A surfactant for acid fracturing to improve oil recovery, and its preparation method and application

Abstract

The present application discloses a surfactant for acid fracturing to improve oil recovery, and a preparation method and application thereof, which belongs to the technical field of surfactants for fracturing. The preparation method comprises the following steps: (1) dissolving monomer A and functional monomer in a first solvent, polymerizing under the action of an initiator to obtain a solution containing a prepolymer; (2) adding monomer B to the prepolymer, polymerizing again, and separating to obtain the surfactant. When the surfactant is used in acid fracturing fluid, it can form stable reticular micelles, improve its shear resistance and temperature resistance in the acid fracturing fluid, reduce the residue in the formation, and improve the flowback rate and sand carrying capacity.

Description

Technical Field

[0001] The present application relates to a surfactant for acid fracturing to improve oil recovery, a preparation method and application thereof, and belongs to the technical field of surfactants for fracturing. Background Art

[0002] Acid fracturing fluid is used to exploit low permeability oil reservoirs. The dissolution effect of the acid fluid increases the crack wall surface, which is beneficial to the outflow of oil and gas, can significantly improve the oil recovery rate, and achieve increased production of the oil field.

[0003] The surfactants currently used in fracturing fluids include hydroxypropyl guar gum, alkyl polyoxyethylene ether, etc. The above catalysts can basically meet the requirements of on-site construction. However, they will form insoluble substances that remain in the formation after fracturing, which will not only reduce the permeability of the formation, but also affect the subsequent fracturing and exploitation, causing irreversible damage to the oil field. At the same time, the pressure fluid return rate using the above surfactants is low.

[0004] Patent CN113956863A discloses a viscoelastic surfactant for fracturing, which can form micelles in salt water. When used in fracturing operations in oil and gas fields, it can increase the flowback rate and reduce damage to the formation. However, this type of surfactant is only applicable to ordinary fracturing fluids. When it is added to acidified pressure fluids containing acid, the stability and temperature resistance of its micelles deteriorate. The micelle structure is easily destroyed during fracturing and remains on the surface of the formation, resulting in a significant decrease in the flowback rate and sand carrying capacity, making it difficult to meet construction applications. Summary of the invention

[0005] In order to solve the above problems, a surfactant for acid fracturing with improved recovery rate and a preparation method and application thereof are provided. When the surfactant is used in the acid fracturing fluid, it can form stable network micelles, improve its shear resistance and temperature resistance in the acid fracturing fluid, reduce the residue in the formation, and improve the return rate and sand carrying capacity.

[0006] According to one aspect of the present application, a surfactant for acid fracturing to enhance oil recovery is provided, wherein the molecular structure of the surfactant is shown in formula (1):

[0007] Formula (1),

[0008] wherein R2 and R3 are independently selected from one of a straight chain or branched chain alkyl group containing 1 to 3 carbon atoms, R4 is selected from one of a straight chain or branched chain alkyl group containing 2 to 5 carbon atoms, R5 and R6 are independently selected from one of a straight chain or branched chain alkyl group containing 2 to 5 carbon atoms or a straight chain or branched chain halogenated alkyl group containing 2 to 5 carbon atoms, R7 is selected from one of a straight chain or branched chain alkyl group containing 2 to 5 carbon atoms, x and y are independently selected from an integer between 10 and 30, z is selected from an integer between 5 and 20, and n is selected from an integer between 6 and 12;

[0009] The molecular structure of R1 is shown in formula (2):

[0010] Formula (2),

[0011] In formula (2), m is selected from 3 to 6.

[0012] The surfactant improves the viscoelastic surfactant of CN113956863A. By introducing the R1 segment on the straight chain, the surfactant can form a mesh structure micelle in the acid fracturing fluid. The stability and temperature resistance of the micelle in the acid fracturing fluid are significantly improved. Therefore, the acid pressure fluid containing the surfactant has improved shear resistance and sand carrying capacity during the acid fracturing process, thereby improving the flowback rate and recovery rate. In addition, the surfactant uses an amine oxide group to replace the original sulfonate or carboxylate. The amine oxide can promote the formation of mesh micelles and further improve the stability of the mesh micelles; second, it can be cationic in the acid fracturing fluid, improve the solubility in crude oil, thereby reducing the dissolution amount of the surfactant; third, it can improve the salt resistance, temperature resistance and acid resistance of the surfactant.

