A foaming agent for oil fields and a method for preparing the same

Abstract

The application discloses an oil field foaming agent and a preparation method thereof, and belongs to the technical field of oil and gas field chemical agent preparation. The foaming agent is a sodium salt of phthalic acid monoamide polyoxyethylene ether, wherein phthalic anhydride and ethanolamine are used to synthesize phthalic acid monoethanolamide, the phthalic acid monoethanolamide is reacted with ethylene oxide to obtain phthalic acid monoamide polyoxyethylene ether, and the phthalic acid monoamide polyoxyethylene ether is neutralized by using a NaOH aqueous solution to obtain the sodium salt. Compared with conventional foaming agents in oil fields, the foaming agent significantly improves foaming and foam stability performance of the foaming agent, reduces oil-water interfacial tension, and especially under high-temperature and high-salinity conditions, the gas bubbles still have high oil meeting stability.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field chemical agent preparation technology, specifically relating to an oilfield foaming agent and its preparation method. Background Technology

[0002] Currently, polymer flooding and binary flooding are relatively mature tertiary oil recovery technologies, but they face the problem of a shortage of high-quality tertiary oil recovery resources. Foam flooding, due to its good plugging performance and selectivity for oil and water, is considered a promising tertiary oil recovery method.

[0003] Foam flooding, as a chemical flooding technology for enhancing oil recovery, has been widely researched and applied both domestically and internationally. In the mid-to-late 20th century, the United States, Canada, the United Kingdom, and Norway conducted laboratory experiments on foam flooding and air foam flooding, and carried out field trials in the Higgins, Knybob South, North Sea, and Snorre oil fields in Illinois, achieving good results. Domestic research on air foam flooding began in the 1970s at the Shengli Oilfield, followed by field trials in the Baise, Ziyin, and Zhongyuan oilfields, all achieving good results.

[0004] In oil and gas field development, factors affecting fluid flow in reservoirs include the pore structure of the reservoir sandstone, oil / water interfacial tension, oil / gas surface tension, and system wettability. Among these, the oil / water interfacial tension is considered a crucial factor. An oil-water interfacial tension in the range of 0.1 mN / m to 0.001 mN / m is considered low interfacial tension, while a tension below 0.001 mN / m is considered ultra-low interfacial tension. It is generally believed that only by reducing the oil-water interfacial tension to the ultra-low interfacial tension zone can the residual crude oil in the reservoir strata deform and flow, thereby improving oil recovery. Foaming agents play a vital role in oil and gas field development and oil and gas well enhancement measures. Currently used foaming agents such as ABS, SDS, and BK6A used in the foam flooding system of the Ganguyi block all suffer from insufficient bubble volume and poor stability, inability to achieve ultra-low interfacial tension at the oil-water interface, instability upon contact with oil, and ineffectiveness under high salinity and high temperature conditions. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a foaming agent for oil fields and its preparation method, so as to solve the technical problems of existing foaming agents having insufficient bubble volume and poor stability, inability to achieve ultra-low interfacial tension at the oil-water interface, instability when encountering oil, and poor performance under high salinity and high temperature conditions.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention discloses a method for preparing a foaming agent for oil fields, comprising the following steps:

[0008] S1: After mixing the solvent, phthalic anhydride and catalyst A, a mixed solution is obtained. Ethanolamine is added dropwise to the mixed solution to carry out the reaction. After removing the unreacted solvent and ethanolamine, white-yellow phthalic acid monoethanolamide is obtained.

[0009] S2: Mix white and yellow phthalic acid monoethanolamide and catalyst B and place them in a reaction vessel. Vacuum the vessel until no water is distilled out. Then, ethylene oxide is introduced to react and phthalic acid monoethanolamide polyoxyethylene ether is obtained.

[0010] S3: Phthalic acid monoamide polyoxyethylene ether is added to sodium hydroxide solution and reacted fully to obtain a foaming agent for oil fields.

[0011] Further, in S1, the solvent, phthalic anhydride and catalyst are mixed to obtain a mixed solution. After the mixed solution is heated to 80-120℃ in an oil bath, ethanolamine is added dropwise to the mixed solution at a rate of 1d / (2-5)s to react for 4-8h. After cooling to room temperature, the unreacted solvent and ethanolamine are removed to obtain white-yellow phthalic acid monoethanolamide.

