Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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As originally filed
Process for extracting mineral oil using surfactants based on butylene oxide-
containing
alkyl alkoxylates
Description
The invention relates to a process for mineral oil extraction by means of
Winsor Type III
microemulsion flooding, in which an aqueous surfactant formulation comprising
at least
one ionic surfactant of the general formula
R1-0-(D),-(B)m-(A)1-XY- M+
is injected through injection boreholes into a mineral oil deposit, and crude
oil is
withdrawn from the deposit through production boreholes. The invention further
relates
to ionic surfactants of the general formula, and to processes for preparation
thereof.
In natural mineral oil deposits, mineral oil is present in the cavities of
porous reservoir
rocks which are sealed toward the surface of the earth by impervious top
layers. The
cavities may be very fine cavities, capillaries, pores or the like. Fine pore
necks may,
for example, have a diameter of only about 1 p.m. As well as mineral oil,
including
fractions of natural gas, a deposit comprises water with a greater or lesser
salt content.
In mineral oil extraction, a distinction is generally drawn between primary,
secondary
and tertiary extraction. In primary extraction, the mineral oil flows, after
commencement
of drilling of the deposit, of its own accord through the borehole to the
surface owing to
the autogenous pressure of the deposit.
After primary extraction, secondary extraction is therefore used. In secondary
extraction, in addition to the boreholes which serve for the extraction of the
mineral oil,
the so-called production bores, further boreholes are drilled into the mineral
oil-bearing
formation. Water is injected into the deposit through these so-called
injection bores in
order to maintain the pressure or to increase it again. As a result of the
injection of the
water, the mineral oil is forced slowly through the cavities into the
formation,
proceeding from the injection bore in the direction of the production bore.
However, this
only works for as long as the cavities are completely filled with oil and the
more viscous
oil is pushed onward by the water. As soon as the mobile water breaks through
cavities, it flows on the path of least resistance from this time, i.e.
through the channel
formed, and no longer pushes the oil onward.
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By means of primary and secondary extraction, generally only approx. 30 to 35%
of the
amount of mineral oil present in the deposit can be extracted.
It is known that the mineral oil yield can be enhanced further by measures for
tertiary
oil extraction. A review of tertiary oil extraction can be found, for example,
in "Journal of
Petroleum Science of Engineering 19 (1998)", pages 265 to 280. Tertiary oil
extraction
includes, for example, thermal methods in which hot water or steam is injected
into the
deposit. This lowers the viscosity of the oil. The flow medium used may
likewise be
gases such as CO2 or nitrogen.
Tertiary mineral oil extraction also includes methods in which suitable
chemicals are
used as assistants for oil extraction. These can be used to influence the
situation
toward the end of the water flow and as a result also to extract mineral oil
hitherto held
firmly within the rock formation.
Viscous and capillary forces act on the mineral oil which is trapped in the
pores of the
deposit rock toward the end of the secondary extraction, the ratio of these
two forces
relative to one another being determined by the microscopic oil separation. By
means
of a dimensionless parameter, the so-called capillary number, the action of
these
forces is described. It is the ratio of the viscosity forces (velocity x
viscosity of the
forcing phase) to the capillary forces (interfacial tension between oil and
water x
wetting of the rock):
c = ________________________________________
cost9
In this formula, p is the viscosity of the fluid mobilizing mineral oil, V is
the Darcy
velocity (flow per unit area), 6 is the interfacial tension between liquid
mobilizing
mineral oil and mineral oil, and 6' is the contact angle between mineral oil
and the rock
(C. Melrose, C.F. Brandner, J. Canadian Petr. Techn. 58, Oct. ¨ Dec., 1974).
The
higher the capillary number, the greater the mobilization of the oil and hence
also the
degree of oil removal.
It is known that the capillary number toward the end of secondary mineral oil
extraction
is in the region of about 10-6 and that it is necessary to increase the
capillary number to
about 10-3 to 10-2 in order to be able to mobilize additional mineral oil.
For this purpose, it is possible to conduct a particular form of the flooding
method -
what is known as Winsor type III microemulsion flooding. In Winsor type III
microemulsion flooding, the injected surfactants should form a Winsor type III
microemulsion with the water phase and oil phase present in the deposit. A
Winsor
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type III microemulsion is not an emulsion with particularly small droplets,
but rather a
thermodynamically stable, liquid mixture of water, oil and surfactants. The
three
advantages thereof are that
- a very low interfacial tension 6 between mineral oil and aqueous phase is
thus
achieved,
- it generally has a very low viscosity and as a result is not trapped
in a porous
matrix,
- it forms with even the smallest energy inputs and can remain stable over
an
infinitely long period (conventional emulsions, in contrast, require high
shear
forces which predominantly do not occur in the reservoir, and are merely
kinetically stabilized).
The Winsor type III microemulsion is in an equilibrium with excess water and
excess
oil. Under these conditions of microemulsion formation, the surfactants cover
the oil-
water interface and lower the interfacial tension more preferably to values
of
< 10-2 mN/m (ultra-low interfacial tension). In order to achieve, an optimal
result, the
proportion of the microemulsion in the water-microemulsion-oil system, with a
defined
amount of surfactant, should by its nature be at a maximum, since this allows
lower
interfacial tensions to be achieved.
In this manner, it is possible to alter the form of the oil droplets
(interfacial tension
between oil and water is lowered to such a degree that the smallest interface
state is
no longer favored and the spherical form is no longer preferred), and they can
be
forced through the capillary openings by the flooding water.
When all oil-water interfaces are covered with surfactant, in the presence of
an excess
amount of surfactant, the Winsor type III microemulsion forms. It thus
constitutes a
reservoir for surfactants which cause a very low interfacial tension between
oil phase
and water phase. By virtue of the Winsor type III microemulsion being of low
viscosity,
it also migrates through the porous deposit rock in the flooding process
(emulsions, in
contrast, can become trapped in the porous matrix and block deposits). When
the
Winsor type III microemulsion meets an oil-water interface as yet uncovered
with
surfactant, the surfactant from the microemulsion can significantly lower the
interfacial
tension of this new interface, and lead to mobilization of the oil (for
example by
deformation of the oil droplets).