[0013] Optionally, R2 and R3 are both selected from methyl, R4 is selected from propyl, R5 and R6 are both selected from ethyl, and R7 is selected from propyl.

[0014] According to another aspect of the present application, there is provided a method for preparing the surfactant described in any one of the above items, comprising the following steps:

[0015] (1) dissolving monomer A and a functional monomer in a first solvent, and polymerizing them under the action of an initiator to obtain a solution containing a prepolymer;

[0016] (2) adding monomer B to the solution containing the prepolymer to undergo polymerization reaction again, and obtaining the surfactant after separation;

[0017] The molecular structure of the monomer A is shown in formula (3):

[0018] Formula (3);

[0019] The molecular structure of the monomer B is shown in formula (4):

[0020] Formula (4);

[0021] wherein R2 and R3 are independently selected from one of a C1-C3 alkyl group containing a straight chain or a branched chain, R4 is selected from one of a C2-C5 alkyl group containing a straight chain or a branched chain; R7 is selected from one of a C2-C5 alkyl group containing a straight chain or a branched chain; said R8 and R9 are independently selected from one of a C2-C5 alkenyl group containing a straight chain or a branched chain or a C2-C5 haloalkenyl group containing a straight chain or a branched chain, and n is selected from an integer between 6 and 12;

[0022] The functional monomer is selected from 1,4-bis-[4-(3-acryloxypropoxy)benzoyloxy]-2-methylbenzene and / or 1,4-bis-[4-(6-acryloxyhexyloxy)benzoyloxy]-2-methylbenzene.

[0023] In the above reaction, monomer A is first reacted with a functional monomer to obtain a prepolymer, and then the prepolymer is reacted with monomer B to obtain a surfactant with R1 as an intermediate segment. This preparation method is conducive to introducing the functional monomer between monomer A and monomer B, so that the R1 segment can play the above role, and the length of the main chain of the surfactant and the distance between the monomer A segment and the monomer B segment can be regulated by the R1 segment, thereby regulating the volume of the network micelles to obtain micelles with moderate volume and strong shear resistance.

[0024] The functional monomer contains more alkyl groups, benzene ring structures, ester groups and ether groups. The alkyl groups can adjust the chain length of the surfactant, thereby improving the mechanical adaptability of the micelles formed by the surfactant and ensuring that the micelles are not easily deformed during the fracturing process. The benzene ring can improve the shear resistance and acid resistance of the surfactant, so that the micelles formed by the surfactant can exist stably in the acid fracturing fluid. The ester group and ether group can play a role in anti-static adsorption, and are similar to the carbonyl and ester groups of monomers A and B. They can improve the density of the formed micelles, improve the resistance of the micelles to acid, and further improve the stability of the surfactant.

[0025] In addition, the current fracturing fluids configured with surfactants are generally configured while being used. If too much is configured, the stability of the micelles in the fracturing fluid will also deteriorate as the pressure fluid is placed for a longer time, so the fracturing effect deteriorates, resulting in the fracturing fluid being unable to continue to be used. After the surfactant prepared by the functional monomer used in the present application is configured with the acidified fracturing fluid, it can be placed at room temperature for a long time, extending the use time of the acidified fracturing fluid. Therefore, more acidified fracturing fluid can be pre-configured for use before fracturing, and even if it is not used up, it can be left for the next fracturing or other oil field exploitation, thereby improving the fracturing efficiency while also avoiding the waste of fracturing fluid.

[0026] Optionally, the reaction temperature of step (1) is 70-90°C and the reaction time is 3-4h.

[0027] Optionally, the reaction temperature of step (2) is 60-100° C., and the reaction time is 2-4 h.

[0028] Optionally, the weight ratio of the monomer A, the functional monomer and the monomer B is (0.45-1.10):(0.35-0.65):1.

[0029] The dosage of the above monomers can ensure the stability, temperature resistance and compactness of the network structure micelles formed by the surfactant, and improve the viscosity of the acid fracturing fluid and the sand carrying capacity of the acid fracturing fluid.

[0030] Optionally, the functional monomer is selected from 1,4-bis-[4-(3-acryloxypropoxy)benzoyloxy]-2-methylbenzene and 1,4-bis-[4-(6-acryloxyhexyloxy)benzoyloxy]-2-methylbenzene in a weight ratio of 1:2.

