Note: Descriptions are shown in the official language in which they were submitted.
1
Process for producing mineral oil using surfactants based on CisCia-containing
alkyl
propoxy surfactants
Description
The invention relates to a process for mineral oil production 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-(CH2C(CH3)HO)m(CH2CH20)n-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withdrawn from the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.
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 lam. As well as mineral oil, including fractions of
natural gas, a
deposit comprises water with a greater or lesser salt content.
In mineral oil production, a distinction is generally drawn between primary,
secondary and
tertiary production. In primary production, 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 production, secondary production is therefore used. In secondary
production,
in addition to the boreholes which serve for the production 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.
By means of primary and secondary production, generally only approx. 30 to 35%
of the
amount of mineral oil present in the deposit can be produced.
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It is known that the mineral oil yield can be enhanced further by measures for
tertiary
oil production. A review of tertiary oil production can be found, for example,
in "Journal
of Petroleum Science of Engineering 19 (1998)", pages 265 to 280. Tertiary oil
production 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 production also includes methods in which suitable
chemicals are
used as assistants for oil production. These can be used to influence the
situation
toward the end of the water flow and as a result also to produce 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 production, 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):
Pv
N= cos =
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 G 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
production
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
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
PF 0000070462 SE/PP CA 02790159 2012-08-16
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- a very low interfacial tension a 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 a more preferably to values
of
< 1 0-2 mNim (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:
Firstly, as the continuous oil bank advances through new porous rock, the oil
droplets
present there can coalesce with the bank.
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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 Winsor type III 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 production differ
significantly
from requirements on surfactants for other applications: suitable surfactants
for tertiary
oil production 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 5,849,960 discloses branched alcohols having 8 to 36 carbon atoms. The
degree of
branching is at least 0.7 and preferably 1.5 to 2.3, where less than 0.5%
quaternary
carbon atoms are present, and the branches comprise methyl and ethyl groups.
Also
described is the further processing of the alcohols to give corresponding
surfactants,
specifically alkoxylates, sulfates or alkoxy sulfates.
EP 003 183 B1 describes surfactants of the general formula R-0-polypropoxy-
poly-
ethoxy-X where X is a sulfate, sulfonate, phosphate or carboxylic acid group.
R in a
preferred embodiment is a branched alkyl radical having 10 to 16 carbon atoms,
for -
example an isotridecyl radical.
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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).
5
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 and
these
compounds become increasingly sparingly water-soluble.
It is therefore an object of the invention to provide a particularly efficient
and soluble
surfactant for use for surfactant flooding or preferably Winsor type 111
microemulsion
flooding, and an improved process for tertiary mineral oil production.
Accordingly, a process is provided for tertiary mineral oil production by
means of
Winsor type 111 microemulsion flooding, in which an aqueous surfactant
formulation
comprising at least one ionic surfactant is injected through at least one
injection
borehole into a mineral oil deposit for the purpose of lowering the
interfacial tension
between oil and water to <0.1 mN/m, preferably to <0.05 mN/m, more preferably
to
<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
R1-0-(CH2C(CH3)HO)m(CH2CH20),-XY" M+ where
is an unbranched, saturated or unsaturated, straight-chain aliphatic
hydrocarbon radical having 16 to 18 carbon atoms,
is from 0 to 99,
is from 0 to 99,
where the sum of n and m is in the range from 3 to 99,
Y" is selected from the group of sulfate groups, sulfonate groups,
carboxylate groups and phosphate groups,
X is an alkyl or alkylene group having 0 to 10 carbon atoms, and
1V1+ is a cation.
6
Additionally, there is provided a surfactant mixture for mineral oil
production, which comprises
at least one ionic surfactant of the general formula defined above.
More particularly, there is provided a process for mineral oil production by
means of Winsor
type III microemulsion flooding, in which an aqueous surfactant formulation
comprising water
and 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, 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
R1-0-(CH2C(CH3)HO)m(CH2CH20)n-XY- M+ where
R1 is an unbranched saturated or unsaturated straight-chain
aliphatic hydrocarbon
radical having 16 to 18 carbon atoms,
n is from 0 to 96,
m is from 3 to 20,
where the sum of n and m is in the range from 3 to 99,
Y is selected from the group consisting of sulfate groups,
sulfonate groups,
carboxylate groups and phosphate groups,
X is absent or an alkyl or alkylene group having 1 to 10 carbon
atoms, and
M+ is a cation.
