RU2772807C2 - Solubility enhancers based on allyl alcohol for aqueous compositions of surfactants for enhancing oil extraction - Google Patents

Abstract

FIELD: oil industry.

SUBSTANCE: group of inventions relates to the extraction of crude oil from underground oil-bearing reservoirs. A method for the extraction of crude oil from underground oil-bearing reservoirs includes: providing an aqueous composition containing water and a surfactant mixture, injecting the specified composition into an underground oil-bearing reservoir through at least one injection well, reducing the tension at the interface of crude oil-water to less than 0.1 mN/ m, and extracting crude oil from the reservoir through at least one producing well. The surfactant mixture contains at least surfactant (A) with the general formula

and a solubility enhancer (B) with the general formula

where R¹ is a hydrocarbon fragment with from 8 to 36 carbon atoms, R² is a hydrocarbon fragment with from 2 to 16 carbon atoms, R³ is selected from a simple bond group, an alkylene group -(CH₂)_o-, where o is from 1 to 3, a group -CH₂-CH(OH)-CH₂-, R⁴ is an allyl group H₂C=CH-CH₂-, Y^- is an anionic group selected from -COO^- or -SO₃ ^-, M⁺ is at least cation selected from a group: H⁺, alkali metal ions, NH₄ ⁺, and organic ammonium ions, a is a number from 0 to 69, b is a number from 3 to 70, c is a number from 0 to 50, x is a number from 1 to 69, y is a number from 0 to 50, and where R³, Y^- and M⁺ in (A) and (B) are identical, x<b, y=c, and the molar ratio of surfactant (A)/solubility enhancer (B) is from 98:2 to 60:40.

EFFECT: good solubility of surfactants for increasing oil extraction in reservoir water at a reservoir temperature, reduction in the surface tension at the interface between crude oil and reservoir water to a level of less than 0.1 mN/m.

17 cl, 1 tbl

Description

The present invention relates to a method for extracting crude oil from a subterranean oil reservoir comprising at least the following steps of providing an aqueous surfactant composition comprising water and a mixture of surfactants, injecting said surfactant composition into a subterranean oil reservoir through at least at least one injection well, thereby reducing the tension at the crude oil-water interface to less than 0.1 mN/m, and extracting crude oil from the formation through at least one production well.

The present invention further relates to said aqueous surfactant composition and methods for preparing the same, and to the use of a solubility enhancer (B) to enhance the solubility of the anionic surfactant (A).

In natural oil fields, oil is present in the cavities of pore reservoirs, compacted to the surface of the earth by impermeable overlying layers. The cavities may be very small cavities, capillaries, pores, or the like. The necks of the fine pores may have a diameter of, for example, only about 1 µm. Along with oil, including natural gas fractions, the field usually also contains water with a higher or lower salt content.

If the oil field has sufficient autogenous pressure, after the formation is drilled, oil flows through the well to the surface on its own due to autogenous pressure (primary oil recovery). However, even if sufficient autogenous pressure is initially present, the reservoir autogenous pressure generally decreases relatively quickly during oil recovery, and thus only small amounts can usually be recovered from the amount of oil present in the reservoir in this way, according to the type of reservoir.

Therefore, when primary production declines, it is a known method to drill additional wells, so-called injection wells, in the oil reservoir, in addition to wells that serve to produce oil, so-called production wells. Through such injection wells, water is injected into the formation to maintain pressure or re-increase it. Water injection causes oil to flow through the cavities in the formation, gradually moving from the injection well towards the production well. This method is known as waterflooding and is one of the so-called secondary oil recovery methods. However, this only works as long as the cavities are completely filled with oil and the more viscous oil is pushed forward by the water. Once the moving water breaks through the cavities, it flows along the path of least resistance from that time, i.e. through the formed channel, and no longer pushes the oil further. With continued waterflooding, more and more oil is retained in the capillaries as isolated spherical droplets while water flows through the formed channels without effect. Therefore, the amount of oil produced from the production well decreases more and more, and the amount of water increases more and more.

When economically viable oil recovery is not possible or no longer possible using primary or secondary oil recovery technologies for tertiary oil recovery, also known as "Enhanced Oil Recovery (EOR)", it can be applied to increase oil recovery. The tertiary production of mineral oils includes processes in which suitable chemicals such as surfactants and/or polymers are used as oil recovery aids. An overview of tertiary oil recovery using chemicals can be found, for example, in D. G. Kessel, Journal of Petroleum Science and Engineering, 2 (1989) 81 - 101.

Tertiary oil recovery technologies include what is called "surfactant flooding". In surfactant flooding, aqueous formulations containing suitable surfactants are injected through injection wells into a subterranean oil reservoir. Surfactants reduce the tension at the oil/water interface and thereby mobilize additional oil from the formation.

The technical requirements for surfactants to improve recovery are high. Subterranean oil reservoirs may have different temperatures, for example, temperatures from 30 to 120°C, and, in addition to crude oil, may also contain formation water. The salinity of the formation water may be up to 350,000 ppm, and the formation water may also contain divalent cations such as Mg ²⁺ and Ca ²⁺ . It is common to use formation water or sea water to prepare an aqueous surfactant composition to enhance oil recovery. Therefore, suitable surfactants for enhancing oil recovery should have good solubility in the formation water at the formation temperature and should reduce the interfacial tension between the crude oil and the formation water to less than 0.1 mN/m.

Surfactants often either have good solubility in formation water at formation temperature or exhibit low interfacial tension, but often surfactants do not meet both requirements at the same time. To fulfill both requirements, mixtures of two or more different surfactants can be used, for example a more hydrophilic and a more hydrophobic surfactant. However, when using mixtures of surfactants, an additional problem arises, namely that the properties of the mixture depend not only on the nature of the surfactants used, but also on the mixing ratio of the surfactants.

While the blending ratio can be properly adjusted without problems when preparing an aqueous surfactant composition to enhance oil recovery, it may happen that the blending ratio does not remain constant after injection into the formation, but the blending ratio changes. This effect can be caused by the following mechanism: when passing through a subterranean formation, two surfactants can become chromatographically separated if one of the two surfactants is adsorbed to the surface of the formation better than the other. Such a separation can particularly occur if the surfactants are chemically very different or if they do not form mixed micelles with each other. Thus, for a mixture of surfactants, the surfactants either should not become chromatographically separable, or the properties of the mixture should not change, or at least should not change too much when changing the ratio in the mixture. The search for mixtures of surfactants that meet all of these requirements is laborious and complex.

US 4,448,697 discloses a process for recovering petroleum products from an underground oil and gas reservoir using a mixture of an anionic sulfate or sulfonate surfactant in admixture with a non-ionic surfactant RO-(C ₄ H ₈ O) _1-40 (C ₂ H ₄ O ) _>10 H. R is selected from C ₁ -C ₆ alkyl, phenyl or tolyl.

US 4,542,790 discloses a method for recovering oil from an underground deposit by injecting a mixture of surfactants containing an anionic surfactant of the general formula

R-(OCH ₂ CH ₂ ) _n -OCH ₂ COOM and R-(OCH ₂ CH ₂ ) _n H,

where n is from 1 to 30, and R is selected from linear or branched aliphatic groups with 4 to 20 carbon atoms, or alkylphenyl or dialkylphenyl groups with 1 to 14 carbon atoms in the alkyl groups.

WO 2012/158645 A1 discloses a surfactant mixture suitable for enhanced oil recovery containing propoxylated C ₁₂ -C ₂₀ sulfate, C ₁₂ -C ₂₀ internal olefin sulfonate and ethoxylated C ₄ -C ₁₂ alcohol sulfate.

WO 2013/090614 A1 discloses a surfactant-free aqueous composition containing a light co-solvent, a water-soluble polymer and an alkaline agent. The light co-solvent may have the formula

H-(CH ₂ ) _1-6 (OCH ₂ CHR) _n OH,

where n is from 0 to 30 and R is H, methyl or ethyl. The mixture can be used to produce oil.

WO 2015/048139 A1 discloses a petroleum recovery composition containing two different anionic surfactants selected from propoxylated primary alcohol carboxylates or propoxylated primary alcohol glycerol sulfonates, where the average carbon number is from 12 to 30 carbon atoms, the degree of branching is from 0.5 to 3.5 and the amount of propylene oxide groups is from 1 to 20.

WO 2015/048142 A1 discloses an oil recovery composition containing two different anionic surfactants selected from propoxylated primary alcohol carboxylates or propoxylated primary alcohol glycerol sulfonates and from alkoxylated primary alcohol carboxylates or alkoxylated primary alcohol glycerol sulfonates.