[0031] The ratio of the functional monomers can maximize the effect of the functional monomers, and can also further improve the stability of the acid fracturing fluid prepared by the surfactant at room temperature, thereby extending the use time of the acid fracturing fluid.

[0032] Optionally, nitrogen is introduced into the reactions of step (1) and step (2) for protection.

[0033] Optionally, the first solvent used in step (1) is at least one selected from hexane, benzene, toluene, xylene, dichloromethane, ether and acetone.

[0034] Optionally, the initiator is at least one of an azo initiator, a persulfate initiator and a peroxide initiator.

[0035] Optionally, the amount of the initiator used is 1-2 wt % of the amount of the monomer A used.

[0036] Optionally, the monomer A is obtained by reacting reactant A and reactant B in a second solvent, the reactant A is hydrogen peroxide, and the molecular structure of reactant B is shown in formula (5):

[0037] Formula (5).

[0038] Optionally, the weight ratio of reactant A to reactant B is (20-25):1.

[0039] Optionally, the reaction temperature of the reactant A and the reactant B is 60-70° C., and the reaction time is 3-6 h.

[0040] Optionally, the second solvent is at least one of ethanol, isopropanol and acetone.

[0041] Optionally, the concentration of hydrogen peroxide in the hydrogen peroxide is 30%.

[0042] Optionally, nitrogen gas is introduced during the reaction of reactant A and reactant B for protection.

[0043] Optionally, the reactant B is obtained by reacting reactant C and reactant D in a third solvent under ice bath, wherein the molecular structure of the reactant C is shown in formula (6):

[0044] Formula (6);

[0045] The molecular structure of reactant D is shown in formula (7):

[0046] Formula (7).

[0047] Optionally, the weight ratio of reactant C to reactant D is (0.33-0.65):1.

[0048] Optionally, the third solvent is at least one of dichloromethane, tetrahydrofuran and pyridine.

[0049] Optionally, nitrogen gas is introduced during the reaction of reactant C and reactant D for protection.

[0050] According to another aspect of the present application, there is provided use of any of the surfactants described above or a surfactant prepared by any of the preparation methods described above in oil and gas field exploitation.

[0051] The beneficial effects of this application include but are not limited to:

[0052] 1. The surfactant for acid fracturing of the present application can form stable micelles in the acid fracturing fluid, and the structure is not easily destroyed during the acid fracturing process, which significantly improves the temperature resistance of the acid fracturing fluid. In addition, the micelles formed by the surfactant are not easy to remain, and the damage to the formation is small, which can meet the requirements of construction use.

[0053] 2. The surfactant for acid fracturing of the present application can reduce its dosage in the acid fracturing fluid and reduce the cost of acid fracturing due to its high properties in various aspects, and can still improve the recovery rate of oil and gas fields and increase the production of oil fields even when used in a small amount.

[0054] 3. The surfactant for acid fracturing of the present application can significantly reduce its surface tension, increase the water contact angle, reduce capillary force, and improve the return efficiency of the injected fluid, thereby improving the recovery rate of oil and gas fields by adding a very small amount of the surfactant to the acid fracturing fluid.

[0055] 4. When the acid fracturing surfactant of the present application is used to prepare an acid fracturing fluid, the acid fracturing fluid has excellent fracturing performance and does not require the addition of a debonding agent. It can automatically debond when encountering crude oil, so there is no residue after fracturing and the flowback rate is high. DETAILED DESCRIPTION

[0056] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0057] Unless otherwise specified, the raw materials in the examples and comparative examples of the present application were purchased through commercial channels.

[0058] Unless otherwise specified, the methods used in the examples and comparative examples of the present application are conventional methods in the prior art.

[0059] In the examples of the present application, infrared spectroscopy analysis of the surfactant was performed using a Fourier transform infrared spectrometer, and the obtained surfactant was tested and analyzed at room temperature using an attenuated total reflection mode.

[0060] Example 1 Surfactant 1#

[0061] The molecular structure of surfactant 1# is:

[0062] ,

[0063] Among them, R1 is , R2 and R3 are both methyl, R4 is n-propyl, R5 and R6 are both ethyl, R7 is n-propyl, x is 12, y is 12, z is 8, n is 8, and m is 3.

