Alkali-free composite oil-displacing agent composition, alkali-free composite oil-displacing agent and preparation method thereof

Abstract

The present invention relates to the technical field of oilfield composite flooding, and discloses an alkali-free composite flooding agent composition, an alkali-free composite flooding agent, and a preparation method thereof. The alkali-free composite flooding agent composition contains an acrylic acid polymer, a sulfonate surfactant, and a nonionic surfactant. The sulfonate surfactant is a product obtained by sequentially performing sulfonation and neutralization reactions on a second-line distillate oil, a tower bottom oil, and an alkylated derivative of a wash oil, and the interfacial tension of the sulfonate surfactant is not greater than 10 ‑2 The composition can produce an alkali-free composite oil displacement agent with ultra-low interfacial tension and high oil displacement efficiency without adding alkali.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield composite oil displacement technology, and in particular to an alkali-free composite oil displacement agent composition, an alkali-free composite oil displacement agent and a preparation method thereof. Background Art

[0002] Petroleum is a vital energy source. Compared to coal, it offers advantages such as higher energy density, easier transportation and storage, and lower atmospheric pollution after combustion. Liquefied petroleum gas and pipeline gas, derived from petroleum, are high-quality fuels for urban residents. Furthermore, petroleum fuels aircraft, tanks, ships, rockets, and other spacecraft.

[0003] Oil production refers to the process of digging for and extracting oil from existing reservoirs. It consists of three stages: primary recovery, which relies on the natural energy of the stratum; secondary recovery, which involves artificial water or gas injection; and tertiary recovery, which relies on physical and chemical methods. Tertiary recovery methods primarily include thermal flooding, miscible flooding, chemical flooding, and microbial flooding.

[0004] Chemical flooding is an oil recovery method that adds various chemicals to the injected water to improve the water's oil displacement and sweep performance, thereby increasing the crude oil recovery rate. The existing chemical flooding system is designed to achieve an ultra-low oil-water interfacial tension (10 -3 mN / m) to improve oil recovery, usually by adding high concentrations of alkali. However, the addition of alkali reduces the viscosity and viscoelasticity of the flooding system, affecting the mobility control ability of the composite oil-displacing agent. Furthermore, alkali reacts with the reservoir rock to produce severe scaling and reservoir damage. The resulting scale can deposit on the well bottom and on the screw pump, causing pump jams. Therefore, there is an urgent need to provide an alkali-free composite oil-displacing agent with low interfacial tension that can achieve high oil displacement efficiency while avoiding the impact of alkali on oil recovery. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problem that the alkali-free composite oil-displacing agent in the prior art cannot have both low interfacial tension and high oil displacement efficiency, and to provide an alkali-free composite oil-displacing agent composition, an alkali-free composite oil-displacing agent and a preparation method thereof.

[0006] In order to achieve the above object, the present invention provides an alkali-free composite oil displacement agent composition, which contains:

[0007] 5-15 parts by mass of acrylic polymer;

[0008] 3-9 parts by mass of sulfonate surfactant;

[0009] 1 part by mass of nonionic surfactant;

[0010] Optionally, the composition further contains 975-991 parts by mass of water;

[0011] Wherein, the number average molecular weight of the acrylic polymer is 20 million to 30 million;

[0012] The sulfonate surfactant is a product obtained by sequentially performing sulfonation reaction and neutralization reaction on the second-line distillate oil, tower bottom oil and wash oil alkylation derivative, and the interfacial tension of the sulfonate surfactant is not greater than 10 - 2 mN / m;

[0013] The nonionic surfactant is octylphenol polyoxyethylene ether and / or lauric acid diglycol amide.

[0014] Preferably, with respect to 1 part by mass of the nonionic surfactant, the content of the acrylic acid polymer is 8-10 parts by mass, and the content of the sulfonate surfactant is 6-9 parts by mass.

[0015] Preferably, the nonionic surfactant is a mixture of octylphenol polyoxyethylene ether and lauric acid diglycolamide in a mass ratio of 1-3:1.

[0016] Preferably, the alkyl content of the wash oil alkylated derivative is 25 wt%-65 wt%, and the relative average molecular weight of the wash oil alkylated derivative is 400-600.

