Low-tension foaming agent as well as preparation method and application thereof

Abstract

The invention relates to a low-tension foaming agent as well as a preparation method and application thereof. The preparation method comprises the following steps: (1) dissolving fatty alcohol and maleic anhydride in an organic solvent under the protection of nitrogen or inert gas, uniformly mixing, adding anhydrous sodium acetate, reacting to obtain a reaction solution, and performing first post-treatment to obtain fatty alcohol monomaleate; (2) under the protection of nitrogen or inert gas, adding dihydroxybenzidine into fatty alcohol maleic acid monoester, adding p-toluenesulfonic acid into the fatty alcohol maleic acid monoester, reacting to obtain a reaction solution, and performing second post-treatment to obtain a gemini intermediate product; and (3) adjusting the pH value of the gemini intermediate product, adding a sodium hydrogen sulfite aqueous solution into the gemini intermediate product to obtain a mixed solution, carrying out a reaction to obtain a reaction solution, and carrying out third post-treatment to obtain the low-tension foaming agent. The method has the following beneficial effects: (1) the adsorption loss in a reservoir is small, and deep migration can be realized; (2) efficient foaming and plugging can be realized under the conditions of low concentration and low power in the deep part of the stratum; and (3) the viscosity-reducing and oil-washing agent has good viscosity-reducing and oil-washing effects.

Description

Technical Field

[0001] The present invention belongs to the field of heavy oil exploitation, and particularly relates to a low-tension foaming agent, a preparation method thereof, and uses thereof. Background Art

[0002] In China, the heavy oil resources are rich in reserves. The annual output of heavy oil is high in Shengli Oilfield, Xinjiang Oilfield, Daqing Oilfield and other places, which is an important part of increasing reserves and production. Steam stimulation is an important development method for heavy oil reservoirs. Chinese Patent Application CN113250666A discloses a method for exploiting a shallow heavy oil reservoir by assisted steam stimulation with in-situ combustion. The method for exploiting the shallow heavy oil reservoir by assisted steam stimulation with in-situ combustion includes the following steps: establishing a group steam stimulation well pattern for in-situ combustion assisted steam stimulation, which includes a plurality of in-situ combustion assisted steam stimulation units. Each in-situ combustion assisted steam stimulation unit includes an in-situ combustion stimulation area arranged at the central position and a steam stimulation area arranged around the in-situ combustion stimulation area; a plurality of in-situ combustion stimulation vertical wells are arranged in the in-situ combustion stimulation area; a plurality of steam stimulation vertical wells are arranged in the steam stimulation area; all the plurality of in-situ combustion stimulation vertical wells perform in-situ combustion stimulation, and at the same time, all the plurality of steam stimulation vertical wells perform steam stimulation; after repeating 2 to 3 rounds, all the plurality of in-situ combustion stimulation vertical wells are converted into continuous in-situ combustion injection wells, and all the plurality of steam stimulation vertical wells continue to perform steam stimulation. However, after years of development, the old thermal recovery areas have entered the high-round steam stimulation development period. With the continuous increase of the development time and the number of steam injection rounds, the steam development effect of the steam stimulation wells has further deteriorated.

[0003] In recent years, the thermal composite chemical stimulation technology with foam as the core has been increasingly valued. For example, Chinese Patent Application CN114370259A discloses a thermal composite stimulation efficiency enhancement system for offshore low-production heavy oil cold production wells, including a wellhead production tree, an electric pump production string, a hot water injection pipeline, a mud tank, a chemical agent tank and a nitrogen generation device. One end of the hot water injection pipeline is connected to the tubing wing valve and the other end is connected to the platform hot water; the mud tank stores a composite efficiency enhancement agent A, and the mud tank is connected to the hot water injection pipeline through an agent injection pipeline A; the chemical agent tank stores a composite efficiency enhancement agent B, and the chemical agent tank is connected to the hot water injection pipeline through an agent injection pipeline B; the nitrogen generation device is connected to the casing wing valve through a nitrogen injection pipeline. The present invention also discloses an operation method of the above system: injecting hot water, the composite efficiency enhancement agent A, the composite efficiency enhancement agent B and nitrogen into the oil reservoir through the crude oil cold production production string, and after the injection is completed, shutting in the well for a period of time and then starting the pump for production. Foam has unique oil washing and profile control properties. On the one hand, it can selectively block the high-permeability zones, effectively adjust the steam absorption profile, inhibit steam channeling, etc., so as to expand the steam sweep; on the other hand, the foaming agent itself is a chemical agent with high interfacial activity, which can effectively reduce the oil-water interfacial tension, then strip and emulsify the crude oil, improve the crude oil flow ability at the steam front, and expand the oil drainage radius.

