Note: Descriptions are shown in the official language in which they were submitted.
1
USE OF HYDROPHOBICALLY ASSOCIATING COPOLYMER AS ADDITIVE
IN SPECIFIC OILFIELD APPLICATIONS
The present invention relates to the use of a water-soluble hydrophobically
associating
copolymer as an additive in the development, exploitation and completion of
under-
ground mineral oil and natural gas deposits and in deep drillings.
A copolymer of the above mentioned type is described in WO 2011/015520 Al with
pri-
ority of 06.08.2009, published on 10.02.2011. That international patent
application con-
cerns a water-soluble, hydrophobically associating copolymer which is obtained
in the
presence of an non-polymerizable tenside, and processes for the preparation
thereof
and uses thereof. However, the specific applications und uses as described and
claimed in this present patent application have not been recognized and
described in
that prior international patent application.
Water-soluble thickening polymers are used in many fields of industry, for
example in
the field of cosmetics, in foods, for production of detergents, printing inks
and emulsion
paints, but especially in mineral oil production.
There are many known chemically different classes of polymers which can be
used as
thickeners. An important class of thickening polymers is that of what are
called "hydro-
phobically associating polymers". These are water-soluble polymers which have
lateral
or terminal hydrophobic groups, for example relatively long alkyl chains. In
aqueous
solution, such hydrophobic groups can associate with each other or with other
substan-
ces having hydrophobic groups. This forms an associative network by which the
me-
dium is thickened.
According to Taylor, K.C. and Nasr-El-Din, H.A., "Hydrophobically Associating
Poly-
mers for Oilfield Applications", presented at the Canadian International
Petroleum Con-
ference, Calgary, AB, Canada, June 12-14, 2007, p.1, "... hydrophobically
associating
polymers (AP) are water-soluble polymers that contain a small number (less
than one
mole percent) of hydrophobic groups attached directly to the polymer
backbone...".
This definition shall be adhered to for the purpose of the present patent
application,
keeping in mind, however, that one mole percent can be as much as ten or even
twenty percent by weight of that hydrophobic groups.
An important area of use of these hydrophobically associating polymers is in
the field of
mineral oil production, especially of tertiary mineral oil production
(enhanced oil recov-
ery, EOR). Details of the use of hydrophobically associating copolymers for
tertiary
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mineral oil production are described, for example, in the review article by
Taylor, K.C.
and Nasr-El-Din, H.A. in J. Petr. Sci. Eng. 1998, 19, 265-280.
Another of the techniques of tertiary mineral oil production is known as
"polymer flood-
ing". A mineral oil deposit is not an underground "lake of mineral oil", but
rather the
mineral oil is held in tiny pores of the mineral oil-bearing rock. The
diameter of the
pores in the formation is typically only a few micrometers. For polymer
flooding, an
aqueous solution of a thickening polymer is injected through injection
boreholes into a
mineral oil deposit. The injection of the polymer solution forces the mineral
oil through
said cavities in the formation from the injection borehole proceeding in the
direction of
the production borehole, and the mineral oil is produced via the production
borehole.
The use of an aqueous polymer solution as opposed to pure water prevents
channels
of different permeability from forming in the course of flooding of the
underground for-
mation (known as "fingering"), as a result of which the other underground
regions
would not be flooded. The addition of the polymer to the aqueous phase reduces
the
mobility thereof and leads as a result to a more homogeneous flooding
operation.
A further technique in mineral oil production is known as "hydraulic
fracturing". In hy-
draulic fracturing, for example, a high-viscosity aqueous solution is injected
under high
pressure into the oil- or gas-bearing formation layer. The high pressure gives
rise to
cracks in the rock, which facilitates the production of oil or gas. The
thickeners used
here are in particular guar and the more thermally stable derivatives thereof,
for exam-
ple hydroxypropylguar or carboxymethylhydroxypropylguar (J. K. Fink, Oil Field
Chemi-
cals, Elsevier 2003, p. 240 if). These biopolymers, however, like most
polymers in gen-
eral, have a distinct decrease in viscosity with rising temperature. Since,
however, ele-
vated temperatures exist in the underground formations, it would be
advantageous for
use in hydraulic fracturing to use thickeners whose viscosity does not
decrease or ac-
tually even rises with rising temperature.
Further areas of use of hydrophobically associating copolymers in the field of
mineral
oil production are the thickening of drilling muds and completion fluids. For
example,
Ezell et al. (presentation AADE-10-DF-H0-01 at the AADE Fluids Conference and
Ex-
hibition, Houston, TX, USA, 6-7 April 2010) describe the use of associative
thickeners
in completion fluids. In addition, Taylor describes, in his review article
(Ann. Transac-
tions of the Nordic Rheology Society, Vol. 11, 2003), the use of
hydrophobically asso-
ciating polymers in drilling muds and completion fluids. It is stated that the
viscosity of
these copolymers decreases with rising temperature.
Foamed fluids are used in hydraulic fracturing, both as "proppants" and as
"diverting
agents" (Burman et al., 1986, DOI: 10.2118/15575-MS; Parlar et al., 1995, DOI:
10.2118/29678-MS). The foam is said to remain stable over the entire
treatment. Differ-
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3
ent factors influence the stability of the foam, including the viscosity, the
chemical com-
position of the foam formers, the formation temperature and the gas phase.
It should also be ensured that the aqueous polymer solution contains no gel
particles at
all. This is because even small gel particles with dimensions in the
micrometer range
can block the fine pores in the formation and hence stop the mineral oil
production.
Hydrophobically associating copolymers for mineral oil production should
therefore
have a minimum proportion of gel particles. The aim is for the polymers to
achieve an
increase in the viscosity of the water, which ideally corresponds to the
viscosity of the
hydrocarbons to be produced.
Hydrophobically associating water-soluble copolymers are frequently prepared
by what
is known as micellar copolymerization. This involves solvating water-insoluble
comono-
mers by the addition of surfactants in the aqueous reaction medium and
reacting them
with hydrophilic comonomers, for example acrylamide, to give a water-soluble
hydro-
phobically associating copolymer. For example, Macromol. Chem. Phys. 2001,
202,
1384-1397 describes the micellar copolymerization of the water-soluble
comonomers
acrylamide, AMPS - (acrylamidomethylpropanesulphonic acid) and MADQUAT ([2-
(methacryloyloxy)ethyl]trimethylammonium chloride) with dihexylacrylamide or N-
(4-
ethylphenyl)acrylamide, while Polymer 1998, 39 (5), 1025-1033 discusses the
copoly-
merization of acrylamide with dihexylacrylamide, and Eur. Polym. J. 2007, 43,
824-834
the copolymerization of acrylamide with N-octadecylacrylamide. The surfactant
used in
both cases is sodium dodecylsulphonate (SDS). A further example of a micellar
copoly-
merization is given by J. Colloid Interf. Sci. 2009, 333, 152-163. Acrylamide
is reacted
here with a polypropylene glycol methacrylate in the presence of SDS.
In addition, WO 85/03510 describes water-soluble hydrophobically associating
copoly-
mers of an ethylenically unsaturated water-soluble monomer and of an
ethylenically
unsaturated amphiphilic monomer with hydrophobic groups. These copolymers are
ob-
tamed by reaction of water-soluble monomers, for example acrylamide, and
amphiphilic
monomers, for example dodecylpolyoxyethylene (10) methacrylate. The
amphiphilic
comonomers are characterized as water-soluble at room temperature but water-
insolu-
ble at elevated temperature or the temperature used in the preparation of the
copoly-
mers, for example of 60 C. Therefore, a surfactant or emulsifier is added here
too if re-
quired, i.e. when the polymerization is effected at elevated temperature, in
order to en-
sure the solubility of the amphiphilic comonomer under the polymerization
conditions.
However, the monomer is then no longer a water-soluble variant.
A further method for preparation of water-soluble hydrophobically associating
copoly-
mers is the use of surface-active water-soluble comonomers. These comonomers
have
a hydrophobic component which brings about the hydrophobically associating
effect in
the copolymer, and a hydrophilic component which ensures the water solubility
of the
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4
comonomer. The advantage of this process is that no additional surfactant is
needed
for solvation of the hydrophobically associating monomer.
Examples of the use of this process can be found in EP 705 854 Al, DE 100 37
629 Al
and DE 10 2004 032 304 Al. These documents disclose water-soluble
hydrophobically
associating copolymers and use thereof, for example in the construction
chemistry sec-
tor. The hydrophobically associating monomers present in the copolymers
disclosed
are in each case monomers of the following type: H2C=C(Rx)-000-(-CH2-CH2-0-)q-
RY
or else H2C=C(Rx)-0-(-CH2-CH2-0-)q-RY, where Rx is typically H or CH3 and RY
is a
larger hydrocarbyl radical, typically hydrocarbyl radicals having 8 to 40
carbon atoms.