WO 2011/045254 A1 discloses that allyl alcohol can be obtained by rearrangement of propylene oxide in the presence of KOH, and that such allyl alcohol can then be alkoxylated and sulfated. However, said publication also mentions that such products are not active as surfactants.

It is an object of the present invention to provide an aqueous surfactant composition for EOR processes that meets the requirements mentioned above in an optimized manner, especially considering properties, solubility, and the like of surfactants.

The problem is solved by a method for extracting crude oil from underground oil-bearing formations, preferably by injecting Winsor type III microemulsions into the formation, including at least the following stages:

(1) providing an aqueous surfactant composition comprising water and a mixture of surfactants,

(2) injecting said surfactant composition into the subterranean oil formation through at least one injection well, thereby reducing the tension at the crude oil-water interface to less than 0.1 mN/m, and

(3) extracting crude oil from the reservoir through at least one production well,

where the mixture of surfactants contains at least a surfactant (A) having the general formula

and

solubility enhancer (B) having the general formula

where

R ¹ is a hydrocarbon fragment having from 8 to 36 carbon atoms,

R ² is a hydrocarbon fragment having from 2 to 16 carbon atoms,

R ³ is selected from the group

простой связи,

simple connection,

алкиленовой группы -(СН₂)_o-, где о представляет собой от 1 до 3,

alkylene group -(CH ₂ ) _o -, where o represents from 1 to 3,

группы -СН₂-СН(ОН)-СН₂-,

groups -CH ₂ -CH (OH) -CH ₂ -,

R ⁴ is an allyl group H ₂ C=CH-CH ₂ -,

Y ^- is an anionic group selected from -COO ^- or -SO ₃ ^- ,

M ⁺ is at least a cation selected from the group H ⁺ , alkali metal ions, NH ₄ ⁺ , and organic ammonium ions,

a is a number from 0 to 69,

b is a number from 3 to 70,

c is a number from 0 to 50,

x is a number from 1 to 69,

y is a number from 0 to 50,

and where

R³, Y^-, и М⁺ в (А) и (В) являются идентичными,

R ³ , Y ^- , and M ⁺ in (A) and (B) are identical,

х<b,

x<b,

у=с, и

y=s, and

молярное отношение поверхностно-активного вещества (А)/усилителя растворимости (В) представляет собой от 98: 2 до 60: 40.

the molar ratio of surfactant (A)/solubility enhancer (B) is 98:2 to 60:40.

The object is also achieved by means of an aqueous composition of surfactants as defined herein, as well as by the use of a solubility enhancer (B) of the general formula

as defined herein, to enhance the solubility of the anionic surfactant (A) of general formula (I)

as defined in this document.

Surprisingly, it has been found that the solubility enhancer (B) can act as a surfactant and improve the solubility of the surfactant (A) without significantly reducing the interfacial tension reducing the properties of the surfactant (A), especially when limiting characteristics such as elevated temperature and salt content.

With regard to the present invention, the following can be specifically stated:

For the method of extracting crude oil from underground formations according to the present invention, an aqueous surfactant composition according to the present invention is used, containing at least water and a mixture of surfactants containing at least a surfactant (A) and a solubility enhancer (B ).

Both surfactants (A) and (B) are alkoxylated anionic surfactants, where each surfactant (A) and (B) is present in the mixture of surfactants in a specific distribution with respect to the extent of each alkoxylation step. Accordingly, surfactants (A)/(B) can be considered as mixtures of different surfactants for each type, (A) and (B). In the case of surfactants and in the singular, the main component of the chemical compounds with the highest mole fraction is considered. Accordingly, for a plurality of surfactants of general formula (I) or (II), the numbers a, b, c and x, each represent the average value for all surfactant molecules, since the alkoxylation of alcohol with ethylene oxide or propylene oxide or higher alkylene oxides (for example, from butylene oxide to hexadecene oxide) in each case provides a certain distribution of chain lengths. This distribution can be described in a manner known in principle as the so-called polydispersity DD=M _w /M _n is the ratio of the weight average molar mass and the number average molar mass. Polydispersity can be determined by methods known to those skilled in the art, such as gel permeation chromatography.

Surfactants (A) have the general formula

The surfactant of formula (I) contains a hydrocarbon moiety R ¹ , an alkyleneoxy group -(CH ₂ CH(R ² )O)-, b a propyleneoxy group-(CH ₂ CH(CH ₃ )O)- and an ethyleneoxy group -(CH ₂ CH ₂ O)-, which are preferably arranged in a block manner, in the order indicated in formula (I). It will be apparent to one skilled in the art that, due to manufacturing conditions, the transition between blocks need not be abrupt, but may also be gradual, so that some mixing between blocks may be observed. In addition, a and c may be 0, so one or both blocks may not be present in certain embodiments of the invention. Surfactants further include an anionic end group -Y ^- M ⁺ , which is linked by an R ³ linking group to an ethyleneoxy or propoxy block.

R ¹ is a hydrocarbon moiety having 8 to 36, preferably 12 to 32, more preferably 12 to 30, more preferably 14 to 28 carbon atoms. The hydrocarbon fragment may be linear or branched, unsaturated or saturated, aliphatic and/or aromatic. Of course, the surfactants (A) may contain two or more different R ¹ hydrocarbon moieties. Preferably R ¹ is aliphatic, more preferably saturated (alkyl), and more preferably linear.

According to one embodiment, R ¹ is an aromatic hydrocarbon moiety or an aromatic hydrocarbon moiety substituted with aliphatic groups. Examples of substituted aromatic groups include alkyl-substituted phenyl groups such as a dodecylphenyl group.

According to another embodiment, R ¹ is a linear or branched, saturated or unsaturated aliphatic hydrocarbon moiety having 8 to 36, preferably 12 to 32, more preferably 14 to 28 carbon atoms.

In one embodiment, R ¹ is a linear saturated or unsaturated, preferably a linear saturated aliphatic hydrocarbon moiety having 12 to 20 carbon atoms, preferably 14 to 18 carbon atoms, and more preferably 16 to 18 carbon atoms. Preferably the number of carbon atoms is even. Such hydrocarbon moieties may be derived from fatty alcohols. Examples of such groups include n-dodecyl, n-tetradecyl, n-hexadecyl, n-octadecyl and n-eicosyl moieties. Preferably, the surfactants (A) may contain at least two different linear aliphatic saturated hydrocarbon fragments R ¹ whose carbon number differs by two. Examples of such combinations include n-dodecyl and n-tetradecyl, n-tetradecyl and n-hexadecyl, n-hexadecyl and n-octadecyl, and n-octadecyl and n-eicosyl. Preferably, the surfactants (A) may contain n-hexadecyl and n-octadecyl moieties.

According to another embodiment, R ¹ is a branched saturated aliphatic hydrocarbon group having the general formula CH ₂ -CH(R ⁵ )(R ⁶ ) (X), where R ⁵ and R ⁶ are independently linear alkyl groups, having from 4 to 16 carbon atoms, provided that the total number of carbon atoms in such fragments (X) is an even number from 12 to 32, preferably from 16 to 28 carbon atoms. Such hydrocarbon moieties come from Guerbet alcohols. Preferably, two or more such hydrocarbon moieties derived from Guerbet alcohols may be present.

According to one embodiment, the surfactants (A) contain R ¹ hydrocarbon moieties selected from the group consisting of 2-hexyldecyl, 2-octyldecyl, 2-hexyldodecyl or 2-octyldodecyl, or mixtures thereof.

According to one embodiment, the surfactants (A) contain hydrocarbon fragments R ¹ selected from the group consisting of 2-decyltetradecyl, 2-dodecyltetradecyl, 2-decylhexadecyl or 2-dodecyltetradecyl, or mixtures thereof.

In formula (I), R ² is a hydrocarbon fragment having from 2 to 16 carbon atoms, for example, the group-(CH ₂ CH(R ² )O)- is derived from butylene oxide or higher alkylene oxides. The hydrocarbon moieties may in particular be selected from linear or branched, unsaturated or saturated, aliphatic hydrocarbon moieties having 2 to 16 carbon atoms, preferably saturated, more preferably saturated and linear hydrocarbon moieties having 2 to 16 carbon atoms. Most preferred are ethyl moieties. In addition, the hydrocarbon moieties may be selected from aromatic hydrocarbon moieties or hydrocarbon moieties substituted with aliphatic groups where the total number of carbon atoms is from 6 to 10. However, preferably R ² is an alkyl group as above.