[0004] Conventional foaming agents are mainly traditional single-chain sulfonates, carboxylates, non-ionic surfactants, etc. For example, Chinese Patent Application CN112300769A discloses a temperature-resistant foam flooding agent, its preparation method and application, belonging to the field of tertiary oil recovery technology. The method includes: adding olefins to a reactor, heating to a first reference temperature, adding naphthalene and concentrated sulfuric acid, refluxing for 2 - 6 hours, cooling to a second reference temperature and continuing the reaction for 12 - 36 hours, adding a pH regulator to adjust the pH value to 9 - 10, and drying to obtain a foaming agent; mixing 0.1 - 0.6% by mass of the foaming agent, 0.01 - 0.05% by mass of a foam stabilizer and the balance of water evenly to obtain a foam flooding agent. However, the sulfonate foaming agent of this invention has a single-chain structure, and only contains one sulfonic acid group in its molecular structure. The formed foam flooding agent has a resistance factor of 32.11 at 120°C, with insufficient plugging strength and is difficult to be used in multi-round huff and puff heavy oil reservoirs. That is, conventional foaming agents have loose molecular arrangements at the gas-liquid interface and oil-water interface. Therefore, they have low plugging strength in reservoirs with strong heterogeneity, and poor oil washing and viscosity reduction effects in the low-concentration area at the steam front, that is, in the range of 40 - 60 m from the wellbore, and it is difficult to meet the requirements of multi-round huff and puff heavy oil reservoirs. Summary of the Invention

[0005] Object of the Invention: Aiming at the above technical problems, the present invention provides a low-tension foaming agent, its preparation method and use. This low-tension foaming agent has high surface activity, strong foaming ability, high plugging strength, and at the same time can achieve ultra-low interfacial tension, strong oil washing and viscosity reduction ability, can realize the integration of oil washing and profile control, effectively improve steam sweep, expand the drainage radius, and achieve quality improvement and efficiency increase in multi-round huff and puff.

[0006] Technical Solution: A low-tension foaming agent having the structure of formula (1):

[0007]

[0008] Wherein: R is a straight-chain aliphatic hydrocarbon group with C8 - C24, preferably a straight-chain aliphatic hydrocarbon group with C12 - C18;

[0009] M is one of an alkali metal, an alkaline earth metal or an ammonium group, preferably one of K, Na, ammonium.

[0010] The preparation method of the above low-tension foaming agent, in terms of mole parts, comprises the following steps:

[0011] (1) Under the protection of nitrogen or inert gas, dissolve 1 part of fatty alcohol and 1 to 1.2 parts of maleic anhydride in an appropriate amount of organic solvent, mix evenly, then add an appropriate amount of anhydrous sodium acetate thereto, react at 70 to 110°C for at least 1 h to obtain a reaction solution, and then perform a first post-treatment on the reaction solution to obtain fatty alcohol maleic monoester;

[0012] (2) Under the protection of nitrogen or inert gas, add 2 to 2.4 parts of dihydroxybenzidine to the fatty alcohol maleic acid monoester obtained in step (1), and add an appropriate amount of p-toluenesulfonic acid thereto. React at 110 to 150 °C for at least 2 h to obtain a reaction solution, and then obtain a gemini intermediate after subjecting the reaction solution to a second post-treatment;

[0013] (3) Use an alkali solution to adjust the pH value of the gemini intermediate to 6.5 to 7.5, and then slowly add an aqueous solution of sodium bisulfite thereto to obtain a mixed solution. React the mixed solution at 80 to 160 °C for at least 5 h to obtain a reaction solution, and then obtain a low-tension foaming agent after subjecting the reaction solution to a third post-treatment.

[0014] Further, the fatty alcohol described in step (1) is a straight-chain fatty alcohol having 8 to 24 carbon atoms, preferably a straight-chain fatty alcohol having 12 to 18 carbon atoms.

[0015] Further, the organic solvent described in step (1) is one of acetone, tetrahydrofuran, ethyl acetate, and diethyl ether.

[0016] Further, the volume ratio of the amount of the organic solvent used in step (1) to the volume of the fatty alcohol is (20 - 40):1, preferably (25 - 35):1.

[0017] Further, the mass ratio of the amount of anhydrous sodium acetate used in step (1) to the amount of the fatty alcohol used is (0.2 - 1):100, preferably (0.4 - 0.6):100.

[0018] Further, the reaction time in step (1) is 1 - 6 h;

[0019] The reaction time of the reaction in step (2) is 2 - 6 h;

[0020] The reaction time of the reaction in step (3) is 5 - 10 h.

[0021] Further, the specific steps of the first post-treatment in step (1) are: rotary evaporate the reaction solution and then recrystallize.

[0022] Further, the mass ratio of the amount of p-toluenesulfonic acid used in step (2) to the amount of the fatty alcohol maleic acid monoester used is (1 - 2):100, preferably (1.4 - 1.6):100.

[0023] Further, the specific steps of the second post-treatment in step (2) are: extract the reaction solution with ethyl acetate and then rotary evaporate.

[0024] Further, the solute of the alkali solution described in step (3) is at least one of alkali metal hydroxides and alkaline earth metal hydroxides, preferably sodium hydroxide and / or potassium hydroxide.

[0025] Further, the mass fraction of the aqueous sodium bisulfite solution is 20 - 40%.

[0026] Further, in step (3), the pH value of the gemini intermediate is adjusted to 6.5 to 7.5 using the alkali solution.

[0027] Further, in the mixed solution of step (3), the molar ratio of sodium bisulfite to the gemini intermediate is (4 - 5):1.

