Temperature-resistant and salt-resistant imbibition agent

Abstract

The invention relates to a temperature-resistant and salt-resistant imbibition agent. The temperature-resistant and salt-resistant imbibition agent is prepared by the following steps: carrying out Mannich reaction on p-xylylenediamine, formaldehyde and formic acid to synthesize a tetramethyl binary tertiary amine intermediate; and reacting the intermediate with alpha-bromo-carboxylic acid under an alkaline condition to generate the gemini betaine surfactant. The gemini betaine surfactant is compounded with one or two of a nonionic surfactant and small molecular alcohol to prepare the temperature-resistant and salt-resistant imbibition agent. The imbibition agent has the characteristics of easiness in entering a matrix pore channel, adsorption resistance and strong wetting reversal capability, can resist the temperature of 150 DEG C, can resist the salt of 15 * 10 < 4 > mg / L, and can meet the technical requirements of imbibition oil extraction of a low-permeability reservoir with the reservoir temperature of less than or equal to 150 DEG C and the mineralization degree of less than or equal to 15 * 10 < 4 > mg / L.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical agent synthesis for oil fields, and in particular relates to a temperature-resistant and salt-resistant imbibition agent. Background Art

[0002] Low-permeability oil and gas reservoirs have low porosity and permeability, and face problems such as difficulty in water injection and complex mining processes. The average recovery rate of low-permeability oil fields in my country is only 23.3%, 11.7% lower than the 35% of medium and high-permeability oil fields. At present, low-permeability oil and gas reservoirs account for more than half of the proven reserves. Combined with my country's current national conditions, low-permeability oil reservoirs have become a strategic replacement area for crude oil resources, but they have the characteristics of poor porosity and permeability conditions, strong reservoir heterogeneity, and poor water absorption capacity, resulting in low recovery rates in low-permeability oil fields. Therefore, the technical difficulty faced by the development of low-permeability oil reservoirs is extremely large.

[0003] Imbibition oil recovery is to use imbibition fluid to enter the pores of reservoir rocks, change the wettability of the matrix, reduce the oil-water interfacial tension, and the wetting phase fluid / imbibition fluid displaces the non-wetting phase fluid with the help of capillary force. In this process, spontaneous imbibition without external pressure is often accompanied. At present, imbibition agents mainly include surfactants, nano-silica and compound types, all of which can reduce the oil-water interfacial tension and change the wettability of the matrix, and have poor temperature resistance and salt resistance. For oil reservoirs with a mineralization higher than 30,000 mg / L, ordinary imbibition agents are prone to salting out and cannot be effectively dissolved in formation water; for oil reservoirs with a temperature higher than 100°C, some easily hydrolyzed functional groups will hydrolyze and lose the interfacial activity of the imbibition agent. In view of the poor temperature resistance and salt resistance of imbibition agents, technicians have carried out relevant research.

[0004] Chinese patent document CN114106806A discloses a heat-resistant and salt-resistant nanometer permeating agent and its synthesis method and application. The heat-resistant and salt-resistant nanometer permeating agent provided is BrCH 2 CH 2 OSi(OCH 2 CH 3 ) 3 , N-methylimidazole, RO(CH 2 CH 2 O) n- 1 CH 2 CH 2 OH, BrCH 2 COONa is a raw material that is made by step-by-step reaction. The imbibition agent has a temperature resistance of 150°C and a total mineralization of 32868 mg / L. However, its synthetic product belongs to the silyl ether compound, which is sensitive to acid and alkali and easily hydrolyzed, unstable, has weak compounding ability of silyl ether bond and divalent ion, and is not highly salt resistant.

[0005] Chinese patent document CN114410286A discloses a heat-resistant and salt-resistant nano-imbibition oil-displacing agent and its preparation method and application. The heat-resistant and salt-resistant nano-imbibition oil-displacing agent includes the following components: 20 to 40 parts by weight of active nano-materials; 10 to 30 parts by weight of non-ionic surfactants; 10 to 30 parts by weight of anionic surfactants; the active nano-materials are obtained by polymerizing raw materials containing double-bond-modified lamellar nano-materials, hydrophilic monomers and hydrophobic monomers. The operating temperature of the nano-imbibition oil-displacing agent is 70 to 120°C, and the mineralization is 10000 mg / LNaCl to 100000 mg / LNaCl. Gemini surfactants designed for the nano-imbibition oil-displacing agent The hydrophobic group is longer, and the hydrophilic carboxylic acid group is not as salt resistant as the sulfonic acid group. The molecular weight is larger and the cloud point is lower in salt water. Summary of the invention

[0006] The purpose of the present invention is to provide a temperature-resistant and salt-resistant imbibition agent, which is used to solve the problem that the oil displacement imbibition agent in the prior art is insufficiently temperature-resistant and salt-resistant.

[0007] To achieve the above purpose, the technical solution adopted by the heat-resistant and salt-resistant imbibition agent provided by the present invention is:

[0008] A temperature-resistant and salt-resistant imbibition agent comprises a gemini betaine surfactant and water; and also comprises one or two of a nonionic surfactant and a small molecule alcohol; the structural formula of the gemini betaine surfactant is:

[0009]

[0010] Wherein, R is a C12-C16 chain saturated alkane;

[0011] The mass ratio of the gemini betaine surfactant, the nonionic surfactant and the small molecule alcohol is (0.1-0.5): (0.1-0.3): (0.1-0.2).

[0012] The beneficial effects of the present invention are as follows: the present invention designs a gemini betaine surfactant with a gemini and positive and negative double charge structure, which has double hydrophilic groups, strong space-occupying ability, and double hydrophobic groups with strong oil displacement ability; it has positive and negative double charges, no precipitation at the isoelectric point, and strong salt resistance; an alkylbenzene rigid group is used to link two hydrophilic groups and two hydrophobic chains through chemical bonds, thereby enhancing the stability of the system and enhancing the temperature resistance.

