U.S. patent application number 12/868501 was filed with the patent office on 2010-12-23 for cement additive for the enhanced treatment of oil and gas wells and related methods of use.
Invention is credited to Lloyd Byron Spangle.
Application Number | 20100319918 12/868501 |
Document ID | / |
Family ID | 40340605 |
Filed Date | 2010-12-23 |
United States Patent
Application |
20100319918 |
Kind Code |
A1 |
Spangle; Lloyd Byron |
December 23, 2010 |
CEMENT ADDITIVE FOR THE ENHANCED TREATMENT OF OIL AND GAS WELLS AND
RELATED METHODS OF USE
Abstract
Cement mixtures and methods are disclosed for enhancing fluid
loss prevention in oil and gas wells comprising an electrolyte, a
polymer and a cross linking agent.
Inventors: |
Spangle; Lloyd Byron;
(Claremore, OK) |
Correspondence
Address: |
Novak Druce + Quigg LLP
1000 Louisiana Street, Fifty-Third Floor
Houston
TX
77002
US
|
Family ID: |
40340605 |
Appl. No.: |
12/868501 |
Filed: |
August 25, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12704333 |
Feb 11, 2010 |
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12868501 |
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12019933 |
Jan 25, 2008 |
7670994 |
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12704333 |
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Current U.S.
Class: |
166/285 ;
166/192; 521/25; 523/130 |
Current CPC
Class: |
C04B 28/02 20130101;
C04B 28/02 20130101; C09K 8/487 20130101; C04B 22/0013 20130101;
C09K 8/512 20130101; C04B 2103/46 20130101; C04B 24/2623 20130101;
C04B 2103/0062 20130101 |
Class at
Publication: |
166/285 ; 521/25;
523/130; 166/192 |
International
Class: |
E21B 33/00 20060101
E21B033/00; C09K 8/44 20060101 C09K008/44; E21B 33/12 20060101
E21B033/12 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 22, 2008 |
US |
PCT/US08/80838 |
Claims
1. A method for inhibiting fluid loss from an oil and gas well,
said method comprising the steps of: adding an electrolyte into a
cement mixture comprising a cross linking agent and a polymer, and
pumping said cement mixture into said well's borehole to cement at
least a portion of a formation face, said cement mixture comprising
a polymer composition, wherein polymerization of said polymer is
inhibited, thereby inhibiting fluid loss from said well's borehole
to said formation.
2. A fluid loss additive for use in a cement mixture to complete a
well bore, said fluid loss additive comprising an electrolyte, a
polymer and a cross linking agent.
3. The fluid loss additive of claim 2 comprising about 1%
electrolyte to about 99% electrolyte, about 1% polymer to about 99%
polymer, and about 0.1% cross linking agent to about 5% cross
linking agent.
4. The fluid loss additive of claim 3, further comprising at least
one of a retarder, a defoamer, and a polyanionic polymer.
5. A kit for inhibiting fluid loss from an oil and gas well
comprising about 1% electrolyte to about 99% electrolyte, about 1%
polymer to about 99% polymer, and about 0.1% cross linking agent to
about 5% cross linking agent.
6. A wellbore treated to inhibit fluid loss with the composition of
claim 2.
7. A pumpable cement mixture comprising about 0.01% to about 5.0%
electrolyte, about 0.01% to about 5.0% polymer, about 0.001 to
about 0.1% cross linking agent, about 5% to about 50% water, and
about 30% to about 95% cement.
8. The pumpable cement mixture of claim 7, further comprising at
least one of a retarder, a defoamer, and a polyanionic polymer.
9. A completed wellbore comprising the cement mixture of claim
7.
10. A fluid-loss cement additive comprising: about 1 part polyvinyl
alcohol, about 1 part NaCl, about 0.05 parts borax, about 0.05
parts calcium lignosulfonate; and about 0.12 parts defoamer.
11. The fluid-loss additive of claim 10, wherein the fluid-loss
additive is prepared on a weight basis in a dry blend and added at
a concentration of about 1 percent by weight of the cement.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority as a continuation of
U.S. Non-provisional patent application Ser. No. 12/704,333, filed
Feb. 11, 2010 which further claims priority as a continuation in
part to U.S. Non-provisional patent application Ser. No.
12/019,933, filed on Jan. 25, 2008, now U.S. Pat. No. 7,670,994,
issued Mar. 2, 2010, and International Application No.
PCT/US08/80838, filed Oct. 22, 2008 which further claims priority
to U.S. Non-provisional patent application Ser. No. 12/019,933,
filed on Jan. 25, 2008, now U.S. Pat. No. 7,670,994, issued Mar. 2,
2010.
