A viscosity-reducing oil displacement composition and its preparation method and application

Abstract

The present disclosure relates to a viscosity reduction oil displacement composition and its preparation method and application. The viscosity reduction oil displacement composition comprises a viscosity reducer, a zwitterionic surfactant and water; the viscosity reducer comprises a ternary copolymer, and the ternary copolymer comprises a structural unit (I), a structural unit (II) and a structural unit (III) as shown in the following formula. The viscosity reduction oil displacement composition has multiple functions of reducing interfacial tension, improving the fluidity of heavy oil, stabilizing emulsified oil droplets and improving the water-oil mobility ratio, and can effectively improve the recovery rate of heavy oil on the basis of water flooding.

Description

Technical Field

[0001] The present disclosure relates to the technical field of crude oil recovery, and in particular to a viscosity-reducing oil displacement composition and a preparation method and application thereof. Background Art

[0002] Heavy oil has high viscosity and low mobility, which makes it difficult to produce. Thermal recovery technology, which uses external heat sources to heat heavy oil to reduce its viscosity and improve its fluidity, is still the main method of heavy oil production. As the water content in the formation increases and the water flow channel breaks through the front of the heavy oil, the external heat source is mainly lost in the formation water, resulting in low heat utilization, which greatly increases the cost of heavy oil production. Compared with thermal recovery of heavy oil, heavy oil water flooding cold recovery technology (water flooding technology without external heat source) undoubtedly has the advantages of low cost and simple operation. The difficulty of heavy oil water flooding cold recovery technology is that the viscosity of heavy oil is higher than the viscosity of injected water, and the difference in water-oil mobility ratio is large, resulting in irregular oil-water front, viscous fingering and water channeling, which makes the recovery rate of heavy oil cold recovery low. At the same time, affected by the heterogeneity of the reservoir, the viscosity of crude oil is high, the permeability difference is large, the water injection utilization rate is low, and a large amount of residual heavy oil is difficult to reach, so the injection recovery rate during water flooding cold production is generally less than 20%. At present, water flooding cold production mainly reduces the viscosity of heavy oil and improves its fluidity by adding viscosity reducers to form O / W emulsions. For example, patent CN106520102A provides a composition for reducing the viscosity of heavy oil, which can reduce the viscosity of ordinary heavy oil by more than 90%. However, although viscosity reducers can reduce the viscosity of heavy oil, it is easy to cause water penetration of viscous finger, resulting in ineffective water flooding.

[0003] The research and development of a viscosity reduction and flooding system for cold recovery of heavy oil with both viscosity reduction and mobility control is the main development direction for improving the efficiency of water flooding of heavy oil. Patent CN109135709A discloses a viscosity reduction and flooding system that can be used for cold recovery of heavy oil, which is compounded with a nonionic surfactant, a cationic oligomeric surfactant, a composition of organic small molecule alcohols of C1 to C6 and polyacrylamide. Patent CN107365574A discloses a viscosity reduction and flooding system for ordinary heavy oil reservoirs, which is mainly compounded with alkyl alcohol polyoxyethylene ether sulfate, nonionic surfactant, organic solvent and polyacrylamide. The system increases the recovery rate by 28% in core displacement experiments when the concentration is 0.3%-0.5%. In addition, patent CN107365575A discloses an oil displacement system compounded with an emulsifier, an ester compound, a wetting agent and polyacrylamide in a certain proportion. CN107365574A discloses a viscosity-reducing oil-displacing agent composed of alkyl alcohol polyoxyethylene ether sulfate, nonionic surfactant, anionic surfactant, organic solvent and water, which needs to be compounded with polymers such as polyacrylamide to form an oil displacement system when used. The viscosity-reducing oil displacement systems disclosed in the above patents are all composed of different surfactants and small molecule organic solvents and polymers, but in actual use, the amount of small molecule surfactants is large, and the deep displacement effect is not good. Subsequently, amphiphilic polymers have the advantages of hydrophilic and lipophilic properties, which can simultaneously reduce the viscosity of heavy oil and improve the oil-water mobility ratio, and become the direction of research. CN109135709A proposes a viscosity-reducing oil displacement system suitable for heavy oil reservoirs, which is mainly composed of alkylphenol / alkyl alcohol polyoxyethylene ether, cationic oligomeric surfactants, organic small molecule alcohols and polyacrylamide. The system has a certain effect when core displacement. However, the oil displacement system has a narrow scope of application, and the cationic surfactant loss in carbonate reservoirs is large, which affects the displacement effect. CN110483701A discloses a water-soluble hyperbranched heavy oil viscosity reduction and displacement system, which is mainly used in oil reservoirs with a reservoir temperature of about 65°C and low viscosity of heavy oil. In general, the existing amphiphilic polymer viscosity reduction and displacement agent technology with both viscosity reduction and fluidity improvement is still immature, and the synthesized active polymer molecules still have problems such as low molecular weight, low viscosity, poor water solubility, unsatisfactory interfacial activity and emulsification effect. Summary of the invention

[0004] The purpose of the present disclosure is to provide a viscosity-reducing oil-displacing composition and a preparation method and application thereof. The viscosity-reducing oil-displacing composition has multiple functions of reducing interfacial tension, improving the fluidity of heavy oil, stabilizing emulsified oil droplets and improving the water-oil mobility ratio, and can effectively improve the recovery rate of heavy oil on the basis of water flooding.

[0005] In order to achieve the above-mentioned object, the present disclosure provides a viscosity reduction oil displacement composition in a first aspect, comprising a viscosity reducer, a zwitterionic surfactant and water; the viscosity reducer comprises a terpolymer, and the terpolymer comprises a structural unit (I), a structural unit (II) and a structural unit (III) as shown in the following formula:

[0006]

[0007] Wherein, R1 is selected from C2 to C9 alkyl; R2 to R 10 Each is independently selected from hydrogen, deuterium, fluorine, chlorine, bromine, and a C2-C9 alkyl group; m is 0, 1, 2, 3 or 4; and n is 0, 1, 2, 3 or 4.

