WO2012126976A1

WO2012126976A1 - Method for recovering crude oil using surfactants belonging to the class of alkyl polyglucosides

Info

Publication number: WO2012126976A1
Application number: PCT/EP2012/055061
Authority: WO
Inventors: Christian Bittner; Günter OETTER; Jack Tinsley; Christian Spindler; Gabriela ALVAREZ JÜRGENSON; Sophie Maitro-Vogel; Monika SANTA; Jianhua Mao
Original assignee: Basf Se; Cognis Ip Management Gmbh
Priority date: 2011-03-24
Filing date: 2012-03-22
Publication date: 2012-09-27
Also published as: US20120241151A1

Abstract

The invention relates to a method for recovering crude oil. An aqueous surfactant formulation comprising at least one alkyl polyglucoside is injected into a crude oil reservoir through at least one injection bore, and crude oil is removed from the reservoir through at least one production bore, said formulation not containing alcohols as cosolvents.

Description

Process for the extraction of crude oil using surfactants from the class of alkylpolyglucosides

description

The present invention relates to petroleum production processes in which an aqueous surfactant formulation comprising at least one alkyl polyglucoside is injected through at least one injection well into a petroleum deposit and crude oil is withdrawn through the deposit through at least one production well, the formulation comprising no alcohols as co-solvent.

In natural oil deposits, petroleum is present in the cavities of porous reservoirs, which are closed to the earth's surface by impermeable cover layers. The cavities may be very fine cavities, capillaries, pores or the like. Fine pore necks, for example, have a diameter of only about 1 μιη. In addition to crude oil, including natural gas, a deposit contains more or less saline water. Oil production generally distinguishes between primary, secondary and tertiary production. In primary production, after drilling the deposit, petroleum automatically streams through the borehole due to the inherent pressure of the deposit. After the primary funding, therefore, the secondary funding is used. In secondary production, additional wells will be drilled into the oil-bearing formation in addition to the wells that serve to extract the oil, known as production wells. Through these so-called injection wells water is injected into the reservoir to maintain or increase the pressure. By injecting the water, the oil is slowly forced through the cavities into the formation, starting from the injection well, toward the production well. But this works only as long as the cavities are completely filled with oil and the viscous oil is pushed through the water in front of him. As soon as the low-viscosity water breaks through cavities, it flows from this point on the path of least resistance, ie through the channel formed, and no longer pushes the oil before her.

By means of primary and secondary production, as a rule only about 30-35% of the quantity of crude oil in the deposit can be extracted. It is known to further increase the oil yield by means of tertiary Olförderung. An overview of tertiary oil production can be found, for example, in the "Journal of Petroleum Science of Engineering 19 (1998)", pages 265 to 280. Tertiary oil extraction involves heat processes in which hot water or superheated steam is injected into the deposit, thereby increasing the viscosity of the oil The flooding medium can also be gases such as CO2 or nitrogen.

Tertiary oil production further includes processes in which suitable chemicals are used as auxiliaries for oil production. With these, the situation can be influenced towards the end of the flood and thus also promote oil that was previously held in the rock formation.

Viscous and capillary forces act on the oil, which is trapped in the pores of the reservoir rock towards the end of the secondary production, and the relationship of these two forces to one another determines the microscopic oil removal. By means of a dimensionless parameter, the so-called capillary number, the influence of these forces is described. It is the ratio of the viscosity forces (velocity x viscosity of the pressing phase) to the capillary forces (interfacial tension between oil and water x wetting of the rock):

σ coso

Where μ is the viscosity of the oil mobilizing fluid, v the Darcy velocity (flow per unit area), σ the interfacial tension between petroleum mobilizing liquid and petroleum and Θ the contact angle between petroleum and rock (C. Melrose, CF Brandner, J Canadian Petr. Techn. 58, Oct.-Dec., 1974). The higher the capillary number, the greater the mobilization of the oil and thus also the degree of de-oiling. It is known that the capillary is located near the end of secondary oil recovery in the range of about 10 ⁶ and that it is necessary to increase the capillary number of about 10 ³ to 10 ^"2 to mobilize additional mineral oil.