There is also provided an aqueous surfactant formulation for mineral oil
production,
comprising water and at least one ionic surfactant of the general formula
R1-0-(CH2C(CH3)HO)m(CH2CH20)n-XY- M+ where
IR1 is an unbranched saturated or unsaturated straight-chain aliphatic
hydrocarbon
radical having 16 to 18 carbon atoms,
n is from 0 to 96,
m is from 3 to 20,
where the sum of n and m is in the range from 3 to 99,
Y- is selected from the group consisting of sulfate groups, sulfonate groups,
carboxylate groups and phosphate groups,
X is absent or an alkyl or alkylene group having 1 to 10 carbon
atoms, and
M+ is a cation.
There is further provided a surfactant of the general formula
R1-0-(CH2C(CH3)HO)m(CH2CH20)n-XY- M+ where
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6a
R1 is an unbranched saturated or unsaturated straight-chain aliphatic
hydrocarbon radical having 16 to 18 carbon atoms,
n is from 1 to 96,
m is from 3 to 20,
where the sum of n and m is in the range from 4 to 99,
Y. is selected from the group consisting of sulfate groups, sulfonate
groups, carboxylate groups and phosphate groups,
X is absent or an alkyl or alkylene group having 1 to 10 carbon atoms, and
NA+ is a cation,
wherein the alkylene oxides are > 80% arranged in block form and the propylene
oxide block
is joined directly to the R1-0.
According to an optional embodiment, in the general formula of the surfactant,
R1 is an
unbranched saturated straight-chain aliphatic hydrocarbon radical having 16 to
18 carbon
atoms.
According to another optional embodiment, in the general formula of the
surfactant, Y. is
selected from the group consisting of sulfate groups, sulfonate groups and
carboxylate
groups.
According to another optional embodiment, in the general formula of the
surfactant, the
surfactant comprises both alkylene oxides that are > 80% arranged in block
form, and the
propylene oxide block is joined directly to the R1-0.
According to another optional embodiment, in the general formula of the
surfactant, the sum
of n and m is in the range from 5 to 15.
According to another optional embodiment, in the general formula of the
surfactant, m is
greater than n.
With regard to the invention, the following should be stated specifically.
In the above-described process according to the invention for mineral oil
production by means of
Winsor type III 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.
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6b
In the process according to the invention for tertiary mineral oil production
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-(CH2C(CH3)HO)m(CH2CH20)n-XY- M. 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 unbranched aliphatic hydrocarbon radical
having 16 to
18 carbon atoms and is preferably saturated.
In the above general formula, n is from 0 to 99, preferably 0 to 19, more
preferably 0 to 10.
In the above general formula, m is from 0 to 99, preferably 3 to 20, more
preferably 5 to 11.
According to the invention, the sum of n + m is a number in the range from 3
to 99, preferably
in the range from 3 to 39, more preferably in the range from 5 to 15.
In a preferred embodiment of the invention, m is greater than n, which means
the propylene
oxide makes up more than 50% of the overall alkylene oxide (sum of n and m).
In the above-defined general formula n and m are each integers. It is clear to
the person
skilled in the art in the field of polyalkoxylates that this definition is the
definition
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of a single surfactant. In the case of presence of surfactant formulations
which
comprise a plurality of surfactants of the general formula, the numbers X and
m are
each mean values over all molecules of the surfactants, since the alkoxylation
of
alcohol with ethylene oxide and/or propylene oxide affords a certain
distribution of
chain lengths. This distribution can be described in a manner known in
principle by the
polydispersity D. D = Mw/M, 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.
According to the invention, the ethylene oxide and propylene oxide groups are
randomly distributed, alternatingly distributed, or are in the form of two or
more blocks
in any sequence. More preferably, in the presence of both alkylene oxides in
the
surfactant the alkylene oxides are > 80% arranged in block form, and the
propylene
oxide block is joined directly to the above-described R1-0.
In the above general formula, X is an alkylene group or alkenylene groups
having 0 to
10 and preferably 0 to 3 carbon atoms. In a preferred embodiment of the
invention, X is
a methylene, ethylene or propylene group.
In the above general formula, Y is a sulfonate, sulfate, carboxylate group or
phosphate
group. In a preferred embodiment of the invention, Y- is a sulfate group. The
ionic Y
group can be attached to the alcohol alkoxylate, for example, by means of
sulfation.
In the above formula M+ is a cation, preferably a cation selected from the
group of Na+,
K4, LI4, NH44, H4, Mg2+ and Ca2+.
The surfactants of the general formula can be prepared in a manner known in
principle
by alkoxylating corresponding alcohols R1-0H. The performance of 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.
