Note: Descriptions are shown in the official language in which they were submitted.
PF 72130 CA 02826635 2013-08-06
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Process for producing mineral oil from underground formations
The present invention relates to a process for producing mineral oil from
underground
formations, wherein, in one process step, permeable regions of the underground
formation are
blocked by injecting aqueous formulations of hydrophobically associating
copolymers into the
formation.
In natural mineral oil deposits, mineral oil occurs in the cavities of porous
reservoir rocks which
are closed off from the surface of the earth by impervious covering layers.
The cavities may be
very fine cavities, capillaries, pores or the like. Fine pore necks may, for
example, have a
diameter of only approx. 1 ji.m. The underground formation may additionally
also have regions
with pores of greater diameter and/or natural fractures. In addition to
mineral oil, including
proportions of natural gas, a deposit generally comprises water with a greater
or lesser salt
content.
After a well has been sunk into the oil-bearing strata, mineral oil at first
flows to the production
wells owing to the natural deposit pressure, and is flushed to the surface of
the earth. This
phase of mineral oil production is known by the person skilled in the art as
primary production.
However, flush production generally ceases very rapidly, especially under poor
deposit
conditions, for example a high oil viscosity, rapidly declining deposit
pressure or high flow
resistances in the oil-bearing strata. With primary production, it is possible
to produce an
average of only 2 to 10% of the oil originally present in the deposit. In the
case of higher-
viscosity mineral oils, flush production is generally completely impossible.
In order to enhance the mineral oil yield, what are known as secondary and
optionally tertiary
production processes are therefore used.
One secondary mineral oil production process is called "water flooding". For
this purpose, the
deposit is provided with one or more injection wells in addition to the
production wells, i.e. the
wells through which mineral oil is withdrawn from the mineral oil formation.
Water is injected into
the oil-bearing strata through the injection wells. This artificially
increases the deposit pressure
and forces the oil from the injection wells in the direction of the production
wells. Water flooding
can significantly enhance the exploitation level. Instead of water, it is also
possible to inject
steam into the deposit ("steam flooding"). This is advisable especially when
the deposit
comprises high-viscosity oils.
In the course of water flooding, in the ideal case, a water front proceeding
from the injection well
should force the oil homogeneously over the entire mineral oil formation to
the production well.
In practice, a mineral oil formation, however, has regions with different
levels of flow resistance.
In addition to fine-porosity, oil-saturated reservoir rocks with a high flow
resistance to water,
there also exist regions with a low flow resistance to water, for example
natural or synthetic
fractures or very permeable regions in the reservoir rock. The permeable
regions may also be
already exploited regions. In the course of water flooding, the flooding water
injected naturally
PF 72130 CA 02826635 2013-08-06
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flows principally through flow paths with low flow resistance from the
injection well to the
production well, while there is at least slower flow, if any, of water through
the fine-porosity, oil-
saturated deposit regions with high flow resistance. The water thus no longer
flows
homogeneously through the formation, and the water front is instead very
irregular (called
"fingering"), and an increasing amount of water and a decreasing amount of
mineral oil are
produced via the production well. In this connection, the person skilled in
the art refers to
"watering out of production". The effects mentioned are particularly marked in
the case of heavy
and viscous mineral oils. The higher the mineral oil viscosity, the more
probable is rapid
watering out of production. The problem occurs especially in the presence of
fissured rock
formations (called "fractured reservoirs").
There also exist mineral oil formations in which a water-bearing stratum is
arranged below an
oil-bearing stratum. In the course of drilling into such a formation, not only
mineral oil but also
water is produced, and so production here too is significantly watered out.
There has been no lack of attempts to prevent the inhomogeneous flow of water,
or at least to
achieve more homogeneous flow. In the prior art, there are therefore known
measures for
closing such highly permeable zones between the injection wells and production
wells by
means of suitable measures, or at least for reducing the permeability thereof.
As a result, the
flooding water or flooding steam is forced again to flow through the oil-
saturated, low-
permeability strata, and further mineral oil can thus again be mobilized. Such
measures are also
known as "conformance control" or "water shut-off'. An overview of conformance
control
measures is given by Boiling et al. "Pushing out the oil with Conformance
Control" in Oilfield
Review (1994), pages 44 if
For blocking of highly permeable regions of underground formations, i.e. for
conformance
control, it is possible to use comparatively low-viscosity formulations of
particular chemical
substances which can be injected readily into the formation, and the viscosity
of which rises
significantly only after injection into the formation, under the conditions
which exist in the
formation. Such formulations comprise inorganic, organic or polymeric
components suitable for
increasing viscosity. The rise in viscosity of the injected formulation can
occur, for example, with
a simple time delay, and/or the rise in viscosity can be triggered by the
temperature rise when
the injected formulation in the deposit gradually heats up to the deposit
temperature.
Formulations whose viscosity rises only under formation conditions are known,
for example, as
"thermogels" or "delayed gelling systems".
SU 1 654 554 Al discloses a process for producing oil using mixtures of
aluminum chloride or
aluminum nitrate, urea and water, which are injected into the mineral oil
formation. The
formulations naturally flow preferably along the flow paths with the lowest
flow resistance. At the
elevated temperatures in the formation, the urea is hydrolyzed to carbon
dioxide and ammonia.
The release of the ammonia base significantly increases the pH of the water,
and a high-
viscosity gel of aluminum hydroxide precipitates out, which blocks the highly
permeable zones.
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US 2008/0035344 Al discloses a mixture for blocking of underground formations
with retarded
gelation, which comprises at least one acid-soluble, crosslinkable polymer,
for example partly
hydrolyzed polyacrylamide, a partly neutralized aluminum salt, for example an
aluminum
hydroxide chloride, and an activator which can release bases under formation
conditions, for
example urea, substituted ureas or hexamethylenetetramine. The mixture can
preferably be
used at a temperature of 0 to 40 C and gelates at temperatures above 50 C,
according to the
use conditions, within 2 h to 10 days.
RU 2 361 074 discloses a process for blocking highly permeable zones, in which
portions of
formulations based on urea and aluminum salts are injected into a deposit with
high deposit
temperature.
US 4,182,417, US 2007/0204989, WO 2007/126318 Al and WO 2010/069607 Al
disclose
water-swellable particles for blocking of underground formations. These
particles can be
injected in a suitable formulation into the underground formation, swell in
the formation under
the influence of the formation water and in this manner block highly permeable
regions of the
formation.
R. D. Sydansk "Acrylamide-Polymer/Chromium(III)-Carboxylate Gels for Near
Wellbore Matrix
Treatments"in Proceedings Society of Petroleum Engineers / US Department of
Energy, 70,
Symposium on Enhanced Oil Recovery, April 22- 25, 1990, Tulsa, Oklahoma,
SPE/DOE 20214,
Society of Petroleum Engineers, 1990 disclose acrylamide-chromium(l II)
carboxylate gels for
blocking of underground formations. For this purpose, acrylamide and Cr(III)
carboxylates, for
example Cr(III) acetate, are injected into the formation. Under the formation
conditions, amide
groups of the polymer are hydrolyzed to carboxylate groups. The Cr(III)
carboxylate then
crosslinks carboxylate groups of different polymer strands, thus forming a
viscous gel.
US 4,613,631 discloses gels formed from crosslinked polymers for blocking of
underground
formations. The polymers may, for example, be polyacrylamide, polyacrylic
acids, or else
biopolymers, for example xanthogenates. The crosslinkers used are organic
compounds which
have at least two positively charged nitrogen atoms.
US 7,150,319 62 discloses a process for blocking underground formations, in
which a
copolymer comprising 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, a
further
nitrogen-containing monomer, for example N-vinylformamide or N-
vinylpyrrolidone, and
vinylphosphonic acid as monomers. The copolymer is crosslinked with compounds
of
chromium, zirconium, titanium or aluminum to form a viscous gel.
US 6,803,348 B2 discloses a process for reducing water production from mineral
oil-bearing
underground formations, in which water-soluble, hydrophobically associating
copolymers
comprising a linear hydrophilic main chain, hydrophobic side groups and
functional groups
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which can be used for crosslinking are used. The water-soluble copolymers are
injected into the
underground formation and crosslinked therein, for example by means of Cr(III)
ions, Zr(IV) ions
or aldehydes. The polymers are preferably based on polyacrylamides. The
hydrophobic groups
are preferably alkyl groups having at least 6, preferably at least 8 and more
preferably at least
12 carbon atoms. The copolymer may comprise, for example, N-alkylacrylamides,
for example
N-decylacrylamide, as a monomer.
WO 2010/133527 A2 discloses hydrophobically associating copolymers which
comprise at least
hydrophilic, monoethylenically unsaturated monomers, for example acrylamide,
and
monoethylenically unsaturated, hydrophobically associating monomers. The
hydrophobically
associating monomers have a block structure and have ¨ in this sequence ¨ an
ethylenically
unsaturated group, optionally a linking group, a first polyoxyalkylene block
which comprises at
least 50 mol% of ethyleneoxy groups, and a second polyoxyalkylene block which
consists of
alkyleneoxy groups having at least 4 carbon atoms. The application discloses
the use of such
copolymers as thickeners, for example for polymer flooding, for construction
chemical
applications, or for detergent formulations.
WO 2011/015520 Al discloses a process for preparing hydrophobically
associating copolymers
by polymerizing water-soluble, monoethylenically unsaturated, surface-active
monomers and
monoethylenically unsaturated hydrophilic monomers in the presence of
surfactants, and the
use of such copolymers for polymer flooding.
Our prior applications EP 10192323.3, EP 10192334.0 and EP 10192316.7 disclose
the use of
the hydrophobically associating copolymers disclosed in WO 2010/133527 A2 in
specific
processes for polymer flooding.
However, none of the latter cited applications discloses the use of such
hydrophobically
associating copolymers for blocking of underground mineral oil-bearing
formations.
It was an object of the invention to provide an improved process for blocking
of highly
permeable regions of mineral oil-bearing formations.