Examples specified in the documents are relatively long alkyl groups, or else
a tristyryl-
phenyl group.
In addition, J. Appl. Polym. Sci. 1999, 74, 211-217 discusses the use of a
cationic wa-
ter-soluble hydrophobically associating comonomer which has been obtained by
react-
ing 2-methacryloyloxyethyldimethylamine with 1-bromododecane.
Canadian patent 2,196,908 is concerned with associating monomers and polymers.
At
the forefront of this document are essentially emulsion polymers of
methacrylic acid,
ethyl acrylate and a monomer which has been obtained by reaction of dimethyl-m-
isoprenylbenzyl isocyanate (DMI) and El M or polybutylene oxide or
polybutylene oxide-
co-polyethylene oxide. This is done using in particular water-insoluble and
nonhydro-
philic monomers, for example ethyl acrylate.
It can be stated in general terms that the known hydrophobically associating
copoly-
mers when used as thickeners in the field of mineral oil production have the
disadvan-
tage that the viscosity decreases with rising temperature. Since the use of
these poly-
mers in mineral oil production usually takes place at elevated temperature,
this is a
particularly serious disadvantage.
A further disadvantage of the above-described and commercially available
hydrophobi-
cally associative polymers is the high gel content thereof, which forms in the
course of
dissolution and can block porous formations. This problem has already been
partly
solved with copolymers according to our prior international patent application
WO
2010/133527 A2 with priority of 20.05.2009, published 25.11.2010. The gel
contents
were reduced markedly therein, but not avoided entirely. There was still a
need for hy-
drophobically associative polymers with improved properties compared to the
already
known hydrophobically associating copolymers. Our above mentioned prior
interna-
tional patent application WO 2011/015520 Al provides a hydrophobically
associating
copolymer with low or undetectable gel content.
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The object of this present invention was to examine whether this copolymer is
suitable
for use as an additive in the development, exploitation and completion of
underground
mineral oil and natural gas deposits and in deep drillings, for example in
hydraulic fract-
uring, as a thickener or stabilizer of foams, and as a thickener of completion
fluids, spa-
5 cer fluids and drilling muds under the conditions customary in
underground formations.
This object is achieved by the features of the independent claim. The
dependent claims
relate to preferred embodiments.
It has been found that, surprisingly, the copolymer described in our above
mentioned
prior international patent application WO 2011/015520 Al has an advantageous
vis-
cosity profile and is particularly suitable, for example, as a thickener for
completion flu-
ids, spacer fluids and drilling muds, hydraulic fracturing and foams, since
the viscosity
of this copolymer increases with rising temperature up to a maximum at approx.
60 C.
The present invention thus provides for the use of a hydrophobically
associating co-
polymer as an additive in the development, exploitation and completion of
underground
mineral oil and natural gas deposits and in deep drillings, wherein the
copolymer com-
prises
(a) at least one monoethylenically unsaturated monomer (a) selected from
H2C=C(R1)-R4-0-(-CH2-CH2-0-)k+CH2-CH(R3)-0-)I-R5 (I), and/or
H2C=C(R1)-0-(-CH2-CH2-0-)k-R2 (II),
where the -(-CH2-CH2-0-)k- and -(-CH2-CH(R3)-0-)i- units are arranged in block
struc-
ture in the sequence shown in formula (I) and the radicals and indices are
each defined
as follows:
k: a number from 6 to 150,
I: a number from 5 to 25,
R1: H or methyl,
R2: an aliphatic and/or aromatic, straight-chain or branched hydrocarbyl
radical hav-
ing 8 to 40 carbon atoms,
R3: each independently a hydrocarbyl radical having at least 2 carbon atoms,
R4: a single bond or a divalent linking group selected from the group of -
(CnH2n)-
[R4a], -0-(Cn.H2)- [R4b] and -C(0)-0-(Cn..1-12no)- [R4c], where n, n' and n"
are
each integers from 1 to 6,
R5: H or a C1_30-hydrocarbyl radical, preferably H or a Ci_5-alkyl radical
and particu-
larly H,
and (b) at least one monoethylenically unsaturated, hydrophilic monomer (b)
different
from monomer (a), wherein the copolymer is obtainable through copolymerization
of
the monomers (a) and (b) in the presence of at least one surfactant (c).
The synthesis of the copolymer as used according to the invention, before the
initiation
of the polymerization reaction, advantageously involved the presence of said
at least
one surfactant (c), which is a nonpolymerizable surfactant.. The term "nonpoly-
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6
merizable surfactant" as used herein has been chosen for clarity reasons.
Surfactants,
as a rule, are nonpolymerizable compounds. By using this term, it is meant to
clarify
that the surfactant (c) will not become chemically bound to, in or by the
copolymer of
the invention.
As already mentioned above, one advantage of the processes known from the
prior art
is considered to be that the hydrophobically associating copolymers can be
prepared
without the addition of a surfactant, since all comonomers used therein are
water-solu-
ble. It was therefore all the more surprising that, in the copolymer according
to WO
2011/ 015520 Al, the addition of a surfactant during the aqueous solution
polymeriza-
tion of hydrophilic monomers with a water-soluble hydrophobically associating
co-
monomer achieved a distinct improvement in the polymer properties, especially
the
thickening action, and also significantly reduced the gel content. Without
wanting to be
bound by theory, this effect can probably be explained as follows:
In the known procedure, the hydrophobically associating comonomer forms micels
in
the aqueous reaction medium. In the polymerization, the effect of this is that
the hydro-
phobically associating regions are incorporated blockwise into the polymer. If
an addi-
tional nonpolymerizable surfactant is present in the course of preparation of
the co-
polymer, preferably already before the initiation of the polymerization
reaction, mixed
micelles form. These mixed micelles thus contain polymerizable comonomer and
non-
polymerizable sufractant. As a result, the hydrophobically associating
monomers are
then incorporated in shorter blocks. At the same time, the number of these
shorter
blocks per polymer chain is greater. Thus, the polymer constitution of the
copolymer
according to WO 2011/015520 Al differs distinctly from the prior art
copolymers, as a
result of which the performance properties thereof also improve significantly.
The inventive hydrophobically associating copolymers are water-soluble
copolymers
which contain a small number of hydrophobic groups. In aqueous solution, the
hydro-
phobic groups can associate with themselves or with other substances having
hydro-
phobic groups, and thicken the aqueous medium by virtue of this interaction.
The person skilled in the art is aware that the solubility of hydrophobically
associating
(co)polymers in water may be dependent to a greater or lesser degree on the pH
ac-
cording to the type of monomers used. The reference point for the assessment
of water
solubility should therefore in each case be the pH desired for the particular
end use of
the copolymer. A copolymer which has insufficient solubility for the intended
end use at
a particular pH may have a sufficient solubility at a different pH. The term
"water-
soluble" especially also includes alkali-soluble dispersions of polymers, i.e.
polymers
which are present as dispersions in the acidic pH range and only in the
alkaline pH
range dissolve in water and display their thickening action.
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In the ideal case, the copolymers of the invention should be miscible with
water in any
ratio. According to the invention, however, it is sufficient when the
copolymers are wa-
ter-soluble at least at the desired use concentration and at the desired pH.
In general,
the solubility in distilled water at room temperature (20 C) should be at
least 20 g/I,
preferably at least 50 g/I and more preferably at least 100 g/I.
The inventive hydrophobically associating copolymers therefore comprise, in
addition
to the hydrophobic groups already mentioned, hydrophilic groups in such an
amount
that the water solubility outlined is ensured at least in the pH range
envisaged for the
particular use.
Monomer (a)
The inventive hydrophobically associating copolymer comprises at least one
mono-
ethylenically unsaturated monomer (a) which imparts hydrophobically
associating
properties to the copolymer of the invention and is therefore referred to
hereinafter as
"hydrophobically associating monomer". According to the invention, the at
least one
monoethylenically unsaturated water-soluble monomer (a) is at least one
compound of
the general formulas (I) and/or (II) as defined hereinabove.
In the monomers (a) of the formula (I), an ethylenic group H2C=C(R1)- is thus
bonded
via a divalent linking -R4-0- group to a polyoxyalkylene radical with block
structure, i.e.
-(-CH2-CH2-0-)k+CH2-CH(R3)-0-)I-H, where the two -(-CH2-CH2-0-)k- and -(-CH2-
CH(R3)-0-)i- blocks are arranged in the sequence shown in formula (I). The
polyoxy-
alkylene radical may thus have a terminal OH group.