[0008] Optionally, based on the total weight of the composition, the content of the viscosity reducer is 0.01-3.00% by weight, the content of the zwitterionic surfactant is 0.05-5.00% by weight, and the rest is water; preferably, based on the total weight of the composition, the content of the viscosity reducer is 0.1-1.0% by weight, the content of the zwitterionic surfactant is 0.3-1.0% by weight, and the rest is water.

[0009] Optionally, the zwitterionic surfactant is selected from one or more of alkyl betaines and their derivatives; preferably, the zwitterionic surfactant is selected from one or more of dodecyl dimethyl betaine, tetradecyl dimethyl betaine, hexadecyl dimethyl betaine, octadecyl dimethyl betaine, dodecyl dihydroxyethyl betaine, dodecyl dihydroxyethyl betaine, tetradecyl sulfopropyl betaine, hexadecyl dimethyl sulfopropyl betaine, octadecyl sulfopropyl betaine, dodecyl hydroxypropyl phosphate betaine, tetradecyl hydroxypropyl phosphate betaine and hexadecyl hydroxypropyl phosphate betaine.

[0010] Optionally, in the viscosity reducer, the molar ratio of the structural unit (I), the structural unit (II) and the structural unit (III) is (9-30):(10-70):(10-70); preferably (10-20):(50-70):(20-40); preferably, the weight average molecular weight of the viscosity reducer is 2×10 5 ~5×10 5 , preferably 2.5×10 5 ~5×10 5 .

[0011] Optionally, the terpolymer comprises a structure shown in the following formula (1) and / or formula (2):

[0012]

[0013] Wherein, x, y, and z are all integers greater than or equal to 1, and x / (x+y+z) is 10% to 70%, preferably 50% to 70%; y / (x+y+z) is 9% to 30%, preferably 10% to 20%; z / (x+y+z) is 10% to 70%, preferably 20% to 40%;

[0014]

[0015] Among them, e, f, and g are all integers greater than or equal to 1, and g / (e+f+g) is 10% to 70%, preferably 50% to 70%; f / (e+f+g) is 9% to 30%, preferably 10% to 20%; e / (e+f+g) is 10% to 70%, preferably 20% to 40%.

[0016] Optionally, R1 is selected from C2 to C6 alkyl, R2 to R 10 are all hydrogen, m is 0, 1 or 2; n is 0, 1 or 2.

[0017] Optionally, the viscosity reducer is prepared by a preparation method comprising the following steps: under polymerization reaction conditions, allowing a reaction monomer to contact and react with an initiator and a chain transfer agent in an organic solvent; the reaction monomer comprises: a first monomer having a structure shown in formula (IV), a second monomer having a structure shown in formula (V), and a third monomer having a structure shown in formula (VI):

[0018]

[0019] In formula (IV), M + for Na + or K + .

[0020] Optionally, the first monomer is selected from one or more of sodium p-styrene sulfonate, sodium m-styrene sulfonate, potassium p-styrene sulfonate and potassium m-styrene sulfonate; the second monomer is selected from one or more of acrylamide, deuterated acrylamide, 2-methyl acrylamide and crotonamide; the third monomer is selected from one or more of vinyl acetate, vinyl butyrate, vinyl nonanoate, allyl formate, allyl acetate, 3-butylene acetate, 2-propylene nonanoate and vinyl caproate; preferably, the molar ratio of the first monomer, the second monomer and the third monomer in the reaction monomer is 1:(1-5):(1-5); preferably 1:(1-3):(1-2).

[0021] Optionally, the polymerization reaction conditions include: under an inert atmosphere, the reaction temperature is 50-90°C, and the reaction time is 2-10 hours; preferably, the reaction temperature is 60-70°C, and the reaction time is 4-5 hours; optionally, the inert atmosphere contains one or more of nitrogen, helium and argon.

[0022] Optionally, the initiator is selected from at least one of an azo compound initiator and a peroxide initiator; optionally, the initiator is selected from at least one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, benzoyl peroxide and lauroyl peroxide; based on the total weight of the reaction monomers, the added weight concentration of the initiator is 0.5 wt% to 1.5 wt%, preferably 1.0 wt% to 1.5 wt%; optionally, the chain transfer agent is selected from at least one of aliphatic thiols, preferably dodecyl mercaptan; based on the total weight of the reaction monomers, the added concentration of the chain transfer agent is 0.1 wt% to 5.0 wt%, preferably 1.0 wt% to 3.0 wt%; optionally, the organic solvent is benzene or a benzene substituted product, preferably toluene.

[0023] The second aspect of the present disclosure provides a method for preparing the viscosity reduction oil displacement composition of the first aspect, comprising: mixing the viscosity reducer, a zwitterionic surfactant and water under stirring conditions.

[0024] A third aspect of the present disclosure provides a use of the viscosity reduction and oil displacement composition described in the first aspect of the present disclosure in cold recovery of heavy oil.

[0025] Through the above technical scheme, the present disclosure provides a viscosity reduction oil displacement composition and a preparation method and application thereof. The viscosity reduction oil displacement composition is formed by mixing a ternary copolymer and a zwitterionic surfactant, has hydrophilic and lipophilic properties, can reduce the oil-water interfacial tension, promote the emulsification and viscosity reduction of heavy oil, and improve the fluidity of heavy oil; the composition also has a certain viscosity, can improve the water-oil mobility ratio, increase the swept area of ​​the displacement fluid, and achieve the purpose of increasing the recovery rate of heavy oil and reducing the mining cost under multiple effects; at the same time, the composition inhibits the occurrence of chromatographic separation in the oil displacement system during the flow process, thereby ensuring that the oil displacement system has a larger effective radius and achieving the purpose of deep viscosity reduction oil displacement.