With the help of surfactants, the oil-water interface can be covered and the interfacial tension σ can be lowered, preferably to values of <10 ² mN / m (ultralow interfacial ten sion).

In this way, the oil droplets can change their shape (interfacial tension between oil and water is lowered so far that no longer the State of the smallest interface is sought and not the spherical shape is preferred) and squeeze through the flood water through the capillary.

Usually, the surfactants are optionally injected together with cosolvents and / or basic salts (optionally in the presence of chelating agents). Subsequently, a solution of thickening polymer is injected for mobility control. Another variant is the injection of a mixture of thickening polymer and surfactants, cosolvents and / or basic salts (optionally with chelating agent) and subsequently a solution of thickening polymer for mobility control. These solutions should usually be clear to avoid blockage of the reservoir.

The requirements for surfactants for tertiary mineral oil production differ significantly from requirements for surfactants for other applications: Suitable surfactants for tertiary oil production are the interfacial tension between water and oil (usually approx. 20 mN / m) to particularly low values of less than 10 ² Reduce mN / m to allow sufficient mobilization of the petroleum. This must be done at the usual storage temperatures of about 15 ° C to 130 ° C and in the presence of highly saline water, especially in the presence of high levels of calcium and / or magnesium ions; The surfactants must therefore be soluble in highly saline reservoir water.

In order to meet these requirements, mixtures of surfactants have frequently been proposed, in particular mixtures of anionic and nonionic surfactants. Nonionic surfactants of, for example, the alkyl polyglucoside type have been described, but the required low interfacial tensions have been achieved only by the addition of significant amounts of cosolvents such as an alcohol.

US 4,985,154 describes a mixture of alkyl polyglucosides with cosolvents for use in oil extraction. As cosolvents, various alcohols are mentioned (column 6, lines 4 ff.), For example monoalcohols having 3 to 8 C atoms, polyalcohols having 3 to 10 C atoms, alkyl ethers of polyhydric alcohols having 2 to 8 C atoms in the alkyl chain or alkyl polyglucosides having alkyl chains of 3 to 6 carbon atoms in length. In column 5, line 10 it is pointed out that one always requires a cosolvent when using alkyl polyglucosides. The ratio of surfactant / cosolvent is preferably 1: 5 to 5: 1. The examples disclose aqueous surfactant formulations in which the amount of surfactant and cosolvent is 4% by weight.

US 2006/046948 claims the mixture of alkyl polyglucosides with aromatic alcohols for tertiary mineral oil production. The mixing ratio of the aroma Tables of alcohol with the alkyl polyglucosides can be 1000: 1 to 1: 1000. In addition, Table 9 (page 9) discloses combinations of the aliphatic alcohols 1-propanol, 1-butanol, 1-hexanol or 1-octanol with a C12-based alkyl polyglucoside in a weight ratio of 1: 3, which provide the required interfacial tensions with octane as model oil reached. A low interfacial tension without the addition of alcohol could not be found.

S. Iglauer, Y. Wu, P. Shuler, Y. Tang, and W.A. Goddard I, I, Colloids and Surfaces A: Physichochem. Closely. Aspects 339 (2009) 48-59 disclose formulations of alkyl polyglucosides and various alcohol colloids for improved petroleum production. For example, 1-propanol, 1-butanol, 1 -H-exanol, 1-octanol, 1-dodecanol, 4-methyl-2-hexanol, cyclohexanol or phenol or naphthol have been used. For the experiments, in each case 2% by weight of a mixture of surfactant and cosolvent were used, the minimum amount used when using 1-dodecanol was 10% alcohol with respect to the mixture of alcohol and surfactant, with the other alcohols at least 20% by weight. The use of alkyl polyglucosides in an amount of 2% by weight in a model system of saline water (2% NaCl) and n-octanol but without the addition of alcohols as cosolvent at room temperature resulted in only oil-water interface tensions of 0.735 mN / m ( for an alkypolyglucoside with an average of 12.5 carbon atoms), 1, 08 mN / m (with an average of 10, 1 C atoms) and 2.4 mN / m (with an average of 9.1 C atoms).

WO 2009/124922 discloses alkylpolyglucosides based on branched C ₇ -alcohols and their use for tertiary mineral oil extraction.