[0013] The above-mentioned Gemini betaine surfactant is compounded with nonionic surfactant and small molecule alcohol, so that the penetrant has the characteristics of easy entry into the matrix pores, anti-adsorption, and strong wetting reversal ability, and can achieve temperature resistance of 150°C and salt resistance of 15×10 4 mg / L.

[0014] The carbon numbers of the three components in the imbibition agent prepared by the present invention are different in number, wherein the gemini betaine surfactant has a carbon number of 29 to 36 and a hydrophobic chain of 12 to 16 carbons; the nonionic surfactant has a carbon number of 8 to 10 and the small molecule alcohol has a carbon number of 2 to 6. The different molecular sizes and different carbon chain lengths are combined to achieve a synergistic effect. The small molecule alcohol can increase the fluidity of the interfacial film and increase the speed at which the interfacial tension decreases; the medium-molecular nonionic surfactant has a "fast running speed" as the hydrophilic groups in the molecular structure react with the clay material in advance, and the hydrophobic groups are arranged outward, reducing the subsequent loss of the imbibition agent. The gemini betaine surfactant with a relatively large molecular weight has a strong space-occupying ability and displaces the crude oil on the matrix.

[0015] In order to allow the hydrophilic groups in the molecular structure to react with the clay material in advance, and the hydrophobic groups to be arranged outwards, thereby reducing the subsequent loss of the imbibing agent, preferably, the non-ionic surfactant is a C8-C10 alkyl alcohol polyoxyethylene ether.

[0016] Further preferably, the nonionic surfactant is any one of isooctyl alcohol polyoxyethylene ether, decanol polyoxyethylene ether, and octanol polyoxyethylene ether.

[0017] In order to further increase the fluidity of the interfacial film and speed up the reduction of the interfacial tension, preferably, the small molecule alcohol is a monohydric or dihydric alcohol of C2 to C6.

[0018] More preferably, the small molecule alcohol is any one of ethylene glycol, n-butanol, propylene glycol and propanol.

[0019] In order to reduce the surface tension and interfacial tension of the heat-resistant and salt-resistant imbibing agent and improve the salt and temperature resistance of the imbibing agent, preferably, in the heat-resistant and salt-resistant imbibing agent, the mass proportion of the gemini betaine surfactant is 0.1 to 0.5‰.

[0020] The preparation method of the heat-resistant and salt-resistant imbibition agent comprises the steps of preparing the gemini betaine surfactant and mixing the nonionic surfactant, the small molecule alcohol and water; the preparation method of the gemini betaine surfactant comprises: synthesizing p-phenylenediamine with formaldehyde and formic acid through Mannich reaction to obtain a tetramethyl ditertiary amine intermediate; the intermediate is then reacted with α-bromocarboxylic acid in the presence of an alkaline substance to generate; the α-bromocarboxylic acid has a general formula of RBrCHCOOH, wherein R is a C12-C16 chain saturated alkane.

[0021] The beneficial effect of the above technical scheme is that in the preparation method of the heat-resistant and salt-resistant penetrant of the present invention, the prepared gemini betaine surfactant with a gemini and a positive and negative double charge structure is compounded with one or two of a nonionic surfactant and a small molecule alcohol, and the penetrant has the characteristics of easy entry into the matrix pores, anti-adsorption, and strong wetting reversal ability through different molecular sizes and different carbon chain lengths. The heat-resistant and salt-resistant penetrant can achieve a temperature resistance of 150°C and a salt resistance of 15×10 4 mg / L. Small molecule alcohol can increase the fluidity of the interfacial film and increase the speed of decreasing interfacial tension; medium molecule nonionic surfactants, which "run fast" as the previous "troops", the hydrophilic groups in the molecular structure react with clay substances in advance, and the hydrophobic groups are arranged outward, reducing the loss of subsequent penetrants. Gemini betaine surfactants with relatively large molecular weight have strong space-occupying ability and displace crude oil on the matrix.

[0022] Specifically, the synthesis route of the gemini betaine surfactant is as follows:

[0023]

[0024] More preferably, the α-bromocarboxylic acid is one of α-bromododecylacetic acid, α-bromotetradecylacetic acid or α-bromohexadecylacetic acid.

[0025] In order to ensure that the reaction of p-phenylenediamine with formaldehyde and formic acid is sufficient, rapid and effective, preferably, the temperature for synthesizing the tetramethyl ditertiary amine intermediate is 50-80° C. and the time is 8-48 hours.

[0026] More preferably, the temperature for synthesizing the tetramethyl diamine intermediate is 50 to 70° C. and the time is 8 to 24 hours.

[0027] In order to enhance the stability and temperature resistance of the gemini betaine surfactant, preferably, the molar ratio of p-phenylenediamine, formaldehyde and formic acid is (1-1.1): (2-2.2): (2.1-2.2).

[0028] More preferably, the molar ratio of the p-phenylenediamine to formaldehyde and formic acid is 1:(2-2.1):(2.1-2.2).

[0029] In order to make the intermediate react with α-bromocarboxylic acid mildly and fully, preferably, the intermediate reacts with α-bromocarboxylic acid at a temperature of 50-100° C., a time of 8-48 h, and a pH of 8-10.

[0030] More preferably, the intermediate is reacted with α-bromocarboxylic acid at a temperature of 50-80° C., a time of 8-24 h, and a pH of 8-9.

[0031] In order to enhance the salt resistance of the gemini betaine surfactant, preferably, the molar ratio of p-phenylenediamine to α-bromocarboxylic acid is (1-1.1): (2-2.5).

[0032] The application of the above-mentioned temperature-resistant and salt-resistant imbibition agent in the development of low-permeability oil reservoirs.