[0064] The synthetic route of surfactant 1# is:

[0065]

[0066] .

[0067] Pre-synthesize monomer A:

[0068] S1: Dissolve 100.0g of reactant D in 450.0g of pyridine, add reactant C dropwise in an ice bath, add 45.0g in total, react for 3h under N2 protection to synthesize reactant B;

[0069] S2: Dissolve 10.0 g of reactant B in 500.0 g of isopropanol, raise the temperature to 60°C while stirring, add 30% hydrogen peroxide solution, a total of 200.0 g, and react at a constant temperature for 6 hours under N2 protection to synthesize monomer A.

[0070] The preparation method of surfactant 1# is:

[0071] (1) 11.0 g of monomer A and 6.5 g of 1,4-bis-[4-(3-acryloxypropoxy)benzoyloxy]-2-methylbenzene were mixed and dissolved in a mixed solution of 250.0 g of n-hexane and toluene (the weight ratio of n-hexane to toluene was 1:1). Under N2 protection, 0.22 g of azobisisobutyronitrile was added and reacted at 70°C for 4 h to obtain a solution containing a prepolymer;

[0072] (2) 10.0 g of monomer B was added to the solution containing the prepolymer, and the polymerization reaction was carried out again at 60° C. for 4 h. Surfactant 1# was obtained after column chromatography separation.

[0073] Example 2 Surfactant 2#

[0074] The difference between this embodiment and embodiment 1 is that in the molecular structure of surfactant 2#, m of R1 is 6, R2 and R3 are both n-propyl, R4 is n-pentyl, R5 and R6 are both ethyl, R7 is n-pentyl, and the other conditions are the same as surfactant 1#.

[0075] Example 3 Surfactant 3#

[0076] The difference between this embodiment and embodiment 1 is that the reaction temperature of step (1) is 90°C and the reaction time is 4 hours, the reaction time of step (2) is 100°C and the reaction time is 2 hours, and the other conditions are the same as those of surfactant 1#.

[0077] Example 4 Surfactant 4#

[0078] The difference between this embodiment and embodiment 1 is that the weight ratio of monomer A, functional monomer and monomer B is 0.45:0.35:1, and the other conditions are the same as surfactant 1#.

[0079] Example 5 Surfactant 5#

[0080] The difference between this embodiment and embodiment 1 is that in step S2 of synthesizing monomer A, the amount of hydrogen peroxide added is 150.0 g, and the other conditions are the same as those of surfactant 1#.

[0081] Example 6 Surfactant 6#

[0082] The difference between this embodiment and embodiment 1 is that in step S2 of synthesizing monomer A, the reaction is carried out at a constant temperature of 40° C. for 4 hours, and the other conditions are the same as those of surfactant 1#.

[0083] Comparative Example 1 Comparative Surfactant D1#

[0084] The molecular structure formula of the comparative surfactant D1# is:

[0085] ,

[0086] Among them, R1 is n-propyl, R2 and R3 are both methyl, R4 is n-propyl, R5 and R6 are both ethyl, R7 is n-propyl, x is 12, y is 12, and n is 8.

[0087] The synthetic route of the comparative surfactant D1# is:

[0088] .

[0089] The preparation method of the comparative surfactant D1# is:

[0090] (1) Dissolve 100.0 g of reactant D in 450.0 g of pyridine, add reactant C dropwise in an ice bath, add a total of 45.0 g, and react for 3 h under N2 protection to synthesize reactant B;

[0091] (2) Dissolve 100.0 g of reactant B in 500.0 g of isopropanol, raise the temperature to 90°C while stirring, add reactant A dropwise, 45.0 g in total, and react at a constant temperature for 4 h under N2 protection to synthesize monomer A;

[0092] (3) 38.0 g of monomer A and 100.0 g of monomer B were mixed and dissolved in 475.0 g of n-hexane. Under N2 protection, 5.0 g of azobisisobutyronitrile was added and reacted at 80°C for 3 h. Comparative surfactant D1# was obtained after column chromatography separation.

[0093] Comparative Example 2 Preparation of Comparative Surfactant D2#

[0094] The molecular structure formula of the comparative surfactant D2# is:

[0095] ,

[0096] Among them, R2 and R3 are both methyl, R4 is n-propyl, R5 and R6 are both ethyl, R7 is n-propyl, x is 12, y is 12, and n is 8.