[0026] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0028] Figure 1 is the infrared spectrum of the product synthesized in Preparation Example 1. DETAILED DESCRIPTION

[0029] The specific implementation of the present disclosure is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the present disclosure, and is not used to limit the present disclosure.

[0030] The first aspect of the present disclosure provides a viscosity reduction oil displacement composition, comprising a viscosity reducer, a zwitterionic surfactant and water; the viscosity reducer comprises a terpolymer, and the terpolymer comprises a structural unit (I), a structural unit (II) and a structural unit (III) represented by the following formula:

[0031]

[0032] Wherein, R1 is selected from C2 to C9 alkyl; R2 to R 10 Each is independently selected from hydrogen, deuterium, fluorine, chlorine, bromine, and a C2-C9 alkyl group; m is 0, 1, 2, 3 or 4; and n is 0, 1, 2, 3 or 4.

[0033] The present invention provides a viscosity reduction oil displacement composition, which is formed by mixing a ternary copolymer and a zwitterionic surfactant. The composition has hydrophilic and lipophilic properties, can reduce oil-water interfacial tension, promote emulsification and viscosity reduction of heavy oil, and improve the fluidity of heavy oil; the composition also has a certain viscosity, improves the water-oil mobility ratio, increases the swept area of ​​the displacement fluid, and achieves the purpose of increasing the recovery rate of heavy oil and reducing the mining cost under multiple effects; at the same time, it inhibits the occurrence of chromatographic separation in the oil displacement system during the flow process, thereby ensuring that the oil displacement system has a larger effective radius, and achieving the purpose of deep viscosity reduction oil displacement.

[0034] The viscosity reduction oil displacement composition provided by the present disclosure includes a viscosity reducer containing a terpolymer, wherein the terpolymer not only has a relatively long carbon chain in the main chain, but also contains hydrophilic groups such as sulfonate, carboxylate and amine groups on the side chains. In a zwitterionic surfactant solution with a relatively low concentration, the terpolymer has a strong association with the zwitterionic surfactant, so that the macromolecular system of the viscosity reducer in the composition is stretched and the apparent viscosity of the solution is increased; at the same time, the cross-linking association between the molecules can increase the hydration radius of each molecule in the system. During the use of the composition, the macromolecular system can adjust the reservoir profile, improve the heterogeneity of the reservoir, and increase the swept area of ​​the displacement fluid.

[0035] In the present disclosure, a structural unit refers to a repeating unit in a polymer whose chemical composition and structure can be repeated. The terpolymer of the present disclosure can be one or more of a random copolymer, an alternating copolymer and a block copolymer, without specific limitation.

[0036] In one embodiment, the zwitterionic surfactant is selected from one or more of alkyl betaines and their derivatives;

[0037] Preferably, the zwitterionic surfactant is selected from one or more of dodecyl dimethyl betaine, tetradecyl dimethyl betaine, hexadecyl dimethyl betaine, octadecyl dimethyl betaine, dodecyl dihydroxyethyl betaine, dodecyl dihydroxyethyl betaine, tetradecyl sulfopropyl betaine, hexadecyl dimethyl sulfopropyl betaine, octadecyl sulfopropyl betaine, dodecyl hydroxypropyl phosphate betaine, tetradecyl hydroxypropyl phosphate betaine and hexadecyl hydroxypropyl phosphate betaine.

[0038] In one embodiment, based on the total weight of the composition, the content of the viscosity reducer is 0.01 to 3.00% by weight, the content of the zwitterionic surfactant is 0.05 to 5.00% by weight, and the rest is water.

[0039] In a preferred embodiment, based on the total weight of the composition, the content of the viscosity reducer is 0.1 to 1.0 weight%, the content of the zwitterionic surfactant is 0.3 to 1.0 weight%, and the rest is water.

[0040] In one embodiment, in the viscosity reducer, the molar ratio of the structural unit (I), the structural unit (II) and the structural unit (III) is (9-30):(10-70):(10-70); preferably (10-20):(50-70):(20-40). The present disclosure does not specifically limit this, and the molar ratio of the three structural units can be adjusted according to actual usage.

[0041] In one embodiment, the weight average molecular weight of the viscosity reducer is 2×10 5 ~5×10 5 , preferably 2.5×10 5 ~5×10 5 The present disclosure does not make any special limitation on this, and those skilled in the art can adjust the weight average molecular weight according to actual applications to achieve better effects of the viscosity reduction oil displacement composition.

[0042] In a specific embodiment, the terpolymer comprises a structure represented by the following formula (1) and / or formula (2):

[0043]

[0044] Wherein, x, y, and z are all integers greater than or equal to 1, and x / (x+y+z) is 10% to 70%, preferably 50% to 70%; y / (x+y+z) is 9% to 30%, preferably 10% to 20%; z / (x+y+z) is 10% to 70%, preferably 20% to 40%;

[0045]

[0046] Wherein, e, f, and g are all integers greater than or equal to 1, and g / (e+f+g) is 10% to 70%, preferably 50% to 70%; f / (e+f+g) is 9% to 30%, preferably 10% to 20%; e / (e+f+g) is 10% to 70%, preferably 20% to 40%. According to the present disclosure, the values ​​of x, y, and z or the values ​​of e, f, and g make the weight average molecular weight of the viscosity reducer between 2×10 5 ~5×10 5 within the range.

[0047] Formula (1) and Formula (2) are merely exemplary molecular structures of the terpolymer of the present disclosure, but the molecular structure of the terpolymer of the present disclosure is not limited to the above Formula (1) or Formula (2).