Accordingly, a process has been found for producing mineral oil from
underground mineral oil
deposits, which comprises at least the following process steps:
(1) blocking permeable regions of the underground mineral oil deposit by
injecting an
aqueous formulation into the formation through at least one well, said aqueous
formulation comprising at least one water-soluble, hydrophobically associating
copolymer, and
(2) injecting an aqueous flooding medium into at least one injection well
and
withdrawing mineral oil through the at least one production well,
5
and wherein
= the water-soluble, hydrophobically associating copolymer comprises
(a) 0.1 to 15% by weight of at least one monoethylenically unsaturated,
hydrophobically
associating monomer (a) selected from the group of
H2C=C(R1)-R2-0-(-CH2-CH(R3)-0-)k+CH2-CH(R4)-0-)I-R6 (I),
H2C=C(R1)-0+CH2-CH(R3)-0-)k-R6 (II),
H2C=C(R1)-(C=0)-0-(-CH2-CH(R3)-0-)k-R6 (Ill),
where the -(-CH2-CH(R3)-0-)k and -(-CH2-CH(R4)-0-)i units are arranged in
block
structure in the sequence shown in formula (I) and the radicals and indices
are
each defined as follows:
k: a number from 10 to 150,
I: a number from 5 to 25,
R1: H or methyl,
R2: a single bond or a divalent linking group selected from the group of -
(CnH2
J,
n)-
[R2al 0-(Crif120- [R29 and ¨C(0)-0-(Cn-1-120- [R2c], where n, n' and n" are
each natural numbers from 1 to 6,
R3: each independently H, methyl or ethyl, wherein at least 50 mol% of the R3
radicals are H,
R4: each independently a hydrocarbyl radical having at least 2 carbon atoms or
an ether group of the general formula ¨CH2-0-R4', where R4' is a hydrocarbyl
radical having at least 2 carbon atoms,
R5: H or a hydrocarbyl radical having 1 to 30 carbon atoms,
R6: an aliphatic and/or aromatic, straight-chain or branched hydrocarbyl
radical
having 8 to 40 carbon atoms,
and also
(b) 85 to 99.9% by weight of at least two monoethylenically unsaturated
monomers (b)
different than (a), where the monomers (b) comprise
(b1) at least one uncharged, monoethylenically unsaturated, hydrophilic
monomer (b1), selected from the group of (meth)acrylamide,
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N-methyl(meth)acrylamide, N,N'-dimethyl(meth)acrylamide or
N-methylol(meth)acrylamide, and
(b2) at least one monomer (b2a) and/or (b2b), where the monomers (b2a) and
(b2b) are defined as follows:
(b2a) anionic, monoethylenically unsaturated, hydrophilic monomers which
have at least one acidic group selected from the group of -COOH,
-S03H and ¨P03H2 and salts thereof,
(b2b) (meth)acrylic esters of the general formula H2C=C(R16)-000R16
where R16 is H or methyl and R16 is a straight-chain or branched alkyl
radical having 1 to 8 carbon atoms, wherein the amount of the
monomers (b2b), if present, does not exceed 20% by weight,
where the proportions are each based on the total amount of all monomers in
the
copolymer,
= the copolymer has a weight-average molecular weight Mw of 0.5*106 g/mol
to
30*106 g/mol,
= the amount of the copolymer in the aqueous formulation is 0.1 to 3% by
weight, and
= the deposit temperature is 20 C to 120 C,
= and where the formulation further comprises water-soluble components
which
produces crosslinking of the polymer under deposit conditions, and the
temperature of
the aqueous copolymer formulation to be injected is selected such that it is
lower than
the deposit temperature.
With regard to the invention, the following should be stated specifically:
The process according to the invention comprises at least two process steps,
(1) and (2).
In process step (1), permeable regions of the underground mineral oil deposit
are blocked by
injecting an aqueous formulation through at least one well sunk into the
formation, said aqueous
formulation comprising at least one water-soluble, hydrophobically associating
copolymer. The term
"blocking" means here that the permeable regions are completely or at least
partially blocked.
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"Partially blocked" is intended to mean that the flow resistance of the
permeable regions for
aqueous media increases due to the treatment with the aqueous formulation of
the copolymer. This
can occur, for example, as a result of the copolymer forming a gel in the
permeable regions of the
formation and blocking them, or it can occur as a result of the copolymer
forming a coating on the
inner surface of cavities in the formation and this constriction of the flow
paths increasing the flow
resistance in the permeable regions.
In process step (2), mineral oil is actually produced by injecting an aqueous
flooding medium into at
least one injection well and withdrawing mineral oil through at least one
production well.
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The injected aqueous flooding medium maintains the pressure and forces the
mineral oil from
the injection wells in the direction of the production wells.
The result of the performance of process step (1) here, i.e. the blocking of
permeable zones, is
that the flooding medium injected in process step (2) is forced also to flow
through less
permeable, as yet unexploited regions of the underground formation. As a
result, the mineral oil
yield is increased and water production is reduced.
Process steps (1) and (2) can also be performed more than once in the context
of the process
according to the invention, and the process according to the invention may of
course comprise
further process steps.
Deposits
The mineral oil deposits to which the process according to the invention is
applied may be
deposits for all kinds of oil, for example those for light or heavy oil.
In addition to mineral oil and possibly natural gas, the deposits generally
comprise deposit water
with a greater or lesser salt content. Typical salts in deposit waters
comprise especially alkali
metal salts and alkaline earth metal salts. Examples of typical cations
comprise Na, l<4., Mg2+
and Ca2+, and examples of typical anions comprise chloride, bromide,
hydrogencarbonate,
sulfate or borate. The process according to the invention is especially
suitable for deposits with
a total amount of all salts in the deposit water of 20 000 ppm to 350 000 ppm
(parts by weight),
preferably 100 000 ppm to 250 000 ppm. The amount of alkaline earth metal ions
in the deposit
water may especially be 1000 to 53 000 ppm.
The mineral oil deposits have inhomogeneous permeability. This is understood
to mean that the
permeability is not the same in all regions of the deposit, and that the
deposit instead has
regions of higher and lower permeability. Regions of higher permeability may
be caused, for
example, by the fact that the deposits have larger pores in this region, or
else by the fact that
the deposits have fractures, cracks, fissures or the like. In the course of
continued injection of
water into the formation to maintain the pressure, called water flooding, the
water injected, due
to the low flow resistance, flows preferentially through the regions of high
permeability.
The deposit may also have different rock layers of different permeability
arranged one on top of
another. For example, a deposit may comprise a comparatively permeable layer
essentially
comprising water, and a lower, less permeable layer comprising mineral oil.
The deposit temperatures (Ti.) are in the range from 20 C to 120 C, especially
30 C to 120 C,
preferably 35 C to 110 C, more preferably 40 C to 100 C, even more preferably
45 C to 90 C
and, for example, 50 C to 75 C. It will be clear to the person skilled in the
art that a mineral oil
deposit may also have a certain temperature distribution. The deposit
temperature mentioned
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relates to the region of the deposit between the injection and production
wells, i.e. the region
covered by process steps (1) and (2). The temperature distribution can
generally be undertaken
from temperature measurements at particular sites in the formation in
combination with
simulation calculations, the simulation calculations taking account of factors
including amounts
of heat introduced into the formation and the amounts of heat removed from the
formation.
To execute process step (1) of the process according to the invention, at
least one well is sunk
into the mineral oil deposit, through which the aqueous copolymer formulation
can be injected to
block permeable regions. This may be a well which has been sunk specially for
process step
(1). It is preferably an injection well and/or a production well which can
also be used for process
step (2) and/or has already been used in preceding water flooding.
To execute process step (2), at least one production well and at least one
injection well are
sunk into the mineral oil deposit. In general, a deposit is provided with
several injection wells
and with several production wells. Aqueous formulations can be injected into
the mineral oil
deposit through the at least one injection well, and the production wells
serve to withdraw
mineral oil from the mineral oil deposit. The term "mineral oil" in this
context does not of course
mean only single-phase oil, but instead the term also comprises the customary
crude oil-water
emulsions wherein the water may either be deposit water or injected water
which has
penetrated as far as the production well.
The wells which can be used for process step (1) may preferably be the
injection and/or
production wells which are also used for process step (2).
Process step (1)
In process step (1), an aqueous formulation comprising at least one water-
soluble,
hydrophobically associating copolymer is used. In addition to the at least one
copolymer, the
formulation may optionally comprise further components.
Hydrophobically associating copolymers used
The term "hydrophobically associating copolymers" is known in principle to
those skilled in the
art.
They comprise water-soluble copolymers which, as well as hydrophilic molecular
components,
have hydrophobic groups. In aqueous solution, the hydrophobic groups can
associate with
themselves or with other substances having hydrophobic groups due to
intermolecular forces.
This gives rise to a polymeric network joined by intermolecular forces, which
thickens the
aqueous medium.
In the ideal case, the copolymers used in accordance with the invention should
be miscible with
water in any ratio. According to the invention, however, it is sufficient when
the copolymers are
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water-soluble at least at the desired use concentration and at the desired pH.
In general, the
solubility in water at room temperature under the use conditions should be at
least 35 g/I.
According to the invention, the water-soluble, hydrophobically associating
copolymer used
comprises 0.1 to 15% by weight of at least one monoethylenically unsaturated,
hydrophobically
associating monomer (a) and 85 to 99.9% by weight of at least two
monoethylenically
unsaturated, hydrophilic monomers (b) different than (a). In addition, it is
optionally possible for
further, ethylenically unsaturated, preferably monoethylenically unsaturated,
monomers (c)
different than the monomers (a) and (b) to be present in an amount of up to
14.9% by weight.
The amounts mentioned are each based on the sum of all monomers in the
copolymer.
Preference is given to using exclusively monoethylenically unsaturated
monomers.
Monomers (a)
The water-soluble, hydrophobically associating copolymer used comprises at
least one
monoethylenically unsaturated monomer (a) which imparts hydrophobically
associating
properties to the copolymer and shall therefore be referred to hereinafter as
''hydrophobically
associating monomer". According to the invention, the monomers (a) are
selected from the
group of
1-12C=C(R1)-R2-0-(-CH2-CH(R3)-0-)k+CH2-CH(R4)-0-)I-R5 (I),
H2C=C(R1)-0-(-CH2-CH(R3)-0-)k-R5 (II),
H2C=C(R1)-(C=0)-0+CH2-CH(R3)-0-)k-R6 (III).
Monomers (a) of the formula (I)
In the monomers (a) of the formula (I), an ethylenic group H2C=C(R1)- is
bonded via a divalent
linking group -R2-0- to a polyoxyalkylene radical with block structure
-(-CH?-CH(R3)-0-)k+CH2-CH(R4)-0-)I-R5, where the two blocks -(-CH2-CH(R3)-0-)k
and
-(-CH2-CH(R4)-0-)i are arranged in the sequence shown in formula (I). The
polyoxyalkylene
radical has either a terminal OH group or a terminal ether group -0R5.
In the abovementioned formula, R1 is H or a methyl group.
R2 is a single bond or a divalent linking group selected from the group of -
(CH2n)- [R2a group],
-0-(Cn.H2n,)- [R2b group]- and -C(0)-0-(CrcH2n)- [R2b group]. In the formulae
mentioned, n, n'
and n" are each a natural number from 1 to 6. In other words, the linking
group comprises
straight-chain or branched aliphatic hydrocarbyl groups having 1 to 6
hydrocarbon atoms, which
PF 72130 CA 02826635 2013-08-06
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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 -(C-H2)- groups are preferably
linear aliphatic
hydrogarbyl groups.
5 The R2a group is preferably a group selected from ¨CH2-, -CH2-CH2- and
¨CH2-CH2-CH2-, more
preferably a methylene group ¨CH2-.
The R2b group is preferably a group selected from -0-CH2-CH2-, -0-CH2-CH2-CH2-
and
-0-CHg-CH2-CH2-CH2-, more preferably ¨0-CH2-CH2-CH2-CH2-.
The R2c group is preferably a group selected from ¨C(0)-0-CH2-CH2-, -C(0)0-
CH(CH3)-CH2_,
-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 R2 group is more preferably an R2a or R2b group, more preferably an R2b
group.
In addition, R2 is more preferably a group selected from ¨CH2- and -0-CH2-CH2-
CH2-CH2-, most
preferably -0-CH2-CH2-CH2-CH2-.
The monomers (I) also have a polyoxyalkylene radical which consists of the
units
-(-CH2-CH(R3)-0-)k and +CH2-CH(R4)-0-)1where 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.