[0012] Further, the amount of solvent used is 3-4 times the mass of phthalic anhydride; the amount of ethanolamine used is 0.9-1.2 equivalents of phthalic anhydride; and the amount of catalyst A used is 0.1% equivalent of phthalic anhydride.

[0013] Further, the solvent is one or more of dichloromethane, trichloromethane, dichloroethane, cyclohexane, and toluene; the catalyst A is a condensing agent dicyclohexylcarbodiimide, diisopropylcarbodiimide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, or 4-N,N-dimethylpyridine.

[0014] Further, the catalyst B is KOH; the amount of catalyst B used is 0.3%-0.4% of the mass of phthalic acid monoethanolamide.

[0015] Further, the reaction vessel is a reaction kettle; the mixture of white yellow phthalic acid monoethanolamide and catalyst B is placed into the reaction kettle, then the reaction kettle is closed, the reaction kettle is evacuated and nitrogen gas is introduced to remove air; the temperature of the reaction kettle is raised to 80-90℃, and the vacuum is evacuated again for 40-60 minutes until no water is distilled out.

[0016] Further, the temperature of the reactor is raised to 140-180℃, and then ethylene oxide is introduced to carry out the reaction until the pressure of the reaction vessel no longer decreases, to obtain phthalic acid monoethanolamide polyoxyethylene ether; the molar ratio of the white yellow phthalic acid monoethanolamide to ethylene oxide is 1:(7-12).

[0017] Further, the mass concentration of the sodium hydroxide solution is 0.3-0.5%; the heating temperature is 40-60℃; the reaction time is 1-4h; and the mass ratio of the phthalic acid monoamide polyoxyethylene ether to the sodium hydroxide solution is (25-30):(80-100).

[0018] The present invention also discloses a foaming agent for oilfields prepared by the above preparation method.

[0019] Furthermore, the chemical formula for the oilfield foaming agent is:

[0020]

[0021] Where n is 7-12.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] This invention discloses a method for preparing a foaming agent for oilfields. The method involves reacting phthalic anhydride with ethanolamine via an amidation reaction, followed by reaction with ethylene oxide to introduce a polyoxyethylene ether segment, resulting in phthalic acid monoamide polyoxyethylene ether. Since commonly used foaming agents are generally alkyl anionic, amamidopropyl betaine-based, or contain benzenesulfonyl surfactants, their foaming performance is generally poor. This invention synthesizes a substance containing phenyl, amide, and polyoxyethylene ether groups. The resulting oilfield foaming agent significantly improves the foaming and foam-stabilizing properties of the foaming agent, reduces the oil-water interfacial tension, and exhibits high oil-contaminated stability, especially under high temperature and high salinity conditions.

[0024] This invention also discloses an oilfield foaming agent obtained by the above preparation method. Due to its good foaming performance and stability, it can be used under high temperature and high salinity conditions. It has good foaming performance and the bubbles still have high oil stability, and has broad application prospects. Detailed Implementation

[0025] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0026] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0027] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0028] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0029] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0030] This invention provides a foaming agent for oilfields and its preparation method, specifically including the following steps:

[0031] S1. A four-necked flask is equipped with an oil bath, a stirring device, a thermometer, a condenser, and a dropping funnel. Solvent is placed in the four-necked flask, and a certain amount of phthalic anhydride and catalyst are added to the solvent. The reaction flask is protected with N2. The oil bath is heated to 80-120℃. 0.9-1.2 equivalents of ethanolamine are added dropwise to the reaction flask at a rate of 1d / 2-5s. After the addition is complete, the reaction continues for 4-8 hours. During this time, the amine value of the reaction liquid remains unchanged. The temperature is lowered, and the solvent and unreacted ethanolamine are removed by rotation to obtain white-yellow phthalic acid monoethanolamide.

[0032] S2. Add the phthalic acid monoethanolamide obtained in S1 to the reactor, and simultaneously add catalyst at 0.2%-0.5% of the mass of phthalic acid monoethanolamide. Then close the reactor, evacuate the reaction system, and purge with nitrogen to remove air. Repeat this process 3-5 times to ensure the oxygen content in the reaction system is at an extremely low level. Next, raise the temperature to 80-90℃, evacuate again for dehydration, and continue for 40-60 minutes until no water is distilled off. Afterward, raise the temperature to 140-180℃, and introduce ethylene oxide at a ratio of n(phthalic acid monoethanolamide):n(ethylene oxide) = 1:7-12 until the pressure in the reaction system no longer decreases. A light yellow paste is obtained, which is phthalic acid monoethanolamide polyoxyethylene ether.