The oil droplets can subsequently combine to a continuous oil bank. This has
two
advantages:
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Firstly, as the continuous oil bank advances through new porous rock, the oil
droplets
present there can coalesce with the bank.
Moreover, the combination of the oil droplets to give an oil bank
significantly reduces
the oil-water interface and hence surfactant no longer required is released
again.
Thereafter, the surfactant released, as described above, can mobilize oil
droplets
remaining in the formation.
Winsor type III microemulsion flooding is consequently an exceptionally
efficient
process, and requires much less surfactant compared to an emulsion flooding
process.
In microemulsion flooding, the surfactants are typically optionally injected
together with
co-solvents and/or basic salts (optionally in the presence of chelating
agents).
Subsequently, a solution of thickened polymer is injected for mobility
control. A further
variant is the injection of a mixture of thickening polymer and surfactants,
co-solvents
and/or basic salts (optionally with chelating agent), and then a solution of
thickening
polymer for mobility control. These solutions should generally be clear in
order to
prevent blockages of the reservoir.
The requirements on surfactants for tertiary mineral oil extraction differ
significantly
from requirements on surfactants for other applications: suitable surfactants
for tertiary
oil extraction should reduce the interfacial tension between water and oil
(typically
approx. 20 mN/m) to particularly low values of less than 10-2mN/m in order to
enable
sufficient mobilization of the mineral oil. This has to be done at the
customary deposit
temperatures of approx. 15 C to 130 C and in the presence of water of high
salt
contents, more particularly also in the presence of high proportions of
calcium and/or
magnesium ions; the surfactants thus also have to be soluble in deposit water
with a
high salt content.
To fulfill these requirements, there have already been frequent proposals of
mixtures of
surfactants, especially mixtures of anionic and nonionic surfactants.
US 3,890,239 discloses a combination of organic sulfonates with alkyl
alkoxylates of
the C8-C20¨AO¨H type (AO = alkylene oxide having 2 to 6 carbon atoms) with
anionic
surfactants of the C8-C20¨A0¨sulfate or C8-C20¨AO¨sulfonate type. The
specification of
the alkylene oxides is only kept very general in the context of the disclosure
of
US 3,890,239. However, there are only examples which comprise exclusively EO.
US 4,448,697 claims the use of alkyl alkoxylates of the CI-Cs ¨ (A0)1.40 ¨
E0,10 ¨ H
type in combination with an anionic surfactant. AO may be 1,2-butylene oxide
or
2,3-butylene oxide.
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US 4,460,481 describes surfactants of the alkylaryl alkoxy sulfate or
sulfonate type. The
alkylene oxide may be ethylene oxide, propylene oxide or butylene oxide. There
exists the
proviso that ethylene oxide makes up the majority of the alkylene oxides.
There is no more
detailed description of the butylene oxide.
The use parameters, for example type, concentration and mixing ratio of the
surfactants used
with respect to one another, are therefore adjusted by the person skilled in
the art according to
the conditions existing in a given oil formation (for example temperature and
salt content).
As described above, mineral oil production is proportional to the capillary
number. The lower
the interfacial tension between oil and water, the higher it is. The higher
the mean number of
carbon atoms in the crude oil, the more difficult it is to achieve low
interfacial tension. Suitable
surfactants for low interfacial tensions are those which possess a long alkyl
radical. The longer
the alkyl radical, the better it is possible to reduce the interfacial
tensions. However, the
availability of such compounds is very limited.
It is therefore an object of the invention to provide a particularly efficient
surfactant for use for
surfactant flooding, and an improved process for tertiary mineral oil
extraction.
Accordingly, a process is provided for tertiary mineral oil extraction by
means of Winsor type
Ill microemulsion flooding, in which an aqueous surfactant formulation
comprising at least one
ionic surfactant, for the purpose of lowering the interfacial tension between
oil and water to
<0.1 mN/m, is injected through at least one injection borehole into a mineral
oil deposit, the
interfacial tension between oil and water is lowered to values of <0.1 mN/m,
preferably to
values of < 0.05 mN/m, more preferably to values of < 0.01 mN/m, and crude oil
is withdrawn
from the deposit through at least one production borehole, wherein the
surfactant formulation
comprises at least one surfactant of the general formula
R1O(D)n(B)m(A)iXY M, where
R1 is a linear or branched, saturated or unsaturated, aliphatic
and/or aromatic
hydrocarbon radical having 8 to 30 carbon atoms,
A is ethyleneoxy,
B is propyleneoxy, and
D is butyleneoxy,
is from 0 to 99,
m is from 0 to 99 and
n is from 1 to 99,
X is an alkyl or alkylene group having 0 to 10 carbon atoms,
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M+ is a cation, and
Y- is selected from the group of sulfate groups, sulfonate groups,
carboxylate groups
and phosphate groups, where
the A, B and D groups may be distributed randomly, alternatingly, or in the
form of two, three,
four or more blocks in any sequence, the sum of I + m + n is in the range from
3 to 99 and the
proportion of 1,2- butylene oxide, based on the total amount of butylenoxy, is
at least 80%.
Additionally provided has been a surfactant mixture for mineral oil
extraction, which comprises
at least one ionic surfactant of the general formula defined above.
With regard to the invention, the following should be stated specifically:
In the above-described process according to the invention for mineral oil
extraction by means
of Winsor type ill microemulsion flooding, an aqueous surfactant formulation
comprising at
least one surfactant of the general formula is used. It may additionally
comprise further
surfactants and/or other components.