In formulas (I) and (II), R ³ is selected from the group consisting of

простой связи,

simple connection,

алкиленовой группы -(СН₂)₀-, где о представляет собой от 1 до 3, и

alkylene group -(CH ₂ ) ₀ -, where o represents from 1 to 3, and

группы -СН₂-СН(ОН)-СН₂-.

groups -CH ₂ -CH (OH) -CH ₂ -.

According to a first embodiment of the present invention, Y ^- is C(O)O ^- and R ³ is -(CH ₂ ) _o - resulting in a carboxylate where o is 1, 2 or 3, preferably 1.

According to another embodiment of the present invention, Y ^- is an SO ₃ ^- group, and R is -(CH ₂ ) _o - or -CH ₂ CH (OH) CH ₂ -, leading to a sulfonate group, where o is 2 or 3.

According to another embodiment of the present invention, Y ^- represents an SO ₃ ^- group, and R ³ represents a single bond, leading to a sulfate group.

M ⁺ is at least a cation selected from the group of alkali metal ions, NH ₄ ⁺ , and organic ammonium ions. Preferably M ⁺ is Li ⁺ , Na ⁺ , K ⁺ , Rb ⁺ , Cs ⁺ , NH ₄ ⁺ , N(CH ₂ CH ₂ OH) ₃ H ⁺ , N(CH ₂ CH[CH ₃ ]OH) ₃ H ⁺ , N(CH ₃ )(CH ₂ CH ₂ OH) ₂ H ⁺ , N(CH ₃ ) ₂ (CH ₂ CH ₂ OH)H ⁺ , N(CH ₃ ) ₃ (CH ₂ CH ₂ OH) ⁺ , N( CH ₃ ) ₃ H ⁺ , or N(C ₂ H ₅ ) ₃ H ⁺ . More preferably, M ⁺ is Li ⁺ , Na ⁺ , K ⁺ , Rb ⁺ , Cs ⁺ , or NH ₄ ⁺ . Even more preferably, M ⁺ is Na ⁺ or K ⁺ . Even more preferably, M ⁺ is Na ⁺ .

The variable "a" is the number of higher alkoxylates as butyleneoxy. In a preferred embodiment, a is 0.

The variable "b" represents the number of propyleneoxy groups in formula (I). According to a preferred embodiment b is a number from 5 to 60. More preferably b is from 5 to 50, more preferably b is from 5 to 40, more preferably from 5 to 30, even more preferably from 6 to 20 and even more preferably b is 6 to 10, even more preferably b=7.

The variable "c" is the number of ethyleneoxy groups in formula (I). Preferably, c is a number from 1 to 50, more preferably from 2 to 40, more preferably from 3 to 30, more preferably from 5 to 20, even more preferably c=10.

Preferably the sum of a, b and c, preferably b and c (a=0) is 5 to 75. More preferably the sum is 5 to 70, even more preferably 6 to 60, even more preferably 7 to 50, even more preferably 8 to 40, even more preferably 10 to 30, and even more preferably 15 to 20.

The solubility enhancer (B) is represented by the formula (II)

R ⁴ -O-(CH ₂ CH(CH ₃ )O) _x -(CH ₂ CH ₂ O) _y -R ³ -Y ^- M ^+.

In formula (II) R ⁴ represents an allyl group.

The variable "x" is the number of propyleneoxy groups in formula (II). Preferably x is a number from 1 to 44, more preferably from 1 to 40, more preferably from 1 to 30, more preferably from 1 to 20, even more preferably from 1 up to 10, even more preferably 1 to 5, even more preferably x=1.6.

The variable "y" is the number of the ethyleneoxy group in formula (II). Preferably, y is a number from 1 to 50, more preferably from 2 to 40, more preferably from 3 to 30, more preferably from 5 to 20, even more preferably y =10.

For formulas (I) and (II), the following conditions are given R³, Y^-, and M⁺ in (A) and (B) are identical: Respectively for R³, Y^-, them⁺ the same applies to formula (II), which are described herein for R, Y^-, and M in formula (I).

x<b. Accordingly, the degree of propoxylation for the enhancer (B) is less than for the surfactant (A).

y=c: Accordingly, the degree of ethoxylation is the same for (A) and (B).

The molar ratio of surfactant (A)/solubility enhancer (B) is from 98:2 to 60:40, preferably from 95:5 to 65:35, more preferably from 95:5 to 70:30, more preferably from 90:10 to 80:20, even more preferably 85:15.

The alkoxylates (A) and (B) can be prepared by methods known in the art, starting from the appropriate alcohol R ¹ OH, R ⁴ OH, respectively, which are commercially available or can be synthesized by methods well known to the person skilled in the art. Also, alkoxylation and subsequent functionalization to introduce an R ³ -Y ^- M ⁺ group is well known in the art.

The number of alkoxy groups can be controlled by the molar ratio of the respective starting materials. Alkoxylates (A) and (B) can be obtained separately and mixed to obtain the desired ratio.

Alternatively, by choosing a catalyst during alkoxylation, an alkoxylate can be obtained in the preparation of (A) as a by-product due to a side reaction of propylene oxide with allyl alcohol. This has the advantage that the mixture of surfactants according to the present invention with the mixture of surfactants can be obtained in one reaction step ("one-pot reaction"). However, the single vessel reaction is limited in terms of the choice of catalyst. Since NaOH and KOH affect the formation of allyl alcohol at higher temperatures with the ratio (A) to (B) as indicated in the present composition, it cannot be achieved using a double metal cyanide catalyst (DMC), double hydroxide clays, or a CsOH catalyst. Since the formation of allyl alcohol begins during the propoxylation of the alcohol R ¹ OH, the degree of propoxylation is always lower for (B) compared to (A) (x<b). However, this effect will not affect the ethoxylation during the reaction in one vessel (y=c) and the subsequent derivatization (RR ³ , Y ^- , M ⁺ in (A) and (B) are identical). The degree of formation of allyl alcohol can be affected by the amount of catalyst, the temperature, and the amount of propylene oxide used to form PO. The degree of formation of allyl alcohol increases with an increase in the amount of catalyst, with an increase in temperature and/or with an increase in the amount of propylene oxide used to form PO. In the case of a=0, a low amount of catalyst (less than 0.05 eq. KOH relative to the amount of 1.0 eq. R ¹ -OH), moderate temperature (130°C or less), and low to moderate propylene oxide (less 8 equivalents of propylene oxide) used to form RO, the ratio (A) to (B) is 99.5:0.5 and higher.

Another object of the present invention is a process for preparing a composition of surfactants according to the present invention, comprising at least the following steps

(a) optionally alkoxylation of the alcohol R ¹ OH with alkylene oxides of the general formula

thus obtaining R ¹ -O-(CH ₂ CH(R ² )O) _and H (VI),

(b) alkoxylation of the alcohol R ¹ OH or the alkoxylated alcohol R ¹ -O-(CH ₂ CH(R ² )O) _a H (VI) with propylene oxide, thereby obtaining a mixture

и

and

(c) optionally alkoxylating mixture (V) and (VI) with ethylene oxide, thus obtaining a mixture

и

and

(d) introducing terminal anionic groups -Y ^- M ⁺ into the mixture (VII) and (VIII), thus obtaining a mixture

surfactant (A) having the general formula

and

solubility enhancer (B) having the general formula

where R ¹ , R ² , R ³ , R ⁴ , Y ^- , M ⁺ , a, b, c, x, and y are as defined above.

Optionally, step b) is carried out in the presence of NaOH or KOH as a catalyst.

Preferably the mixture (VII) and (VIII) is reacted with sulfur trioxide or chlorosulfonic acid and then neutralized with a base (eg an alkali metal hydroxide such as NaOH). Alternatively, a mixture of (VII) and (VIII) is reacted with sulfamic acid (SO ₃ NH ₃ ).

According to another preferred embodiment, a mixture of (VII) and (VIII) is reacted with an ω-halogenated carboxylic acid R ⁵ -(CH ₂ ) _o -COOH or a salt thereof, where R ⁵ is selected from F, O, Br, or I and o is 1 to 3, preferably 1, thus obtaining a mixture of surfactant (A) having the general formula

and a solubility enhancer (B) having the general formula

In order to increase the amount of (B), separately prepared (B) can be added to the surfactant mixture after the one-pot reaction.

