Cationic surfactant microemulsion and preparation method thereof

Abstract

The present invention provides a cationic surfactant microemulsion and a preparation method thereof. The raw materials of the microemulsion include a surfactant and water, wherein the surfactant is composed of a quaternary ammonium salt cationic surfactant, a fatty amine polyoxyethylene ether, an alkyl pyrrolidone, and an isomeric alcohol ether. The microemulsion is used to improve oil recovery after flooding, and has a low surfactant usage ratio, does not require the addition of salt or alcohol as a main agent, is low in cost, and is applicable to formation water with a salinity of up to 90,000 mg / L, thus facilitating widespread application.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas extraction, and in particular to a cationic surfactant microemulsion and a preparation method thereof. Background Art

[0002] Tertiary oil recovery technology is one of the most effective means to improve oil recovery. For low-permeability and ultra-low-permeability reservoirs, in recent years, the use of conventional active microemulsions can improve oil recovery by reducing oil-water interfacial tension and changing wettability. In 2000, Liu Zhongyun et al. in "The Effect of Wettability on Recovery and Relative Permeability" proved through water flooding experiments that the recovery rate of hydrophilic rocks is higher than that of oil-wet rocks, while weakly hydrophilic rocks have the highest recovery rate, followed by neutral wettability. Yao Fengying et al. believe that converting the wettability of oil-wet reservoirs to hydrophilic or neutral wettability is conducive to improving recovery. Yang Jian et al. in 2018 "Preparation and Application Research of High-efficiency Oil Displacement Surfactants" stated that the oil / water interfacial tension can be reduced to 1.9×10 －3 mN / m, with a final oil recovery efficiency of 52.5%. In 2019, Fan Huabo et al. published "Preparation and Performance Evaluation of Anionic Nonionic Surfactants for Improving Imbibition Efficiency," synthesizing the anionic nonionic surfactant AN211 from alkyl alcohol polyoxyethylene ether and maleic anhydride. The surfactant exhibited an interfacial tension of 3.37 mN / m, and its aqueous solution achieved an imbibition efficiency of 48% in rock cores. Currently, active emulsions used in tertiary oil recovery, whether blended with anionic and nonionic surfactants or with anionic, cationic, or zwitterionic surfactants, struggle to achieve both ultra-low interfacial tension, strong water wetting, and good crude oil emulsification due to the structural composition of ion pairs, the interaction of different active groups, and the complexity of practical oilfield applications.

[0003] In recent years, driven by the need to significantly increase oil recovery, medium-phase microemulsions have garnered significant attention in the oil industry. A medium-phase microemulsion is a three-phase equilibrium system consisting of a microemulsion, excess oil phase, and excess water phase. It possesses the unique property of solubilizing both oil and water, while also achieving ultra-low interfacial tension between the oil and water phases. This allows for excellent crude oil solubilization and emulsification, significantly improving oil displacement efficiency.

[0004] In 2016, Zhou Bingling et al. published "Study on the Optimal Middle Phase Microemulsion Displacement System", using the ternary phase diagram method to determine that the optimal middle phase microemulsion system is composed of 4% sodium dodecyl sulfate, 7% n-butanol and 3% sodium carbonate.

[0005] In 2021, Liang Yukai et al. published "Spontaneously generated middle-phase microemulsion oil washing system in low permeability reservoirs" and selected a middle-phase microemulsion system that can be rapidly and spontaneously generated, consisting of 1% to 8% compound surfactants, 1.5% to 3.5% C5 alcohol and 3.5% KCl aqueous solution.

[0006] In 2023, Wu Tianjiang et al. published "Screening of Mid-Phase Microemulsion Flooding Systems for Low-Permeability Reservoirs." The system consists of anionic surfactants, zwitterionic surfactants, sodium chloride, and n-butanol. The main agent is a mixture of sodium dodecylbenzene sulfonate and coconut fatty acid polyoxyethylene betaine in a 1:3 ratio, with a concentration of 0.3% to 0.7%. The main agent is a non-cationic surfactant. The system's auxiliary agents are 1.5% to 6% sodium chloride and 1.3% to 3.7% n-butanol, resulting in high costs.

[0007] In 1997, Hao Jingcheng et al. published "Formation and Properties of Cationic Surfactant-Based Microemulsions," describing a system composed of a quaternary ammonium salt cationic surfactant, sodium chloride, and n-butanol. The main agent was a proportional blend of two cationic surfactants, dioctadecyldimethylammonium chloride and decylpyridinium bromide. Dioctadecyldimethylammonium chloride is poorly soluble in water at room temperature, making it less practical. The auxiliary agents in the system were 1.3% to 2.2% sodium chloride and at least 1% n-butanol, resulting in high costs. This was primarily theoretical research, with no specific application areas.