The use parameters, such as, for example, type, concentration and the mixing ratio of the surfactants used, are therefore adapted by the person skilled in the art to the prevailing conditions in a given oil formation (for example temperature and salinity).

As described above, the oil production is proportional to the capillary number. This is the higher the lower the interfacial tension between oil and water. The addition of alcohols as cosolvents to surfactants can lower the interfacial tension if the alcohol has a sufficient number of carbon atoms. Besides the increased costs due to the addition of further chemicals, there is the disadvantage that hydrophobic nonionic compounds such as alcohols dissolve well in the oil phase. Upon contact of the surfactant formulation with the oil, the alcohol is virtually weextracted from the interface. This changes the composition of the compounds at the oil-water interface and the interfacial tension increases again. Only with the use of high amounts of surfactant and alcohol would the "extraction" make little sense.

The object of the invention is therefore to provide a particularly efficient surfactant or an efficient surfactant mixture for use for surfactant flooding, as well as an improved process for tertiary mineral oil production.

Surprisingly, it has been found that the addition of alcohols as cosolvent is not necessary in order to achieve low interfacial tensions with crude oils when using surfactants of the general formula (I).

Accordingly, a petroleum production process has been discovered in which an aqueous surfactant formulation is injected through at least one injection well into a petroleum deposit and crude oil is withdrawn from the deposit through at least one production well, the interfacial tension between oil and water in the reservoir being under the action of the surfactant formulation Values <0.1 mN / m is lowered, and wherein the aqueous surfactant formulation at least

50% by weight of water,

• optionally water-miscible organic cosolvents other than water, as well

• at least one nonionic surfactant of the general formula R ¹ 0- (A) _m -H (I), wherein the surfactant may comprise proportions of monoalcohol R ¹ OH (II), wherein

R ¹ in the formulas (I) and (II) is identical and for a linear or branched, saturated or unsaturated aliphatic or aromatic-aliphatic hydrocarbon radical having 8 to 24 carbon atoms,

for a hexose or pentose, and

is a number from 1 to 10, wherein the amounts are in each case based on the total amount of all components of the formulation, and wherein as cosolvent the following OH-containing compounds are excluded: o of alcohols of the formula R ¹ OH different monoalcohols R ² OH (III) wherein R ^{2 is} a straight-chain, branched or cyclic aliphatic and / or aromatic hydrocarbon radical having 3 to 24 carbon atoms, o alkyl ethers of the formula R ² - (O-CH ₂ -CH ₂ ) n H (IV), where R ^{2 has} the abovementioned meaning and n is a number from 1 to 3, o dialcohols of the general formula HO-R ³ - OH (V), where R ^{3 is} a divalent, straight-chain or branched hydrocarbon radical having 2 to 10 carbon atoms,

o Compounds of the general formula R ⁴ 0- (A) _m -H (VI), wherein R ^{4 is} a hydrocarbon radical having 3 to 6 carbon atoms, and wherein the at least one surfactant R ¹ 0- (A) _m -H (I ) comprises not more than 3% by weight, based on the amount of the surfactant, of alcohols R ¹ OH (II). n is a preferred embodiment

R ^{1 is} a linear or branched, saturated or unsaturated aliphatic hydrocarbon radical having 8 or 18 carbon atoms, A is a hexose or pentose,

m is a number from 1 to 3. n a particularly preferred embodiment

R ^{1 is} a linear saturated or unsaturated aliphatic hydrocarbon radical having 8 or 18 carbon atoms,

A for glucose,

m for a number from 1 to 2.

More specifically, the following is to be accomplished for the invention:

The petroleum production process of the present invention, as described above, employs an aqueous surfactant formulation comprising at least one surfactant. Surfactants used

According to the invention, the aqueous formulation comprises at least one surfactant of the general formula R ¹ 0- (A) _m -H (I).

Of course, it is also possible to use two or more surfactants of the formula (I). The radical R ¹ from the general formula (I) is a linear or branched, saturated or unsaturated aliphatic or aromatic-aliphatic hydrocarbon radical having 8 to 24 carbon atoms, preferably 8 to 18 carbon atoms. Particularly preferred are linear saturated or unsaturated aliphatic hydrocarbon radicals having 8 to 18 carbon atoms. Examples of these are the radicals of fatty alcohols and / or mixtures thereof.