FIELD OF THE INVENTION
[0002] The present invention relates to an improved cement additive
for treating oil and gas wells. Various further embodiments relate
to enhanced methods for treating oil and gas wells.
DESCRIPTION OF THE RELATED ART
[0003] Previous methods of fluid loss control have been attempted
by a one step addition of fluid loss control additive to the
cement, which hopefully reduces the ability of the liquid portion
of the slurry from rapidly penetrating a permeable zone at the
formation face. This creates a critical dependence of the fluid
control on the use of a fluid loss control additive that functions
at the temperature of the permeable zone. Also, the cement slurry
must be designed to complement the requirements of the fluid loss
additive for rheology of the fluid portion of the cement slurry.
Most fluid loss control additives thicken the cement slurry into
which they are mixed. Also, they may retard the hardening of the
cement when it reaches its required destination. To deal with such
properties, it is common for service companies to have many
different fluid loss control additives and to select the "best fit"
for the well conditions that are to be encountered.
[0004] As such, the art field is in search of additives and methods
to alleviate these issues.
SUMMARY OF THE INVENTION
[0005] Various embodiments of the present invention generally
relate to additives and methods for treating an oil and/or gas
well. In an embodiment, a method of the present invention generally
comprises an improved cement additive for treating oil and gas
wells that is added to a cement mixture comprising a polymer
composition, such as, for example, a polyvinyl alcohol. In an
embodiment, the additive is an electrolyte.
[0006] The cement polymer mixture undergoes cross linking when
exposed to the cross linking agent. The electrolyte inhibits that
cross-linking or polymerization. The additive has been shown to
inhibit the cross linking such that cement mixture can achieve
greater penetration into the formation before polymerization or
cross-linking. In various embodiments, when the polymer in the
cement mixture comes into contact with the wash composition's cross
linking agent, the polymer undergoes polymerization or cross
linking. This cross linking helps to prevent fluid loss into the
formation.
[0007] In an embodiment, the cement mixture comprises an additive,
a polymer, a suitable crosslinker for the polymer, and at least one
cement. Further embodiments comprise at least one retarder. Various
further embodiments comprise at least one defoamer. Various further
embodiments comprise a perlite.
[0008] Examples of components useful in the present invention can
be found in U.S. Pat. Nos. 5,009,269; 5,850,880; 5,728,210, the
contents of which are hereby incorporated by reference as if they
were reproduced herein in their entirety.
[0009] In various embodiments, the cement mixture comprising the
additive is added about the same time as the cross-linking
agent.
[0010] In various embodiments, circulation can be started with
addition of a first cement mixture comprising a polymer and a cross
linking agent followed shortly thereafter by the addition of an
additive comprising an electrolyte. In such an embodiment, the
first cement mixture acts as a wiper to remove excess drilling
mud.
[0011] In various embodiments, the cement mixtures are suitable for
subterranean applications such as well completion and remedial
operations. It is to be understood that "subterranean applications"
encompass both areas below exposed earth and areas below earth
covered by water such as ocean or fresh water. In various
embodiments, the cement mixtures include a sufficient amount of
water to form a pumpable slurry.
[0012] The density of the cement mixtures may vary. In various
embodiments, the cement mixtures may comprise a density of from
about 4 lb/gallon to about 23 lb/gallon. In alternative
embodiments, the cement mixtures may comprise a density of from
about 12 lb/gallon to about 17 lb/gallon. In other alternative
embodiments, the cement mixtures may be low-density cement mixtures
with a density of from about 5 lb/gallon to about 12 lb/gallon. In
general, the density can be selected for the drilling
operation.
[0013] In various embodiments, the cement mixture comprises at
least one cement such as hydraulic cement, which includes calcium,
aluminum, silicon, oxygen, and/or sulfur and which sets and hardens
by reaction with water. Examples of hydraulic cements include but
are not limited to Portland cements (e.g., classes A, C, G, and H
Portland cements), pozzolana cements, gypsum cements, phosphate
cements, high alumina content cements, silica cements, high
alkalinity cements, and combinations thereof.
[0014] Type I Portland cement is known as common or general purpose
cement. It is commonly used for general construction especially
when making precast and precast-prestressed concrete that is not to
be in contact with soils or ground water. The typical compound
compositions of this type are 55% (C.sub.3S), 19% (C.sub.2S), 10%
(C.sub.3A), 7% (C.sub.4AF), 2.8% MgO, 2.9% (SO.sub.3), 1.0%
Ignition loss, and 1.0% free CaO.
