Binary composite system oil-displacing agent, preparation method and application

Abstract

The invention belongs to the technical field of oil-displacing agents, and particularly relates to a binary composite system oil-displacing agent, a preparation method and application. The binary composite system oil displacement agent is prepared from the following raw materials in percentage by weight: 0.05 to 0.15 percent of lauryl alcohol polyoxyethylene ether sodium sulfate, 0.3 to 0.5 percent of a double-tailed hydrophobic association polymer and saline water, the double-tailed hydrophobic associated polymer is prepared by the following steps: reacting di-isocyanate alkyl acid alkyl ester with organic amine to prepare a double-tailed hydrophobic compound, and grafting the double-tailed hydrophobic compound onto a copolymer through ester exchange reaction, and copolymer polymeric monomers comprise acrylamide, unsaturated sulfonic acid and hydroxyl acrylate in a molar ratio of (80-90): (10-20): (0.5-3); the mass ratio of the double-tailed hydrophobic compound to the copolymer is (5-15): 100. Double-tailed hydrophobic groups form an association network, so that the emulsification oil-carrying capacity and viscosity are improved; the sulfo group and the amido group enhance hydrophilicity and calcium and magnesium tolerance, and inhibit viscosity loss under high salt; and a polyoxyethylene chain segment forms a hydration protection layer outside the associated micro-region, so that low interfacial tension, strong emulsification oil carrying and excellent salt tolerance are realized.

Description

Technical Field

[0001] This invention belongs to the field of oil displacement agent technology, specifically relating to a binary composite system oil displacement agent, its preparation method, and its application. Background Technology

[0002] With the rapid development of my country's economy, the demand for energy from all sectors of society is increasing. Although the country has increased its investment in new energy sources such as nuclear power and solar energy, oil, as a traditional energy source, still occupies an extremely important position. At present, my country's major large and medium-sized oil fields are in the middle and late stages of exploitation, with some oil fields suffering from severe aging, an overall water cut exceeding 85%, declining recovery rates, and a general trend of decreasing oil field production capacity.

[0003] Chemical flooding is an oil recovery method that involves adding chemical agents to the injected water to enhance oil recovery. These added chemical agents are often referred to as oil displacement agents. Oil displacement agents increase the viscosity of the injected water, reduce the interfacial tension between oil and water, and alter the permeability of parts of the oil layer, thereby either increasing the sweep efficiency or improving the oil washing efficiency, ultimately achieving the goal of increasing oil recovery. Depending on the type of chemical agent used for oil displacement, chemical flooding is classified into: alkaline flooding, surfactant flooding, polymer flooding, and later, polymer / surfactant / alkaline ternary composite flooding and alkali-free polymer / surfactant binary composite flooding, developed to address the shortcomings and drawbacks of low efficiency and high cost associated with single chemical agents. Among these, alkali-free polymer / surfactant binary composite flooding is more widely used because it avoids the low efficiency problem of single chemical agents and eliminates the problems of oil layer scaling and polymer viscosity reduction caused by the addition of alkali. For example, patent CN108314998B discloses a hydrophobic associating polymer-surfactant binary combination. The oil recovery system and its composite flooding system utilize a binary composite flooding composition of hydrophobic associating polymer and surfactant, comprising the following components: 1) a hydrophobic associating polymer containing acrylamide units and hydrophobic monomer units; 2) a composite surfactant comprising a mass ratio of fatty amide betaine: alkyl betaine: aromatic acid salt = (1-60):(1-60):(20-60); wherein the mass ratio of the hydrophobic associating polymer to the composite surfactant is (0.5-3):(0.1-5). This binary composite flooding composition can achieve low interfacial tension, but the oil displacement agent has low emulsification ability, poor oil carrying capacity, and limited recovery improvement. CN102876313B discloses a hydrophobic associating polymer-composite surfactant binary composite flooding system and method, the main components and contents (wt%) of which are: hydrophobic associating polymer: 0.08-0.3, composite surfactant: 0.05-0.5, water: 99.2-99.87. The composition and content (wt%) of the composite surfactant are: fatty acid diester disulfonate 50-70, oleic acid diethanolamide 30-50. This binary composite flooding system is alkali-free and environmentally friendly, and has the advantages of high interfacial activity and significant synergistic effect. However, Ca...2+ Mg 2+ Carrying two positive charges, it can simultaneously form ionic bonds with the two sulfonate groups in the molecular structure of fatty acid diester disulfonate, generating water-insoluble calcium / magnesium fatty acid diester disulfonate precipitates. This disrupts the molecular structure and micellar state of the surfactant, causing it to lose its interfacial activity, which in turn leads to a significant increase in oil-water interfacial tension, limiting its application in high-calcium and magnesium oil reservoirs.

