FLUID LOSS ADDITIVES FOR WELL CEMENTING COMPOSITIONS

ADJUVANTS POUR COMPOSITION DE CIMENTATION DE PUITS DE PRODUITS PETROLIERS, SERVANT A REDUIRE LE FILTRAT

English Abstract

32292CA
Abstract of the Disclosure
An additive for reducing water loss from cement comprising a
tetrapolymer, a base, an electrolyte, at least one surfactant, and water
is disclosed. A process for producing cement slurries with improved
water loss properties, as well as an improved method for cementing gas
and oil wells is also disclosed.

Claims

32292CA
The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. A fluid loss additive for cement slurries comprising:
a) from 29 to 95.0 weight percent of water;
b) from 0.1 to 70 weight percent of a tetrapolymer, wherein
said tetrapolymer is composed of
i) from 1 to 60 weight percent of N-vinyl-2-pyrrolidone;
ii) from 1 to 60 weight percent of at least one monomer
selected from the group consisting of acrylamide or methacrylamide;
iii) from 10 to 90 weight percent at least one monomer
selected from the group consisting of sodium 2-acrylamido-2-methyl-
propane sulfonate or 2-acrylamido-2-methylpropane sulfonic acid, and
iv) from 1 to 60 weight percent of at least one monomer
selected from the group consisting of acrylic acid or sodium
acrylate;
c) from 0.1 to 37.2 weight percent of an electrolyte;
d) from 0.1 to 3 weight percent of a base; and
e) from 0.1 to 40 weight percent of at least one surfactant.
2. The fluid loss additive of claim 1 wherein
a) said electrolyte is selected from the group consisting of
the sodium, potassium, or ammonium salt of chlorine, bromine, iodine,
fluorine, or nitrate;
b) said base is selected from the group consisting of K+OH-,
Na+OH-, or NH4+0H-;
c) said surfactant is selected from the group consisting of
i) carboxylates of the formula
RCOO- M+
wherein R is selected from the group consisting of alkyl groups
containing from 9 to 21 carbon atoms and M is selected from the
group consisting of sodium, potassium, and lithium;
ii) polyalkoxycarboxylates represented by the formula
<IMG>
wherein R is selected from the group consisting of alkyl and
alkylaryl groups containing from 10 to 21 carbon atoms; M is

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selected from the group consisting of sodium, lithium, or potassium,
and n is an integer from 5 to 21.
iii) sulfonates of the formula
RS03- M+
wherein R is selected from the group consisting of alkyl groups
containing from 10 to 20 carbon atoms; M is selected from the group
consisting of sodium, potassium, or lithium;
d) alkylbenzene sulfonates represented by the formula
RC6H4S03- M+
wherein R is selected from the group consisting of alkyl groups
containing from 10 to 20 carbon atoms and M is selected from the group
consisting of sodium, lithium, or potassium;
e) lignosulfonates
f) naphthalene sulfonates of the formula
RC10H6S03 M+
wherein R is selected from the group consisting of alkyl groups
containing from 3 to 10 carbon atoms, and M is selected from the group
consisting of sodium, lithium, calcium, or potassium.
g) naphthalene sulfonates which have condensed with
formaldehyde;
h) alpha-olefin sulfonates of the formula
RC=CHS03- M+
wherein R is selected from the group consisting of alkyl groups
containing from 10 to 20 carbon atoms and M is selected from the group
consisting of potassium, sodium or lithium.
i) poly(ethylene glycol) monomethyl ethers of the formula
HC-(CH2CH2-0)XCH3
wherein x can vary from about 20 to about 225,000.
j) polyethylene glycols of the formula
HO(CH2CH2-0)X CH20H
wherein x can vary from about 20 to about 225,000.
k) alcohol exthoxylates of the formula
R[OCH2CH2]n-OH
wherein R is selected from the group consisting of alkyl groups
containing from 6 to 20 carbon atoms and n is an integer from 2 to 100.