[0033] S3. Add phthalic acid monoamide polyoxyethylene ether to a 0.3-0.5% sodium hydroxide solution, heat to 40-60℃, and react for 1-4 hours to obtain a viscous and transparent substance, which is sodium phthalic acid monoamide polyoxyethylene ether.

[0034] Further, in S1, the solvent is one or more of dichloromethane, trichloromethane, dichloroethane, cyclohexane, and toluene; the amount of solvent used is 3-4 times the mass of phthalic anhydride; the catalyst is one of the condensing agents dicyclohexylcarbodiimide (DCC), diisopropylcarbodiimide (DIC), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDCI), and 4-N,N-dimethylpyridine (DMAP); the reaction temperature is preferably 90-100℃, the reaction time is preferably 5-6 h; and the amount of ethanolamine added is preferably 1-1.1 equivalents of phthalic anhydride.

[0035] In S2, the preferred reaction temperature is 150-160℃;

[0036] In S3, the sodium hydroxide solution is preferably 0.4% by mass, and the reaction time is preferably 2-3 hours.

[0037] The chemical reaction formulas for the synthesis method of this invention are shown below:

[0038]

[0039]

[0040] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0041] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0042] Example 1

[0043] A method for preparing a foaming agent for oil fields includes the following steps:

[0044] S1: A four-necked flask is equipped with an oil bath, a stirring device, a thermometer, a condenser, and a dropping funnel. 140g of dichloromethane solvent is placed in the four-necked flask. 0.3mol of phthalic anhydride and 0.07g of dicyclohexylcarbodiimide (DCC) are added to the solvent. The reaction flask is protected with N2. The oil bath is heated to 90℃. 0.3mol of ethanolamine is added dropwise to the reaction flask at a rate of 1d / 2s. After the addition is complete, the reaction continues for 5 hours. At this point, the amine value of the reaction liquid remains unchanged. The temperature is lowered, and the solvent and unreacted ethanolamine are removed by rotation to obtain pale yellow phthalic acid monoethanolamide.

[0045] S2: Add 20g of phthalic acid monoethanolamide to the reaction vessel, and simultaneously weigh 0.04g of KOH and add it to the vessel. Then close the reaction vessel, evacuate the reaction system, and introduce nitrogen gas to remove air. Repeat this process 4 times to ensure that the oxygen content in the reaction system is at an ultra-low value. Then raise the temperature to 80℃, evacuate the system again to remove water, and continue for 40 minutes until no water is distilled off. After that, raise the temperature to 160℃ and introduce 44g of ethylene oxide to react until the pressure of the reaction system no longer decreases. A light yellow paste is obtained, which is phthalic acid monoethanolamide polyoxyethylene ether.

[0046] S3: Add 30g of phthalic acid monoamide polyoxyethylene ether to 100g of sodium hydroxide aqueous solution with a mass concentration of 0.4%, heat to 50℃, and react for 2h to obtain a viscous and transparent substance, a foaming agent for oil fields (i.e., sodium salt of phthalic acid monoamide polyoxyethylene ether).

[0047] Example 2

[0048] A method for preparing a foaming agent for oil fields includes the following steps:

[0049] S1: A four-necked flask is equipped with an oil bath, a stirring device, a thermometer, a condenser, and a dropping funnel. 130g of cyclohexane solvent is placed in the four-necked flask. 0.2mol of phthalic anhydride and 0.05g of diisopropylcarbodiimide (DIC) are added to the solvent. The reaction flask is protected with N2. The oil bath is heated to 80℃. 0.24mol of ethanolamine is added dropwise to the reaction flask at a rate of 1d / 5s. After the addition is complete, the reaction proceeds for another 4 hours. At this point, the amine value of the reaction liquid remains unchanged. The mixture is then cooled, and the solvent and unreacted ethanolamine are removed by rotation to obtain pale yellow phthalic acid monoethanolamide.