The aqueous composition of surfactants contains water and a mixture of surfactants with at least (A) and (B). The composition may further contain salts. Generally, saline water is used in the aqueous surfactant composition. Salt water can be, inter alia, river water, sea water, water from an aquifer close to the formation, so-called injection water, formation water, so-called produced water, which is re-injected again, or mixtures of the waters described above. However, mineralized water can also be that which has been derived from saltier water: for example, partial desalination, depletion of polyvalent cations, or by dilution with fresh water or potable water. The mixture of surfactants may preferably be presented as a concentrate, which may also contain salt as a result of preparation.

Another object of the present invention is the use of a solubility enhancer (B) of the general formula

as defined herein to enhance the solubility of the anionic surfactant (A) of general formula (I)

as defined in this document. Preferably, (A) and (B) are used in the ratio as described herein, more preferably (A) and (B) are used in the aqueous composition of the present invention.

According to a preferred embodiment, the crude oil recovery process of the present invention is a Winsor type III microemulsion injection method, which is known in the art.

The Winsor type III microemulsion is in equilibrium with excess water and excess oil. Under these microemulsion conditions, the surfactants coat the oil-water interface and lower the interfacial tension s, more preferably to <10-2 mN/m (ultra low interfacial tension). In order to achieve an optimal result, the proportion of microemulsion in the water-microemulsion-oil system for a certain amount of surfactant must naturally be maximized, since this allows the reduction of interfacial tensions to be achieved.

In this way, the shape of the oil droplets can be changed (surface tension at the interface between oil and water is reduced to such an extent that the smallest surface state is no longer maintained and a spherical shape is no longer preferred), and they can be forced through the capillary holes by injection water.

When all oil-water interfaces are coated with surfactant, in the presence of an excess amount of surfactant, a Winsor type III microemulsion is formed. This thus constitutes a reservoir for surfactants which induce very low interfacial tension between the oil phase and the water phase. Because the Winsor type III microemulsion has a low viscosity, it also migrates through porous reservoir rocks during the injection process. Emulsions, on the other hand, can remain suspended in the porous matrix and block the formations. If a Winsor Type III microemulsion encounters an oil-water interface not yet coated with a surfactant, then the surfactant from the microemulsion can significantly reduce the interfacial tension of this new interface and result in oil mobilization (e.g. , by deformation of oil droplets).

The oil droplets may subsequently coalesce to form a continuous oil bank. This has two advantages:

First, when a continuous oil bank advances through new porous rock, the oil droplets present there may merge with the bank.

In addition, the combination of the oil droplets to form the oil bank significantly reduces the oil-water interface and hence the surfactant, which is no longer needed, is released again. Thereafter, the released surfactant, as described above, can mobilize the oil droplets remaining in the formation.

Therefore, Winsor type III microemulsion injection is an extremely efficient process and requires much less surfactant compared to the emulsion injection process. When injecting the microemulsion, surfactants are usually optionally added together with co-solvents and/or basic salts (optionally in the presence of complexing agents). The thickening polymer solution is then added to control mobility. Another option is to introduce a mixture of thickening polymer and surfactants, co-solvents and/or basic salts (optionally with a complexing agent), and then a solution of thickening polymer to control mobility. These solutions should generally be clear to prevent clogging of the tank.

In the context of the method of the present invention for crude oil recovery, the use of the surfactant composition of the present invention lowers the interfacial tension between oil and water to values of <0.1 mN/m, preferably to <0.05. mN/m, more preferably up to <0.01 mN/m. Thus, the surface tension at the interface between oil and water is reduced 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 up to values in the range from 0.01 mN/m to 0.0001 mN/m. The indicated values refer to the prevailing formation temperature. A particularly preferred embodiment is the operation of injecting a Winsor type III microemulsion into the formation as described above.

According to another preferred embodiment of the present invention, a thickening polymer from the group of biopolymers or from the group of copolymers based on acrylamide is added to the aqueous surfactant composition. The copolymer may consist of the following units, among others:

- acrylamide and sodium salt of acrylic acid

- acrylamide and sodium salt of acrylic acid and N-vinylpyrrolidone

- acrylamide and sodium salt of acrylic acid and AMPS (2-acrylamido-2-methylpropane sulfonic acid sodium salt)

- acrylamide and sodium salt of acrylic acid and AMPS (2-acrylamido-2-methylpropanesulfonic acid sodium salt) and N-vinylpyrrolidone.

The copolymer may also optionally contain association groups. Preferred copolymers are described in EP 2432807 or WO 2014095621. Other preferred copolymers are described in US 7700702.

According to a preferred embodiment of the present invention, the characteristic feature of this method is that the production of crude oil from underground oil fields is a surfactant flooding method or a surfactant/polymer flooding method and is not an alkali/surfactant/flooding method. polymer and is not a waterflooding method in which Na ₂ CO ₃ is introduced into the well.

According to a particularly preferred embodiment of the present invention, the characteristic feature of this method is that the production of crude oil from underground oil fields is a Winsor type III microemulsion method or a Winsor type III microemulsion/polymer flooding method and is not an alkali/ Winsor type III microemulsion/polymer and is not a waterflooding method in which NaCO ₃ is injected into the well

Underground oil reservoirs are usually fallow rocks, which may be sandy or carbonate.

According to a preferred embodiment of the present invention, a sand deposit, where more than 70 wt. percent sand (quartz and/or feldspar) is present and up to 25 wt. percent of other minerals selected from kaolinite, smectite, illite, chlorite and/or pyrite may be present. Preferably more than 75 wt. percent sand (quartz and/or feldspar) is present, and up to 20 wt. percent of other minerals selected from kaolinite, smectite, illite, chlorite and/or pyrite may be present. Especially preferably more than 80 wt. percent sand (quartz and/or feldspar) is present and up to 15 wt. percent of other minerals selected from kaolinite, smectite, illite, chlorite and/or pyrite may be present.

API Gravity (American Petroleum Institute Gravity) is a standard unit of gravity commonly used in the US for crude oil. It is used throughout the world to characterize and as a quality standard for crude oil. API gravity is calculated from the relative density p _rel of crude oil at 60° F (15.56° C) based on water using

Density in degrees API=(141.5 / p _rel ) - 131.5.

According to the present invention, the crude oil from the field must have at least 10°API. Preferably at least 12° API. Particularly preferably at least 15° API. Particularly preferably at least 20° API.

The field temperature in the oil field in which the method according to the present invention is used according to the invention is from 15 to 150°C, especially from 20 to 140°C, preferably from 25 to 130°C, more preferably from 30°C to 120 °C and, for example, from 35°C to 110°C.

The salts in the deposit water may in particular be salts of alkali metals and alkaline earth metals. Exemplary cations include Na ⁺ , K, Mg ²⁺ and/or Ca ²⁺ and exemplary anions include chloride, bromide, hydrogen carbonate, sulfate or borate. The amount of alkaline earth metal ions may preferably be 0 to 53,000 ppm, more preferably 1 ppm to 20,000 ppm, and even more preferably 10 to 6,000 ppm.

In general, at least one or more alkali metal ions are present, especially at least Na ⁺ . In addition, alkaline earth metal ions may be present, in which case the mass ratio of alkali metal ions/alkaline earth metal ions is generally ^3: 2, preferably ³ :3. The anions present are generally at least one or more than one halide ion, especially at least Cl ^- . Typically, the amount of Cl is at least 50 wt. %, preferably at least 60 wt. % based on the total amount of all anions.

The total amount of all salts in the formation water can be up to 350,000 ppm (wt. parts), based on the total sum of all components in the composition, for example, from 2000 ppm to 350,000 ppm, especially from 5000 ppm to 250,000 ppm per million. If sea water is used for injection, the salt content may be from 2000 ppm to 40,000 ppm, and if formation water is used, the salt content may be from 5000 ppm to 250,000 ppm, for example, from 10,000 ppm per million to 200,000 ppm.

The aqueous surfactant composition contains (A) and (B) and may contain other surfactants. The concentration of all surfactants together is from 0.05% to 0.49 wt. %, based on the total amount of total composition administered. The total concentration of surfactants is preferably from 0.06% to 0.39 wt. %, more preferably from 0.08% to 0.29 wt. %. Preferably no additional surfactants other than (A) and (B) are present.

According to another preferred embodiment of the present invention, at least one organic co-solvent may be added to the inventive mixture of surfactants. They are preferably water-miscible solvents, but solvents having only partial miscibility with water can also be used. As a rule, the solubility should be at least 50 g/l, preferably at least 100 g/l. Examples include aliphatic C3-C8 alcohols, preferably C4-C6 alcohols, more preferably C3-C6 alcohols, which may be substituted with 1 to 5, preferably 1 to 3, ethyleneoxy units to achieve sufficient solubility in water. Additional examples include aliphatic diols having 2 to 8 carbon atoms, which may optionally also have additional substitution. For example, the co-solvent may be at least one selected from the group of 2-butanol, 2-methyl-1-propanol, butylethylene glycol, butyldiethylene glycol or butyltriethylene glycol.