[0008] Patent CN202110973258.X: A middle-phase microemulsion and its preparation process and application, comprising the following components: 0.1% to 0.35% of a main agent, 0.05% to 0.2% of sodium fatty alcohol polyoxyethylene polyoxypropylene sulfonate, 0.01% to 0.03% of an auxiliary agent, and water. The main agent includes at least one of sodium alkyl benzodicyclohexane sulfonate, sodium alkyl acenaphthene sulfonate, sodium alkyl biphenyl sulfonate, sodium alkyl fluorene sulfonate, and sodium alkyl indane sulfonate. A 0.5 PV middle-phase microemulsion solution is injected, followed by flooding with reinjection water to a water content of 98%. The calculated enhanced oil recovery of the middle-phase microemulsion after polymer flooding is 5.6% to 20.4%. However, this solution is suitable for formation water with a salinity of 10,000 mg / L to 30,000 mg / L. However, formation water salinity is typically high, making it difficult to achieve the requirement of less than 30,000 mg / L. Therefore, this solution has poor applicability. The nonionic surfactant uses an ester-based, easily hydrolyzed surfactant. The maximum usage concentration is 0.58%, which is high.

[0009] Currently, the formation of medium-phase microemulsions requires high concentrations of surfactants and co-surfactants, the addition of salt, and a high salinity of the formation water. Therefore, developing medium-phase microemulsions that are more suitable for low-permeability reservoirs, have high oil recovery efficiencies, and have promising industrial applications is a key development direction for this technology. Summary of the Invention

[0010] In view of this, the present invention proposes a cationic surfactant microemulsion and a preparation method thereof. The use of the microemulsion can solve the problems of high concentration of conventional middle-phase microemulsion surfactants, high requirements for injection water mineralization, and high on-site application costs.

[0011] The technical solution of the present invention is achieved as follows:

[0012] In one aspect, the present invention provides a cationic surfactant microemulsion, the raw materials of which include a surfactant and water, wherein the surfactant is composed of a quaternary ammonium salt cationic surfactant, a fatty amine polyoxyethylene ether, an alkyl pyrrolidone and an isomeric alcohol ether.

[0013] In some embodiments, the quaternary ammonium salt cationic surfactant includes a quaternary ammonium salt cationic surfactant having an alkyl group of C8 to C18.

[0014] In some embodiments, the quaternary ammonium salt cationic surfactant with an alkyl group of C8-C18 includes at least one of C8-C18 alkyltrimethylammonium chloride, C8-C18 alkyltrimethylammonium bromide, bis-C8-C18 alkyldimethylammonium chloride and bis-C8-C18 alkyldimethylammonium bromide.

[0015] In some embodiments, the fatty amine polyoxyethylene ether includes at least one of laurylamine polyoxyethylene ether with an EO addition number of 2 or 3 and octadecylamine polyoxyethylene ether with an EO addition number of 4 or 5.

[0016] In some embodiments, the alkyl pyrrolidone includes at least one of N-octyl pyrrolidone and N-dodecyl pyrrolidone.

[0017] In some embodiments, the isomeric alcohol ether includes at least one of isomeric decanol polyoxyethylene ether with an EO addition number of 5 to 9 and isomeric tridecanol polyoxyethylene ether with an EO addition number of 7, 8, 10, or 12.

[0018] In some embodiments, the salinity of the water is 10,000 mg / L to 90,000 mg / L.

[0019] In a second aspect, the present invention also provides a method for preparing the above-mentioned cationic surfactant microemulsion, comprising the following steps: adding a quaternary ammonium salt cationic surfactant, fatty amine polyoxyethylene ether, alkyl pyrrolidone and isomeric alcohol ether into water and mixing them uniformly to obtain a microemulsion.

[0020] In a third aspect, the present invention further provides a use of the above cationic surfactant microemulsion or the microemulsion prepared by the above method for preparing the cationic surfactant microemulsion in an oil displacement agent.