In the abovementioned formula, R1 is H or a methyl group. R4 is a single bond
or a di-
valent linking group selected from the group of -(CH2)- [R4a], -O-(CH2)- [R4b]
and
-C(0)-0-(CH2)- [R4c]. In the formulae mentioned, n, n' and n" are each natural
numbers from 1 to 6. In other words, the linking group comprises straight-
chain or
branched aliphatic hydrocarbyl groups having 1 to 6 carbon atoms, which are
joined to
the ethylenic group H2C=C(R1)- directly, via an ether group ¨0- or via an
ester group
-C(0)-0-. The -(CH2)-, -(CH2)- and -(CH2)- groups are preferably linear
aliphatic
hydrocarbyl groups.
R4a is preferably a group selected from ¨CH2-, -CH2-CH2- and ¨CH2-CH2-CH2-,
more
preferably a methylene group ¨CH2-.
Rab is preferably a group selected from -0-CH2-CH2-, -0-CH2-CH2-CH2- and -0-
CH2-
CH2-CH2-CH2-, more preferably ¨0-CH2-CH2-CH2-CH2-.
R4c
is preferably a group selected from -C(0)-0-CH2-CH2-, -C(0)0-CH(CH3)-CH2-,
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8
-C(0)0-CH2-CH(CH3)-, -C(0)0-CH2-CH2-CH2-CH2- and -C(0)0-CH2-CH2-CH2-CH2-
CH2-CH2-, more preferably -C(0)-0-CH2-CH2- and -C(0)0-CH2-CH2-CH2-CH2- and
most preferably -C(0)-0-CH2-CH2-.
The R4 group is more preferably an R4a or R4b group, more preferably an R4b
group.
In addition, R4 is more preferably a group selected from ¨CH2- and -0-CH2-CH2-
CH2-
CH2-, most preferably -0-CH2-CH2-CH2-CH2-.
The monomers of the formula (I) also have a polyoxyalkylene radical which
consists of
the units -(-CH2-CH2-0-)k- and -(-CH2-CH(R3)-0-)i- where the units are
arranged in
block structure in the sequence shown in formula (I). The transition between
the two
blocks may be abrupt or else continuous.
The number of alkylene oxide units k is a number from 6 to 150, preferably 12
to 100,
more preferably 15 to 80, even more preferably 20 to 30 and, for example,
approx. 22
to 25. It is clear to the person skilled in the art in the field of the
polyalkylene oxides that
the numbers mentioned are averages of distributions.
In the second, terminal -(-CH2-CH(R3)-0-)i- block, the R3 radicals are each
independ-
ently hydrocarbyl radicals of at least 2 carbon atoms, preferably at least 3
and more
preferably 3 to 10 carbon atoms. This may be an aliphatic and/or aromatic,
linear or
branched carbon radical. It is preferably an aliphatic radical.
Examples of suitable R3 radicals comprise ethyl, n-propyl, n-butyl, n-pentyl,
n-hexyl, n-
heptyl, n-octyl, n-nonyl or n-decyl, and phenyl. Examples of preferred
radicals comprise
n-propyl, n-butyl, n-pentyl, particular preference being given to an n-propyl
radical.
The -(-CH2-CH(R3)-0-)i- block is thus a block which consists of alkylene oxide
units
having at least 4 carbon atoms, preferably at least 5 carbon atoms, and/or
glycidyl
ethers having an ether group of at least 2, preferably at least 3, carbon
atoms. Pre-
ferred R3 radicals are the hydrocarbyl radicals mentioned; the units of the
second ter-
minal block are more preferably alkylene oxide units comprising at least 5
carbon at-
oms, such as pentene oxide units or units of higher alkylene oxides.
The number of alkylene oxide units I is a number from 5 to 25, preferably 6 to
20, more
preferably 8 to 18, even more preferably 10 to 15 and, for example, approx.
12.
In the monomers of the formula (I), a monoethylenic group is joined to a
polyoxyal-
kylene group with block structure, specifically firstly to a hydrophilic block
having poly-
ethylene oxide units, which is in turn joined to a second terminal hydrophobic
block
formed at least from butene oxide units, preferably at least pentene oxide
units, or units
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of higher alkylene oxides, for example dodecene oxide. The second block has a
termi-
nal OH group. In contrast to the hydrophobically associating monomers (a) of
the for-
mula (II) and/or (III), the end group is thus not etherified with a
hydrocarbyl radical for
the hydrophobic assocation, but rather the terminal -(-CH2-CH(R3)-0-)i- block
with the
R3 radicals is itself responsible for the hydrophobic association of the
copolymers pre-
pared using the monomers (a) of the formula (I).
The R5 radical is H or a preferably aliphatic hydrocarbyl radical having 1 to
30 carbon
atoms, preferably 1 to 10 and more preferably 1 to 5 carbon atoms. R5 is
preferably H,
methyl or ethyl, more preferably H or methyl and most preferably H.
The monomers (a) of the formula (II) are preferably compounds of the general
formula
H2C=CH-0-(-CH2-CH2-0-)k-R2 where k is a number from 10 to 40 and R2 is a
tristyryl-
phenyl radical.
The monomer representatives (I) and (II) may be involved in any proportions in
the
structure of the copolymer.
It is clear to the person skilled in the art in the field of polyalkylene
oxide block copoly-
mers that the transition between the two blocks, according to the method of
prepara-
tion, may be abrupt or else continuous. In the case of a continuous
transition, there is
still a transition zone between the two blocks, which comprises monomers of
both
blocks. When the block boundary is fixed at the middle of the transition zone,
it is pos-
sible for the first block -(-CH2-CH20-)k- to have small amounts of -CH2-CH(R3)-
0- units
and for the second block -(-CH2-CH(R3)-04- to have small amounts of -CH2-CH2-0-
units, although these units are not arranged randomly over the block but are
arranged
in the transition zone mentioned.
According to the invention, the monomers (a) are water-soluble. In general,
the solubil-
ity of the monomers (a) in distilled water at room temperature (20 C) should
be at least
10 g/I, preferably at least 50 g/I and more preferably at least 100 g/I.
The amount of the monoethylenically unsaturated, hydrophobically associating
mono-
mers (a) is guided by the particular end use of the inventive copolymer and is
generally
0.1 to 20% by weight based on the total amount of all monomers in the
copolymer. The
amount is preferably 0.5 to 15% by weight.
Hydrophilic monomers (b)
Over and above the monomers (a), the inventive hydrophobically associating
copoly-
mer comprises at least one different monoethylenically unsaturated hydrophilic
mono-
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mer (b). It is of course also possible to use mixtures of a plurality of
different hydrophilic
monomers (b).
The hydrophilic monomers (b) comprise, in addition to an ethylenically
unsaturated
5 group, one or more hydrophilic groups. The hydrophilic groups are
especially functional
groups which comprise oxygen and/or nitrogen atoms. They may additionally
comprise
especially sulphur and/or phosphorus atoms as heteroatoms.
In the ideal case, the monomers (b) should be miscible with water in any
ratio, but it is
10 sufficient for execution of the invention that the hydrophobically
associating copolymer
of the invention has the water solubility mentioned at the outset. In general,
the term
"hydrophilic" in connection with monomer (b) means that the solubility of
monomer (b)
in distilled water at room temperature (20 C) should be at least 100 g/I,
preferably at
least 200 g/I and more preferably at least 500 g/I.
Examples of suitable functional groups include carbonyl groups >C=0, ether
groups
-0-, especially polyethylene oxide groups -(CH2-CH2-0-)n- where n is
preferably a
number from 1 to 200, hydroxyl groups -OH, ester groups -C(0)0-, primary,
secondary
or tertiary amino groups, ammonium groups, amide groups -0(0)-NH-, carboxamide
groups
-0(0)-NE12, or acidic groups such as carboxyl groups -COOH, sulpho groups -
S03H,
phosphonic acid groups -P03H2 or phosphoric acid groups -0P(OH)3.
Examples of preferred functional groups include hydroxyl groups -OH, carboxyl
groups
-COOH, sulpho groups -S03H, carboxamide groups -C(0)-NH2, amide groups
-0(0)-NH- and polyethylene oxide groups -(CH2-CH2-0-)n-H where n is preferably
a
number from 1 to 200.
The functional groups may be attached directly to the ethylenically
unsaturated group,
or else joined to the ethylenically unsaturated group via one or more linking
hydrocarbyl
groups.