[0004] Therefore, it is necessary to develop an alkali-free binary composite oil displacement agent that combines excellent interfacial activity and strong emulsifying ability with good tolerance to calcium and magnesium ions. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a binary composite system oil displacement agent, its preparation method, and its application. The binary composite system oil displacement agent of this invention comprises a double-tailed hydrophobic associating polymer and sodium lauryl polyoxyethylene ether sulfate. The double-tailed hydrophobic associating polymer is first prepared by reacting a diisocyanate alkyl acid alkyl ester with an organic amine to obtain a double-tailed hydrophobic compound. Then, the double-tailed hydrophobic compound is grafted onto a copolymer obtained by copolymerizing acrylamide, unsaturated sulfonic acid, and hydroxy acrylate. The double-tailed hydrophobic groups can form a strong associative network, enhancing the system's emulsifying and oil-carrying capacity. Force and solution viscosity; sulfonic acid groups and amide groups can enhance molecular hydrophilicity and tolerance to calcium and magnesium ions, inhibiting molecular aggregation and viscosity loss under high salt conditions; sodium lauryl ether sulfate and the associative microregions of the double-tailed hydrophobic associative polymer have suitable hydrophobic affinity and steric hindrance matching effect, which can stably arrange the polyoxyethylene segments on the periphery of the hydrophobic associative microregions, without intruding into the interior of the associative microregions and destroying the associative network, thus ensuring the stability of the system viscosity and emulsification performance; at the same time, it can form a hydration protective layer by relying on the hydration of polyoxyethylene segments to shield against Ca. 2+ Mg 2+ It avoids adverse effects on the polymer and itself, prevents component instability or precipitation, and enables the system to simultaneously possess ultra-low interfacial tension, strong emulsification and oil carrying capacity, and excellent calcium and magnesium ion tolerance.

[0006] To achieve the above objectives, the following technical solution is adopted:

[0007] A binary composite system oil displacement agent comprises the following raw materials in percentage: 0.05-0.15 wt% sodium lauryl polyoxyethylene ether sulfate, 0.3-0.5 wt% a double-tailed hydrophobic associating polymer, and the remainder being brine. The double-tailed hydrophobic associating polymer is prepared by a method comprising: reacting a diisocyanate alkyl acid alkyl ester with an organic amine to obtain a double-tailed hydrophobic compound, and then grafting the double-tailed hydrophobic compound onto a copolymer via transesterification. The copolymer comprises acrylamide, unsaturated sulfonic acid, and hydroxyacrylate in a molar ratio of 80-90:10-20:0.5-3; and the mass ratio of the double-tailed hydrophobic compound to the copolymer is 5-15:100.

[0008] The molar ratio of the diisocyanate alkyl acid alkyl ester and the organic amine is 1:2.04-2.08.

[0009] The diisocyanate-alkyl acid alkyl ester is selected from one or a combination of two of L-lysine diisocyanate and methyl 2,6-diisocyanate hexanoate. The organic amine is selected from at least one of C4-C10 fatty amines and C4-C10 alkylanilines.

[0010] The C4-C10 alkylaniline is selected from at least one of 4-n-butylaniline, 4-n-pentylaniline, 4-n-hexylaniline, 4-n-heptylaniline, 4-n-octylaniline, 4-n-nonylaniline, and 4-n-decylaniline; the C4-C10 aliphatic amine is selected from at least one of n-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, and n-decylamine.