[0021] The present invention has the following beneficial effects compared to the prior art:

[0022] The cationic surfactant microemulsion of the present invention can be used for oil displacement and generate a middle phase with crude oil. The recovery rate after microemulsion displacement is increased by 13.6% compared with water displacement. The weight proportion of the surfactant in the microemulsion of the present invention is less than 0.28%, and no salt and alcohol additives need to be added, so the cost of use is low. At the same time, it is suitable for formation water with a salinity of up to 90,000 mg / L, has a wider range of applications, and is conducive to promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 This is a phase diagram of the microemulsion prepared in Example 2 of the present invention and Jiangsu crude oil;

[0025] Figure 2 This is a cryo-scanning electron micrograph of the intermediate phase produced by the microemulsion prepared in Example 2 of the present invention and Jiangsu crude oil, wherein the scale bar is 250 nm;

[0026] Figure 3 This is a small-angle X-ray scattering diagram of the middle phase produced by the microemulsion prepared in Example 2 of the present invention and Jiangsu crude oil;

[0027] Figure 4 This is a curve diagram of water content and recovery rate changes during the core flooding test of the microemulsion prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of the present invention belong. If the definitions set forth in this section are contrary to or otherwise inconsistent with definitions set forth in the patents, patent applications, published patent applications, and other publications incorporated herein by reference, the definitions listed in this section take precedence over the definitions incorporated herein by reference.

[0030] Unless otherwise specified, the methods used in the following examples are conventional methods. The materials, reagents, and instruments used are conventional materials, reagents, and instruments in the art, unless otherwise specified, and can be obtained commercially by those skilled in the art.

[0031] When an amount, concentration or other value or parameter is expressed as a range, a preferred range or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any upper range limit or preferred value with any lower range limit or preferred value, regardless of whether the range is disclosed alone. For example, when a range "1 to 5" is disclosed, the described range should be interpreted as including the ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within the range. In the present specification and claims, range definitions may be combined and / or interchanged, and if not otherwise stated, such ranges include all subranges contained therein.

[0032] The water used in the following examples is formation simulated water, and its salinity and ion composition are shown in the following table:

[0033]

[0034] Example 1

[0035] A cationic surfactant microemulsion, calculated by weight percentage, comprises the following components:

[0036] 0.039% octadecyltrimethylammonium bromide

[0037] 0.156% Octadecylamine polyoxyethylene ether (EO addition number 5) AC1805

[0038] 0.039% N-octylpyrrolidone

[0039] 0.015% Isomeric Deca-alcohol Polyoxyethylene Ether (EO addition number 6) E1006

[0040] The surfactant accounts for 0.249% of the total weight of the microemulsion, and the remainder is water with a salinity of 10000 mg / L, which accounts for 99.751% of the total weight of the microemulsion.

[0041] The microemulsion preparation method comprises: adding octadecyltrimethylammonium bromide, octadecylamine polyoxyethylene ether, N-octyl pyrrolidone and isomeric decanol polyoxyethylene ether into water and mixing them evenly to obtain the microemulsion.

[0042] Example 2

[0043] A cationic surfactant microemulsion, calculated by weight percentage, comprises the following components:

[0044] 0.037% hexadecyltrimethylammonium bromide

[0045] 0.156% Octadecylamine polyoxyethylene ether (EO addition number 5) AC1805

[0046] 0.039% N-octylpyrrolidone

[0047] 0.013% Isomeric Deca-alcohol Polyoxyethylene Ether (EO addition number 6) E1006

[0048] The surfactant accounts for 0.245% of the total weight of the microemulsion, and the remainder is water with a salinity of 30,000 mg / L, which accounts for 99.755% of the total weight of the microemulsion.

[0049] The microemulsion preparation method comprises: adding cetyltrimethylammonium bromide, octadecylamine polyoxyethylene ether, N-octyl pyrrolidone and isomeric decanol polyoxyethylene ether into water and mixing them evenly to obtain the microemulsion.

[0050] Example 3

[0051] A cationic surfactant microemulsion, calculated by weight percentage, comprises the following components:

[0052] 0.031% bis(octyldimethylammonium chloride)

[0053] 0.087% dodecylamine polyoxyethylene ether (EO addition number 2) AC1202

[0054] 0.051% N-dodecylpyrrolidone

[0055] 0.018% Isotridecyl Polyoxyethylene Ether (EO addition number 8) E1308

[0056] The surfactant accounts for 0.187% of the total weight of the microemulsion, and the remainder is water with a salinity of 50,000 mg / L, which accounts for 99.813% of the total weight of the microemulsion.

[0057] The microemulsion preparation method comprises: adding bis-octyl dimethyl ammonium chloride, dodecylamine polyoxyethylene ether, N-dodecyl pyrrolidone and isomeric tridecanol polyoxyethylene ether into water and mixing them evenly to obtain the microemulsion.

