A tertiary oil recovery method using a composite oil displacement agent and the oil displacement agent thereof

Abstract

The present application discloses a tertiary oil recovery method and its oil-displacing agent using a composite oil-displacing agent, belonging to the field of tertiary oil recovery technology. The composite oil-displacing agent includes the following percentages of components: 0.5-1.5% of a tetrapolymer, 0.1-0.3% of a heavy oil penetrant, 0.3-1% of a surfactant, and the remainder of water; the surfactant includes a lipopeptide biosurfactant and sodium fatty alcohol polyoxyethylene ether carboxylate; the tetrapolymer is obtained by copolymerization of acrylamide, acryloylmorpholine, 2-acrylamide-2-methylpropanesulfonic acid, and hexadecyldimethylallyl ammonium chloride; the heavy oil penetrant is octadecyl methacrylate or octadecyl acrylate. By compounding a specific tetrapolymer, a surfactant, and a heavy oil penetrant in a specific ratio, a composite oil-displacing agent is obtained, which can improve oil displacement efficiency, and the oil-displacing agent has the effects of salt and high temperature resistance, and can meet the requirements of efficient viscosity increase under high temperature and high mineralization conditions.

Description

Technical Field

[0001] The present application relates to a tertiary oil recovery method using a composite oil displacement agent and the oil displacement agent thereof, belonging to the technical field of tertiary oil recovery. 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] Polymers can effectively increase water viscosity, thereby improving the oil-water mobility ratio, increasing the sweep coefficient of the flooding system, and ultimately enhancing crude oil recovery. Therefore, polymer flooding technology has become a primary means of tertiary oil recovery. Conventional polymers used in oil fields are mostly partially hydrolyzed polyacrylamide, which has the following main problems: Its high molecular weight and long carbon chain make it susceptible to shear degradation; at high salinity, the partially hydrolyzed polyacrylamide molecular chain curls, resulting in low viscosity of the polymer solution; and at high temperatures, it is susceptible to hydrolysis due to temperature effects.

[0005] Existing partially hydrolyzed polyacrylamide (PAA) as a polymer flooding agent is no longer able to meet the requirements for efficient viscosity enhancement under high-temperature and high-salinity conditions. With the continued development of deep-well, high-temperature, and high-salinity reservoirs, the development of a high-efficiency, high-temperature and salt-resistant oil-displacement agent system is of great practical significance. Summary of the Invention

[0006] In order to solve the above problems, a tertiary oil recovery method using a composite oil-displacing agent and its oil-displacing agent are provided. By compounding a specific tetrapolymer, a surfactant and a heavy oil penetrant in a specific proportion, a composite oil-displacing agent is obtained, which can improve the oil recovery efficiency. The oil-displacing agent is salt-resistant and high-temperature-resistant, and can meet the requirements of efficient viscosity increase under high-temperature and high-mineralization conditions.

[0007] According to one aspect of the present application, a composite oil displacement agent is provided, comprising the following components in the following percentages: 0.5-1.5% of a tetrapolymer, 0.1-0.3% of a heavy oil penetrant, 0.3-1% of a surfactant, and the balance of water;

[0008] The surfactant includes lipopeptide biosurfactant and sodium fatty alcohol polyoxyethylene ether carboxylate;

[0009] The tetrapolymer is obtained by copolymerizing acrylamide, acryloylmorpholine, 2-acrylamide-2-methylpropanesulfonic acid and hexadecyldimethylallyl ammonium chloride;

[0010] The thick oil penetrant is octadecyl methacrylate or octadecyl acrylate.

[0011] Optionally, the mass ratio of the lipopeptide biosurfactant to sodium fatty alcohol polyoxyethylene ether carboxylate is 1:1-1.5.

[0012] Optionally, the lipopeptide biosurfactant is a cyclic lipopeptide composed of a β-hydroxy fatty acid and 7 amino acids, the fatty acid portion is normal, isomeric and trans isomeric fatty acids with a carbon chain length of 7 to 10, and the connection sequence of the amino acid portion is Glu-Leu-Leu-Val-Asp-Leu-Leu.

[0013] Optionally, the method for preparing the tetrapolymer comprises the following steps:

[0014] (1) Dissolve acrylamide, acryloylmorpholine, 2-acrylamide-2-methylpropanesulfonic acid and hexadecyldimethylallyl ammonium chloride in water with a mass fraction of the polymerizable monomer of 30-35%, stir until completely dissolved, adjust the pH to 7, and pass nitrogen to remove oxygen;

[0015] (2) Add initiator dropwise, stir evenly, pass nitrogen to remove oxygen, and allow polymerization to occur to obtain a colloidal polymer;

[0016] (3) Cut the colloidal polymer into pieces, wash and soak it with anhydrous ethanol, and dry it to obtain a tetrapolymer.