[0017] Preferably, the wash oil alkylated derivative is obtained by alkylating the wash oil, wherein the wash oil has an aromatic content of 80wt%-95wt%, a relative average molecular weight of 450-550, and a kinematic viscosity of 15m at 50°C. 2 / s-20m 2 / s.

[0018] More preferably, the alkylation treatment conditions at least meet the following requirements: the alkylating agent is an olefin with 12-28 carbon atoms, the mass ratio of the wash oil to the alkylating agent is 1:0.4-0.8, the treatment temperature is 30°C-80°C, and the treatment time is 1h-8h.

[0019] Preferably, the aromatic content of the second-line distillate oil is 25wt%-40wt%, the relative average molecular weight is 290-360, and the kinematic viscosity at 50°C is 12m 2 / s-16m 2 / s.

[0020] Preferably, the aromatic content of the bottom oil is 70wt%-85wt%, the relative average molecular weight is 400-600, and the kinematic viscosity at 50°C is 14m 2 / s-18m 2 / s.

[0021] Preferably, the weight ratio of the second-line distillate oil, the bottom oil and the wash oil alkylated derivative for the sulfonation reaction is 2.3-9:0.6-2.4:1;

[0022] More preferably, the sulfonating agent of the sulfonation treatment is sulfur trioxide and / or chlorosulfonic acid, the molar ratio of the sulfonating agent to the second-line distillate oil is 1-1.5:1, the sulfonation reaction temperature is 50°C-80°C, and the time is 1h-4h.

[0023] Preferably, the neutralizing agent for the neutralization reaction is a sodium hydroxide solution, the mass concentration of the sodium hydroxide solution is 20wt%-40wt%, and the endpoint pH value of the neutralization reaction is 8-13.

[0024] Preferably, the acrylic polymer is one or more of polyacrylic acid, polymethacrylic acid, acrylic acid-hydroxypropyl acrylate copolymer, acrylic acid-sulfonate-amide copolymer, acrylic acid-acrylate-phosphonic acid-sulfonate tetrapolymer, acrylic acid-acrylate-sulfonate terpolymer, maleic acid-acrylic acid copolymer and carboxylate-sulfonate-acrylate terpolymer.

[0025] The second aspect of the present invention provides a method for preparing an alkali-free composite oil-displacing agent, which is carried out using the components of the above-mentioned alkali-free composite oil-displacing agent composition, comprising:

[0026] S1: mixing a sulfonate surfactant, a nonionic surfactant and a portion of water to obtain a surfactant mother solution;

[0027] and, mixing the acrylic acid polymer and the remaining portion of water to obtain an acrylic acid polymer mother solution;

[0028] S2: mixing the surfactant mother solution and the acrylic acid polymer mother solution to obtain an alkali-free composite oil displacement agent.

[0029] Preferably, in step S1, relative to 1 part by mass of the nonionic surfactant, the total amount of water used of the part of water and the remaining part of water is 975-991 parts by mass, and the amount of the part of water accounts for 50wt%-70wt% of the total amount of water used.

[0030] The third aspect of the present invention provides an alkali-free composite oil-displacing agent prepared from the above-mentioned alkali-free composite oil-displacing agent composition or an alkali-free composite oil-displacing agent prepared by the above-mentioned preparation method.

[0031] In the alkali-free composite oil-displacing agent composition provided in the first aspect of the present invention, a specific sulfonate surfactant, an anionic surfactant, and an acrylic polymer with a number-average molecular weight of 20 million to 30 million are compounded in a specific ratio. The components synergistically enhance the effect, thereby producing an alkali-free composite oil-displacing agent with ultra-low interfacial tension and high oil displacement efficiency.

[0032] The preparation method provided in the second aspect of the present invention uses the alkali-free composite oil-displacing agent composition provided in the first aspect of the present invention, and in accordance with a specific mixing order, the prepared alkali-free composite oil-displacing agent has both ultra-low interfacial tension and high oil displacement efficiency.