[0015] Type III has a relatively high early strength. Its typical
composition is 57% (C.sub.3S), 19% (C.sub.2S), 10% (C.sub.3A), 7%
(C.sub.4AF), 3.0% MgO, 3.1% (SO.sub.3), 0.9% Ignition loss, and
1.3% free CaO. The gypsum level may also be increased a small
amount. This gives the concrete using this type of cement a three
day compressive strength equal to the seven day compressive
strength of types I and II. Finally, other cement types useful in
the cement blend of the present invention include (high-early set)
HE and class C cements.
[0016] A sufficient amount of water is added to the cement mixture
to make the cement mixture pumpable. The water may be fresh water
or salt water, e.g., an unsaturated aqueous salt solution or a
saturated aqueous salt solution such as brine or seawater, or a
non-aqueous fluid. The water may be present in the amount of from
about 16 to about 180 percent by weight of cement, alternatively
from about 28 to about 60 percent by weight of cement. In general,
any amount of water can be used as would be understood by one of
ordinary skill in the art.
[0017] In various embodiments an amount of an additive comprising
an electrolyte is added such that the ratio of polymer to
electrolyte is 1:1. In an alternate embodiment, the amount of an
additive comprising an electrolyte added is in excess of the amount
of polymer added. In an alternate embodiment, the amount of an
additive comprising an electrolyte added is 50% in excess of the
amount of polymer. In an alternate embodiment, the amount of an
additive comprising an electrolyte added is about 100% in excess of
the amount of the polymer. In an alternate embodiment, the amount
of an additive comprising an electrolyte added is about 200% in
excess of the amount of the polymer. In an alternate embodiment,
the amount of an additive comprising an electrolyte added is about
500% in excess of the amount of the polymer. In an alternate
embodiment, the amount of an additive comprising an electrolyte
added is about 50% less than the amount of the polymer. In an
alternate embodiment, the amount of an additive comprising an
electrolyte added is about 75% less than the amount of the polymer.
In an alternate embodiment, the amount of an additive comprising an
electrolyte added is about 90% less than the amount of the polymer.
In an alternate embodiment, the amount of an additive comprising an
electrolyte added is about 25% less than the amount of the polymer.
In general, any amount of an additive comprising an electrolyte can
be used and can be governed by one of ordinary skill in the art
based on the polymer, results, cost, and/or the like.
[0018] As such, in various embodiments methods for inhibiting fluid
loss from an oil and gas well are disclosed comprising the steps of
adding an electrolyte into a cement mixture comprising a cross
linking agent and a polymer, and pumping said cement mixture into
said well's borehole to cement at least a portion of a formation
face, said cement mixture comprising a polymer composition, wherein
polymerization of said polymer is inhibited, thereby inhibiting
fluid loss from said well's borehole to said formation.
[0019] Various embodiments of the present invention comprise a
fluid loss additive for use in a cement mixture to complete a well
bore, said fluid loss additive comprising an electrolyte, a polymer
and a cross linking agent. An embodiment comprises about 1%
electrolyte to about 99% electrolyte, about 1% polymer to about 99%
polymer, and about 0.1% cross linking agent to about 5% cross
linking agent. An alternate embodiment comprises about 5%
electrolyte to about 90% electrolyte, about 5% polymer to about 90%
polymer, and about 0.1% cross linking agent to about 5% cross
linking agent. An alternate embodiment comprises about 15%
electrolyte to about 75% electrolyte, about 15% polymer to about
75% polymer, and about 0.01% cross linking agent to about 3% cross
linking agent. An alternate embodiment comprises about 25%
electrolyte to about 50% electrolyte, about 25% polymer to about
50% polymer, and about 0.01% cross linking agent to about 2% cross
linking agent. In general, the relative proportions of the
electrolyte, the polymer, and the cross linking agent can be
varied. Various further embodiments comprise at least one of a
retarder, a defoamer, and a polyanionic polymer.
[0020] Various embodiments of the present invention comprise a kit
for inhibiting fluid loss from an oil and gas well comprising about
1% electrolyte to about 99% electrolyte, about 1% polymer to about
99% polymer, and about 0.1% cross linking agent to about 5% cross
linking agent. An alternate embodiment of a kit comprises about 5%
electrolyte to about 90% electrolyte, about 5% polymer to about 90%
polymer, and about 0.1% cross linking agent to about 5% cross
linking agent. An alternate embodiment of a kit comprises about 15%
electrolyte to about 75% electrolyte, about 15% polymer to about
75% polymer, and about 0.01% cross linking agent to about 3% cross
linking agent. An alternate embodiment of a kit comprises about 25%
electrolyte to about 50% electrolyte, about 25% polymer to about
50% polymer, and about 0.01% cross linking agent to about 2% cross
linking agent. In general, the relative proportions of the
electrolyte, the polymer, and the cross linking agent in the kit
can be varied. Various further embodiments of a kit comprise at
least one of a retarder, a defoamer, and a polyanionic polymer.