Accordingly, preferably, the aqueous surfactant composition contains both an anionic surfactant (A) of general formula (I) and an enhancer (B) of general formula (II), as well as a co-solvent selected from the group of aliphatic alcohols having from 3 to 8 carbon atoms, or from the group of alkylmonoethylene glycols, alkyldiethylene glycols or alkyltriethylene glycols, where the alkyl radical is an aliphatic hydrocarbon radical having 3 to 6 carbon atoms.

Particular preference is given to the aqueous composition of surfactants according to the present invention in the form of a concentrate containing from 20 wt. % up to 70 wt. % mixture of surfactants, from 10 wt. % up to 40 wt. % water and from 10 wt. % up to 40 wt. % co-solvent, based on the total amount of the concentrate, where the co-solvent is selected from the group of aliphatic alcohols having from 3 to 8 carbon atoms, or from the group of alkyl monoethylene glycols, alkyl diethylene glycols or alkyl triethylene glycols, where the alkyl radical is an aliphatic hydrocarbyl radical having from 3 to 6 atoms carbon, and the concentrate is free-flowing at 20°C and has a viscosity at 40°C<1500 mPa.s at 200 Hz.

Most preferably, the concentrate contains butyl diethylene glycol as a co-solvent.

Another object of the present invention is a composition according to the present invention further comprising surfactants (C) which are not identical to surfactants (A) or (B), and

- selected from the group of alkylbenzenesulfonates, alpha-olefinsulfonates, internal olefinsulfonates, paraffinsulfonates, where surfactants have from 14 to 28 carbon atoms; and/or

- are selected from the group of alkyl ethoxylates and alkyl polyglycosides, where a specific alkyl radical has from 8 to 18 carbon atoms.

For surfactants (C), particular preference is given to alkyl polyglucosides which are formed from primary linear fatty alcohols having from 8 to 14 carbon atoms and having a glucosation level from 1 to 2, and alkyl ethoxylates which are formed from primary alcohols having from 10 to 18 carbon atoms, and having an ethoxylation level of 3 to 25.

Surfactants (A) and (B) according to the general formulas (I) or (II) can preferably be obtained by base-catalyzed alkoxylation. In this case, the alcohol R ¹ OH can be mixed in a pressure reactor with alkali metal hydroxides (eg NaOH, KOH, CsOH), preferably potassium hydroxide, or with alkali metal alkoxides, eg sodium methoxide or potassium methoxide. Water (or MeOH) still present in the mixture can be removed by reduced pressure (eg <100 mbar) and/or increased temperature (30 to 150°C). The alcohol is then present in the form of the corresponding alkoxide. This is followed by inertization with an inert gas (eg nitrogen) and the gradual addition of alkylene oxide(s) at a temperature of 60 to 180°C to a pressure of not more than 20 bar (preferably not more than 10 bar). According to a preferred embodiment, the alkylene oxide is dosed initially at 120°C. During the reaction, the generated heat of reaction causes the temperature to rise to 170°C.

According to another preferred embodiment of the present invention, the higher alkylene oxide (for example, butylene oxide or hexadecene oxide) is first added at a temperature in the range of 100 to 145°C, then propylene oxide is added at a temperature in the range of 100 to 145°C, and then ethylene oxide is added at a temperature of in the range from 120 to 165°C. At the end of the reaction, the catalyst can, for example, be neutralized by adding an acid (eg acetic acid or phosphoric acid) and filtered if necessary. However, the substance may also remain unneutralized.

Alkoxylation of alcohols R ¹ OH can also be carried out in other ways, for example, acid-catalyzed alkoxylation. Further, for example, clay double hydroxides as described in DE 43 25 237 A1 can be used, or bimetallic cyanide catalysts (DMC catalysts) can be used. Suitable DMC catalysts are disclosed, for example, in DE 10243361 A1, especially in chapters [0029] to [0041] and also in the literature cited there. For example, catalysts of the Zn-Co type can be used. To carry out the reaction, the alcohol R ¹ OH can be mixed with a catalyst, and the mixture is removed from water, as described above, and mixed with alkylene oxides, as described. Generally, no more than 1000 ppm of catalyst is used relative to the mixture, and because of this small amount, the catalyst may remain in the product. The amount of catalyst can typically be less than 1000 ppm, such as 250 ppm or less.

Further derivatization can be carried out by methods well known in the art. For example, to prepare carboxylates, a non-ionic alkoxylation intermediate may be reacted with stirring with chloroacetic acid or with sodium chloroacetic acid and in the presence of an alkali metal hydroxide or an aqueous alkali metal hydroxide to remove reaction water so that the water content in the reactor is maintained at a level between 0, 2 to 1.7% (preferably 0.3 to 1.5%) during carboxymethylation by applying reduced pressure and/or nitrogen bubbling.

Additionally, preferably, the methods of the present invention for the recovery of crude oil include process steps of the recovery methods of the present invention that are upstream of the injection stage.

The above-described method for recovering crude oil using an aqueous composition of surfactants (A) of general formula (I) and (B) of general formula (II) can optionally be carried out with the addition of additional methods. For example, a polymer or foam may optionally be added to control mobility. The polymer may optionally be introduced into the deposit along with the surfactant formulation, followed by the introduction of the surfactant formulation. It can also be administered only with a surfactant formulation or only after a surfactant formulation. The polymers may be acrylamide or biopolymer based copolymers. The copolymer may consist of the following units, among others:

- acrylamide and sodium salt of acrylic acid

- acrylamide and sodium salt of acrylic acid and N-vinylpyrrolidone

- acrylamide and sodium salt of acrylic acid and AMPS (2-acrylamido-2-methylpropanesulfonic acid sodium salt)

- acrylamide and sodium salt of acrylic acid and AMPS (2-acrylamido-2-methylpropanesulfonic acid sodium salt) and N-vinylpyrrolidone.

The copolymer may also optionally contain association groups. Useful copolymers are described in EP 2432807 or WO 2014095621. Other suitable copolymers are described in US 7700702.

The polymers can be stabilized by adding additional additives such as biocides, stabilizers, free radical scavengers and inhibitors.

Foam can be produced at the surface of the reservoir or in situ in the reservoir by introducing gases such as nitrogen or gaseous hydrocarbons such as methane, ethane or propane. Foam can be obtained and stabilized by adding a mixture of surfactants or other surfactants.

Optionally, it is also possible to add a base such as an alkali metal hydroxide or an alkali metal carbonate to the surfactant formulation, in which case it is combined with complexing agents or polyacrylates to prevent precipitation due to the presence of polyvalent cations. In addition, it is also possible to add a co-solvent to the composition.

This leads to the following (combined) ways:

- surfactant flooding

- Type III microemulsion flooding according to Winsor classification

- surfactant/polymer flooding

- Flooding with Winsor type III microemulsion/polymer

- alkali/surfactant/polymer flooding

- Winsor Type III Alkali/Microemulsion/Polymer Flooding

- surfactant/foam flooding

- waterflooding with Winsor type III microemulsion/foam

- alkali/surfactant/foam flooding

- Alkaline/Microemulsion Type III Winsor/Foam Flooding

According to a preferred embodiment of the invention, one of the first four methods is used (surfactant flood, Winsor type III microemulsion flood, surfactant/polymer flood, or Winsor type III microemulsion/polymer flood). Particularly preferred is a Winsor type III microemulsion/polymer flood.

In Winsor type III microemulsion/polymer flooding, in the first step, the surfactant formulation is injected with or without polymer. The composition of surfactants, in contact with crude oil, leads to the formation of a type III microemulsion according to the Winsor classification. In the second stage, only the polymer is introduced. In the first stage, in each case it is possible to use aqueous compositions having a higher salinity than in the second stage. Alternatively, both steps can also be carried out with water of the same salinity.

According to one embodiment, the methods can, of course, also be combined with waterflooding. In the case of flooding, water is injected into the oil field through at least one injection well and crude oil is extracted from the field through at least one production well. The water may be fresh or salty, such as sea water or mineral water. After waterflooding, the method according to the present invention can be used.