The surfactants of the general formula can preferably be prepared by base-
catalyzed
alkoxylation. The alcohol R1-0H 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 inertization with inert gas (for example nitrogen) and
stepwise
=
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addition of the alkylene oxide(s) at temperatures of 60 to 180 C up to a
maximum
pressure of 10 bar. According to the invention, the propylene oxide is
preferably added
first, in order to obtain an alkyloxy propylene ether, which is then reacted
with the
ethylene oxide. At the end of the reaction, the catalyst can be neutralized by
adding
acid (for example acetic acid or phosphoric acid) and is 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 432 523 7 A1, or
it is
possible to use double metal cyanide catalysts (DMC catalysts). Suitable DMC
catalysts are disclosed, for example in DE 102 43 361 A1, 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.
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
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
such polymeric surfactants comprise amphiphilic block copolymers which
comprise at
least one hydrophilic block and at least one hydrophobic block. Examples
comprise
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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 2006/1 31 541
A1.
Process for mineral oil production
In the process according to the invention for mineral oil production, 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 mNim.
After the injection of the surfactant formulation, known as "surfactant
flooding", or
preferred 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.
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
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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
5 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 Winsor type III
microemulsion
flooding has already been described in detail at the outset.
10 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.
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 I: Synthesis of the surfactants used
General method 1: Alkoxylation by means of KOH catalysis
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
PF 0000070462 SE/PP CA 02790159 2012-08-16
= 11
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). This is followed by stirring at 125 to 135 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 1H NMR spectrum in CDCI3, gel
permeation
chromatography and OH number determination, and the yield is determined.
General method 2: 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. 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
C16C18 Commercially available fatty alcohol mixture consisting
of linear
C16H33-0H and Cighip-OH
C14 Commercially available linear alcohol C14H29-0H
C20 Commercially available linear alcohol C201-141-0H
The alcohols were each alkoxylated according to method 1, and the particular
degree
of alkoxylation is summarized in Tables 1 to 3.
Part II: Performance tests
The surfactants obtained were used to carry out the following tests in order
to assess
the suitability thereof for tertiary mineral oil production.
PF 0000070462 SE/PP CA 02790159 2012-08-16
12
Description of the test methods
a.) Solubility
An alkyl alkoxy sulfate is dissolved at room temperature in a saline injection
water or
production water from a deposit (total concentration 500 to 3000 ppm), and
NaOH
(1000 to 1.5000 ppm) and optionally a chelating agent, for example EDTA, are
added.
Optionally, butyl diethylene glycol (BDG) was added. Subsequently, the
solution is
brought to the deposit temperature. After 24 h, the formulation is assessed
visually and
used further only in the presence of a clear solution. The injection water of
the deposit
in question had a salinity of 11250 ppm TDS (total dissolved salt). The
deposit
temperature was 32 C.
b.) Interfacial tension
In addition, interfacial tensions were measured directly by the spinning drop
method on
a dead crude oil (API approx. 14) and the saline original injection water at
deposit
temperature 32 C. For this purpose, the surfactant solution produced in a) was
used.
At deposit temperature, an oil droplet was introduced into this clear
solution, and the
interfacial tension was read off after 2 h.
c.) Determination of SP*
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
dissolved per ml of surfactant used in a microemulsion (Winsor type III). The
interfacial
tension a (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)).
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
13
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
Surfactants based on linear CisCu-fatty alcohol were used. For comparison,
surfactants
based on the linear alcohols C20 and C14 were selected. 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, interfacial tensions were measured directly by the spinning drop
method on a
dead crude oil (API approx. 14) and a saline original injection water with
11250 ppm TDS
(total dissolved salt) at deposit temperature 32 C. For this purpose, the
original injection water
was admixed with 1000 ppm of surfactant, 500 ppm of BDG, 300 ppm of chelating
agent and
3500 ppm of NaOH. At 32 C, an oil droplet was introduced into this clear
solution and the
interfacial tension was read off after 2 h. The results are shown in Tables 1
to 3.
Table 1
Ex Alkyl ¨ AO ¨ SO4Na: Surfactant BDG NaCI To
SP*
pt I FT
.