[0021] Further embodiments comprise a wellbore treated to inhibit
fluid loss with the composition as herein described.
[0022] In various embodiments, a pumpable cement mixture is
disclosed comprising about 0.01% to about 5.0% electrolyte, about
0.01% to about 5.0% polymer, about 0.001 to about 0.1% cross
linking agent, about 5% to about 50% water, and about 30% to about
95% cement. In an alternate embodiment, a pumpable cement mixture
is disclosed comprising about 0.0001% to about 3.0% electrolyte,
about 0.001% to about 3.0% polymer, about 0.0001 to about 0.3%
cross linking agent, about 10% to about 40% water, and about 40% to
about 90% cement. In an alternate embodiment, a pumpable cement
mixture is disclosed comprising about 0.1% to about 3.0%
electrolyte, about 0.1% to about 3.0% polymer, about 0.1 to about
0.3% cross linking agent, about 20% to about 30% water, and about
50% to about 70% cement. In general, various embodiments of the
present invention are capable of comprising varying proportions of
electrolyte, polymer, cross-linking agent, water and cement.
Various embodiments further comprise at least one of a retarder, a
defoamer, and a polyanionic polymer. Further disclosed is a
completed wellbore comprising a pumpable cement mixture as herein
disclosed.
[0023] The foregoing has outlined rather broadly the features of
the present disclosure in order that the detailed description that
follows may be better understood. Additional features and
advantages of the disclosure will be described hereinafter, which
form the subject of the claims.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0024] In the following description, certain details are set forth
such as specific quantities, sizes, etc. so as to provide a
thorough understanding of the present embodiments disclosed herein.
However, it will be obvious to those skilled in the art that the
present disclosure may be practiced without such specific details.
In many cases, details concerning such considerations and the like
have been omitted inasmuch as such details are not necessary to
obtain a complete understanding of the present disclosure and are
within the skills of persons of ordinary skill in the relevant
art.
[0025] The following definitions and explanations are meant and
intended to be controlling in any future construction unless
clearly and unambiguously modified in the following Description or
when application of the meaning renders any construction
meaningless or essentially meaningless. In cases where the
construction of the term would render it meaningless or essentially
meaningless, the definition should be taken from Webster's
Dictionary, 3rd Edition. Definitions and/or interpretations should
not be incorporated from other patent applications, patents, or
publications, related or not, unless specifically stated in this
specification or if the incorporation is necessary for maintaining
validity.
[0026] As used herein, the term "lignosulfonate" means and refers
to lignosulfonates, or sulfonated lignins, and are water-soluble
anionic polyelectrolyte polymers.
[0027] As used herein, the term "PVA" or "polyvinyl alcohol" means
and refers to a partially hydrolyzed polyvinyl acetate polymer
having at least about 80 percent of the acetate groups hydrolyzed.
PVA has been a desired fluid loss control agent because of its low
cost, its lack of a set retarding function, and the fact that it is
not totally water soluble, so that its effect on slurry viscosity
is minimal. However, the PVA-based materials previously used have
been less effective at temperatures above about 50 degrees C.
because the PVA becomes essentially water-soluble. Also, PVA has
not been particularly effective in cement slurries formulated with
fresh water.
[0028] As used herein, the terms "cross link" and "polymerize" are
used interchangeably, unless such use would be irrational.
[0029] As used herein, the term "electrolyte" means and refers to a
chemical compound that ionizes when dissolved or molten to produce
an electrically conductive medium. Electrolytes commonly exist as
solutions of acids, bases or salts. Furthermore, some gases may act
as electrolytes under conditions of high temperature or low
pressure. Electrolyte solutions can also result from the
dissolution of some biological (e.g., DNA, polypeptides) and
synthetic polymers (e.g., polystyrene sulfonate), termed
polyelectrolytes, which contain charged functional group.
Electrolyte solutions are normally formed when a salt is placed
into a solvent such as water and the individual components
dissociate due to the thermodynamic interactions between solvent
and solute molecules, in a process called solvation. For example,
when table salt, NaCl, is placed in water, the salt (a solid)
dissolves into its component elements.
[0030] The additive is comprised of the following components:
one part PVA that is readily soluble such as DuPont's Elvanol is
preferred, partially hydrated PVA such as Elvanol 50-42S8 is
preferred. a suitable crosslinker for the PVA such as boric acid,
other soluble borates, titanates, or zirconates in the amount of
approximately 0.05 parts by weight. an electrolyte such as NaCl in
the amount of approximately equal weight to the PVA (one part by
weight. a neutralizing compound such as calcium lignosulfonate in
the amount of approximately 0.05 parts by weight). a defoamer in
the amount of approximately 0.1 parts by weight.
