. A
small amount (typically 0.5% to 2.0%, based on the total non-water
ingredients) of NTA is added in aqueous solution. Water is then
removed in any suitable manner, such as evaporation, leaving a
fluid having a density of about 16 pounds per gallon and a modified
freeze point of about 40.degree. F. The fluid appears to include a
nonsymmetric ion made by hydrogen acting as a hydrogen bond from
the hydroxyl groups of the ethylene glycol.
[0012] Evaporation, as a practical matter, requires the
introduction of heat, but I may generate a portion of the heat by
dissolving dry calcium bromide into a mixture of water and at least
one polyol. Dissolution of calcium bromide in water is notably
exothermic. Thus, in this mode of preparation, a calcium bromide
solution need not be made as an initial step. As a further
essential step of my process, after dry CaBr.sub.2 is dissolved in
the mixture of water and polyol, a desired amount of water is
removed to increase the density of the mixture to at least 16
pounds per gallon, preferably at least 15 pounds per gallon.
[0013] The term "deep eutectic solvent" is used in an article by
Emma L. Smith, Andrew P. Abbott, and Karl S. Ryder titled Deep
Eutectic Solvents (DESs) and their Applications. See FIG. 2, a
"schematic representation of a eutectic point on a two component
phase diagram." The authors note that "(t)he difference in the
freezing point at the eutectic composition of a binary mixture of
A+B compared to that of a theoretical ideal mixture" is "related to
the magnitude of the interaction between A and B." The schematic
shows a significant (deep) trough below a line drawn between the
melting points of the two components. The authors also say (p.
11060-11061) that deep eutectic solvents "contain large
nonsymmetric ions that have low lattice energy and hence low
melting points. The charge delocalization occurring through
hydrogen bonding between for example a halide ion and the
hydrogen-donor moiety is responsible for the decrease in the
melting point of the mixture relative to the melting points of the
individual components."
[0014] The deep eutectic solvents are said to be analogous to ionic
liquids and are grouped into four classes in the above article and
elsewhere in the literature. Previous work with deep eutectic
solvents does not, however, include the development of heavy fluids
useful in oilfield applications. Nor does it include the
development of heavy fluids containing such nonsymmetric ions in a
significantly water-reduced or water-deprived state. Nor does it
include my method of creating heavy fluids that are pumpable even
after reaching a low crystallization temperature. While I believe
nonsymmetric ions are present in all of my compositions, it will be
observed that they do not necessarily meet the definition of a
eutectic, in that the crystallization point of the finished
composition may be well above the crystallization point of the
hydrogen donor.
[0015] My chief objective is to obtain a heavy fluid, free of zinc,
having a crystallization point well below that of previously known
solutions of the heavy salts used to make heavy brines and other
heavy fluids used in oil well processing.
[0016] My preferred polyol is ethylene glycol. Instead of, or
together with ethylene glycol, propylene glycol or glycerol can be
used as the hydrogen donor. In the case of glycerol, the molar
ratios are adjusted accordingly. That is, since glycerol
HOCH.sub.2CHOHCH.sub.2OH has three (hydrogen donor) hydroxyl
groups, the ideal molar ratio of CaBr.sub.2 to glycerol would be
3:2. In practice, the ratio may be varied from 5:2 to 2:5. A
mixture of at least two polyols selected from ethylene glycol,
propylene glycol and glycerin, each of said polyols comprising at
least 10% by weight of the mixture, can be used also, the
particular ratios dependent on the desired viscosity, density, cost
or other properties.
[0017] Particular mixtures of polyols may also be chosen to take
advantage of the deep eutectic freezing points such mixtures
exhibit. The polyol mixtures continue to act as hydrogen donors in
the presence of calcium bromide; thus, my invention includes the
use of mixtures of ethylene glycol, propylene glycol (1,2 propane
diol; PG), and glycerol (GLRL) in combination of any two of them or
all three wherein each is present in an amount of at least 10% by
weight. Examples of such ratios are listed in List A. The invention
is most efficient in hydrogen bonding to form the above-described
nonsymmetric ions when care is taken to observe the molar
equivalence of hydroxyl groups to bromide moieties in the
composition.
TABLE-US-00001 List A: Useful Hydrogen Donor (Polyol) Mixtures (by
weight) 1. 1 GLRL:9 EG 2. 1 GLRL:4 EG 3. 1 PG:9 EG 4. 1 PG:4 EG 5.
1 GLRL:3 EG 6. 1 PG:3 EG
[0018] Since glycerol and propylene glycol both contain three
carbon atoms, the general formula OHCH.sub.2C(OH).sub.2CH.sub.2X,
where X is H or OH, may be useful to describe the hydrogen donor
combinations recited in List A. Thus the ranges of list A may be
summarized:
1OHCH.sub.2C(OH).sub.2CH.sub.2X, where X is H or OH:3-9EG
[0019] Likewise, combinations of ethylene glycol (EG) and low
molecular weight polyethylene glycol (having 4-8 carbon atoms and 3
to 8 hydroxyl groups--PEG) in mixtures of EG containing 1% to 25%
PEG may be useful where a somewhat higher viscosity is desired. As
with the combinations of EG and PG or GLRL mentioned above, the
bromide should be in a range of near equivalence to the hydroxyl
moieties, e.g. is a range of 2:5 to 5:2 or preferably 3:4 to
4:5.