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1) alkylphenyl ethoxylates of the formula
RC6H4(0C2H2)n -OH
wherein R is selected from the group consisting of alkyl groups
containing from 8 to 15 carbon atoms and n is an integer from 2 to 70;
and
m) petroleum sulfonates.
3. The fluid loss additive of claim 1 wherein there is
additionally present therein from 0.001 to 5 weight percent of a
preservative.
4. The fluid loss additive of claim 3 wherein said
preservative is paraformaldehyde.
5. The fluid loss additive of claim 3 wherein
a) said tetrapolymer is present in the quantity of from 1.5
to 10 weight percent and contains from 30 to 40 weight percent of
Nvinyl2pyrrolidone from 50 to 60 weight percent of sodium
2-acrylamido-2-methylpropane sulfonate, from 1 to 10 weight percent of
acrylic acid, and from 5 to 15 weight percent of acrylamide;
b) said electrolyte is present in the quantity of from 2 to
10 weight percent;
c) said base is present in the quantity of from 0.2 to 2.0
weight percent;
d) said surfactant is present in the quantity of from 5 to 15
weight percent;
e) said preservative is present in the quantity of from 0.008
to 0.05 weight percent;
f) said water is present in the quantity of from 70 to 80
weight percent.
6. The fluid loss additive of claim 3 wherein
a) said tetrapolymer contains 35 weight percent of
N-vinyl-2-pyrrolidone, 55 weight percent of sodium 2-acrylamido-2-
methylpropane sulfonate, 5 weight percent of acrylic acid and 10 weight
percent of acrylamide;
b) said electrolyte is KCI;
c) said base is KOH;

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d) said surfactants are sodium naphthalene formaldehyde
condensate and poly(ethylene glycol) monomethyl ethers; and
e) said preservative is paraformaldehyde.
7. The fluid loss additive of claim 6 wherein
a) said poly(sodium 2-acrylamido-2-methylpropane sulfonate-
co-N-vinyl-pyrrolidone-co-acrylamide-co-acrylic acid) is present in the
quantity of about 5 weight percent;
b) said KCI is present in the quantity of about 2 weight
percent;
c) said KOH is present in the quantity of about 1 weight
percent;
d) said sodium naphthalene formaldehyde condensate is present
in the quantity of about 9.8 weight percent and said poly(ethylene
glycol) monoethyl ether is present in the quantity of about 4 weight
percent;
e) said paraformaldehyde is present in the quantity of about
0.02 weight percent;
f) said water is present in the quantity of about 78 weight
percent.
8. A cement slurry comprising:
a) water;
b) hydraulic cement;
c) the fluid loss additive of claim 1 wherein said fluid loss
additive is present in the quantity of 0.2 to 2.5 gallons per 94 lbs. of
cement present in said slurry.
9. The cement slurry of claim 8 wherein said fluid loss
additive is the fluid loss additive of claim 7.
10. A process for producing a cement having low fluid loss
properties comprising admixing
a) water;
b) a hydraulic cement;
c) the fluid loss additive of claim 1 in the quantity of 0.2
to 2.5 gallons per 94 lbs. of cement present therein.
11. The process of claim 10 wherein said fluid loss additive
is the fluid loss additive of claim 7.

19
12. In a process for cementing oil and gas wells wherein a
slurry of hydraulic cement is pumped into the well bore and allowed to
solidify wherein the improvement which comprises admixing from 0.2 to
2.5 gallons of the fluid loss additive of claim 1 for every 94 lbs. of
cement utilized in forming said cement slurry.
13. The process of claim 12 wherein said hydraulic cement
slurry is subjected to temperatures ranging from 80°F to 450°F.
14. The process of claim 12 wherein said fluid loss additive
is the fluid loss additive of claim 7.
15. The process of claim 12 wherein said fluid loss additive
is the fluid loss additive of claim 7 and wherein said hydraulic cement
slurry is subjected to temperatures ranging from 80°F to 450°F.