[0017] Optionally, the mass ratio of acrylamide, acryloylmorpholine, 2-acrylamide-2-methylpropanesulfonic acid and hexadecyldimethylallylammonium chloride is (7-10):(8-10):(1-3):(1-2).

[0018] Optionally, the initiator is a mixture of potassium persulfate and sodium bisulfite; the mass ratio of potassium persulfate to sodium bisulfite is 1:1-2.

[0019] Optionally, the reaction temperature of the polymerization reaction in step (2) is 20-25° C., and the reaction time is 5-6 h.

[0020] According to another aspect of the present application, a tertiary oil recovery method using the composite oil displacement agent is provided, comprising the following steps:

[0021] (1) Select the layer section for tertiary oil recovery in the target well and divide the layer section into 3-5 groups of swallowing section and discharge section;

[0022] (2) Lower the packer and production tubing into the target well;

[0023] (3) Injecting the injection fluid containing the composite oil displacement agent into each swallowing section and then shutting down the well;

[0024] (4) After the well is soaked, the oil-water mixture displaced by the injection fluid is produced from each discharge section.

[0025] Optionally, in step (3), the volume ratio of the injection fluid to the fracturing fluid is 1:5-6; and the mass ratio of the composite oil displacement agent to the injection fluid is 0.5-2:100.

[0026] Optionally, the soaking time is 5-8 days.

[0027] The beneficial effects of this application include but are not limited to:

[0028] 1. A composite oil displacement agent according to the present application improves oil displacement efficiency by compounding a specific tetrapolymer, a surfactant, and a heavy oil penetrant in specific proportions. The oil displacement agent is also salt-resistant and high-temperature-resistant, meeting the requirements for efficient viscosity increase under high-temperature and high-salinity conditions.

[0029] 2. A composite oil-displacing agent according to the present application comprises a surfactant prepared by compounding a specific lipopeptide surfactant with sodium fatty alcohol polyoxyethylene ether carboxylate in a specific ratio. The lipopeptide surfactant effectively increases the degradation rate of oil, particularly aromatic hydrocarbons, non-hydrocarbons, and asphaltene components. The sodium fatty alcohol polyoxyethylene ether carboxylate effectively reduces interfacial tension and, possessing the properties of both anionic and nonionic surfactants, exhibits strong stability and emulsification ability in high salinity conditions. It also interacts with the quaternary polymer to enhance sweep and oil-washing efficiency.

[0030] 3. According to the present application, a composite oil-displacing agent is prepared by specifying the monomer types, monomer ratios, and initiators to produce a quaternary polymer. This quaternary polymer contains morpholine ring rigid groups, sulfonic acid groups, and associative groups. The absence of π-π conjugation in the acryloylmorpholine molecule enhances the activity of the monomer free radicals during polymerization, making it easier to copolymerize with other olefinic monomers. The morpholine rings also enhance the water solubility and viscosity-increasing properties of the copolymer through intermolecular hydrogen bonding. This polymer is adaptable to high-temperature, high-salinity reservoir conditions and, when combined with specific surfactants, improves oil displacement efficiency and increases production.

[0031] 4. The tertiary oil recovery method utilizing a composite oil-displacing agent according to this application simplifies the construction process, shortens the construction period, and eliminates the need for multiple well openings and closings, which in turn eliminates reservoir energy replenishment. Injecting the injection fluid containing the composite oil-displacing agent from the intake section significantly increases the oil-displacing agent's range of action, achieving increased production. Specific ratios of the injection fluid, fracturing fluid, and composite oil-displacing agent are also specified to achieve optimal oil recovery results. DETAILED DESCRIPTION

[0032] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0033] Unless otherwise defined, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. The reagents and raw materials used in the present invention can be purchased through conventional channels. Unless otherwise specified, the reagents and raw materials used in the present invention are used in accordance with conventional methods in the art or in accordance with the product instructions. In addition, any methods and materials similar to or equivalent to those described herein can be applied to the present invention. The preferred embodiments and materials described in this patent are for illustrative purposes only.

[0034] Example 1

[0035] (1) Select the layer section for tertiary oil recovery in the target well and divide the layer section into three groups of swallowing section and discharge section;

[0036] (2) Lower the packer and production tubing into the target well;

[0037] (3) Inject the injection fluid containing the composite oil displacement agent into each swallowing section, with the volume ratio of injection fluid to fracturing fluid being 1:5, and the mass ratio of the composite oil displacement agent to injection fluid being 0.5:100, and then keep the well in a well for 5 days;

[0038] (4) After the well is soaked, the oil-water mixture displaced by the injection fluid is produced from each discharge section.