To carry out the method according to the present invention, one production well and at least one injection well are provided to an oil field. As a rule, the field is provided with several injection wells and several production wells. An aqueous composition of the described water-soluble components is pumped through at least one well in an oil field, and crude oil is extracted from the field through at least one production well. As a result of the pressure generated by the injected aqueous composition, referred to as "flooding", oil flows towards the production well and is produced through the production well.

The term "crude oil" or "oil" in this context, of course, means not only single-phase oil; on the contrary, the term also covers conventional crude oil and water emulsions. A person skilled in the art will understand that the oil field may also have a certain temperature distribution. The specified field temperature is based on the area of the field between the injection and production wells that is covered by water flooding. Methods for determining the temperature distribution of an oilfield are known in principle to those skilled in the art. The temperature distribution is usually determined from temperature measurements at specific locations in the reservoir combined with simulation-based calculations; simulation-based calculations also take into account the amount of heat introduced into the reservoir and the amount of heat removed from the reservoir.

The method according to the invention can be particularly applied in oil fields with an average permeability of 5 mD-4 D, preferably 50 mD-2 D and more preferably 200 mD-1 D. The permeability of an oil reservoir is indicated by a person skilled in the art in units of "darcy" (abbreviated "D" or " mD" for "milidarcy") and can be determined from the flow rate of the liquid phase in the oil reservoir depending on the pressure difference. The flow rate can be determined during rod flooding tests using cores extracted from the formation. Details of this are described, for example, in K. Wagen, G. Pusch, H. Frisch Muller "Oil and Gas", pages 37 ff., Ullmann's Encyclopedia of Industrial Chemistry, Online Edition, Wiley-VCH, Weinheim 2010. that the permeability in an oil field should not be heterogeneous, but should contain a certain distribution, and accordingly, the oil field permeability data means the average permeability.

Additives can be used, for example, to prevent unwanted side effects, such as undesired precipitation of salts, or to stabilize the polymer used. The compositions injected into the formation during the waterflooding process only flow very gradually towards the producing well, which means that they remain at reservoir conditions in the reservoir for an extended period. The degradation of polymers leads to a decrease in viscosity. This either needs to be taken into account when using more polymer, or it should be recognized that the efficiency of the method will deteriorate. In each case, the economic value of the method deteriorates. A variety of mechanisms may be responsible for polymer degradation. With suitable additives, the degradation of the polymer can be prevented or at least delayed, depending on the conditions.

According to one embodiment of the present invention, the aqueous composition used further comprises at least one oxygen scavenger. Oxygen scavengers react with oxygen that may be present in the aqueous composition and thus prevent the ability of oxygen to attack the polymeric or polyether groups. Examples of oxygen scavengers include sulfites, such as Na ₂ SO ₃ , bisulfites, phosphites, hypophosphites or dithionites.

According to another embodiment of the present invention, the aqueous composition used contains at least one free radical scavenger. Free radical scavengers can be used to counteract free radical degradation of the polymer. Compounds of this type can form stable compounds with free radicals. Free radical scavengers are known in principle to those skilled in the art. For example, they may be stabilizers selected from sulfur compounds, secondary amines, hindered amines, N-oxides, nitroso compounds, aromatic hydroxyl compounds or ketones. Examples of sulfur compounds include thiourea, substituted thioureas such as N,N'-dimethylthiourea, N,N'-diethylthiourea, N,N'-diphenylthiourea, thiocyanates such as ammonium thiocyanate or potassium thiocyanate, tetramethylthiuram disulfide and mercaptans such as 2- mercaptobenzothiazole or 2-mercaptobenzimidazole or salts thereof, eg sodium salts, sodium dimethyldithiocarbamate, 2,2'-dithiobis(benzothiazole), 4,4'-thiobis(6-tert-butyl-m-cresol). Other examples include phenoxazine, carboxylated phenoxazine salts, carboxylated phenoxazine, methylene blue, dicyandiamide, guanidine, cyanamide, paramethoxyphenol, paramethoxyphenol sodium, 2-methylhydroquinone, 2-methylhydroquinone salt, 2,6-ditert-butyl-4-methylphenol, butylhydroxyanisole, 8-hydroxyquinoline, 2,5-di(tert-amyl)-hydroquinone, 5-hydroxy-1,4-naphthoquinone, 2,5-di(tert-amyl)hydroquinone, dimedone, propyl 3,4,5- trihydroxybenzoate, ammonium N-nitrosophenylhydroxylamine, 4-hydroxy-2,2,6,6-tetramethyloxypiperidine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and 1,2,2,6,6- pentamethyl-4-piperidinol. Hindered amines such as 1,2,2,6,6-pentamethyl-4-piperidinol and sulfur compounds, mercapto compounds, especially 2-mercaptobenzothiazole or 2-mercaptobenzimidazole or salts thereof, such as sodium salts, are preferred, and particularly preferred is 2-mercaptobenzothiazole or its salts.

According to another embodiment of the present invention, the aqueous composition used contains at least one protective agent. Protective agents can react with free radicals and thus render them harmless. Examples include especially alcohols. Alcohols can be oxidized by free radicals, for example, to ketones. Examples include monohydric alcohols and polyhydric alcohols, such as 1-propanol, 2-propanol, propylene glycol, glycerol, butanediol, or pentaerythritol.

According to another embodiment of the present invention, the aqueous composition used further comprises at least one complexing agent. It is, of course, possible to use mixtures of different complexing agents. Complexing agents are generally anionic compounds that can form complex divalent and high valent metal ions, such as Mg ²⁺ or Ca ²⁺ . Thus, it is possible, for example, to prevent unwanted precipitation. In addition, any polyvalent metal ions present in the crosslinking of the polymer can be prevented by the acidic groups present, especially the COOH group. The complexing agents may especially be derivatives of a carboxylic acid or a phosphonic acid. Examples of complexing agents include ethylenediaminetetraacetic acid (EDTA), ethylenediaminesuccinic acid (EDDS), diethylenetriaminepentamethylenephosphonic acid (DTPMP), methylglycine diacetic acid (MGDA) and nitrilotriacetic acid (NTA). Of course, the corresponding salts of each of these may also be involved, for example the corresponding sodium salts. According to a particularly preferred embodiment of the present invention, MGDA is used as a complexing agent.

As an alternative or in addition to the above complexing agents, polyacrylates can also be used.

According to another embodiment of the present invention, the composition further comprises at least one organic co-solvent as noted above. They are preferably water-miscible solvents, but solvents having only partial miscibility with water can also be used. As a rule, the solubility should be at least 50 g/l, preferably at least 100 g/l. Examples include aliphatic C4-C8 alcohols, preferably C4-C6 alcohols, which may be substituted with 1 to 5, preferably 1 to 3, ethyleneoxy units to achieve sufficient solubility in water. Additional examples include aliphatic diols having 2 to 8 carbon atoms, which may optionally also have additional substitution. For example, the co-solvent may be at least one selected from the group of 2-butanol, 2-methyl-1-propanol, butylethylene glycol, butyldiethylene glycol or butyltriethylene glycol.

The injection of the aqueous composition can be carried out using conventional devices. The composition can be injected into one or more injection wells using conventional pumps. Injection wells typically contain steel cemented pipes in place and the steel pipes are perforated at the desired point. The composition enters the oil formation from the injection well through the perforation. The pressure applied by the pumps, in a manner known in principle, is used to fix the flow rate of the composition and hence also the shear stress with which the aqueous composition enters the formation. The formation shear stress can be calculated by one skilled in the art in a manner known in principle based on the Hagen-Poiseuille law using the area through which the flow passes at the formation entry, the average pore radius and the volumetric flow rate. The average permeability of the formation can be found as described in a known manner. Naturally, the greater the volumetric flow rate of the aqueous polymer composition introduced into the formation, the greater the shear stress.

The injection rate can be fixed by one of ordinary skill in the art according to the conditions in the reservoir. Preferably, the shear rate upon entry of the aqueous polymer composition into the formation is at least 30,000 s ^-1 , preferably at least 60,000 s ^-1 and more preferably at least 90,000 s ^-1

According to one embodiment of the present invention, the method of the present invention is a waterflooding method that uses a base and typically a complexing agent or polyacrylate. This is usually the case when the proportion of polyvalent cations in the formation water is low (100-400 ppm). An exception is sodium metaborate, which can be used as a base in the presence of significant amounts of polyvalent cations even without a complexing agent.

The pH value of the aqueous composition is generally at least 8, preferably at least 9, especially 9 to 13, preferably 10 to 12 and for example 10.5 to 11.