In the above formula (I), A has the meaning of the residue of a hexose or pentose residue. Examples of hexoses are allose, altrose, glucose, mannose, gulose, idose, galactose or talose. Examples of pentoses are ribose, arabinose, xylose or lyxose. The selection of the sugars is made by the skilled person depending on the alcohol used and the desired target compounds and property profile. Preferably, A is the residue of glucose and / or xylose residues, and more preferably A is a glucose residue.

In the case of hexoses, the general formula of the surfactants R ^{1 is} 0- (C 6 HioOs) m H (II). One of the OH groups of a hexose is esterified with an alcohol R ¹ OH and the m sugar units are linked together via glycosidic bonds in a manner known in principle.

In the general formula defined above, m may stand for an integer. However, it will be apparent to those skilled in the art of alkyl polyglucosides that this definition is the definition of a single surfactant. In the case of the presence of surfactant mixtures or surfactant formulations which comprise a plurality of surfactants of the general formula, the number m is averages over all molecules of the surfactants, since in the reaction of alcohol with hexoses or pentoses, a certain distribution of Chain lengths is obtained. This distribution can be described in a manner known in principle by the so-called polydispersity D. D = M _w / M _n is the quotient of the weight average molecular weight and the number average molar mass. The polydispersity can be determined by means of the methods known to the person skilled in the art, for example by means of gel permeation chromatography.

In the above general formula, m is a number from 1 to 10, preferably 1 to 3, particularly preferably 1 to 2.

The surfactants according to the general formula (I) can be prepared in a manner known in principle by acid-catalyzed reaction of alcohols R ¹ OH (II) with sugars with removal of the water of reaction. Exemplary descriptions can be found inter alia in US 3,547,828 or US 5,898,070 again. As by-product, the surfactants of the general formula (I) may also contain radicals of the alcohols R ¹ OH, where the radicals R ¹ in the formulas (I) and (II) are identical. Such levels of alcohol can be obtained by incomplete reaction in the course of said synthesis and need not be removed.

According to the invention, the at least one surfactant R ¹ 0- (A) _m -H (I) but not more than 3 wt.%, Based on the amount of the surfactant, of the alcohol R ¹ OH (II), preferably not more than 1, 5% by weight.

Other surfactants

In addition to the surfactants of the general formula (I), the formulation may additionally optionally comprise further surfactants. Examples of such surfactants include anionic surfactants of the type alkylarylsulfonate or olefinsulfonate (alpha-olefinsulfonate or internal olefinsulfonate), alkylalkoxysulfates, alkylalkoxysulfonates, alkylalkoxycarboxylates and / or nonionic surfactants of the alkylethoxylate type. Betainic surfactants may also be used. solvent

According to the invention, the surfactant formulation used comprises as solvent at least 50% by weight of water, preferably at least 80% by weight, more preferably at least 90% by weight of water and most preferably at least 95% by weight, based on the amount of all components of the formulation.

Optionally, it may additionally comprise water-miscible cosolvents, the alcohols R ¹ OH mentioned above not being counted among the cosolvents.

However, the following, OH-containing compounds are according to the invention excluded as cosolvents, namely o monoalcohols R ² OH (III) which are NEN of alcohols of formula R various ¹ OH wherein R ² is a straight-chain, branched or cyclic aliphatic and or aromatic hydrocarbon radical having 3 to 24 carbon atoms. o Alkyl ethers of the formula R ² - (O-CH ₂ -CH ₂ ) n H (IV), wherein R ^{2 has} the meaning already mentioned and n is a number from 1 to 3. o Dialcohols of the general formula HO-R ³ -OH (V), wherein R ^{3 is} a divalent, straight-chain or branched hydrocarbon radical having 2 to 10 carbon atoms.

o Compounds of the general formula R ⁴ 0- (A) _m -H (VI), wherein R ^{4 is} a hydrocarbon radical having 3 to 6 carbon atoms, ie, they are alkyl polyglucosides, but the hydrocarbon radical is shorter than in the present invention used surfactants of the formula (I).

Most preferably, the formulation does not include cosolvents besides water.