Description

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1 3 1 7452
F~UID LOSS ADDITIVES FOR
WELL OEMENTING COMPOSITIONS
The present invention pertains to cement slurry additives which
are useful for preventing water loss from cement slurries. Another
aspect of the invention relates to a method for preventing wat~r loss
from cement slurries. Another aspect of the invention relates to cement
slurries which have improved water loss properties. A still further
aspect of the invention relates to an improved process for cementing oil
and gas wells.
Cement compositions are used in the oil and gas industry to
cement the annular space in the well bore between the surrounding
formation and the pipe or casing. Typically, the cement slurry is pumped
down inside of the casing and back up the outside of the casing through
the annular space. The amount of water which is used in forming the
cement slurry will vary depending upon the type of hydraulic cement
selected and the job conditions at hand. The amount of water used can
vary over a wide range, depending upon such factors as the required
consistency of the slurry and upon the strength requirement for the
particular job.
Many times the hydraulic cement must be placed within or next
to a porous medium. For example, earthen strata in the well bore. When
this happens, water tends to filter out of the slurry and into the strata
during the settling of the cement. Many difficulties are related to an
uncontrolled fluid loss of this type such as uncontrolled setting rate,
improper placement of the slurry, impaired strength properties, and
, .

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2 1 3 1 7 4 5 2
contamination of the surrounding strata. These condi~ions are all
undesirable in oil and gas well cementing operations.
In order to lessen the loss of fluid from the aqueous cement
slurry, various materials have been employed in the past. Unfortunately,
these materials often have adverse effects upon the cement itself.
For example, U.S. 4,015,991 teaches the use of a copolymer of
acrylamide and 2-acrylamido-2-methylpropane sulfonic acid as a fluid loss
additive for cement slurries. Although this copolymer will reduce the
fluid loss from cement slurries, it also has the undesirable effect of
reducing the compressive strength of the cement and of retarding the rate
at which the cement forms a solid.
A further problem with the fluid loss additives currently
available, is their ineffectiveness at a temperature in the range of
300F to 450F. For example, the copolymer described in U.S. 4,015,991
is ineffective at a temperature in excess of 250F.
Thus, it would be a valuable contribution to the art to develop
additives which would reduce water loss from cement slurries without
having adverse effects upon the compressive strength of the cement or the
rate at which the cement solidifies.
It would also be a valuable contribution to the art to develop
additives which would reduce the water loss from cement slurries at
elevated temperatures.
It is an object of the present invention to provide additives
which will reduce the water loss from cement slurries without reducing
the compressive strength of the cement or delaying the rate at which the
cement solidifies. It is a further object of the present invention to
provide additives that will prevent the loss of water from cement
slurries at elevated temperatures. It is a further object of the present
invention to provide a method for reducing the loss of water from cement
slurries without reducing the compressive strength of the cement or
delaying the rate at which the cement solidifies. It is yet another
object of the present invention to provide a method for reducing the loss
of water from cement slurries at an elevated temperature. It is also an
object of the present invention to provide cement compositions having
improved water loss properties at elevated temperatures. It is yet a

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further object of the present invention to provide an improved method for
cementing oil and gas wells.
In accordance with the present invention, it has been
discovered that an additive comprising (A) a tetrapolymer, (B) an
S electrolyte, (C) a base, (D) at least one surfactant, and (E) water, will
reduce the water loss from cement slurries without reducing the
compressive strength of the cement or delaying the rate at which the
cement solidifies. It has also been discovered that this additive will
control the water loss from cement slurries at elevated temperatures.
As used in this application, the term tetrapolymer refers to a
water soluble polymer which is composed of a) from 1 to 60 weight percent
of N-vinyl-2-pyrrolidone, b) from 1 to 60 weight percent of at least one
monomer selected from the group consisting of acrylamide or
methacrylamide, c) from 10 to 90 weight percent of at least one monomer
selected from the group consisting of 2-acrylamido-2-methylpropane
sulfonic acid or sodium 2-acrylamido-2-methylpropane sulfonate, and d)
from 1 to 60 weight percent of at least one monomer selected from the
group consisting of acrylic acid or sodium acrylate.
The tetrapolymers of the present invention as well as their
methods of preparation are known to those skilled in the art. As such
their preparation can be achieved by polymerization in accordance with
any of the well known free radical techniques in solution, suspension or
emulsion environment. See, for example, U.S. 3,547,899, or European
patent application No. 0115836. In addition, such other methods of
polymerization as would have occurred to one skilled in the art may be
employed, and the present invention is not limited to any particular
method of preparing the tetrapolymers set out herein.
The molecular weight of the tetrapolymers of the present
invention may be varied over a considerable range. The molecular weight
may be as low as 30,000 or as high as 1,000,000 or more, provided, of
course that the properties of the aqueous hydraulic cement slurry to
which the tetrapolymer is added, are not adversely affected thereby.
At the present time the presently preferred tetrapolymer
contains from 30 to 40 weight percent of N-vinyl-2-pyrrolidone, from 5 to
15 weight percent of acrylamide, from 50 to 60 weight percent of sodium