In the -(-CH2-CH(R3)-0-)k block, the R3 radicals are each independently H,
methyl or ethyl,
preferably H or methyl, with the proviso that at least 50 mol% of the R3
radicals are H.
Preferably at least 75 mol% of the R3 radicals are H, more preferably at least
90 mol%, and they
are most preferably exclusively H. The block mentioned is thus a
polyoxyethylene block which
may optionally also have certain proportions of propylene oxide and/or
butylene oxide units,
preferably a pure polyoxyethylene block.
The number of alkylene oxide units k is a number from 10 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(R4)-0-)1- block, the R4 radicals are each
independently
hydrocarbyl radicals of at least 2 carbon atoms, preferably at least 3, more
preferably 3 to 10
and most preferably 3 to 4 carbon atoms. This may be an aliphatic and/or
aromatic, linear or
branched carbon radical. It is preferably an aliphatic radical.
PF 72130 CA 02826635 2013-08-06
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Examples of suitable R4 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 R4 radicals may also be ether groups of the general formula ¨CH2-0-R4'
where R4 is an
aliphatic and/or aromatic, linear or branched hydrocarbyl radical having at
least 2 carbon atoms,
preferably at least 3 and more preferably 3 to 10 carbon atoms. Examples of
R3' radicals
comprise n-propyl, n-butyl, n-pentyl, n-hexyl, 2-ethylhexyl, n-heptyl, n-
octyl, n-nonyl, n-decyl or
phenyl.
The +CH2-CH(R4)-0-)1- 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. Preferred R3
radicals are the
hydrocarbyl radicals mentioned; the units of the second terminal block are
more preferably
alkylene oxide units comprising at least 5 carbon atoms, 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.
The R5 radical is H or a preferably aliphatic hydrocarbyl radical having 1 to
30 carbon atoms,
preferably Ito 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.
In the monomers of the formula (I), a terminal monoethylenic group is joined
to a
polyoxyalkylene group with block structure, specifically firstly to a
hydrophilic block having
polyethylene 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 of higher
alkylene oxides, for example dodecene oxide. The second block has a terminal
¨0R5-group,
especially an OH-group. The terminal -(-CH2-CH(R4)-0-)Iblock with the R4
radicals is
responsible for the hydrophobic association of the copolymers prepared using
the monomers
(a). Etherification of the 01-I end group is an option which may be selected
by the person skilled
in the art according to the desired properties of the copolymer. A terminal
hydrocarbyl group is,
however, not required for the hydrophobic association, and the hydrophobic
association also
works with a terminal OH group.
It is clear to the person skilled in the art in the field of polyalkylene
oxide block copolymers that
the transition between the two blocks, according to the method of preparation,
may be abrupt or
else continuous. In the case of a continuous transition, there is 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, the first block -(-CH2-CH(R3)-0-)k may
accordingly also have small
amounts of -CH2-CH(R4)-0- units and the second block -(-CH2-CH(R4)-0-)1- small
amounts of
PF 72130 CA 02826635 2013-08-06
12
-CH2-CH(R3)-0- units, though these units are not distributed randomly over the
block but
arranged in the transition zone mentioned.
Preparation of the monomers (a) of the formula (I)
The hydrophobically associating monomers (a) of the formula (I) can be
prepared by methods
known in principle to those skilled in the art.
To prepare the monomers (a), a preferred preparation process proceeds from
suitable
monoethylenically unsaturated alcohols (IV) which are subsequently alkoxylated
in a two-stage
process such that the block structure mentioned is obtained. This gives
monomers (a) of the
formula (I) where R5 = H. These can optionally be etherified in a further
process step.
The type of ethylenically unsaturated alcohols (IV) to be used is guided here
especially by the
R2 group.
When R2 is a single bond, the starting materials are alcohols (IV) of the
general formula
H2C=C(R1)-0+CH2-CH(R7)-0-)d-H (IVa) where R1 is as defined above, R7 is H
and/or CH3,
preferably H, and d is a number from 1 to 5, preferably 1 or 2. Examples of
such alcohols
comprise diethylene glycol vinyl ether H2C=CH-O-CH2-CH2-0-CH2-CH2-0H or
dipropylene
glycol vinyl ether H2C=CH-O-CH2-CH(CH3)-0-CH2-CH(CH3)-0H, preferably
diethylene glycol
vinyl ether.
To prepare monomers (a) in which R2 is not a single bond, it is possible to
use alcohols of the
general formula H2C=C(R1)-R2-0H (IVb) or alcohols which already have alkoxy
groups and are
of the formula H2C=C(R1)-R2-0-(-CH2-CH(R7)-0-)d-H (IVc), where R7 and d are
each as defined
above, and R2 in each case is selected from the group of R2a, R2b and R2c.
The preparation of the monomers with a linking R2a group preferably proceeds
from alcohols of
the formula H2C=C(R1)¨(CnH2)-0H, especially H2C=CH¨(CnH2n)-0H, or alcohols of
the formula
H2C=C(R1)-0+CH2-CH(R7)-0-)d-H. Examples of preferred alcohols comprise ally!
alcohol
H2C=CH-CH2-0H or isoprenol H2C=C(CH3)-CH2-CH2-0H.
The preparation of the monomers with a linking R2b group proceeds from vinyl
ethers of the
formula H2C=C(R1)-0-(C04-12,)-0H, preferably H2C=CH-0-(C,,F120-0H. It is more
preferably
possible to use co-hydroxybutyl vinyl ether H2C=CH¨O-CH2-CH2-CH2-CH2-0H.
The preparation of the monomers with a linking R2ogroup proceeds from
hydroxyalkyl
(meth)acrylates of the general formula H2C=C(R1)-C(0)-0-(Cl20)-OH, preferably
H2C=C(R1)-C(0)-0-(Cn-H2n)-OH. Examples of preferred hydroxyalkyl
(meth)acrylates comprise
hydroxyethyl (meth)acrylate H2C=C(R1)-C(0)-0-CH2-CH2-0H and hydroxybutyl
(meth)acrylate
H2C=C(R1)-C(0)-0-CH2-CH2-CH2-CH2-0H.
PF 72130 CA 02826635 2013-08-06
13
The starting compounds mentioned are alkoxylated, specifically in a two-stage
process, first
with ethylene oxide, optionally in a mixture with propylene oxide and/or
butylene oxide, and in a
second step with alkylene oxides of the general formula (Xa) or (Xb)
0 0
(Xa) /OR 4
(Xb)
R4 CH2
where R4 in (Xa) and R4' in (Xb) are each as defined at the outset.
The performance of an alkoxylation including the preparation of block
copolymers from different
alkylene oxides is known in principle to those skilled in the art. It is
likewise known to those
skilled in the art that the reaction conditions, especially the selection of
the catalyst, can
influence the molecular weight distribution of the alkoxylates and the
orientation of alkylene
oxide units in a polyether chain.
The alkoxylates can be prepared, for example, by base-catalyzed alkoxylation.
For this purpose,
the alcohol used as the starting material can be admixed in a pressure reactor
with alkali metal
hydroxides, preferably potassium hydroxide, or with alkali metal alkoxides,
for example sodium
methoxide. By means of reduced pressure (e.g. <100 mbar) and/or increasing the
temperature
(30 to 150 C), water still present in the mixture can be removed. Thereafter,
the alcohol is
present as the corresponding alkoxide. This is followed by inertization with
inert gas (e.g.
nitrogen) and, in a first step, stepwise addition of ethylene oxide,
optionally in a mixture with
propylene oxide and/or butylene oxide, at temperatures of 60 to 180 C,
preferably 130 to
150 C. The addition is typically effected within 2 to 5 h, though the
invention should not be
restricted thereto. After the addition has ended, the reaction mixture is
appropriately allowed to
continue to react, for example for 1/2 h to 1 h. In a second step, alkylene
oxides of the general
formula (Xb) are subsequently metered in stepwise. The reaction temperature in
the second
stage can be maintained or else altered. A reaction temperature lower by
approx. 10 to 25 C
than in the first stage has been found to be useful.
The alkoxylation can also be undertaken by means of techniques which lead to
narrower
molecular weight distributions than the base-catalyzed synthesis. For this
purpose, the catalysts
used may, for example, be double hydroxide clays as described in DE 43 25 237
Al. The
alkoxylation can more preferably be effected using double metal cyanide
catalysts (DMC
catalysts). Suitable DMC catalysts are disclosed, for example, in DE 102 43
361 Al, especially
paragraphs [0029] to [0041] and the literature cited therein. For example, it
is possible to use
catalysts of the Zn-Co type. To perform the reaction, the alcohol used as the
starting material
can be admixed with the catalyst, and the mixture can be dewatered as
described above and
reacted with the alkylene oxides as described. Typically, not more than 250
ppm of catalyst
PF 72130 CA 02826635 2013-08-06
14
based on the mixture are used, and the catalyst can remain in the product due
to this small
amount.
The alkoxylation can additionally also be undertaken under acid catalysis. The
acids may be
Bronsted or Lewis acids. To perform the reaction, the alcohol used as the
starting material can
be admixed with the catalyst, and the mixture can be dewatered as described
above and
reacted with the alkylene oxides as described. At the end of the reaction, the
acidic catalyst can
be neutralized by addition of a base, for example KOH or NaOH, and filtered
off if required.
It is clear to the person skilled in the art in the field of the polyalkylene
oxides that the orientation
of the hydrocarbyl radicals R4 and optionally R3 may depend on the conditions
of the
alkoxylation, for example on the catalyst selected for the alkoxylation. The
alkylene oxide
groups can thus be incorporated into the monomer either in the -(-Cl12-CH(R4)-
0-) orientation or
else in the inverse -(-CH(R4)¨CH2-0-)- orientation. The description in formula
(I) should
therefore not be considered to be restricted to a particular orientation of
the R3 or R4 groups.
When the terminal OH group of the monomers (a) of the formula (I) (i.e. R5 =
H) is to be
etherified, this can be accomplished with customary alkylating agents known in
principle to
those skilled in the art, for example alkyl sulfates. For etherification, it
is especially possible to
use dimethyl sulfate or diethyl sulfate.
The preferred preparation process described for the monomers (I) has the
advantage that the
formation of possibly crosslinking by-products is substantially avoided.
Accordingly, it is possible
to obtain copolymers with a particularly low gel content.
Monomers (a) of the formulae (II) and (III)
In the monomers of the formulae (II) and (III), R1, R3 and k are each defined
as already outlined.
R6 is an aliphatic and/or aromatic, straight-chain or branched hydrocarbyl
radical having 8 to 40
carbon atoms, preferably 12 to 32 carbon atoms. For example, it may comprise n-
alkyl groups
such as n-octyl, n-decyl or n-dodecyl groups, phenyl groups, and especially
substituted phenyl
groups. Substituents on the phenyl groups may be alkyl groups, for example C1-
C6-alkyl groups,
preferably styryl groups. Particular preference is given to a tristyrylphenyl
group.
The hydrophobically associating monomers of the formulae (II) and (III) and
the preparation
thereof are known in principle to those skilled in the art, for example from
EP 705 854 Al.
PF 72130 CA 02826635 2013-08-06
Amounts of monomers (a)
The amount of the monoethylenically unsaturated, hydrophobically associating
monomers (a) is
0.1 to 15% by weight, based on the total amount of all monomers in the
copolymer, especially
5 0.1 to 10% by weight, preferably 0.2 to 5% by weight and more preferably
0.5 to 5% by weight
and, for example, 0.5 to 2% by weight.