[0050] S2: Add 20g of phthalic acid monoethanolamide to the reaction vessel, and simultaneously weigh 0.06g of KOH and add it to the vessel. Then close the reaction vessel, evacuate the reaction system, and introduce nitrogen gas to remove air. Repeat this process 4 times to ensure that the oxygen content in the reaction system is at an ultra-low value. Then raise the temperature to 90℃, evacuate the vessel again to remove water, and continue for 40 minutes until no water is distilled off. After that, raise the temperature to 180℃ and introduce 46g of ethylene oxide to react until the pressure of the reaction system no longer decreases. A light yellow paste is obtained, which is phthalic acid monoethanolamide polyoxyethylene ether.

[0051] S3: Add 30g of phthalic acid monoamide polyoxyethylene ether to 80g of sodium hydroxide aqueous solution with a mass concentration of 0.5%, heat to 40℃, and react for 3h to obtain a viscous and transparent substance, a foaming agent for oil fields (i.e., sodium salt of phthalic acid monoamide polyoxyethylene ether).

[0052] Example 3

[0053] A method for preparing a foaming agent for oil fields includes the following steps:

[0054] S1: A four-necked flask is equipped with an oil bath, a stirring device, a thermometer, a condenser, and a dropping funnel. 135g of toluene solvent is placed in the four-necked flask. 0.25mol of phthalic anhydride and 0.07g of 4-N,N-dimethylpyridine (DMAP) are added to the solvent. The reaction flask is protected with N2. The oil bath is heated to 80℃. 0.3mol of ethanolamine is added dropwise to the reaction flask at a rate of 1d / 3s. After the addition is complete, the reaction proceeds for another 5 hours. At this point, the amine value of the reaction liquid remains unchanged. The mixture is then cooled, and the solvent and unreacted ethanolamine are removed by rotation to obtain pale yellow phthalic acid monoethanolamide.

[0055] S2: Add 17.5g of phthalic acid monoethanolamide to the reaction vessel, and simultaneously weigh 0.07g of KOH and add it to the vessel. Then close the reaction vessel, evacuate the reaction system, and introduce nitrogen gas to remove air. Repeat this process 4 times to ensure that the oxygen content in the reaction system is at an ultra-low value. Then raise the temperature to 80℃, evacuate the system again to remove water, and continue for 60 minutes until no water is distilled off. After that, raise the temperature to 140℃ and introduce 37.5g of ethylene oxide to react until the pressure of the reaction system no longer decreases, and a light yellow paste is obtained, which is phthalic acid monoethanolamide polyoxyethylene ether.

[0056] S3: Add 26.3g of phthalic acid monoamide polyoxyethylene ether to 80g of sodium hydroxide aqueous solution with a mass concentration of 0.5%, heat to 40℃, and react for 3h to obtain a viscous transparent substance, a foaming agent for oil fields (i.e., sodium salt of phthalic acid monoamide polyoxyethylene ether).

[0057] Example 4

[0058] A method for preparing a foaming agent for oil fields includes the following steps:

[0059] S1: A four-necked flask is equipped with an oil bath, a stirring device, a thermometer, a condenser, and a dropping funnel. 135g of chloroform solvent is placed in the four-necked flask. 0.25mol of phthalic anhydride and 0.07g of 4-N,N-dimethylpyridine (DMAP) are added to the solvent. The reaction flask is protected with N2. The oil bath is heated to 85℃. 0.3mol of ethanolamine is added dropwise to the reaction flask at a rate of 1d / 4s. After the addition is complete, the reaction proceeds for another 5 hours. At this point, the amine value of the reaction liquid remains unchanged. The mixture is then cooled, and the solvent and unreacted ethanolamine are removed by rotation to obtain pale yellow phthalic acid monoethanolamide.

[0060] S2: Add 17.5g of phthalic acid monoethanolamide to the reaction vessel, and simultaneously weigh 0.07g of KOH and add it to the vessel. Then close the reaction vessel, evacuate the reaction system, and introduce nitrogen gas to remove air. Repeat this process 4 times to ensure that the oxygen content in the reaction system is at an ultra-low value. Then raise the temperature to 80℃, evacuate the system again to remove water, and continue for 50 minutes until no water is distilled off. After that, raise the temperature to 160℃ and introduce 37.5g of ethylene oxide to react until the pressure of the reaction system no longer decreases, and a light yellow paste is obtained, which is phthalic acid monoethanolamide polyoxyethylene ether.

[0061] S3: Add 26.3g of phthalic acid monoamide polyoxyethylene ether to 80g of 0.5% sodium hydroxide aqueous solution, heat to 55℃, and react for 4h to obtain a foaming agent for oil fields.