1 3 1 7 4 5 2 32292CA
2-acrylamido-2-methylpropane sulfonate, and from 1 to 10 weight percent
of acrylic acid.
Suitable electrolytes (B) for use in the present invention can
be selected from the group consisting of sodium, potassium, lithium, or
ammonium salts of chlorine, bromine, iodine, nitrate, or fluorine. At
the present time, the preferred electrolyte is potassium chloride.
Suitable bases (C) for use in the present invention include
those selected from the group consisting of potassium hydroxide, sodium
hydroxide, or ammonium hydroxide. The presently preferred base is
potassium hydroxide.
Suitable (D) surfactants for use in the present invention can
be selected from the group consisting of:
1) carboxylates of the formula
RC00- M+
wherein R is selected from the group consisting of alkyl groups
containing from 9 to 21 carbon atoms and M is selected from the group
consisting of sodium, potassium, or lithium;
2) polyalkoxycarboxylates represented by the formula
o
ll
R-lOCH2CH2]nCH2C-0- M+
wherein R is selected from the group consisting of alkyl and alkylaryl
groups containing from 10 to 21 carbon atoms, M is selected from the
group consisting of sodium, lithium or potassium, and n is an integer
from 5 to 21;
3) sulfonates of the formula
; R S03 M+
wherein R is selected from the group consisting of alkyl groups
containing from 10 to 20 carbon atoms, and M is selected from the group
consisting of sodium, potassium, or lithium;
4) alkylbenzene sulfonates represented by the formula
RC6H4S03- M+
wherein R is selected from the group consisting of alkyl groups
containing from 10 to 20 carbon atoms, and M is selected from the group
consisting of sodium, lithium, or potassium;

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5) lignosulfonates;
6) naphthalene sulfonates of the formula
RC1oH6SO3~ Mt
wherein R is selected from the group consisting of alkyl groups
containing from 3 to 10 carbon atoms, and M is selected from the group
consisting of sodium, lithium, calcium or potassium;
7) naphthalene sulfonates which have been condensed with
formaldehyde;
8) the alpha-olefin sulfonates of the formula
RC=CHSO3- Mt
wherein R is selected from the group consisting of alkyl groups
containing from 10 to 20 carbon atoms and M is selected from the group
consisting of potassium, sodium or lithium;
9) poly(ethylene glycol) monomethyl ethers of the formula
HO-(CH2CH2O)X CH3
wherein x can vary from about 20 to about 225,000.
10) polyethylene glycols of the formula
HO(CH2CH2O)X H
wherein x can vary from about 20 to about 225,000.
11) alcohol ethoxylates of the formula
R[OCH2CH2]n OH
wherein R is selected from the group consisting of alkyl groups
containing from 6 to 20 carbon atoms and n is an integer from 2 to 100;
12) alkylphenyl ethoxylates of the formula
Rc6H4(oc2H4)n OH
wherein R is selected from the group consisting of alkyl groups
containing from 8 to 15 carbon atoms and n is an integer from 2 to 70;
and
13) petroleum sulfonates.
All of these surfactants as well as their methods of
preparation are well known to those skilled in the art. They are
available from numerous commercial suppliers.
At the present time it is preferred that the cement slurry
water loss additive contain two surfactants.