[0028] Further, the specific steps of the third post-treatment in step (3) are as follows:

[0029] The reaction solution is put into distilled water for extraction, the insoluble substances are removed by filtration, the filtrate is collected, rotary evaporated and recrystallized, and then the crystals are collected, washed with absolute ethanol and rotary evaporated.

[0030] Further, the structure of the fatty alcohol maleic acid monoester described in step (1) is shown in formula (2):

[0031]

[0032] Among them, R is a straight-chain aliphatic hydrocarbon group with 8 - 24 carbon atoms, preferably a straight-chain aliphatic hydrocarbon group with 12 - 18 carbon atoms.

[0033] Further, the structure of the gemini intermediate described in step (2) is shown in formula (3):

[0034]

[0035] Among them, R is a straight-chain aliphatic hydrocarbon group with 8 - 24 carbon atoms, preferably a straight-chain aliphatic hydrocarbon group with 12 - 18 carbon atoms.

[0036] A low-tension foaming agent is prepared by the above preparation method.

[0037] Application of the low-tension foaming agent described in any one of the above as an integrated oil washing and profile control agent during steam stimulation in heavy oil reservoirs.

[0038] Further, the specific steps of the application are as follows:

[0039] In the case of pre-injection or co-injection with steam, the low-tension foaming agent described in any one of the above is dissolved in an appropriate amount of water to form a low-tension foaming agent solution with a mass concentration of 0.1% - 1.5%, and then the low-tension foaming agent solution and gas are simultaneously injected into the formation from the wellbore in an appropriate ratio to achieve the integration of oil washing and profile control.

[0040] Further, the gas is at least one of nitrogen, air, CO 2 , and flue gas.

[0041] Further, the volume ratio of the low-tension foaming agent solution to the gas is 1:(0.6 - 4).

[0042] The low-tension foaming agent of the present invention is a gemini sulfonate surfactant-type foaming agent, which has a gemini structure and contains multiple active sulfonic acid groups. The surfactant molecules are closely arranged at the gas-liquid interface and the oil-water interface. The cmc is 28 mg / L, and it has high surface activity. It can quickly form small and uniform bubbles under high-temperature conditions, with strong foaming and foam-stabilizing abilities. It can efficiently foam and plug at low concentrations and low driving forces in the deep formation. At the same time, it can form an ultra-low interfacial tension of 0.001 - 0.01 mN / m with formation crude oil, has a good effect of washing oil and reducing viscosity, can reduce the fluidity of crude oil at the steam front, expand the oil drainage radius, and improve the thermal recovery huff and puff effect.

[0043] Beneficial effects: A low-tension foaming agent and its preparation method and use disclosed by the present invention have the following beneficial effects:

[0044] (1) The low-tension foaming agent of the present invention has small adsorption loss in the reservoir and can migrate deep.

[0045] (2) The low-tension foaming agent of the present invention can efficiently foam and plug at low concentrations and low driving forces in the deep formation. At a temperature of 200 °C and a use concentration of 0.1%, the foaming volume > 200 mL, and the resistance factor > 120.

[0046] (3) The low-tension foaming agent of the present invention has a good viscosity reduction and oil washing effect. For ordinary heavy oil (crude oil viscosity range at 50 °C is 50 - 10000 mPa·s) and extra-heavy oil (crude oil viscosity range at 50 °C is 10000 - 50000 mPa·s), the viscosity reduction rate of heavy oil can reach more than 98%, and the static oil washing rate can reach more than 40%. Description of the Drawings

[0047] Figure 1 It is a flow chart of the preparation method of the low-tension foaming agent disclosed by the present invention. Detailed Embodiments

[0048] The following combines specific embodiments and further describes the present invention in detail with reference to data. It should be understood that these embodiments are only for illustrating the present invention and do not limit the scope of the present invention in any way.

[0049] The reaction equation for preparing the low-tension foaming agent is as follows:

[0050] ①

[0051]

[0052] ②

[0053]

[0054]

[0055] Example 1

[0056] A low-tension foaming agent Q1 having the structure of formula (1):

[0057]

[0058] Wherein: R is a straight-chain alkyl group of C12 (lauryl);

[0059] M is Na.

[0060] The preparation method of the above low-tension foaming agent Q1 is as follows in terms of mole parts:

[0061] (1) Under nitrogen protection, 1 part of lauryl alcohol and 1 part of maleic anhydride are dissolved in an appropriate amount of organic solvent. After mixing evenly, an appropriate amount of anhydrous sodium acetate is added thereto, and the reaction is carried out at 90 °C for 3 h to obtain a reaction solution. Then, the reaction solution is subjected to a first post-treatment to obtain lauryl alcohol maleic monoester;

[0062] (2) Under nitrogen protection, 2.2 parts of dihydroxybenzidine are added to the lauryl alcohol maleic monoester obtained in step (1), and an appropriate amount of p-toluenesulfonic acid is added thereto. The reaction is carried out at 140 °C for 5 h to obtain a reaction solution. Then, the reaction solution is subjected to a second post-treatment to obtain a gemini intermediate;

[0063] (3) The pH value of the gemini intermediate is adjusted to 7 using an alkali solution, and then an aqueous solution of sodium bisulfite is slowly added thereto to obtain a mixed solution. The mixed solution is reacted at 120 °C for 8 h to obtain a reaction solution. Then, the reaction solution is subjected to a third post-treatment to obtain the low-tension foaming agent Q1.