[0058] Example 4

[0059] A cationic surfactant microemulsion, calculated by weight percentage, comprises the following components:

[0060] 0.042% didodecyldimethylammonium chloride

[0061] 0.087% dodecylamine polyoxyethylene ether (EO addition number 2) AC1202

[0062] 0.051% N-dodecylpyrrolidone

[0063] 0.012% Isotridecyl Polyoxyethylene Ether (EO addition number 12) E1312

[0064] The surfactant accounts for 0.192% of the total weight of the microemulsion, and the remainder is water with a salinity of 70,000 mg / L, which accounts for 99.808% of the total weight of the microemulsion.

[0065] The microemulsion preparation method comprises: adding didodecyl dimethyl ammonium chloride, dodecylamine polyoxyethylene ether, N-dodecyl pyrrolidone and isomeric tridecanol polyoxyethylene ether into water and mixing them evenly to obtain the microemulsion.

[0066] Example 5

[0067] A cationic surfactant microemulsion, calculated by weight percentage, comprises the following components:

[0068] 0.042% didodecyldimethylammonium chloride

[0069] 0.043% dodecylamine polyoxyethylene ether (EO addition number 2) AC1202

[0070] 0.061% N-dodecylpyrrolidone

[0071] 0.015% Isomeric Deca-alcohol Polyoxyethylene Ether (EO addition number 9) E1009

[0072] The surfactant accounts for 0.161% of the total weight of the microemulsion, and the remainder is water with a salinity of 90,000 mg / L, which accounts for 99.839% of the total weight of the microemulsion.

[0073] The microemulsion preparation method comprises the following steps: adding didodecyl dimethyl ammonium chloride, dodecylamine polyoxyethylene ether, N-dodecyl pyrrolidone and isomeric decanol polyoxyethylene ether into water and mixing them uniformly to obtain the microemulsion.

[0074] Example 6

[0075] A cationic surfactant microemulsion, calculated by weight percentage, comprises the following components:

[0076] 0.031% didodecyldimethylammonium chloride

[0077] 0.043% dodecylamine polyoxyethylene ether (EO addition number 2) AC1202

[0078] 0.039% N-dodecylpyrrolidone

[0079] 0.012% Isomeric Deca-alcohol Polyoxyethylene Ether (EO addition number 5) E1005

[0080] The surfactant accounts for 0.125% of the total weight of the microemulsion, and the remainder is water with a salinity of 90,000 mg / L, which accounts for 99.875% of the total weight of the microemulsion.

[0081] The microemulsion preparation method comprises the following steps: adding didodecyl dimethyl ammonium chloride, dodecylamine polyoxyethylene ether, N-dodecyl pyrrolidone and isomeric decanol polyoxyethylene ether into water and mixing them uniformly to obtain the microemulsion.

[0082] Example 7

[0083] A cationic surfactant microemulsion, calculated by weight percentage, comprises the following components:

[0084] 0.042% octadecyltrimethylammonium bromide

[0085] 0.156% Octadecylamine polyoxyethylene ether (EO addition number 5) AC1805

[0086] 0.061% N-octylpyrrolidone

[0087] 0.018% Isomeric Deca-alcohol Polyoxyethylene Ether (EO addition number 6) E1006

[0088] The surfactant accounts for 0.277% of the total weight of the microemulsion, and the remainder is water with a salinity of 10000 mg / L, which accounts for 99.723% of the total weight of the microemulsion.

[0089] The microemulsion preparation method comprises: adding octadecyltrimethylammonium bromide, octadecylamine polyoxyethylene ether, N-octyl pyrrolidone and isomeric decanol polyoxyethylene ether into water and mixing them evenly to obtain the microemulsion.

[0090] The interfacial tension and wetting properties of the cationic surface or microemulsions prepared in the above examples were tested.

[0091] The interfacial tension test is carried out in accordance with the method specified in the petroleum and natural gas industry standard "SY / T 5370 Surface and interfacial tension determination method".

[0092] The crude oil used in the experiment was Jiangsu crude oil. The interfacial tension between Jiangsu crude oil and the microemulsion prepared in the above example was about 10 -3 mN / m, reaching the ultra-low interface.

[0093] The wettability test was carried out in accordance with the method specified in the petroleum and natural gas industry standard "SY / T 5153 Determination of Wettability of Reservoir Rocks".

[0094] The crude oil used in the experiment was Jiangsu crude oil. The wetting reversal between Jiangsu crude oil and the microemulsion prepared in the above embodiment was achieved within 24 hours, with the contact angles being less than 9°, transforming the oil-wet surface into a strongly water-wet surface.