The at least one hydrophilic monomer (b) is preferably a monomer comprising
acidic
groups, where the acidic groups, in accordance with the invention, comprise at
least
one group selected from the group of -COOH, -S03H and -P03H2. Preference is
also
given to monomers of the general formula H2C=C(R7)R8 where R7 is H or methyl
and
RB is a hydrophilic group or a group comprising one or more hydrophilic
groups.
The RB groups are groups which comprise heteroatoms in such an amount that the
water solubility defined at the outset is attained.
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11
Examples of suitable monomers (b) include monomers comprising acidic groups,
for
example monomers comprising -COON groups, such as acrylic acid or methacrylic
acid, crotonic acid, itaconic acid, maleic acid or fumaric acid, monomers
comprising
sulpho groups, such as vinylsulphonic acid, allylsulphonic acid, 3-allyloxy-2-
hydroxy-
propanesulphonic acid, 2-acrylamido-2-methylpropanesulphonic acid (AMPS), 2-
methacrylamido-2-methylpropanesulphonic acid, 2-acrylamidobutanesulphonic
acid, 3-
acrylamido-3-methylbutanesulphonic acid or 2-acrylamido-2,4,4-
trimethylpentanesulphonic acid, or monomers comprising phosphonic acid groups,
such as vinylphosphonic acid, allylphosphonic acid,
N-(meth)acrylamidoalkylphosphonic acids or (meth)acryloyloxyalkylphosphonic
acids.
Mention should also be made of acrylamide and methacrylamide and derivatives
thereof, for example N-methyl(meth)acrylamide, N,N'-dimethyl(meth)acrylamide
and
N-methylolacrylamide, N-vinyl derivatives such as N-vinylformamide, N-
vinylacetamide,
N-vinylpyrrolidone or N-vinylcaprolactam, and vinyl esters such as vinyl
formate or vinyl
acetate. N-Vinyl derivatives can be hydrolysed after polymerization to
vinylamine units,
and vinyl esters to vinyl alcohol units.
Further examples include monomers comprising hydroxyl and/or ether groups, for
ex-
ample hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, allyl
alcohol, hy-
droxyvinyl ethyl ether, hydroxyvinyl propyl ether, hydroxyvinyl butyl ether,
or com-
pounds of the formula H2C=C(R1)-000-(-CH2-CH(R9)-0-)b-R1 (IVa) or H2C=C(R1)-0-
(-
CH2-CH(R9)-0-)b-R10 (IVb), where R1 is as defined above and b is a number from
2 to
200, preferably 2 to 100. The R9 radicals are each independently H, methyl or
ethyl,
preferably H or methyl, with the proviso that at least 50 mol% of the R9
radicals are H.
Preferably at least 75 mol% of the R9 are H, more preferably at least 90 mol%,
and
they are most preferably exclusively H. The R1 radical is H, methyl or ethyl,
preferably
H or methyl. The individual alkylene oxide units may be arranged randomly or
in
blocks. In the case of a block copolymer, the transition between the blocks
may be
abrupt or gradual.
Suitable hydrophilic monomers (b) are also monomers having ammonium groups, es-
pecially ammonium derivatives of N-(waminoalkyl)(meth)acrylamides or
oraminoalkyl
(meth)acrylic esters.
More particularly, monomers (b) having ammonium groups may be compounds of the
general formulae H2C=C(R7)-CO-NR13-R11_NR123+ X- (Va) and/or H2C=C(R7)-COO-R11-
NR123+ X- (Vb), where R7 is as defined above, i.e. is H or methyl, R11 is a
preferably lin-
ear C1- Cealkylene group, and R13 is H or a C1- C4-alkyl group, preferably H
or methyl.
The R12 radicals are each independently Ci-C4alkyl, preferably methyl, or a
group of
the general formula -R14-S03H, where R14 is a preferably linear Ci-C4alkylene
group or
a phenyl group, with the proviso that generally not more than one of the R12
substitu-
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12
ents is a substituent having sulpho groups. More preferably, the three R12
substituents
are each methyl groups, i.e. the monomer has a -N(CH3)3+ group. X- in the
above for-
mula is a monovalent anion, for examople Cl-. Of course, X may also be a
correspond-
ing fraction of a polyvalent anion, though this is not preferred. Examples of
suitable
monomers (b) of the general formula (Va) or (Vb) include salts of 3-
trimethylammonio-
propylacrylamides or 2-trimethylammonioethyl (meth)acrylates, for example the
corre-
sponding chlorides such as 3-trimethylammoniopropylacrylamide chloride (DI
MAPA-
QUAT) and 2-trimethylammonioethyl methacrylate chloride (MADAME-QUAT).
The monomer (b) may thus be an uncharged monomer (b1), and here especially a
monomer selected from the group of (meth)acrylamide, N-methyl(meth)acrylamide,
N,N-dimethyl(meth)acrylamide, N-methylol(meth)acrylamide, N-vinylformamide or
N-
viny1-2-py r r olid on e , and the monomer (b2) may be at least one selected
from the group
of (meth)acrylic acid, vinylsulphonic acid, allylsulphonic acid, 2-acrylamido-
2-
methylpropanesulphonic acid (AMPS ), 2-methacrylamido-2-methylpropanesulphonic
acid, 2-acrylamidobutanesulphonic acid, 3-acrylamido-3-methylbutanesulphonic
acid or
2-acrylamido-2,4,4-trimethylpentanesulphonic acid or vinylphosphonic acid. The
co-
polymer may additionally also comprise at least one cationic monomer (b3)
having
ammonium groups, where the cationic monomer comprises salts of 3-tri-
methylammoniopropyl(meth)acrylamides and 2-
trimethylammonioethyl(meth)acrylates.
The abovementioned hydrophilic monomers can of course be used not only in the
acid
or base form shown, but also in the form of corresponding salts. It is also
possible to
convert acidic or basic groups to corresponding salts after the formation of
the polymer.
As already explained, the inventive copolymer comprises, in a preferred
embodiment of
the invention, at least one monomer (b) comprising acidic groups. These are
preferably
monomers which comprise at least one group selected from the group of -COOH, -
S03H and -P03H2, particular preference being given to monomers comprising COOH
groups and/or -S03H groups, and suitable salts thereof.
At least one of the monomers (b) is preferably a monomer selected from the
group of
(meth)acrylic acid, vinylsulphonic acid, allylsulphonic acid and 2-acrylamido-
2-
methylpropanesulphonic acid (AMPS ), more preferably acrylic acid and/or AMPS
or
salts thereof.
Surfactant (c)
The inventive copolymers are advantageously prepared in the presence of at
least one
nonpolymerizable surfactant (c), which is preferably at least one nonionic
surfactant.
However, anionic and cationic surfactants are also suitable, to the extent
that they do
not take part in the polymerization reaction.
13
Although our prior international patent application WO 2010/133527 A2
mentioned at
the outset discloses, at pages 34-45 ("part B) preparation of the
hydrophobically asso-
ciating copolymers"), the preparation of comparable copolymers which have been
ob-
tamed without the use of a component (c) and are likewise suitable to a
certain extent
for achievement of the object of the invention, the copolymer according to our
prior
international patent application WO 2011/015520 Al mentioned at the outset,
which has
been prepared with addition of a surfactant, exhibits a distinct improvement
in the polymer
properties, especially in the thickening action, and it was also possible to
significantly
reduce the gel content.
In other words, it is also possible in principle not to use this surfactant,
but significantly
better results can be achieved using this surfactant.
The nonionic surfactant is preferably an ethoxylated, long-chain aliphatic
alcohol which
may optionally contain aromatic components. Examples include: C12-14-fatty
alcohol
ethoxylates, C16_18-fatty alcohol ethoxylates, C13-oxo alcohol ethoxylates,
Cio-oxo alco-
hol ethoxylates, C13-15-oxo alcohol ethoxylates, C10-Guerbet alcohol
ethoxylates and
alkylphenol ethoxylates.
A suitable surfactant is especially at least one representative selected from
the group
of the ethoxylated alkylphenols, the ethoxylated saturated iso-C13-alcohols
and/or the
ethoxylated C10-Guerbet alcohols.
Monomers (d)
In special cases, the inventive copolymers, in addition to monomers (a) and
(b), may
optionally also comprise monomers (d) which possess two or more, preferably
two,
ethylenically unsaturated groups. This can achieve a certain level of
crosslinking of the
copolymer, provided that this does not have any undesired adverse effects in
the in-
tended use of the copolymer. Too high a degree of crosslinking should,
however, be
avoided in any case; more particularly, the required water solubility of the
copolymer
must not be impaired. Whether a low level of crosslinking may be advisable in
the indi-
vidual case is guided by the particular use of the copolymer, and the person
skilled in
the art makes an appropriate selection.