[0097] The synthetic route of the comparative surfactant D2# is:

[0098]

[0099] .

[0100] The pre-synthesized monomer A in the comparative surfactant D2# is the same as that in Example 1, except that:

[0101] (1) 11.0 g of monomer A and 10.0 g of monomer B were mixed and dissolved in 250.0 g of a mixed solution of n-hexane and toluene (the weight ratio of n-hexane to toluene was 1:1). Under N2 protection, 0.22 g of azobisisobutyronitrile was added and reacted at 60°C for 4 h. Comparative surfactant D2# was obtained after column chromatography separation.

[0102] Comparative Example 3 Preparation of Comparative Surfactant D3#

[0103] The molecular structure formula of the comparative surfactant D3# is:

[0104] ,

[0105] Among them, R1, R2, R3, R4, R5, R6, R7, x, y, z, n, and m are all the same as those in Example 1.

[0106] The synthetic route of surfactant 1# is:

[0107]

[0108] .

[0109] Pre-synthesize monomer A:

[0110] S1: Dissolve 100.0g of reactant D in 450.0g of pyridine, add reactant C dropwise in an ice bath, add 45.0g in total, react for 3h under N2 protection to synthesize reactant B;

[0111] S2: Dissolve 100.0 g of reactant B in 500.0 g of isopropanol, raise the temperature to 90°C while stirring, add reactant A dropwise, a total of 45.0 g, and react at a constant temperature for 4 hours under N2 protection to synthesize monomer A.

[0112] The preparation method of the comparative surfactant D3# is:

[0113] (1) 11.0 g of monomer A and 6.5 g of 1,4-bis-[4-(3-acryloxypropoxy)benzoyloxy]-2-methylbenzene were mixed and dissolved in a mixed solution of 250.0 g of n-hexane and toluene (the weight ratio of n-hexane to toluene was 1:1). Under N2 protection, 0.22 g of azobisisobutyronitrile was added and reacted at 70°C for 4 h to obtain a solution containing a prepolymer;

[0114] (2) 10.0 g of monomer B was added to the solution containing the prepolymer, and the polymerization reaction was carried out again at 60° C. for 4 h. After column chromatography separation, a comparative surfactant D3# was obtained.

[0115] Test Example 1

[0116] By weight, 0.5 parts of the surfactants prepared in the examples and comparative examples were added to a mixture of 100 parts of water, 0.3 parts of citric acid, 0.5 parts of hydroxymethyl cellulose, 25 parts of hydrofluoric acid, 3 parts of sodium salicylate and 0.5 parts of sodium thiosulfate to obtain an acidified fracturing fluid.

[0117] The apparent viscosity, heat and shear resistance, viscosity of the debonding fluid, the residue content after debonding, the sand suspension capacity, and the damage performance of the fracturing fluid prepared in each embodiment or comparative example were tested. The test results are shown in Table 1. The test method is as follows:

[0118] 1. Apparent viscosity: Use a rheometer at 25°C, 170s -1 The viscosity after 1 min of shear rate testing.

[0119] 2. Heat and shear resistance: Use a rheometer at 150°C, 170s -1 The viscosity of the fracturing fluid after shearing for 120 minutes was tested at a shear rate of .

[0120] 3. Viscosity of the breaking fluid: Crude oil was used as a breaker to test the breaking performance, that is, a certain amount of breaker was added to the fracturing fluid at room temperature (the mass ratio of fracturing fluid to breaker was 1:0.001), and the breaking state was observed. When the fracturing fluid recovered to a free-flowing state, the breaking was considered complete. The viscosity of the fracturing fluid after breaking was tested, and the results are shown in Table 1.

[0121] 4. Residue content after gel breaking: Take 50mL (V0) of fracturing fluid after gel breaking in a centrifuge tube, centrifuge at 3000r / min for 30min, pour out the supernatant, inject 50mL of distilled water, centrifuge at 3000r / min for 20min, pour out the supernatant, and dry the centrifuge tube (105℃) to obtain the residue mass m1. The residue content is x=m1 / V0×1000.