[0011] The molar ratio of acrylamide, unsaturated sulfonic acid, and hydroxyacrylate is 80-90:10-20:0.5-3, preferably 80-90:10-20:1.5-3. The viscosity-average molecular weight of the copolymer is 18 million to 22 million.

[0012] The hydroxyacrylate is selected from at least one of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, and hydroxybutyl acrylate.

[0013] The unsaturated sulfonic acid is selected from at least one of 2-acrylamido-2-methylpropanesulfonic acid, allyl sulfonic acid, styrene sulfonic acid, and methacrylic sulfonic acid.

[0014] The mass ratio of the dual-tailed hydrophobic compound to the copolymer is 10-15:100.

[0015] The dual-tailed hydrophobic associative polymer is prepared by a method comprising the following steps:

[0016] 1) Dissolve the alkyl ester of diisocyanate in an anhydrous organic solvent, add an organic amine solution dropwise under temperature-controlled stirring, and keep the reaction at the temperature to obtain a double-tailed hydrophobic compound;

[0017] 2) Under an inert atmosphere, acrylamide, unsaturated sulfonic acid, and hydroxy acrylate are added to water and mixed to obtain a monomer solution. The pH of the monomer solution is adjusted to 6.5-7.5, the initiator is added and the reaction is carried out under controlled temperature to obtain a copolymer.

[0018] 3) Dissolve the copolymer, the double-tailed hydrophobic compound, and the catalyst in an organic solvent, and heat to reflux to react, to obtain the double-tailed hydrophobic associative polymer.

[0019] In step 1), the anhydrous organic solvent is selected from at least one of anhydrous chlorobenzene, anhydrous N,N-dimethylformamide, anhydrous dimethyl sulfoxide, anhydrous ethyl acetate, and anhydrous chloroform. The molar volume ratio of the diisocyanate alkyl acid alkyl ester to the organic solvent is 0.5-2 mol / L. The temperature-controlled stirring conditions are a controlled temperature of 0-25℃ and a stirring speed of 500-800 rpm. The concentration of the organic amine solution is 0.5-2 mol / L. The solvent of the organic amine solution is selected from at least one of diethyl ether, tetrahydrofuran, acetone, carbon tetrachloride, chlorobenzene, benzene, and toluene. The dropping rate of the organic amine solution is 0.5-1.0 mL / min. The heat preservation reaction is carried out at 0-25℃ for 0.5-2 h. After the reaction, the process includes washing with 0.1-0.5 mol / L hydrochloric acid, separation, washing the organic phase with saturated sodium bicarbonate until the pH of the separated aqueous phase is 7, vacuum distillation, and column chromatography post-treatment. The eluent used for column chromatography is a mixture of ethyl acetate and petroleum ether in a volume ratio of 5-10:1.

[0020] In step 2), the amount of water used is such that the solid content of the monomer solution is 10-20%. The heating reaction is carried out at 40-80℃ for 5-12 hours. The initiator is selected from at least one of redox initiators and azo initiators. Preferably, the initiator is a redox initiator composed of an oxidant and a reducing agent in a mass ratio of 1-3:1. The oxidant is selected from at least one of potassium persulfate, ammonium persulfate, and sodium persulfate. The reducing agent is selected from at least one of sodium bisulfite, potassium bisulfite, and sodium thiosulfate. The oxidant and reducing agent are added dropwise by preparing oxidant solutions and reducing agent solutions respectively. The dropwise addition time is 0.5-1.5 hours. The concentration of the oxidant solution is 1-3 g / 100 mL, and the concentration of the reducing agent solution is 1-3 g / 100 mL. The redox initiator is 0.003-0.008 wt% of the sum of the mass of acrylamide, unsaturated sulfonic acid, and hydroxyacrylate. After the reaction is completed, the process also includes shearing, granulation, drying, pulverizing, alcohol washing, and post-drying treatment. The alcohol washing involves washing 1-3 times with at least one of methanol, ethanol, and propanol.

[0021] The organic solvent in step 3) is selected from at least one of DMF, DMSO, and NMP. The catalyst is selected from at least one of p-toluenesulfonic acid and sodium formate. The amount of catalyst used is 0.1-0.3 wt% of the copolymer. The reflux reaction time is 5-8 h. After the reaction is completed, the reaction also includes precipitation in anhydrous ethanol, filtration, washing with anhydrous ethanol, and vacuum drying to constant weight.