Examples of suitable monomers (d) include 1,4-butanediol di(meth)acrylate, 1,6-
hex-
anediol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, neopentyl
glycol
di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol
di(meth)acrylate,
triethylene glycol di(meth)acrylate or oligoethylene glycol di(meth)acrylates,
for exam-
ple polyethylene glycol bis(meth)acrylate, N,N'-methylenebis(meth)acrylamide,
ethyl-
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14
ene glycol divinyl ether, triethylene glycol divinyl ether, triallylamine,
triallylaminemeth-
ammonium chloride, tetraallylammonium chloride or tris(2-hydroxyethyl)
isocyanurate
tri(meth)acrylate.
If present at all, crosslinking monomers (d), however, are used only in small
amounts.
In general, the amount of the monomers (d) should not exceed 1.0% by weight
based
on the amount of all monomers used. Preferably not more than 0.5% by weight
and
more preferably not more than 0.1% by weight should be used. The type and
amount
of the crosslinker are determined by the person skilled in the art according
to the de-
sired use of the copolymer.
Preferably in accordance with the invention, the copolymer is used as a
thickening
rheological additive for hydraulic fracturing. Said copolymer can also be used
as a
thickening rheological additive for completion fluids, spacer fluids and
drilling fluids, or
else as a thickening rheological additive and/or as a stabilizer for foams.
The inventive use is effected preferably at a temperature in the range from 40
C to
120 C, more preferably at 50 C to 100 C.
Overall, monomer component (a) should be present in amounts of 0.1 to 20.0% by
weight, preferably of 0.1 to 5% by weight, monomer component (b) in amounts of
50.0
to 99.8% by weight, and surfactant (c) in amounts of 0.1 to 10.0% by weight,
based in
each case on the total amount of all components in the copolymer. The exact
amount
is guided by the type and the desired end use of the hydrophobically
associating co-
polymers and is determined correspondingly by the person skilled in the art.
More preferably, R3 of monomer component (a) of the formula (I) is a
hydrocarbyl radi-
cal having at least 3 carbon atoms.
More preferably, with regard to monomer component (a) of the formula (I), R1
is H and
R4 is a group selected from -CH2- and -0-CH2-CH2-CH2-CH2-.
As already detailed above, the at least one monomer (b) is preferably a
monomer
comprising acidic groups and/or salts thereof. The acidic groups are
preferably at least
one group selected from -COON, -S03H and -P03H2, and salts thereof.
It is generally considered to be preferred when the copolymer is a copolymer
(Al)
which comprises at least two different hydrophilic monomers (b), which
comprise at
least
= one uncharged hydrophilic monomer (bl), preferably acrylamide, and
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= at least one hydrophilic anionic monomer (b2) which comprises at least
one
acidic group selected from -COOH, -S03H and -P03H2,
where the amount of the monomers (a) is 0.1 to 20% by weight and that of all
5 monomers (b) together is 70 to 99.5% by weight, based on the amount of
all
monomers in the copolymer.
The preferred uncharged monomers (b1) are (meth)acrylamide, N-
methyl(meth)acryla-
mide, N,N-dimethyl(meth)acrylamide, N-methylol(meth)acrylamide, N-
vinylformamide
10 and N-vinyl-2-pyrrolidone, and the monomer (b2) is at least one monomer
selected
from the group of (meth)acrylic acid, vinylsulphonic acid, allylsulphonic
acid, 2-
acrylamido-2-methylpropanesulphonic acid (AMPS ), 2-methacrylamido-2-
methylpropanesulphonic acid, 2-acrylamidobutanesulphonic acid, 3-acrylamido-3-
methylbutanesulphonic acid, 2-acrylamido-2,4,4-trimethylpentanesulphonic acid
and
15 vinylphosphonic acid.
The inventive copolymer may additionally also comprise at least one cationic
monomer
(b3) having ammonium groups, more preferably salts of 3-trimethylammoniopro-
pyl(meth)acrylamides and/or 2-trimethylammonioethyl (meth)acrylates.
In addition, it is considered to be preferred when the copolymer is a
copolymer (A2)
which comprises at least two different hydrophilic monomers (b), which are at
least
= one uncharged hydrophilic monomer (b1), and
= at least one cationic monomer (b3),
where the amount of the monomers (a) is 0.1 to 20% by weight and that of all
monomers (b) together is 70 to 99.9% by weight, based on the amount of all
monomers in the copolymer.
Finally, it is considered to be preferred when the copolymer is a copolymer
(A3) which
comprises at least two different hydrophilic monomers (b), which are at least
= 5 to 50% by weight
of at least one uncharged hydrophilic monomer (b1),
and
= 25 to 94.9% by weight of at least one anionic monomer (b2) comprising
sulpho groups,
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where the amount of the monomers (a) is 0.1 to 20% by weight and that of all
monomers (b) together is 70 to 99.9% by weight, based on the amount of all
monomers in the copolymer.
More preferably, the inventive copolymer also comprises up to 1% by weight of
the
crosslinking monomer (d) which comprises at least two ethylenically
unsaturated
groups and has already been mentioned above, where monomer (d) comprises at
least
one monomer selected from the group of triallylamine, triallylmethylammonium
chlo-
ride, tetraallylammonium chloride, N,N'-methylenebisacrylamide, triethylene
glycol bis-
methacrylate, triethylene glycol bisacrylate, polyethylene glycol(400)
bismethacrylate
and polyethylene glycol(400) bisacrylate.
Preparation of the water-soluble hydrophobically associating copolymer
The inventive copolymers can be prepared by methods known in principle to
those
skilled in the art, by free-radical polymerization of the monomers (a), (b)
and optionally
(d), for example by solution or gel polymerization in the aqueous phase.
The monomers (a) of the formula (I) used in accordance with the invention are
more
preferably provided by the above-described preparation process by alkoxylating
ethylenically unsaturated alcohols, for example hydroxybutyl vinyl ether,
optionally fol-
lowed by an etherification.
In a preferred embodiment, the preparation is undertaken by means of gel
polymeriza-
tion in the aqueous phase. For gel polymerization, a mixture of the monomers
(a), (b)
and optionally (d), initiators, the surfactant (c) and other assistants with
water is first
provided. Acidic monomers can be neutralized completely or partially before
the po-
lymerization. Preference is given to a pH of approx. 4 to approx. 9. The
concentration
of all components except the solvents is typically approx. 20 to 60% by
weight, pref-
erably approx. 30 to 50% by weight.
It is recommended to subject at least one hydrophobically associating monomer
(a)
and at least one hydrophilic monomer (b) to an aqueous solution polymerization
in the
presence of at least one surfactant (c), preferably by initially charging
monomer corn-
ponent (a) and then successively adding monomer component (b) and component
(c).
In addition, it is optionally possible to add a mixture containing monomer
component (b)
and component (c) to monomer component (a). However, the invention also
includes
addition of component (c) to monomer component (a), and subsequent addition of
monomer component (b) to the mixture obtained. The polymerization should be
per-
formed especially at a pH in the range from 5.0 to 7.5 and preferably at a pH
of 6Ø
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It is important to add the surfactant (c) to the reaction solution before the
initiation of
the polymerization, though the sequence of addition of monomers (a) and (b)
and of
component (c) ¨ as just described ¨ can be selected substantially freely.
The mixture is subsequently polymerized thermally and/or photochemically,
preferably
at -5 C to 50 C. If polymerization is effected thermally, preference is given
to using
polymerization initiators which can initiate even at comparatively low
temperature, for
example redox initiators. The thermal polymerization can be undertaken even at
room
temperature or by heating the mixture, preferably to temperatures of not more
than
50 C. The photochemical polymerization is typically undertaken at temperatures
of
-5 C to 10 C. Particularly advantageously, photochemical and thermal
polymerization
can be combined with one another, by adding both initiators for the thermal
and photo-
chemical polymerization to the mixture. In this case, the polymerization is
first initiated
photochemically at low temperatures, preferably -5 to +10 C. The heat of
reaction re-
leased heats the mixture, which additionally initiates the thermal
polymerization. By
means of this combination, it is possible to achieve a conversion of more than
99%.
The gel polymerization is generally effected without stirring. It can be
effected batch-
wise by irradiating and/or heating the mixture in a suitable vessel at a layer
thickness of
2 to 20 cm. The polymerization gives rise to a solid gel. The polymerization
can also be
effected continuously. For this purpose, a polymerization apparatus is used,
which pos-
sesses a conveyor belt to accommodate the mixture to be polymerized. The
conveyor
belt is equipped with devices for heating or for irradiating with UV
radiation. In this
method, the mixture is poured onto one end of the belt by means of a suitable
appara-
tus, the mixture is polymerized in the course of transport in belt direction,
and the solid
gel can be removed at the other end of the belt.