[0033] The alkali-free composite oil displacement agent provided in the third aspect of the present invention can not only avoid the problems of formation damage, reduced reservoir permeability, severe emulsification of produced fluid, and difficulty in separation caused by alkali, but also has ultra-low interfacial tension and high oil displacement efficiency. DETAILED DESCRIPTION

[0034] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0035] As mentioned above, the first aspect of the present invention provides an alkali-free composite oil displacement agent composition, which comprises:

[0036] 5-15 parts by mass of acrylic polymer;

[0037] 3-9 parts by mass of sulfonate surfactant;

[0038] 1 part by mass of nonionic surfactant;

[0039] Optionally, the composition further contains 975-991 parts by mass of water;

[0040] Wherein, the number average molecular weight of the acrylic polymer is 20 million to 30 million;

[0041] The sulfonate surfactant is a product obtained by sequentially performing sulfonation reaction and neutralization reaction on the second-line distillate oil, tower bottom oil and wash oil alkylation derivative, and the interfacial tension of the sulfonate surfactant is not greater than 10 - 2 mN / m;

[0042] The nonionic surfactant is octylphenol polyoxyethylene ether and / or lauric acid diglycol amide.

[0043] In the alkali-free composite oil-displacing agent composition provided by the present invention, a specific sulfonate surfactant, an anionic surfactant, and an acrylic polymer with a number-average molecular weight of 20 million to 30 million are compounded in a specific ratio to produce a synergistic effect. The resulting alkali-free composite oil-displacing agent can avoid problems such as formation damage, reduced reservoir permeability, severe emulsification of produced fluids, and difficulty in separation caused by the addition of alkali, and can also produce ultra-low interfacial tension and have excellent emulsification properties, thereby achieving good oil displacement efficiency.

[0044] According to some preferred embodiments of the present invention, the acrylic acid polymer is present in an amount of 8-10 parts by mass, and the sulfonate surfactant is present in an amount of 6-9 parts by mass, per 1 part by mass of the nonionic surfactant. More preferably, the sulfonate surfactant is present in an amount of 7-8 parts by mass, per 1 part by mass of the nonionic surfactant. Under these preferred conditions, the swept volume of the alkali-free composite oil-displacing agent can be further increased, thereby improving the oil displacement efficiency of the alkali-free composite oil-displacing agent.

[0045] According to some particularly preferred embodiments of the present invention, the nonionic surfactant is a mixture of octylphenol polyoxyethylene ether and lauric acid diglycolamide in a mass ratio of 1-3:1. Under these preferred conditions, the resulting article has lower interfacial tension and higher oil displacement efficiency as an oil displacement agent.

[0046] According to some preferred embodiments of the present invention, the alkyl content of the wash oil alkylated derivative is 25 wt% to 65 wt%, and the relative average molecular weight of the wash oil alkylated derivative is 400 to 600. Under these preferred conditions, the sulfonate-type surfactant prepared has a stronger synergistic effect when compounded with other components, thereby producing an alkali-free composite oil displacement agent with higher oil displacement efficiency.

[0047] According to some preferred embodiments of the present invention, the wash oil alkylated derivative is obtained by alkylating the wash oil, wherein the wash oil has an aromatic content of 80wt%-95wt%, a relative average molecular weight of 450-550, and a kinematic viscosity of 15m at 50°C. 2 / s-20m 2 The wash oil alkylation derivative prepared under the preferred conditions can produce a sulfonate surfactant that is more suitable for the alkali-free composite oil displacement agent composition system provided by the present invention.

[0048] More preferably, the alkylation treatment conditions at least meet the following requirements: the alkylating agent is an olefin with 12-28 carbon atoms, the mass ratio of the wash oil to the alkylating agent is 1:0.4-0.8, the treatment temperature is 30°C-80°C, and the treatment time is 1-8 hours. The sulfonate surfactant produced under these preferred conditions exhibits stronger synergistic effects when combined with other components, resulting in an alkali-free composite oil-displacement agent with higher oil displacement efficiency.

[0049] According to some preferred embodiments of the present invention, the aromatic content of the second-line distillate oil is 25wt%-40wt%, the relative average molecular weight is 290-360, and the kinematic viscosity at 50°C is 12m 2 / s-16m 2 The sulfonate surfactant prepared from the second-line distillate oil under the preferred conditions can be compounded with other components to produce an alkali-free composite oil displacement agent with higher oil displacement efficiency.