[0064] Further, the organic solvent in step (1) is acetone.

[0065] Further, the volume ratio of the amount of the organic solvent used in step (1) to the volume of the lauryl alcohol is 30:1.

[0066] Further, the mass ratio of the amount of the anhydrous sodium acetate used in step (1) to the amount of the lauryl alcohol used is 0.5:100.

[0067] Further, the specific steps of the first post-treatment in step (1) are as follows: rotary evaporate the reaction solution and then perform recrystallization.

[0068] Further, the mass ratio of the dosage of p-toluenesulfonic acid to the dosage of lauryl maleate in step (2) is 1.5:100.

[0069] Further, the specific steps of the second post-treatment in step (2) are as follows: extract the reaction solution with ethyl acetate and then perform rotary evaporation.

[0070] Further, the solute of the alkali solution in step (3) is sodium hydroxide.

[0071] Further, the mass fraction of the aqueous sodium bisulfite solution is 30%.

[0072] Further, the molar ratio of sodium bisulfite to the gemini intermediate in the mixed solution of step (3) is 4.5:1.

[0073] Further, the specific steps of the third post-treatment in step (3) are as follows:

[0074] Put the reaction solution into distilled water for extraction, filter to remove insoluble substances, collect the filtrate, perform rotary evaporation and recrystallization, then collect the crystals, wash them with absolute ethanol and perform rotary evaporation.

[0075] Further, the structure of lauryl maleate described in step (1) is shown in formula (2):

[0076]

[0077] Among them, R is a straight-chain aliphatic hydrocarbon group with 12 carbon atoms (lauryl group).

[0078] Further, the structure of the gemini intermediate described in step (2) is shown in formula (3):

[0079]

[0080] Among them, R is a straight-chain aliphatic hydrocarbon group with 12 carbon atoms (lauryl group).

[0081] A low-tension foaming agent is prepared by the above preparation method.

[0082] Application of the low-tension foaming agent Q1 described in any one of the above as an integrated oil washing and profile control agent during steam stimulation in heavy oil reservoirs.

[0083] Further, the specific steps of the application are as follows:

[0084] In the case of pre-injection, dissolve the low-tension foaming agent Q1 described in any one of the above in an appropriate amount of water to form a low-tension foaming agent Q1 solution with a mass concentration of 0.1%, and then simultaneously inject the low-tension foaming agent Q1 solution and gas into the formation from the wellbore in an appropriate ratio to achieve the integration of oil washing and profile control.

[0085] Further, the gas is nitrogen.

[0086] Further, the volume ratio of the low-tension foaming agent Q1 solution to the gas is 1:2.

[0087] Example 2

[0088] A low-tension foaming agent Q2 has the structure of formula (1):

[0089]

[0090] Wherein: R is a straight-chain aliphatic hydrocarbon group of C24;

[0091] M is K.

[0092] The preparation method of the above low-tension foaming agent Q2 is as follows in terms of mole parts:

[0093] (1) Under the protection of argon gas, dissolve 1 part of tetracosanol and 1.2 parts of maleic anhydride in an appropriate amount of organic solvent, mix evenly, then add an appropriate amount of anhydrous sodium acetate thereto, react at 110 °C for 1 h to obtain a reaction solution, and then perform the first post-treatment on the reaction solution to obtain tetracosanol maleic monoester;

[0094] (2) Under the protection of argon gas, add 2.4 parts of dihydroxybenzidine to the tetracosanol maleic monoester obtained in step (1), and add an appropriate amount of p-toluenesulfonic acid thereto, react at 150 °C for 2 h to obtain a reaction solution, and then perform the second post-treatment on the reaction solution to obtain a gemini intermediate;

[0095] (3) Use an alkali solution to adjust the pH value of the gemini intermediate to 7.5, then slowly add an aqueous solution of sodium bisulfite thereto to obtain a mixed solution, react the mixed solution at 160 °C for 5 h to obtain a reaction solution, and then perform the third post-treatment on the reaction solution to obtain the low-tension foaming agent.

[0096] Further, the tetracosanol in step (1) is a straight-chain fatty alcohol of C24.

[0097] Further, the organic solvent in step (1) is tetrahydrofuran.

[0098] Further, the volume ratio of the amount of the organic solvent used in step (1) to the volume of the tetracosanol is 40:1. In another embodiment, the volume ratio of the amount of the organic solvent used to the volume of the tetracosanol is 35:1.

[0099] Further, the mass ratio of the amount of the anhydrous sodium acetate used in step (1) to the amount of the tetracosanol used is 1:100. In another embodiment, the mass ratio of the amount of the anhydrous sodium acetate used to the amount of the tetracosanol used is 0.6:100.