Particular preference is given to using monomers (a) of the general formula
(I) to prepare the
inventive copolymers.
Monomers (b)
Over and above the monomers (a), the hydrophobically associating copolymer
used in
accordance with the invention comprises at least two monoethylenically
unsaturated monomers
(b) different than (a). referred to hereinafter as (b1) and (b2).
The monomers (b1) are uncharged, hydrophilic monomers.
The monomers (b2) are anionic, hydrophilic monomers (b2a) and/or (meth)acrylic
esters (b2b).
The (meth)acrylic esters themselves are, according to the nature of the ester
group, generally
not hydrophilic, but can be hydrolyzed under formation conditions to form
hydrophilic groups.
More preferably, the hydrophilic monomers (b1) and (b2a) used are miscible
with water in any
ratio, but it is sufficient for execution of the invention that the inventive,
hydrophobically
associating copolymer possesses the water solubility mentioned at the outset.
In general, the
solubility of the monomers (131) and (b2a) in water at room temperature should
be at least 50 g/I,
preferably at least 150 g/I and more preferably at least 250 g/I.
According to the invention, the copolymer comprises at least one uncharged,
monoethylenically
unsaturated, hydrophilic monomer (b1) selected from the group of
(meth)acrylamide,
N-methyl(meth)acrylamide, N,N'-dimethyl(meth)acrylamide or N-
methylol(meth)acrylamide.
Preference is given to (meth)acrylamide, especially acrylamide. When mixtures
of different
monomers (b1) are used, at least 50 mol% of the monomers (b1) should be
(meth)acrylamide,
preferably acrylamide.
According to the invention, the copolymer used further comprises at least
monomer (b2a)
and/or (b2b).
Monomer (b2a) comprises hydrophilic, monoethylenically unsaturated anionic
monomers which
have at least one acidic group selected from the group of ¨COOH, ¨S03H and -
P03H2 and salts
thereof. Preference is given to monomers comprising COOH groups and/or -S03H
groups,
particular preference to monomers comprising ¨803H groups. The monomers may of
course
PF 72130 CA 02826635 2013-08-06
16
also be the salts of the acidic monomers. Suitable counterions comprise
especially alkali metal
ions such as Li*, Na. or K., and ammonium ions such as NH4 + or ammonium ions
with organic
radicals.
Examples of monomers comprising COOH groups comprise acrylic acid, methacrylic
acid,
crotonic acid, itaconic acid, maleic acid or fumaric acid. Preference is given
to acrylic acid.
Examples of monomers comprising sulfo groups comprise vinylsulfonic acid,
allylsulfonic acid,
2-acrylamido-2-methylpropanesulfonic acid, 2-methacrylamido-2-
methylpropanesulfonic acid, 2-
acrylamidobutanesulfonic acid, 3-acrylamido-3-methylbutanesulfonic acid or 2-
acrylamido-2,4,4-
trimethylpentanesulfonic acid. Preference is given to vinylsulfonic acid,
allylsulfonic acid or 2-
acrylamido-2-methylpropanesulfonic acid, and particular preference to 2-
acrylamido-2-
methylpropanesulfonic acid.
Examples of monomers comprising phospho groups comprise vinylphosphonic acid,
allylphosphonic acid, N-(meth)acrylamidoalkylphosphonic acids or
(meth)acryloyloxyalkyl-
phosphonic acids, preference being given to vinylphosphonic acid.
For the sake of completeness, it should be mentioned that the monomers (b1)
can be
hydrolyzed at least partly to (meth)acrylic acid under some circumstances in
the course of
preparation and use of the copolymers. The hydrolysis can of course also be
undertaken
deliberately by the person skilled in the art. The copolymers used in
accordance with the
invention may accordingly comprise (meth)acrylic acid units, even if
(meth)acrylic acid itself has
not been used for the synthesis. The tendency to hydrolysis of the monomers
(b1) decreases
with increasing content of sulfo groups. Accordingly, the presence of sulfo
groups in the
copolymer used in accordance with the invention is advisable. The monomers
(b2b) are
(meth)acrylic esters of the general formula H2C=C(R16)-000R16. For example,
R16 may be
methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl, i-butyl, 1-pentyl, 1-
hexyl, 1-heptyl or 1-octyl
radicals.
R15 here is H or methyl, preferably H. R16 is a straight-chain or preferably
branched alkyl radical
having 1 to 8 carbon atoms.
Ris is preferably a secondary alkyl radical ¨CH(R17)(R17'), where R17 and R17
are straight-chain
or branched alkyl radicals, with the proviso that the total number of carbon
atoms in the R17 and
R17' radicals is 2 to 7. Examples of such secondary alkyl radicals comprise 2-
propyl, 2-butyl or
2-pentyl radicals.
Additionally preferably, R16 is a tertiary alkyl radical ¨C(R18)(R18)(R18"),
where R15, R18., Rla" are
straight-chain or branched alkyl radicals, with the proviso that the total
number of carbon atoms
in the R15, R18 and R18" radicals is 3 to 7. A particularly preferred tertiary
alkyl radical is a t-butyl
radical ¨C(CH3)3.
PF 72130 CA 02826635 2013-08-06
17
The ester groups of the (meth)acrylic esters (b2b) can, after being
incorporated into the
copolymer, be hydrolyzed to ¨COON groups or salts thereof, especially under
formation
conditions, i.e. especially elevated temperature. This results in in situ
formation of polymers
comprising the units (b1) and (b2a). Esters having secondary and especially
tertiary alkyl
radicals are hydrolyzed more quickly than esters of primary alkyl radicals and
are therefore
particularly preferred.
The copolymers used in accordance with the invention may additionally
optionally comprise at
least one monoethylenically unsaturated, cationic monomer (b3) having ammonium
ions.
Suitable cationic monomers (b3) comprise especially monomers having ammonium
groups,
especially ammonium derivatives of N-(w-aminoalkyl)(meth)acrylamides or co-
aminoalkyl-
(meth)acrylic esters, and also diallyldimethylammonium salts.
More particularly, monomers (b3) having ammonium groups may be compounds of
the general
formulae H2C=C(R8)-CO-NR9-R10_NR113+X- (Va) and/or H2C=C(R8)-COO-R10-NR113+X-
(Vb). In
these formulae, R8 is H or methyl, R9 is H or a Cl-C4-alkyl group, preferably
H or methyl, and
Rlo is a preferably linear C1-C4-alkylene group, for example a 1,2-ethylene
group ¨CH2-CH2- or
a 1,3-propylene group ¨CH2-CH2-CH2- .
The R11 radicals are each independently Cl-C4-alkyl radicals, preferably
methyl, or a group of
the general formula ¨R12-S03H where R12 is a preferably linear C1-C4-alkylene
group or a phenyl
group, with the proviso that generally not more than one of the R11
substituents is a substituent
having sulfo groups. More preferably, the three R11 substituents are methyl
groups, i.e. the
monomer has a ¨N(CH3)3+ group. X- in the above formula is a monovalent anion,
for example
Cl-. X- may of course also be a corresponding fraction of a polyvalent anion,
though this is not
preferred. Examples of preferred monomers (b3) of the general formula (Va) or
(Vb) comprise
salts of 3-trimethylammoniopropyl(meth)acrylamides or 2-trimethylammonioethyl
(meth)acrylates, for example the corresponding chlorides such as 3-
trimethylammoniopropyl-
acrylamide chloride (DIMAPAQUAT) and 2-trimethylammoniomethyl methacrylate
chloride
(MADAME-QUAT).
The copolymers used in accordance with the invention may additionally also
comprise further
monoethylenically unsaturated hydrophilic monomers (b4) different than the
hydrophilic
monomers (b1), (b2) and (b3). Examples of such monomers comprise monomers
comprising
hydroxyl groups and/or ether groups, for example hydroxyethyl (meth)acrylate,
hydroxypropyl
(meth)acrylate, ally' alcohol, hydroxyvinyl ethyl ether, hydroxyvinyl propyl
ether, hydroxyvinyl
butyl ether, or compounds of the formula H2C=C(R1)-000-(-CH2-CH(R13)-0-)b-R14
(Via) or
H2C=C(R1)-0-(-CH2-CH(R13)-0-)b-R14 (Vlb), where R1 is as defined above and b
is a number
from 2 to 200, preferably 2 to 100. The R13 radicals are each independently H,
methyl or ethyl,
preferably H or methyl, with the proviso that at least 50 mol% of the R13
radicals are H.
Preferably at least 75 mol% of the R13 radicals are H, more preferably at
least 90 mol%, and
PF 72130 CA 02826635 2013-08-06
18
they are most preferably exclusively H. The R14 radical is H, methyl or ethyl,
preferably H or
methyl. Further examples of monomers (b4) comprise N-vinyl derivatives, for
example
N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone or N-vinylcaprolactam,
and vinyl esters,
for example vinyl formate or vinyl acetate. N-Vinyl derivatives can be
hydrolyzed after
polymerization to give vinylamine units, and vinyl esters to give vinyl
alcohol units.
Copolymers used with preference comprise monomers (b1) and (b2a), but no
monomers (b2b).
Further copolymers used with preference comprise monomers (b1) and (b2b), but
no monomers
(b2a). As explained above, however, it is also possible in this case for the
ester groups of the
monomers (b2b) to be hydrolyzed to ¨0001-I groups, especially under formation
conditions, and
so such copolymers may also have ¨COON groups some time after employment.
The amount of all monomers (b) in the inventive copolymer is, in accordance
with the invention,
85 to 99.9% by weight, based on the total amount of all monomers in the
copolymer, preferably
90 to 99.8% by weight.
The amount of the uncharged, hydrophilic monomers (b1) here is generally 30 to
95% by
weight, preferably 30 to 85% by weight and more preferably 30 to 70% by
weight, based on the
total amount of all monomers used.
When the copolymer comprises only uncharged monomers (b1) and anionic monomers
(b2a), it
has been found to be useful to use the uncharged monomers (b1) in an amount of
30 to 95% by
weight and the anionic monomers (b2a) in an amount of 4.9 to 69.9% by weight,
each amount
being based on the total amount of all monomers used. In this embodiment, the
monomers (b1)
are preferably used in an amount of 30 to 80% by weight and the anionic
monomers (b2a) in an
amount of 19.9 to 69.9% by weight, and the monomers (b1) are more preferably
used in an
amount of 40 to 70% by weight and the anionic monomers (b2a) in an amount of
29.9 to 59.9%
by weight.
When the copolymer comprises uncharged monomers (b1), anionic monomers (b2a)
and
cationic monomers (b3), it has been found to be useful to use the uncharged
monomers (b1) in
an amount of 30 to 95% by weight, and the anionic (b2a) and cationic (b3)
monomers together
in an amount of 4.9 to 69.9% by weight, with the proviso that the molar
(b2a)/(b3) ratio is 0.7 to
1.3. The molar (b2a)/(b3) ratio is preferably 0.8 to 1.2 and, for example, 0.9
to 1.1. This
measure makes it possible to obtain copolymers which are particularly
insensitive to salt
burden. In this embodiment, the monomers (b1) are preferably used in an amount
of 30 to 80%
by weight, and the anionic and cationic monomers (b2a) + (b3) together in an
amount of 19.9 to
69.9% by weight, and the monomers (b1) are more preferably used in an amount
of 40 to 70%
by weight and the anionic and cationic monomers (b2a) + (b3) together in an
amount of 29.9 to
59.9% by weight, where the molar ratio already mentioned should be observed in
each case.