[0033] The beneficial effect of the above technical solution is that the heat-resistant and salt-resistant imbibition agent provided by the present application has good heat and salt resistance, low permeability, and a mineralization resistance of 15×10 4 mg / L, temperature resistance of 150℃, can be used in the development of low permeability oil reservoirs to improve the recovery rate of low permeability fractured oil fields, which is of great significance and economic value to improving the development efficiency of low permeability oil reservoirs. DETAILED DESCRIPTION

[0034] The oil displacement imbibition agent in the prior art is not heat-resistant and salt-resistant enough. The present invention provides a heat-resistant and salt-resistant imbibition agent, which comprises a gemini betaine surfactant and water; and also comprises one or two of a nonionic surfactant and a small molecule alcohol;

[0035] The structural formula of the gemini betaine surfactant is:

[0036]

[0037] Wherein, R is a C12-C16 chain saturated alkane;

[0038] The mass ratio of the gemini betaine surfactant, the nonionic surfactant and the small molecule alcohol is (0.1-0.5): (0.1-0.3): (0.1-0.2).

[0039] The technical concept of the present invention is: the present invention designs and synthesizes a gemini betaine surfactant with a gemini and positive and negative double charge structure, which has the characteristics of strong occupancy capacity, strong double hydrophobic group oil displacement capacity, strong salt resistance, enhanced system stability, and enhanced temperature resistance. The compound nonionic surfactant and one or two of the small molecule alcohols are combined with different molecular sizes and different carbon chain lengths to achieve synergistic effects, so that the imbibition agent has the characteristics of easy entry into the matrix pores, anti-adsorption, and strong wetting reversal ability, and can achieve a temperature resistance of 150°C and a salt resistance of 15×10 4 mg / L.

[0040] Specifically, the method for preparing the gemini betaine surfactant comprises the following steps:

[0041] (1) In a normal pressure reactor equipped with a heating, stirring and temperature control system, p-phenylenediamine, formaldehyde and formic acid are added in a molar ratio of (1-1.1): (2-2.2): (2.1-2.2), an appropriate amount of solvent is added, and the mixture is stirred at a constant temperature of 50-80° C. for 8-48 hours;

[0042] (2) adding an appropriate amount of alkaline substance to the above reaction solution to adjust the pH to 8-10, adding α-bromocarboxylic acid at a molar ratio of 2-2.5 times that of p-phenylenediamine dropwise, and stirring at a constant temperature of 50-100° C. for 8-48 hours;

[0043] (3) Cooling to room temperature, adjusting the pH to 6-7, and filtering to obtain a gemini betaine surfactant solid.

[0044] Preferably, the solvent is at least one of deionized water or ethanol.

[0045] Preferably, the alkaline substance is selected from at least one of NaOH solution, KOH solution or ammonia solution.

[0046] In the following examples and comparative examples, the CAS number of the nonionic surfactant isooctyl alcohol polyoxyethylene ether is No. 26468-86-0, the CAS number of decanol polyoxyethylene ether is No. 26183-52-8, and the CAS number of octanol polyoxyethylene ether is No. 71060-57-6.

[0047] The implementation process of the present invention is described in detail below in conjunction with specific embodiments.

[0048] 1. Specific embodiments of the heat-resistant and salt-resistant imbibition agent of the present invention

[0049] Example 1

[0050] The heat-resistant and salt-resistant imbibition agent of the present embodiment is composed of a gemini betaine surfactant, a nonionic surfactant, a small molecule alcohol and water. The mass fractions of the gemini betaine surfactant, the nonionic surfactant and the small molecule alcohol in the imbibition agent are 0.1‰, 0.1‰ and 0.1‰ respectively, and water is the solvent; wherein:

[0051] The structural formula of Gemini betaine surfactant is:

[0052]

[0053] Wherein, R is a C12 chain saturated alkane;

[0054] The nonionic surfactant is: isooctyl alcohol polyoxyethylene ether;

[0055] Small molecule alcohol is: ethylene glycol.

[0056] The method for preparing the heat-resistant and salt-resistant imbibition agent of the present embodiment comprises the following steps:

[0057] Step 1: Preparation of Gemini Betaine Surfactant:

[0058] (1) In a three-necked round-bottom flask, add p-phenylenediamine, formaldehyde, and formic acid in a molar ratio of 1:2.1:2.1, with a total mass of 30 g, add 150 ml of ethanol, and stir at a constant temperature of 50°C for 8 h;

[0059] (2) 5.6 mL of 30% NaOH was added to the reaction solution to adjust the pH to 8, and α-bromododecylacetic acid with a molar ratio of 2.0 times that of p-phenylenediamine was added dropwise, and the mixture was stirred at a constant temperature of 50° C. for 8 h;

[0060] (3) Cool to room temperature, adjust the pH to 6, and filter to obtain a gemini betaine surfactant solid.

[0061] Step 2: Preparation of heat-resistant and salt-resistant imbibition agent:

[0062] Measure 100 parts of water, slowly add 0.1‰ gemini betaine surfactant, 0.1‰ nonionic surfactant and 0.1‰ small molecule alcohol in sequence under stirring, stir for more than 1 hour to allow each component to fully dissolve, and obtain a temperature-resistant and salt-resistant imbibition agent.

[0063] Example 2

[0064] The heat-resistant and salt-resistant imbibition agent of the present embodiment is composed of a gemini betaine surfactant, a nonionic surfactant, a small molecule alcohol and water. The mass fractions of the gemini betaine surfactant, the nonionic surfactant and the small molecule alcohol in the imbibition agent are 0.2‰, 0.2‰ and 0.2‰ respectively, and water is the solvent; wherein:

[0065] The structural formula of Gemini betaine surfactant is:

[0066]

[0067] Wherein, R is a C14 chain saturated alkane;

[0068] The nonionic surfactant is: polyoxyethylene decyl alcohol ether;

[0069] Small molecule alcohol: n-butanol.

