ACID VISCOSIFIER COMPOSITIONS

COMPOSITIONS POUR EPAISSIR UNE SOLUTION ACIDE

English Abstract

ABSTRACT OF THE DISCLOSURE
Cationic, anionic and amphoteric polymers
suitable for the preparation of acid viscosifier
compositions and the acid viscosified compositions
are provided. The polymers are water soluble or
water dispersible and are based on acrylyl monomers
having the stated ionic charge. They are capable of
viscosifying acid solutions that have important use
in recovery of gas and oil from subterranean
formations.
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Claims

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The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. A polymer selected from the group
consisting of (A), (B), (C), and (D) wherein; (A) is
a cationic polymer of the general formula:
<IMG>
where R = H or CH3;
R' = a linear or branched alkylene radical
having from 2 to 10 carbon atoms;
R" = H or alkyl, linear or branched, having
from 1 to 3 carbon atoms;
R''' = an alkyl group, linear or branched,
having about 8 to about 25 carbon atoms,
aryl, alkaryl or aralkyl having from 6
to 18 carbon atoms;
Q = -NR- or -O-;
G = a residual unit derived from a
polyunsaturated monomer;
X? = a halogen ion (F, Cl, Br, I) or an alkyl
sulfate ion;
b = from about 10 to 99.9 mole percent;
c = from about 0 to 90 mole percent;
d = from 0.1 to about 10 mole percent; and
e = from 0 to 2 mole percent;
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(B) is an anionic polymer of the general formula;
<IMG>
(I)
where R = H or CH3;
R' = a linear or branched alkylene or arylene
radical having from 2 to 10 carbon
atoms;
M+ = H+, Na+, NH4+, or other
monovalent metal atom (Me+);
G = a unit derived from a polyunsaturated
monomer;
Q = a divalent radical -O- or -NR-;
R" = C8-C18 alkyl, C7-C24 aralkyl
or an ethoxylated C7-C24 aralkyl;
f = from about 10 to 60 mole percent;
h = from about 39.99 to 89.99 mole percent;
j = from 0.01 to 10 mole percent; and
k = from 0 to 2 mole percent;
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(C) is an amphoteric polymer of the general formula;
<IMG>
(D) is an amphoteric polymer of the general formula:
<IMG>
where A- ? = the residue of a cationic monomer;
B- ? = the residue of an anionic monomer;
C- ? - ? = the residue of a Zwitter-ion monomer;
R, R", Q and G are the same as previously
defined under (B);
m = 10-49.99 mole percent;
n = 10-49.99 mole percent;
p = 0.01-10 mole percent;
q = 0-80 mole percent;
r = 0-2 mole percent;
s = 5-99.99 mole percent;
t = 0-95 mole percent,
with the proviso that the sum thereof equals 100 mole
percent.
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2. A cationic polymer (A) as claimed in
claim 1 wherein:
R = H or CH3;
R' = a linear or branched alkylene radical
having from 2 to 4 carbon atoms;
R'' = H or alkyl, linear or branched, having
from 1 to 2 carbon atoms;
R''' = an alkyl group, linear or branched,
having from 8 to about 18 carbon atoms,
aryl, alkaryl or aralkyl having from 6
to 18 carbon atoms;
Q = -NR- or -O-;
G = a residual unit derived from a
polyunsaturated monomer;
X? = a halogen ion (F, Cl, Br, I) or an alkyl
sulfate ion;
b = from about 30 to 50 mole percent;
c = from about 50 to 70 mole percent;
d = from 0.1 to about 2 mole percent; and
e = from 0 to 0,5 mole percent.
3. An anionic polymer (B) as claimed in
claim 1 wherein:
R = H or CH3;
R' = a linear or branched alkylene radical
having from 2 to 4 carbon atoms;
M+ = H+, Na+ NH4+, or other
monovalent metal atom (Me+);
G = a unit derived from a polyunsaturated
monomer;
Q = a divalent radical -O- or -NR-;
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R" = C8-C18 alkyl, C7-C24 aralkyl
or an ethoxylated C7-C24 aralkyl;
f = from about 29 to 50 mole percent;
h = from about 49.9 to 79.9 mole percent;
j = from 0.1 to about 2 mole percent; and
k = from 0 to 0.5 mole percent.
4. An amphoteric polymer (C) as claimed in
claim 1 wherein:
A- ? - the residue of a cationic monomer;
B- ? - the residue of an anionic monomer;
R, R", Q and G are the same as previously
defined in claim 1;
m = 20-35 mole percent;
n = 20-35 mole percent;
p = 0.1-2 mole percent;
q = 30-60 mole percent;
r = 0-0.5 mole percent; and
with the proviso that the sum thereof equals 100 mole
percent.
5. An amphoteric polymer (D) as claimed in
claim 1 wherein:
C- ? - ? = the residue of a Zwitter-ion monomer; R,
R", Q and G are the same as previously defined
in claim 1;
p = 0.1-2 mole percent;
r = 0-0.5 mole percent;
s = 10-50 mole percent;
t = 50-90 mole percent; and
with the proviso that the sum thereof equals 100 mole
percent.
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6. A cationic polymer (A) as claimed in
claim 1 comprising (i) methacrylamidopropyl-tri-
methylammonium chloride; (ii) acrylamide and (iii)
methacrylamidopropyldimethyl-C8-16 alkyl-ammonium
chloride units.
7. A cationic polymer (A) as claimed in
claim 1 comprising (i) methacrylamidopropyl-tri-
methylammonium chloride; (ii) acrylamide, and (iii)
methacrylamidopropyldimethyl-n-stearyl-ammonium
chloride units.
8. A cationic polymer as claimed in claim
6 wherein component (iii) is methacrylamidopropyldi-
methylcetylammonium chloride units.
9. A cationic polymer as claimed in claim
6 wherein component (iii) is methacrylamidopropyldi-
methyl-n-dodecylammonium chloride units.
10. A cationic polymer as claimed in claim
1 comprising (i) methacrylamidopropyltrimethylammonium
chloride, (ii) acrylamide, (iii) methacrylamidopropyl-
dimethyl-n-dodecylammonium chloride and (iv)
ethyleneglycol dimethacrylate units.
11. An anionic polymer as claimed in claim
1 comprising (i) sodium 2-acrylamido-2-methylpropane
sulfonate, (ii) acrylamide and (iii)
N-decylacrylamide units.
12. An anionic polymer as claimed in claim
1 comprising (i) sodium 2-acrylamido-2-methylpropane
sulfonate, (ii) acrylamide, and (iii)
nonylphenoxypoly(ethyleneoxy)ethyl methacrylate units.
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13. An anionic polymer as claimed in claim
1 comprising (i) sodium 2-acrylamido-2-methylpropane
sulfonate, (ii) acrylamide, and (iii) N-benzylmeth-
acrylamide units.
14. An anionic polymer as claimed in claim
1 comprising (i) sodium 2-acrylamido-2-methylpropane
sulfonate, (ii) acrylamide, and (iii) N-t-butylmeth-
acrylamide units.
15. An anionic polymer as claimed in claim
1 comprising (i) sodium 2-acrylamido-2-methylpropane
sulfonate, (ii) acrylamide, (iii) N-decylacrylamide
and (iv) ethyleneglycol dimethacrylate units.
16. An anionic polymer as claimed in claim
1 comprising (i) sodium 2-acrylamido-2-methylpropane
sulfonate, (ii) acrylamide, (iii) N-decylacrylamide
and (iv) trimethylolpropane trimethacrylate units.
17. An amphoteric polymer as claimed in
claim 1 comprising (i) sodium 2-acrylamido-2-methyl-
propane sulfonate, (ii) dimethyldiallylammonium
chloride, (iii) acrylamide and (iv) nonylphenoxypoly-
(ethyleneoxy)ethylmethacrylate units.
18. A viscosified acidic composition
suitable for acidizing a porous subterranean
formation susceptible to attack by an acid,
comprising (i) water; (ii) from about 0.25 to 3
weight percent, based on the total weight of said
acidic composition of a polymer selected from the
group consisting of (A), (B), (C), and (D) wherein;
(A) is a cationic polymer of the general formula:
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<IMG>
where R = H or CH3;
R' = a linear or branched alkylene radical
having from 2 to 10 carbon atoms;
R" = H or alkyl, linear or branched, having
from 1 to 3 carbon atoms;
R''' = an alkyl group, linear or branched,
having about 8 to about 25 carbon atoms,