[0039] A composite oil displacement agent comprising 0.5% of a tetrapolymer, 0.1% of a heavy oil penetrant octadecyl methacrylate, 0.3% of a surfactant, and the balance water; the surfactant comprising a lipopeptide biosurfactant and sodium fatty alcohol polyoxyethylene ether carboxylate, the mass ratio of the lipopeptide biosurfactant to the sodium fatty alcohol polyoxyethylene ether carboxylate being 1:1; the lipopeptide biosurfactant being a cyclic lipopeptide composed of a β-hydroxy fatty acid and seven amino acids, wherein the fatty acid portion comprises normal, isomeric, and trans-isomerized fatty acids with carbon chain lengths of 7 to 10, and the amino acid portion has a connection sequence of Glu-Leu-Leu-Val-Asp-Leu-Leu;

[0040] The preparation method of the tetrapolymer comprises the following steps:

[0041] (1) Dissolve acrylamide, acryloylmorpholine, 2-acrylamide-2-methylpropanesulfonic acid and hexadecyldimethylallyl ammonium chloride in water. The mass fraction of the polymerizable monomer is 30, and the mass ratio of acrylamide, acryloylmorpholine, 2-acrylamide-2-methylpropanesulfonic acid and hexadecyldimethylallyl ammonium chloride is 7:8:1:1. Stir until completely dissolved, adjust the pH to 7, and pass nitrogen to remove oxygen.

[0042] (2) Add a mixture of potassium persulfate and sodium bisulfite as initiators dropwise, with a mass ratio of potassium persulfate to sodium bisulfite of 1:1, stir evenly, pass nitrogen through to remove oxygen, and allow polymerization to occur at a reaction temperature of 20°C for 5 hours to obtain a colloidal polymer;

[0043] (3) Cut the colloidal polymer into pieces, wash, soak and dry it with anhydrous ethanol to obtain a quaternary polymer.

[0044] Example 2

[0045] (1) Select the layer section for tertiary oil recovery in the target well and divide the layer section into five groups of swallowing section and discharge section;

[0046] (2) Lower the packer and production tubing into the target well;

[0047] (3) Inject the injection fluid containing the composite oil displacement agent into each swallowing section, with the volume ratio of the injection fluid to the fracturing fluid being 1:6, and the mass ratio of the composite oil displacement agent to the injection fluid being 0.5:100, and then keep the well in a well for 8 days;

[0048] (4) After the well is soaked, the oil-water mixture displaced by the injection fluid is produced from each discharge section.

[0049] A composite oil displacement agent comprising 1.5% of a tetrapolymer, 0.3% of a heavy oil penetrant octadecyl methacrylate, 1% of a surfactant, and the balance water; the surfactant comprising a lipopeptide biosurfactant and sodium fatty alcohol polyoxyethylene ether carboxylate, the mass ratio of the lipopeptide biosurfactant to the sodium fatty alcohol polyoxyethylene ether carboxylate being 1:1.5; the lipopeptide biosurfactant being a cyclic lipopeptide composed of a β-hydroxy fatty acid and seven amino acids, wherein the fatty acid portion comprises normal, isomeric, and trans-isomerized fatty acids with carbon chain lengths of 7 to 10, and the amino acid portion has a connection sequence of Glu-Leu-Leu-Val-Asp-Leu-Leu;

[0050] The preparation method of the tetrapolymer comprises the following steps:

[0051] (1) Dissolve acrylamide, acryloylmorpholine, 2-acrylamide-2-methylpropanesulfonic acid and hexadecyldimethylallyl ammonium chloride in water. The mass fraction of the polymerizable monomer is 35%, and the mass ratio of acrylamide, acryloylmorpholine, 2-acrylamide-2-methylpropanesulfonic acid and hexadecyldimethylallyl ammonium chloride is 10:10:3:2. Stir until completely dissolved, adjust the pH to 7, and pass nitrogen to remove oxygen.

[0052] (2) Add a mixture of potassium persulfate and sodium bisulfite as initiators dropwise, with a mass ratio of potassium persulfate to sodium bisulfite of 1:2, stir evenly, pass nitrogen through to remove oxygen, and allow polymerization to occur at a reaction temperature of 25°C for 6 hours to obtain a colloidal polymer;

[0053] (3) Cut the colloidal polymer into pieces, wash, soak and dry it with anhydrous ethanol to obtain a quaternary polymer.