[0048] It can be seen from the above formula that the molecular structure of the terpolymer provided by the present invention includes structural unit (I), structural unit (II) and structural unit (III), and the polymer segment of structural unit (II) and the polymer segment of structural unit (III) are respectively connected on both sides of the polymer segment of structural unit (I), so that the viscosity reducer provided by the present invention has both hydrophilicity and lipophilicity.

[0049] In one embodiment, the interfacial modified viscosity reducing agent provided by the present disclosure is a solid, including powder or granules, preferably a powdered solid.

[0050] In a further embodiment, in the viscosity reducing agent, the substituents of the structural formulas of the structural unit (I), the structural unit (II) and the structural unit (III) may be:

[0051] R1 is selected from C2 to C6 alkyl, R2 to R 10 are all hydrogen, m is 0, 1 or 2; n is 0, 1 or 2.

[0052] In a specific embodiment, the viscosity reducer used in the present disclosure is a mixture, which also includes a viscosity reducing aid. The present disclosure combines the terpolymer with other viscosity reducing aids to use together as a viscosity reducer, which has a better effect than using the terpolymer alone and has a synergistic application effect.

[0053] In a further embodiment, the viscosity reducing agent comprises a binary copolymer and / or a homopolymer, wherein the binary copolymer contains two of the structural unit (I), the structural unit (II) and the structural unit (III), and the homopolymer contains the structural unit (I), the structural unit (II) or the structural unit (III). The present disclosure does not specifically limit this. In a specific embodiment, the weight ratio of the terpolymer to the viscosity reducing agent in the viscosity reducing agent is (80-90):(10-15). The present disclosure does not specifically limit this, and those skilled in the art can make adaptive adjustments so that the viscosity reducing agent has a better synergistic viscosity reducing effect.

[0054] In one embodiment, the viscosity reducer is prepared by a preparation method comprising the following steps:

[0055] Under polymerization conditions, the reaction monomers are contacted with an initiator and a chain transfer agent in an organic solvent for reaction; the reaction monomers include: a first monomer having a structure shown in formula (IV), a second monomer having a structure shown in formula (V), and a third monomer having a structure shown in formula (VI):

[0056]

[0057] In formula (IV), M + for Na + or K + .

[0058] In one embodiment, the first monomer is selected from one or more of sodium p-styrene sulfonate, sodium m-styrene sulfonate, potassium p-styrene sulfonate and potassium m-styrene sulfonate;

[0059] The second monomer is selected from one or more of acrylamide, deuterated acrylamide, 2-methylacrylamide and crotonamide;

[0060] The third monomer is selected from one or more of vinyl acetate, vinyl butyrate, vinyl nonanoate, propylene formate, propylene acetate, 3-butylene acetate, 2-propylene nonanoate and vinyl caproate.

[0061] In a preferred embodiment, the molar ratio of the first monomer, the second monomer and the third monomer in the reaction monomers is 1:(1-5):(1-5); preferably 1:(1-3):(1-2).

[0062] In a specific embodiment, the polymerization reaction conditions include: under an inert atmosphere, a reaction temperature of 50 to 90° C., and a reaction time of 2 to 10 h;

[0063] Preferably, the reaction temperature is 60-70°C and the reaction time is 4-5h;

[0064] Optionally, the inert atmosphere comprises one or more of nitrogen, helium and argon.

[0065] In one embodiment, the initiator is selected from at least one of an azo compound initiator and a peroxide initiator; optionally, the initiator is selected from at least one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, benzoyl peroxide and lauroyl peroxide; optionally, the added weight concentration of the initiator is 0.5 wt % to 1.5 wt %, preferably 1.0 wt % to 1.5 wt %, based on the total weight of the reaction monomers;

[0066] Optionally, the chain transfer agent is selected from at least one of aliphatic mercaptans, preferably dodecyl mercaptan; optionally, the chain transfer agent is added at a concentration of 0.1 wt % to 5.0 wt %, preferably 1.0 wt % to 3.0 wt %, based on the total weight of the reaction monomers;

[0067] Optionally, the organic solvent is benzene or a benzene substitute, preferably toluene.

[0068] According to the present disclosure, the viscosity reducer obtained by a simple preparation process is essentially a mixture, which can be put into use without a complicated purification process, is easy to operate and has a high yield.

[0069] The second aspect of the present disclosure provides a method for preparing the viscosity reduction oil displacement composition according to the first aspect of the present disclosure, comprising:

[0070] The viscosity reducer, zwitterionic surfactant and water are mixed under stirring.

[0071] In a specific implementation manner, the stirring speed ranges from 100 to 200 rpm.

[0072] The third aspect of the present disclosure provides use of the viscosity reduction and oil displacement composition described in the first aspect of the present disclosure in heavy oil production, especially heavy oil cold production.

[0073] The instruments, reagents, materials, etc. involved in the following embodiments of the present disclosure, unless otherwise specified, are conventional instruments, reagents, materials, etc. in the prior art and can be obtained through conventional commercial channels. The experimental methods, detection methods, etc. involved in the following embodiments, unless otherwise specified, are conventional experimental methods, detection methods, etc. in the prior art.

[0074] Preparation Example 1

[0075] This preparation example is used to prepare viscosity reducer A.

[0076] 0.01 mol sodium sulfonate styrene, 0.02 mol acrylamide, 0.01 mol vinyl acetate were added to the reactor in a molar ratio of 1:2:1, and 1.0 wt% initiator azobisisobutyronitrile and 1.0 wt% chain transfer agent dodecyl mercaptan were added. Nitrogen was introduced to replace the air in the flask, and the temperature was raised to 70°C. After reacting for 5 hours, the reaction was terminated. Part of the solvent was removed by rotary evaporation, and after washing with methanol several times, it was dried in an oven at 120°C for 4 hours to obtain a white solid. The obtained product was recorded as A (R1 is ethyl, R2 to R 10 is hydrogen, m and n are both 0).