The gel obtained is preferably comminuted and dried after the polymerization.
The dry-
ing should preferably be effected at temperatures below 100 C. To prevent
conglutina-
tion, it is possible to use a suitable separating agent for this step. This
gives the hydro-
phobically associating copolymer as granules or powder.
Further details of the performance of a gel polymerization are disclosed, for
example, in
DE 10 2004 032 304 Al, paragraphs [0037] to [0041].
The inventive copolymers preferably possess a number-average molecular weight
Mn
of 50 000 to 25 000 000 g/mol.
Since the polymer powder or granules obtained are generally used in the form
of an
aqueous solution in the course of application at the site of use, the polymer
has to be
dissolved in water on site. This may result in undesired lumps with the high
molecular
weight polymers described. In order to avoid this, it is possible to add an
assistant
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which accelerates or improves the dissolution of the dried polymer in water to
the in-
ventive polymer as early as in the course of synthesis. This assistant may,
for example,
be urea.
Use of the water-soluble hydrophobically associating copolymer
The hydrophobically associating copolymer can, as already mentioned at the
outset, be
used in accordance with the invention for thickening of aqueous phases.
The selection of the type and amount of the monomers (a), (b), (c) and (d) can
be used
to adjust the properties of the copolymers to the particular technical
requirements.
The use concentration is determined by the person skilled in the art according
to the
type of aqueous phase to be thickened and the type of the copolymer. In
general, the
concentration of the copolymer is 0.05 to 5% by weight based on the aqueous
phase,
preferably 0.1 to 2% by weight and more preferably 0.15 to 1% by weight.
The aqueous phases to be thickened are, as already mentioned above, for
example,
formulations for hydraulic fracturing, completion fluids, spacer fluids and
drilling fluids,
and also aqueous formulations to generate foam.
The copolymers can be used here alone, or else in combination with other
thickening
components, for example together with other thickening polymers. They can also
be
formulated, for example, together with surfactants to give a thickening
system. The
surfactants can form micelles in aqueous solution, and the hydrophobically
associating
copolymers can form, together with the micelles, a three-dimensional
thickening net-
work.
For use, the copolymer can be dissolved directly in the aqueous phase to be
thickened.
It is also conceivable to predissolve the copolymer and then to add the
solution formed
to the system to be thickened.
The examples which follow are intended to illustrate the invention in more
detail and
with reference to the accompanying drawings. Herein:
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Fig. 1 shows a graphical representation of the viscosity of an aqueous
solution of a
copolymer according to the invention over temperature,
Fig. 2shows a graphical representation of rheological data measured at 300
rpm,
Fig. 3shows a graphical representation of rheological data measured at 3 rpm,
Fig. 4shows a graphical representation of foam buildup data on a SITA foam
tester,
Fig. 5shows a graphical representation of foam collapse data on a SITA foam
tester,
Fig. 6shows a graphical representation of Fann-35 data measured in HCO2Na
brine,
Fig. 7 shows a graphical represent. of Fann-35 data measured in CaCl2/CaBr2
brine,
Fig. 8shows a graphical representation of Fann-35 data measured in CaBr2
brine.
Examples
1. Preparation process
1.1 Preparation example 1 (comparative): without addition of surfactant
during the
polymerization
A 3 I vessel with stirrer and thermometer is initially charged with 242.5 g of
a 50% Na-
AMPS solution (AMPS 2405, from Lubrizol). 295.8 g of water were added while
stir-
ring. Subsequently, 1.2 g of Surfynol DF 58 and 0.4 g of Baysilone EN (from
Bayer) as
defoamers were added successively. After addition of 4.6 g of Pluriol
A1190V+12Pe0
(development product from BASF consisting of hydroxybutyl vinyl ether having
25 eth-
ylene oxide units and 12 pentene oxide units), 228.8 g of a 50% acrylamide
solution
(from Cytec) were added. After addition of 2.4 g of a 5% Versenex solution to
destabi-
lize the acrylamide solution, the pH was adjusted to 6.0 with a 20% NaOH
solution
and/or a 20% H2SO4 solution. During the inertization by purging with nitrogen
for 30
minutes, the solution was cooled to approx. 20 C. Subsequently, the solution
was
transferred to a plastic vessel of dimensions (w*d*h) 15cm*10cm*20cm, and 16.0
g
(200 ppm) of 10% 2,2'-azobis(2-amidinopropane) dihydrochloride, 0.5 g (10 ppm)
of
1% bisulphite solution, 8 g (6 ppm) of 0.1% tert-butyl hydroperoxide solution
and 4.09
(5 ppm) of 1% iron(II) sulphate solution were added successively.
The polymerization was initiated by irradiating with UV light (two Philips
tubes; Cleo
Performance 40 W). After approx. 2-3 h, the cut-resistant gel was removed from
the
plastic vessel and cut with scissors into gel cubes of approx. 5 cm * 5 cm * 5
cm in
size. Before the gel cubes were comminuted with a conventional meat grinder,
they
were lubricated with the separating agent Sitren 595 (polydimethylsiloxane
emulsion;
from Goldschmidt). The separating agent is a polydimethylsiloxane emulsion
which has
been diluted 1:20 with water.
20
The gel granules obtained were subsequently distributed homogeneously on
drying
grids and dried to constant weight under reduced pressure at approx. 90-120 C
in a
forced-air drying cabinet. Approx. 500 g of white hard granules were obtained,
which
were converted to a pulverulent state with the aid of a centrifugal mill.
1.2 Preparation examples 2-4 (inventive): with surfactant addition during the
gel po-
lymerization
In addition to the monomer solution as described in comparative example 1, the
surfac-
tant Lutensol TO15 (from BASF, C13-oxo alcohol ethoxylate + 15 ethylene oxide
units)
was dissolved in the following amounts in the monomer solution before the
polymeriza-
tion:
Preparation ex. 2: 1% LutensolTm TO15 (corresponds to 2.4 g)
Preparation ex. 3: 2% LutensolTm T015 (corresponds to 4.8 g)
Preparation ex. 4: 3% LutensolTM T015 (corresponds to 7.2 g)
1.3 Preparation examples 5-10 (inventive)
Proceeding from preparation ex. 3, the following polymers were produced with
alterna-
tive surfactants to LutensolTM TO15 (measurement of the viscosity as described
in use
ex. 1):
Viscosity
Surfactant
[mPa*s]
Preparation ex. 3 2% LutensolTmT0 15 (C13-oxo alcohol ethoxylate + 15 EO)
230
Preparation ex. 5 2% Lutensolm AP 10 (alkylphenol + 10 EO) 390
Preparation ex. 6 2% LutensolTm XL100 (Cio-Guerbet alcohol +10 EO) 140
Preparation ex. 7 2% LutensolTM XP100 (Cio-Guerbet alcohol+10 ED) 80
Preparation ex. 8 2% sodium dodecylsulphonate (SDS) 100
Preparation ex. 9 2% dodecyltrimethylammonium chloride 150
Preparation ex. 10 2% LutensolTmT0 10 (C13-oxo alcohol ethoxylate + 10 EO)
270
As can be seen from the data, not only LutensolTM but also other nonionic
surfac-
tants, and also anionic and cationic surfactants, can be used in the synthesis
of the
inventive copolymers.
1.4 Preparation example 11 (inventive)
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In analogy to preparation example 3, a copolymer was produced with an
alternative
water-soluble hydrophobically associating monomer to Plurioln4A1190V+12Pe0.
This
monomer consists of a C12-alcohol ethoxylated with 7 EO, which was
subsequently
reacted with methacrylic anhydride (GenagenTM LA070MA from ClariantTm). The
mass of
the GenagenTM used corresponds to that of the PluriolTM A1190V+12Pe0 in
preparation ex.
3.
The measurement of the viscosity as in use ex. 1 gave a value of 780 mPas.
This
preparation example shows that different water-soluble hydrophobically
associating
monomers can be used.
1.5 Preparation example 12 (inventive)
In analogy to preparation example 3, a mixed ionic copolymer was produced.
This co-
polymer contains, in addition to AMPS , acrylamide and PIurioITM A1190V+12PeO,
the
cationic monomer 3-trimethylammoniopropylmethacrylamide chloride (DIMAPAQUAT).