[0031] Various embodiments of the present invention can use any
cross linking agent. The cross-linking agent can comprise a borate
releasing compound or any of the well known transition metal ions
which are capable of creating a cross-linked structure. Examples of
cross-linking agents include, but are not limited to, borate
releasing compounds, a source of titanium ions, a source of
zirconium ions, a source of antimony ions and a source of aluminum
ions. Generally any cross linking agent can be used.
[0032] A cross linking agent can come from any source, such as
sodium tetraborate, potassium tetraborate, boric acid, boron oxide,
or calcium hexaboride, and the like. Titanate and zirconate
cross-linking agents can be used as full or partial substitutes for
the water-soluble borates, but are not as preferred.
[0033] In general, any polymer can be used with various embodiments
of the present invention, such as a polymerization product formed
by polymerizing a 2-acrylamido-2-methylpropane sulfonic acid,
2-methacrylamido-2-methylpropane sulfonic acid, sulfonated styrene,
vinyl sulfonic acid, allyl ether sulfonic acids such as propane
sulfonic acid allyl ether, methallyl ether phenyl sulfonates,
acrylic acid, methacrylic acid, maleic acid, itaconic acid,
n-acrylamidopropyl-n,n-dimethyl amino acetic acid,
n-methacrylamidopropyl-n,n-dimethyl amino acidic acid,
n-acryloyloxyethyl-n,n-dimethyl amino acidic acid,
n-methacryloyloxyethyl-n,n-dimethyl amino acidic acid,
n-acryloyloxyethyl-n,n-dimethyl amino acidic acid,
n-methacryloyloxyethyl-n,n-dimethyl amino acidic acid, crotonic
acid, acrylamidoglycolic acid, methacrylamidoglycolic acid,
2-acrylamido-2-methylbutanoic acid and
2-methacrylamido-2-methylbutanoic acid. Nonionic monomers which can
be used in the formed (synthesized, intercalated) polymer include,
but are not limited to, C.sub.1-C.sub.22 straight or branched chain
alkyl or aryl acrylamide, C.sub.1-C.sub.22 straight or branched
chain n-alkyl or aryl methacrylamide, acrylamide, methacrylamide,
n-vinylpyrrolidone, vinyl acetate, ethoxylated and propoxylated
acrylate, ethoxylated and propoxylated methacrylate, hydroxy
functional acrylates such as hydroxyethylacrylate and
hydroxypropylacrylate, hydroxy functional methacrylates such as
hydroxyethylmethacrylate and hydroxypropylmethacrylate,
n,n-dimethylacrylamide, n,n-dimethylmethacrylamide, styrene,
styrene derivatives and C.sub.1-C.sub.22 straight or branched chain
alkyl, aryl, allyl ethers, poly vinyl alcohol (PVA), and/or the
like.
[0034] In general, any electrolyte can be used with various
embodiments of additives of the present invention.
[0035] In embodiments utilizing PVA, at least in part, while not
intending to be bound, the mechanism by which PVA controls fluid
loss is believed to be different from that of other fluid loss
materials. Most fluid loss additives are high molecular weight
polymers that are totally water-soluble and form some type of a
structure between the cement particles, which reduces the
permeability of the filter cake. PVA is not totally water-soluble
below about 50 degrees C., but is, instead, "water-swellable." The
individual PVA particles swell and soften to form small gel-balls
in the slurry. These gel-balls deform by flattening, and become a
part of the filter cake, greatly reducing the filter cake
permeability, thus giving extremely good fluid loss control.
Because PVA is not totally water-soluble, it does not significantly
increase the slurry viscosity. PVA does not retard the set of
cement.
[0036] Variations in the degree of hydrolysis of the polyvinyl
alcohol, the molecular weight of the polyvinyl alcohol, and the
inclusion of up to 25 percent by weight of substituents on the
polyvinyl alcohol, such as methacrylate, methmethacrylate and the
like are within the scope of the present invention. In addition,
the preferred embodiment can contain calcium sulfate in a form such
as dihydrate or anhydrite, but present in an amount equivalent to
from 0 to 60 percent by weight of calcium sulfate hemihydrate.
[0037] The surfactant can be any of a wide range of materials such
as ethoxylated alkyl phenols, ethoxylated primary or secondary
alcohols, ethoxylated fatty alcohols, ethoxylated amines,
ethoxylated amides, ethoxylated fatty acids, ethoxylated diamines,
and ethoxylated quaternary ammonium chlorides. Suitable surfactants
are described in detail in U.S. Pat. No. 5,105,885, the contents of
which are hereby incorporated by reference as if it was reproduced
herein in its entirety.