[0077] The terpolymer in product A includes the following three structural units.

[0078]

[0079] The viscosity reducer A was tested by infrared spectroscopy (MPA type, Bruker, Germany). The infrared spectroscopy characterization results are as follows: Figure 1 As shown. In the infrared spectrum, 3440cm- 1 The stronger absorption peak at 2920cm- 1 The absorption peak near is the methylene absorption peak; at 1660cm- 1 The infrared absorption spectrum absorption peak at 1110cm- is the carbonyl stretching absorption peak connected to oxygen, indicating that the product contains an ester structure. 1 、552cm- 1 is the absorption peak of the unsaturated carbon on the benzene ring, indicating that there is a benzene ring on the side chain of the viscosity reducer A. The above test results prove that the viscosity reducer A prepared in the present disclosure contains structural unit (I), structural unit (II) and structural unit (III) at the same time, and a polymerization reaction occurs between the three monomers.

[0080] Preparation Comparative Example 1

[0081] The same preparation method as in Preparation Example 1 was adopted, except that sodium styrene sulfonate was not added, and the rest of the preparation process was the same as in Example 1 (the molar ratio of acrylamide to vinyl acetate was 2:1). The obtained product was recorded as D1.

[0082] Preparation Comparative Example 2

[0083] The same preparation method as in Preparation Example 1 was adopted, except that vinyl acetate was not added, and the rest of the preparation process was the same as in Example 1 (the molar ratio of sodium styrene sulfonate to acrylamide was 1:2). The obtained product was recorded as D2.

[0084] Preparation Comparative Example 3

[0085] The same preparation method as in Preparation Example 1 was adopted, except that acrylamide was not added, and the rest of the preparation process was the same as in Example 1 (the molar ratio of sodium sulfonate styrene to vinyl acetate was 1:1). The obtained product was recorded as D3.

[0086] Preparation Example 2

[0087] This preparation example is used to prepare viscosity reducer B.

[0088] The same preparation method as in Preparation Example 1 was used, except that vinyl acetate was replaced with propyl acetate. The obtained product was recorded as B (R1 is propyl, R2 to R 10 is hydrogen, m and n are both 0).

[0089] Preparation Example 3

[0090] This preparation example is used to prepare viscosity reducer C.

[0091] The same preparation method as in Preparation Example 1 was used, except that vinyl acetate was replaced with butyl acetate. The obtained product was recorded as C (R1 is butyl, R2 to R 10 is hydrogen, m and n are both 0).

[0092] Preparation Example 4

[0093] The same preparation method as Preparation Example 1 was adopted, except that 0.01 mol sodium sulfonate styrene, 0.05 mol acrylamide, and 0.04 mol vinyl acetate were added into the reactor in a molar ratio of 1:5:4, and the rest of the method was the same as Preparation Example 1. The obtained product was recorded as D.

[0094] The products obtained from the above preparation examples and comparative examples were subjected to the following tests, and the test results are listed in Table 1.

[0095] Gel permeation chromatography (GPC) was used to test the molecular weight.

[0096] The average molar ratio of the structural units in the viscosity reducer product is calculated according to the material addition ratio.

[0097] Table 1

[0098]

[0099] The following examples are used to prepare the viscosity reduction oil displacement composition provided by the present disclosure.

[0100] In the viscosity-reducing oil displacement compositions provided in the following examples and comparative examples, the water used is mineralized water with a mineralization degree of 7500 mg / L.

[0101] Example 1

[0102] At room temperature (15-35°C), a certain amount of viscosity reducer A and dodecyl dimethyl betaine (BS-12) were added to water, with the mass percentage of viscosity reducer A being 0.05% by weight and the mass percentage of BS-12 being 0.1% by weight based on the total weight of the composition. The mixture was stirred at a stirring speed of 100-200 rpm for 6 hours until it was completely mixed, thereby preparing a viscosity reduction displacement composition Z1.

[0103] Comparative Example 1 to Comparative Example 3

[0104] The same method as in Example 1 was used to obtain viscosity reducing oil displacement compositions DZ1 to DZ3, which were different from Example 1 only in that the viscosity reducing agent A was replaced by D1 to D3 prepared in Comparative Examples 1 to 3, respectively.

[0105] Example 2

[0106] At room temperature (15-35°C), a certain amount of viscosity reducer B and dodecyl dihydroxyethyl betaine were added to water, with the mass percentage of viscosity reducer B being 0.05% by weight and the mass percentage of dodecyl dihydroxyethyl betaine being 0.1% by weight based on the total weight of the composition. The mixture was stirred at a stirring speed of 100-200 rpm for 6 hours until it was completely mixed, thereby preparing a viscosity reduction displacement composition Z2.

[0107] Example 3

[0108] At room temperature (15-35°C), a certain amount of viscosity reducer C and tetradecyl sulfopropyl betaine were added to water, with the mass percentage of viscosity reducer C being 0.05% by weight and the mass percentage of tetradecyl sulfopropyl betaine being 0.1% by weight based on the total weight of the composition. The mixture was stirred at a stirring speed of 100-200 rpm for 8 hours until it was completely mixed, thereby preparing a viscosity reduction displacement composition Z3.

[0109] Comparative Example 4

[0110] The same method as in Example 3 was used to obtain a viscosity reducing oil displacement composition DZ4, which was different from Example 3 only in that the viscosity reducing agent C was replaced with commercially available polyacrylamide (provided by Henan Xinqi Polymer Co., Ltd., with a molecular weight of 8 million to 20 million).

[0111] Comparative Example 5

[0112] The viscosity reduction flooding composition DZ5 was obtained by the same method as in Example 3, which differed from Example 3 in that only a zwitterionic surfactant, tetradecyl sulfopropyl betaine, was added, and no viscosity reducer was added.