1 3 1 7 4 5 2 32292CA
One of the preferred surfactants is poly(ethylene glycol)
monomethyl ether. The surfactant will have a molecular weight ranging
from about 200 to about 8000, preferably 200 to 1000. Presently Dow
Froth 1012~ with molecular weight of about 385 is the most preferred.
The other preferred surfactant is a naphthalene sulfonate
formaldehyde condensate. Such compounds are also known as sulfonated
condensation products of formaldehyde and naphthalene or metal salts of
condensation products of naphthalene sulfonic acid with formaldehyde.
Condensed naphthalene sulfonate formaldehyde condensates
suitable for use in the present invention are marketed by a number of
companies under various brands and the preparation of some of these are
set forth, for example, in U.S. 3,537,869 or ~.S. 4,814,887. Examples of
commercially available naphthalene sulfonate formaldehyde condensates are
Lomar D~, CFR-2~, Tamol~, SM~, TIC~, and Doxad~. Currently Lomar D~ is
the preferred naphthalene sulfonate formaldehyde condensate.
At the present time, it is also preferred that the water loss
additive contain (F), a preservative. The nature of the preservative is
not critical to the practice of the present invention and any
commercially available preservative is suitable for use in the present
invention. At the present time, the preferred preservative is a
paraformaldehyde.
The constituents of the water loss additive are present in the
following quantities:
Broad Range Preferred Range
wt % wt b
A Tetrapolymer 0.1 - 70 1.5 - 10
B Electrolyte 0.1 - 37.2 2 - lO
C Base 0.1 - 3 .2 - 2
D Surfactant 0.1 - 40 5 - 15
30 E Water 29 - 95 70 - 80
F Preservative (optional) O.OO1 - 5 .008 - .05
The fluid additive of the present invention is suitable for use
with any hydraulic cement. The term hydraulic cement is meant to
encompass any organic cement that hardens or sets under water. Hydraulic

1 3 1 7 4 5 2 32292CA
cements, for example, include portland cements, aluminus and pozzolan
cements, and the like. The term hydraulic cement is also intended to
include cements having minor amounts of extenders such as bentonite,
gilsonite, and is also intended to include cements used either without
any appreciable sand or aggregate material or such cements admixed with a
granular filling material such as sand, ground limestone, and the like.
Thus, for example, any of the class A - J cements listed in API Spec 10,
Section 2, First Ed., January, 1982, are suitable for this purpose.
Strength enhancers such as silica powder can also be employed.
The dry hydraulic cement component, the fluid loss additive of
the present invention, is admixed with water to form a pumpable, settable
cement slurry. The cement sets to form a monolithic solid. The water
which is employed to form the cement slurry may be any naturally
occurring water suitable for preparing cement slurries. Sea water may be
employed and is thus convenient in offshore operations. It is a
particular advantage of the fluid loss additive of the present invention
that it is effective in reducing fluid loss from cement slurries even
where brines are employed to make up the slurry. This constitutes
another important advantage of the invention over many other cement
additives known in the art.
The amount of water employed to make up the hydraulic cement
slurry is not critical, and generally the amount of water necessary to
give a settable cement composition having the required characteristics
will be an amount from about 25 to about 150 percent by weight, based on
the weight of the dry hydraulic cement. As discussed previously, the
amount of water employed should be only such as is sufficient to produce
a pumpable slurry. Use of the water loss additive of the present
invention makes it unnecessary to add excess water in anticipation of
substantial water losses.
Generally, the amount of fluid loss additive employed will be
in the range of from 0.2 gal to 2.5 gal of additive per 94 lbs. of cement
utilized in preparing the cement slurry.
The fluid loss additive of the present invention is suitable
for use in cement slurries that are subjected to temperatures ranging
from 80F to 450F.

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In the method of cementing a well bore with the present
additive, a hydraulic cement, water and the fluid loss additive of the
present invention are mixed together to form a pumpable slurry. The
cement slurry so prepared is then pumped to the desired location in the
well bore and allowed to harden to form a so]id mass.
The following examples are intended to illustrate the
advantages of this invention, but are not intended to unduly limit this
invention.
Example I
The purpose of this example is to demonstrate -the composition
of and a method for preparing the preferred fluid loss additive of the
present invention.
The composition of the preferred fluid loss additive system of
the present invention is represented below.
TABLE I
Material Amount (wt in grams)
Water 78
KCI 2
KOH
Paraformaldehyde 0.02
Sodium naphthalene
formaldehyde condensate1 9.8
Poly(ethylene glycol)monomethyl
ether2 4
Tetrapolymer3 5
1 Lomar D~, Diamond Shamrock
2 Dow Froth 1012~, Dow
3 a poly(sodium 2-acrylamido-2-methylpropane sulfonate-co-N-vinyl-2-
pyrrolidone-co-acrylamide-co-acrylic acid), containing 55 wt % sodium
2-acrylamido-2-methylpropane sulfonate, 35 wt % N-vinyl-2-pyrrolidone, 10
wt % acrylamide, 5 wt % acrylic acid and is commercially available as HE~
polymer from Phillips Petroleum Company.