aryl, alkaryl or aralkyl having from 6
to 18 carbon atoms;
Q = -NR or -O-;
G = a residual unit derived from a
polyunsaturated monomer;
X? = a halogen ion (F, Cl, Br, I) or an alkyl
sulfate ion having 1 to 4 carbon atoms;
b = from about 10 to 100 mole percent;
c = from about 0 to 90 mole percent;
d = from 0 to about 10 mole percent; and
e = from 0 to 2 mole percent;
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(B) is an anionic polymer of the general formula;
<IMG>
(I)
where R = H or CH3;
R' = a linear or branched alkylene or arylene
radical having from 2 to 10 carbon
atoms;
M+ = H+, Na+, NH4+, or other
monovalent metal atom (Me+);
G = a unit derived from a polyunsaturated
monomer;
Q = a divalent radical -O- or -NR-;
R" = C8-C18 alkyl, C7-C24 aralkyl
or an ethoxylated C7-C24 aralkyl;
f = from about 10 to 60 mole percent;
h = from about 39.99 to 89.99 mole percent;
j = from 0.01 to 10 mole percent; and
k = from 0 to 2 mole percent;
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(C) is an amphoteric polymer of the general formula;
<IMG>
(D) is an amphoteric polymer of the general formula:
<IMG>
where A-? = the residue of a cationic monomer;
B-? = the residue of an anionic monomer;
C-?-?= the residue of a Zwitter-ion monomer;
R, R", Q and G are the same as previously
defined under (B);
m = 10-49.99 mole percent;
n = 10-49.99 mole percent;
p = 0.01-10 mole percent;
q = 0-80 mole percent;
r = 0-2 mole percent;
s = 5-99.99 mole percent;
t = 0-95 mole percent,
with the proviso that the sum thereof equals 100 mole
percent; and (iii) from 3 to about 28 weight percent
of acid.
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19. A viscosified acidic composition as
claimed in claim 18 wherein the concentration of
component (ii) is from 0.5 to 1.5 weight percent.
20. A viscosified acidic composition as
claimed in claim 18 wherein component (ii) is a
cationic polymer (A) wherein:
R = H or CH3;
R' = a linear or branched alkylene radical
having from 2 to 4 carbon atoms;
R" = H or alkyl, linear or branched, having
from 1 to 2 carbon atoms;
R''' = an alkyl group, linear or branched,
having from 8 to about 18 carbon atoms,
aryl, alkaryl or aralkyl having from 6
to 18 carbon atoms;
Q = -NR- or -O-;
G = a residual unit derived from a
polyunsaturated monomer;
X? = a halogen ion (F, Cl, Br, I) or an alkyl
sulfate ion having 1-4 carbon atoms;
b = from about 30 to 50 mole percent;
c = from about 50 to 70 mole percent;
d = from 0.1 to about 2 mole percent; and
e = from 0 to 0.5 mole percent.
21. A viscosified acidic composition as
claimed in claim 18 wherein component (ii) is an
anionic polymer (B) wherein:
R = H or CH3;
R' = a linear or branched alkylene radical
having from 2 to 4 carbon atoms;
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M+ = H+, Na+, NH4+, or other
monovalent metal atom (Me+);
G = a unit derived from a polyunsaturated
monomer;
Q = a divalent radical -O- or -NR-;
R" = C8-C18 alkyl, C7-C24 aralkyl
or an ethoxylated C7-C24 aralkyl;
f = from about 20 to 50 mole percent;
h = from about 49.9 to 79.9 mole percent;
j = from 0.1 to about 2 mole percent; and
k = from 0 to 0.5 mole percent.
22. A viscosified acidic composition as
claimed in claim 18 wherein component (ii) is an
amphoteric polymer (C) wherein:
A-? = the residue of a cationic monomer;
B-? = the residue of an anionic monomer;
R, R", Q and G are the same as previously
defined in claim 18;
m = 20-35 mole percent;
n = 20-35 mole percent;
p = 0.1-2 mole percent;
q - 30-60 mole percent;
r = 0-0.5 mole percent; and
with the proviso that the sum thereof equals 100 mole
percent.
23. A viscosified acidic composition as
claimed in claim 18 wherein component (ii) is an
amphoteric polymer (D) wherein:
C-?-? = the residue of a Zwitter-ion monomer; R,
R", Q and G are the name as previously defined
in claim 18;
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p = 0.1-2 mole percent;
r = 0 0.5 mole percent;
s = 10-50 mole percent;
t = 50-90 mole percent; and
with the proviso that the sum thereof equals 100 mole
percent.
24. A viscosified acidic composition as
claimed in claim 18 wherein the cationic polymer
comprises (i) methacrylamidopropyl-trimethylammonium
chloride; (ii) acrylamide and (iii) methacrylamido-
propyldimethyl-n-octyl-ammonium chloride units.
25. A viscosified acidic composition as
claimed in claim 18 wherein the cationic polymer
comprises (i) methacrylamidopropyl-trimethylammonium
chloride; (ii) acrylamide; and (iii) methacrylamido-
propyldimethyl-n-stearyl-ammonium chloride units.
26. A viscosified acidic composition as
claimed in claim 18 wherein the cationic polymer
comprises (i) methacrylamidopropyl-trimethylammonium
chloride; (ii) acrylamide; and (iii) methacrylamido-
propyldimethylcetylammonium chloride units.
27. A viscosified acidic composition as
claimed in claim 18 wherein the cationic polymer
comprises (i) methacrylamidopropyl-trimethylammonium
chloride; (ii) acrylamide; and (iii) methacrylamido-
propyldimethyl-n-dodecylammonium chloride units.
28. A viscosified acidic composition as
claimed in claim 18 wherein the cationic polymer
comprises (i) methacrylamidopropyltrimethylammonium
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chloride, (ii) acrylamide, (iii) methacrylamidopro-
pyldimethyl-n-dodecylammonium chloride and (iv)
ethyleneglycol dimethacrylate units.
29. A viscosified acidic composition as
claimed in claim 18 wherein the anionic polymer
comprises (i) sodium 2-acrylamido-2-methylpropane
sulfonate, (ii) acrylamide and (iii) N-decylacryl-
amide units.
30. A viscosified acidic composition as
claimed in claim 18 wherein the anionic polymer
comprises (i) sodium 2-acrylamido-2-methylpropane
sulfonate, (ii) acrylamide; and (iii) nonylphenoxy-
poly(ethyleneoxy)ethyl methacrylate units.
31. A viscosified acidic composition as
claimed in claim 18 wherein the anionic polymer
comprises (i) sodium 2-acrylamido-2-methylpropane
sulfonate, (ii) acrylamide; and (iii) N-benzyl-
methacrylamide units.
32. A viscosified acidic composition as
claimed in claim 18 wherein the anionic polymer
comprises (i) sodium 2-acrylamido-2-methylpropane
sulfonate, (ii) acrylamide; and (iii) N-t-butylmeth-
acrylamide units.
33. A viscosified acidic composition as
claimed in claim 18 wherein the anionic polymer
comprises (i) sodium 2-acrylamido-2-methylpropane
sulfonate, (ii) acrylamide, (iii) N-decylacrylamide
and (iv) ethyleneglycol dimethacrylate units.
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34. A viscosified composition as claimed in
claim 18 wherein the anionic polymer comprises (i)
sodium 2-acrylamido-2-methylpropane sulfonate, (ii)
acrylamide, (iii) N-decylacrylamide, and (iv)
trimethylolpropane trimethacrylate units.
35. A viscosified acidic composition as
claimed in claim 18 wherein the amphoteric polymer
comprises (i) sodium 2-acrylamido-2-methylpropane
sulfonate, (ii) dimethyldiallylammonium chloride,
(iii) acrylamide and (iv) nonylphenoxypoly(ethylene-
oxy)ethylmethacrylate units.
36. A viscosified acidic composition as
claimed in claim 18 wherein the cationic polymer
comprises (i) methacrylamidopropyltrimethylammonium
chloride, and (ii) acrylamide.
37. A viscosified acidic composition as
claimed in claim 36 wherein the cationic polymer
comprises (i) methacrylamidopropyltrimethylammonium
chloride and (ii) acrylamide; b = from 30 to 50 mole
percent and c = from 50 to 70 mole percent.
38. A viscosified acidic composition as
claimed in claim 18 wherein the concentration of acid
in the composition is an amount sufficient to have an
acidizing effect on the formation.
D-15387