[0050] According to some preferred embodiments of the present invention, the aromatic content of the bottom oil is 70wt%-85wt%, the relative average molecular weight is 400-600, and the kinematic viscosity at 50°C is 14m 2 / s-18m 2 The sulfonate surfactant prepared from the bottom oil under the preferred conditions and compounded with other components to obtain an alkali-free composite oil displacement agent have higher oil displacement efficiency.

[0051] According to some preferred embodiments of the present invention, the weight ratio of the second-line distillate oil, the tower bottoms oil, and the wash oil alkylated derivative subjected to the sulfonation reaction is 2.3-9:0.6-2.4:1. The sulfonate surfactant produced under these preferred conditions exhibits superior performance, and the resulting alkali-free composite oil displacement agent, when combined with other components, exhibits higher oil displacement efficiency.

[0052] Further preferably, the sulfonating agent used in the sulfonation treatment is sulfur trioxide and / or chlorosulfonic acid, the molar ratio of the sulfonating agent to the second-line distillate oil is 1-1.5:1, and the sulfonation reaction temperature is 50°C-80°C, and the reaction time is 1-4 hours. Under these preferred conditions, the resulting sulfonate-type surfactant exhibits even better performance.

[0053] Further preferably, the neutralizing agent in the neutralization reaction is a sodium hydroxide solution, the mass concentration of the sodium hydroxide solution is 20wt%-40wt%, and the endpoint pH value of the neutralization reaction is 8-13. Under these preferred conditions, an excellent sulfonate surfactant can be produced without wasting sodium hydroxide solution, which is economical and environmentally friendly.

[0054] According to some preferred embodiments of the present invention, the acrylic polymer is one or more of polyacrylic acid, polymethacrylic acid, acrylic acid-hydroxypropyl acrylate copolymer, acrylic acid-sulfonate-amide copolymer, acrylic acid-acrylate-phosphonic acid-sulfonate tetrapolymer, acrylic acid-acrylate-sulfonate terpolymer, maleic acid-acrylic acid copolymer and carboxylate-sulfonate-acrylate terpolymer.

[0055] Preferably, the acrylic polymer is one or more of polyacrylic acid, polymethacrylic acid, acrylic acid-hydroxypropyl acrylate copolymer, acrylic acid-acrylate-sulfonate terpolymer and maleic acid-acrylic acid copolymer.

[0056] It should be noted that the present invention has no particular limitation on the source of the acrylic polymer, and any commercially available product in the art may be used.

[0057] It should be noted that the water used in the alkali-free composite oil-displacing agent composition is not particularly limited in the present invention. Exemplarily, the water may be deionized water, mineral-containing water, or the like. The mineral-containing water may be tap water, river water, or oilfield injection water. However, for environmental and economic reasons, oilfield injection water is preferred.

[0058] The second aspect of the present invention provides a method for preparing an alkali-free composite oil-displacing agent, which is carried out using the components of the above-mentioned alkali-free composite oil-displacing agent composition, comprising:

[0059] S1: mixing a sulfonate surfactant, a nonionic surfactant and a portion of water to obtain a surfactant mother solution;

[0060] and, mixing the acrylic acid polymer and the remaining portion of water to obtain an acrylic acid polymer mother solution;

[0061] S2: mixing the surfactant mother solution and the acrylic acid polymer mother solution to obtain an alkali-free composite oil displacement agent.

[0062] Preferably, in step S1, relative to 1 part by mass of the nonionic surfactant, the total amount of water used of the part of water and the remaining part of water is 975-991 parts by mass, and the amount of the part of water accounts for 50wt%-70wt% of the total amount of water used.

[0063] The preparation method provided in the second aspect of the present invention uses the alkali-free composite oil-displacing agent composition provided in the first aspect of the present invention to prepare an alkali-free composite oil-displacing agent with ultra-low interfacial tension and high oil displacement efficiency.

[0064] The third aspect of the present invention provides an alkali-free composite oil-displacing agent prepared from the above-mentioned alkali-free composite oil-displacing agent composition or an alkali-free composite oil-displacing agent prepared by the above-mentioned preparation method.

[0065] The present invention will be described in detail below through examples. In the following examples, 1 part by mass represents 1 g. The amount of substance, M, of the second-tier distillate oil is calculated as: M = mass / relative average molecular weight. In the following examples, normal temperature and pressure refer to room temperature (25°C) and 0.1013 MPa. Interfacial tension is measured using an interfacial tensiometer purchased from Beijing Shengwei Jiye Technology Co., Ltd.