C12H25Ph-SO3Na = 3:1 [ok] [A] [/0] [ C] [mN/m]
C1 C20 ¨ 7 PO ¨ SO4Na 2.5 2 4 58 14.8 0.0014
C2 C14 ¨ 7 PO ¨ SatNa 2.5 2 7 58 7.3 0.0056
3 CisCts ¨ 7 PO ¨ SO4Na 2.5 2 4 60 17.8 0.0009
4 Ci6C18 ¨ 9 PO ¨ SaiNa 2.5 2 4 67 17.8 0.0009
CA 2790159 2017-10-06
PF 0000070462 SE/PP CA 02790159 2012-08-16
14
As can be seen in Table 1, the C16C18-based compounds astonishingly gave the
highest SP* values and hence the lowest interfacial tensions. In order to rule
out any
influence of temperature, comparison was first made at the same optimal
temperature
(formation of a balanced Winsor Type III microemulsion). As expected,
Comparative
" Example C2 gives a higher interfacial tension than Example 3. This is in
agreement
with the literature. An extension of the linear alkyl radical beyond Cig
astonishingly
already shows the differences thereof on the simple model oil decane
(Comparative
Example C1 compared to Examples 3 and 4). In the case of C1, the interfacial
tension
is not lowered any further, but increased. It can normally be inferred from
the literature
that an extension of the alkyl radical leads to a lower interfacial tension.
However, this
is not the case.
. =
PF 0000070462 SE/PP CA 02790159 2012-08-16
Table 2
Na0 Salinit
Alkyl ¨ AO ¨ SO4Na BDG Chelate
Ex. H y
Solubility
[1000 ppm] IPPrnl[ C]
[ppm][PPrn]
C16C19 ¨ 7 P0¨
1 500 3500 300 11250 32 clear
SO4Na
C16C18 ¨ 7 P0¨
2 500 6500 300 11250 32 clear
SO4Na
turbid
C3 C20 ¨ 7 PO ¨ SO4Na 500 3500 300 11250 32
homogeneous
C4 C14 ¨ 7 PO ¨ SO4Na 500 3500 300 11250 32
clear
C16C18 ¨ 6 PO ¨
clear
5 500 3500 300 11250 32
SO4Na
C6 C20-6 PO ¨ SO4Na 500 3500 300 11250 32
clear
C7 C20¨ 9 PO ¨ SO4Na 500 5000 300 11250 32
clear
In the saline injection water, almost all surfactant formulations prepared
have dissolved
5 clearly
at room temperature and deposit temperature 32 C (Table 2). An exception is
C3 containing C20 ¨ 7 PO ¨ sulfate. A turbid but homogeneous solution was
present
here. This can lead over the course of time, in a porous matrix, to deposits
and
blockages of the fine channels. The lack of branching in the alkyl radical in
the other
examples is not found to be a disadvantage. The literature generally refers to
the
10
advantage of a branch. As a result, for example, the solubility improves, or
the Kraft
point of a surfactant is lowered. Surfactants based on linear alcohols do not
have any
disadvantages in terms of solubility as a result of the combination with
propylene oxide.
Table 3
Ex. Alkyl ¨ AO ¨ SO4Na BDG NaOH Chelate Salinity T
IFT
[1000 ppm] [ppm] [ppm] [ppm]
[ppm] [ C] [mNim]
1 c16c18- 7 PO ¨ SO4Na 500 3500 300 11250 32
0.0032
2 C16C18 ¨ 7 PO ¨ SO4Na 500 6500
300 11250 32 0.0028
C3 C20 ¨ 7 PO ¨ SO4Na 500 3500 300 11250 32 0.0604
C4 C14 ¨ 7 PO ¨ SO4Na 500 3500 300 11250 32 0.0373
5 C16C18 ¨ 6 PO ¨ SO4Na 500 3500 300
11250 32 0.0053
C6 C20 ¨ 6 PO ¨ SO4Na 500 3500 300 11250 32 0.0340
C7 C20¨ 9 PO ¨ SO4Na 500 5000 300 11250 32
0.0611
PF 0000070462 SE/PP CA 02790159 2012-08-16
= 16
As can be seen in Table 3, the surfactants based on linear alcohols give
different
interfacial tensions with respect to the crude oil. Even in the case of
variation in the
amount of NaOH (and hence a change in the salinity and an altered mobilization
of
naphthenic acids as natural surfactants), Example 1 and Example 2 give
excellent
interfacial tensions of about 3 x 10-3 mN/m. Even a variation in the degree of
propoxylation (Example 5) shows only a small change in the good interfacial
tension
values. It rises to 5 x 10-3 mN/m. If this is compared with a surfactant based
on the
linear C20-alcohol (C6 and C7), it is found that the interfacial tensions are
much higher
(at 3-6 x 10-2 mN/n, almost one order of magnitude higher). A surfactant with
a shorter
alkyl moiety (C14), as can seen from C4, also does not give better interfacial
tension
values.