In principle, any type of base that can achieve the desired pH can be used, and the person skilled in the art will make the appropriate choice. Examples of suitable bases include alkali metal hydroxides, eg NaOH or KOH, or alkali metal carbonates, eg Na ₂ CO ₃ . In addition, bases can be basic salts, for example alkali metal salts of carboxylic acids, phosphoric acid, or especially complexing agents containing acidic groups in base form, such as EDTANa ₄ .

The mineral oil usually also contains various carboxylic acids, such as naphthenic acids, which are converted to the corresponding salts by the base formulation. The salts act as natural surfactants and thus support the oil recovery process.

When complexing agents are used, it is preferable to prevent undesired precipitation of sparingly soluble salts, especially Ca and Mg salts, when the alkaline aqueous composition comes into contact with the appropriate metal ions and/or aqueous compositions for a process involving the corresponding salts. The amount of complexing agents is chosen by a person skilled in the art. For example, it can be from 0.1 to 4 wt. % based on the total amount of all components of the aqueous composition.

According to another preferred embodiment of the present invention, however, a crude oil recovery process is used in which a base (eg, alkali metal hydroxides or alkali metal carbonates) is not used.

The present invention is illustrated in more detail by means of the following examples.

Synthesis examples:

Preparation of anionic surfactants (A) and (B):

Abbreviations used:

EO ethyleneoxy

PO propyleneoxy

The following alcohols are used for synthesis:

1 a) allyl - 1.6 PO - 10 EO - CH ₂ CO ₂ Na

corresponds to the solubility enhancer (B) of general formula (II) R ⁴ -O-(CH ₂ C(CH ₃ )HO) _x (CH ₂ CH ₂ O) _y R ³ -Y ^- M ⁺ c R ⁴ =H ₂ C= CHCH ₂ , x=1.6, y=10, R ³ =CH ₂ , Y=CO ₂ and M=Na.

A 2 L pressure autoclave with an anchor stirrer was initially charged with 116 g (2.0 mol) of allyl alcohol and the stirrer was turned on. Thereafter, 2.37 g of potassium tert-butoxide (0.021 mol KOtBu) was added. The vessel was purged three times with N ₂ . After that, the vessel was checked for leaks, the pressure was brought to 0.5 bar (1.5 bar, absolute) and the vessel was heated to 120°C. At 150 rpm, 186 g (3.2 mol) of propylene oxide were dosed at 120° C. for 3 hours. The mixture was stirred at 130°C for 3 hours. 881 g (20 mol) of ethylene oxide were dosed at 120° C. for 24 hours. The mixture was allowed to react for another 1 hour, cooled to 80° C. and depressurized to 1.0 bar absolute. Nitrogen was bubbled through the solution for 15 minutes. After transferred at 80°C in an atmosphere of N ₂ . Analysis (mass spectrum, GPC, 1H NMR in CDCl ₃ , 1H NMR in MeOD) confirmed the average composition of CH ₂ =CH-CH ₂ O - 1.6 PO - 10 EO - H.

130 g (0.22 mol, 1.0 eq.) CH₂=CH-CH₂O 1.6 PO-10 EO-H and 35.3 g (0.297 mol, 1.35 eq.) of sodium salt of chloroacetic acid (purity 98%), and the mixture was stirred at 45°C for 15 minutes at 400 rpm at standard pressure. 2.0 g (0.05 mol, 0.227 eq.) of NaOH micropellets (diameter 0.5-1.5 mm) were introduced and a vacuum of 100 mbar was created for 30 min. After that, the following procedure was carried out six times: 1.645 g (0.0411 mol, 0.187 eq.) of NaOH micropellets (diameter 0.5-1.5 mm) were introduced, a vacuum of 100 mbar was used to remove reaction water, the mixture was stirred for 50 min and then the vacuum was broken with N₂. A total of 11.88 g (0.297 mol, 1.35 eq.) of NaOH micropellets was added. During the first hour of this period, the rotation speed was increased to about 1000 rpm. The mixture was then stirred at 45° C. and at 100 mbar for another 10 hours. The vacuum was broken with N₂, and the experiment was terminated (>95% yield).

A liquid that is white/yellowish and viscous at 20°C was obtained. The pH value (5% in water) was 8. The molar fraction of the sodium salt of chloroacetic acid is about 6 mol. %. The mole fraction of the sodium salt of glycolic acid is about 7 mol. %. The level of carboxymethylation is 80% according to ¹ H NMR ( ¹ HNMR with the addition of a shift reagent trichloroacetyl isocyanate). The content of the surfactant is 83 wt. percent.

1 b) C16C18-7 PO-10 EO-CH ₂ CO ₂ Na

Corresponds to the anionic surfactant (A) of general formula (I) R ¹ -O-(CH ₂ C(R ² )HO) _a -(CH ₂ C(CH ₃ )HO) _b -(CH ₂ CH ₂ O) _c -R ³ -Y ^- M ⁺ c R ¹ \u003d C ₁₆ H ₃₃ /C ₁₈ H ₃₇ , a \u003d 0, b \u003d 7, c \u003d 10, R ³ \u003d CH ₂ , Y \u003d CO ₂ and M \u003d Na.

An autoclave under pressure with a volume of 2 l with an anchor stirrer was initially loaded with 304 g (1.19 mol) of C16C18 alcohol, and the stirrer was turned on. After that, 4.13 g of a 50% KOH aqueous solution (0.037 mol KOH, 2.07 g KOH) was added, a vacuum of 25 mbar was created, and the mixture was heated to 100°C and maintained for 120 min to drive off water. The vessel was purged three times with N ₂ . Thereafter, the vessel was checked for leaks, the pressure was adjusted to 1.0 bar (2.0 bar absolute), the vessel was heated to 130° C., and then the pressure was adjusted to 2.0 bar absolute. At 150 rpm, 482 g (8.31 mol) of propylene oxide were dosed at 130° C. for 6 hours; p _max was 6.0 bar absolute. The mixture was stirred at 130°C for 10 hours; p _max was 5.0 bar absolute. The mixture was allowed to react for 1 hour until the pressure became constant, cooled to 100° C. and depressurized to 1.0 bar absolute. The vacuum was <10 mbar and the residual oxide was removed within 2 hours. The vacuum was broken with N ₂ and the product was transferred at 80° C. under N ₂ atmosphere. Analysis (mass spectrum, GPC, 1H NMR in CDCl ₃ , 1H NMR in MeOD) confirmed the average composition of C16C18-7PO-10EO-H.

165.3 g (0.150 mol, 1.0 eq.) C16C18 - 7 RO - 10 EO - H containing 0.005 mol mol, 1.35 eq) of sodium salt of chloroacetic acid (98% purity), and the mixture was stirred at 45°C at 400 rpm at standard pressure for 15 min. After that, the following procedure was carried out eight times: 1.02 g (0.0253 mol, 0.1688 equiv) of NaOH micropellets (diameter 0.5 - 1.5 mm) was introduced, a vacuum of 30 mbar was applied to remove reaction water, the mixture was stirred for 50 min, and then the vacuum was broken with N2 _. A total of 8.1 g (0.203 mol, 1.35 eq.) of NaOH micropellets was added over a period of about 6.5 hours. During the first hour of this period, the rotation speed was increased to about 1000 rpm. The mixture was then stirred at 45° C. and at 30 mbar for a further 3 hours. The vacuum was broken with N ₂ and the experiment was terminated (>95% yield).

A liquid that is white/yellowish and viscous at 20° C. was obtained. The pH value (5% in water) was 7.5. The water content was 1.5%.

The molar fraction of the sodium salt of chloroacetic acid is about 2 mol. %. The content of NaCl is about 6.0 wt. %. The OH number of the reaction mixture is 8.0 mg KOH/g. The molar fraction of the sodium salt of glycolic acid is about 3 mol. %. The level of carboxymethylation is 85%. 99 g of butyldiethylene glycol and 99 g of water were added. The content of surfactant is 45 wt. percent.

Application tests:

Determination of solubility

Surfactants were mixed (Example 3) and mixed with the appropriate salt composition at the appropriate concentration for testing in salt water at 20-30°C for 30 min (alternatively, the surfactant was dissolved in water, the pH was adjusted if required , up to a range of 6.5 to 8 by adding aqueous hydrochloric acid, and appropriate amounts of the corresponding salt were dissolved at 20°C). This was followed by incremental heating until cloudiness or phase separation occurred. This was followed by gentle cooling, and the point was noted at which the solution became clear or again slightly diffuse. This was recorded as cloud point.