[0020] Other useful examples of hydrogen donors in addition to the
low molecular weight polyols mentioned above include sorbitol,
urea, citric acid, tartaric acid, and choline chloride. Where an
increase in viscosity is not one of the desiderata, I prefer to use
such relatively low molecular weight materials; they tend to be
more common, available, easier to work with and easier to maintain
the optimum molecular weight ratios; also many of them are known to
be acceptable in oilfield processing. Where an increase in
viscosity is desired as an additional benefit, higher molecular
weight polyols and other polymeric materials having many hydrogen
donor sites may be used, taking care to match the hydrogen donor
sites to the acceptor sites on the CaBr.sub.2 and also realizing
that the application in mind may have an upper limit for viscosity.
The practitioner should be aware that the increasing molecular
weight of longer chain polyols will increase viscosity
exponentially in aqueous solution; in the present context, where it
is desired to have little or no water, the practical limit in
molecular weight for candidate polyols is rather low. Nevertheless,
as indicated above, I do not intend to rule out the use of polyols
having four or more hydroxyl groups. Sorbitol is mentioned
specifically below.
[0021] In choosing hydrogen donors, one should also be aware of
their physical state at ambient temperatures--for example, citric
acid is crystalline at room temperature; if both the CaBr.sub.2 and
the citric acid are in the form of separate aqueous solutions added
together, more water must be removed than might otherwise be the
case. Even with this example, however, the reduced-temperature
crystallinity phenomenon is observable.
[0022] As indicated above, my invention includes the method of
making a phase controlled clear heavy fluid comprising mixing a
heavy hydrogen acceptor compound with a hydrogen donor compound in
the presence of water and removing water in any effective manner to
create at least some large nonsymmetric ions; evaporation is
effective to remove the water and cause the formation of the
nonsymmetric ions. The hydrogen donor compound is preferably a low
molecular weight polyol. By a low molecular weight polyol, I mean
ethylene glycol (EG), propylene glycol (PG), and glycerol
(GLRL).
[0023] I also include a small amount of a crystallization inhibitor
in my dense fluids. They are of two types--solid and dissolved. The
dissolved inhibitor is preferably nitrilotriacetamide (NTA) in
water. The small amount, 0.5% to 2.0% NTA, is added to the mixture
before water is removed. The solid, amorphous or functionalized
silica, which may be in nano size (x to y % by weight of the
non-water components), may be added before or after the water is
removed. By inhibiting crystal formation at lower temperatures,
these materials greatly enhance the ability to pump the dense fluid
when otherwise exposure to low temperatures would noticeably
increase the risk that pumpability would be impossible.
[0024] The invention is further described below.
DETAILED DESCRIPTION OF THE INVENTION
[0025] Several different general methods of making my low-freezing
heavy fluid will be described below. This degree of stability
appears to be due to the formation of a nonsymmetrical ion by the
action of the hydrogen bond donor on the hydrogen bond
acceptor.
Procedure 1
[0026] As indicated above, CaBr.sub.2 and ethylene glycol may be
used to make my new fluid. In order to achieve a good mix with the
hydrogen donor (EG), calcium bromide is first dissolved in water,
then ethylene glycol is mixed with the solution in a molar ratio of
CaBr.sub.2 to EG of 1:1. To minimize heat expenditure in the
evaporation step, the calcium bromide solution is beneficially a
saturated solution. Deviation from the 1:1 ratio, say within the
range 2:5 to 5:2, may be effective as a practical matter. Water is
then removed in any suitable manner, such as evaporation, to
achieve a fluid having a density of 16.5 pounds per gallon. The
fluid will have a crystallization point of about 40.degree. F.,
which contrasts with the crystallization point higher than ambient
temperature which one would expect for an aqueous solution of 16.5
CaBr.sub.2.
[0027] Since it is a part of my method to remove water from the
mixture, I prefer to avoid using excess water with the CaBr.sub.2.
A saturated or near saturated solution is preferred, but excess
water will not prevent the accomplishment of the goal, which is to
obtain a clear liquid including as little water as possible and
that includes a significant quantity of nonsymmetric ions; these
ions survive the evaporation of the water of solvation of the
CaBr.sub.2. Moreover, they appear to survive the re-introduction of
water to the fluid. If, for example, the above attained fluid
having a density of 16.0 or 16.5 ppg is considered too dense for
the particular use at hand, it is notable that the addition of a
small amount of water (or other solvent) to reduce density does not
seem to affect the nonsymmetric ion relationship.
[0028] Evaporation of the water may be accomplished by heating the
mixture. Any way of heating may be used. Mixing may continue during
heating and evaporating.