Description

~L3C~
ACID ~ISCOSIFIER COMPOSITIONS
The use of polymeric compositions to thicken
or viscosify acid compositions is well known and
commonly practiced in the gas and oil recovery field.
Though many polymers are used, problems are often
encountered~ e~g., loss of viscosity of the acid
composition, precipitation of the polymer from
solution, degradation resulting from exposure to
elevated temperatures in the subterranean formation,
and sensitivity to calcium ions. The polymers of
this invention have been found to alleviate some of
the problems.
Canadian Patent No. 1,133,788, issued to K.
G. Phillips et al., on October 19, 1982, discloses
water-in-oil emulsions of MAPTAC and acrylamide
cationic polymers but does not disclose their use as
acid viscosifying agents.
U.S. Patent No. 3,943,966, issued to Lo J.
Guildbault on March 16, 1976, discloses use of
MAPTAC-containing polymers in cements.
U.S. Patent No. 4,022,731, issued to J. M.
Schmitt on May 10, 1977, discloses MAPTAC-AM polymers
but does not disclose use as an acid viscosifying
agent.
U.S. Patent No. 4,191,657, issued to B. L.
Swanson on March 4, 1980, discloses the use Or water
~,i."! dispersible polymers based on acrylamide or
methacrylamide, the hydrolyzed polymers thereof? the
crosslinked polymers thereof, the hydrolyzed
crosslinked polymers thereof, and copolymers thereof
with other monomers, in the production of acid
compositions suitable for matrix-acidizing or
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fracture-acidizing subterranean formations. However,
it nowhere discloses our claimed polymers~
U.S. Patent No. 4J452~940~ issued to M. R.
Rosen on June 5, 1984 and U.S. Patent No. 4~529,782,
issued to Y. L. ~an et al. on July 16t 1985, disclose
the producton of water-in-oil emulsions and water
soluble polymers. However, they do not disclose the
polymers of this invention nor their use in producing
viscosified acid compositions.
European Patent Application 0122073,
published on October 17, 1984, discloses a terpolymer
of acrylamide/sodium styrene sulfonate/methacryl-
amidopropyltrimethylammonium chloride and its use in
drilling muds having a basio pH of about 10 to 10.5.
Not only are the polymers different than those of
this invention, but it is not concerned with highly
acidic viscosified acid compositions.
The cationic, anionic and amphoteric
polymers of this invention are essentially water
soluble and can be used to prepare viscosified acid
compositions having improved properties.
T~E INVENTION
_
This invention is directed to polymers
useful as viscosifying agents to thicken acid
solutions that are employed in gas and oil well
acidizing operations. The polymers are those
cationic polymers (Group A), anionic polymers (Group
B) and amphoteric polymers (Group C) hereinafter
defined.
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Acid treating or acidizing of porous
subterranean formations is an accepted procedure for
increasing the yield and/or production of fluids from
the well, be they liquid or gaseous. These
procedures are so well known and so extensively
practiced that detailed explanation is neither
necessary nor o~ assistance to one of ordinary skill
in this field. Suffice it to say it is an
internationally practiced procedure to acid treat
wells and the patent and related published technical
literature is replete with material detailing the
procedure.
Though there is an abundance of published
material and commercial compositions available, the
industry is continuously looking for improvements.
Among the problems that still exist are inadequate
penetration of the acid into the formation, fluid
loss in the more porous ~ones of the formation and
leak-off at the fracture faces1 any one of which may
have a deleterious effect on the well's production.
Among the attempts ~hat have been made to resolve
some of these problems has been the addition of
various polymeric thickening agents. These agents
seem to thicken the acid solution and increase its
viscosity and in many instances the higher viscosity
or thickened acid solutions have reduced fluid loss
properties. In this regard attention is directed to
U.S. Patent No. 3,415,319 (B. L. Gibson) and U.S.
Patent No. 3,434,971 (B. L. Atkins). It has also
been indicated that these thickened acid solutions
show a lesser reaction rate with the acid-soluble
portions of the formation. In this regard attention
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is directed to U.S. Patent No. 3,749,169 (J. F.
Tate), U.S. Patent No. 3,236,305 (C. F. Parks) and
U.S. Patent No. 3,252,904 (N. F. Carpanter).
The higher viscosities additionally have an
advantage in fracture-acîdizing operations because
these thicker and more viscous acid solutions produce
longer and wider fractures. They are also more
effective in carring propping agents into the
formation when they are employed.
A problem existing in acidizing operations
is the instability of the viscosifier in the acid
solution to heat. This problem can be particularly
troublesome when using acidizing solutions that
contain thickening or viscosifying agents. Stability
to heat, the retention of the increased or higher
viscosity properties of the acidizing mixture under
the conditions existing in the well or formation is
important. The most satisfactory acidizing mixtures
or compositions are those which are sufficiently
stable to resist degradation by the heat in the well
and, particularly, in the formation for a period of
time sufficient to accomplish the intended purposes
of good penetration andtor significant etching of the
formation. The degree of stability will vary from
one formation to another, as is known, and is
dependent on many factors present during the
operation. For instance the siæe and depth of the
well, the type of subterranean formation present, the
concentration of the acid in the acidizing solution,
the temperature conditions existing throughout the
well bore and the formation, etc. All of these
factors as well as many others are known to affect
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the stability of the acidizing solution with the
temperature, which can be as high as 4000F or more,
having a pronounced effect and is considered one of
the most important operating variables when
considering stabiliSy. Increased temperature not
only hastens degradation with resultant decrease in
viscosity but also increases the rate o~ reaction of
the acid in the formation resulting in treatment of a
smaller area of the formation; both being
undesireable. Thermal degradation must be
distinguished from loss of viscosity (thermal
thinning) due to increased temperature, also a common
phenomenon.
The present invention generally alleviates
several of the problems discussed and provides
polymers useful for the production of thickened or
, viscosified acid solutions, and new thickened or
j viscosified acid solutions containing said polymers.
The following glossary is presented to
facilitate an understanding of the designations used
to identify the various compounds:
MAPTAC - methacrylamidopropyltrimethylammonium
chloride
MAPDMOAC - methacrylamidopropyldimethyl-n-octyl-
ammonium chloride
MAPDMDAC - methacrylamidopropyldimethyl-n-dodecyl-
ammonium chloride
MAPDMCAC - methacrylylamidopropyldimethylcetyl-
ammonium chloride
AM - acrylamide
MAM ~ methacrylamide
NAM - N-methylacrylamide
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~ 3
NND~AM - N,N-dimethylacrylamide
DMAPA - dimethylaminopropylmethacrylamide
~aAMP ~ - s~dium 2-acrylamido-2-methylpr~pane
sulfonate
NPPE~, ~ n~nylphenoxyp~ly(ethyleneoxy)ethylmeth-
acrylate
DMDAAC - dimethyldiallylammonium ~hl~ride
SPP - N~(3-sulropropyl)~ ethacrylamid~propyl-
- N,N-dimethyl ammonium betain
YAZO 33~ - 2,2'-az~b-is(2,4-dimethyl-4~methoxy
valeronitrile)
VAZO 52~ - 2,2'-azobis(294-di~ethyl valeronitrile)
TERGITOL ~P10~ - 10 mole ethoxylate of nonylphenol
VERSO~X 80a - pentasodium salt of diethylene-
triamine pentaacetic acid
Santonox R~ - a phenolic thioether
Ionol~ - di-t-butyl-p-cresol
Isopar M6 _ hydrooarbon oil
The Group A ca:ionic polymers ar~ the
polymers presented ~y Generic Formula A. They are
produced by polymerizing monomer ~i) alone or in`
com~ination with one or ~ore ~S the ~onomers (ii),
(iii) and/or (iv):
(i) an acrylamidoalkyltrialkylammonium halide or a
~ethacrylamidoalkyltrialkylammonium halide;
(ii) acrylamide, an N-alkylacrylamide or an
N,N-dialkylacryla~ide;
(iii) a hydrophobic acrylamidoalkYltrialkYlammonium
- halide or ~e~hacrylamidoalkyltr~alkylammonium
halide dirSere~t than that ~hich ~as used as
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monomer (i); as (iii) is defined in Generic
Formula A; and
(iv) a polyunsaturated monomer.
The cationic polymers of this group appear
to perform well in the laboratory under acidizing
conditions usually encountered in the field. They
exhibit good solubility and stability in acid
- solutions at only moderate cationic levels, they
exhibit good viscosity retention after thermal aging
in acid, they are capable of forming very high
molecular weight polymers thus giving rise to high
viscosif`ying efficiencies, the polymers containing
the polyunsaturated monomer modifier in the molecule
often exhibit improved thermal thinning behavior over
the corresponding unmodified versions, and they are
compatible with other cationic additives generally
used in the field. Those containing the hydrophobe
(iii) and/or polyunsaturated monomer (iv) are novel
polymers.
GENERIC FORMULA A
R R R
~CH2-C~fcH2-c~cH2_c~G~
- C =O C =O C -O
s Q N Q
/ ~ l
R' R R R'
1~
R"-N-R" R"-N-R"
X~ I X~
R" R"'
!
I
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8 --
where R = H or CH3;
R~ = a linear or branched alkylene radical
having ~rom 2 to 10 carbon ato~s,
pre~erably from 2 to 6 carbon atoms,
most prererably from 2 to 4 ¢arbon
atoms;
R" - H or alkyl, llnear or branched, having
- from 1 to 3 carbon atoms, preferably
from 1 to 2 carbon atoms;
R"' ~ an alkyl groupt linear or branched,
having about 8 to about 25 carbon atoms,
preferably from 4 to 18 carbon ~toms;
aryl, alkaryl or aralkyl having from 6
to lB carbon atoms;
Q = -NR- or -0-;
G = a residual unit derived from a
polyunsaturated monomer;
X~ - a halogen ion (F, Cl, Br1 I) or a
methyl sulfate ion;
b _ from about 10 to 100 mole percent,
preferably from 20 to 50 mole perc~nt,
most pre~erably ~rom 30 to 50 mole
percent; ~ith the proviso that (b) i~
not more than 9g.9DS when (d) is greater
than zero
c - ~rom about O to 90 ~ole percent,
preferably from 50 to 80 ~ole percent,
most prererably from 50 to 70 mole
percent;
d ~ from O to about 10 ~ole percent,
pre~erably rrom 0.1 to about 2 ~le
peroent; and
e ~ rrom O ~o 2 ~ole p~rcent, preferably
~ro= O te 0~5 ~ole percentO
~_153B7
.
; . .
i ~ 1 ,
r ~ !,