[0062] Table 1 compares the oilfield foaming agent synthesized in this invention with commonly available foaming agents at a salinity of 10 × 10⁻⁶. 4 Comparison of foaming volume, foam half-life, and interfacial tension in aqueous solutions with a mineralization of mg / L (YT-1: foaming agent synthesized in this invention). The table shows that the foaming volume and half-life of the foaming agent synthesized in this invention are nearly twice that of commercially available agents, and the interfacial tension reaches an ultra-low level.

[0063] Table 1: Comparison of Performance Data of Different Foaming Agents

[0064]

[0065] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a foaming agent for oilfield use, characterized in that, Includes the following steps: S1: A mixed solution is obtained by mixing solvent, phthalic anhydride, and catalyst A. Ethanolamine is added dropwise to the mixed solution to carry out the reaction. After removing unreacted solvent and ethanolamine, white-yellow phthalic acid monoethanolamide is obtained. The amount of ethanolamine used is 0.9-1.2 equivalents of phthalic anhydride. The amount of catalyst A used is 0.1% equivalent of phthalic anhydride. S2: Mix white yellow phthalic acid monoethanolamide and catalyst B and place them in a reaction vessel, then evacuate until no water is distilled out; then introduce ethylene oxide to react and obtain phthalic acid monoethanolamide polyoxyethylene ether; the molar ratio of white yellow phthalic acid monoethanolamide to ethylene oxide is 1:(7-12). S3: Phthalic acid monoamide polyoxyethylene ether is added to sodium hydroxide solution and reacted fully to obtain a foaming agent for oil fields.

2. The method for preparing an oilfield foaming agent according to claim 1, characterized in that, In S1, the solvent, phthalic anhydride and catalyst A are mixed to obtain a mixed solution. After the mixed solution is heated to 80-120℃ in an oil bath, ethanolamine is added dropwise to the mixed solution at a rate of 1d / (2-5)s to react for 4-8h. After cooling to room temperature, the unreacted solvent and ethanolamine are removed to obtain white-yellow phthalic acid monoethanolamide.

3. The method for preparing an oilfield foaming agent according to claim 1, characterized in that, In S1, the amount of solvent used is 3-4 times the mass of phthalic anhydride.

4. The method for preparing an oilfield foaming agent according to claim 1, characterized in that, In S1, the solvent is one or more of dichloromethane, trichloromethane, dichloroethane, cyclohexane, and toluene; the catalyst A is a condensing agent, such as dicyclohexylcarbodiimide, diisopropylcarbodiimide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, or 4-N,N-dimethylaminopyridine.

5. The method for preparing an oilfield foaming agent according to claim 1, characterized in that, In S2, the catalyst B is KOH; the amount of catalyst B is 0.3%-0.4% of the mass of white yellow phthalic acid monoethanolamide.

6. The method for preparing an oilfield foaming agent according to claim 1, characterized in that, In S2, the reaction vessel is a reaction kettle; white yellow phthalic acid monoethanolamide and catalyst B are mixed and placed into the reaction kettle, then the reaction kettle is closed, the reaction kettle is evacuated and nitrogen gas is introduced to remove air; the temperature of the reaction kettle is raised to 80-90℃, and the vacuum is evacuated again for 40-60 minutes until no water is distilled out.

7. The method for preparing an oilfield foaming agent according to claim 6, characterized in that, In S2, ethylene oxide is then introduced to react and obtain phthalic acid monoamide polyoxyethylene ether. To obtain phthalic acid monoamide polyoxyethylene ether, the temperature of the reactor is raised to 140-180℃, and then ethylene oxide is introduced to react until the pressure of the reaction vessel no longer decreases.

8. The method for preparing an oilfield foaming agent according to claim 1, characterized in that, In S3, the mass concentration of the sodium hydroxide solution is 0.3-0.5%; the reaction temperature is 40-60℃; the reaction time is 1-4h; and the mass ratio of the phthalic acid monoamide polyoxyethylene ether to the sodium hydroxide solution is (25-30):(80-100).

9. A foaming agent for oilfield use, characterized in that, It is prepared by the method for preparing an oilfield foaming agent according to any one of claims 1 to 8.

10. A foaming agent for oilfield use according to claim 9, characterized in that, The chemical formula for the oilfield foaming agent is: ； Where n is 7-12.

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