[0070] The method for preparing the heat-resistant and salt-resistant imbibition agent of the present embodiment comprises the following steps:

[0071] Step 1: Preparation of Gemini Betaine Surfactant:

[0072] (1) In a three-necked round-bottom flask, add p-phenylenediamine, formaldehyde, and formic acid in a molar ratio of 1:2.1:2.2, with a total mass of 30 g, add 120 mL of ethanol, and stir at a constant temperature of 60°C for 12 h;

[0073] (2) 5.6 mL of 30% NaOH was added to the reaction solution to adjust the pH to 8, and α-bromotetradecylacetic acid with a molar ratio of 2 to p-phenylenediamine was added dropwise, and the mixture was stirred at a constant temperature of 60° C. for 12 h;

[0074] (3) Cool to room temperature, adjust the pH to 6, and filter to obtain a gemini betaine surfactant solid.

[0075] Step 2: Preparation of heat-resistant and salt-resistant imbibition agent:

[0076] Measure 100 parts of water, slowly add 0.2‰ gemini betaine surfactant, 0.2‰ nonionic surfactant and 0.2‰ small molecule alcohol in sequence under stirring, stir for more than 1 hour to allow each component to fully dissolve, and obtain a temperature-resistant and salt-resistant imbibition agent.

[0077] Example 3

[0078] The heat-resistant and salt-resistant imbibition agent of the present embodiment is composed of a gemini betaine surfactant, a nonionic surfactant, a small molecule alcohol and water, wherein the mass fractions of the gemini betaine surfactant, the nonionic surfactant and the small molecule alcohol in the imbibition agent are 0.3‰, 0.3‰ and 0.2‰ respectively, and water is the solvent; wherein:

[0079] The structural formula of Gemini betaine surfactant is:

[0080]

[0081] Wherein, R is a C16 chain saturated alkane;

[0082] The nonionic surfactant is: octanol polyoxyethylene ether;

[0083] Small molecule alcohol: propylene glycol.

[0084] The method for preparing the heat-resistant and salt-resistant imbibition agent of the present embodiment comprises the following steps:

[0085] Step 1: Preparation of Gemini Betaine Surfactant:

[0086] (1) In a three-necked round-bottom flask, add p-phenylenediamine, formaldehyde, and formic acid in a molar ratio of 1:2:2.2, with a total mass of 29 g, add 110 mL of ethanol, and stir at a constant temperature of 65°C for 20 h;

[0087] (2) 5.7 mL of 30% NaOH was added to the reaction solution to adjust the pH to 9, and α-bromohexadecylacetic acid with a molar ratio of 2.1 times that of p-phenylenediamine was added dropwise, and the mixture was stirred at a constant temperature of 65° C. for 20 h;

[0088] (3) Cool to room temperature, adjust the pH to 6, and filter to obtain a gemini betaine surfactant solid.

[0089] Step 2: Preparation of heat-resistant and salt-resistant imbibition agent:

[0090] Measure 100 parts of water, and slowly add the following in sequence under stirring: 0.3‰ gemini betaine surfactant, 0.3‰ nonionic surfactant and 0.2‰ small molecule alcohol, and stir for more than 1 hour to allow each component to fully dissolve to obtain an imbibing agent.

[0091] Example 4

[0092] The heat-resistant and salt-resistant imbibition agent of the present embodiment is composed of a gemini betaine surfactant, a nonionic surfactant, a small molecule alcohol and water, wherein the mass fractions of the gemini betaine surfactant, the nonionic surfactant and the small molecule alcohol in the imbibition agent are 0.2‰, 0.1‰ and 0.2‰ respectively, and water is the solvent; wherein:

[0093] The structural formula of Gemini betaine surfactant is:

[0094]

[0095] Wherein, R is a C12 chain saturated alkane;

[0096] The nonionic surfactant is: isooctyl alcohol polyoxyethylene ether;

[0097] Small molecule alcohol is: propanol.

[0098] The method for preparing the heat-resistant and salt-resistant imbibition agent of the present embodiment comprises the following steps:

[0099] Step 1: Preparation of Gemini Betaine Surfactant:

[0100] (1) In a three-necked round-bottom flask, add p-phenylenediamine, formaldehyde, and formic acid in a molar ratio of 1:2:2.2, with a total mass of 30 g, add 120 mL of ethanol, and stir at a constant temperature of 65°C for 20 h;

[0101] (2) 5.8 mL of 30% NaOH was added to the reaction solution to adjust the pH to 9, and α-bromododecylacetic acid with a molar ratio of 2.1 times that of p-phenylenediamine was added dropwise, and the mixture was stirred at a constant temperature of 70° C. for 20 h;

[0102] (3) Cooling to room temperature, adjusting the pH to 7, and filtering to obtain a gemini betaine surfactant solid.

[0103] Step 2: Preparation of heat-resistant and salt-resistant imbibition agent:

[0104] Measure 100 parts of water, slowly add 0.2‰ gemini betaine surfactant, 0.1‰ nonionic surfactant and 0.2‰ small molecule alcohol in sequence under stirring, stir for more than 1 hour to allow each component to fully dissolve, and obtain the imbibition agent.

[0105] Example 5

[0106] The heat-resistant and salt-resistant imbibition agent of the present embodiment is composed of a gemini betaine surfactant, a nonionic surfactant, a small molecule alcohol and water, wherein the mass fractions of the gemini betaine surfactant, the nonionic surfactant and the small molecule alcohol in the imbibition agent are 0.3‰, 0.2‰ and 0.2‰ respectively, and water is the solvent; wherein:

[0107] The structural formula of Gemini betaine surfactant is:

[0108]

[0109] Wherein, R is a C14 chain saturated alkane;

[0110] The nonionic surfactant is: polyoxyethylene decyl alcohol ether;

[0111] Small molecule alcohol: n-butanol.