~L3~)2~3
g
Illustrative type (i) water-soluble monomers
include methacrylamidopropyltrimethylammonium
chloride ? methacrylamidopropyltrimethylammonium
~ethylsulfate, methacrylamidopropylhydroxyethyl-
dimethylammonium acetate, methacrylamidopropyli~o-
propylammonium chloride, methacryloyllethyltrimethyl-
ammonium chloride, acryloylethyltrimethylammonium
chloride~ methacryloylethyltrimethylammonium
methylsulfate, acrylolethyldimethylethylammonium
ethylsulfate and the like.
Illustrative type (ii) monomers include
acrylamide, N-methylacrylamide and dimethylacryl-
amide, alpha-methyl acrylamide, alpha-methyl-N-
methylacrylamide, alpha-methyl-N,N-dimethylacryl-
amide.
Illustrative type (iii) hydrophobic ~onomers
include methacrylamidopropyldimethyl-n-octylammonium
chloride, methacrylamido-propyldimethyl-n-dodecyl
ammonium chloride, me~hacrylamidopropyldimethyl_
cetylammonium chloride, methacryoylethyldimethyl-
octylam~onium chloride, methacryloylethyldimethyl-
cetylammonium chloride, acryloylethyldimethyldodecyl-
ammonium chloride, acryloylethyldimethyloctylammonium
chloride, methacrylamidopropyldi~ethylhexylammonium
chloride, methacryloylethyldimethylstearylammonium
chloride and the like.
Illustrative type (iv) monomers include
ethylene glycol diacrylate, diethylene glycol
diacrylate, propylene glycol diacrylate, ethylene
glycvl dimethacrylate, diethylene glycol
dimethacrylate, diurethane di~ethacrylate,
I)_15387

~2~3
-- 1 o --
1,4-butandiol dimethacrylate, polyglycol-400 dimeth-
acrylate, neopentyl glycol dimethacrylate, triethyl-
ene glycol dimethacrylate, N,N'-isovalerylidene-bis
methacrylamide, N,N'-methylene-bis-methacrylamide and
the like.
These Group A Cationic Polymers pos~sess good
solubility, can be made to have high molecular
~ weights and can be used over a wide temperature range
in viscosified acid solutions in subterranean
formations.
The Group B Anionic Polymers
The Group B anionic polymers are the
copolymers represented by Generic Formula B. They
are produced by copolymerizing three or more of the
~ monomers:
:~ (i) an acrylamidoalkyl sulfonic acid or a
methacrylamidoalkyl sulfonic acid or the salts
thereof;
t (ii) acrylamide, N-alkylacrylamide or
N,N-dialkylacrylamide;
(iii) a hydrophobic acrylic acid ester or methacrylic
acid ester or acrylamidohydrocarbyl wherein the
hydrocarbyl group is as defined by R" in
Generic Formula B; and
(iv) a polyunsaturated monomer.
D-15387

~;~1)2~4D3
GENERIC FORMULA ~
R R R
~CH2-C~cH2_c~cH2_c - ~G~
I f \ I /h I i ~ / k
C=O C=O C=û
Q N Q
/ \
R' R R R"
SO 3M
(I)
where R = H or CH3;
R' = a linear or branched alkylene or arylene
radioal having from 2 to 10 carbon
atoms, preferably from 2 to 6 carbon
atoms, most preferably from 2 to 4
carbon atoms;
M~ = H+, Na+, NH4~, or other
j monovalent metal atom (Mef);
G = a unit derived from a polyunsaturated
monomer;
Q = a divalent radical such as -O-, -NR-;
R" = C4-C1g alkyl, C7-C24 aralkyl
or an ethoxylated C7-C24 aralkyl;
f = from about 10 to 60 mole percent,
preferably from 20 to 50 mole percent;
h = from about 39.99 to 89.99 mole percent,
preferably from 49.9 to 79.9 mole
percent;
j = from 0.01 to 10 mole percent, preferably
from 0.1 to about 2 mole percent; and
k = from O to 2 mole percent, preferably
from 0.1 to 0.5 mole percent.
D-15387

- 12 -
Illustrative type (i) monomers include
sodium 2-acryla~ido-2-methylpropane sul~onate, sodium
2-acrylamidoethane sulfonate, potassium 3~methacryl-
amidopropane sulfonate, ammonium p-acrylamidobenzene-
sulfonate, potassium 6-acrylamidonaphthalene
sulfonate, disodium 4-methacrylamidobenzenedisul-
fonate-1,3, tripotassium 3-acrylamidonaphthalene
trisulfonate-1,5,6~ and the like.
Illustrative type (ii) monomers include
acrylamide, N-methylacrylamide, N,N-dimethylacryl-
amide, alpha-methylacrylamide, alpha-methyl-N-meth-
acrylamide, alpha-methyl-N,N-dimethy;acrylamide.
Illustrative type ~iii) hydrophobic monomers
include N-butylacrylamide, N-t-butyl-acrylamide,
N-decylacrylamide, N-stearylacrylamide, the N-pentyl-
acrylamides, N-butylmethacrylamide, N-decylmethacryl-
amide, N-benzylacrylamide, N-tolylacrylamide,
N-benzylmethacrylamide, N-tolylmethacrylamide,
N-t-butylmethacrylamide, the butyl acrylates, the
decyl acrylates, phenyl acrylate, tolyl acrylate,
t-butyl methacrylate, octyl methacrylate, phenyl
methacrylate, nonylphenoxypoly(ethyleneoxy)ethylmeth-
acrylate, and the like.
Illustrative type (iv) polyunsaturated
monomers include ethylene glycol diacrylate,
diethylene glycol diacrylate, propylene glycol
diacrylate, ethylene glycol dimethacrylate,
diethylene glycol dimethacrylate, diurethane
dimethacrylate, 1,4-butandiol dimethacrylate,
polyglycol-400 dimethacrylate, neopentylglycol
dimethacrylate, triethyleneglycoldimethacrylate,
N,N'-isovalerylidene-bis-methacrylamide,
N,N'~methylene-bis-methylacrylamide, and the like.
D-15387

It was unexpected and unpredictable to
discover that the viscosifying ability of the Group B
Anionic Polymers was enhanced rather than impaired by
the incorporation of the hydrophobic component and
that even a weak hydrophobe, such as a C4-al~yl
moiety benefited the acid-solution viscosity. These
polymers also exhibited good solubility in acid.
Applicants do not intend to be bound by the
above theoretical explanation. The viscosifying
ability of the hydrophobe-modified anionic polymers
was found to be better than the counterpart
hydrophobe free polymer. Theoretically this may be
explained as being caused by an association of the
hydrophobe group.
,,
The Group C Amphoteric Polymers
The Group G amphoteric polymers are those
represented by Generic Formulas C and D. These poly-
ampholyte copolymers are particularly useful acid
viscosifiers in acid solutions used where a high
degree of tolerance to calcium ions is required.
During the course of an acidizing operation an
increasingly higher concentration of calcium chloride
generally forms due to the reaction of hydrochloric
acid with limestone or dolemite formations. The
presence of high concentrations of calcium ions is
usually detrimental to the stability of many poly-
electrolytes leading to either a loss of solution
1 viscosity or polymer precipitation or both. We have
found these polyampholytes provide the required solu-
bility and stability in acid solution and as shown in
the data below are stable in the presence of calcium.
D-15387