[0038] Antifoam materials useful in the present invention are
usually polypropylene glycols but any suitable substitute can be
utilized.
[0039] Cement retarding additives can also be added to the fluid
loss additives. At temperatures above 80 degrees F., cement sets in
a short period of time. Retarders, such as lignosulfonate
materials, lengthen the time the cement slurry will stay liquid,
allowing the slurry to be pumped down the casing and back up the
annulus before setting.
[0040] For embodiments comprising sulfonated polymer dispersing
agents, such materials are capable of being sulfonated
polymelamine, sulfonated polystyrene or vinyl sulfonate polymers or
mixtures of these. Other sulfonated polymer materials can be
substituted provided that materials can be prepared at low pH and
neutralized to form salts of the polymers. The salts can be sodium,
potassium, lithium, ammonium, calcium, magnesium, and the like. The
sulfonated polymer is added in a quantity of 0.05 to 2.0 percent by
weight of the cement. These sulfonated polymers are available in
liquid or powdered form. The weight percent specified is based on
sulfonated polymer only and does not include the weight of any
water that may be present in the liquid form.
[0041] In preparing the low viscosity dry mixed fluid loss control
additive of the present invention, the components to the cement can
be added as a single blend, or as individual components, or in any
combination or order of addition.
[0042] The present invention is both compositions and methods for
treating an oil or gas well and uses a cross linking agent, such as
borax, and an additive comprising an electrolyte, in various
embodiments. Various further embodiments comprise an electrolyte,
such as a salt.
[0043] In various embodiments, the additive comprising an
electrolyte is added at the same time as the cement mixture. A
cross linking agent or additive helps to inhibit fluid loss into
the formation. Likewise, the additive comprising an electrolyte
inhibits fluid loss into the formation.
[0044] Further embodiments of the present invention comprise kits.
Kits of the present invention are capable of containing different
constituents or components of the cement mixture. In an embodiment,
a kit of the present invention comprises a polymer and an additive
comprising an electrolyte. In an alternate embodiment, a kit of the
present invention comprises a polymer, an additive comprising an
electrolyte, and a cross linking agent. Further kits may include,
alternatively, retarders, defoamers, fluid loss additives, and/or
the like.
[0045] The invention may be embodied in other specific forms
without departing from its spirit or essential characteristics. The
described embodiments are to be considered in all respects only as
illustrative and not restrictive. The scope of the invention is,
therefore, indicated by the appended claims rather than by the
foregoing description. All changes to the claims that come within
the meaning and range of equivalency of the claims are to be
embraced within their scope. Further, all published documents,
patents, and applications mentioned herein are hereby incorporated
by reference, as if presented in their entirety.
EXAMPLES
[0046] It has been discovered, in various embodiment and/or various
conditions, that polyvinyl alcohol used in cementing formulations
for fluid-loss prevention can be much more effective if a
crosslinker such as borax or boric acid is used with an
electrolyte, such as, but not limited to NaCl. Various further
embodiments include a plasticizer, such as, but not limited to
calcium lignosulfonate. Various further embodiments comprise a
defoamer. In an effort to accomplish that objective, in an
embodiment, we have found that a cement additive comprising about 1
part polyvinyl alcohol, about 1 part NaCl, about 0.05 parts borax,
about 0.05 parts calcium lignosulfonate and about 0.12 parts
defoamer prepared on weight basis in a dry blend and added at a
concentration of about 1 percent by weight of the cement achieves
the desired result. The proportions of constituents can be varied
widely and are often chosen based upon a particular well and
geological aspects of the well. As such, the proportions of
components in various embodiments of the present invention can be
varied widely.
[0047] In various embodiments, the percentage of cement additive is
greater than 1 percent by weight of cement. In various alternate
embodiments, the percentage of cement additive is less than 1
percent by weight of cement.
[0048] In an alternate embodiment, the ratio of polymer to
electrolyte is such that an excess of polymer is used. Various
suitable ratios include, but are not limited to about 1.1:1; 1.5:1;
2:1; 3:1; 4:1; 5:1; and greater than 5:1. In an alternate
embodiment, the ratio of polymer to electrolyte is such that an
excess of electrolyte is used. Various suitable ratios include, but
are not limited to about 1:1.1; 1:1.5; 1:2; 1:3; 1:4; 1:5; and
greater than 1:5. In general, any ratio of polymer to electrolyte
can be used.
[0049] In various embodiments, a polymer is added with a
crosslinker to a dry cement mixture which is then blended with
water. Also, a liquid version of the polymer and/or crosslinker are
capable of use. In various embodiments the polymer begins reacting
with the caustic cement and hydrates the mixture of cement and
water upon contact with the polymer. As such, the crosslinker is
subjected to chemical reactions that are not desirable.