Other components

In addition to the surfactants, solvents, optional co-solvents and cosurfactants, the formulations described may also contain other components or additives, for example salts or complexing agents such as EDTA. In a particularly preferred embodiment, the formulation additionally comprises basic alkali salts (so-called "alkali surfactant flooding") .These salts can be selected from the group of alkyl metal hydroxides, alkali metal silicates or alkali metal carbonates, preferably from alkyl metal hydroxides and alkali metal carbonates The addition of basic salts advantageously converts acidic compounds in the petroleum oils, especially naphthenic acids occurring in crude oil, into the corresponding salts, and this produces a natural surfactant action The amount of basic salts may typically be from 0.1% to 5% by weight relative to the total amount of all components of the aqueous formulation Examples of preferred basic salts include sodium carbonate or sodium hydroxide. A formulation comprising basic salts may furthermore advantageously contain complexing agents such as, for example, EDTA.

amounts

The total concentration of all surfactants together is generally 0.01 to 5 wt .-% with respect to the total amount of the aqueous surfactant formulation, preferably 0.05 to 2.5 wt .-% and particularly preferably 0.1 to 2 wt.%. The amount of the surfactants of the surfactants of the general formula R ¹ O- (A) _m -H (I) used according to the invention is generally at least 0.01% by weight, preferably at least 0.05% by weight and more preferably at least 0.1 Weight%.

In general, the proportion of the surfactants of the general formula (I) is at least 50% by weight, preferably at least 80% by weight, particularly preferably at least 90% by weight and very particularly preferably 100% by weight of all surfactants used, ie. only surfactants of the general formula (I) are used.

Process for the extraction of oil

The deposits in which the method is used, as a rule, have a temperature of at least 10 ° C, for example 10 to 150 ° C, in particular a temperature of at least 15 ° C to 120 ° C. The method is particularly suitable for deposits with elevated reservoir temperature, especially deposits with 40 ° C to 120 ° C, preferably 45 ° C to 1 10 ° C and more preferably 50 ° C to 100 ° C.

The deposit comprises, in a known manner, oil as well as reservoir water, which as a rule is more or less salty.

The oil may be light, medium or heavy oils, for example those with an API grade of 10 ° to 45 ° API (as defined by the American Petroleum Institute).

It may preferably be deposits with salt contents of the reservoir water of more than 30,000 ppm. The salts may in particular be alkali metal salts and alkaline earth metal salts. Examples of typical cations include Na ⁺ , K ⁺ , Mg ²⁺ or Ca ²⁺ and examples of typical anions include chloride, bromide, bicarbonate, sulfate or borate.

For deposits with oil of an API grade of 10 ° API to less than 30 ° API, it is possible with particular advantage to use formulations which comprise the abovementioned basic salts, in particular alkali metal hydroxides or carbonates and very particularly sodium hydroxide or sodium carbonate.

For deposits with an API grade of 30 ° to 45 ° API, reservoir temperatures> 40 ° C and more than 30,000 ppm salts, formulations containing no basic salts can also be used well. In the method according to the invention for oil production, the described aqueous surfactant formulation is injected through at least one injection well into the oil reservoir and the deposit is withdrawn through at least one production well crude oil. Of course, the term "crude oil" in this context does not mean phase-pure oil, but rather the customary crude-oil-water emulsions. [. In] As a rule, a deposit is provided with several injection wells and with several production wells.

The main effect of the surfactant of the formula (I) and optionally related cosurfactants lies in the reduction of the interfacial tension between water and oil. When carrying out the process according to the invention for tertiary mineral oil extraction, the surface tension between oil and water is brought to values of <0.1 mN / m, preferably to <0.05 mN / m, particularly preferably to <0.01 mN, by using the described surfactant mixture / m lowered. Thus, the interfacial tension between oil and water on values in the range of 0.1 mN / m to 0.0001 mN / m, preferably on values in the range of 0.05 mN / m to 0.0001 mN / m, particularly preferably values are lowered in the range from 0.01 mN / m to 0.0001 mN / m.