In the process according to the invention for tertiary mineral oil extraction
by means of Winsor
type III microemulsion flooding, the use of the inventive surfactant lowers
the interfacial tension
between oil and water to values of <0.1 mN/m, preferably to < 0.05 mN/m, more
preferably to
<0.01 mN/m. The interfacial tension between oil and water is thus lowered to
values in the
range from 0.1 mN/m to 0.0001 mN/m, preferably to values in the range from
0.05 mN/m to
0.0001 mN/m, more preferably to values in the range from 0.01 mN/m to 0.0001
mN/m.
The at least one surfactant can be encompassed by the general formula R1-0-
(D)n-(B)m-(A)I-
XY- M. As a result of the preparation, it is also possible for a plurality of
different surfactants
of the general formula to be present in the surfactant formulation.
The R1 radical is a straight-chain or branched aliphatic and/or aromatic
hydrocarbon radical
having 8 to 30 carbon atoms, preferably 9 to 30 carbon atoms, more preferably
10 to 28 carbon
atoms.
In a particularly preferred embodiment of the invention, the R1 radical is iso-
C17H35 or a
commercial fatty alcohol mixture consisting of linear C16F133 and C181-137 or
derived from
the commercially available C16 Guerbet alcohol 2-hexyldecan-1-ol or derived
from the
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commercially available C24 Guerbet alcohol 2-decyltetradecanol or derived from
the
commercially available C28 Guerbet alcohol 2-dodecylhexadecanol.
More preferably, in linear alcohols n = 3 to 10 and m = 5 to 9, while, in
branched
alcohols n = 2 to 10 and m =. 5 to 9. It is preferred here in each case that D
is 1,2-
butylene oxide to an extent of more than 80%, and that the alkylene oxides,
beginning
at the alcohol, have the sequence D ¨ B ¨ A. The alkylene oxides are arranged
in
blocks to an extent of more than 90%.
-- Particular preference is given to a straight-chain or branched aliphatic
hydrocarbon
radical, especially a straight-chain or branched aliphatic hydrocarbon radical
having 10
to 28 carbon atoms.
A branched aliphatic hydrocarbon radical generally has a degree of branching
of 0.1 to
-- 5.5, preferably 1 to 3.5. The term "degree of branching" is defined here in
a manner
known in principle as the number of methyl groups in a molecule of the alcohol
minus
1. The mean degree of branching is the statistical mean of the degrees of
branching of
all molecules in a sample.
-- In the above formula, A means ethyleneoxy. B means propyleneoxy and D means
butyleneoxy.
In the above-defined general formula I, m and n are each integers. It is,
however, clear
to the person skilled in the art in the field of polyalkoxylates that this
definition is the
-- definition of a single surfactant in each case. In the case of presence of
surfactant
mixtures or surfactant formulations which comprise a plurality of surfactants
of the
general formula, the numbers I, m and n are each mean values over all
molecules of
the surfactants, since the alkoxylation of alcohol with ethylene oxide and/or
propylene
oxide and/or butylene oxide in each case affords a certain distribution of
chain lengths.
-- This distribution can be described in a manner known in principle by the
polydispersity
D. D = Mw/Mn is the quotient of the weight-average molar mass and the number-
average molar mass. The polydispersity can be determined by means of the
methods
known to those skilled in the art, for example by means of gel permeation
chromatography.
In the above general formula I is from 0 to 99, preferably 1 to 40, more
preferably 1 to
20.
In the above general formula m is from 0 to 99, preferably 1 to 20, more
preferably 5 to
9.
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In the above general formula n is from 1 to 99, preferably 2 to 30, more
preferably 2 to
10.
According to the invention, the sum of I + m + n is a number in the range from
3 to 99,
preferably in the range from 5 to 50, more preferably in the range from 8 to
39.
According to the present invention the proportion of 1,2-butyleneoxy, based on
the total
amount of butyleneoxy (D), is at least 80%, preferably at least 85%,
preferably at least
90%, more preferably at least 95%, of 1,2-butyleneoxy.
The ethyleneoxy (A), propyleneoxy (B) and butyleneoxy (D) group(s) are
randomly
distributed, alternatingly distributed, or are in the form of two, three,
four, five or more
blocks in any sequence.
In a preferred embodiment of the invention, in the presence of a plurality of
different
alkyleneoxy blocks, the sequence R1, butyleneoxy block, propyleneoxy block,
ethyleneoxy block is preferred. The butylene oxide used should comprise 80% of
1,2-
butylene oxide, preferably > 90% of 1,2-butylene oxide.
In the above general formula, X is an alkylene group or alkenylene group
having 0 to
10, preferably 0 to 3 carbon atoms. The alkylene group is preferably a
methylene,
ethylene or propylene group.
In the prior art cited, there is often no specific information with regard to
the description
of 04 epoxides. This may generally be understood to mean 1,2-butylene oxide,
2,3-butylene oxide, isobutylene oxide, and mixtures of these compounds. The
composition is generally dependent on the C4 olefin used, and to a certain
degree on
the oxidation process.
In the above general formula Y is a sulfonate, sulfate or carboxyl group or
phosphate
group.
In the above formula M+ is a cation, preferably a cation selected from the
group of Na,
K+, Li, NH4, H+, Mg2+ and Ca2+.
The surfactants of the general formula can be prepared in a manner known in
principle
by alkoxylating corresponding alcohols R1-OH. The performance of such
alkoxylation is
known in principle to those skilled in the art. It is likewise known to those
skilled in the
art that the molar mass distribution of the alkoxylates can be influenced
through the
reaction conditions, especially the selection of the catalyst.