[0066] Acrylic polymer A (hereinafter referred to as BA): polymethacrylic acid, number average molecular weight 20 million, purchased from Heilongjiang Jidi Oilfield Services Co., Ltd.

[0067] Acrylic acid polymer B (hereinafter referred to as BB): acrylic acid-hydroxypropyl acrylate copolymer, number average molecular weight 25 million, purchased from Heilongjiang Jidi Oilfield Services Co., Ltd.

[0068] Nonionic surfactant A (hereinafter referred to as FA): octylphenol polyoxyethylene ether, purchased from Hai'an Petrochemical Plant, Jiangsu Province;

[0069] Nonionic surfactant B (hereinafter referred to as FB): lauric acid diglycol amide, homemade, 95 wt%, obtained by condensation reaction of lauric acid and diglycolamine;

[0070] Nonionic surfactant C (hereinafter referred to as FC): prepared by mixing the octylphenol polyoxyethylene ether and the lauric acid diglycolamide in a mass ratio of 2:1 at room temperature and pressure;

[0071] Sulfonate surfactant A (hereinafter referred to as HA): interfacial tension is 3.7×10 -3 mN / m, obtained by mixing second-line distillate oil A, tower bottom oil A, and wash oil alkylated derivative A in a weight ratio of 4:1:1.2, followed by sulfonation reaction and neutralization reaction, wherein the conditions for the sulfonation reaction are: the sulfonating agent is liquid sulfur trioxide (analytical grade), and the molar ratio of the liquid sulfur trioxide to the second-line distillate oil A is 1.2:1; the conditions for the neutralization reaction are: the neutralizing agent is a sodium hydroxide solution with a mass concentration of 30wt%, and the endpoint pH value is 10;

[0072] Sulfonate surfactant B (hereinafter referred to as HB): interfacial tension is 9.5×10 -3 mN / m, obtained by sequentially subjecting a second-line distillate oil A, a tower bottom oil A, and a wash oil alkylated derivative A to sulfonation and neutralization, wherein the sulfonation reaction conditions are as follows: the sulfonating agent is liquid sulfur trioxide (analytical grade), and the molar ratio of the liquid sulfur trioxide to the second-line distillate oil A is 0.9:1; the neutralization reaction conditions are as follows: the neutralizing agent is a sodium hydroxide solution with a mass concentration of 10 wt%, and the endpoint pH value is 7;

[0073] Sulfonate surfactant C (hereinafter referred to as HC): interfacial tension is 2.6×10 -2 mN / m, obtained by sequentially subjecting a second-line distillate oil B, a tower bottom oil B, and a wash oil alkylated derivative B to a sulfonation reaction and a neutralization reaction, wherein the conditions for the sulfonation reaction are: the sulfonating agent is liquid sulfur trioxide (analytical grade), and the molar ratio of the liquid sulfur trioxide to the second-line distillate oil B is 0.9:1; the conditions for the neutralization reaction are: the neutralizing agent is a sodium hydroxide solution with a mass concentration of 10wt%, and the endpoint pH value is 7;

[0074] Second-tier distillate oil A: aromatic content is 35wt%-40wt%, relative average molecular weight is 320-360, kinematic viscosity at 50℃ is 14m 2 / s-16m 2 / s, purchased from Daqing Refining and Chemical Company;

[0075] Second-tier distillate oil B: aromatic content is 18wt%-24wt%, relative average molecular weight is 280-310, kinematic viscosity at 50℃ is 10m 2 / s-12m 2 / s, purchased from Daqing Petrochemical Company;

[0076] Bottom oil A: aromatic content is 75wt%-85wt%, relative average molecular weight is 500-600, kinematic viscosity at 50℃ is 16m 2 / s-18m 2 / s, purchased from Daqing Refining and Chemical Company;

[0077] Bottom oil B: aromatic content is 60wt%-68wt%, relative average molecular weight is 380-480, kinematic viscosity at 50℃ is 12m 2 / s-14m 2 / s, purchased from Daqing Petrochemical Company;