[0122] 5. Sand suspension capacity: Take 20.0g of proppant (20-40 mesh ceramsite proppant) at room temperature and add it to 100.0g of fracturing fluid. After stirring evenly, pour it into a measuring cylinder and measure the time it takes for the proppant to settle to the bottom of the measuring cylinder.

[0123] 6. Damage performance: The experiment was conducted using the tight sandstone gas layer of the Shaximiao Formation in southwestern Sichuan. The permeability of the fracturing fluid prepared with the surfactants of the above embodiments and comparative examples before and after passing through the core was tested, and the damage rate of the fracturing fluid to the core permeability was calculated. The calculation formula for the damage rate is: [(permeability before fracturing - permeability after fracturing) / permeability before fracturing] * 100%.

[0124] Table 1

[0125]

[0126] Test Example 2

[0127] The surfactants of Example 1 and Comparative Examples 1-3 were prepared into fracturing fluids, and the recovery rate of the surfactants was verified by construction. The results are shown in Table 2. The specific test method is as follows:

[0128] First, add 0.5 parts of surfactant, 0.3 parts of citric acid, 3 parts of sodium salicylate and 0.5 parts of sodium thiosulfate to 100 parts of water and stir evenly, then add 0.5 parts of hydroxymethyl cellulose and stir evenly to form a thickened fracturing fluid for use. When in use, the thickened fracturing fluid is injected into the production layer of the oil well in the heavy oil production test of a certain oil field using a high-pressure device to create cracks. Then, 25 parts of hydrofluoric acid are added to the cracks to dissolve the cracks to prevent the cracks from closing after the high pressure is removed, and finally the oil recovery rate of the above acidified fracturing fluid is calculated.

[0129] Table 2

[0130]

[0131] The above is only the embodiment of the present application, and the protection scope of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the technical ideas and principles of the present application should be included in the protection scope of the present application.

Claims

1. A surfactant for acid fracturing to enhance oil recovery, characterized in that: The preparation method of the surfactant comprises the following steps: (1) dissolving monomer A and a functional monomer in a first solvent, and polymerizing them under the action of an initiator to obtain a solution containing a prepolymer; (2) adding monomer B to the solution containing the prepolymer to polymerize again, and obtaining the surfactant after separation, wherein the weight ratio of the monomer A, the functional monomer and the monomer B is (0.45-1.10): (0.35-0.65): 1; The molecular structure of the monomer A is shown in formula (3): Formula (3); The molecular structure of the monomer B is shown in formula (4): Formula (4); wherein R2 and R3 are independently selected from one of a C1-C3 alkyl group containing a straight chain or a branched chain, R4 is selected from one of a C2-C5 alkylene group containing a straight chain or a branched chain; R7 is selected from one of a C2-C5 alkylene group containing a straight chain or a branched chain; said R8 and R9 are independently selected from one of a C2-C5 alkenyl group containing a straight chain or a branched chain or a C2-C5 haloalkenyl group containing a straight chain or a branched chain, and n is selected from an integer between 6 and 12; The functional monomer is selected from 1,4-bis-[4-(3-acryloxypropoxy)benzoyloxy]-2-methylbenzene and / or 1,4-bis-[4-(6-acryloxyhexyloxy)benzoyloxy]-2-methylbenzene.

2. The surfactant for acid fracturing for improving oil recovery according to claim 1, characterized in that: The reaction temperature of step (1) is 70-90°C and the reaction time is 3-4h.

3. The surfactant for acid fracturing for improving oil recovery according to claim 1, characterized in that: The reaction temperature of step (2) is 60-100°C and the reaction time is 2-4h.

4. The surfactant for acid fracturing for improving oil recovery according to claim 1, characterized in that: The monomer A is obtained by reacting reactant A and reactant B in a second solvent, wherein reactant A is hydrogen peroxide, and the molecular structure of reactant B is shown in formula (5): Formula (5).

5. The surfactant for acid fracturing for improving oil recovery according to claim 4, characterized in that: The weight ratio of reactant A to reactant B is (20-25):

1.

6. The surfactant for acid fracturing for improving oil recovery according to claim 4, characterized in that: The reaction temperature of the reactant A and the reactant B is 60-70° C., and the reaction time is 3-6 hours.

7. Use of the surfactant according to any one of claims 1 to 6 in oil and gas field exploitation.

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