[0054] Example 3

[0055] (1) Select the layer section for tertiary oil recovery in the target well and divide the layer section into four groups of swallowing section and discharge section;

[0056] (2) Lower the packer and production tubing into the target well;

[0057] (3) Inject the injection fluid containing the composite oil displacement agent into each swallowing section, with the volume ratio of the injection fluid to the fracturing fluid being 1:5.5 and the mass ratio of the composite oil displacement agent to the injection fluid being 1:100, and then keep the well in a well for 6 days;

[0058] (4) After the well is soaked, the oil-water mixture displaced by the injection fluid is produced from each discharge section.

[0059] A composite oil displacement agent comprises 1% of a tetrapolymer, 0.2% of a heavy oil penetrant octadecyl acrylate, 0.6% of a surfactant, and the balance water; the surfactant comprises a lipopeptide biosurfactant and sodium fatty alcohol polyoxyethylene ether carboxylate, with the mass ratio of the lipopeptide biosurfactant to sodium fatty alcohol polyoxyethylene ether carboxylate being 1:1.2; the lipopeptide biosurfactant is a cyclic lipopeptide composed of a β-hydroxy fatty acid and seven amino acids, wherein the fatty acid portion comprises normal, isomeric, and trans-isomerized fatty acids with carbon chain lengths of 7 to 10, and the amino acid portion has a connection sequence of Glu-Leu-Leu-Val-Asp-Leu-Leu;

[0060] The preparation method of the tetrapolymer comprises the following steps:

[0061] (1) Dissolve acrylamide, acryloylmorpholine, 2-acrylamide-2-methylpropanesulfonic acid and hexadecyldimethylallyl ammonium chloride in water. The mass fraction of the polymerizable monomer is 30%, and the mass ratio of acrylamide, acryloylmorpholine, 2-acrylamide-2-methylpropanesulfonic acid and hexadecyldimethylallyl ammonium chloride is 7:8:3:2. Stir until completely dissolved, adjust the pH to 7, and pass nitrogen to remove oxygen.

[0062] (2) Add a mixture of potassium persulfate and sodium bisulfite as initiators dropwise, with a mass ratio of potassium persulfate to sodium bisulfite of 1:1.5, stir evenly, pass nitrogen through to remove oxygen, and allow polymerization to occur at a reaction temperature of 22°C for 5.5 hours to obtain a colloidal polymer;

[0063] (3) Cut the colloidal polymer into pieces, wash, soak and dry it with anhydrous ethanol to obtain a quaternary polymer.

[0064] Example 4

[0065] The difference between Example 4 and Example 3 is that the mass ratio of the composite oil-displacing agent to the injection liquid is 3:100, and the rest are the same.

[0066] Example 5

[0067] The difference between Example 5 and Example 3 is that the volume ratio of injection fluid to fracturing fluid is 1:10, and the rest are the same.

[0068] Comparative Example 1

[0069] The difference between Comparative Example 1 and Example 3 is that the composite oil-displacing agent in Comparative Example 1 does not include a quaternary polymer, and the rest are the same.

[0070] Comparative Example 2

[0071] The difference between Comparative Example 2 and Example 3 is that the surfactant in Comparative Example 2 does not include lipopeptide biosurfactant, and the rest are the same.

[0072] Comparative Example 3

[0073] The difference between Comparative Example 3 and Example 3 is that the mass ratio of the lipopeptide biosurfactant to the sodium alcohol polyoxyethylene ether carboxylate in Comparative Example 3 is 1:2, and the rest are the same.

[0074] Comparative Example 4

[0075] The difference between Comparative Example 4 and Example 3 is that the surfactant in Comparative Example 4 does not include sodium alcohol polyoxyethylene ether carboxylate, and the rest are the same.

[0076] Comparative Example 5

[0077] The difference between Comparative Example 5 and Example 3 is that the composite oil displacement agent in Comparative Example 5 does not include a heavy oil penetrant, and the rest are the same.

[0078] Comparative Example 6

[0079] The difference between Comparative Example 6 and Example 3 is that the mass ratio of acrylamide, acryloylmorpholine, 2-acrylamide-2-methylpropanesulfonic acid and hexadecyldimethylallyl ammonium chloride in Comparative Example 6 is 6:11:2:1, and the rest are the same.

[0080] Comparative Example 7

[0081] The difference between Comparative Example 7 and Example 3 is that the mass fraction of the polymerized monomer in Comparative Example 7 is 40%, and the rest are the same.

[0082] Comparative Example 8

[0083] The difference between Comparative Example 8 and Example 3 is that the mass ratio of potassium persulfate to sodium bisulfite in Comparative Example 8 is 1:3, and the rest are the same.