[0078] Wash oil alkylated derivative A: alkyl content of 53wt%, relative average molecular weight of 560, obtained by alkylation treatment of wash oil; the wash oil has an aromatic content of 80wt%-90wt%, a relative average molecular weight of 450-500, and a kinematic viscosity of 15m at 50°C 2 / s-18m 2 / s, purchased from Heilongjiang Baotailong Coal Chemical Group; the alkylation treatment conditions are as follows: the alkylating agent is n-hexadecene, the mass ratio of the wash oil to the alkylating agent is 1:0.6, the treatment temperature is 50°C, and the treatment time is 4h;

[0079] Wash oil alkylated derivative B: alkyl content of 20wt%, relative average molecular weight of 380, obtained by alkylation treatment of wash oil; the wash oil has an aromatic content of 65wt%-75wt%, a relative average molecular weight of 350-400, and a kinematic viscosity of 10m at 50°C 2 / s-13m 2 / s, the alkylation treatment conditions are: the alkylating agent is n-decene, the mass ratio of the wash oil to the alkylating agent is 1:0.2, the treatment temperature is 50°C, and the treatment time is 4 hours.

[0080] Example 1

[0081] Preparation of alkali-free composite oil displacement agent:

[0082] S1: mixing a sulfonate surfactant, a nonionic surfactant and a portion of water to obtain a surfactant mother solution;

[0083] and, mixing the acrylic acid polymer and the remaining portion of water to obtain an acrylic acid polymer mother solution;

[0084] S2: mixing the surfactant mother solution and the acrylic acid polymer mother solution to obtain an alkali-free composite oil displacement agent.

[0085] The mixing in step S1 and step S2 is performed at room temperature and pressure. Specifically, the parameters are shown in Table 1 below.

[0086] Example 2

[0087] The method of Example 1 was followed, except that the group distribution ratio was changed. Specifically, the parameters are shown in Table 1 below.

[0088] Example 3

[0089] The method of Example 1 was followed, except that the component ratio and the types of nonionic surfactant and acrylic polymer were changed. Specifically, the parameters are shown in Table 1 below.

[0090] Example 4

[0091] The method of Example 1 was followed, except that the component ratio and the types of nonionic surfactant and acrylic polymer were changed. Specifically, the parameters are shown in Table 1 below.

[0092] Example 5

[0093] The method of Example 2 was followed, except that the type of sulfonate surfactant was changed. Specifically, the parameters are shown in Table 1 below.

[0094] Example 6

[0095] The method of Example 4 was followed, except that the type of sulfonate surfactant was changed. Specifically, the parameters are shown in Table 1 below.

[0096] Example 7

[0097] The method of Example 1 was followed, except that the type of nonionic surfactant was changed. Specifically, the parameters are shown in Table 1 below.

[0098] Comparative Example 1

[0099] The method of Example 2 was followed, except that the type of sulfonate surfactant was changed. Specifically, the parameters are shown in Table 1 below.

[0100] Comparative Example 2

[0101] The method of Example 3 was followed, except that no nonionic surfactant was added and the component ratio was changed. Specifically, the parameters are shown in Table 1 below.

[0102] Comparative Example 3

[0103] The method of Example 3 was followed, except that the sulfonate surfactant was not added and the component ratio was changed. Specifically, the parameters are shown in Table 1 below.

[0104] Comparative Example 4

[0105] The method of Example 3 was followed, except that the group distribution ratio was changed. Specifically, the parameters are shown in Table 1 below.

[0106] Comparative Example 5

[0107] The method of Example 3 was followed, except that the component ratio and the type of nonionic surfactant were changed. Specifically, the parameters are shown in Table 1 below.

[0108] Table 1

[0109]

[0110] Table 1 (Continued)

[0111]

[0112]

[0113] Table 1 (Continued)

[0114]

[0115] The alkali-free composite oil-displacing agents prepared in the above examples and comparative examples were subjected to performance tests according to SY / T 6424-2014 "Compound Oil Displacing System Performance Test Methods". The test results are shown in Table 2 below:

[0116] Table 2

[0117] Interfacial tension (mN / m) Oil displacement efficiency (%) L1 0.0026 70 L2 0.0028 68 L3 0.0035 65 L4 0.0030 69 L5 0.0047 60 L6 0.0043 62 L7 0.0012 78 DL1 0.0086 45 DL2 0.0068 51 DL3 0.0083 48 DL4 0.0059 55 DL5 0.0062 53

[0118] It can be seen from the results in Table 1 and Table 2 that the alkali-free composite oil-displacing agent prepared by the method described in the embodiment of the present invention can achieve ultra-low interfacial tension and high oil-displacing efficiency.