PF 72130 CA 02826635 2013-08-06
19
The amount of the monomers (b2b) is judged by the person skilled in the art
such that the water
solubility of the copolymer is not impaired by the use of the monomers (b2b).
The amount of the
monomers (b2b) should therefore generally, if present, not exceed 20% by
weight, based on the
total amount of all monomers. The amount should preferably not exceed 10% by
weight. It may,
for example, be 0.5 to 5% by weight.
Monomers (c)
In addition to the hydrophilic monomers (a) and (b), the inventive copolymers
may optionally
comprise ethylenically unsaturated monomers different than the monomers (a)
and (b),
preferably monoethylenically unsaturated monomers (c). Of course, it is also
possible to use
mixtures of a plurality of different monomers (c).
Such monomers can be used for fine control of the properties of the copolymer
used in
accordance with the invention. If present at all, the amount of such
optionally present monomers
(c) may be up to 14.9% by weight, preferably up to 9.9% by weight, more
preferably up to 4.9%
by weight, based in each case on the total amount of all monomers. Most
preferably, no
monomers (c) are present.
The monomers (c) may, for example, be monoethylenically unsaturated monomers
which have
more hydrophobic character than the hydrophilic monomers (b1) and (b2a) and
which are
accordingly water-soluble only to a minor degree. In general, the solubility
of the monomers (c)
in water at room temperature is less than 50 g/I, especially less than 30 V.
Examples of such
monomers comprise N-alkyl- and N,IT-dialkyl(meth)acrylamides, where the number
of carbon
atoms in the alkyl radicals together is at least 3, preferably at least 4.
Examples of such
monomers comprise N-butyl(meth)acrylamide, N-cyclohexyl(meth)acrylamide or
N-benzyl(meth)acrylamide.
Preparation of the hydrophobically associating copolymers
The copolymers used in accordance with the invention 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 (c), for example by solution or gel polymerization in the aqueous
phase.
For polymerization, the monomers (a), (b), optionally (c), initiators and
optionally further
assistants for polymerization are used in an aqueous medium.
In a preferred embodiment, the preparation is undertaken by means of gel
polymerization in the
aqueous phase. For gel polymerization, a mixture of the monomers (a), (b) and
optionally (c),
initiators and optionally further assistants with water or an aqueous solvent
mixture is first
provided. Suitable aqueous solvent mixtures comprise water and water-miscible
organic
30 CA 02826635 2013-08-06
PF 721
solvents, where the proportion of water is generally at least 50% by weight,
preferably at least
80% by weight and more preferably at least 90% by weight. Organic solvents in
this context
include especially water-miscible alcohols such as methanol, ethanol or
propanol. Acidic
monomers can be fully or partly neutralized before the polymerization. The
concentration of all
5 components except the solvents in the course of the polymerization is
typically approx. 20 to
60% by weight, preferably approx. 30 to 50% by weight. The polymerization
should especially
be performed at a pH in the range from 5.0 to 7.5 and preferably at a pH of
6Ø
10 Polymerization in the presence of a nonpolymerizable, interface-active
compound
In a preferred embodiment of the invention, the copolymers used are prepared
in the presence
of at least one nonpolymerizable, surface-active compound (T).
15 The nonpolymerizable, surface-active compound (T) is preferably at least
one nonionic
surfactant, but anionic and cationic surfactants are also suitable to the
extent that they do not
take part in the polymerization reaction. They may especially be surfactants,
preferably nonionic
surfactants, of the general formula R13-Y' where R13 is a hydrocarbyl radical
having 8 to 32,
preferably 10 to 20 and more preferably 12 to 18 carbon atoms, and Y' is a
hydrophilic group,
20 preferably a nonionic hydrophilic group, especially a polyalkoxy group.
The nonionic surfactant is preferably an ethoxylated long-chain aliphatic
alcohol which may
optionally comprise aromatic components.
Examples include: C12C14-fatty alcohol ethoxylates, CisCia-fatty alcohol
ethoxylates, C13-oxo
alcohol ethoxylates, Clo-oxo alcohol ethoxylates, C13C15-oxo alcohol
ethoxylates, Clo-Guerbet
alcohol ethoxylates and alkylphenol ethoxylates. Useful compounds have
especially been found
to be those having 5 to 20 ethyleneoxy units, preferably 8 to 18 ethyleneoxy
units. It is optionally
also possible for small amounts of higher alkyleneoxy units to be present,
especially
propyleneoxy and/or butyleneoxy units, though the amount in the form of
ethyleneoxy units
should generally be at least 80 mol% based on all alkyleneoxy units.
Especially suitable are surfactants selected from the group of the ethoxylated
alkylphenols, the
ethoxylated, saturated iso-C13-alcohols and/or the ethoxylated C10-Guerbet
alcohols, where in
each case 5 to 20 ethyleneoxy units, preferably 8 to 18 ethyleneoxy units, are
present in alkoxy
radicals.
Surprisingly, the addition of nonpolymerizable, interface-active compounds (T)
during the
polymerization leads to a distinct improvement in performance properties of
the copolymer in
polymer flooding. More particularly, the thickening action is increased and
the gel content of the
copolymer is also reduced. This effect can probably be explained as follows,
without any
intention that the invention thus be tied to this explanation. In the case of
polymerization without
the presence of a surfactant, the hydrophobically associating comonomers (a)
form micelles in
PF 72130 CA 02826635 2013-08-06
=
21
the aqueous reaction medium. In the polymerization, this leads to blockwise
incorporation of the
hydrophobically associating regions into the polymer. If, in accordance with
the invention, an
additional surface-active compound is present in the preparation of the
copolymers, mixed
micelles form. These mixed micelles comprise polymerizable and
nonpolymerizable
components. As a result, the hydrophobically associating monomers are then
incorporated in
relatively short blocks. At the same time, the number of these relatively
short blocks is greater
per polymer chain. Thus, the structure of the copolymers prepared in the
presence of a
surfactant differs from those without the presence of a surfactant.
The nonpolymerizable, interface-active compounds (T) can generally be used in
an amount of
0.1 to 5% by weight, based on the amount of all monomers used.
The weight ratio of the nonpolymerizable, interface-active compounds (T) used
to the
monomers (a) is generally 4:1 to 1:4, preferably 2:1 to 1:2, more preferably
1.5:1 to 1:1.5 and,
for example, approx. 1:1.
Performance of the polymerization
For the polymerization, the components required are first mixed with one
another. The
sequence with which the components are mixed for polymerization is
unimportant; what is
important is merely that, in the preferred polymerization method, the
nonpolymerizable,
interface-active compound (T) is added to the aqueous polymerization medium
before the
initiation of the polymerization.
The mixture is subsequently polymerized thermally and/or photochemically,
preferably at -5 C
to 80 C. If polymerization is effected thermally, preference is given to using
polymerization
initiators which can initiate the polymerization 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 to
10 C. It is also
possible to combine photochemical and thermal polymerization with one another,
by adding
both initiators for the thermal and photochemical 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 released 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%.
In a further preferred embodiment of the polymerization, it is also possible
to perform the
reaction with a mixture of a redox initiator system and a thermal initiator
which does not
decompose until relatively high temperatures. This may, for example, be a
water-soluble azo
initiator which decomposes within the temperature range from 40 C to 70 C. The
polymerization
PF 72130 CA 02826635 2013-08-06
22
here is at first initiated at low temperatures of, for example, 0 to 10 C by
the redox initiator
system. The heat of reaction released heats the mixture, and this additionally
initiates the
polymerization by virtue of the initiator which does not decompose until
relatively high
temperatures.
The gel polymerization is generally effected without stirring. It can be
effected batchwise 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, for example, a polymerization apparatus possessing a
conveyor belt to
accommodate the mixture to be polymerized is used. The conveyor belt is
equipped with
devices for heating and/or for irradiating with UV radiation. In this method,
the mixture is poured
onto one end of the belt by means of a suitable apparatus, 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 drying
should preferably be effected at temperatures below 100 C. To prevent
conglutination, it is
possible to use a suitable separating agent for this step. This gives the
hydrophobically
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].
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 which accelerates
or improves the
dissolution of the dried polymer in water to the inventive polymers as early
as in the course of
synthesis. This assistant may, for example, be urea.
The resulting copolymers preferably have a weight-average molecular weight NAN
of 1*106 g/mol
to 30*106 g/mol, preferably 5*106 g/mol to 20*106 g/mol.
Aqueous formulation for process step (1)
To execute the process, an aqueous formulation which comprises, in addition to
water, at least
the hydrophobically associating copolymer described is used. It is of course
also possible to use
mixtures of different hydrophobically associating copolymers.
As well as water, the formulation may also comprise water-miscible organic
solvents, in which
case the amount of the water should generally comprise at least 75% by weight,
preferably at
least 90% by weight and more preferably at least 95% by weight based on the
sum of all
PF 72130 CA 02826635 2013-08-06
23
solvents used. Very particular preference is given to using exclusively water
as the solvent. The
formulation can be made up in freshwater or else in water comprising salts.
The formulation can
preferably be prepared by initially charging the water, sprinkling in the
copolymer as a powder
and mixing it with the water, and is preferably made up at ambient
temperature.
According to the invention, the concentration of the polymer in the
formulation is 0.1 to 3% by
weight based on the sum of all components of the aqueous formulation. The
amount is
preferably 0.5 to 3% by weight and more preferably 1 to 3% by weight.
The concentration of the copolymer and hence the viscosity of the formulation
used can be
determined by the person skilled in the art according to the conditions in the
formation.
The formulation may optionally comprise further components, for example
crosslinkers,
biocides, stabilizers or salts.
Further components may especially be water-soluble crosslinkers which can
bring about
crosslinking of the hydrophobically associating copolymer under deposit
conditions.
Crosslinkers may, for example, be water-soluble compounds comprising di-, tri-
or tetravalent
metal ions, for example compounds comprising AI(III), Cr(III) or Zr(IV) ions,
for example
chromium(III) acetate, aluminum(III) citrate, zirconium(IV) salts such as
zirconium(IV) lactate or
zirconium(IV) acetate. The crosslinkers may also be boric acid or salts
thereof.
The crosslinkers may also be organic crosslinkers, for example aldehydes such
as
formaldehyde, glyoxal or glutaraldehyde, or organic compounds comprising at
least two amino
or ammonium groups, for example polyethyleneimines, polyvinylamine or
polyetheramines.
The crosslinkers may also be microencapsulated crosslinkers in which the
crosslinker is
released only after the injection of the formulation into the formation.
The amounts of crosslinker are selected by the person skilled in the art
according to the desired
properties, for example the desired degree of crosslinking. The amount of
crosslinker may, for
example, be 1 to 10% by weight based on the amount of the polymer used.
Performance of process step (1)
The performance of process step (1) involves injecting the above-described
aqueous
formulation which comprises at least the hydrophobically associating copolymer
described into
the formation through at least one well.