[0022] The sodium lauryl ether sulfate is selected from at least one of sodium lauryl ether-8 sulfate, sodium lauryl ether-7 sulfate, and sodium lauryl ether-5 sulfate.

[0023] The total mineralization of the brine is 5000-30000 mg / L, and the total content of calcium and magnesium ions is 0-3000 mg / L.

[0024] The present invention also provides a method for preparing the above-mentioned binary composite system oil displacement agent, comprising the following steps: adding a hydrophobic associating polymer to brine to dissolve, and adding sodium lauryl polyoxyethylene ether sulfate to dissolve to obtain a binary composite system oil displacement agent.

[0025] Application of a binary composite system oil displacement agent, wherein the binary composite system oil displacement agent is used for tertiary oil recovery.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] The binary composite system oil displacement agent of this invention includes a double-tailed hydrophobic associating polymer and sodium lauryl polyoxyethylene ether sulfate. The double-tailed hydrophobic associating polymer is first prepared by reacting a diisocyanate alkyl acid alkyl ester with an organic amine to obtain a double-tailed hydrophobic compound. Then, the double-tailed hydrophobic compound is grafted onto a copolymer obtained by copolymerizing acrylamide, unsaturated sulfonic acid, and hydroxy acrylate. The double-tailed hydrophobic groups can form a strong associative network, improving the system's emulsifying oil-carrying capacity and solution viscosity. The sulfonic acid groups and amide groups can enhance the separation... The hydrophilicity and tolerance to calcium and magnesium ions inhibit molecular aggregation and viscosity loss under high salt conditions. The suitable hydrophobic affinity and steric hindrance matching effect between the associative microregions of sodium lauryl ether sulfate and the double-tailed hydrophobic associative polymer allow the polyoxyethylene segments to be stably arranged on the periphery of the hydrophobic associative microregions. This prevents them from penetrating the interior of the associative microregions and disrupting the associative network, ensuring stable viscosity and emulsification properties of the system. Furthermore, the hydration of the polyoxyethylene segments forms a hydration protective layer, shielding against calcium and magnesium ions. 2+ Mg 2+ It avoids adverse effects on the polymer and itself, prevents component instability or precipitation, and enables the system to simultaneously possess ultra-low interfacial tension, strong emulsification and oil carrying capacity, and excellent calcium and magnesium ion tolerance. Detailed Implementation

[0028] The present invention will be further described below with reference to specific embodiments, but is not limited to the contents of the specification. Unless otherwise specified, all "parts" mentioned in the embodiments of the present invention are parts by weight. All reagents used are commercially available in the art.

[0029] Viscosity-average molecular weight: The viscosity-average molecular weight of copolymers and dual-tailed hydrophobic associative polymers was measured and calculated in accordance with the calculation method of viscosity-average relative molecular mass in the technical requirements for polymers used in oil displacement SY / T 5862-2020.

[0030] Example 1

[0031] 1) Dissolve 1 mol of methyl hexanoate 2,6-diisocyanate in anhydrous chlorobenzene to obtain a 1 mol / L solution. Under controlled temperature of 0℃ and stirring speed of 500 rpm, add 4.08 L of 0.5 mol / L n-decylamine solution (solvent is diethyl ether) dropwise. Keep the temperature at 0℃ for 2 h. After the reaction is completed, wash with 0.1 mol / L hydrochloric acid, separate the liquid and liquid phases, wash the organic phase with saturated sodium bicarbonate until the pH of the separated aqueous phase is 7, concentrate by vacuum distillation, and perform column chromatography. The eluent used in the column chromatography is a mixture of ethyl acetate and petroleum ether in a volume ratio of 5:1 to obtain a double-tailed hydrophobic compound.