[0119] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. An alkali-free composite oil-displacing agent composition, characterized in that: The composition contains: 5-15 parts by mass of acrylic polymer; 3-9 parts by mass of sulfonate surfactant; 1 part by mass of nonionic surfactant; Optionally, the composition further contains 975-991 parts by mass of water; Wherein, the number average molecular weight of the acrylic polymer is 20 million to 30 million; The acrylic polymer is at least one of polyacrylic acid, polymethacrylic acid, and acrylic acid-hydroxypropyl acrylate copolymer; The sulfonate surfactant is a product obtained by sequentially performing sulfonation and neutralization reactions on the second-line distillate oil, tower bottom oil and wash oil alkylation derivatives, and the interfacial tension of the sulfonate surfactant is not greater than 10 -2 mN / m; The wash oil alkylated derivative is obtained by alkylating the wash oil. The wash oil has an aromatic content of 80wt%-95wt%, a relative average molecular weight of 450-550, and a kinematic viscosity of 15m at 50°C. 2 / s-20m 2 / s; the conditions of the alkylation treatment at least meet the following requirements: the alkylating agent is an olefin with a carbon number of 12-28, the mass ratio of the wash oil to the alkylating agent is 1:0.4-0.8, the treatment temperature is 30°C-80°C, and the treatment time is 1h-8h; The aromatic content of the second-line distillate oil is 25wt%-40wt%, the relative average molecular weight is 290-360, and the kinematic viscosity at 50°C is 12m 2 / s-16m 2 / s; The aromatic content of the bottom oil is 70wt%-85wt%, the relative average molecular weight is 400-600, and the kinematic viscosity at 50°C is 14m 2 / s-18m 2 / s; The weight ratio of the second-line distillate oil, the bottom oil and the wash oil alkylated derivative for the sulfonation reaction is 2.3-9:0.6-2.4:1; The sulfonating agent of the sulfonation reaction is sulfur trioxide and / or chlorosulfonic acid, the molar ratio of the sulfonating agent to the second-line distillate oil is 1-1.5:1, the temperature of the sulfonation reaction is 50° C.-80° C., and the time is 1 hour-4 hours; The nonionic surfactant is a mixture of octylphenol polyoxyethylene ether and lauric acid diglycolamide in a mass ratio of 1-3:

1.

2. The alkali-free composite oil-displacing agent composition according to claim 1, characterized in that The content of the acrylic acid polymer is 8-10 parts by mass, and the content of the sulfonate surfactant is 6-9 parts by mass per 1 part by mass of the nonionic surfactant.

3. The alkali-free composite oil-displacing agent composition according to claim 1 or 2, characterized in that The neutralizing agent for the neutralization reaction is a sodium hydroxide solution, the mass concentration of the sodium hydroxide solution is 20wt%-40wt%, and the endpoint pH value of the neutralization reaction is 8-13.

4. A method for preparing an alkali-free composite oil-displacing agent, characterized in that: The method is carried out using the components of the alkali-free composite oil displacement agent composition according to any one of claims 1 to 3, comprising: S1: mixing a sulfonate surfactant, a nonionic surfactant and a portion of water to obtain a surfactant mother solution; and, mixing the acrylic acid polymer and the remaining portion of water to obtain an acrylic acid polymer mother solution; S2: mixing the surfactant mother solution and the acrylic acid polymer mother solution to obtain an alkali-free composite oil displacement agent.

5. The preparation method according to claim 4, characterized in that In step S1, relative to 1 part by mass of the nonionic surfactant, the total amount of water used of the part of water and the remaining part of water is 975-991 parts by mass, and the amount of the part of water accounts for 50wt%-70wt% of the total amount of water used.

6. An alkali-free composite oil-displacing agent prepared from the alkali-free composite oil-displacing agent composition according to any one of claims 1 to 3 or an alkali-free composite oil-displacing agent prepared by the preparation method according to claim 4 or 5.

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