Process step (1) can be executed as the first process step, and then process
step (2) of the
process according to the invention. Process step (1) can, however, also be
executed only after
PF 72130 CA 02826635 2013-08-06
24
a first performance of process step (2), especially after water flooding of
the formation. This
variant is advisable when water production has already risen significantly as
a result of
sustained water flooding.
The injection of the aqueous formulation can be undertaken by means of
customary apparatus.
The formulation can be injected by means of customary pumps. The wells are
typically lined
with cemented steel pipes, and the steel pipes are perforated at the desired
site. The
formulation enters the mineral oil formation through the perforation in the
well. In a manner
known in principle, the pressure applied by means of the pumps fixes the flow
rate of the
formulation and hence also the shear stress with which the aqueous formulation
enters the
deposit. The process may of course also be performed when the well has not
been lined.
According to the type of underground formation and the regions to be blocked,
a person skilled
in the art selects suitable copolymers. The formation of a gel in the
underground formation can,
according to the copolymer, proceed with use of crosslinkers or else without
the use of
crosslinkers.
The copolymers used in accordance with the invention as a constituent of the
aqueous
formulation, especially those which comprise monomers (a), (b1) and (b2a), are
notable for
thermal thickening characteristics within particular temperature ranges, which
means that the
aqueous formulations are notable in that the viscosity thereof at room
temperature is lower than
at higher temperatures. In general, the viscosity passes through a maximum in
the range from
approx. 50 to 80 C. The details on this subject are given in the experimental
section.
Preferred copolymers for this application comprise, as well as the monomers
(a) and (b1),
monomers (b2a) having sulfo groups. These may more preferably be copolymers
comprising
monomers (a), acrylamide and 2-acrylamido-2-methylpropanesulfonic acid.
In a first preferred embodiment of the invention, permeable regions of the
formation can
therefore be blocked by exploiting the thermal thickening characteristics of
the copolymers
used. For this embodiment, no crosslinker need be added to the formulation.
In this first preferred embodiment, the temperature of the aqueous formulation
before the
injection should preferably be lower than the deposit temperature. "Before the
injection" relates
to the temperature of the formulation at the surface of the earth before it is
injected into the well.
The temperature of the aqueous formulation before the injection into the
deposit is preferably
less than 35 C, more preferably less than 30 C and, for example, approx. 15 C
to 25 C.
In this preferred embodiment, the temperature of the aqueous formulation of
the
hydrophobically associating copolymer is lower than the deposit temperature.
After entry into
the mineral oil formation, the aqueous formulation naturally flows into the
permeable regions of
the formation with low flow resistance. Under the influence of the deposit
temperature, the
aqueous formulation heats up to an increasing degree and accordingly gradually
increases in
viscosity until ultimate formation of a gel which has such a high viscosity
that the permeable
PF 72130 CA 02826635 2013-08-06
regions of the formation are blocked. This variant is suitable especially for
formations with a
deposit temperature of more than 40 C, preferably more than 45 C, especially
40 C to 100 C,
preferably 45 C to 90 C, more preferably 50 C to 75 C. In this embodiment, the
temperature of
the aqueous formulation before injection into the deposit should be at least
10 C, preferably at
5 least 20 C, lower than the deposit temperature.
The hydrophobically associating copolymers used in accordance with the
invention, especially
the already mentioned copolymers comprising monomers (a), (b1) and (b2a) also
have shear-
diluting characteristics, i.e. the viscosity thereof decreases with increasing
shear. It is therefore
10 advisable to inject the aqueous formulations with high flow rate. This
retards the heating of the
formulation, but the shear-diluting characteristics do not result in
mechanical degradation of the
copolymer on entry into the formation, and so it regains viscosity after the
shear has declined.
In a second preferred embodiment of the invention, the shear rate on entry of
the aqueous
15 copolymer formulation into the formation is therefore at least 30 000 s-
1, preferably at least
60 000 s-1 and more preferably at least 90 000 s-1. The shear stress on entry
into the formation
can be calculated by the person skilled in the art in a manner known in
principle on the basis of
the Hagen-Poiseuille law using the area flowed through on entry into the
formation, the mean
pore radius and the volume flow rate. The average porosity of the formation
can be calculated in
20 a manner known in principle by measurements on drill cores. The greater
the volume flow rate
of aqueous formulation injected into the formation, the greater the shear
stress will naturally be.
Copolymers particularly preferred for execution of the outlined embodiments 1
and 2 of the
process comprise monomers (a) of the general formula H2C=CH-0-(CH2),-0-(-CH2-
CH2-0-)k-
25 (-CH2-CH(R4)-0-)1-H (la) where n' is 2 to 6, preferably 2 to 4 and more
preferably 4. R4 in the
preferred variant is a hydrocarbyl radical having 3 to 10 carbon atoms,
especially an n-propyl
radical. In addition, in formula (la), k is a number from 20 to 30 and I is a
number from 6 to 20,
preferably 8 to 18. The amount of the monomers (a) of the formula (la) is 0.2
to 5% by weight,
preferably 0.5 to 2% by weight. As monomer (b1) the copolymer preferred for
embodiments 1
and 2 comprises 40 to 60% by weight of acrylamide, and as monomer (b2a) 35 to
55% by
weight of a monomer (b2a) having sulfo groups, preferably 2-acrylamido-2-
methylpropane-
sulfonic acid or salts thereof. Particular preference is given to using
exclusively monomers (b2a)
having sulfo groups.
In a third preferred embodiment of the invention, a formulation which
additionally comprises one
or more crosslinkers which can bring about the crosslinking of the polymer
under deposit
conditions is used. The crosslinking reaction thus occurs only in the course
of heating of the
formulation to deposit temperature. For this purpose, the above-described
crosslinkers can be
used in the aqueous formulation. The crosslinking of the polymer improves the
strength of the
gel for blockage of the formation. For the third embodiment too, the
copolymers particularly
suitable for embodiments 1 and 2 can be used with preference.
PF 72130 CA 02826635 2013-08-06
26
For the third embodiment, it is particularly advantageously possible to use
copolymers having
COOH groups, or those which form COOH groups under formation conditions.
Copolymers which are particularly advantageous for this third embodiment are
therefore those
which comprise monomers (a), (b1) and (b2b). Preference is given especially to
copolymers
comprising monomers (a) of the general formula H2C=CH-0-(CH2)re-0-(-CH2-CH2-0-
)k+CH2-
CH(R4)-04-H (la). Preferred ranges for n', k, I and R4 have already been
specified above. (b1)
is preferably acrylamide, and (b2b) especially comprises readily hydrolyzable
esters with
secondary or tertiary ester groups, especially t-butyl (meth)acrylate.
Preferred amounts are 0.2
to 5% by weight of monomers (la), 70 to 99.7% by weight of (b1) and 0.1 to 10%
by weight,
preferably 0.2 to 5% by weight, of (b2b).
The mode of action of the crosslinkers is known in principle to those skilled
in the art. In this
regard, we make reference to the literature cited at the outset, for example
from the review
article Boding et aZ "Pushing out the oil with Conformance Control" in
Oilfield Review (1994),
pages 44 ff What is essential is that crosslinking reactions do not proceed at
a significant rate
at room temperature, but only at higher temperatures, especially at
temperatures of > 50 C. At
higher temperatures, ¨CONR2 and/or ¨000R16 groups present in the polymer can
be
hydrolyzed to ¨COOH groups, and the ¨COOH groups of different copolymer chains
can
crosslink with one another via complexation with metal ions present in the
formulation. It is
likewise possible for COON groups to react with polyethyleneimines and/or
forms salts, and
thus crosslink the copolymers. The crosslinking forms a high-viscosity gel
which blocks the
formation.
In a fourth preferred embodiment of the invention, copolymers which also
comprise cationic
monomers (b3) as well as monomers (b1) and (b2a) are used in the aqueous
formulation.
Preferred copolymers for this fourth embodiment comprise 0.2 to 5% by weight,
preferably 0.5
to 2% by weight, of monomers (a) of the general formula (la), and, as monomers
(b1), 30 to
40% by weight of acrylamide. They additionally comprise 25 to 35% by weight of
at least one
monomer (b2a) having sulfo groups, preferably 2-acrylamido-2-
methylpropanesulfonic acid or
salts thereof, and 25 to 35% by weight of at least one cationic monomer having
ammonium
ions, preferably salts of dialkyldiallylammonium, 3-
trimethylammoniopropyl(meth)acrylamides
and 2-trimethylammonioethyl (meth)acrylates.
This embodiment can be used, for example, in silicatic formations, especially
sandstone
formations. However, it can of course also be used in other formations, for
example carbonatic
formations. Silicatic formations have anionic sites on the surface, which can
interact well with
the cationic sites of the copolymers used. It is thus possible to form a
polymer film on the
surface of the rock formation, which constricts free cross sections. Further
polymer can be
absorbed on the polymer-modified surface. It will be appreciated that this
embodiment can also
be combined with crosslinking of the copolymer. For this purpose, the
crosslinkers already
outlined can be used.
PF 72130 CA 02826635 2013-08-06
27
In a fifth preferred embodiment of the invention, the injection of the
copolymer used in
accordance with the invention is preceded by injection of an aqueous
formulation of a polymer
having cationic groups. Examples of suitable cationic polymers comprise
poly(diallyldimethyl-
ammonium chloride), poly(N-acrylamidopropyl-N,N,N-trimethylammonium chloride)
or poly(N-
methacrylatopropyl-N,N-dimethyl¨N-benzylammonium chloride), or corresponding
copolymers,
for example with acrylannide as a comonomer.
After the injection of the cationic polymer, the aqueous formulation of the
copolymer used in
accordance with the invention is injected into the formation, and the surface
is cationically
modified as a result. The copolymer which has anionic groups and is used in
accordance with
the invention can be adsorbed efficiently on the cationically modified
surface. In a preferred
embodiment of the invention, the injection of aqueous formulations of a
cationic polymer and of
the copolymer used in accordance with the invention can be repeated once or
more than once.
In this way, a multilayer polymer film of ever greater thickness forms on the
formation surface.
The aqueous copolymer formulation can be injected either through one or more
injection wells
and/or one or more production wells. This is guided by the specific conditions
in the formation.
Injection into a production well is particularly advisable, for example, when
a water-bearing
stratum is arranged below a mineral oil-bearing stratum, and water is
increasingly being
produced from the water-bearing stratum. For injection into production wells,
the injection of
aqueous flooding media into the injection wells is generally stopped. Measures
known in
principle to those skilled in the art can ensure that the aqueous copolymer
formulation is
actually injected into the water-bearing zone and not into the oil-bearing
zone. For example,
through suitable lining of the well, steel pipes perforated exactly in the
region of the water-
bearing stratum can inject the copolymer formulation into the water-bearing
stratum in a
controlled manner. In addition, the penetration of polymer formulation into
the oil-bearing
stratum can be prevented by simultaneously injecting an inert protection fluid
into the oil-bearing
stratum.
In the case of injection into one or more injection wells, the aqueous
copolymer formulation
naturally flows into the permeable regions of the formation with low flow
resistance, and hence
exactly through the regions which are to be blocked.
Process step (2)
In process step (2), mineral oil is actually produced by injection of an
aqueous flooding medium
into the at least one injection well and withdrawing mineral oil through the
at least one
production well. The aqueous flooding medium injected maintains the pressure
and forces the
mineral oil from the injection wells in the direction of the production wells.