[0112] The method for preparing the heat-resistant and salt-resistant imbibition agent of the present embodiment comprises the following steps:

[0113] Step 1: Preparation of Gemini Betaine Surfactant:

[0114] (1) In a three-necked round-bottom flask, add p-phenylenediamine, formaldehyde, and formic acid in a molar ratio of 1:2.1:2.2, with a total mass of 30 g, add 110 mL of ethanol, and stir at a constant temperature of 70°C for 24 h;

[0115] (2) 5.6 mL of 30% NaOH was added to the reaction solution to adjust the pH to 9, and α-bromotetradecylacetic acid with a molar ratio of 2.2 times that of p-phenylenediamine was added dropwise, and the mixture was stirred at a constant temperature of 70° C. for 24 h;

[0116] (3) Cool to room temperature, adjust the pH to 6, and filter to obtain a gemini betaine surfactant solid.

[0117] Step 2: Preparation of heat-resistant and salt-resistant imbibition agent:

[0118] Measure 100 parts of water, slowly add 0.3‰ gemini betaine surfactant, 0.2‰ nonionic surfactant and 0.2‰ small molecule alcohol in sequence under stirring, stir for more than 1 hour to allow each component to fully dissolve, and obtain the imbibition agent.

[0119] Example 6

[0120] The heat-resistant and salt-resistant imbibition agent of the present embodiment is composed of a gemini betaine surfactant, a nonionic surfactant, a small molecule alcohol and water. The mass fractions of the gemini betaine surfactant, the nonionic surfactant and the small molecule alcohol in the imbibition agent are 0.4‰, 0.1‰ and 0.1‰ respectively, and water is the solvent; wherein:

[0121] The structural formula of Gemini betaine surfactant is:

[0122]

[0123] Wherein, R is a C16 chain saturated alkane;

[0124] The nonionic surfactant is: isooctyl alcohol polyoxyethylene ether;

[0125] Small molecule alcohol: propylene glycol.

[0126] The method for preparing the heat-resistant and salt-resistant imbibition agent of the present embodiment comprises the following steps:

[0127] Step 1: Preparation of Gemini Betaine Surfactant:

[0128] (1) In a three-necked round-bottom flask, add p-phenylenediamine, formaldehyde, and formic acid in a molar ratio of 1:2.1:2.1, add 150 mL of ethanol, and stir at 75°C for 24 h;

[0129] (2) 5.6 mL of 30% NaOH was added to the reaction solution to adjust the pH to 9, and α-bromohexadecylacetic acid with a molar ratio of 2.3 times that of p-phenylenediamine was added dropwise, and the mixture was stirred at a constant temperature of 75° C. for 24 h;

[0130] (3) Cooling to room temperature, adjusting the pH to 7, and filtering to obtain a gemini betaine surfactant solid.

[0131] Step 2: Preparation of heat-resistant and salt-resistant imbibition agent:

[0132] Measure 100 parts of water, slowly add 0.4‰ gemini betaine surfactant, 0.1‰ nonionic surfactant and 0.1‰ small molecule alcohol in sequence under stirring, stir for more than 1 hour to allow each component to fully dissolve, and obtain an imbibing agent.

[0133] Example 7

[0134] The heat-resistant and salt-resistant imbibition agent of the present embodiment is composed of a gemini betaine surfactant, a nonionic surfactant, a small molecule alcohol and water, wherein the mass fractions of the gemini betaine surfactant, the nonionic surfactant and the small molecule alcohol in the imbibition agent are 0.5‰, 0.2‰ and 0.1‰ respectively, and water is the solvent; wherein:

[0135] The structural formula of Gemini betaine surfactant is:

[0136]

[0137] Wherein, R is a C12 chain saturated alkane;

[0138] The nonionic surfactant is: octanol polyoxyethylene ether;

[0139] Small molecule alcohol: n-butanol.

[0140] The method for preparing the heat-resistant and salt-resistant imbibition agent of the present embodiment comprises the following steps:

[0141] Step 1: Preparation of Gemini Betaine Surfactant:

[0142] (1) In a three-necked round-bottom flask, add p-phenylenediamine, formaldehyde, and formic acid in a molar ratio of 1:2.2:2.2, with a total mass of 30 g, add 120 mL of ethanol, and stir at a constant temperature of 75°C for 32 h;

[0143] (2) 5.6 mL of 30% NaOH was added to the reaction solution to adjust the pH to 8, and α-bromododecylacetic acid with a molar ratio of 2.4 times that of p-phenylenediamine was added dropwise, and the mixture was stirred at a constant temperature of 80° C. for 32 h;

[0144] (3) Cooling to room temperature, adjusting the pH to 7, and filtering to obtain a gemini betaine surfactant solid.

[0145] Step 2: Preparation of heat-resistant and salt-resistant imbibition agent:

[0146] Measure 100 parts of water, slowly add 0.5‰ gemini betaine surfactant, 0.2‰ nonionic surfactant and 0.1‰ small molecule alcohol in sequence under stirring, stir for more than 1 hour to allow each component to fully dissolve, and obtain the imbibition agent.

[0147] Example 8

[0148] The heat-resistant and salt-resistant imbibition agent of the present embodiment is composed of a gemini betaine surfactant, a nonionic surfactant, a small molecule alcohol and water, wherein the mass fractions of the gemini betaine surfactant, the nonionic surfactant and the small molecule alcohol in the imbibition agent are 0.5‰, 0.1‰ and 0.1‰ respectively, and water is the solvent; wherein:

[0149] The structural formula of Gemini betaine surfactant is:

[0150]

[0151] Wherein, R is a C14 chain saturated alkane;

[0152] The nonionic surfactant is: isooctyl alcohol polyoxyethylene ether;

[0153] Small molecule alcohol is: ethylene glycol.

[0154] The method for preparing the heat-resistant and salt-resistant imbibition agent of the present embodiment comprises the following steps:

[0155] Step 1: Preparation of Gemini Betaine Surfactant:

[0156] (1) In a three-necked round-bottom flask, add p-phenylenediamine, formaldehyde, and formic acid in a molar ratio of 1:2.1:2.2, with a total mass of 30 g, add 120 mL of ethanol, and stir at a constant temperature of 80°C for 48 h;

[0157] (2) 5.7 mL of 30% NaOH was added to the reaction solution to adjust the pH to 10, and α-bromotetradecylacetic acid with a molar ratio of 2.5 times that of p-phenylenediamine was added dropwise, and the mixture was stirred at a constant temperature of 85° C. for 48 h;

[0158] (3) Cool to room temperature, adjust the pH to 6, and filter to obtain a gemini betaine surfactant solid.