[0032] 2) Under a nitrogen atmosphere, 80 mol of acrylamide, 20 mol of methacrylic acid sulfonic acid, and 3 mol of hydroxyethyl acrylate were added to water and mixed thoroughly to obtain a mixture. The total mass of the monomers in the mixture was 20 wt%. The pH of the mixture was adjusted to 7 with 1 mol / L sodium hydroxide solution, and the temperature was raised to 40℃. At the same time, 1 g / 100 mL of ammonium persulfate solution (solvent: water) and 1 g / 100 mL of sodium bisulfite solution (solvent: water) were added dropwise. The ammonium persulfate solution was added dropwise over 40 min, and the sodium bisulfite solution was added dropwise over 60 min. The mass ratio of ammonium persulfate to sodium bisulfite was 3:1. The total mass of the oxidant and the reducing agent was 0.003 wt% of the total mass of acrylamide, methacrylic acid sulfonic acid, and hydroxyethyl acrylate. The reaction was carried out at 60℃ for 10 h. After the reaction, the copolymer was sheared, granulated, dried, pulverized, washed with ethanol, and dried again to obtain the copolymer. The viscosity-average molecular weight of the copolymer was 22 million.

[0033] 3) Dissolve 15 kg of the double-tailed hydrophobic compound, 100 kg of the copolymer, and 0.3 kg of p-toluenesulfonic acid in 600 L of DMF, heat to reflux and react for 8 h. After the reaction is complete, pour into anhydrous ethanol for precipitation, filter, wash with anhydrous ethanol, and dry under vacuum at 60 °C to constant weight to obtain the double-tailed hydrophobic associating polymer; the viscosity-average molecular weight of the double-tailed hydrophobic associating polymer is 24.1 million.

[0034] 4) Add 0.5 kg of hydrophobic associative polymer to 99.35 kg of brine 1 and dissolve it, then add 0.15 kg of sodium lauryl ether-8 sulfate and dissolve it to obtain a binary composite oil displacement agent.

[0035] Salt solution 1: Prepare a standard salt solution with a total mineralization of 20000 mg / L using distilled water, NaCl, CaCl₂, and MgCl₂. 2+ 1400 mg / L, Mg 2+ The concentration was 600 mg / L, with the remainder being sodium. + C1 - .

[0036] Example 2

[0037] The rest is the same as in Example 1, except that in step 4), brine 2 is used instead of brine 1 by an equal mass. Brine 2 is a standard salt solution with a total mineralization of 10000 mg / L prepared by distilling water, NaCl, CaCl2, and MgCl2. 2+ 800 mg / L, Mg 2+ The concentration was 200 mg / L, with the remainder being Na. + C1 - .

[0038] Example 3

[0039] The rest is the same as in Example 1, except that in step 4), salt water 3 is used instead of salt water 1 of equal mass. Salt water 3 is a standard salt solution with a total mineralization of 30000 mg / L prepared by distilling water, NaCl, CaCl2, and MgCl2. 2+ 2000 mg / L, Mg 2+ It is 1000 mg / L, the rest is Na. + C1 - .

[0040] Example 4

[0041] The rest is the same as in Example 1, except that in step 2), the amount of hydroxyethyl acrylate is 1.5 mol; and in step 3), the amount of the double-tailed hydrophobic compound is 10 kg. The copolymer obtained in step 2) has a viscosity-average molecular weight of 21.56 million; the double-tailed hydrophobic associating polymer obtained in step 3) has a viscosity-average molecular weight of 22.96 million.

[0042] Example 5

[0043] The rest is the same as in Example 1, except that in step 2), the amount of hydroxyethyl acrylate is 0.5 mol; and in step 3), the amount of the double-tailed hydrophobic compound is 5 kg. The copolymer obtained in step 2) has a viscosity-average molecular weight of 21 million; the double-tailed hydrophobic associative polymer obtained in step 3) has a viscosity-average molecular weight of 21.69 million.

[0044] Example 6

[0045] The rest is the same as in Example 1, except that in step 1), n-butylamine is used instead of n-decylamine in an equimolar amount. The copolymer obtained in step 2) has a viscosity-average molecular weight of 22 million; the double-tailed hydrophobic associating polymer obtained in step 3) has a viscosity-average molecular weight of 24.03 million.