The amount of formulation to be injected depends on the pore volume in the area of petroleum formation covered by the flooding process, i. the area between the injection and production wells. The pore volume can be determined by known methods. As a rule, it is recommended to inject a quantity of 0.05 to 3 times the pore volume as surfactant. Following the pressing in of the surfactant formulation, the so-called "surfactant flooding", water can be injected into the formation ("water flooding") to maintain the pressure or, preferably, a higher-viscous aqueous solution of a polymer having a pronounced thickening effect ("polymer flooding"). However, techniques are also known according to which the surfactants are first allowed to act on the formation Another known technique is the injection of a solution of surfactants and thickening polymers followed by a solution of thickening polymer technical implementation of "surfactant flow", "water flooding" and "polymer flooding" known and he applies depending on the nature of the deposit a corresponding technique.

The person skilled in the art makes an appropriate choice with regard to the concentration of the surfactants, depending on the desired properties, in particular depending on the conditions in the petroleum formation. In particular, the amount is measured by the fact that the required reduction of the interfacial tension to values below 0.1 mN / m is achieved. For the expert it is clear that the concentration of the surfactants after injection into the formation because the formulation can mix with formation water or absorb surfactants also on solid surfaces of the formation. It is the great advantage of the mixture used according to the invention that the surfactants lead to a particularly good lowering of the interfacial tension.

It is of course possible to first produce a concentrate which is diluted on site to the desired concentration for injection into the formation. As a rule, the total concentration of the surfactants in such a concentrate is from 30 to 50% by weight. Depending on the surfactant, it is also possible to supply concentrates of up to 98%; however, storage at 40 - 50 ° C may be necessary.

The following examples are intended to explain the invention in more detail: Synthesis of the surfactants used according to the invention

Compounds of the general formula (I) were prepared as described in US 5,898,070, Example 1. The sugar used for the synthesis was D-glucose monohydrate and the following alcohols.

In the surfactants of the formula R ¹ 0- (A) _m -H thus obtained, A is glucose residues and m is 1, 4 to 1, 9. The residual alcohol content R ¹ OH is in each case less than 2% by weight with respect to the surfactants R ¹ 0- (A) _m -H.

For the comparative experiments, the commercially available surfactants octyl sulfate sodium salt, dodecylbenzenesulfonate sodium salt, lauryl alcohol, alkoxylated with 10 units of ethylene oxide, Laurylaminoxid and cocoamidopropyl betaine were used.

Application testing

With the surfactants obtained, interfacial tensions were measured by spinning drop technology to evaluate the suitability of surfactants for tertiary oil recovery. Subsequently, pilot tests were carried out on a smaller scale. test results

Interfacial tensions were measured by spinning drop tensiometers. For this purpose, a crude oil and 1 percent by weight of surfactant in seawater (with a salinity> 30,000 ppm) at 80 ° C was used. The interfacial tension was determined after 1 minute rotation time. The results are shown in Table 1. Examples C1 - C5 are for comparison.

Example surfactant [1% in seawater] interfacial tension

[dyn * cm ¹ ]

1 octyl polyglucoside 0.005

2 dodecylpolyglucoside 0.005

C1 octylsulfate sodium salt 1 .0

C2 dodecylbenzenesulfonate sodium salt 0.5

C3 lauryl alcohol + 10 EO 1 .2

C4 Laurylamine oxide 1 .1

C5 cocoamidopropylbetaine 1 .3

TABLE 1 Interfacial Tensions Water-oil when using surfactants according to the invention and the comparative surfactants C1 to C5 in seawater at 80 ° C.

As can be seen in Table 1, the surfactant solutions used according to the invention achieve very low interfacial tensions under the test conditions, although no cosolvent was added (Examples 1 and 2). Remarkably, the nonionic surfactants of the general formula (I) under these conditions achieve significantly lower interfacial tensions than other commercially available surfactants (Examples C1-C5).