[0159] Step 2: Preparation of heat-resistant and salt-resistant imbibition agent:

[0160] Measure 100 parts of water, slowly add 0.5‰ gemini betaine surfactant, 0.1‰ nonionic surfactant and 0.1‰ small molecule alcohol in sequence under stirring, stir for more than 1 hour to allow each component to fully dissolve, and obtain the imbibition agent.

[0161] Example 9

[0162] The heat-resistant and salt-resistant imbibition agent of the present embodiment is composed of a gemini betaine surfactant, a nonionic surfactant, a small molecule alcohol and water. The mass fractions of the gemini betaine surfactant, the nonionic surfactant and the small molecule alcohol in the imbibition agent are 0.3‰, 0.2‰ and 0.1‰ respectively, and water is the solvent; wherein:

[0163] The structural formula of Gemini betaine surfactant is:

[0164]

[0165] Wherein, R is a C16 chain saturated alkane;

[0166] The nonionic surfactant is: polyoxyethylene decyl alcohol ether;

[0167] Small molecule alcohol is: ethylene glycol.

[0168] The method for preparing the heat-resistant and salt-resistant imbibition agent of the present embodiment comprises the following steps:

[0169] Step 1: Preparation of Gemini Betaine Surfactant:

[0170] (1) In a three-necked round-bottom flask, add p-phenylenediamine, formaldehyde, and formic acid in a molar ratio of 1:2:2.2, with a total mass of 30 g, add 150 mL of ethanol, and stir at a constant temperature of 80°C for 48 h;

[0171] (2) 5.8 mL of 30% NaOH was added to the reaction solution to adjust the pH to 10, and α-bromohexadecylacetic acid with a molar ratio of 2.0 times that of p-phenylenediamine was added dropwise, and the mixture was stirred at a constant temperature of 100° C. for 48 h;

[0172] (3) Cooling to room temperature, adjusting the pH to 7, and filtering to obtain a gemini betaine surfactant solid.

[0173] Step 2: Preparation of heat-resistant and salt-resistant imbibition agent:

[0174] Measure 100 parts of water, and slowly add the following in sequence under stirring: 0.3‰ gemini betaine surfactant, 0.2‰ nonionic surfactant and 0.1‰ small molecule alcohol, and stir for more than 1 hour to allow each component to fully dissolve to obtain an imbibing agent.

[0175] Example 10

[0176] The heat-resistant and salt-resistant imbibition agent of this embodiment is composed of a gemini betaine surfactant, a small molecule alcohol and water. The mass fractions of the gemini betaine surfactant and the small molecule alcohol in the imbibition agent are 0.2‰ and 0.2‰ respectively, and water is the solvent; wherein:

[0177] The structural formula of Gemini betaine surfactant is:

[0178]

[0179] Wherein, R is a C14 chain saturated alkane;

[0180] Small molecule alcohol is: ethylene glycol.

[0181] The method for preparing the heat-resistant and salt-resistant imbibition agent of the present embodiment comprises the following steps:

[0182] Step 1: Preparation of Gemini Betaine Surfactant:

[0183] (1) In a three-necked round-bottom flask, add p-phenylenediamine, formaldehyde, and formic acid in a molar ratio of 1:2:2.2, with a total mass of 30 g, add 120 mL of ethanol, and stir at a constant temperature of 70°C for 24 h;

[0184] (2) 5.7 mL of 30% NaOH was added to the reaction solution to adjust the pH to 9, and α-bromotetradecylacetic acid with a molar ratio of 2.2 times that of p-phenylenediamine was added dropwise, and the mixture was stirred at a constant temperature of 70° C. for 24 h;

[0185] (3) Cool to room temperature, adjust the pH to 6, and filter to obtain a gemini betaine surfactant solid.

[0186] Step 2: Preparation of heat-resistant and salt-resistant imbibition agent:

[0187] Measure 100 parts of water, and slowly add the following in sequence under stirring: 0.2‰ gemini betaine surfactant and 0.2‰ low molecular alcohol, and stir for more than 1 hour to allow each component to fully dissolve to obtain an imbibing agent.

[0188] Embodiment 11

[0189] The heat-resistant and salt-resistant imbibition agent of the present embodiment is composed of a gemini betaine surfactant, a nonionic surfactant and water, wherein the mass fractions of the gemini betaine surfactant and the nonionic surfactant in the imbibition agent are 0.2‰ and 0.1‰ respectively, and the water solvent is used; wherein:

[0190] The structural formula of Gemini betaine surfactant is:

[0191]

[0192] Wherein, R is a C16 chain saturated alkane;

[0193] The nonionic surfactant is polyoxyethylene isooctyl alcohol ether.

[0194] The method for preparing the heat-resistant and salt-resistant imbibition agent of the present embodiment comprises the following steps:

[0195] Step 1: Preparation of Gemini Betaine Surfactant:

[0196] (1) In a three-necked round-bottom flask, add p-phenylenediamine, formaldehyde, and formic acid in a molar ratio of 1:2:2.2, with a total mass of 30 g, add 120 mL of ethanol, and stir at a constant temperature of 70°C for 24 h;

[0197] (2) 5.7 mL of 30% NaOH was added to the reaction solution to adjust the pH to 9, and α-bromohexadecylacetic acid with a molar ratio of 2.3 times that of p-phenylenediamine was added dropwise, and the mixture was stirred at a constant temperature of 70° C. for 24 h;

[0198] (3) Cool to room temperature, adjust the pH to 6, and filter to obtain a gemini betaine surfactant solid.