- 14 -
The Generic Formula C polymers are produced
by copolymerizing three or more of the monomers;
(i) a cationic polymerizable monomer;
(ii) an anionic polymerizable monomer;
(iii) a hydrophobic acrylic acid ester or methacrylic
acid ester or acrylamidohydrocarbyl wherein the
hydrocarbyl group is as defined by R";
~ (iv) acrylamide; and
(v) a polyunsaturated monomer.
The Generic Formula D polymers are produced
by copolymerizing at least three of the monomers;
(i) a Zwitter-ion polymerizable monomer;
(ii) a hydrophobic acrylic acid ester or methacrylic
acid ester or acrylamidohydrocarbyl wherein the
hydrocarbyl group i9 as de~ined by R";
(iii) acrylamide; and
(iv) a polyunsaturated monomer.
l GENERIC FORMULA C
,
R R
A ~ 1 B ~ CH2-C ~ CH2-C ~ G t
\ ¦ /m \ ¦ n\ I P\ I q r
~9 ~3 C=O C=O
Q N
/ \
R" R R
GENERIC FORMULA D
_
R R
~ C ~ CH2-C ~ CH2-C _ ~ G
- ~ C=O C-O
Q N
R" R R
D 15387

where A- ~ = the residue of a cationic monomer;
B- 0 = the residue of an anionic monomer;
C- ~ - 0 = the residue of a Zwitter-ion monomer;
R, R'l, Q and G are the same as previously
defined from Generic Formula B;
m = 10-49.99 mole percent; prePerably 20-35
mole percent;
n = 10-49.99 mole percent, preferably 20-35
mole percent;
p = 0.01-10 mole percent; preferably 0.1-2 mole
percent;
q = 0-80 mole percent, preferably 30-60 mole
percent;
r - 0-2 mole percent, preferably 0-0.5 mole
percent;
s = 5-99.99 mole percent, preferably 10-50 mole
percent; and
,~ t = 0-95 mole percent, preferably 50-90 mole
percent
with the previso that the sum thereof equals 100 mole
percent.
Of course one can use a mixture oP A-0, B-
~and C~ type monomers in a single copolymer and
this is considered with the scope of our claimed
invention. In such instances, the copolymers can be
represented by the following formula wherein the
variable x is modified to produce an appropriate
viscosifying agent.
R R
~A~1B- ~ LC~CH2_C~CH2C~G~
\ I Jx \ I lx \ I ~x l /x I x ~x
~3 9 ~ C=O 1=0
Q N
R'l R R
D- 1 5387

~3~ 3
- 16 -
The cationic, anionic and Zwitter ionmonomers are well known to the ordinary skilled
polymer chemist; any suitable monomer can be used.
Illustrative suitable cationic polymerizable
monomers include dimethyldiallylammonium chloride,
methacryloylethyl trimethylammonium chloride,
acryloylethyl trimethylammonium methylsulfate,
methacryloylethyldimethylethylammonium ethyl sulfate,
methacrylamidopropyltrimethylammonium chloride,
vinylmethylpyridinium chloride, and the like.
Illustrative suitable anionic polymerizable
monomers include sodium 2-acrylamido-2-methylpropane
sulfonic acid, sodium acrylate, potassium
methacrylate, sodium 2-acrylamidoethane sulfonate,
potassium 3-methacrylamidopropane sulfonate, and the
like.
The cationic and anionic monomers may be
present in the form of an ion-pair such that no other
counter ions are present. The ion-pair monomers
! would enter the polymerization as if they were a
' single entity. Illustrative ion-pair monomers
include dimethylaminopropylmethacrylamide, and
2-acrylamido 2-methylpropane sulfonic acid and the
like.
; Illustrative suitable Zwitter-ion polymerizable
monomers include N-(3-sulfopropyl)-N-methacrylamido-
propyl-N,N-dimethyl ammonium betain, N-(3~sulfo-
propyl)-N-methacryloxyethyl-N,N-dimethylammonium
~ betain 7 and the like.
! The suitable hydrophobic monomers and
polyunsaturated monomers are those set forth as
illustrative for types ~iii) and (iv) for Generic
D-15387

~3~ 33
7 -
Formula B. Illustrative type (iii) hydrophobic
monomers include N-butylacrylamide, N-t-butylacryl-
amide~ N-decylacrylamide, N-stearylacrylamide, the
N-pentylacrylamides, N-butylmethacrylamide, N-decyl-
methacryla~ide, N-benzylacrylamide, N-tolylacryl-
amide, N-benzylmethacrylamide, N-tolyl~ethacrylamide,
N-t-butylmethacrylamide~ the butyl acrylates, the
decyl acrylates, phenyl acrylate, tolyl acrylate,
t-butyl methacrylate, octyl methacrylate, phenyl
methacrylate, nonylphenoxypoly(ethyleneoxy)ethylmeth-
acrylate. Illustrative type (iv) monomers include
ethylene glycol diacrylate, diethylene glycol
diacrylate, propylene glycol diacrylate, ethylene
glycol dimethacrylate, diethylene glycol dimethacryl-
ate, diurethane di~ethacrylate, 1,4-butandiol dimeth-
acrylate, polyglycol-400 dimethacrylate, neopentyl
glycol dimethacrylate, triethylene glycol dimeth-
acrylate, N,N'-isovalerylidene-bis-methacrylamide,
N,N'-methylene-bis-methacr~lamide, and the like.
It is recognized that small amounts of other
polymerizable monomers can be present in any polymer
discussed above.
The polymerization reactions for producing the
above polymers can be carried out using any of the
methods known in the art. For example as disclosed
in U.S. Patent No. 4,191,657 (B. L. Swanson), U.S.
Patent No. 4,452,940 (M. R~ Rosen), U.S. Patent No.
4,485,209 (Y. L. Fan et al.), U.S. Patent No.
4,529,782 (Y. L. Fan et al.) and South African Patent
No. 84-01784 (Y. L. Fan et al.). The preferred
method, however, is that which was used to produce
the polymers in the examples.
i
D-15387

~3~ 3
18 -
In a typical polymerization process the method
comprises;
ta) combining the monomers, an oil soluble
surfactant, water and hydrophobic- liquid ~edium
in the conventional manner;
(b) homogenizing the mixture from (a) to form a
water-in-oil emulsion;
(c) deoxygenating the emulsion from ~b);
(d) adding initiator(s) to the deoxygenatd emulsion
from (c);
(e) heating and stirring the mixture from (d) under
polymerization conditions so as to form a
water-in-oil polymer emulsion; and
(f) recovering the polymer in whatever physical form
desired.
In this procedure, the aqueous phase generally
comprises from about 60 weight percent to about 85
weight percent, preferably from about 70 weight
percent to about 80 weight percent, of the total
composition .
The hydrophobic medium suitable fGr use in ~his
invention includes benzene, xylene, toluene, mineral
oils, petroleum and mixtures~ hereof. A preferred
hydrophobic medium is Isopar'~h~ Any oil-soluble
surfactant that supports a water-in-oil emulsion and
does not have an unduly harmful e~fect on the
polymerization reaction can be used. The pre~erred
surractant3 are those ha~ing a Hydrophile-Lipophile
Balance (HLB) of ~rom about 1 to about 10, pre~erably
rrom about 2 to about 6. These ~urfactants are well
known and include She fatty acid ester~, and aq
D-15387

~L3~2~3
~ g
sorbitan monolaurate, sorbit n monostearate, sorbitan
monooleate, sorbitan trioleate; mono- and diglycer-
ides, such as those obtained from the glycerolysis of
edible ~ats; polyoxyethyleneated fatty acid e~ters,
such as polyoxyethylene-(4)-sorbiSan monostearate;
polyoxyethyleneated linear alcohols, such as
TERGITOL$ 15-S~3 and SERGITOL0 ~25=L-3; polyoxyethyl-
ene sorbitol esters, such as polyoxyethylene sorbitol
beeswax derivatives; polyoxyethyleneated alcohols,
such as polyoxyethylene-(2)-c ~ l ether; polyester
ether copolymers (e.g. Rapiso -246, ICI); and the
like, or mixtures thereof.
Any of the known free radical initiators can
be used at catalytic amounts sufficient to carry out
the polymeri~ation, generally from about 0.05 to
about 0.5, preferably from about 0.1 to about 0.25
weight percent, based on the weight of monomers
charged. The initiator can be added directly or
diluted with solvent and can be incrementally added
during the course of the reaction if desired.
Illustrative initiators include the peroxides, such
as t butyl hydroperoxide, t-butyl perbenzoate,
benzoyl peroxide, ammonium persulfate, cumene f~
hydr~ eroxide~the azo compounds, such as VA~0~ 3,
VA~0~ 2, VAZ0~4; redox catalysts; and others known
to those of ordinary skill in the art.
The polymerization is carried out at a
temperature ~rom about 30C to about 800C, preferably
from about 40C to about 600C. The time will vary
depending upon the particular reactants being
employed, the temperature, the size of the batch and
other corditions pr~valent during the poly~eri2ation.
Normally cooling ~ r~quired.
Do15387
.~ .