[0100] Further, the specific steps of the first post-treatment in step (1) are as follows: rotary evaporate the reaction solution, and then perform recrystallization.

[0101] Further, the mass ratio of the amount of the p-toluenesulfonic acid used in step (2) to the amount of the monomaleate of tetracosanol used is 2:100. In another embodiment, the mass ratio of the amount of the p-toluenesulfonic acid used to the amount of the monomaleate of tetracosanol used in step (2) is 1.6:100.

[0102] Further, the specific steps of the second post-treatment in step (2) are as follows: extract the reaction solution with ethyl acetate, and then perform rotary evaporation.

[0103] Further, the solute of the alkali solution in step (3) is potassium hydroxide.

[0104] Further, the mass fraction of the aqueous sodium bisulfite solution is 40%.

[0105] Further, the molar ratio of the sodium bisulfite to the gemini intermediate in the mixed solution of step (3) is 5:1.

[0106] Further, the specific steps of the third post-treatment in step (3) are as follows:

[0107] Put the reaction solution into distilled water for extraction, filter to remove insoluble substances, collect the filtrate, perform rotary evaporation and recrystallization, then collect the crystals, wash them with absolute ethanol, and perform rotary evaporation.

[0108] Further, the structure of the monomaleate of tetracosanol described in step (1) is shown in formula (2):

[0109]

[0110] Among them, R is a straight-chain aliphatic hydrocarbon group of C24.

[0111] Further, the structure of the gemini intermediate described in step (2) is shown in formula (3):

[0112]

[0113] Among them, R is a straight-chain aliphatic hydrocarbon group of C24.

[0114] A low-tension foaming agent is prepared by the above preparation method.

[0115] Application of the low-tension foaming agent described in any one of the above as an integrated oil washing and profile control agent during steam stimulation in heavy oil reservoirs.

[0116] Further, the specific steps of the application are as follows:

[0117] In the case of being injected along with steam, dissolve the low-tension foaming agent Q2 described in any one of the above in an appropriate amount of water to form a low-tension foaming agent solution with a mass concentration of 1.5%, and then inject the low-tension foaming agent Q2 solution and gas into the formation from the wellbore simultaneously in an appropriate ratio to achieve the integration of oil washing and profile control.

[0118] Further, the gas is air.

[0119] Further, the volume ratio of the low-tension foaming agent Q2 solution to the gas is 1:4.

[0120] Example 3

[0121] A low-tension foaming agent Q3 has the structure of formula (1):

[0122]

[0123] Among them: R is a straight-chain aliphatic hydrocarbon group of C8;

[0124] M is ammonium.

[0125] In another embodiment, the low-tension foaming agent is substantially the same as the low-tension foaming agent Q3, and the only difference is that: M is K and Na.

[0126] The preparation method of the above low-tension foaming agent Q3 is as follows in terms of mole parts:

[0127] (1) Under the protection of a neon atmosphere, dissolve 1 part of n-octanol and 1.1 parts of maleic anhydride in an appropriate amount of organic solvent, mix evenly, then add an appropriate amount of anhydrous sodium acetate thereto, and react at 70 °C for 6 h to obtain a reaction solution, and then perform a first post-treatment on the reaction solution to obtain n-octanol maleic monoester;

[0128] (2) Under the protection of a neon atmosphere, add 2 parts of dihydroxybenzidine to the n-octanol maleic monoester obtained in step (1), and add an appropriate amount of p-toluenesulfonic acid thereto, and react at 110 °C for 6 h to obtain a reaction solution, and then perform a second post-treatment on the reaction solution to obtain a gemini intermediate;

[0129] (3) Adjust the pH value of the gemini intermediate to 6.5 with an alkali solution, then slowly add an aqueous solution of sodium bisulfite thereto to obtain a mixed solution. React the mixed solution at 80 °C for 10 h to obtain a reaction solution, and then obtain the low-tension foaming agent Q3 after the third post-treatment of the reaction solution.

[0130] Further, the n-octanol described in step (1) is a straight-chain fatty alcohol of C8.

[0131] Further, the organic solvent described in step (1) is ethyl acetate.

[0132] Further, the volume ratio of the amount of the organic solvent used to the volume of the n-octanol in step (1) is 20:1. In another embodiment, the volume ratio of the amount of the organic solvent used to the volume of the n-octanol in step (1) is 25:1.

[0133] Further, the mass ratio of the amount of anhydrous sodium acetate used to the amount of n-octanol used in step (1) is 0.2:100. In another embodiment, the mass ratio of the amount of anhydrous sodium acetate used to the amount of n-octanol used in step (1) is 0.4:100.

[0134] Further, the specific steps of the first post-treatment in step (1) are: rotary evaporate the reaction solution, and then perform recrystallization.

[0135] Further, the mass ratio of the amount of p-toluenesulfonic acid used to the amount of monooctyl maleate in step (2) is 1:100. In another embodiment, the mass ratio of the amount of p-toluenesulfonic acid used to the amount of monooctyl maleate in step (2) is 1.4:100.

[0136] Further, the specific steps of the second post-treatment in step (2) are: extract the reaction solution with ethyl acetate, and then perform rotary evaporation.