[0113] Example 4

[0114] The same method as in Example 1 was used to obtain a viscosity reducing oil displacement composition Z4, which was different from Example 1 only in that the viscosity reducing agent A was replaced by the viscosity reducing agent D.

[0115] Example 5

[0116] The viscosity reducing oil displacement composition Z5 was obtained by the same method as in Example 1, which was different from Example 1 only in that the mass percentage of viscosity reducing agent A was 0.1% by weight and the mass percentage of BS-12 was 0.5% by weight.

[0117] Example 6

[0118] The viscosity reducing oil displacement composition Z6 was obtained by the same method as in Example 1, which was different from Example 1 only in that the mass percentage of viscosity reducing agent A was 0.01% by weight and the mass percentage of BS-12 was 10% by weight.

[0119] Example 7

[0120] The viscosity reducing oil displacement composition Z7 was obtained by the same method as in Example 1, which was different from Example 1 only in that the zwitterionic surfactant BS-12 was replaced with dodecylaminopropionic acid.

[0121] In order to verify the performance of the viscosity reduction and oil displacement compositions obtained in the examples and comparative examples of the present disclosure, the following test examples 1 to 3 tested the viscosity increasing ability of the water phase, the heavy oil viscosity reduction performance, and the oil displacement performance of the obtained compositions.

[0122] Test Example 1

[0123] This test example is used to illustrate the evaluation process of the viscosity-reducing oil displacement composition provided by the present disclosure on the viscosity-increasing ability of the water phase.

[0124] The viscosity of the viscosity-reducing oil displacement composition obtained in the examples and comparative examples was tested using a HAKKE MARSⅢ rheometer at 50° C. The test results are listed in Table 2 below.

[0125] Table 2

[0126]

[0127] In the field of oil production, the water-oil mobility ratio refers to the ratio of the flow rate of the displacement fluid to the displaced phase (oil), which is inversely proportional to the viscosity of the fluid. According to the viscosity test data in Table 2 above:

[0128] (1) Compared with the viscosity of mineralized water, the viscosity-reducing oil displacement compositions Z1 to Z7 provided in the present disclosure can increase the viscosity of the aqueous solution and improve the water-oil mobility ratio;

[0129] (2) Z1 is compared with DZ1 to DZ3. Z1 uses the viscosity reducer A provided by the present disclosure, and the viscosity reducer A contains structural unit (I), structural unit (II) and structural unit (III). Z1 has higher viscosity and better effect of improving water-oil fluidity ratio;

[0130] (3) Comparing Z3 with DZ4-DZ5, Z3 uses the viscosity reducer C provided by the present disclosure, and Z3 has higher viscosity and better effect in improving the water-oil fluidity ratio;

[0131] (4) Comparing Z4 with Z1, the molar ratio of the first monomer, the second monomer and the third monomer in the reaction monomers of the viscosity reducer A used in Z1 satisfies 1:(1-3):(1-2), Z1 has a higher viscosity and a better effect of improving the water-oil fluidity ratio;

[0132] (5) Comparing Z5 with Z1, Z5 satisfies the conditions that "the content of viscosity reducer is 0.1-1.0 wt %, and the content of zwitterionic surfactant is 0.3-1.0 wt %". Z5 has higher viscosity and better effect in improving water-oil fluidity ratio.

[0133] (6) Comparing Z6 with Z1, Z1 satisfies the conditions that "the content of viscosity reducer is 0.01 to 3.00 wt %, and the content of zwitterionic surfactant is 0.05 to 5.00 wt %". Z1 has higher viscosity and better effect in improving water-oil fluidity ratio.

[0134] (7) Comparing Z7 with Z1, Z1 uses a betaine-based zwitterionic surfactant, which has a higher viscosity and a better effect in improving the water-oil fluidity ratio.

[0135] Test Example 2

[0136] This test example is used to illustrate the viscosity reduction performance test process of the viscosity reduction oil displacement composition provided by the present disclosure on heavy oil.

[0137] The oil sample used in this test example is heavy oil from a block in Henan Oilfield, with a surface degassing viscosity of 4315 mPa·s at 50°C and a water content of 15.3% by weight.

[0138] The viscosity reduction performance test is as follows:

[0139] (1) Place the heavy oil sample in a water bath at 50°C for 30 min.

[0140] (2) In the viscosity reduction experiment, the viscosity reduction flooding compositions in the examples and comparative examples were mixed with heavy oil samples at a mass ratio of 3:7, stirred for 10 min at a constant temperature of 50°C, and the emulsion viscosity at 50°C was tested using HAKKEMARS III. The test results and viscosity reduction ratio are shown in Table 3. Wherein, viscosity reduction ratio = (heavy oil viscosity - emulsion viscosity) / heavy oil viscosity × 100%.

[0141] Table 3

[0142] Viscosity reduction oil displacement composition system Emulsion viscosity / mPa·s Viscosity reduction rate / % Z1 56.1 98.7 DZ1 1566.3 63.7 DZ2 1221.1 71.7 DZ3 824.2 80.9 Z2 64.7 98.5 Z3 60.4 98.6 DZ4 953.6 77.9 DZ5 1531.8 64.5 Z4 418.6 90.3 Z5 30.2 99.3 Z6 703.3 83.7 Z7 522.1 87.9

[0143] According to the viscosity reduction performance test data in Table 3 above:

[0144] (1) The viscosity reduction oil displacement compositions Z1 to Z7 provided in the present disclosure can effectively reduce the viscosity of heavy oil samples, and the viscosity reduction rate can reach more than 83%, preferably more than 90%;