~3~2 [)~3
_ 20 -
The pressure is not critical and can be
subatmospheric, atmospheric or superatmospheric. The
polymerization i5 preferably carried out under an
lnert atmosphere. However, at times, small
quantities of air or oxygen may be ~parged into t~e
reaction mixture to assist in controlling the
polymerization reaction rate; the amount of dissolved
oxygen in the aqueous pha~e is usually less than
about 1 part per million.
After the polymerization is complete, an
antioxidant, or any other desired additive, can be
added to the reaction mass, generally in an amount of
from about 0.05 to about 5 parts per hundred parts of
resin. Any organic antioxidant suitable for the
product can be used; it is generally added in the
form o~ a solution in a suitable solvent. Suit~ble
antioxidants include substituted phenols, such as
Ionol; thiobisphenols, such as Santonox R~;
hydroquinone derivatives, ~uch as the monomethyl
ether of hydroquinone; benzothiazole; ammonium or
sodium thiosulfate; alkaline metal thiocyanates;
aminocarboxylic acids; or any of the other
antioxidants known to those skilled in the art~
An inverting sur~actant, e.g. TERGITO~NP10,
may be added to the water in-oil emulsion at the
conclusion of the reaction. The surfactants which
may be used include polyoxyethylene alkyl phenol,
polyoxyethylene (10 mole) cetyl ether, polyoxyethyl-
ene alkyl-aryl ether1 quaternary ammonium
derivatives, potassium oleate, N-cetyl N-ethyl
~orpholinium ethosul~ate, sodium lauryl ~ulfate,
condensation productg ~r higher fatty alcohol~ with
D-1~387
. ," .

)3
- 21 -
ethylene oxide, such as the reaction product of oleyl
alcohol with 10 ethylene oxide units; condensation
products of alkylphenols and ethylene oxide, such as
the reaction products of isooctylphenol with 12
ethylene oxide units; condensation products of higher
fatty acid amines with five, or more, ethylene oxide
units; ethylene oxide condensation products of
polyhydric alcohol partial higher fatty esters, and
their inner anhydrides (mannitolanhydride, called
Mannitan, and sorbitol-anhydride, called Sorbitan).
The preferred surfactants are ethoxylated nonyl
phenols, ethoxylated nonyl phenol formaldehyde
resins, and the like.
The inverting surfactant is used in amounts
of from about 0.1 to about 20, preferably from about
1 to about 10 parts per one hundred parts of the
polymer.
The water-in-oil emulsion containing the
inverting surfactant is solubilized or inverted in
the presence of water. The polymer-containing
emulsion releases the polymer in the aqueous solution
in a very short period of time.
The polymers of this invention have reduced
viscosity of from about 1 dl/g to about 20 dl/g~
preferably from about 3 dl/g to about 15 dl/g in 1N
NaCl solution at 25C.
The acidizing solutions generally are based
on aqueous hydrochloric acid. The acid concentration
usually varies from about 3 to about 2~ weight
percent ~Cl. The amount of viscosifying agent of
this invention present in the acidizing solution will
depend upon the viscosity desired. Suitable polymer
D-15387

~L3~ 3
- 22 -
concentrations are from about 0.25 to about 3 weight
percent of the acidizing solution. Commonly about
0.5 to 1.5 weight percent is employed. The
preparation of the~e solutions is well known to one
of ordinary skill in this art and can contaln any of
the additives normally and conventionally uqed in
this art. Any of the other commonly used acids oan
be employed, e.g., hydrofluoric acid, formic acid,
acetic acid, etc., as is known in the art, as well as
mixtures. It is also known that higher concentra-
tions of the acid can be used and these are within
the scope of our invention. Any concen~ration of
acidizing acid adequate to have an acidizing effect
in the formation can be used.
The following examples serve to give
specific illustrations of this invention but they are
not intended in any way to limit the scope of this
invention.
Example 1
Into a one-liter pyrex~ lass reactor,
equipped with a turbine agitator, thermometer,
addition funnel, condenser, nitrogen inlet and
outlet, and an external heating or cooling bath,
there was charged 704 g of a monomeric ~ater-in~oil
emulsion. The latter was prepared by emulsifying an
aqueouQ solution that consisted of 245.2 g of a 50S
aqueous solution of ~MAPTAC) methacrylamidopropyltri-
~ethyla~moniu~ chloride, 184.4 g of a 50~ aqueous
solution of (AM) acryla~ide, ~ 6 B g of deionized
water, and 0.17 g o~ Versenex~0 with an oil olution
consisting of 157.9 g of Isopar~ oil and 9~ g of
D~153B7

~ 3
- 23 -
Span 80~ (sorbitan mon~oleate). The monomeric
emulsion was deaerated by sparging with nitrogen for
30 m~nutes. Thereafter, an i ~tiator solution
consisting of 0.012 g of VAZO ~ 3 and 1.5 g Or sylene
was introduced. The reactor was heated to 50DC with
the external heating bath. ~nce the polymerization
initiated, an external cooling bath was employed and
the polymerization temperature was maintained at 50
2~C. In the meantime, a second initiator solution
consisted of 0.18 g of VAZ~ 2 and 7.5 g of xylene
was added in six equal portions with a 10 minute
interval between addltions. Upon completing the
addition of the second initiator1 the polymerization
mixture was heated for an additional 4 hours at 50 +
2C. At the end of polymerization, the reactor was
cooled t~ room temperature and a solution of 0.2 g of
Santonox~ in 2.5 g of xylene together with 10.7 g of
TERGITOL~ P10 was added to the mixture. The ~inished
polymeric emulsion was milky white in appearance and
exhibited a Brookfield viscosity of 1560 cps (Model
HBT, 10 rpm at 25C). The recovered polymer
possessed a reduced viscosity in 1N NaCl solution of
9,7 dlJg.
Examples 2-9
Using the equip~ent and procedure described
in Example 1, a series of (MAPTAC-AM) copolymers
having different degrees o~ ionic characters was
prepared. The compositions and general characteris-
tics of these polymers are listed in Table I. For
completion; data for Example 1 is also ~rcluded.
D-15387

3 ~ 3
- 24 ~
TABLE I
CATIONIC POLYMERS DERIVED FR M MAPTAC
Composition, Mole ~ RV1 3~ Solution2
Example MAPTAC AM dl/g ViscosityL cps
2 17.6 82046.2 4650
3 20 80 10.4 7550
4 25 75 11.0 7250
- 1 30 7Q 9.7 5450
9.5 5800
6 40 60 7.9 2850
7 40 60 9.1 5800
8 50 50 7.6 3160
9 100 - 1.1 low
1) Measured in lN NaCl solution at 25C,
C = 0.0126 g/dl.
2) Measured in distilled water, Brookfield Viscometer
Model L.VT, 0.6 rpm, at 25C.
Example 10
This example illustrates a general procedure
for the preparation of a hydrophobe-modified
cationic monomer using an alkylating agent. Into a
100-ml, 3~necked pyrex flask, equipped with a
mechanic stirrer, thermometer, condenser, addition
funnel and an external cooling bath, there was
charged 34.7 g of the amino monomer, dimethylamino-
propylmethacrylamide (DMAPMA). The flask was cooled
to about 10C with the cooling bath, and 29.9 g of
n-octyl chloride was added in a dropwise manner over
a one-hour period. The reaction mixture was stirred
for another hour at room temperature. The product,
methacrylamidopropyldimethyl-n-octylammonium
chloride, was used for polymerization without further
purification.
D-15387

2~)3
25 --
Using the equipment and procedures described
in Example 10 and the appropriate molar quantities of
reactants, two additional hydrophobe modi~ied
cationic monomers were prepared. The results of
Examples 10 to 12 are summarized in Table II.
TABLE II
HYDROPHOBE-MODIFIED CATIONIC MONOMERS
Example Amino Alkylating
Number ~ ABent _
1 O DMAPMA n-octyl methacrylamidopropyl-
chloride dimethyl-n-octyl-
ammonium chloride
11 DMAPMA n-dodecyl methacrylamidopropyl-
chloride dimethyl-n-dodecyl-
am~onium chloride
12 DMAPMA cetyl methacrylamidopropyl-
chloride dimethylcetylammonium-
chloride
Example 13
A polymer was prepared using the equipment
and procedure described in Example 1 with the
exception that the agueous solution was composed of
24~.3 g of a 50g aqueous solution of MAPTAC, 185.7 g
of a 50S a~ueous ~olution of acrylamide, 1.19 g of
methacrylamidopropyldimethyl-n-octylamm~n ~ ~ chloride
prepared in Example 10, 0.18 g of Versene~~~0, and
104.2 g of deicni~ed water. The finished polymeric
emulsion exhibited a Brook~ield ViQCosity o~ 1560 cps
(Model H~T, 10 rpm at 25C). The recovered polymer
pOSQ~S ed a reduced vi~cosity of 8.1 dl/g in lN NaCl
~olution at 25C.
D-15387
L~
.~s; .~ ~