[0095] The above experimental results are shown in the following table:

[0096]

[0097] The microemulsion prepared in Example 2 was mixed with Jiangsu crude oil at a volume ratio of 1:1 and placed in a precision calibrated colorimetric tube. After gently shaking up and down 50 times, it was placed in a constant temperature oven at 75°C and allowed to stand for 3 days. The interface stratification was observed to form a distinct middle phase. Figure 1 shown.

[0098] Furthermore, the middle phase produced by the microemulsion prepared in Example 2 and Jiangsu crude oil was characterized by cryo-scanning electron microscopy. The cryo-scanning electron microscopy observed a sponge-like oil-water bicontinuous structure, i.e., the formation of the middle phase. The observation photos are as follows: Figure 2 shown.

[0099] Furthermore, the middle phase produced by the microemulsion prepared in Example 2 and Jiangsu crude oil was characterized by small-angle X-ray scattering. The small-angle X-ray scattering experimental data was fitted with the Teubner-Strey simulation, proving that the system was a well-defined oil-water bicontinuous phase, i.e., a middle phase was formed. The experimental measurement data are as follows: Figure 3 shown.

[0100] Furthermore, referring to the method specified in the petroleum and natural gas industry standard "SY / T 5862 Technical Requirements for Polymers for Oil Displacement," simulated formation water was injected at a flow rate of 0.1 mL / min until the water cut at the production end exceeded 98%. After injecting 1 PV of the microemulsion prepared in Example 2 at a flow rate of 0.1 mL / min, subsequent water flooding was carried out until the water cut exceeded 98%, and the oil displacement efficiency was calculated.

[0101] A natural core of a block with a length of 8 cm and a diameter of 2.5 cm was used. The core had a porosity of 15.7%, a permeability of 38.8 mD, and a temperature of 55°C. The test was carried out according to the core flooding method. The salinity was 30,000 mg / L simulated formation water. The water content and recovery rate change curves of the microemulsion prepared in Example 2 during the flooding stage were as follows: Figure 4 As shown in Figure 2, the recovery rate of low-permeability core oil flooding is 38.2%. After adding the microemulsion flooding agent, the recovery rate reaches 51.8%, a 13.6% increase compared to water flooding. Furthermore, when the water flooding exceeds 98%, the microemulsion flooding system can reduce the water content by 5.6%, demonstrating a significant oil recovery effect.

[0102] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A cationic surfactant microemulsion, characterized in that: The raw materials of the microemulsion include, by weight percentage, 0.031% to 0.042% of a quaternary ammonium salt cationic surfactant, 0.043% to 0.156% of a fatty amine polyoxyethylene ether, 0.039% to 0.061% of an alkyl pyrrolidone, 0.012% to 0.018% of an isomeric alcohol ether, and 99.723% to 99.875% of water, wherein the alkyl pyrrolidone includes at least one of N-octyl pyrrolidone and N-dodecyl pyrrolidone.

2. The cationic surfactant microemulsion according to claim 1, wherein The quaternary ammonium salt cationic surfactant includes a quaternary ammonium salt cationic surfactant whose alkyl group is C8~C18.

3. The cationic surfactant microemulsion according to claim 2, wherein The quaternary ammonium salt cationic surfactant with an alkyl group of C8~C18 includes at least one of C8~C18 alkyl trimethyl ammonium chloride, C8~C18 alkyl trimethyl ammonium bromide, di-C8~C18 alkyl dimethyl ammonium chloride and di-C8~C18 alkyl dimethyl ammonium bromide.

4. The cationic surfactant microemulsion according to claim 1, wherein The fatty amine polyoxyethylene ether includes at least one of laurylamine polyoxyethylene ether with an EO addition number of 2 or 3 and octadecylamine polyoxyethylene ether with an EO addition number of 4 or 5.

5. The cationic surfactant microemulsion according to claim 1, wherein The isomeric alcohol ether includes at least one of isomeric decanol polyoxyethylene ether with an EO addition number of 5 to 9 and isomeric tridecanol polyoxyethylene ether with an EO addition number of 7, 8, 10, and 12.

6. The cationic surfactant microemulsion according to claim 1, wherein The mineralization of the water is 10000 mg / L to 90000 mg / L.

7. A method for preparing a cationic surfactant microemulsion according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: adding quaternary ammonium salt cationic surfactant, fatty amine polyoxyethylene ether, alkyl pyrrolidone and isomeric alcohol ether into water, and mixing them evenly to obtain microemulsion.

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