[0145] (2) Comparing Z1 with DZ1 to DZ3, Z1 uses the viscosity reducer A provided by the present disclosure, and the viscosity reducer A contains structural unit (I), structural unit (II) and structural unit (III). Z1 has a higher viscosity reduction rate and better viscosity reduction effect;

[0146] (3) Comparing Z3 with DZ4-DZ5, Z3 uses the viscosity reducer C provided by the present disclosure, and Z3 has a higher viscosity reduction rate and better viscosity reduction effect;

[0147] (4) Comparing Z4 with Z1, the molar ratio of the first monomer, the second monomer and the third monomer in the reaction monomers of the viscosity reducer A used in Z1 satisfies 1:(1-3):(1-2), and Z1 has a higher viscosity reduction rate and a better viscosity reduction effect;

[0148] (5) Comparing Z5 with Z1, Z5 satisfies the conditions that "the content of the viscosity reducer is 0.1 to 1.0 wt %, and the content of the zwitterionic surfactant is 0.3 to 1.0 wt %". Z5 has a higher viscosity reduction rate and better viscosity reduction effect.

[0149] (6) Comparing Z6 with Z1, Z1 satisfies the conditions that "the content of the viscosity reducer is 0.01 to 3.00% by weight, and the content of the zwitterionic surfactant is 0.05 to 5.00% by weight", and Z1 has a higher viscosity reduction rate and better viscosity reduction effect;

[0150] (7) Comparing Z7 with Z1, Z1 uses a betaine-based zwitterionic surfactant, and Z1 has a higher viscosity reduction rate and better viscosity reduction effect.

[0151] Test Example 3

[0152] This test example is used to illustrate the oil displacement performance test process of the viscosity reduction oil displacement composition provided by the present disclosure.

[0153] (1) Dry the artificial core in an oven at 120°C to constant weight, and accurately measure the core size and gas permeability.

[0154] (2) After saturating the core with distilled water, measure the core pore volume. Take the core saturated with heavy oil from a block in Henan Oilfield after dehydration and record the mass of saturated crude oil (m1).

[0155] (3) At 50°C, a field water sample (mineralization degree 7240 mg / L) from a block of Henan Oilfield was continuously injected into the oil-saturated core until the oil content in the primary displacement fluid was less than 1% by weight, i.e., the heavy oil retained in the pores could not be displaced. Then, 0.5 PV of the viscosity-reducing oil displacement composition prepared in the embodiment and the comparative example (as a displacement fluid) was respectively injected, and the field mineralized water was injected again to displace the oil until the oil content in the displacement fluid was less than 1% by weight.

[0156] On the basis of the primary drive, the oil volume m2 (mass) driven out in the secondary drive process is taken as the heavy oil recovery enhancement, and the enhanced recovery factor = m2 / m1×100%. The results are listed in Table 4 below.

[0157] In the above process, the core gas permeability was measured by using a permeability meter produced by Dongda Shiyi Company; and the oil displacement test was evaluated by using a simulated oil displacement evaluation device produced by Dongda Shiyi Company.

[0158] Table 4

[0159] Viscosity reduction oil displacement composition Improved oil recovery / % Z1 20.3 DZ1 5.3 DZ2 8.3 DZ3 12.7 Z2 21.7 Z3 21.4 DZ4 10.3 DZ5 5.7 Z4 18.7 Z5 25.5 Z6 15.3 Z7 16.9

[0160] According to the oil displacement performance test data in Table 4 above, it can be seen that:

[0161] (1) The viscosity reduction oil displacement compositions Z1 to Z7 provided in the present disclosure can effectively increase the recovery factor by 15.3% to 25.5% on the basis of water flooding, and have a good effect of increasing the recovery factor;

[0162] (2) Z1 is compared with DZ1 to DZ3. Z1 uses the viscosity reducer A provided by the present disclosure, and the viscosity reducer A contains structural unit (I), structural unit (II) and structural unit (III). Z1 has a higher oil recovery factor and better displacement effect;

[0163] (3) Comparing Z3 with DZ4-DZ5, Z3 uses the viscosity reducer C provided by the present disclosure, and Z3 has a higher oil recovery and better displacement effect;

[0164] (4) Comparing Z4 with Z1, the molar ratio of the first monomer, the second monomer and the third monomer in the reaction monomers of the viscosity reducer A used in Z1 satisfies 1:(1-3):(1-2), and Z1 has a higher enhanced oil recovery and better displacement effect;

[0165] (5) Comparing Z5 with Z1, Z5 satisfies the requirement of "the content of viscosity reducer is 0.1-1.0 wt %, and the content of zwitterionic surfactant is 0.3-1.0 wt %", and Z5 has a higher enhanced oil recovery and better displacement effect;

[0166] (6) Comparing Z6 with Z1, Z1 satisfies the requirement that "the content of viscosity reducer is 0.01 to 3.00 wt %, and the content of zwitterionic surfactant is 0.05 to 5.00 wt %". Z1 has a higher enhanced oil recovery and better displacement effect.

[0167] (7) Comparing Z7 with Z1, Z1 uses a betaine-based zwitterionic surfactant, and Z1 has a higher enhanced oil recovery and better displacement effect.

[0168] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0169] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0170] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A viscosity reduction oil displacement composition, characterized in that: The invention comprises a viscosity reducer, a zwitterionic surfactant and water; the viscosity reducer comprises a terpolymer, and the terpolymer comprises a structural unit (I), a structural unit (II) and a structural unit (III) as shown in the following formula: （Ⅰ）， （Ⅱ）， （Ⅲ）； Wherein, R1 is selected from C2 to C9 alkyl; R2 to R 10 are each independently selected from hydrogen or deuterium, m is 0, 1, 2, 3 or 4; n is 0, 1, 2, 3 or 4; M + for Na + or K + ; The molar ratio of the structural unit (I), the structural unit (II) and the structural unit (III) is (9~30):(10~70):(10~70).