~;~0;~ 33
- 26 -
Examples 14 and 15
Using the procedure described in Example 13,
a (MAPTAC-AM-methac,rylamidopropyldimethyl-n-dodecyl-
ammonium chloride) terpolymer and a (MAPTAC-AM-
methacrylamidopropyldimethylcetylammonium chloride)
terpolymer were prepared. The compositions and
general characteristics of the polymers are shown in
Table III.
TABLE III
HYDROPHOBE-MODIFIED CATIONIC MONOMERS
Example Compo~ M~le ~ RV2 O.3~ Solution3
Number Hydrophobel MAPTAC AM dl/~ Viscosity, cps
13 0.2 29.8 70 8.1 900
(Example 10)
: 14 0.2 29.8 70 8.42500
(Example 11)
0.2 29.8 70 8.6 950
(Example 12)
1) As indicated by the Example number
2) Measured in 1N NaCl solution at 25C,
C - 0.0125 g/dl.
3) Measured in distilled water at 25C with a
Brookfield Model LVT Viscometer at 0.6 rpm,
Example 16
A polymer was prepared using the equipment
and procedure described in Example 1 with the
exception that the aqueous solution was composed of
243.1 g of a 50~ aqueous solution of MAPTAC, 181.6 g
of a 50~ aqueous solution of acrylamide, 1.4 g of the
monomeric product prepared in Example 11, 1.1 g of
D-15387

~L3~2~03
~7
.
ethylene dimethacrylate, 0.18 ~ of ~er~enex ao, and
109.2 g of deionized water. The finished polymeric
emulsion was milky white in appearance and exhibited
a Brookfield viscosity o~ 3760 cps. The recovered
polymer possessed a reduced viscosity o~ 1.3 dl/g in
lN NaCl solution at 25C. This tetrapolymer
contained 0.3 mole ~ of the difuncti.or;al
monomer-ethylene glycol dimethacrylate.
Examples 17-26
The viscosifying efficiencies of these
polymers in 15~ aqueous HCl solution were measured
with a Fann 35 viscometer (Fann Instrument Co.,
Houston, Texas) at 300 rpm and 25C at a
concentration of 35 gallons of emulsion per 1000
gallons Or acid rluid tequivalent to 1.05~ by weight
of active polymer in the acid solution). The higher
the viscosity, the more efficient is the polymer.
For comparative purposes a commercially available
copolymer of acrylamide and sodium acrylate was
tested in the same manner (Control A). The improved
properties obtained with the viscosirying polymers of
this invention are clearly e~ident.
D-15387
J~
~ .,. ;),~

- 28 -
TAB
VISCOSIFYING EFFICIENCIES IN 15% HCl SOBUTION
Polymer Initial
oP Mole ~ Viscosity in
Example Example MAPTAC AM Other 15~ HCl, cps
_
17 2 17.6 82.4 - 51
1~ 3 20 80 - 82
19 4 25 75 - 71
1 30 70 - 64
21 5 35 65 - 59
22 6 40 60 - 49
23 8 50 50 - 56
24 13 29.8 70 0.2 42
14 29.8 70 0.2 42
26 15 29.8 70 Q.2 42
Control A 3
Examples 27-33
I'he thermal-thinning behavior, or viscosity
retention at elevated temperatures, of these polymers
was measured with a Fann 50 viscometer. The sample
was subjected to a constant shear rate of 170 sec 1
and was heated at a programmed rate of 12F/min.
Viscosity retention values at 225, 250 and 300F
were expressed in Table V as ~ of 100F viscosity. In
all cases studied, the polymers of the present
invention showed significantly greater viscosity
retentions at elevated temperatures when compared to
Control B. Control B used a commercially available
polacrylamide of the type employed by drillers.
D~15387

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D-1 5387

~ 30 -
Exa~ple 34
Into a one-liter pyrex glass reactor,
equipped with a turbine agitator, thermometer,
addition funnel, condenser, nitrogen inlet and
outlet, and an external heating or cooling bath,
there was charged 708 g of a water-in--oil monomers
emulsion. The latter was prepared by emulsifying,
with a Waring blender, an aqueous solution consisting
of 249.8 g of a 50S aqueous solution o~ sodium
2-acrylamido-2-methylpropane sulfor.ate (NaAMPS~
178.8 g of a 50S aqueous solution of acrylami(e (AM),
1.g g of N-decylacrylamide, 0.17 g of Ver~enex ~0 and
105.8 g of deionized water with an oil solution
comp~sed of 157.8 g of Isopar~ solvent and 14.2 g of
Span~ O surfactant (sorbitan monooleate). The
monomeric emulsion was deaerated by sparging with
nitrogen for 30 minutes. Thereafter,~n initiator
solution consisting of 0.012 g of VAZ ~ 3 (2,2'-
azobis-t2,4-di~ethyl-4-methoxy valeronitrile]) and
1.5 g of xylene was introduced. The reactor was
heated to 50C. Once the polymerization initiated,
an @xternal cooling bath was used to maintain the
reactor temperature at 50 ~ 2~C. In the meantime, a
second initiator solution, consisting of 0.18 g of
VA2 ~ 2 (2,2'-azobis-[2,4-dimethyl valeronitrile])
and 7.5 g of xylene, was added in six equal portions
with a 10-minute interval between additions. Upon
completion of the addition of She ~econd initiator,
the polymerization was heated for 4 more hours at 50
+ 2C. At the end of polymerization, the reactor was
cooled to room temperature and a ~olution of 0.1g g
Or Santonox~ in 2.5 g of xylene, together with
D-15387
,..~. ~,~ ,,

~3~ 3
~)
10.8 g of TERGITOL NP10 surfactant, was added to the
mixture. ~he finished polymeric emulsion was milky
white in appearance and exhibited a Brookfield
viscosity of 1200 cps (Model HBT, 10 rpm at 25C).
The recovered polymer showed a reduced vi~cosity of
10.8 dl/g in 1N NaCl solution at 25C,
Examples 35-40
Using the equipment and procedure described
in Example 34, six additional terpolymers containing
N decylacrylamide were prepared. The compositions
and general characteristics of these polymers are
listed in Table VI.
TABLE VI
ANIONIC_(NaAMP ~ M-NDAM) TERPOLYMERS
Example Mole ~1 RV2 0.3~ Solution3
_N!_ ~ ~ Vis~oslty, c~
69 1 10 . 3 9000
34 30 69.5 0.511.7 7950
36 30 69.9 0.111.B 8350
37 40 59 . 8 0 . 2 10 . 2 4000
38 50 49 1 8.6 1BOO
39 50 49.5 ~.5 8,8 1g50 '
49.8 0.2 9.7 3550
1) Monomer feed composition
2) Measured in lN NaCl ~olution at 25C,
C = 0.0125 g/dl.
3) Measured in distilled water at 25C using a
Brookfield Model LVT Viscometer at 0.6 rpm
and 25C.
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~ 32 ~
Examples 41-47
Using the equipment and procedure de~cribed
in Example 34, terpolymers containing dif~erent types
of hydrophobes were prepared. The compositions and
general characteristics of these polymers are listed
in Tabl~ VII. Also included in Table VII are two
(NaAMPS~ M) copolymer used as eontrols.
TABLE VII
ANIONIC (NaAMPS-AM-HYDROPHOBE) TERPOLYMERS
Example ~ Mole ~ RV2 0.3~ Solution3
No. ~ 1 dl/g Viscosity,_cps
41 30 69.9NPPEM 0.111.6 10800
42 30 69.~NPPEM 0.58.1 9050
43 30 6909NBMA 0.112.4 gOOO
44 30 69.~NBMA 0.511.4 9300
69NBMA 1.0 11.4 10750
46 30 69.9NTBMA 0~111.1 7050
47 30 69NTBMA 1.0 11.3 7850
Cont. C 40 60 -- 10.4 6400
Cont. D 30 70 -- 10.4 9900
1) NPPEM = Nonylphenoxypoly(ethyleneoxy)ethylmeth-
acrylate; NBMA = N-benzylmethacrylamide;
NTBMA _ N-t-butylmethacrylamide.
2) Measuned in 1N NaCl solution at 25DC,
C ~ 0~0125 g/dlo
3) Measured in distilled water at 25C using a
Brookfield Model LVT Yiscometer ~t 0.6 rpm
and 25C.
Using the equipment and procedures des~ribed
in Exa~ple 34, tetrapolymers containing bot~ a hydro-
phobic comonomer and a multi~unctional oomonomer were
prepared. The ~Gmposi~ions and general ~haract~ris-
tics b~ the e polymers are listed in Table YIII.
D-15387
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- 33 -
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O-- O O O O O O O t..... L
o O ts~ o t--t-- ~ E
_ ~ '-- E C~
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3 ¢) 3 ~a~ O
~ ~ _ o _ ~r . v O -I ~
--I O O
O :~
~ oEI ~ ~ I~ C
:~: C O O O O O O O O v N o
~_~ _l :~ O c11 o a~
a a c: a a a c~ a: o
X ~ c~ C ;~
c~ a~ o
DN N N N ., ~' N
SO O O C ~
e
a ~ a ~ ~ ~ ~ o L ~
O ~ :1: ~ O
E ~ N U~ C . Il) .C
3 3 3 3 3 3 ~ ~
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j~ O C:~ O O O ~I C E v
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K Z ,-- ~ r~ =r
387
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~3(~ 3
- 3~ -
Examples 55 60
__
The examples shown in Table IX illu trate
the benefit of incorporating a quitable poly~erizable
hydrophobe monomer into an anionic acid ~i~cos~f$er.
In all cases studied, the N-decylacrylamide-modified
polymers produced noticeably hiBher viscosities in
acid fluid than their corresponding unmodified
versions.
TABLE IX
Initial1
Example Polymer of ~ L~_ _ Viscosity in
No. Example No. NaAMP_~J-- NDAM 15~ HCl, cps
55Control D 30 70 - 30
56 35 30 69 1 34
57 34 30 69.5 0.5 42
58 36 30 ~9.9 0.1 39
59Control C 40 60 - 23
38 40 59.8 0.2 30
1) Measured with a Fann 35 Viscometer (Fann
Instrument Co., Houston, Texas) at room
temperature and 300 rpm and a concentration ~f
1.05S by weight of polymer.
Examples 61-68
The examples shown in Table X further
illustrate the benefit of this in~ention with
di~ferent types of hydrophobic comonomers.
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TABLE X
~al1
Yi~cosity
Example Polymer of MQle ~in 15
No. Exam~le No. 1~1}5~quo~ 3 ~ e
61 Control D 30 70 --- 3~
62 41 30 69.9NPPEM 0.1 58
63 42 30 69.5NPPEM 0.5 47
64 43 30 69.9NBMA 0.1 39
44 30 69.5NBMA 0.5 44
66 45 30 69.0N~MA 0.1 45
67 46 30 69.9NTBMA 0.1 37
68 47 30 69.0NTBMA 1.0 37
1) Measured with a Fann 35 Yiscometer at room
temperature and 300 rpm and a concentration of
1.05~ ~y weight o~ polymer.
The data in Tables IX and X show the
polymers of this invention, whioh contain the
hydrophobe monomers, when used as acid viscosifiers
produce acid solutions having higher initial
viscosities than are obtained when using a polymer
that does not contain the hydrophobe in the
molecule.
Exam ~
The benefit of retaining a higher portion of
its initial viscosity in acid fluid is accomplished
by the incorporation of the multi~unctional
comonomers described in this patent. Data in Table
XI show the viscosity retention as a function o~
temperature and time when the various level~ of
polyrunctional monomer are employed.
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~3~2~3
- 36 -
TABLE XI
VISCOSITY RETENTION OF
ANIONIC ACID VISCOSIFIERS CONTAINING
DIFFERENT LEVELS O F EDMA
Example No. 40 51 50 49
EDMA, Mole % - 0.1 0.3 0.6
Initial Viscosity1
at 100F, cps48 23 28 11
Retained1,2
Viscosity, ~
at 150F 75 67 72 42
at 200F 56 43 53 36
at 225F 47 37 53 32
at 250F 38 40 65 29
at 250F ~ 5 min. 38 57 116 57
at 250F ~ 15 min. - - 222 217
' at 250F ~ 30 min. - - - 629
;~ after cooling1
!~ back to 100F78 113 250 >1000
1) Measured at a polymer concentration of 2.1% by
' weight using a Fann 50 Viscometer at 100 rpm.
I 2) Viscosity at 100F = 100%.
D 15387