[0084] Experimental Example 1

[0085] The composite oil displacement agents obtained in Examples 1 to 5 and Comparative Examples 1 to 8 were subjected to performance tests according to SY / T 6424-2014 “Compound Oil Displacement System Performance Test Method”. The test results are shown in Table 1.

[0086] Table 1 Performance test results

[0087]

[0088] According to Table 1, the interfacial tension and oil removal efficiency of the composite oil-displacing agents obtained in Examples 1 to 3 are both high, among which Example 3 is the best example. Example 4 changes the mass ratio of the composite oil-displacing agent to the injection fluid, and Example 5 changes the volume ratio of the injection fluid to the fracturing fluid. The oil displacement efficiency decreases to varying degrees compared with Example 3; in Comparative Examples 1 to 5, the components or ratios of the composite oil-displacing agents are changed, and their interfacial tension increases to varying degrees, while the oil displacement efficiency decreases to varying degrees, among which Comparative Example 1 decreases the most significantly; in Comparative Examples 6 to 8, in the process of preparing the quadripolymer, the mass ratio of each monomer, the mass fraction of the polymerized monomer, and the ratio of the initiator are changed, and the interfacial tension of the composite oil-displacing agent obtained increases, while the oil displacement efficiency decreases.

[0089] The foregoing is merely an embodiment of the present application, and the scope of protection of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc. made within the technical ideas and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A composite oil-displacing agent, characterized in that: The method comprises the following components in the following percentages: 0.5-1.5% of a tetrapolymer, 0.1-0.3% of a heavy oil penetrant, 0.3-1% of a surfactant and the balance of water; The surfactant comprises a lipopeptide biosurfactant and sodium fatty alcohol polyoxyethylene ether carboxylate; the mass ratio of the lipopeptide biosurfactant to sodium fatty alcohol polyoxyethylene ether carboxylate is 1:1-1.5; The tetrapolymer is obtained by copolymerizing acrylamide, acryloylmorpholine, 2-acrylamide-2-methylpropanesulfonic acid and hexadecyldimethylallyl ammonium chloride; the mass ratio of acrylamide, acryloylmorpholine, 2-acrylamide-2-methylpropanesulfonic acid and hexadecyldimethylallyl ammonium chloride is (7-10): (8-10): (1-3): (1-2); The thick oil penetrant is octadecyl methacrylate or octadecyl acrylate; The lipopeptide biosurfactant is a cyclic lipopeptide composed of a β-hydroxy fatty acid and 7 amino acids, wherein the fatty acid portion is a normal, isomeric and trans isomeric fatty acid with a carbon chain length of 7 to 10, and the connection sequence of the amino acid portion is Glu-Leu-Leu-Val-Asp-Leu-Leu; The preparation method of the tetrapolymer comprises the following steps: (1) dissolving acrylamide, acryloylmorpholine, 2-acrylamide-2-methylpropanesulfonic acid and hexadecyldimethylallyl ammonium chloride in water to a mass fraction of 30-35% of the polymerizable monomers, stirring until completely dissolved, adjusting the pH to 7, and passing nitrogen through the water to remove oxygen; (2) adding an initiator dropwise, stirring evenly, passing nitrogen to remove oxygen, and causing a polymerization reaction to produce a colloidal polymer; (3) Cut the colloidal polymer into pieces, wash and soak it with anhydrous ethanol, and dry it to obtain a tetrapolymer.

2. A composite oil-displacing agent according to claim 1, characterized in that: The initiator is a mixture of potassium persulfate and sodium bisulfite; the mass ratio of the potassium persulfate to the sodium bisulfite is 1:1-2.

3. A composite oil-displacing agent according to claim 1, characterized in that: The reaction temperature of the polymerization reaction in step (2) is 20-25° C., and the reaction time is 5-6 h.

4. A tertiary oil recovery method using the composite oil displacement agent according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Select the layer section for tertiary oil recovery in the target well and divide the layer section into 3-5 groups of swallowing section and discharge section; (2) Lowering the packer and production tubing into the target well; (3) injecting the injection fluid containing the composite oil displacement agent into each swallowing section and then soaking the well; (4) After the well is soaked, the oil-water mixture displaced by the injection fluid is extracted from each discharge section.

5. The tertiary oil recovery method using a composite oil displacement agent according to claim 4, characterized in that: In step (3), the volume ratio of the injection fluid to the fracturing fluid is 1:5-6; the mass ratio of the composite oil displacement agent to the injection fluid is 0.5-2:

100.

6. The tertiary oil recovery method using a composite oil displacement agent according to claim 4, characterized in that: The stewing time is 5-8 days.

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