The molar ratio of the monomers is AMPS :acrylamide:DIMAPAQUAT:Plurioirm
Al 190V+12Pe0 = 30:37:32:1. The measurement of the viscosity as described in
use
ex. 1 gave a value of 56 mPas.
1.6 Preparation example 13 (inventive)
In analogy to preparation example 3, a copolymer which contains, instead of
4.6 g of
PIurioITM A1190V+12PeO, the same molar amount of PlurioITM A1190V+16Pe0
(develop-
ment product from BASFInnsisting of hydroxybutyl vinyl ether with 25 ethylene
oxide
units and 16 pentene oxide units) was produced. The measurement of the
viscosity as
described in use ex. 1 gave a value of 77 mPas.
1.7 Preparation example 14 (inventive)
In analogy to preparation example 3, a copolymer which contains, instead of Na-
AM PS , the sodium salt of acrylic acid was produced. The proportions by mass
of the
monomers were 28% sodium acrylate, 70% acrylamide and 2% PluriolTM
A1190V+12PeO. The surfactant added was 4.89 of Lutensolim AP10 (BASrm). The
solids
content of the polymerized gel was 19.5%. The measurement of the viscosity as
de-
scribed in use ex. 1 gave a value of 49 mPas.
1.8 Preparation example 15 (inventive)
In analogy to preparation example 3, a copolymer in which the Na-AMPS has
been
partly replaced by the sodium salt of acrylic acid was produced. The
proportions by
mass of the monomers were 28% AMPS , 20% sodium acrylate, 50% acrylamide and
2% PuriolTM Al 190V+12 Pe . The surfactant added was 4.8 g of LutensolTM T015
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(BASF). The measurement of the viscosity as described in use ex. 1 gave a
value of 40
mPas.
1.9 Preparation example 16 (inventive)
This example describes an alternative polymerization process to preparation
example
5.
A plastic bucket with magnetic stirrer, pH meter and thermometer was initially
charged
with 121.2 g of Na-AMPS (50% solution) to which were subsequently added 155
g of
distilled water, 0.6 g of Surfynol, 0.2 g of Baysilone, 2.3 g of Pluriol All
90V + 12 PeO,
114.4 g of acrylamide (50% solution), 1.2 g of Versenex (5% solution) and 2.4
g of
Lutensol AP10. After adjustment to pH 6.0 with a 20% or 2% sulphuric acid
solution
and addition of the rest of the water (total amount of water minus the amount
of water
already added, minus the amount of acid required), the monomer solution was
adjusted
to the start temperature of 20 C. The solution was transferred into a thermos
flask, the
temperature sensor for temperature recording was mounted and the mixture was
purged with nitrogen for 30 minutes. At the end of the nitrogen purging, the
online
measurement of the temperature was started, the start temperature was checked
once
more and adjusted, and 1.6 ml of a 10% V50 solution, 0.12 ml of a 1% t-BHPO
solution
and 0.24 ml of a 1% sodium sulphite solution were added successively. As the
mono-
mer solution began to thicken, the nitrogen frit was removed from the monomer
solu-
tion. Once the temperature of the gel block had attained its maximum, the
temperature
sensor was removed and the thermos flask was placed into a drying cabinet at
80 C for
two hours. Thereafter, the gel block was removed from the thermos flask and
approx.
0.5-1 cm of the surface was removed with scissors and discarded. The remainder
was
halved, painted with the separating agent Comperlan COD (coconut fatty acid
dietha-
nolamide) and comminuted with the aid of a meat grinder. The gel granules
obtained
were dried in a fluidized bed dryer at 55 C for two hours. This gave white
hard granules
which were converted to a pulverulent state by means of a centrifugal mill.
1.10 Preparation example 17 (inventive)
Analogous to preparation example 16, but with use of 6 g of Pluriol A1190V +
12 Pe0
and 6 g of Lutensol AP10.
2. Properties of the copolymer
2.1 Analysis 1
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The polymers of preparation examples 1-4 were dissolved in synthetic seawater
to DIN
50900 (salt content 35 g/l), such that a polymer concentration of 4000 ppm was
at-
tained. The viscosity of these solutions was measured on a Haake rheometer
with a
double slit geometry at 7-1 and60 C.
Viscosity
Polymer
[mPa*s]
Preparation ex. 1 24
Preparation ex. 2 360
Preparation ex. 3 230
Preparation ex. 4 80
It is clear that the addition of the Lutensol TO 15 during the polymerization
significantly
increases the viscosity of the polymers. In addition, the amount of surfactant
added has
a clear influence on the viscosity.
2.2 Analysis 2
In order to show that the inventive polymers are not merely a physical mixture
of the
polymer from preparation ex. 1 and the surfactant, but that the polymer
structure is cru-
cially influenced during the polymerization reaction, the viscosities of
mixtures of the
polymer from preparation ex. 1 with the surfactant Lutensol TO 15 were also
meas-
ured:
Viscosity Viscosity of the mixture of preparation ex. 1
with the cor-
[mPas] responding amount of Lutensol TO 15 [mPas]
Preparation ex. 2 360 25
Preparation ex. 3 230 26
Preparation ex. 4 80 20
As can be seen from these analyses, a subsequent addition of the surfactant
does not
have any positive influence on the viscosity of the polymer.
For more detailed examination of the mechanism of action, the polymer from
prepara-
tion example 3 was refluxed in a Soxhlet with toluene over a period of 48 h.
This ex-
tracted 90% of Lutensol TO 15 originally present from the copolymer. However,
the
high viscosity of the polymer was preserved even after the virtually complete
extraction
of the surfactant.
This indicates that the surfactant is not incorporated or grafted covalently
into the co-
polymer, but rather that the addition of surfactant positively influences the
formation of
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the polymer structure. This could be rationalized in that the surfactant forms
mixed mi-
celles with the hydrophobically associating monomer.
2.3 Analysis 3
1 g of the particular copolymer of preparation examples 1-4 was stirred into
249 g of
synthetic seawater to DIN 50900 (salt content 35 g/I) for 24 h until complete
dissolution.
Subsequently, the solution was filtered through a screen with mesh size 200 pm
and
the volume of the residue remaining on the screen was measured. The value
obtained
corresponds to the gel content.
Gel content
Polymer
[ml]
Preparation ex. 1 (comparative) 45
Preparation ex. 2 (inventive) 9
Preparation ex. 3 (inventive) 5
Preparation ex. 4 (inventive) < 1
As can be seen from the data, the gel content is reduced significantly as a
result of the
surfactant addition. With rising amount of surfactant, it is possible to
reduce the gel
content down to below the detection limit.
2.4 Use example 1 (inventive)
Fig. 1 shows the profile of the viscosity of an aqueous solution of
preparation example
16 (c = 1200 ppm in 9% salt solution, measured at 6 rpm with Brookfield LV and
UL
adapter). In the case of a temperature rise from 20 to 30 C, a small decline
in viscosity
is observed at first, then the viscosity rises significantly and passes
through a maxi-
mum in the region of 50-60 C, in order then to decrease continuously as the
tempera-
ture rises further.
3. Use as a thickener in hydraulic fracturing
3.1 Use example 2 (comparative)
The table below shows the rheological properties of a 0.6% solution of
hydroxypropyl-
guar (Jaguar HP-8, from Rhodia) at different temperatures and speeds
(measured at
Fann 35).
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Solvent Temperature Fann 35 values
[lb/100 sqf] at ... rpm
[ F] 300 200 100 6 3 600
Tap water 80 51 44 34 11 8 65
140 42 35 27 8 4 50
190 33 29 21 4 2 43
Seawater 80 50 42 33 10 8 64
140 38 32 24 6 3 48
190 27 21 14 2 0 35
3.2 Use example 3 (comparative)
5
The table below shows the rheological properties of a 0.6% solution of
hydroxypropyl-
guar (Galctasol 40H4FDS1, from Ashland Aqualon) at different temperatures and
speeds (measured with Fann 35).
Solvent Temperature Fann 35 values
[lb/100 sqf] at ... rpm
[ F] 300 200 100 6 3 600
Tap water 80 39 32 24 6 4 Si
140 29 24 18 3 2 38
190 24 19 14 2 1 32
Seawater 80 44 37 28 6 3 60
140 36 30 22 4 2 47
190 29 24 18 3 2 37
3.3 Use example 4 (comparative)
The table below shows the rheological properties of a 0.6% solution of
carboxymethyl-
hydroxypropylguar (Galctasoll') 60H3FDS, from Ashland Aqualon) at different
tempera-
tures and speeds (measured with Fann 35).