[0137] Further, the alkali solution in step (3) is ammonia water.

[0138] In another embodiment, the solute of the alkali solution in step (3) is sodium hydroxide and potassium hydroxide in an equal mass ratio.

[0139] Further, the mass fraction of the aqueous sodium bisulfite solution is 20%.

[0140] Further, the molar ratio of sodium bisulfite to the gemini intermediate in the mixed solution of step (3) is 4:1.

[0141] Further, the specific steps of the third post-treatment in step (3) are as follows:

[0142] The reaction solution is put into distilled water for extraction, and insoluble substances are removed by filtration. The filtrate is collected, rotary evaporated and recrystallized, and then the crystals are collected, washed with absolute ethanol and rotary evaporated.

[0143] Further, the structure of the octyl maleate monoester described in step (1) is shown in formula (2):

[0144]

[0145] Among them, R is a straight-chain aliphatic hydrocarbon group with C8.

[0146] Further, the structure of the gemini intermediate described in step (2) is shown in formula (3):

[0147]

[0148] Among them, R is a straight-chain aliphatic hydrocarbon group with C8.

[0149] A low-tension foaming agent is prepared by the above preparation method.

[0150] Application of the low-tension foaming agent Q3 described in any one of the above as an integrated oil washing and profile control agent during steam stimulation in heavy oil reservoirs.

[0151] Further, the specific steps of the application are as follows:

[0152] In the case of pre-injection, the low-tension foaming agent Q3 described in any one of the above is dissolved in an appropriate amount of water to form a low-tension foaming agent Q3 solution with a mass concentration of 1%, and then the low-tension foaming agent Q3 solution and gas are simultaneously injected into the formation from the wellbore in an appropriate proportion to achieve the integration of oil washing and profile control.

[0153] Further, the gas is CO 2 .

[0154] Further, the volume ratio of the low-tension foaming agent Q3 solution to the gas is 1:0.6.

[0155] Example 4

[0156] A low-tension foaming agent Q4 has the structure of formula (1):

[0157]

[0158] Among them: R is a straight-chain aliphatic hydrocarbon group with C18;

[0159] M is Mg.

[0160] In another embodiment, the low-tension foaming agent has substantially the same structure as the low-tension foaming agent Q4, with the only difference being that M is Be.

[0161] In another embodiment, the low-tension foaming agent has substantially the same structure as the low-tension foaming agent Q4, with the only difference being that M is Ca.

[0162] The preparation method of the above-mentioned low-tension foaming agent Q4 is as follows in terms of mole parts:

[0163] (1) Under the protection of helium gas, dissolve 1 part of n-octadecanol and 1.1 parts of maleic anhydride in an appropriate amount of organic solvent. After mixing evenly, add an appropriate amount of anhydrous sodium acetate thereto, and react at 85 °C for 4 h to obtain a reaction solution. Then, subject the reaction solution to a first post-treatment to obtain n-octadecanol maleic acid monoester;

[0164] (2) Under the protection of helium gas, add 2.3 parts of dihydroxybenzidine to the n-octadecanol maleic acid monoester obtained in step (1), and add an appropriate amount of p-toluenesulfonic acid thereto. React at 135 °C for 4 h to obtain a reaction solution. Then, subject the reaction solution to a second post-treatment to obtain a gemini intermediate;

[0165] (3) Use an alkali solution to adjust the pH value of the gemini intermediate to 7, and then slowly add an aqueous sodium bisulfite solution thereto to obtain a mixed solution. React the mixed solution at 100 °C for 8 h to obtain a reaction solution. Then, subject the reaction solution to a third post-treatment to obtain the low-tension foaming agent Q4.

[0166] Further, the n-octadecanol described in step (1) is a straight-chain fatty alcohol of C18.

[0167] Further, the organic solvent described in step (1) is diethyl ether.

[0168] Further, the volume ratio of the amount of the organic solvent used in step (1) to the volume of the n-octadecanol is 35:1.

[0169] Further, the mass ratio of the amount of the anhydrous sodium acetate used in step (1) to the amount of the n-octadecanol used is 0.6:100.

[0170] Further, the specific steps of the first post-treatment in step (1) are: rotary evaporate the reaction solution and then recrystallize.

[0171] Further, the mass ratio of the amount of the p-toluenesulfonic acid used in step (2) to the amount of the n-octadecanol maleic acid monoester used is 1.5:100.

[0172] Further, the specific steps of the second post-treatment in step (2) are as follows: extracting the reaction solution with ethyl acetate and then performing rotary evaporation.

[0173] Further, the solute of the alkali solution in step (3) is magnesium hydroxide.

[0174] In another embodiment, the solute of the alkali solution in step (3) is beryllium hydroxide.

[0175] In another embodiment, the solute of the alkali solution in step (3) is calcium hydroxide.

[0176] Further, the mass fraction of the aqueous sodium bisulfite solution is 35%.

[0177] Further, the molar ratio of sodium bisulfite to the gemini intermediate in the mixed solution of step (3) is 4.2:1.