[0050] In various embodiments, various embodiments of the proposed
new method involve changing the ionic environment to delay the
polymer hydration. Such delay will allow the first hydration
reaction of the cement mixture to take place before the polymer is
in solution. In various conventional methods the crosslinker and
polymer are sometimes neutralized by these initial cement reactions
and are then not available for the intended purpose of fluid-loss
control. The controlled solution of the invention overcomes this
shortcoming of fresh water solubility of polymer in cement
slurries. It was found that the solution alteration brought about
by the salt (electrolyte) and/or lignosulfonate (plasticizer)
resulted in less fluid loss from the cement slurry and less
susceptibility to temperature effects on the polymer.
[0051] The amount of "Improved PVA-Mixture" needed for fluid-loss
control is determined in laboratory testing procedures such as
American Petroleum Institute Research Procedures 10B, as is known
by one of ordinary skill in the art with reference to the teachings
of the various embodiments of the present invention.
[0052] In one aspect, an improvement of embodiments of the present
invention is that no different consideration or special mixing
procedures are needed because of the "Improved PVA-Mixture." The
cementing operation is capable of being performed as it would
normally be done.
[0053] It is conceivable that the benefit of controlled hydration
of a crosslinker and PVA in glues or other conventional
applications would be a logical use of the invention. [0054] Any
crosslinker for a polymer such as borates, titanates, zirconates,
and mixtures of these are possible candidates for various
embodiments of methods of the present invention. [0055] A polymer
should be readily soluble such as DuPont's Elvanol. Partially
hydrated PVA such as Elvanol FL42B. [0056] An electrolyte such as
NaCl is capable of use.
[0057] After the amount needed is known that amount will be added
to the dry cement blend and taken to the job location. The results
of using "Improved Polymer-Mixture" should be a much more effective
control of slurry viscosity and fluidity of the pumped slurry.
Also, loss of the fluid portion of the slurry should be
significantly reduced.
[0058] Holcim class G Cement with the fluid-loss additive BOA-C:
Samples of Holcim class G cement from Columbia have been tested
with the fluid loss control additive designated BOA-C. BOA-C is the
designation given to the additive disclosed herein. BOA-C has been
found to perform with better compatibility to various cements than
most other fluid-loss materials. The following tests give the
concentrations in percent by weight of cement used. Fluid-loss
tests were at a test pressure of 1000 psi using API-RP 10 standard
research procedures. The R-61 is a retarder received from Columbia.
Rheology tests were conducted using a Fann V-G Meter with a number
1 standard spring at 80.degree. F. Preferred slurry density was
15.6 lb/gal.
Fluid-Loss Tests
TABLE-US-00001 [0059] Temp ml/30 API .degree. F. min. (ml/30 min.
1.1% BOA-C + 46% water 80 13 26 1.1% BOA-C + 46% water 80 8 16
(2.sup.nd test) 0.75% BOA-C + 46% water 80 23 45 1.1% BOA-C + 0.3%
R-61 + 110 11 21 46% water 1.1% BOA-C + 0.3% R-61 + 110 9 18 46%
water (2.sup.nd test) 1.3% BOA-C + 0.125% R-61 + 110 16 32 46%
water 1.0% BOA-C + 0.6% R-61 + 125 10 20 46% water
Rheology:
TABLE-US-00002 [0060] Atmospheric Consistometer Yield Pt. Viscosity
(B.sub.c) Plastic Vis. (cps) (lbs/100 ft.sup.2) 1.3% BOA-C + 0.125%
R-61 + down 53 62 46% water initial-12 20 min.--16 1.3% BOA-C +
0.125% R-61 + up 55 59 46% water initial-12 20 min.--16 0.75% BOA-C
+ 46% water down 51 62 initial-11 20 min.--15 0.75% BOA-C + 46%
water up 55 58 initial-11 20 min.--15
Compressive Strength:
[0061] 1.1% BOA-C+46% water at 80.degree. F. and 1000 psi curing
pressure for 12 hours--844 psi
[0062] Fluid-Loss Tests Using BOA-C with EX490: The following
laboratory tests show results using BOA-C fluid-loss additive. All
tests are in accordance with API-RP 10 testing procedures. The
tests listed are with a compatible retarder EX490. Viscosity is in
Bearden Units from an atmospheric consistometer.
Cement System Components:
[0063] 1. Lafarge G cement+1.3% BOA-C+1% EX490+44% water 2. Tijeras
G cement+35% silica flour+2.3% BOA-C+1.35% EX490+60% water 3.