2. The composition according to claim 1, characterized in that Based on the total weight of the composition, the content of the viscosity reducer is 0.01-3.00% by weight, the content of the zwitterionic surfactant is 0.05-5.00% by weight, and the rest is water.

3. The composition according to claim 2, characterized in that Based on the total weight of the composition, the content of the viscosity reducer is 0.1-1.0 weight %, the content of the zwitterionic surfactant is 0.3-1.0 weight %, and the rest is water.

4. The composition according to claim 1, characterized in that The zwitterionic surfactant is selected from one or more of alkyl betaine and its derivatives.

5. The composition according to claim 1, characterized in that The zwitterionic surfactant is selected from one or more of dodecyl dimethyl betaine, tetradecyl dimethyl betaine, hexadecyl dimethyl betaine, octadecyl dimethyl betaine, dodecyl dihydroxyethyl betaine, dodecyl dihydroxyethyl betaine, tetradecyl sulfopropyl betaine, hexadecyl dimethyl sulfopropyl betaine, octadecyl sulfopropyl betaine, dodecyl hydroxypropyl phosphate betaine, tetradecyl hydroxypropyl phosphate betaine and hexadecyl hydroxypropyl phosphate betaine.

6. The composition according to claim 1, characterized in that In the viscosity reducer, the molar ratio of the structural unit (I), the structural unit (II) and the structural unit (III) is (10-20): (50-70): (20-40).

7. The composition according to claim 1, characterized in that The weight average molecular weight of the viscosity reducer is 2×10 5 ~5×10 5 .

8. The composition according to claim 7, characterized in that The weight average molecular weight of the viscosity reducer is 2.5×10 5 ~5×10 5 .

9. The composition according to claim 1, characterized in that The terpolymer comprises a structure represented by the following formula (1) and / or formula (2): Formula (1); Wherein, x, y, and z are all integers greater than or equal to 1, and x / (x+y+z) is 10% to 70%; y / (x+y+z) is 9% to 30%; z / (x+y+z) is 10% to 70%; Formula (2); Among them, e, f, and g are all integers greater than or equal to 1, and g / (e+f+g) is 10%~70%; f / (e+f+g) is 9%~30%; and e / (e+f+g) is 10%~70%.

10. The composition according to claim 9, characterized in that In formula (1), x / (x+y+z) is 50%~70%; y / (x+y+z) is 10%~20%; z / (x+y+z) is 20%~40%; In formula (2), g / (e+f+g) is 50%~70%; f / (e+f+g) is 10%~20%; and e / (e+f+g) is 20%~40%.

11. The composition according to claim 1, characterized in that R1 is selected from C2 to C6 alkyl, R2 to R 10 are all hydrogen, m is 0, 1 or 2; n is 0, 1 or 2.

12. The composition according to claim 1, characterized in that The viscosity reducer is prepared by a preparation method comprising the following steps: Under polymerization reaction conditions, the reaction monomers are contacted with an initiator and a chain transfer agent in an organic solvent for reaction; the reaction monomers include: a first monomer having a structure shown in formula (IV), a second monomer having a structure shown in formula (V), and a third monomer having a structure shown in formula (VI): （Ⅳ）， （Ⅴ）， （Ⅵ）； In formula (IV), M + for Na + or K + ; The molar ratio of the first monomer, the second monomer and the third monomer in the reaction monomer is 1:(1~5):(1~5).

13. The composition according to claim 12, characterized in that The first monomer is selected from one or more of sodium p-styrene sulfonate, sodium m-styrene sulfonate, potassium p-styrene sulfonate and potassium m-styrene sulfonate; The second monomer is selected from one or more of acrylamide, deuterated acrylamide and crotonamide; The third monomer is selected from one or more of vinyl butyrate, vinyl nonanoate, 2-propylene nonanoate and vinyl hexanoate.

14. The composition according to claim 13, characterized in that The molar ratio of the first monomer, the second monomer and the third monomer in the reaction monomers is 1:(1-3):(1-2).

15. The composition according to claim 12, characterized in that The polymerization reaction conditions include: under an inert atmosphere, a reaction temperature of 50 to 90° C., and a reaction time of 2 to 10 hours; The inert atmosphere comprises one or more of nitrogen, helium and argon.

16. The composition according to claim 15, characterized in that The polymerization reaction conditions include: reaction temperature of 60-70° C. and reaction time of 4-5 h.

17. The composition according to claim 12, characterized in that The initiator is selected from at least one of an azo compound initiator and a peroxide initiator; The chain transfer agent is selected from at least one of aliphatic mercaptans; The organic solvent is benzene or a benzene substituted product.

18. The composition according to claim 17, characterized in that The initiator is selected from at least one of azobisisobutyronitrile, azobisisoheptylnitrile, dimethyl azobisisobutyrate, benzoyl peroxide and lauroyl peroxide; The chain transfer agent is dodecyl mercaptan; The organic solvent is toluene.

19. The composition according to claim 17, characterized in that The added weight concentration of the initiator is 0.5 wt % to 1.5 wt % based on the total weight of the reaction monomers; The chain transfer agent is added at a concentration of 0.1 wt % to 5.0 wt % based on the total weight of the reaction monomers.

20. The composition according to claim 19, characterized in that The added weight concentration of the initiator is 1.0 wt % to 1.5 wt % based on the total weight of the reaction monomers; The chain transfer agent is added at a concentration of 1.0 wt % to 3.0 wt % based on the total weight of the reactive monomers.

21. A method for preparing a viscosity reduction displacement composition as claimed in any one of claims 1 to 20, characterized in that: include: The viscosity reducer, zwitterionic surfactant and water are mixed under stirring.

22. Use of the viscosity-reducing oil displacement composition according to any one of claims 1 to 20 in cold recovery of heavy oil.

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