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The surfactants of the general formula can preferably be prepared by base-
catalyzed
alkoxylation. In this case, the alcohol R1-OH can be admixed in a pressure
reactor with
alkali metal hydroxides, preferably potassium hydroxide, or with alkali metal
alkoxides,
for example sodium methoxide. Water still present in the mixture can be drawn
off by
means of reduced pressure (for example < 100 mbar) and/or increasing the
temperature (30 to 150 C). Thereafter, the alcohol is present in the form of
the
corresponding alkoxide. This is followed by intertization with inert gas (for
example
nitrogen) and stepwise addition of the alkylene oxide(s) at temperatures of 60
to 180 C
up to a maximum pressure of 10 bar. In a preferred embodiment, the alkylene
oxide is
metered in initially at 130 C. In the course of the reaction, the temperature
rises up to
170 C as a result of the heat of reaction released. In a further preferred
embodiment of
the invention, the butylene oxide is first added at a temperature in the range
from 135
to 145 C, then the propylene oxide is added at a temperature in the range from
130 to
145 C, and then the ethylene oxide is added at a temperature in the range from
125 to
145 C. At the end of the reaction, the catalyst can be centralized, for
example, by
adding acid (for example acetic acid or phosphoric acid) and filtered off if
required.
However, the alkoxylation of the alcohols R1-OH can also be undertaken by
means of
other methods, for example by acid-catalyzed alkoxylation. In addition, it is
possible to
use, for example double hydroxide clays, as described in DE 4325237 Al, or it
is
possible to use double metal cyanide catalysts (DMC catalysts). Suitable DMC
catalysts are disclosed, for example in DE 10243361 Al, especially in
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 R1-0H 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 1000
ppm of
catalyst based on the mixture are used, and the catalyst can remain in the
product
owing to this small amount. The amount of catalyst may generally be less than
1000 ppm, for example 250 ppm or less.
The anionic group is finally introduced. This is known in principle to those
skilled in the
art. In the case of a sulfate group, it is possible, for example, to employ
the reaction
with sulfuric acid, chlorosulfonic acid or sulfur trioxide in a falling-film
reactor with
subsequent neutralization. In the case of a sulfonate group it is possible,
for example,
to employ the reaction with propane sultone and subsequent neutralization,
with butane
sultone and subsequent neutralization, with vinylsulfonic acid sodium salt, or
with
3-chloro-2-hydroxypropanesulfonic acid sodium salt. In the case of a
carboxylate
group, it is possible, for example, to employ the oxidation of the alcohol
with oxygen
and subsequent neutralization, or the reaction with chloroacetic acid sodium
salt.
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Further surfactants
In addition to the surfactants of the general formula, the formulation may
additionally
optionally comprise further surfactants. These are, for example, anionic
surfactants of
the alkylarylsulfonate or olefinsulfonate (alpha-olefinsulfonate or internal
5 olefinsulfonate) type and/or nonionic surfactants of the alkyl ethoxylate
or alkyl
polyglucoside type. These further surfactants may especially also be
oligomeric or
polymeric surfactants. It is advantageous to use such polymeric co-surfactants
to
reduce the amount of surfactants needed to form a microemulsion. Such
polymeric
co-surfactants are therefore also referred to as "microemulsion boosters".
Examples of
10 such polymeric surfactants comprise amphiphilic block copolymers which
comprise at
least one hydrophilic block and at least one hydrophobic block. Examples
comprise
polypropylene oxide-polyethylene oxide block copolymers, polyisobutene-
polyethylene
oxide block copolymers, and comb polymers with polyethylene oxide side chains
and a
hydrophobic main chain, where the main chain preferably comprises essentially
olefins
or (meth)acrylates as monomers. The term "polyethylene oxide" here should in
each
case include polyethylene oxide blocks comprising propylene oxide units as
defined
above. Further details of such surfactants are disclosed in WO 2006/131541 Al.
Process for mineral oil extraction
In the process according to the invention for mineral oil extraction, a
suitable aqueous
formulation of the surfactants of the general formula is injected through at
least one
injection borehole into the mineral oil deposit, and crude oil is withdrawn
from the
deposit through at least one production borehole. The term "crude oil" in this
context of
course does not mean single-phase oil, but rather the usual crude oil-water
emulsions.
In general, a deposit is provided with several injection boreholes and with
several
production boreholes.
The main effect of the surfactant lies in the reduction of the interfacial
tension between
water and oil ¨ desirably to values significantly <0.1 mN/m. After the
injection of the
surfactant formulation, known as "surfactant flooding", or preferably the
Winsor type III
"microemulsion flooding", the pressure can be maintained by injecting water
into the
formation ("water flooding") or preferably a higher-viscosity aqueous solution
of a
polymer with strong thickening action ("polymer flooding"). Also known,
however, are
techniques by which the surfactants are first of all allowed to act on the
formation. A
further known technique is the injection of a solution of surfactants and
thickening
polymers, followed by a solution of thickening polymer. The person skilled in
the art is
aware of details of the industrial performance of "surfactant flooding",
"water flooding",
and "polymer flooding", and employs an appropriate technique according to the
type of
deposit.
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For the process according to the invention, an aqueous formulation which
comprises
surfactants of the general formula is used. In addition to water, the
formulations may
optionally also comprise water-miscible or at least water-dispersible organic
substances or other substances. Such additives serve especially to stabilize
the
surfactant solution during storage or transport to the oil field. The amount
of such
additional solvents should, however, generally not exceed 50% by weight,
preferably
20% by weight. In a particularly advantageous embodiment of the invention,
exclusively
water is used for formulation. Examples of water-miscible solvents include
especially
alcohols such as methanol, ethanol and propanol, butanol, sec-butanol,
pentanol, butyl
ethylene glycol, butyl diethylene glycol or butyl triethylene glycol.
According to the invention, the proportion of the surfactants of the general
formula is at
least 30% by weight based on the proportion of all surfactants present, i.e.
the
surfactants of the general formula and optionally present surfactants. The
proportion is
preferably at least 50% by weight.