PF 72130 CA 02826635 2013-08-06
28
The aqueous flooding medium may preferably be water or salt-containing water.
In this case,
the process is called "water flooding". It is possible to inject either
freshwater or saltwater. For
example, seawater can be used for injection, for example in the case of
production platforms, or
it is possible to use produced formation water, which is reused in this
manner. It may be cold
water or hot water. The aqueous flooding media may, however, also be steam
("steam
flooding"), aqueous formulations comprising surfactants ("surfactant
flooding") or formulations
comprising thickening polymers ("polymer flooding").
When process step (2) is executed repeatedly, the aqueous flooding media used
in each case
may be identical aqueous flooding media or have different compositions.
When step (1) is executed by injection into the injection wells, it is
advisable to commence the
process with the performance of step (1). This is followed by process step
(2). If process step
(2) has formed new preferential flow paths, these can be blocked by repetition
of step (1),
followed by continuation with step (2). It will be appreciated that it is also
possible to repeat the
sequence of steps (1) and (2) several times.
The blocking of permeable regions from the production well can advantageously
be performed
when water production has risen, i.e. after a first performance of process
step (2). After the
performance of process step (1), mineral oil production is repeated with the
new performance of
process step (2).
The examples which follow are intended to illustrate the invention in detail:
Preparation of the monomer used
Hydroxybutyl vinyl ether alkoxylate with 22 EO units and 12 Pe0 units
H2C=CH-0-(CH2)4-0-(-CH2-CH2-0-)22-(-CH2-CH(C3H7)-0-)12-H
A 11 stirred stainless steel autoclave is initially charged with 44.1 g of
hydroxybutyl vinyl ether.
Subsequently, 3.12 g of KOMe (32% in Me0H) are metered in and the methanol is
drawn off at
80 C and approx. 30 mbar. This is followed by heating to 140 C, purging of the
reactor with
nitrogen and establishment of a nitrogen pressure of 1.0 bar. Then 368 g of EO
are metered in
within approx. 3 h. After continued reaction at 140 C for a half hour, the
reactor is cooled to
125 C, and a total of 392 g of pentene oxide are metered in over the course of
3.5 h. The
reaction continues overnight.
The product has an OH number of 31.9 mg KOH/g (theory: 26.5 mg KOH/g). The OH
number is
determined by means of the ESA method.
PF 72130 CA 02826635 2013-08-06
29
Preparation of polymer 1 (inventive):
Preparation of a copolymer from 2% by weight of monomer M1, 50% by weight of
acrylamide
and 48% by weight of 2-acrylamido-2-methylpropanesulfonic acid (by means of
gel
polymerization)
A plastic bucket with magnetic stirrer, pH meter and thermometer is initially
charged with
121.2 g of a 50% aqueous solution of NaATBS (2-acrylamido-2-
methylpropanesulfonic acid,
sodium salt), and then 155 g of distilled water, 0.6 g of a defoamer (Surfynol
DF-58), 0.2 g of a
silicone defoamer (Baysilon EN), 2.3 g of monomer Ml, 114.4 g of a 50%
aqueous solution of
acrylamide, 1.29 of pentasodium diethylenetriaminepentaacetate (complexing
agent, as a 5%
aqueous solution) and 2.4 g of a nonionic surfactant (nonylphenol, alkoxylated
with 10 units of
ethylene oxide) are added successively.
After adjusting the pH with a 20% or 2% sulfuric acid solution to a value of 6
and adding the rest
of the water, the monomer solution is adjusted to the start temperature of 5
C. The total amount
of water is such that ¨ after the polymerization ¨ a solids concentration of
approx. 30 to 36% by
weight is attained. The solution is transferred to a thermos flask, a
temperature sensor for the
temperature recording is provided and the solution is purged with nitrogen for
30 minutes. The
polymerization is then initiated by adding 1.6 ml of a 10% aqueous solution of
a water-soluble
cationic azo initiator 2,2'-azobis(2-amidinopropane) dihydrochloride (Wako V-
50), 0.12 ml of a
1% aqueous solution of tert-butyl hydroperoxide and 0.24 ml of a 1% sodium
sulfite solution.
After the initiators have been added, the temperature rises to approx. 80 C
within 15 to 30 min.
After 30 min, the reaction vessel is placed into a drying cabinet at approx.
80 C for approx. 2 h
to complete the polymerization. The total duration of the polymerization is
approx. 2 h to 2.5 h.
A gel block is obtained, which, after the polymerization has ended, is
comminuted with the aid of
a meat grinder. The gel granules obtained are dried in a fluidized bed dryer
at 55 C for two
hours. This gives white, hard granules which are converted to a pulverulent
state by means of a
centrifugal mill. This gives a copolymer with a weight-average molecular
weight of approx. 1*106
g/mol to 30*106 g/mol.
Comparative polymer 1:
This is a commercially available copolymer for polymer flooding, formed from
approx. 50% by
weight of acrylamide and approx. 50% by weight of 2-acrylamido-2-
methylpropanesulfonic acid
with a weight-average molecular weight M of approx. 8 to 13*106 g/mol. In
contrast to the
copolymers used in accordance with the invention, it does not comprise any
hydrophobically
associating monomers.
PF 72130 CA 02826635 2013-08-06
Preparation of polymer 2 (inventive):
Preparation of a copolymer from 2% by weight of monomer 1, 93% by weight of
acrylamide and
5% by weight of t-butyl acrylate
5
A 2 I three-neck flask with stirrer and thermometer was initially charged with
337.5 g of water.
0.06 g of sodium hypophosphite, 0.5 g of ammonium persulfate and 7.46 g of
butyl acrylate
were added successively to the reaction flask. Then it was purged with
nitrogen for 45 min.
In parallel to this, a monomer solution consisting of 91.2 g of water, 272.56
g of 50 percent
10 aqueous acrylamide solution, 1.03 g of 50 percent aqueous Trilon C
solution, 2.93 g of
monomer Ml, 1.03 g of sodium dodecylsulfate, 0.1 g of sodium hypophosphite and
0.5 g of
potassium bromate was prepared.
24.0 g of a 7 percent aqueous sodium sulfite solution were likewise prepared
as an initiator
solution. After the inertization, the monomer solution and the initiator
solution were metered in
15 in parallel with a peristaltic pump. The metering time of the monomer
solution was 2 h, and that
of the initiator solution 2.5 h. In the course of this, it was ensured that
the internal temperature
did not exceed 50 C. After the metered addition had ended, the mixture was
heated to 60 C.
Subsequently, 0.375 g of VA044 was added as a further initiator for residual
monomer
reduction, and the mixture was stirred at 60 C for 1 h. Finally, 0.75 g of
Acticide MBS was
20 dissolved in 13.5 g of water and added. Then the mixture was cooled and
transferred.
Preparation of polymer 3 (inventive):
Preparation of a copolymer from 4% by weight of monomer 1, 91% by weight of
acrylamide and
25 5% by weight of t-butyl acrylate
Polymer 3 was prepared like polymer 2, except that the amounts of the monomers
were altered
as follows:
50 percent aqueous acrylamide solution 266.71 g
30 Butyl acrylate 7.46 g
Monomer 1 5.85 g
Preparation of polymer 4 (inventive):
Preparation of a copolymer from 1% by weight of monomer 1, 94% by weight of
acrylamide and
5% by weight of t-butyl acrylate
Polymer 4 was prepared like polymer 2, except that the amounts of the monomers
were altered
as follows:
50 percent aqueous acrylamide solution 275.51 g
Butyl acrylate 7.46 g
Monomer 1 1.46 g
PF 72130 CA 02826635 2013-08-06
31
Preparation of polymer 5 (inventive):
Preparation of a copolymer from 0.5% by weight of monomer 1, 94.5% by weight
of acrylamide
and 5% by weight of t-butyl acrylate
Polymer 5 was prepared like polymer 2, except that the amounts of the monomers
were altered
as follows:
Example polymer 4:
50 percent aqueous acrylamide solution 276.99 g
Butyl acrylate 7.46 g
Monomer 1 0.73 g
Preparation of polymer 6 (inventive):
Preparation of a copolymer from 0.5% by weight of monomer 1, 95.5% by weight
of acrylamide
and 4% by weight of sodium acrylate (by means of suspension polymerization)
A 2 I jacketed reactor with stirrer and water separator is initially charged
with 600 g of Exxsol
D40, 4 g of a 25 percent solution of a polymeric stabilizer for water-in-oil
suspensions are added
and the mixture is heated to 35 C. In the course of which, inertization is
effected by purging with
nitrogen for 90 min. In a beaker, 310.40 g of a 50 percent aqueous acrylamide
solution, 18.05 g
of a 35 percent sodium acrylate solution, 0.6 g of a 50 percent aqueous Trilon
C, 0.81 g of
monomer 1 and 10.129 of water are mixed. 10 percent sulfuric acid is used to
adjust the pH to
6Ø Then 1.62 of a 10 percent aqueous solution of V50 (Wako) and 11.52 g of a
1 percent
sodium sulfite solution are added to the monomer solution. The monomer
solution is introduced
into the inertized oil phase and stirred at 350 rpm for 4 min. Thereafter, 3.6
g of a 1 percent
aqueous solution of tert-butyl hydroperoxide are added. The polymerization
commences rapidly
and reaches 85 C after a few minutes. After 15 min, the mixture is heated to
boiling and the
water is distilled off by azeotropic means. After the complete removal of the
water, the mixture is
cooled to room temperature and filtered.
Preparation of polymer 7 (inventive):
Preparation of a copolymer from 1% by weight of monomer 1, 95% by weight of
acrylamide and
4% by weight of sodium acrylate
Polymer 7 was prepared like polymer 6, except that the amounts of the monomers
were altered
as follows:
50 percent aqueous acrylamide solution 308.70 g
35 percent aqueous sodium acrylate solution 18.05 g
Monomer 1 1.62 g
PF 72130 CA 02826635 2013-08-06
32
Preparation of polymer 8 (inventive):
Preparation of a copolymer from 2% by weight of monomer 1, 94% by weight of
acrylamide and
4% bye0ht of sodium acrylate
Polymer 8 was prepared like polymer 6, except that the amounts of the monomers
were altered
as follows:
50 percent aqueous acrylamide solution 305.50 g
35 percent aqueous sodium acrylate solution 18.05 g
Monomer 1 3.24 g
Preparation of polymer 9 (inventive):
Preparation of a copolymer from 4% by weight of monomer 1, 92% by weight of
acrylamide and
4% by weight of sodium acrylate
Polymer 9 was prepared like polymer 26, except that the amounts of the
monomers were
altered as follows:
50 percent aqueous acrylamide solution 299.06 g
35 percent aqueous sodium acrylate solution 18.05 g
Monomer 1 6.48 g
Preparation of comparative polymer 2:
Preparation of a copolymer from 0.5% by weight of acrylic acid, 39.5% by
weight of acrylamide
and 60% by weight of 2-acrylamido-2-methylpropanesulfonic acid
Polymer C2 was prepared like polymer 6 (suspension polymerization), except
that the
abovementioned monomers were used in the amounts specified.
Preparation of polymer 10 (inventive)
Preparation of a copolymer from 3.1% by weight of sodium acrylate, 96.4% by
weight of
acrylamide and 0.5% by weight of monomer 1
The procedure was as in example 1 (gel polymerization), except that the
abovementioned
monomers were used in the amounts specified.