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A preferred manner of preparing this f:luid loss additive is to
mix the ingredients in the order listed under agitation.
Example II
A series of cementing slurry compositions in accordance with
the present invention and having the compositions as noted in Table II
below were prepared by mixing the additive system of Example I with water
and a Class H cementl.
TABLE II
Amount water loss in
Material Amount gal/sack of cement
Cement A
Class H cement829.85 gm 0.3 gal
Water 313.5 ml
Water loss additive 22.2 ml
Cement B
Class H cement829.85 gm 0.41 gal
Water 305.5 ml
Water loss additive 30.3 ml
Cement C
Class H cement829.85 gm 0.60 gal
Water 285.5 ml
Water loss additive 50.2 ml
Cement D
Class H cement829.85 gm 0.68 gal
Water 285.5 ml
Water loss additive 50.1 ml
Cement E
Class H cement829.85 gm 0.75 gal
Water 280.42 ml
Water loss additive 55.2 ml
Cement F (control)
Class H cement829.85 gm 0
Water 335.7 ml
Cement G (control)
Class H cement850.96 gm 0
Water 328.9 ml
Cement H
Class H cement645.92 gm 0.41 gal
Sand 226.1 gm
Water 284.35 ml
Water loss additive 23.51 ml

1 3 1 7 4 5 2 32292CA
Cement I
Class H cement 645.92 gm 0.60 gal
Sand 226.1 gm
Water 273.46 ml
Water loss additive 34.4 ml
Cement J
Class H cement 645.92 gm 0.75 gal
Sand 226.1 gm
Water 264.86 ml
Water loss additive 43.0 ml
Cement K
Class H cement 829.05 gm .80 gal
Water 275.8 ml
Water loss additive 58.9 ml
Cement L
Class H cement829.85 gm 1.00 gal
Water 261.1 ml
Water loss additive 73.7 ml
1 A Class H cement as defined in API Spec 10, Section 2.2, First Ed.,
January 1982. The cement used is commercially available from General
Portland under the brand name TRINITY LAFARGE H~
Example III
To demonstrate that the water loss additive of the present
invention will reduce the water loss from cement slurries over a broad
range of temperatures; the water loss properties of cementing slurry
compositions prepared as in Example II were determined in accordance with
API Spec 10, Appendix F, First Ed., January 1982.
The following results were obtained.
TABLE III
Concentration
of Additive Temp.Fluid-Loss
Cement(gal/94 lbs cement) F cc/30'
B 0.41 80 66
B 0.41 100 76
D 0.68 100 40
F (Control) 0.00 100 +1298
B 0.41 125 74
D 0.68 125 46

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11
F (Control) 0.00 125 tl298
B 0.41 170 80
~ 0.68 170 46
F ~Control) 0.00 170 +1500
H 0.41 170 78
I 0.60 170 48
H 0.41 200 118
I 0.60 200 131
I 0.60 230 138
I 0.60 250 40
J 0.75 300 54
The water loss properties of cement slurries prepared without
the additive of the present invention (cement F) were determined at
temperatures ranging from 100F to 170F. These cement slurries lost
between 1298 to 1500 cc of fluid during the 30 minute testing period.
The water loss properties of cement slurries prepared with the
additive of the present invention were determined at temperatures ranging
from 80F to 300F. These cements only lost from 40 to 138 cc of fluid
during the 30 minute testing period.
Thus, this data demonstrates that the addi.tive of the present
invention provides cements with superior water loss properties over a
broad temperature range.
Example IV
To demonstrate that the fluid loss additive of the present
invention does not decrease the compressive strength of the resulting
cement composition, a series of cement compositions as prepared in
Example II were tested in accordance with API Spec 10, Section 7,
Compressive Strength Tests, First Ed., January, 1982.
The following data was generated.