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Solvent Temperature Fann 35 values
[lb/100 sqf] at ... rpm
[ F] 300 200 100 6 3 600
Tap water 80 44 37 29 9 6 56
140 39 33 25 5 3 47
190 28 24 17 3 2 36
Seawater 80 54 47 37 12 8 69
140 41 36 28 8 4 51
190 33 28 21 3 2 41
3.4 Use example 5 (inventive)
The table below shows the rheological properties of a 0.6% solution of
preparation ex-
ample 16 at different temperatures and speeds (measured with Fann 35).
Solvent Temperature Fann 35 values
[lb/100 sqf] at ... rpm
[ F] 300 200 100 6 3 600
Tap water 80 71 67 50 17 12 108
140 73 60 45 17 13 91
190 70 56 41 18 14 78
Seawater 80 35 27 17 3 2 49
140 40 33 26 10 8 47
190 37 27 17 7 5 41
3.5 Use example 6 (inventive)
The table below shows the rheological properties of a 0.6% solution of
preparation ex-
ample 2 at different temperatures (measured with Fann 35).
Solvent Temperature Fann 35 values
[lb/100 sqf] at ... rpm
[ F] 300 200 100 6 3 600
Tap water 80 95 72 50 20 13 119
27
140 70 65 51 20 17 85
190 79 66 53 27 24 92
Seawater 80 35 28 18 4 3 51
140 65 56 48 20 14 64
190 45 32 28 11 9 55
To illustrate the above data, the values measured at 300 rpm and 3 rpm in tap
water
were summarized in Fig. 2 and Fig. 3, respectively.
As can be seen from Figs. 2 and 3, the viscosity values of the inventive
copolymers at
room temperature are firstly higher than those of the commercial polymers used
to
date; secondly, no significant decline in viscosity is observed with rising
temperature,
and it is even possible to observe a rise at the low shear rates.
The comparatively high viscosity values at the low shear rates are
particularly advanta-
geous for use as a thickener in hydraulic fracturing, since proppants are
generally
pumped together with the polymer solution in this use. Thus, settling of these
prop-
pants is prevented.
4. Use as a thickener or stabilizer for foams
4.1 Use example 7 (inventive)
350 g of tap water were weighed into a beaker. 1 g of the polymer from
preparation
example 17 was added while stirring, the mixture was stirred at 400 rpm for 30
min,
then the stirrer was switched to approx. 200 rpm, and the mixture was left to
stir over-
night. 300 g of this mixture were introduced into the glass container of a
WaringTm
blender. 0.125% (0.38 g) of foaming agent (LutensolTM GD 70, alkyl
polyglucoside, from
BASFTM) was added and the mixture was stirred in the \ivaringTM blender at 12
000 rpm for
15 sec. 60 g of this foam were weighed into a plastic bottle and made up to a
total of
300 g with tap water (20% dilution). This mixture was then analyzed on an
SITATm foam
tester.
4.2 Use example 8 (comparative)
350 g of tap water were weighed in, and 3.5 g of Jaguar HP 8
(hydroxypropylguar,
from Rhodia) were added while stirring in a Hamilton BeachTM mixer. This was
followed
by stirring at the "low speed" setting for 20 min. 300 g of this mixture were
introduced
into the glass container of a Waring TM blender, 0.125% (0.38 g) of foaming
agent (Luten-
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sol GD 70, alkyl polyglucoside, from BASF) were additionally added, and the
mixture
was stirred at 12 000 revolutions on the Waring blender for 15 sec. 60 g of
this foam
were weighed out into a plastic bottle and made up to 300 g with tap water
(20% dilu-
tion). This mixture was then likewise analysed on an SITA foam tester.
The test parameters of use examples 7 and 8 are reproduced in the table below,
and
the results are given in form of graphical representations in Fig 4 (foam
buildup).and
Fig. 5 (foam collapse).
SITA foam tester ¨ test parameters
Parameter:
V (Sample): 250 ml
N (Rotor): 2000 R/min T (Sample): 20.0 C 0.5 K
t (Stir): 15 s Cleaning: short
It appears from Fig. 4 that, in order to achieve an equally good foam
structure as com-
pared to that with the commercial Jaguar HP 8 thickener, only 1 ppb ("pound
per bar-
rel") of the inventive copolymer is needed instead of 3.5 ppb.
Moreover, it appears from Fig. 5 that the foam collapse in the case of use of
the inven-
tive copolymer is much slower and more homogeneous than with the commercial
Jag-
uar HP thickener.
5. Thickener for drilling muds
The tests were performed according to API RP 131 "Recommended Practice for
Labo-
ratory Testing of Drilling Fluids".
5.1 Use example 9:
350 ml of distilled water were introduced into a 600 ml beaker. A stirrer with
stirrer shaft
was clamped into the precision glass stirrer and immersed into the beaker. The
stirrer
was set to 300 rpm and the polymer was added slowly. The stirrer was throttled
to
200 rpm after approx. 30 min; the mixture was stirred for a further 17 hours.
Subse-
quently, the rheology and the pH of the solution were measured.
Thereafter, the solution was introduced into an ageing cell. The cell was
vented and
subjected to ageing in a roller kiln for 16 hours (temp.: 250 F, pressure: 250
psi). After
the ageing, the rheology was analysed again. The results are reproduced in the
table
below.
Polymer ppb Fann-35 before ageing PV YP Fann-35 after ageing PV YP
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600-300-200-100-6-3 600-300-200-100-6-3
Prep. Ex. 16 1.0 43-30-28-20-7-6 13 17 34-25-23-
17-5-4 9 16
1.5 68-58-41-31-13-10 10 48 49-37-31-24-7-5 12 25
Prep. Ex. 17 1.0 72-53-44-34-14-11 19 34 40-29-25-
18-5-4 11 18
1.5 114 86 73 57 24 20 28 58 66-48-40-30-9-6 18 30
8 parts of Ex.16 1.5 80-57-48-37-15-12 23 34 50-
38-33-25-8-6 12 26
2 parts of Ex.17
Biovis 1.0 17-13-12-9-5-4 4 9 10-
6-4-3-1-1 4 2
'
1.5 23-18-15-12-7-6 5 13 21-14-12-9-4-4 8 6
1.0 16-12-10-8-4-4 4 8 4-2-1-0-0-0 2 0
Xanthan
1.5 23-18-16-13-7-6 5 13 4 3 1 0 0 0 1 2
The inventive polymers have a higher viscosity at the same dosage compared to
Bio-
vis (Scleroglucan, from BASF) and particularly compared to Xanthan (Bioflow ,
from
BASF), especially after ageing. It is also of interest that flatter rheology
can be
achieved with a mixture of the two inventive polymers.
6. Use in completion fluids
6.1 Use example 10
The inventive polymer from preparation example 16 was tested in 4 different
high-den-
sity salt solutions ("brines") which are used as solids-free completion
fluids:
Brine 1:
56% by weight of tap water
24% by weight of CaBr2
20% by weight of CaCl2
Density: 1.456 g/ml
Brine 2:
40.2% by weight of tap water
59.8% by weight of CaBr2
Density: 1.774 g/ml
Brine 3:
58% by weight of tap water
42% by weight of CaCl2
Density: 1.351 g/ml
Brine 4:
59.4% by weight of tap water
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40.6% by weight of sodium formate
Density: 1.257 g/ml
The inventive polymers were added as a 1.75% solution to the particular
brines, and
5 the viscosity of the resulting completion fluid was determined with the
Fann-35 at room
temperature. The completion fluids were aged dynamically in a roller kiln at
the particu-
lar temperatures specified for 16 hours. Subsequently, the liquid was cooled
to RT and
determined again with the Fann-35.
10 To prepare the 1.75% polymer solution (1.75 g of polymer + 98.25 g of
water), water
was initially charged in an H BM container on an 1KA stirrer, the polymer was
added and
the mixture was stirred at 1100 rpm for 1 h. To prepare the completion
solutions, 200 g
of a 1.75% polymer solution and 200 g of brine were weighed into an HBM
container
and stirred at 1100 rpm for 30 min. The density was determined and the
rheology was
15 measured. The mixture was left to age in the roller kiln at the
particular temperature for
16 h, and then the ageing cell was cooled in a water bath. The mixture was
stirred
briefly with a spatula and the rheology was measured again at room
temperature. The
results are shown Fig. 6 (sodium formate brine with a density of 1.11 g/ml),
Fig. 7
(CaC12/CaBr2 brine with a density of 1.19 g/ml) and Fig. 8 (CaBr2 brine with a
density of
20 1.16 g/ml). These graphical representations show clearly that the
inventive copolymer
can be used as a thickening rheological additive for completion fluids.