[0178] Further, the specific steps of the third post-treatment in step (3) are as follows:

[0179] Putting the reaction solution into distilled water for extraction, filtering to remove insoluble substances, collecting the filtrate, performing rotary evaporation and recrystallization, then collecting the crystals, washing them with absolute ethanol, and performing rotary evaporation.

[0180] Further, the structure of the octadecyl maleate in step (1) is shown in formula (2):

[0181]

[0182] Among them, R is a straight-chain aliphatic hydrocarbon group with 18 carbon atoms.

[0183] Further, the structure of the gemini intermediate in step (2) is shown in formula (3):

[0184]

[0185] Among them, R is a straight-chain aliphatic hydrocarbon group with 18 carbon atoms.

[0186] A low-tension foaming agent is prepared by the above preparation method.

[0187] Application of the low-tension foaming agent Q4 described in any one of the above as an integrated oil washing and profile control agent during steam stimulation in heavy oil reservoirs.

[0188] Further, the specific steps of the application are as follows:

[0189] In the case of pre-injection, dissolve the low-tension foaming agent Q4 described in any one of the above in an appropriate amount of water to form a low-tension foaming agent Q4 solution with a mass concentration of 0.3%, and then inject the low-tension foaming agent Q4 solution and gas into the formation from the wellbore at an appropriate ratio simultaneously to achieve the integration of oil washing and profile control.

[0190] Furthermore, the gas is flue gas.

[0191] Furthermore, the volume ratio of the low-tension foaming agent Q4 solution to the gas is 1:3.

[0192] Performance evaluation

[0193] In a certain block R of Shengli Oilfield, the reservoir temperature is 55°C. The oil used in this experiment is an oil sample from this block, with the viscosity of the surface degassed crude oil being 12852 mPa·s and the density being 0.8974 g / cm 3 , and the emulsified water cut is 23.9%.

[0194] The water used in this experiment is a water sample from this block, with the total salinity being 21152 mg / L, among which the Ca 2+ content is 2086 mg / L and the Mg 2+ content is 443 mg / L.

[0195] Use the low-tension foaming agents Q1, Q2, Q3, and Q4 prepared in Examples 1-4 respectively, and compare with the commercially available foaming agents FT-1 and FT-2 to evaluate the foaming volume, foam half-life, resistance factor, viscosity reduction rate, and oil washing rate of the formed nitrogen foam. The use concentration of the foaming agent is 0.1%. The results are shown in Table 1, where:

[0196] The test methods for foaming volume, foam half-life, and resistance factor refer to Q / SH10202052-2010 "Foaming Agents for Conventional Foam Flooding". The experimental temperature is 200°C.

[0197] The test method for oil washing rate refers to Q / SH10202191-2018 "Technical Requirements for Surfactants for Oil Displacement". The experimental temperature is 55°C.

[0198] The evaluation method for viscosity reduction rate refers to Q / SH 10201519-2016 "General Standard for Viscosity Reducing Agents for Heavy Oil". The experimental temperature is 55°C.

[0199] Table 1 Performance test results

[0200]

[0201]

[0202] From the above evaluation results, it can be seen that the low-tension foaming agents Q1, Q2, Q3, and Q4 of the present invention have strong foaming and stabilizing properties at a temperature of 200 °C and a use concentration of 0.1%. Their foaming volumes are all greater than 230 mL, and their foam half-lives all reach more than 170 s. However, the foaming volumes of the commercially available foaming agents FT-1 and FT-2 are <190 mL, and their foam half-lives are <150 s, which are significantly lower than those of the present invention.

[0203] The resistance factors of the low-tension foaming agents Q1, Q2, Q3, and Q4 of the present invention all reach above 130, and Q2 reaches a maximum of 147. However, the resistance factors of the commercially available foaming agents FT-1 and FT-2 are both less than 100, which are significantly lower than those of the present invention. The plugging strength of the foaming agents of the present invention is higher.

[0204] The viscosity reduction rates of the low-tension foaming agents Q1, Q2, Q3, and Q4 of the present invention all reach above 99%, and the oil washing rates all reach above 58%. However, the viscosity reduction rates of the commercially available foaming agents FT-1 and FT-2 are both less than 96%, and the oil washing rates are both less than 45%, which are significantly lower than those of the present invention.

[0205] The low-tension foaming agents Q1, Q2, Q3, and Q4 of the present invention all meet the relevant requirements of the oilfield. Compared with the comprehensive performance of commercially available foaming agents, they are excellent and can meet the development needs of multi-round steam stimulation heavy oil reservoirs.

[0206] The above has made a detailed description of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A low tension foaming agent, characterized in that: It has the structure of formula (1): Wherein: R is a C8-C24 straight chain aliphatic hydrocarbon group, preferably a C12-C18 straight chain aliphatic hydrocarbon group; M is one of alkali metals, alkaline earth metals or ammonium groups, preferably one of K, Na and ammonium.