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~e~
Into a one-liter pyrex~ lass reactor9
equipped with a turbine agitator, ther~ometer,
addition funnel, condenser, nitrogen inlet and
outlet, and an external heating or cooling ~ath,
there was charged about 700 g of a water~in-oil
monomeric emulsion. The latter ~as prepared by
emulsifying, with a Waring blender, an aqueous
solution consisting of 162.4 g of sodium
2-~crylamido-2-methylpropane sulfonate as the anionic
monomer, 92 g of a 62~ aqueous solution of
dimethyldiallylam~onium chloride as the cationic
monomer, 150.3 g of a 50~ aqueous solution of
acrylamide as the water soluble monomer, 1.4 g o~
nonylphenoxypoly(ethyleneoxy)ethylmetha~ylate as the
hydrophobic monomer, 0.14 g of Versenex ~0, and
130.2 g of deionized water with an oil solution
comp~sed o~ 157.8 g of Isopar~ solvent and 9.5 g of
Span~O surfactant (sorbitan monooleate). The
monomeric emulsion was deaerated by nitrogen sparging
for 30 minutes. Thereafter,j~n initiator solution
consisting of 0.012 g of VAZ ~ 3
(2,2'-azobis[2,4-dimethyl-4-~ethoxy valeronitrile])
and 1.5 g of xylene was introduced. The reactor was
heated to 50C. Once the polymerization initiated,
an external cooling bath was used to maintain the
reactor temperature at 50 ~ 2C. In the meantime, a
seco~d initiator solution consi~tiDg of 0.18 g of
VAZ ~ 2 (2,2'-azobisL2~4-dimethyl valeronitrileJ) and
7.5 g o~ xylene was added in six equal portions with
a 10-minute interval between additions. Upon
completion o~ the addition of the 3econd initlator,
D-15387

2~3
38 ~
the polymerization was heated ~or 4 more hours at 50
2C. At the end o~ the polymerization, the reactor
~as cooled to room~temperature and a solution of
0.19 g of Santono ~ in 2.5 g of xylene together with
10.8 g Or TERGIT0~-~P10 surfactant was added to the
mixture. The finished polymeric emulsion was milky
white in appearance and exhibited a Brookfield
vi~cosity of 880 cps tModel HBT, 10 rpm at 25C).
The reco~ered polymer pos~essed a reduced viscosity
of 6.2 dl/g in lN NaCl solution.
A polymer was prepared using the equipment
and procedures described in Example 72, with the
exception that the aqueous solution consisted of
163.4 g of a 50% aqueous solution of sodium
2-acrylamido-2-methylpropane ~ulfonate as the anionic
monomer, 92.5 g of a 62S aqueous solution of (DMDAAC)
dimethyldiallylammonium ~hloride as the cationic
monomer, 151.5 g of a 5C~ aqueous solution of
acrylami~e as the water soluble monomer, 0.14 g of
Ver~enex 80, and 12B.9 B Or deionized water. The
~inished polymeric e~ulQion exhibited a Brookfield
viscosity of 1500 cps (Model HBT, 10 rpm at 25DC).
The reco~ered poly~er pos~essed a r-educed viscosity
of 7.6 dl/g in 1N NaCl solution at 25C.
Example 74
An acid fluid containing 1.05 g of active
polymer Or Example 72 in 15S HCl was heated in a
180F water bath ~or 60 mlnutes. The acid ~luid
~howed no visible polymeric precipitate. ~eaction
D- 1 5387

3g -
wit~ limestone showed no significant change in
viscosity nor any evidence of precipation. Under the
~ame te~ing conditions, elther the corr~ponding
(NaAMPS~M) copolymer (at 20/80 molar ratio) or
(DMDAAC-AM~ copolymer (at 20/80 molar ratio) resulted
in precipitation of the polymer on heating.
.
Exam?le 75
An acid fluid containing 1.05 g of active
polymer of Example 72 in 15~ HCl produced a solution
viscosity of 40 cps (Fann 35 viscometer ~easured at
300 rpm and 25C). A control fluid made with the
~ame amount of polymer of Example 73 gave a solution
viscosity of 3l~ ~ps.
Using the equipment and general procedures
described in Example 72, a copolymer composed of 30
m~le percent of N-(3-sulfopropyl)-N-methacrylamido-
propyl-N,N-dimethylammonium-betain (SPP) and 70 mole
percent Or acrylamide was prepared. The resu}tant
polymeric emulsion exhibited a ~rookfield vi cosity
of 1,4~G cps. The recovered polymer possessed a
reduced viscosity (RV) of i.5 dl/g in lN NaCl
solution at 25C.
Example 76 was repeated wi'ch the exception
that a ~mall amount of a hydrophobic comonomer,
nonylphenoxy~-psly(ethyleneoxy)ethyllDethacrylata
(NPPEM), ~a~ incorporated into the polymerizatlDn
~ormulation 30 that ths resul'cant product was 8
D-15387
, ... .

- 40 -
(NPPEM-SPP-AM) terpolymer containing 0.1, 30; and
6g.9 mole percent of these monomers, respectively.
The resultant polymeric emulsion exhibited a
Brookfield viscosity of 1,600 cps. The recovered
polymer possessed a reduced viscosity of 6.7 dl~g.
Exampl_ 78
- The thermal-thinning behavior in 15% HCl
solution of the polymers prepared in Example 76 and
77 were measured using a Fann 50 viscometer operating
at 130 rpm and a programmed heating rate of 12F/min.
A polymer concentration of 1.05 weight percent was
employed.
Initial % Retention of
I Polymer o~ Viscosity at 100F Visco.sity at
Example RV100F, cps150 200 250 300
¦ 76 7.5 51 72 43 23 9
77 6.9 67 82 50 3~ 27
The polymer in Example 77, which contained a
small amount of hydrophobic monomer NPPEM, produced a
significantly higher degrees of viscosity retention
at elevated temperatures than its corresponding
polymer without the hydrophobic comonomer indicating
it was more stable to heat.
D-15387