The mixture used in accordance with the invention can preferably be used for
surfactant flooding of deposits. It is especially suitable for Winsor type III
microemulsion
flooding (flooding in the Winsor III range or in the range of existence of the
bicontinuous microemulsion phase). The technique of microemulsion flooding has
already been described in detail at the outset.
In addition to the surfactants, the formulations may also comprise further
components,
for example C4- to C8 alcohols and/or basic salts (so-called "alkali
surfactant flooding").
Such additives can be used, for example, to reduce retention in the formation.
The ratio
of the alcohols based on the total amount of surfactant used is generally at
least 1:1 ¨
however, it is also possible to use a significant excess of alcohol. The
amount of basic
salts may typically range from 0.1% by weight to 5% by weight.
The deposits in which the process is employed generally have a temperature of
at least
10 C, for example 10 to 150 C, preferably a temperature of at least 15 C to
120 C.
The total concentration of all surfactants together is 0.05 to 5% by weight,
based on the
total amount of the aqueous surfactant formulation, preferably 0.1 to 2.5% by
weight.
The person skilled in the art makes a suitable selection according to the
desired
properties, especially according to the conditions in the mineral oil
formation. It is clear
here to the person skilled in the art that the concentration of the
surfactants can change
after injection into the formation because the formulation can mix with
formation water,
or surfactants can also be absorbed on solid surfaces of the formation. It is
the great
advantage of the mixture used in accordance with the invention that the
surfactants
lead to a particularly good lowering of interfacial tension.
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It is of course possible and also advisable first to prepare a concentrate
which is only
diluted on site to the desired concentration for injection into the formation.
In general,
the total concentration of the surfactants in such a concentrate is 10 to 45%
by weight.
The examples which follow are intended to illustrate the invention in detail:
Part 1: Synthesis of the surfactants
General method 1: Alkoxylation by means of KOH catalysis (applies to use of
EO, PO and/or 1,2-BuO)
In a 21 autoclave, the alcohol to be alkoxylated (1.0 eq) is admixed with an
aqueous
KOH solution which comprises 50% by weight of KOH. The amount of KOH is 0.2%
by
weight of the product to be prepared. While stirring, the mixture is dewatered
at 100 C
and 20 mbar for 2 h. This is followed by purging three times with N2,
establishment of a
feed pressure of approx. 1.3 bar of N2 and a temperature increase to 120 to
130 C.
The alkylene oxide is metered in such that the temperature remains between 125
C
and 135 C (in the case of ethylene oxide) or 130 and 140 C (in the case of
propylene
oxide) or 135 and 145 C (in the case of 1,2-butylene oxide). This is followed
by stirring
at 125 to 145 C for a further 5 h, purging with N2, cooling to 70 C and
emptying of the
reactor. The basic crude product is neutralized with the aid of acetic acid.
Alternatively,
the neutralization can also be effected with commercial magnesium silicates,
which are
subsequently filtered off. The light-colored product is characterized with the
aid of a
NMR spectrum in CDCI3, gel permeation chromatography and OH number
determination, and the yield is determined.
General method 2: Alkoxylation by means of DMC catalysis in the case
of
2,3-butylene oxide
In a 21 autoclave, the alcohol to be alkoxylated (1.0 eq) is mixed with a
double metal
cyanide catalyst (for example DMC catalyst of the Zn-Co type from BASF) at 80
C. To
activate the catalyst, approximately 20 mbar is applied at 80 C for 1 h. The
amount of
DMC is 0.1% by weight or less of the product to be prepared. This is followed
by
purging three times with N2, establishment of a feed pressure of approx. 1.3
bar of N2
and a temperature increase to 120 to 130 C. The alkylene oxide is metered in
such
that the temperature remains between 125 C and 135 C (in the case of ethylene
oxide)
or 130 and 140 C (in the case of propylene oxide) or 135 and 145 C (in the
case of
2,3-butylene oxide). This is followed by stirring at 125 to 145 C for a
further 5 h,
purging with N2, cooling to 70 C and emptying of the reactor. The light-
colored product
is characterized with the aid of a 1H NMR spectrum in CDC13, gel permeation
chromatography and OH number determination, and the yield is determined.
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General method 3: Sulfation by means of chlorosulfonic acid
In a 11 round-bottom flask, the alkyl alkoxylate to be sulfated (1.0 eq) is
dissolved in
1.5-times the amount of dichloromethane (based on percent by weight) and
cooled to 5
to 10 C. Thereafter, chlorosulfonic acid (1.1 eq) is added dropwise such that
the
temperature does not exceed 10 C. The mixture is allowed to warm up to room
temperature and is stirred under an N2 stream at this temperature for 4 h
before the
above reaction mixture is added dropwise to an aqueous NaOH solution of half
the
volume at max. 15 C. The amount of NaOH is calculated to give rise to a slight
excess
based on the chlorosulfonic acid used. The resulting pH is approx. pH 9 to 10.
The
dichloromethane is removed at max. 50 C on a rotary evaporator under gentle
vacuum.
The product is characterized by 1H NMR and the water content of the solution
is
determined (approx. 70%).
For the synthesis, the following alcohols were used.
Alcohol Description
iC17 iso-C17H35-0H; oxo alcohol, prepared by hydroformylating
isohexadecene,
which is obtained by tetrannerizing butene. The mean degree of branching of
the alcohol is 3.1.
C16C18 Commercially available fatty alcohol mixture consisting of
linear C16H33-0H
and C16H37-0F1
C16 Guerbet Commercially available C16 Guerbet alcohol (2-hexyldecan-1-
ol)
Performance tests
The surfactants obtained were used to carry out the following tests in order
to assess
the suitability thereof for tertiary mineral oil extraction.