2. The method for preparing the low tension foaming agent according to claim 1, characterized in that: In terms of molar parts, the steps are as follows: (1) Under the protection of nitrogen or inert gas, 1 part of fatty alcohol and 1 to 1.2 parts of maleic anhydride are dissolved in an appropriate amount of organic solvent, mixed evenly, and then an appropriate amount of anhydrous sodium acetate is added thereto, reacted at 70 to 110° C. for at least 1 hour to obtain a reaction solution, and then the reaction solution is subjected to a first post-treatment to obtain a fatty alcohol maleic acid monoester; (2) under the protection of nitrogen or inert gas, adding 2 to 2.4 parts of dihydroxybenzidine to the fatty alcohol maleic acid monoester obtained in step (1), adding an appropriate amount of p-toluenesulfonic acid thereto, reacting at 110 to 150° C. for at least 2 hours to obtain a reaction solution, and then subjecting the reaction solution to a second post-treatment to obtain a gemini intermediate product; (3) Using an alkaline solution, the pH value of the gemini intermediate product is adjusted to 6.5 to 7.5, and then slowly adding a sodium bisulfite aqueous solution thereto to obtain a mixed solution, reacting the mixed solution at 80 to 160° C. for at least 5 hours to obtain a reaction solution, and then subjecting the reaction solution to a third post-treatment to obtain a low-tension foaming agent.

3. The method for preparing a low tension foaming agent according to claim 2, characterized in that: The fatty alcohol described in step (1) is a C8-C24 straight-chain fatty alcohol, preferably a C12-C18 straight-chain fatty alcohol.

4. The method for preparing a low tension foaming agent according to claim 2, characterized in that: The organic solvent described in step (1) is one of acetone, tetrahydrofuran, ethyl acetate and ether.

5. The method for preparing a low tension foaming agent according to claim 2, characterized in that: The ratio of the volume of the organic solvent used in step (1) to the volume of the fatty alcohol is (20-40):1, preferably (25-35):1; The mass ratio of the amount of anhydrous sodium acetate used in step (1) to the amount of the fatty alcohol used is (0.2-1):100, preferably (0.4-0.6):

100.

6. The method for preparing a low tension foaming agent according to claim 2, characterized in that: The reaction time in step (1) is 1-6h; The reaction time of the reaction in step (2) is 2-6h; The reaction time of the reaction in step (3) is 5-10h.

7. The method for preparing a low tension foaming agent according to claim 2, characterized in that: The specific steps of the first post-treatment in step (1) are: rotary evaporating the reaction solution and then recrystallizing it; The specific steps of the second post-treatment in step (2) are: extracting the reaction solution with ethyl acetate and then rotary evaporating.

8. The method for preparing a low tension foaming agent according to claim 2, characterized in that: The mass ratio of the amount of p-toluenesulfonic acid used in step (2) to the amount of the fatty alcohol maleic acid monoester used is (1-2):100, preferably (1.4-1.6):

100.

9. The method for preparing a low tension foaming agent according to claim 2, characterized in that: The solute of the alkaline solution in step (3) is at least one of an alkali metal hydroxide and an alkaline earth metal hydroxide, preferably sodium hydroxide and / or potassium hydroxide.

10. The method for preparing a low tension foaming agent according to claim 2, characterized in that: The mass fraction of the sodium bisulfite aqueous solution is 20-40%.

11. The method for preparing a low tension foaming agent according to claim 2, characterized in that: The molar ratio of the sodium bisulfite to the gemini intermediate product in the mixed solution of step (3) is (4-5):

1.

12. The method for preparing a low tension foaming agent according to claim 2, characterized in that: The specific steps of the third post-treatment in step (3) are as follows: The reaction solution is put into distilled water for extraction, the insoluble matter is removed by filtration, the filtrate is collected, rotary evaporated, recrystallized, and then the crystals are collected and washed with anhydrous ethanol and rotary evaporated.

13. The method for preparing a low tension foaming agent according to claim 2, characterized in that: The structure of the fatty alcohol maleic acid monoester described in step (1) is shown in formula (2): Wherein, R is a C8-C24 straight chain aliphatic hydrocarbon group, preferably a C12-C18 straight chain aliphatic hydrocarbon group.

14. The method for preparing a low tension foaming agent according to claim 2, characterized in that: The structure of the gemini intermediate product described in step (2) is shown in formula (3): Wherein, R is a C8-C24 straight chain aliphatic hydrocarbon group, preferably a C12-C18 straight chain aliphatic hydrocarbon group.

15. A low tension foaming agent, characterized in that: Prepared by the preparation method according to any one of claims 2 to 14.

16. Use of the low tension foaming agent according to claim 1 or 15 as an integrated oil washing and profile control agent in a steam stimulation process of a heavy oil reservoir.

17. The use according to claim 16, characterized in that The specific steps of the application are as follows: In the case of pre-injection or injection with steam, the low-tension foam agent described in any of the above items is dissolved in a suitable amount of water to form a low-tension foam agent solution with a mass concentration of 0.1%-1.5%, and then the low-tension foam agent solution and gas are simultaneously injected into the formation from the wellbore in an appropriate proportion to achieve integrated oil washing and profile control.

18. The use according to claim 17, characterized in that The gas is at least one of nitrogen, air, CO2 and flue gas.

19. The use according to claim 17, characterized in that The volume ratio of the low tension foaming agent solution to the gas is 1:(0.6-4).

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