At certain fixed temperatures, the appearance of a solution of surfactant in salt water has been noted. Clear solutions or solutions that disperse slightly and become slightly lighter again with slight shearing (but do not become creamy over time) are considered acceptable. These slightly scattering surfactant solutions are filtered through a filter with a pore size of 2 μm. Separation was not observed at all.

The indicated amounts of surfactant are indicated as wt. percentages of active substance (adjusted for 100% surfactant content).

Determination of surface tension at the interface

und kolloid-disperse Systeme" [Interfaces and Colloidally Disperse Systems], Springer Verlag Berlin Heidelberg 2002 - по следующей формуле издиаметра цилиндра d_z, скорости w, и дифференциальной плотностиThe interfacial tensions of crude oil versus salt water in the presence of a surfactant solution at temperature were determined by the spinning drop method using the SVT20 from DataPhysics. For this, a drop of oil was injected into a capillary filled with a saline solution of a surfactant at a temperature, and the expansion of the drop was observed at a speed of about 4500 rpm, and the change in surface tension at the interface with time was noted. The interfacial tension IFT (or s _ll ) was calculated in this case - as described by Hans-Dieter Dorfler in "

und kolloid-disperse Systeme" [Interfaces and Colloidally Disperse Systems], Springer Verlag Berlin Heidelberg 2002 - according to the following formula from cylinder diameter d _z , velocity w, and differential density

The indicated amounts of surfactant are indicated as wt. percentages of active substance (adjusted for 100% surfactant content).

API Gravity (American Petroleum Institute Gravity) is a standard unit of gravity commonly used in the US for crude oil. It is used throughout the world to characterize and as a quality standard for crude oil. API gravity is calculated from the relative density p _rel of crude oil at 60° F (15.56° C) based on water using

Density in degrees API=(141.5 / p _rel ) - 131.5.

Experimental results of solubility and interfacial tension after 0.75 to 7.5 hours are shown in Table 1.

As can be seen from Comparative Example C1 in Table 1, the anionic surfactant (A) gives the desired interfacial tensions of <0.1 mN/m at 50°C for a given high salinity. However, if the temperature is increased to 85° C. (comparative example C2) at the same salinity, the anionic surfactant (A) becomes insoluble and it is no longer possible to achieve low interfacial tensions. Surprisingly, a small addition of a solubility enhancer (B) to an anionic surfactant (A) at 85°C and a given high salinity achieves both surfactant solubility and desired interfacial tensions of <0.1 mN /m (example according to the invention 3). The slight addition is reflected in a ratio of solubility enhancer (B) to anionic surfactant (A) of 13:87 by weight or 15:85 by mole.

Claims (53)

1. A method for extracting crude oil from underground oil reservoirs, including at least the following steps: (1) providing an aqueous surfactant composition comprising water and a mixture of surfactants, (2) injecting said surfactant composition into the subterranean oil formation through at least one injection well, thereby reducing the tension at the crude oil-water interface to less than 0.1 mN/m, and (3) extracting crude oil from the reservoir through at least one production well, where the mixture of surfactants contains at least (A) a surfactant (A) having the general formula

and (B) a solubility enhancer (B) having the general formula

where R ¹ is a hydrocarbon fragment having from 8 to 36 carbon atoms, R ² is a hydrocarbon fragment having from 2 to 16 carbon atoms, R ³ is selected from the group: simple connection, alkylene group -(CH ₂ ) _o -, where o represents from 1 to 3, groups -CH ₂ -CH (OH) -CH ₂ -, R ⁴ is an allyl group H ₂ C=CH-CH ₂ -, Y ^- is an anionic group selected from -COO ^- or -SO ₃ ^- , M ⁺ is at least a cation selected from the group: H ⁺ , alkali metal ions, NH ₄ ⁺ and organic ammonium ions, a is a number from 0 to 69, b is a number from 3 to 70, c is a number from 0 to 50, x is a number from 1 to 69, y is a number from 0 to 50, and where R ³ , Y ^- and M ⁺ in (A) and (B) are identical, x<b, y=s and the molar ratio of surfactant (A)/solubility enhancer (B) is 98:2 to 60:40. 2. The method according to claim 1, where b is a number from 5 to 60. 3. The method according to claim 1 or 2, where x is a number from 1 to 44. 4. The method according to claim 1 or 2, where c is a number from 1 to 50 and y is a number from 1 to 50. 5. The method according to claim 1 or 2, where a is 0. 6. The method according to claim 1 or 2, where the sum of b and c is from 5 to 75. 7. The method according to p. 1 or 2, where R ¹ represents a hydrocarbon fragment having from 12 to 32 carbon atoms. 8. The method according to claim 1 or 2, where Y ^- represents a -COO ^- group and R ³ represents -(CH ₂ ) _o -, where o represents from 1 to 3, preferably 1. 9. The method according to claim 1 or 2, where Y ^- represents a -SO ₃ ^- group, and R ³ is selected from -(CH ₂ ) _o -, where o represents 2 or 3, and -CH ₂ -CH (OH )-CH ₂ -. 10. The method according to p. 1 or 2, where Y ^- represents a -SO ₃ ^- group and R ³ represents a single bond. 11. The method according to claim 1 or 2, wherein the molar ratio of surfactant (A)/solubility enhancer (B) is from 95:5 to 65:35. 12. The method of claim 1 or 2, wherein the aqueous surfactant composition further comprises salts. 13. The method of claim 1 or 2, wherein the method is Winsor type III microemulsion flooding. 14. Aqueous composition of surfactants, as defined in paragraph 1 or 2. 15. A method for producing a composition of surfactants according to claim 14, where in formula (I) and formula (II) a=0, c>0, y>0, including at least the following stages: (a) alkoxylation of the alcohol R ¹ OH with propylene oxide, thus obtaining R ¹ -O-(CH ₂ CH(CH ₃ )O) _b -H followed by alkoxylation of R ¹ -O-(CH ₂ CH(CH ₃ )O) _b -H with ethylene oxide, thus obtaining R ¹ -O-(CH ₂ CH(CH ₃ )O) _b -(CH ₂ CH ₂ O) _c H followed by the introduction of terminal anionic groups -R ³ Y ^- M ⁺ into R ¹ - O-(CH ₂ CH(CH ₃ )O) _b -(CH ₂ CH ₂ O) _c H, thereby obtaining a surfactant (A) having the general formula (I), wherein a=0, c>0 ; (b) alkoxylation of the alcohol R ⁴ OH with propylene oxide, thereby obtaining R ⁴ -O-(CH ₂ CH(CH ₃ )O) _x -H followed by alkoxylation of R ⁴ -O-(CH ₂ CH(CH ₃ )O) _x -H with ethylene oxide, thus obtaining R ⁴ -O-(CH ₂ CH(CH ₃ )O) _x -(CH ₂ CH ₂ O) _y H followed by the introduction of terminal anionic groups -R ³ Y ^- M ⁺ into R ⁴ - O-(CH ₂ CH(CH ₃ )O) _x -(CH ₂ CH ₂ O) _y H, thus obtaining a solubility enhancer (B) having the general formula (II), wherein y>0; (c) mixing (A) and (B); where R ¹ , R ² , R ³ , R ⁴ , Y ^- , M ⁺ , b, c, x and y have the meanings as defined in paragraph 14. 16. The method according to p. 15, where in stage (a) R ¹ -O- (CH ₂ CH (CH ₃ )O) _b - (CH ₂ CH ₂ O) _c H and in stage (b) R ⁴ -O -(CH ₂ CH(CH ₃ )O) _x -(CH ₂ CH ₂ O) _y H are reacted with an ω-halogenated carboxylic acid R ⁵ -(CH ₂ ) _o -COOH or a salt thereof, where R ⁵ is selected from F, Cl, Br or I, and o is from 1 to 3, preferably 1, thus obtaining a surfactant (A) having the general formula (I), wherein a=0, c>0, and a solubility enhancer (B) having the general formula (II), wherein y>0, and moreover, R ³ represents an alkylene group -(CH ₂ ) _o -, where o represents from 1 to 3, Y ^- represents an anionic group -COO ^- . 17. Use of the solubility enhancer (B) of the general formula R ⁴ -O-(CH ₂ CH(CH ₃ )O) _x -(CH ₂ CH ₂ O) _y -R ³ -Y ^- M ⁺ (II), as defined in paragraph 1 or 2, to enhance the solubility of the anionic surfactant (A) of general formula (I) R ¹ -O-(CH ₂ CH(R ² )O) _a -(CH ₂ CH(CH ₃ )O) _b -(CH ₂ CH ₂ O) _c - R ³ -Y ^- M ⁺ as defined in paragraph 1 or 2.