[0046] Example 7

[0047] The rest is the same as in Example 1, except that in step 1), 4-n-decylaniline is used instead of n-decylamine in an equimolar amount. The copolymer obtained in step 2) has a viscosity-average molecular weight of 22 million; the double-tailed hydrophobic associating polymer obtained in step 3) has a viscosity-average molecular weight of 24.14 million.

[0048] Example 8

[0049] The rest is the same as in Example 1, except that in step 4), sodium lauryl ether-5 sulfate is used instead of sodium lauryl ether-8 sulfate of equal mass.

[0050] Example 9

[0051] The rest is the same as in Example 1, except that in step 4), the amount of hydrophobic associative polymer is 0.3 kg, and the amount of brine 1 is made up to 100 kg.

[0052] Example 10

[0053] The rest is the same as in Example 1, except that in step 4), the amount of sodium lauryl ether-8 sulfate is 0.05 kg, and brine 1 is replenished to 100 kg.

[0054] Example 11

[0055] 1) Dissolve 1 mol of L-lysine diisocyanate in anhydrous chlorobenzene to obtain a 1 mol / L solution. Under controlled temperature of 0℃ and stirring speed of 800 rpm, add 4.16 L of 0.5 mol / L n-decylamine solution (solvent is diethyl ether) dropwise. Keep the temperature at 0℃ for 2 h. After the reaction is completed, wash with 0.1 mol / L hydrochloric acid, separate the liquid and liquid phases, wash the organic phase with saturated sodium bicarbonate until the pH of the separated aqueous phase is 7, concentrate by vacuum distillation, and perform column chromatography. The eluent used in the column chromatography is a mixture of ethyl acetate and petroleum ether in a volume ratio of 8:1 to obtain a double-tailed hydrophobic compound.

[0056] 2) Under a nitrogen atmosphere, 80 mol of acrylamide, 20 mol of 2-acrylamido-2-methylpropanesulfonic acid, and 3 mol of hydroxypropyl acrylate were added to water and mixed to obtain a mixture. The total mass of the monomers in the mixture was 20 wt%. The pH of the mixture was adjusted to 7 with 1 mol / L sodium hydroxide solution, and the temperature was raised to 40℃. At the same time, 1 g / 100 mL ammonium persulfate solution (solvent: water) and 1 g / 100 mL sodium bisulfite solution (solvent: water) were added dropwise. The ammonium persulfate solution was added dropwise over 40 min, and the sodium bisulfite solution was added dropwise over 60 min. The mass ratio of ammonium persulfate to sodium bisulfite was 3:1. The total mass of the oxidant and the reducing agent was 0.008 wt% of the total mass of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and hydroxyethyl acrylate. The reaction was carried out at 60℃ for 10 h. After the reaction, the copolymer was sheared, granulated, dried, pulverized, washed with ethanol, and dried again to obtain a copolymer with a viscosity-average molecular weight of 18.25 million.

[0057] 3) Dissolve 15 kg of the double-tailed hydrophobic compound, 100 kg of the copolymer, and 0.3 kg of p-toluenesulfonic acid in 600 L of DMF, heat to reflux and react for 8 h. After the reaction is complete, pour into anhydrous ethanol for precipitation, filter, wash with anhydrous ethanol, and dry under vacuum at 60 °C to constant weight to obtain the double-tailed hydrophobic associative polymer with a viscosity-average molecular weight of 20.31 million.

[0058] 4) Add 0.5 kg of hydrophobic associative polymer to 99.35 kg of brine 1 and dissolve it, then add 0.15 kg of sodium lauryl ether-8 sulfate and dissolve it to obtain a binary composite oil displacement agent.

[0059] Comparative Example 1

[0060] The rest is the same as in Example 1, except that in step 4), sodium lauryl ether-8 sulfate is replaced with an equal mass of tetradecyl alcohol polyoxyethylene (3) ether sulfate monoester sodium salt (CAS No. 25446-80-4).