Description of the test methods
Determination of SP*
a) Principle of the measurement:
The interfacial tension between water and oil was determined in a known manner
via
the measurement of the solubilization parameter SP*. The determination of the
interfacial tension via the determination of the solubilization parameter SP*
is a method
for approximate determination of the interfacial tension which is accepted in
the
technical field. The solubilization parameter SP* indicates how many ml of oil
are
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dissolved per ml of surfactant used in a microemulsion (Winsor type III). The
interfacial tension
o (IFT) can be calculated therefrom via the approximate formula IFT
0.3/(SP*)2, if equal
volumes of water and oil are used (C. Huh, J. Coll. Interf. Sc., Vol. 71, No.
2(1979)).
b) Procedure
To determine the SP*, a 100 ml measuring cylinder with a magnetic stirrer bar
is filled with 20
ml of oil and 20 ml of water. To this are added the concentrations of the
particular surfactants.
Subsequently, the temperature is increased stepwise from 20 to 90 C, and the
temperature
window in which a microemulsion forms is observed.
The formation of the microemulsion can be assessed visually or else with the
aid of conductivity
measurements. A triphasic system forms (upper oil phase, middle microemulsion
phase, lower
water phase). When the upper and lower phase are of equal size and do not
change over a
period of 12 h, the optimal temperature (Tot) of the microemulsion has been
found. The volume
of the middle phase is determined. The volume of surfactant added is
subtracted from this
volume. The value obtained is then divided by two. This volume is then divided
by the volume
of surfactant added. The result is noted as SP*.
The type of oil and water used to determine SP* is determined according to the
system to be
examined. It is possible either to use mineral oil itself or a model oil, for
example decane. The
water used may either be pure water or saline water, in order better to model
the conditions in
the mineral oil formation. The composition of the aqueous phase can be
adjusted, for example,
according to the composition of a particular deposit water.
Information regarding the aqueous phase used and the oil phase can be found
below in the
specific description of the tests.
Test results
A 1:1 mixture of decane and of an NaCI solution was admixed with butyl
diethylene glycol
(BDG). Butyl diethylene glycol (BDG) functions as a co-solvent and is not
included in the
calculation of SP*. To this was added a surfactant mixture composed of 3 parts
alkyl
alkoxysulfate and 1 part dodecylbenzene sulfonate (LutensitTm A-LBN 50 ex
BASF). The total
surfactant concentration is reported in percent by weight of the total volume.
In addition a 1:1 mixture out of decane and sodium chloride solution was mixed
with butyl
diethylene glycol (BDG). Butyl diethylene glycol (BDG) works as cosolvent and
was not taken
into account for SP*. Surfactant mixture consisting out of three parts alkyl
alkoxy sulfate and
one part secondary alkyl sulphonate (HostapurTM SAS 60 ex Clariant) was added.
Total
surfactant concentration in weight percent refers to aqueous phase.
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In addition, a 1:1 mixture of south German crude oil (API 33 ) and of an NaCI
solution
was admixed with butyl diethylene glycol (BDG). Butyl diethylene glycol (BDG)
functions as a
co-solvent and is not included in the calculation of SP*. To this was added a
surfactant mixture
composed of 3 parts alkyl alkoxy sulfate and 1 part dodecylbenzenesulfonate
(Lutensit A-LBN
50 ex BASF). The total surfactant concentration is reported in percent by
weight of the total
volume.
In two further tests a 1:1 mixture out of crude oil from southern parts of
Germany (API 33 ) and
sodium chloride solution or a 1:1 mixture out or crude oil Canada (API 14 )
and sodium chloride
solution was mixed each with butyl diethylene glycol (BDG). Butyl diethylene
glycol (BDG)
works as cosolvent and was not taken into account for SP*. Surfactant mixture
consisting out
of three parts alkyl alkoxy sulfate and one part secondary alkyl sulphonate
(Hostapur SAS 60
ex Clariant) was added each. Each total surfactant concentration in weight
percent refers to
aqueous phase.
The results for surfactants based on linear and branched alcohols are shown in
tables 1 to 7.
Table 1 Surfactants based on linear C16C18-alcohol
Ex. Alkyl - AO - SO4Na : Surfactant BDG NaCI Topt SP*
IFT
C12H25Ph-S03Na = 3: 1 [ ./0] [ /0] ro) [ C] [mN/rn]
Cl CisCia -7 PO - SO4Na 2.5 2 5 48 13.3 0.0017
C2 CieCis - 7 PO - SO4Na 2.5 2 4 60 17.8 0.0009
C3 CisCis - 9 PO - SO4Na 2.5 2 5 52 15.5 0.0012
C4 CisCia - 9 PO - SO4Na 2.5 2 4 67 17.8 0.0009
5 Ci6C18- 2 "1,2-BuO" - 7 PO - 2.5 2 5 47 16 0.0012
SO4Na
6 CisCia- 2 "1,2-BuO" - 7 PO -2.5 2 4 65 16.5 0.0011
,SO4Na
C7 CisCia- 7 PO - 2 "1,2-BuO" - 2.5 2 4 46 11.8
0.0022
SO4Na
C8 C16C18- 7 PO - 2 "1,2-BuO" - 2.5 2 3 68 14.3
0.0015
SO4Na
C9 C16C18- 9 PO - SO4Na 1.25 2 5 52 14 0.0015
C10 Ci6C18- 9 PO - SO4Na 1.25 2 4 67 13 0.0018
11 Ci6C18- 2 "1,2-BuO" -7 PO - 1.25 2 3.35 72 15
0.0013
SO4Na
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C12 CisCia ¨ 2 "2,3-Bu0" ¨ 7 PO ¨ 1.25 2 4.5 74 8 0.0047
SO4Na
13 C16C18¨ 3 "1,2-BuO" ¨ 7 PO ¨ 1.25 2 3 67 23.5
0.0005
SO4Na
14 C16C18 ¨ 5 "1,2-Bu0" ¨7 PO ¨ 1.25 2 2 77 34.5
0.0003
SO4Na
15 C16C18¨ 5 "1,2-BuO" ¨ 7 PO ¨ 1.25 2 2.15 71 35.5
0.0002
SO4Na
16 C18C18 ¨ 5 "1,2-BuO" ¨7 PO ¨ 1.25 2 2.5 49 30.5
0.0003
SO4Na
As evident from examples Cl and C3 or 02 and C4 in table 1, there are few
differences in SP* between C16C18¨ 7 PO ¨ sulfate and CmCis ¨ 9 PO ¨ sulfate.