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TABLE IV
Concentration 24 Hr COMPRESSIVE STRENGTH (PSI)
of Additive @ Atmospheric
pressure @ 3000 PSI
Cement(galt94 lbs of cement 80F 125F 150F 170F
F (Control) 0.00 1483 3517 4646 4799
A 0.30 1483 3725 4697 4713
B 0.41 1508 3642 4689 5013
C 0.68 1550 3775 5847 6192
Cement F was prepared without the fluid loss additive of the
present invention. It demonstrated a compressive strength of 1483 PSI at
80F during a 24 hour compressive strength test.
Cements A, B, and C were prepared with the fluid loss additive
of the present invention. They demonstrated compressive strengths
ranging between 1483 to 1550 PSI. Thus, the additive of the present
invention doe~ not decrease the compressive strength of cements.
A similar trend was demonstrated in the tests conducted at
12SF, 150F, and 170F.
Example V
To demonstrate that the additive of the present invention will
reduce the fluid loss from cement slurries which have been formulated
with salt water, a cement slurry B~, D/, L/ and M/ were prepared as were
Cements B, D, L, and M of Example II except that varying concentrations
of salt water was used to prepare the cementing slurry. For comparative
purposes a cement slurry F was prepared as in Example II.
The fluid loss properties of these cement slurries were
determined in accordance with API Spec 10, Appendix F, First Ed.,
January, 1982.
The following results were obtained.
,

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TABLE V
Concentration
of Additive NaCL Temp. Fluid-Loss
Cement~gal/94 lbs cement) wt % F cc/30'
F (Control) 0 0.0 100 +1298
B/ 0.41 3.0 80 123
B/ 0.41 10.0 80 134
B/ 0.41 18.0 80 180
B/ 0.41 37.2 80 68
D/ 0.68 3 100 50
D/ 0.68 3 125 48
D/ 0.68 3 150 50
D/ 0.68 3 175 53
D/ 0.68 10 100 49
D/ 0.68 10 125 46
D/ 0.68 10 150 63
D/ 0.68 10 175 66
L/ 0.80 3 100 43
L/ 0.80 3 125 45
L/ 0.80 3 150 48
L/ 0.80 3 175 42
L/ 0.80 10 100 49
L/ 0.80 10 125 52
L/ 0.80 10 150 54
L/ 0.80 10 175 56
M/ 1.00 18 200 94
M/ 1.00 37.2 100 104
M/ 1.00 37.2 125 110
M/ 1.00 37.2 150 122
M/ 1.00 37.2 175 130
M/ 1.00 37.2 200 146
Cement F which was prepared without the additive of the present
invention, exhibited a fluid loss in excess of 1298 cc during the 30
minute testing period. The cement slurries prepared with the fluid loss
additive of the present invention only lost from 43 to 180 cc's during
the 30 minute test period. Thus, the fluid loss additive of the present
invention will reduce the water loss from cement slurries which have been
formulated with salt water.
Example VI
To demonstrate that the fluid loss additive of the present
invention does not retard the rate at which the cement solidifies,
cementing compositions were prepared as in Example II and the rate at
which the cement thickens was determined in accordance with API, Spec 10,
Section 8, First Ed., January, 1982.

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The following res~lts were obtained.
TABLE VI
Concentration Thickening Time
of Additive API (in hours)
5Cement(gal/94 lbs of cement)Temp.(F)Schedule 70 Bc100 Bc
F 0.00 80 lg3 4:454:57
B 0.41 80 lg3 4:114:25
C 0.68 80 lg3 5:085:19
F 0.00 100 3g4 2:493:14
B 0.41 100 3g4 2:543:28
C 0.68 100 3g4 3:023:30
F 0.00 125 5g3 1:361:46
B 0.41 125 5g3 1:431:47
C 0.68 125 5g3 1:522:00
Variations of 30 minutes or less in thickening time is considered
within normal experimental error.
Cement F which does not contain the fluid loss additive of the
present invention, thickened in 4 hours and 45 minutes when tested at
80F.
Cements B and C which contained the additive of the present
invention, thickened in 4 hours, ll minutes; and 5 hours, 8 minutes;
respectively.
Although at first glance it appears that the additive of the
present invention retarded the rate at which Cement C solidified, this is
not the case.
Due to the large amount of experimental error inherent in the
testing procedures, cements which thicken within 30 minutes of each other
are considered to have equivalent thickening rates. Therefore, the
additive of the present invention does not delay the rate at which cement
slurries solidify.
~ easonable variations can be made in view of the foregoing
disclosure without departing from the spirit or scope of the present
invention.