[0061] Comparative Example 2

[0062] 1) Under a nitrogen atmosphere, 82.4 mol acrylamide and 20.6 mol methylpropenesulfonic acid were added to water and mixed to obtain a mixture. The total mass of the monomers in the mixture was 20 wt%. The pH of the mixture was adjusted to 7 with 1 mol / L sodium hydroxide solution, and the temperature was raised to 40℃. At the same time, 1 g / 100 mL ammonium persulfate solution (solvent is water) and 1 g / 100 mL sodium bisulfite solution (solvent is water) were added dropwise. The ammonium persulfate solution was added dropwise over 40 min, and the sodium bisulfite solution was added dropwise over 60 min. The mass ratio of ammonium persulfate to sodium bisulfite was 3:1. The total mass of the oxidant and the reducing agent was 0.003 wt% of the total mass of acrylamide and methylpropenesulfonic acid. The reaction was carried out at 60℃ for 10 h. After the reaction, the mixture was sheared, granulated, dried, crushed, washed with ethanol, and dried again to obtain the copolymer.

[0063] 2) Add 0.5 kg of copolymer to 99.35 kg of brine 1 and dissolve it, then add 0.15 kg of lauryl ether-8 sodium sulfate and dissolve it to obtain a binary composite oil displacement agent.

[0064] The binary composite oil displacement agents prepared in the above examples and comparative examples were subjected to the following performance tests:

[0065] 1. Interfacial tension test: At a temperature of 30℃, the TX-500C interfacial tension meter was used at a rotation speed of 5000 rpm to conduct the test according to the "SY / T5370-1999 Methods for Determination and Evaluation of Surface and Interfacial Tension".

[0066] 2. Water separation rate: S1 The oil displacement agent of the binary composite system in the example or comparative example is diluted with its brine to form a solution with a mass and proportion of 0.3wt% of the double-tailed hydrophobic associative polymer and sodium lauryl polyoxyethylene ether sulfate.

[0067] S2. The sample and simulated crude oil (simulated crude oil prepared by dehydrating crude oil and neutral kerosene, with a viscosity of about 10 mPa·s at 45℃) were added into a stoppered tube at a volume ratio of 1:1. The volume of the aqueous phase was recorded as V1.

[0068] S3 vibrates the plugged tube vigorously 300 times to emulsify the oil and water, and then places it in a 45°C constant temperature oven to maintain the temperature.

[0069] After S4 emulsification for 1 hour, the volume of the lower aqueous phase in the plugged tube was read and marked as V2.

[0070] Calculation method of S5 water separation rate

[0071] The water separation rate is calculated using the following formula: Water separation rate = V2 / V1 100% In the formula: V1 - Volume of the lower aqueous phase before emulsification, in milliliters (mL); V2 - Volume of the lower aqueous phase after emulsification, in milliliters (mL).

[0072] Table 1 Performance Test Results

[0073] As shown in Table 1, the binary composite system oil displacement agent of this invention possesses ultra-low interfacial tension, strong emulsification and oil-carrying capacity, and excellent calcium and magnesium ion tolerance, with an interfacial tension as low as 0.11-0.72 × 10⁻⁶. -2 The water separation rate is as low as 4.2-13.8%, with a density of mN / m. The performance test results of Examples 1-3, Comparative Examples 1 and 2 show that this invention, through the synergistic effect of a dual-tailed hydrophobic associative polymer and sodium lauryl polyoxyethylene ether sulfate, achieves a balance between ultra-low interfacial tension and good stability under medium salinity conditions (approximately 20,000 mg / L); at lower salinity conditions, its superior stability is a prominent advantage; and at high salinity conditions, although performance decreases somewhat, it is still significantly superior to conventional oil displacement systems (Comparative Examples 1 and 2). This fully demonstrates that this binary composite system oil displacement agent possesses ultra-low interfacial tension, strong emulsifying and oil-carrying capacity, and excellent calcium and magnesium ion tolerance, enabling it to adapt to reservoir conditions with varying salinity. The water separation rate test results of Examples 1, 8, 10 and Comparative Example 1 show that the double-tailed hydrophobic associating polymer and sodium lauryl polyoxyethylene ether sulfate have a significant synergistic effect in improving the emulsification performance of the oil displacement agent, indicating that the double-tailed hydrophobic associating polymer and sodium lauryl polyoxyethylene ether sulfate have good compatibility and the prepared oil displacement agent has strong emulsification and oil carrying capacity.