In this
respect, it should be noted that a comparison should be carried out at similar
1-00 in
order to rule out temperature effects. These may have a considerable influence
in the
case of surfactants with nonionic elements.
When BuO-containing C16C18-alkoxy sulfates are used, there are surprising
findings.
Examples 5 and 6 show that the incorporation of two 1,2-butylene oxide units
between
the C16C18-fatty alcohol and the seven propylene oxide units leads to a
surprisingly
stable SP* = 16, no matter whether at 47 C or at 62 C. A similar picture
emerges at
reduced total surfactant concentration. In example lithe SP* is 15 at 72 C.
Purely
PO-containing compounds with the same degree of alkoxylation show greater
variations (C3 and C4), or the SP* declines to a somewhat greater degree at a
reduced
total surfactant concentration (C9 and C10).
Arrangement of 1,2-butylene oxide between the propylene oxide block and the
sulfate
group as in comparative examples 07 and C8 is, in contrast, less favorable.
SP* is at a
somewhat lower level and varies more significantly on consideration of
different
temperatures.
The use of 2,3-butylene oxide is significantly poorer. As can be seen in C12,
SP* is
virtually halved at SP* = 8, and hence is poorer than alkyl propoxy sulfates
with the
same degree of alkoxylation (09). Surprisingly, not the mere number of carbon
atoms
but also the spatial arrangement thereof has a great influence on the ability
of the
surfactants to lower the interfacial tension. An unfavorable arrangement as in
the case
of 2,3-butylene oxide actually has a disruptive effect and gives poorer values
than in
the case of corresponding surfactants without alkylene oxide having 4 carbon
atoms.
US 3890239 or US 4448697 does not describe this.
Interestingly, there is an abrupt improvement as soon as the content of 1,2-
butylene
oxide units is three or greater in the linear C16C18-fatty alcohol. In example
13, the
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incorporation of three such units leads to a rise in the SP* to 23.5. This can
even be
enhanced further by going up to 5 units (examples 14-16). SP* is even above 30
here.
Table 2 Surfactants based on branched iCiralcohol
Ex. Alkyl - AO - SO4Na : Surfactant BDG NaCI Too SP* IFT
C12H25Ph-SO3Na = 3: 1 [Ok] [ C] ImNim]
Cl 1C17- 7 PO - SO4Na 1.25 2 4 77.5 10.5 0.0027
2 1C17- 7 "1,2-BuO" - SO4Na 1.25 2 1 82.5 32.5
0.0003
C3 iC17- 14 PO - SO4Na 1.25 2 4.4 77 6.5 0.0071
4 iC17 - 7 PO - 7 "1,2-Bu0"- 1.25 2 1.65 74.5 17
0.0010
SO4Na
5 iC17 - 7 "1,2-Bu0" - 7 PO - 1.25 2 2.5 67.5 31.5
0.0003
SO4Na
6 iC17 - 7 "1,2-Bu0" - 7 PO - 1.25 2 3 50 29.5
0.0003
SO4Na
A similar picture emerges in table 2. Here, alkyl alkoxy sulfates based on the
branched
iCiralcohol were used to demonstrate that there is an effect which is not
attributable to
linear alcohols alone.
Comparative example Cl and example 2 show very clearly that the use of 1,2-
butylene
oxide instead of propylene oxide is distinctly advantageous in surfactants
with the
same degree of alkoxylation. At a similar temperature, the SP* is three times
as high.
The arrangement of the 1,2-BuO directly on the alkyl moiety (as in examples 5
and 6)
also gives lower interfacial tensions than a different arrangement as, for
example, in
example 4.
Table 3
Surfactants based on branched C16 Guerbet alcohol compared to C16C18-
alcohol-based surfactants
Ex. Alkyl - AO - SO4Na : Surfactant BDG NaCI T01 [ C]
SP* IFT [mN/rn]
C12H25Ph-SO3Na .= 3: 1 rid I%
Cl C16C18- 9 PO - SO4Na 1.25 2 4 67 13 0.0018
2 CI6C18 - 2 "1,2-BuO" -7 PO - 1.25 2 3.35 72 15
0.0013
SO4Na
3 C16-Guerbet- 2 õ1,2-BuO" - 7 1.25 2 2.85 68 27.5
0.0004
P0- SO4Na
4 C16-Guerbet - 2 õ1,2-BuO" - 7 1.25 2 3 64 23.5
0.0005
PO - SO4Na
5 C16C16- 3 "1,2-BuO" - 7 P0- 1.25 2 3 67 23.5
0.0005
SO4Na
6 C16-Guerbet - 7 õ1,2-BuO" - 7 0.40 2 4. 5 73 31
0.0003
PO - 10 EO - SO4Na
C7 C16-Guerbet - 7 PO - SO4Na 1.25 2 5 70 6
0.0083
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C8 C16-Guerbet - 9 PO - SO4Na 1.25 2 4 71 9
0.0037
C9 C16-Guerbet - 6 PO - SO4Na 1.25 2 5 64 5
0.0120
C10 C16C18- 6 PO - SO4Na 1.25 2 5 64 10 0.0030
11 C16-Guerbet- 1 õ1,2-BuO" - 7 1.25 2 3.3 73 10.25
0.0029
PO - SO4Na
As can be seen in table 3, a similar picture applies hereto. If a surfactant
based on a
linear alcohol comprises more than two 1,2-BuO units, there is a distinct jump
in the
SP* and hence a lowering of the interfacial tension. Example 2 compared to
examples 3 and 4 shows the difference between the surfactant based on the
linear
C16C18-alcohol and the surfactant based on the branched C16 Guerbet alcohol.