[0199] Step 2: Preparation of heat-resistant and salt-resistant imbibition agent:

[0200] Measure 100 parts of water, and slowly add the following in sequence under stirring: 0.2‰ gemini betaine surfactant and 0.1‰ non-ionic surfactant, and stir for more than 1 hour to allow each component to fully dissolve to obtain an imbibing agent.

[0201] In the technical solution of the present invention, the molar ratio of benzyl diamine is within the range of 1 to 1.1, which can achieve the technical effect of enhancing the stability and temperature resistance of the gemini betaine surfactant.

[0202] 2. Comparison

[0203] Comparative Example 1: Heat-resistant and salt-resistant imbibition agent and its preparation, without adding gemini betaine surfactant:

[0204] Raw material composition of heat-resistant and salt-resistant insipidant: The heat-resistant and salt-resistant insipidant of comparative example 1 is composed of a non-ionic surfactant, a small molecule alcohol and water. The mass fractions of the non-ionic surfactant and the small molecule alcohol in the insipidant are 0.1‰ and 0.2‰ respectively, and water is the solvent; wherein: the non-ionic surfactant is polyoxyethylene isooctyl alcohol; and the small molecule alcohol is n-butanol.

[0205] Preparation of heat-resistant and salt-resistant imbibition agent:

[0206] Measure 100 parts of water, slowly add 0.1‰ non-ionic surfactant and 0.2‰ low-molecular alcohol in sequence under stirring, and stir for more than 1 hour to allow each component to fully dissolve to obtain an imbibing agent.

[0207] 3. Experimental Examples

[0208] Experimental Example 1: Performance test of heat-resistant and salt-resistant imbibition agent:

[0209] Use the live 15×10 4 The sample solutions of the heat-resistant and salt-resistant imbibition agents obtained in Examples 1 to 11 and Comparative Example 1 were prepared with water having a mineralization degree of mg / L and the following performance tests were carried out.

[0210] (1) Surface / interfacial tension

[0211] Surface tension: Take the prepared imbibition agent sample solution and test it with a surface tension meter at 25°C. Measure it three times in a row and take the average value. The test results are shown in Table 1.

[0212] Interfacial tension: Take the prepared imbibition agent sample solution and measure its interfacial tension value at 70°C with kerosene as the low-density phase according to the spinning drop method specified in 3.3 of SY / T5370-2018. Measure three times in a row and take the average value. The test results are shown in Table 1.

[0213] (2) Contact angle

[0214] Prepare low-permeability sandstone core slices with a thickness of about 5 mm, grind the cut surface with sandpaper, clean the sandstone core slices with alcohol and distilled water, and place them in an oven for one day to dry;

[0215] The core pieces were placed in crude oil and immersed at 60°C for more than 48 hours for aging to make them oil-wet surfaces;

[0216] The sandstone core piece was taken out, the surface oil was wiped clean with paper, and then immersed in the prepared imbibition agent sample solution and placed in an oven at 60°C for 24 hours. The contact angles of the core piece surface, air and water were measured using a Kruess DSA25 contact angle meter. The measurements were taken three times in a row and the average value was taken. The test results are shown in Table 1.

[0217] (3) Temperature resistance

[0218] The prepared imbibition agent sample solution was sealed and placed in a 150°C oven for aging for 15 days. The samples were taken out and tested according to the above performance test method. The surface tension, interfacial tension and contact angle values ​​after high temperature aging were recorded. The test results are shown in Table 1.

[0219] Table 1 Performance test data of Examples 1 to 11 and Comparative Example 1 before and after aging

[0220]

[0221] As shown in Table 1, the sample solutions prepared by the imbibition agents of Examples 1 to 9 have a surface tension of 23.95 to 25.62 mN / m, an oil-water interfacial tension of 0.0005 to 0.0009 mN / m, and a water contact angle of 10.2° to 11.2° before aging; after aging, the corresponding surface tension is 23.52 to 25.01 mN / m, the oil-water interfacial tension is 0.0005 to 0.0010 mN / m, and the water contact angle is 10.2° to 11.5°. It can be seen that the surface tension, oil-water interfacial tension, and water contact angle of the sample solutions prepared by the imbibition agents of Examples 1 to 9 are relatively small; the surface tension, oil-water interfacial tension, and water contact angle are basically unchanged before and after aging. Therefore, the gemini betaine surfactant, nonionic surfactant, and small molecule alcohol are used in a ratio at the same time, and the heat and salt resistance are strong, and the heat and salt resistance and imbibition effect are the best.

[0222] The sample solution prepared by the imbibition agent in Example 10, without adding nonionic surfactant, has a surface tension of 25.11mN / m, an oil-water interfacial tension of 0.0009mN / m, and a water contact angle of 22.3° before aging; after aging, the corresponding surface tension is 25.58mN / m, the oil-water interfacial tension is 0.0009mN / m, and the water contact angle is 25.3°. It can be seen that the surface tension and oil-water interfacial tension of the sample solution prepared by the imbibition agent in Example 10 are basically the same as those in Examples 1 to 9, and the water contact angle is larger than that in Examples 1 to 9; the surface tension and oil-water interfacial tension are basically unchanged before and after aging, and the water contact angle changes less after aging, and it has strong heat and salt resistance.

[0223] The sample solution prepared by the absorbing agent in Example 11, without adding small molecule alcohol, has a surface tension of 24.25mN / m, an oil-water interfacial tension of 0.0006mN / m, and a water contact angle of 15.5° before aging; after aging, the corresponding surface tension is 24.11mN / m, the oil-water interfacial tension is 0.0006mN / m, and the water contact angle is 15.8°. It can be seen that the sample solution prepared by the absorbing agent in Example 11 has a surface tension and an oil-water interfacial tension that are basically the same as those in Examples 1 to 9, and a larger contact angle than that in Examples 1 to 9; the surface tension, oil-water interfacial tension, and water contact angle are basically unchanged before and after aging, and it has strong temperature and salt resistance.