Procedure 2
[0029] A method of preparation similar to Example 1 substitutes
glycerol for ethylene glycol and incorporates calcium bromide in a
molar ratio of 3 CaBr.sub.2 to 2 glycerol. Evaporating the water
originally in the calcium bromide brine will result in a slightly
heavier material than was obtained using ethylene glycol.
[0030] The calcium bromide used to make the CaBr.sub.2 solution for
mixing with the polyol hydrogen bond donor may initially be either
in the hydrated or anhydride form. There are several different
calcium bromide hydrates mentioned in the literature. The authors
of the above-mentioned paper on deep eutectic solvents say that the
solid metal halide hydrates have lower melting points than the
corresponding anhydride salts. After removal of the water in my
method, however, the calcium bromide molecular structure, or at
least some of it, is altered by the formation of nonsymmetric ions
including both bromide and hydrogen components, and, although the
entire mixture may be substantially "anhydrous," the conventional
understanding of an anhydrous molecular structure is not
applicable--a nonsymmetric ion exists in a substantially water-free
or reduced water system. Particularly when solidification occurs at
lower temperatures, true crystals are not formed; the material is
"soft" or amorphous and actually pumpable at the solidification
temperature and below.
Procedure 3
[0031] To enhance the pumpability of the "frozen" eutectic
material, I may add a small amount of a crystallization inhibitor
such as nitrilotriacetamide (0.5-2.0% based on the non-water
components), amorphous silica, functionalized silica, or any other
acceptable crystallization inhibitor. To assure even distribution
of the crystallization inhibitor, it can be present at the
beginning of the process so that it can be thoroughly mixed into
the mixture before water removal is begun. The silica may be added
at any time in the process of preparation of the deep eutectic
fluid.
Procedure 4
[0032] An especially useful and practical approach is to (a)
prepare an aqueous solution of calcium bromide having a density of
14.2 pounds per gallon (b) add 10 percent, based on the weight of
the CaBr.sub.2 solution, propylene glycol (ethylene glycol,
glycerol, or mixtures of the three polyols may be substituted), and
then (c) remove twenty percent, based on the weight of the whole
solution, water, concentrating the solution by removing 20% of it
in the form of water will result in a clear fluid having a density
of 15.2 pounds per gallon, which is a highly desirable density for
many oilfield uses. Its low crystallization temperature has been
unattainable in the past for a fluid of such a density. The clear,
solids-free fluid composition may be used as a completion fluid,
drilling fluid, or for gravel packing.
[0033] For use in the oilfield, it may be convenient to use an
already-prepared solution of calcium bromide such as, for example,
a 14.2 pound per gallon solution prepared off site. At the site of
use, this solution can be mixed with the hydrogen bond donor, such
as one or more of the low molecular weight polyols mentioned above.
Water is then removed from the mixture to make the heavier
composition of the invention. Useful examples of combinations of
polyols include mixtures of EG with 10-15% PG or GLRL.
[0034] As my heavy fluids are contemplated for use in various
oilfield and gas production applications, a notable advantage is
that wherever water is mentioned throughout this description of the
invention as a medium for dissolving calcium bromide or otherwise
in the preparation of the heavy fluid, dilute brine may be used as
a substitute for plain water. Dilute brine is commonly available in
the oilfield and may present a problem for disposal which can be
alleviated by use in the present invention.
Procedure 5
[0035] This procedure and Procedure 6 utilize the fact that the
dissolution of calcium bromide in water generates heat. In this
Procedure 5, which may be particularly useful in the field, a
previously prepared 14.2 pound per gallon solution of calcium
bromide is mixed with the polyol and then more calcium bromide is
added in the form of a dry salt, preferably to achieve a molar
ratio described above for the final composition. The dissolution of
the calcium bromide will generate some heat and thereby elevate the
temperature of the mixture, but will not be enough to evaporate any
water. Additional heat will be required to evaporate the required
amount of water, create the asymmetric ions described above, and
achieve a deep eutectic heavy fluid.
Procedure 6
[0036] Yet another way is to mix the three components at the same
time--water, polyol, and CaBr.sub.2. This will be even more
exothermic than the approach of Procedure 5, but will still require
the addition of heat to achieve the desired degree of water
evaporation.
[0037] It should be understood that the crystallization inhibitors
NTA and silica are beneficially used in any of the above procedures
as explained generally above.
[0038] In addition to use as clear completion and drilling fluids,
my heavy fluids may be useful in other oilfield applications such
as pipeline cleanouts, coiled tubing cleanouts, to help release
stuck drill pipe, and to remove refinery deposits. The unique
combination of attributes of my compositions--high density, free of
zinc, clear, and pumpability at very low temperatures point to
their high versatility. As to density, persons skilled in the art
of hydrocarbon recovery will recognize that the heavy fluids may be
favored candidates for any application where barite has been used
in the past. The heavy fluid compositions may include at least one
additive selected from viscosity enhancing agents, corrosion
inhibitors, antibacterial agents, viscosity adjusters, and hydrate
inhibitors.
* * * * *