[0074] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.

Claims

1. A binary composite system oil displacement agent, characterized in that, The raw materials include the following percentages: 0.05-0.15 wt% sodium lauryl ether sulfate, 0.3-0.5 wt% bi-tailed hydrophobic associating polymer, and the remainder being brine. The bi-tailed hydrophobic associating polymer is prepared by the following method: reacting alkyl diisocyanate with organic amine to obtain a bi-tailed hydrophobic compound, and then grafting the bi-tailed hydrophobic compound onto a copolymer via transesterification. The copolymer's monomers include acrylamide, unsaturated sulfonic acid, and hydroxyacrylate in a molar ratio of 80-90:10-20:0.5-3; the mass ratio of the bi-tailed hydrophobic compound to the copolymer is 5-15:

100.

2. The binary composite system oil displacement agent according to claim 1, characterized in that, The molar ratio of the diisocyanate alkyl acid alkyl ester and the organic amine is 1:2.04-2.

08.

3. The binary composite system oil displacement agent according to claim 1, characterized in that, The diisocyanate-based alkyl acid alkyl ester is selected from one or a combination of two of L-lysine diisocyanate and methyl 2,6-diisocyanate hexanoate; the organic amine is selected from at least one of C4-C10 fatty amines and C4-C10 alkylaniline.

4. The binary composite system oil displacement agent according to claim 1, characterized in that, The molar ratio of acrylamide, unsaturated sulfonic acid, and hydroxyacrylate is 80-90:10-20:1.5-3; the viscosity-average molecular weight of the copolymer is 18 million to 22 million.

5. The binary composite system oil displacement agent according to claim 1, characterized in that, The hydroxy acrylate is selected from at least one of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, and hydroxybutyl acrylate; the unsaturated sulfonic acid is selected from at least one of 2-acrylamido-2-methylpropanesulfonic acid, allyl sulfonic acid, styrene sulfonic acid, and methacrylic sulfonic acid.

6. The binary composite system oil displacement agent according to claim 1, characterized in that, The mass ratio of the dual-tailed hydrophobic compound to the copolymer is 10-15:

100.

7. The binary composite system oil displacement agent according to claim 1, characterized in that, The dual-tailed hydrophobic associative polymer is prepared by a method comprising the following steps: 1) Dissolve the alkyl ester of diisocyanate in an anhydrous organic solvent, add an organic amine solution dropwise under temperature-controlled stirring, and keep the reaction at the temperature to obtain a double-tailed hydrophobic compound; 2) Under an inert atmosphere, acrylamide, unsaturated sulfonic acid, and hydroxy acrylate are added to water and mixed to obtain a monomer solution. The pH of the monomer solution is adjusted to 6.5-7.5, the initiator is added and the reaction is carried out under controlled temperature to obtain a copolymer. 3) Dissolve the copolymer, the double-tailed hydrophobic compound, and the catalyst in an organic solvent, and heat to reflux to react, to obtain the double-tailed hydrophobic associative polymer.

8. The binary composite system oil displacement agent according to claim 7, characterized in that, In step 3), the organic solvent is selected from at least one of DMF, DMSO, and NMP; the catalyst is selected from at least one of p-toluenesulfonic acid and sodium formate; the amount of catalyst used is 0.1-0.3 wt% of the copolymer; and the reflux reaction time is 5-8 h.

9. The binary composite system oil displacement agent according to claim 1, characterized in that, The sodium lauryl ether sulfate is selected from at least one of sodium lauryl ether-8 sulfate, sodium lauryl ether-7 sulfate, and sodium lauryl ether-5 sulfate; the total mineralization of the brine is 5000-30000 mg / L, and the total content of calcium and magnesium ions is 0-3000 mg / L.

10. A method for preparing the binary composite system oil displacement agent according to any one of claims 1-9, characterized in that, The process includes the following steps: adding a hydrophobic associative polymer to brine to dissolve it, and then adding sodium lauryl ether sulfate to dissolve it to obtain a binary composite oil displacement agent.

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