PF 72130 CA 02826635 2013-08-06
33
Preparation of polymer 11 (inventive)
Preparation of a copolymer from 3.1% by weight of sodium acrylate, 95.9% by
weight of
acrylamide and 1.0% by weight of monomer 1
The procedure was as in example 1 (gel polymerization), except that the
abovementioned
monomers were used in the amounts specified.
Preparation of polymer 12 (inventive)
Preparation of a copolymer from 3.1% by weight of sodium acrylate, 94.9% by
weight of
acrylamide and 2.0% by weight of monomer 1
The procedure was as in example 1 (gel polymerization), except that the
abovementioned
monomers were used in the amounts specified.
Preparation of polymer 13 (inventive)
Preparation of a copolymer from 3.1% by weight of sodium acrylate, 92.8% by
weight of
acrylamide and 4.1% by weight of monomer 1
The procedure was as in example 1 (gel polymerization), except that the
abovementioned
monomers were used in the amounts specified.
Preparation of comparative polymer 3:
Preparation of a copolymer from 3.1% by weight of sodium acrylate, 96.9% by
weight of
acrylamide
The procedure was as in example 1 (gel polymerization), except that the
abovementioned
monomers were used in the amounts specified. No monomer 1 was used.
Performance tests of polymers 1, 10 to 13 and Cl, C2, C3:
In the test series which follow, the thermal thickening action of the polymers
used is tested.
Test series 1:
Solutions of polymers 1 and Cl were made up in a concentration of in each case
1200 ppm in
tap water, and the viscosity of each of the solutions was measured at 30 C, 60
C, 90 C and
120 C. Figure 1 shows the result of the viscosity measurements.
PF 72130 CA 02826635 2013-08-06
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It is clearly evident that the viscosity of the polymer used in accordance
with the invention rises
with rising temperature up to a viscosity maximum at 60 C and then decreases
again, while the
comparative polymer has a falling viscosity with rising temperature. The
polymer used in
accordance with the invention can thus be injected into the mineral oil
formation low
temperatures, and follows the preferred flow paths. The viscosity increases in
the course of
heating under the sole influence of the deposit temperature and thus leads to
the formation of a
highly viscous gel in the flow paths.
Test series 2:
A 2% solution of inventive polymer 1 in tap water was prepared. This solution
was highly
viscous but still free-flowing at room temperature, especially at high shear
rates as occur in the
course of pumping of the polymer solution. In the course of heating to 60 C at
a low shear rate,
the viscosity of the polymer solution rose significantly and it was barely
free-flowing any longer.
Test series 3:
The Brookfield viscosity (in mPas) of solutions of 0.5% by weight of polymers
10 to 13 and C2
and C3 in fresh water and in a salt solution was measured at various
temperatures.
The salt solution had the following composition:
Salt Amount [g/I]
NaCI 23.5
Na2SO4*10 H20 8.9
KCI 0.7
MgC12*6 H20 10.6
CaCl2*2 H20 2.2
NaHCO3 0.2
Total 46.1
The results are compiled in tables 1 and 2:
T [ C] Viscosity ri [m Pas]
Polymer 10 Polymer 11 Polymer 12 Polymer 13 C2
C3
0.5%M1 1%M1 2%M1 4.1%M1
20 78 150 252 280 500 45
40 75 345 700 800 350 65
60 40 550 1860 1700 250 90
80 2750
Table 1: Results of the viscosity measurements in fresh water
PF 72130 CA 02826635 2013-08-06
T [ C] Viscosity 1 [m Pas]
Polymer 10 Polymer 11 Polymer 12 Polymer 13 02
C3
0.5%M1 1%M1 2%M1 4.1%M1
20 120 170 390 155 40 85
180 470 , 1700 550 20 45
60 250 1000 2500 1000 15 30
80 3300
Table 2: Results of the viscosity measurements in salt water
The results show that the polymers which comprise monomer M1 and are to be
used in
5 accordance with the invention exhibit excellent thermal thickening
characteristics in salt water.
Comparative polymers C2 and C3 have only very low viscosities in salt water,
and the
viscosities decrease in the course of heating. Due to these properties, the
polymers are
outstandingly suitable for blocking of underground formations. The polymers
can be injected
efficiently at low viscosities and the viscosity increases very significantly
underground.
Performance tests of polymers 2 to 9:
Measurement of Brookfield viscosity
The Brookfield viscosity of each of the polymers used was measured in aqueous
solution at
room temperature. The results are compiled in tables 3 and 4 below.
Polymer No. Composition
Brookfield viscosity [mPas]
acrylamide/tert-butyl acrylate/monomer M1 at RT
[in % by wt.]
(aqueous solution, 20% by wt.)
2 93/5/2 208
3 91/5/4 440
4 94/5/1 260
5 945/5/0.5 260
Table 3: Viscosities of polymers 3 to 5
Polymer No. Composition
Brookfield Viscosity [mPas]
acrylamide/sodium acrylate/monomer M1 in water at RT
[in % by wt.]
0.5% by weight 1% by weight
of polymer of
polymer
6 95.5/4/0.5 8 28
7 95/4/1 90 150
8 94/4/2 90 190
PF 72130 CA 02826635 2013-08-06
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9 92/4/4 210 320
Table 4: Viscosities of polymers 6 to 9
Production of polymer gels
In order to be able to test the properties of the polymers used with regard to
gel formation
properties under formation conditions, gel formulation was studied in seawater
at 80 C. The
combination of 80 C and salt-containing water simulates the conditions in a
typical mineral oil
deposit.
The t-butyl ester units of copolymers 2 to 5 are hydrolyzed to an extent of
approx. 50% at 80 C
in seawater within 2 h, and form COOH groups.
A synthetic seawater of the following composition was used:
500 g of deionized water
1.13 g of NaHCO3
13.60 g of CaCl2 X 6 H20
28.34 g of MgCl2 x 6 H20
39.70 g of MgSO4 x 6 H20
158.72 g of NaCI
In addition, crosslinkers were added in some experiments. The crosslinkers
used were:
Crosslinker 1: 50% by weight aqueous chromium(III) acetate solution
Crosslinker 2: 33% by weight of aqueous polyethyleneimine solution, Mw
approx.
75 000 g/mol, pH 11.4 (Lupasol PS)
Crosslinker 3: 40% by weight of aqueous polyethyleneimine solution, M,,
approx.
25 000 g/mol, pH 11.0 (BasominO, G 500)
The gel formation tests were conducted as follows.
- 100 ml of a 5% solution of the polymers in seawater (or in fresh
water for comparative
purposes) are initially charged in a screwtop bottle. If crosslinkers are
used, the
crosslinker is added by means of a plastic syringe and the screwtop bottle is
closed. The
bottle is shaken until the mixture is homogeneous and then placed in the
drying cabinet
at 80 C.
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- The sample is assessed visually at 5 minute intervals, by placing the
bottle on its lid and
assessing the flow characteristics of the contents and assigning a gel code.
The time
when gel code B is attained is noted. The appearance of the gels and the
assignment of
the gel codes is detailed below.
Gel codes
A ¨ no detectable gel formed. The gel appears to have the same viscosity
(fluidity) as the
original polymer solution, and no gel can be discovered visually.
B ¨ highly mobile gel. The gel appears to be only a bit tackier than the
original polymer solution
of relatively low viscosity.
C ¨ flowing gel. The majority of the obviously detectable gel flows into the
bottle lid and back.
D ¨ moderately flowing gel. A small amount (¨ 5-15%) of the gel flows into the
bottle lid and
back, usually characterized as a 'tonguing' gel (i.e. once the gel hangs out
of the bottle, it can
flow back into the bottle when the bottle is slowly turned upright).
E ¨ barely flowing gel. The gel flows slowly into the bottle lid and/or a
significant portion (> 15%)
of the gel does not flow into the bottle lid and back.
F ¨ highly deformable gel. The gel does not flow into the bottle lid and back
(gel barely flows to
reach the bottle lid).
G ¨ moderately deformable non-flowing gel. Half of the gel flows to the bottle
lid and back.
H ¨ an only slightly deformable, non-flowing gel. The gel surface deforms
slightly and the
deformation is reversed again.
I ¨ rigid gel. There is no longer any gel surface deformation.
J ¨ the ringing of rigid gel. After knocking on the bottle, the gel rings like
a tuning fork and
mechanical vibration can be perceived.
The results and test conditions for polymers 2 to 5 are shown in table 5
below, and the results
for polymers 6 to 9 in table 6 below.
, PF 72130 CA 02826635 2013-08-06
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Polymer Amount of Medium Crosslinker Gel code B Gel
code J
No. polymer after [min] after
[min]
[% by wt.]
2 5 Fresh water Crosslinker1/250 ppm
45 55
3 5 Fresh water Crosslinker1/250 ppm
60 70
4 5 Fresh water Crosslinker1/250 ppm
55 65
5 Fresh water Crosslinker1/250 ppm 55 70
2 5 Seawater Crosslinker 1/250 ppm 50 60
3 5 Seawater Crosslinker 1/250 ppm 65 70
4 5 Seawater Crosslinker 1/250 ppm 55 70
5 5 Seawater Crosslinker 1/250 ppm 50 75
2 5 , Fresh water
Crosslinker 2/2000 ppm 3 h 10 min 3 h 30 min
3 5 Fresh water
Crosslinker 2/2000 ppm 3 h 30 min 3 h 45 min
4 5 Fresh water
Crosslinker 2/2000 ppm 3 h 20 min 3 h 35 min
5 5 Fresh water
Crosslinker 2/2000 ppm 2 h 55 min 3 h 05 min
2 5 Fresh water Crosslinker 3/2000 ppm 10 h 50
min 13 h 10 min
3 5 Fresh water Crosslinker 3/2000 ppm 12 h 15
min 14 h 45 min
4 5 Fresh water Crosslinker 3/2000 ppm 11 h 35
min 12 h 55 min
5 5 Fresh water Crosslinker 3/2000 ppm 10 h 25
min 11 h 15 min
2 5 Seawater Crosslinker 2/2000 ppm 14 h 36 h
3 5 Seawater Crosslinker 2/2000 ppm 13 h 38 h
4 5 Seawater Crosslinker 2/2000 ppm 12.5 h 35
h
5 5 Seawater Crosslinker 2/2000 ppm 9.5 h 33
h
2 5 Seawater Crosslinker 3/2000 ppm 12 h 33 h
2 5 Seawater Crosslinker 3/2000 ppm 14 h 35 h
3 5 Seawater Crosslinker 3/2000 ppm 12 h 30 h
5 5 Seawater Crosslinker 3/2000 ppm 7 h 28 h
Table 5: Gel formation tests at 80 C, test conditions and results
PF 72130 CA 02826635 2013-08-06
,
39
Polymer Amount of Medium Time until Final strength
No. polymer attainment of
Attained after Gel
code
[% by wt.] gel code
[min]
attained
B [min]
6 3 Seawater 15 30 J
7 3 Seawater 15 30 J
8 2 Seawater 15 30 I
9 2 Seawater 15 30 I
Table 6: Gel formation tests at 80 C, test conditions and results; the
crosslinker was used in
each case in an amount of 250 ppm.