In the
Guerbet-based surfactant, a significantly better SP* is already attained on
incorporation
of 2 1,2-butylene oxide units than when the surfactant is based on a linear
alcohol with
similar chain length. However, incorporation of a further amount of 1,2-
butylene oxide
in the case of the linear alcohol can, as can be seen in example 5, achieve an
approximately identical SP* level to that in example 4.
It can be seen in example 6 that the incorporation of 10 EO between sulfate
group and
PO block can virtually compensate for the additional hydrophobicity of the 7-
BuO block;
it is thus possible to make a comparison with comparative example Cl under
similar
conditions (similar salt content, similar temperature Too).
Without the incorporation of 1,2-butylene oxide, as can be see in comparative
examples C7 and C8, the surfactant is merely an average surfactant. Example 11
shows that the incorporation of 1 eq of 1,2-BuO only gives a certain
improvement in
SP*. Only incorporation of 2 eq of 1,2-BuO gives a significant improvement in
the case
of the C16 Guerbet-based surfactant (example 3).
Table 4 Tests with south German crude oil
Ex. Alkyl ¨ AO ¨ SO4Na : C12H25Ph- Surfactant BDG NaCI T.21
SP" IFT
SO3Na -=-= 3: 1 [0/.] IN IN rC1 [mN/m]
Cl Cl6C18¨ 9 PO ¨ SO4Na 0.8 2 5 34.5 9.7 0.0032
2 C16C18 ¨ 3 "1,2-BuO" ¨ 7 PO ¨ 0.8 2 3.5 31 15.9
0.0012
SO4Na
C3 C16-Guerbet ¨ 9 PO ¨ SO4Na 0.8 2 5.1 34 5.8
0.0089
4 C16-Guerbet - 2 õ1,2-BuO" - 7 PO - 0.8 2 3.5 34 15
0.0013
SO4Na
As can be seen in table 4, a virtually identical picture also emerges with
crude oil
compared to the tests with decane model oil. Comparative example Cl gives
significantly lower SP* values and hence higher interfacial tensions than the
BuO-
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containing surfactant in example 2 at comparable temperature. Comparative
example
C3 and example 4 show the advantage of the 1,2-butylene oxide in a similar
manner.
Table 5 Tests will decane at similar temperature and salinity
Ex. Alkyl ¨ AO ¨ SO4Na : Surfactant BDG NaCI Toõt SP* IFT
Hostapur SAS 60=3:1 [%] Wo) [ C] [mNim]
V1 C15C18¨ 7 PO ¨ 0.1 E0-SO4Na 0.4 2 4.7 59.9 18.3
0.0009
2 C16C18¨ 7 1 ,2-Bu0" ¨ 7 PO ¨ 10 0.4 2 4.7 64,8 37
0.0002
EO SaiNa
Aqueous surfactant solution mixed with BDG are clearly soluble under optimum
conditions (salinity und T0pt and give by addition of oil a 3-phase-system
(Winsor Typ
III). As shown in table 5 optimum conditions (salinity und Tc,pt) are very
close by. Right
fine tuning of alkoxylation degree as shown in example 2 lead to surfactant,
which has
a similar hydrophilic-hydrophobic-balance as the surfactant in example V1. SP*
in
example 2 is much higher. Consequently interfacial tension is much lower.
Table 6 Tests with crude oil from Germany (API 33 ) at similar
temperature and
salinity
Ex. Alkyl ¨ AO ¨ SO4Na Surfactant BD NaCI Topt SP* IFT
Hostapur SAS 60=3:1 [%] G [/o] [ C] [mN/m]
[0/o]
Vi C16C18¨ 7 PO ¨ 0.1 E0-SO4Na 0.4 2 3.5 73 24.5
0.0005
2 C16C18¨ 7 "1,2-BuO" ¨7 PO ¨ 10 0.4 2 3.5 78,5 37
0.0002
E0 - SatNa
Aqueous surfactant solution mixed with BDG are clearly soluble under optimum
conditions (salinity und T0pt and give by addition of oil a 3-phase-system
(Winsor Typ
III). As shown in table 6 optimum conditions (salinity und -100) are very
close by. Right
fine tuning of alkoxylation degree as shown in example 2 lead to surfactant,
which has
a similar hydrophilic-hydrophobic-balance as the surfactant in example V1. SP*
in
example 2 is again much higher. Consequently interfacial tension is much
lower.
30
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Table 7 Tests with crude oil from Canada (API 14) at similar
temperature and
salinity
Ex. Alkyl ¨ AO ¨ SO4Na : Surfactant BDG NaCI T0 SP*
IFT
Hostapur SAS 60=3:1 [%] [/o] [%] [*C1
[mN/m]
V1 C16C18¨ 7 PO ¨ 0.1 E0-SO4Na 0.4 2 7 55 12
0.0021
2 CI6C18¨ 7 "1,2-BuO" ¨ 7 PO ¨ 10 0.4 2 7 57
19,5 0.0008
E0 - SO4Na:
CI6C18 ¨ 7 "1,2-BuO" ¨ 7 PO ¨ 8
E0-SO4NA=2
5 Aqueous surfactant solution mixed with BOG are clearly soluble under
optimum
conditions (salinity und T0p1 and give by addition of oil a 3-phase-system
(Winsor Typ
III). As shown in table 7 optimum conditions (salinity und T00) are very close
by. Right
fine tuning of alkoxylation degree as shown in example 2 lead to surfactant,
which has
a similar hydrophilic-hydrophobic-balance as the surfactant in example V1. SP*
in
10 example 2 is again much higher. Consequently interfacial tension is much
lower.
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