Tijeras G cement+35% silica flour+2.3% BOA-C+1.0% EX490+60% water
4. Tijeras G cement+35% silica flour+2.3% BOA-C+0.75% EX490+60%
water 5. Tijeras G cement+35% silica flour+2.3% BOA-C+0.625%
EX490+60% water 6. Tijeras G cement+35% silica flour+2.3%
BOA-C+0.5% EX490+60% water 7. Tijeras G cement+35% silica
flour+2.0% BOA-C+0.75% EX490+60% water
TABLE-US-00003 Cement Fluid Loss Fluid Loss Fluid Loss Fluid Loss
System Viscosity Viscosity (ml/30 min) (ml/30 min) (ml/30 min)
(ml/30 min) Components (initial) (20 min.) 140.degree. F.
167.degree. F. 197.degree. F. 220.degree. F. 1. (test one) 11 12 34
-- -- -- 1. (test two) 11 12 30 -- -- -- 1. (test one) 12 9 -- 37
-- -- 1. (test two) 11 12 -- 33 -- -- 1. (test one) 12 7 -- -- 31
-- 1. (test two) 12 7 -- -- 26 -- 2. 18 10 -- -- -- 29 2. 13 15 --
-- -- 125 3. 13 15 -- -- -- 45 4. 13 15 -- -- -- 36 5. 13 30 -- --
-- 32 6. 13 29 (test aborted due to viscosity increase) 7. 12 20 --
-- -- 165
[0064] The conventional use of polymer, such as PVA, at the present
time is a simple addition of the PVA and crosslinker to a dry
cement then blended together before mixing with water. Also, a
liquid version of the PVA and crosslinker is sometimes used which
is then added to the mix water. In these methods the PVA begins
reacting with the caustic cement hydrates the instant the mixture
of cement and water contacts the PVA. Also, the crosslinker is
subjected to chemical reactions that are not in a desirable
progression. In various embodiments, the proposed new method
involves changing the ionic environment to delay the PVA hydration
in a caustic water solution of the cement mix water. This will
allow the first hydration reactions of the cement to take place
before the PVA, or other polymer, is in solution. In the
conventional method the crosslinker and PVA are sometimes
neutralized by these initial cement reactions and are not then
available for the intended purpose of fluid-loss control. The
controlled solution of the invention overcomes this shortcoming of
fresh water solubility of PVA in cement slurries. It was found that
the solution alteration brought about by the salt and
lignosulfonate resulted in less fluid loss from the cement slurry
and less susceptibility to temperature effects on the PVA.
TABLE-US-00004 Fluid Loss Study Using PVA in Portland Cement
Temperature 80 100 110 125 110 110 110 110 110 110 Mix 1 Mix 2 Mix
3 Mix 4 Mix 5 Mix 6 Mix 7 Mix 8 Mix 9 Mix 10 Cement 600 600 600 600
600 600 400 400 400 400 PVA 3 3 3 3 3 3 2 2 2 2 Boric acid 0.15
0.15 0.15 0.15 -- -- -- 0.1 0.1 0.1 Borax -- -- -- -- 0.2 -- -- --
-- -- DWD -- -- -- -- -- -- 1 -- -- -- Defoamer 0.5 0.5 0.5 0.5 0.5
0.5 0.4 0.4 0.4 0.4 Retarder -- 1.2 1.8 2.4 1.8 1.8 1.2 1.2 1.2 1.2
Water 276 276 276 276 276 276 184 184 184 184 NaCl -- -- -- -- --
-- -- 8 4 2 Fluid loss (ml) 22 38 106 38 842 725 509 58 32 21
Temperature 80 110 125 80 80 80 80 80 80 Mix 11 Mix 12 Mix 13 Mix
14 Mix 15 Mix 16 Mix 17 Mix 18 Mix 19 Cement 400 600 400 400 400
400 400 400 400 PVA 2 2.6 2 2 2 2 2 2 2 Borax 0.2 0.26 0.2 0.2 0.2
0.2 0.2 0.2 0.2 Defoamer 0.4 0.33 0.22 0.4 0.4 0.4 0.4 0.4 0.4
Retarder -- 1.2 2.4 -- -- -- -- -- -- Water 184 264 176 184 184 184
184 184 184 NaCl 2 2.6 2 2 1 2 2 2 2 CaLignosulfonate -- -- -- --
-- 1 0.5 0.25 0.1 Fluid loss (ml) >1000 17 20 >1000 >1000
26 20 17 15 Temperatures are in degrees Fahrenheit. Test pressure
was 1000 psi. Components are in grams. Testing was done following
API RP 10 recommended procedures. Class G cement was used.
* * * * *