[0224] The sample solution prepared by the imbibing agent in Comparative Example 1 does not contain the gemini betaine surfactant. The oil-water interfacial tension of the sample solution prepared by the imbibing agent increases from 0.5 to 1.0 before and after aging, which is a large change, indicating that its temperature and salt resistance is insufficient.

[0225] In summary, the gemini betaine surfactant designed by the present invention has positive and negative double charges and strong salt resistance. The two hydrophilic groups and the two hydrophobic chains are linked together by chemical bonds with an alkylbenzene rigid group to enhance the stability of the system and enhance the temperature resistance. The gemini betaine surfactant of the present invention can make the imbibition agent have good temperature and salt resistance, and can significantly reduce the oil-water interfacial tension and water contact angle of the imbibition agent. The system performance after compounding is good, and it has good oil-water interfacial tension and wetting reversal ability, so that the imbibition agent has the characteristics of easy entry into the matrix pores, anti-adsorption, and strong wetting reversal ability, and can achieve a temperature resistance of 150°C and a salt resistance of 15×10 4 mg / L.

[0226] Experimental Example 2 Imbibition Recovery Experiment - Application of Heat-Resistant and Salt-Resistant Imbibition Agent

[0227] The heat-resistant and salt-resistant imbibition agents of Examples 1 to 11 and Comparative Example 1 were applied in the development of low-permeability oil reservoirs to test the imbibition recovery rate.

[0228] 1) Core preparation: prepare artificial sandstone cores, measure gas permeability and porosity; vacuum and pressurize the cores to saturate the formation crude oil, age them in a 90°C thermostat for more than 24 hours after saturation, weigh and record the mass of the saturated crude oil. 2) Place the saturated cores into a self-imbibition instrument containing the sample to be tested, allow the cores to self-absorb and discharge oil, and record the amount of oil discharged over time; when the volume of discharged oil does not change for 8 consecutive hours, record the total volume of discharged oil, and calculate the imbibition recovery rate; 3) Imbibition recovery efficiency / % = (mass of self-absorbed oil / mass of saturated crude oil) × 100%. The imbibition recovery rates of Examples 1 to 11 and Comparative Example 1 are shown in Table 2.

[0229] Table 2 Imbibition recovery data of Examples 1 to 11 and Comparative Example 1

[0230]

[0231] It can be seen from Table 2 that the recovery rates of the imbibition agents of Examples 1 to 11 are above 65.8%, and the recovery rate of the imbibition agent of Comparative Example 1 is 10.3%. It can be seen that the heat-resistant and salt-resistant imbibition agent provided by the present invention can significantly improve the recovery rate, and the recovery rate can reach above 65.8%.

[0232] The imbibition agent prepared by the present invention is heat and salt resistant, the temperature resistance can reach 150°C, and the salt resistance can reach 15×10 4 mg / L, which can meet the requirements of reservoir temperature ≤150℃ and mineralization ≤15×10 4 mg / L low permeability reservoir imbibition oil recovery technology requirements.

[0233] The above is a detailed description of the embodiment process, but it does not limit the technical solution of the present invention. Ordinary technicians in this field should understand that any modifications, partial replacements and variations can be made to the above-mentioned embodiments within the scope of the present invention, which should all be included in the required scope of the present invention.

Claims

1. A temperature-resistant and salt-resistant imbibition agent, It is characterized in that The heat-resistant and salt-resistant imbibition agent comprises: a gemini betaine surfactant and water; and also comprises one or two of a nonionic surfactant and a small molecule alcohol; The structural formula of the gemini betaine surfactant is: Wherein, R is a C12-C16 chain saturated alkane; The mass ratio of the gemini betaine surfactant, the nonionic surfactant and the small molecule alcohol is (0.1-0.5): (0.1-0.3): (0.1-0.2).

2. The heat-resistant and salt-resistant imbibition agent according to claim 1, It is characterized in that The nonionic surfactant is C8-C10 alkyl alcohol polyoxyethylene ether.

3. The heat-resistant and salt-resistant imbibition agent according to claim 1, It is characterized in that The small molecule alcohol is a monohydric or dihydric alcohol of C2 to C6.

4. The heat-resistant and salt-resistant imbibition agent according to claim 1, It is characterized in that In the heat-resistant and salt-resistant imbibing agent, the mass proportion of the gemini betaine surfactant is 0.1 to 0.5‰.

5. The heat-resistant and salt-resistant imbibition agent according to claim 1, It is characterized in that The preparation method of the heat-resistant and salt-resistant imbibition agent comprises the steps of preparing the gemini betaine surfactant and mixing the nonionic surfactant, the small molecule alcohol and water; the preparation method of the gemini betaine surfactant comprises: synthesizing p-phenylenediamine with formaldehyde and formic acid through Mannich reaction to obtain a tetramethyl ditertiary amine intermediate; the intermediate is then reacted with α-bromocarboxylic acid in the presence of an alkaline substance to generate; the α-bromocarboxylic acid has a general formula of RBrCHCOOH, wherein R is a C12-C16 chain saturated alkane.

6. The heat-resistant and salt-resistant imbibition agent according to claim 5, It is characterized in that The temperature for synthesizing the tetramethyl diamine intermediate is 50 to 80° C. and the time is 8 to 48 hours.

7. The heat-resistant and salt-resistant imbibition agent according to claim 6, It is characterized in that The molar ratio of p-phenylenediamine, formaldehyde and formic acid is (1-1.1): (2-2.2): (2.1-2.2).

8. The heat-resistant and salt-resistant imbibition agent according to claim 7, It is characterized in that The intermediate is reacted with α-bromocarboxylic acid at a temperature of 50-100° C., a time of 8-48 hours, and a pH of 8-10.

9. The heat-resistant and salt-resistant imbibition agent according to claim 8, It is characterized in that The molar ratio of p-phenylenediamine to α-bromocarboxylic acid is (1-1.1): (2-2.5).

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