In order to test the effect in the oil field, the above surfactants were in turn injected as 1% solutions in water through one or more injectors by conventional methods in a formation and taken crude oil through the production well. After the tidal flood, a buffer and water were injected. The amount of oil delivered to the producer depends on the surfactant used and the injected pore volume of surfactant solution. The results are shown in Table 2. Examples C6 to C10 are for comparison. The table shows the fraction of petroleum extracted after injection of aqueous surfactant formulation into the formation, after injection of an amount corresponding to the pore volume in the flooded region of the formation, and after injection of 1.5 times and 2 -fold amount. The term pore volume (PV) is described in more detail in US Pat. No. 3,927,716. Example surfactant [1%] Funded Funded Funded

Oil oil oil at 1 .0 PV at 1 .5 PV at 2.0 PV injection injection injection

3 octyl polyglucoside 41% 51% 54%

4 dodecyl polyglucoside 42% 50% 50%

C6 octylsulfate sodium salt 32% 33% 35%

C7 Dodecylbenzenesulfonate 36% 38% 40%

sodium salt

C8 lauryl alcohol + 10 EO 29% 31% 33%

C9 laurylamine oxide 18% 19% 20%

C10 cocoamidopropylbetaine 20% 21% 21%

Table 2: Field Test Results As can be seen in Table 2, the results from the interfacial tension measurements are confirmed. Even without the addition of colourants, alkyl polyglucosides provide significant amounts of oil, which are higher than with other surfactants.

Claims

15 claims

A process for producing crude oil which comprises injecting an aqueous surfactant formulation through at least one injection well into a crude oil reservoir and extracting crude oil from the reservoir through at least one production well, the interfacial tension between oil and water in the reservoir being <0.1 mN under the action of the surfactant formulation / m is lowered, and wherein the aqueous surfactant formulation at least

50% by weight of water,

• optionally water-miscible organic cosolvents other than water, as well

R ¹ in the formulas (I) and (II) is identical and represents a linear or branched, saturated or unsaturated aliphatic or aromatic-aliphatic hydrocarbon radical having 8 to 24 carbon atoms,

A for a hexose or pentose, and

m is a number from 1 to 10, wherein the quantities are in each case based on the total amount of all components of the formulation, characterized in that the cosolvents excluded are the following OH-containing compounds:

o monoalcohols R ² OH (III) other than alcohols of the formula R ¹ OH, where R ^{2 is} a straight-chain, branched or cyclic aliphatic and / or aromatic hydrocarbon radical having 3 to 24 carbon atoms,

o alkyl ethers of the formula R ² - (O-CH ₂ -CH ₂ ) _n -H (IV), wherein R ^{2 has} the meaning already mentioned and n is a number from 1 to 3, o dialcohols of the general formula HO-R ³ -OH (V), where R ^{3 is} a divalent, straight-chain or branched hydrocarbon radical having 2 to 10 carbon atoms,

o Compounds of the general formula R ⁴ 0- (A) _m -H (VI), wherein R ^{4 is} a hydrocarbon radical having 3 to 6 carbon atoms, and wherein the at least one surfactant R ¹ 0- (A) _m -H (I ) comprises not more than 3% by weight, based on the amount of the surfactant, of alcohols R ¹ OH (II). 16

2. The method according to claim 1, characterized in that no organic cosolvents are present in the formulation.

3. The method according to claim 1 or 2, characterized in that

R ^{1 is} a linear or branched, saturated or unsaturated aliphatic hydrocarbon radical having 8 to 18 carbon atoms, and m is a number from 1 to 3.

4. The method according to claim 1 or 2, characterized in that

R ^{1 represents} a linear saturated or unsaturated aliphatic hydrocarbon radical having 8 to 18 carbon atoms,

A for glucose, and

m is a number from 1 to 2.

5. The method according to any one of claims 1 to 4, characterized in that the concentration of all surfactants together 0.01 to 5 wt.% With respect to the total amount of the aqueous surfactant formulation.

6. The method according to any one of claims 1 to 5, characterized in that the concentration of all surfactants together 0.01 to 2 wt.% With respect to the total amount of the aqueous surfactant formulation.

7. The method according to any one of claims 1 to 6, characterized in that the amount of the surfactants of the general formula (I) is at least 50 wt.% With respect to the total amount of all surfactants used.

8. The method according to any one of claims 1 to 6, characterized in that the surfactant formulation comprises as surfactant exclusively at least one surfactant of the general formula (I).

9. The method according to any one of claims 1 to 8, characterized in that the at least one surfactant of the general formula (I) is used in combination with bases.

10. Process according to claim 9, characterized in that the bases are one selected from the group of sodium hydroxide or sodium carbonate.