Hydrolyzed polymer, preparation method thereof, in-crack hydrolyzed polymer cleanup additive for fracturing and application of in-crack hydrolyzed polymer cleanup additive

Abstract

The invention relates to the field of oil and gas recovery engineering of oil and gas reservoirs, and discloses a hydrolytic polymer, a preparation method thereof, an in-crack hydrolytic polymer cleanup additive for fracturing and application. The hydrolytic polymer comprises: a first structural unit provided by a styrene monomer; the second structural unit is provided by a maleic anhydride monomer; an optional structural unit III is provided by amine and / or ammonium monomers with olefin double bonds; the fourth structural unit is provided by a fluorine-containing monomer with an olefin double bond; the molar content ratio of the second structural unit to the first structural unit to the third structural unit is 1: (3-7): (0-2.5); and the content of the structural unit IV is not less than 0.05 wt%. The discharge aiding agent disclosed by the invention not only overcomes the defects of chromatographic separation and the like in the near-shaft stratum mass adsorption and migration process of the existing discharge aiding agent, but also has relatively low surface and interfacial tension after hydrolysis, and has extremely high application value.

Description

Technical Field

[0001] The invention relates to the field of oil and gas reservoir production engineering, and in particular to a hydrolyzable polymer and a preparation method thereof, an intra-fracture hydrolyzable polymer drainage aid for fracturing and an application thereof. Background Art

[0002] In the field of petroleum, fracturing refers to a method of using hydraulic force to create cracks in oil and gas layers during oil or gas production, also known as hydraulic fracturing. Fracturing is the process of artificially creating cracks in the formation to improve the flow environment of oil and gas underground and increase the production of oil and gas wells. It plays an important role in improving the flow conditions at the bottom of oil and gas wells, slowing down interlayer flow and improving the utilization of oil and gas layers.

[0003] At present, the main method of fracturing is hydraulic fracturing. Hydraulic fracturing is to inject fluid into the well at high speed by a ground high-pressure pump truck group, and use the high pressure at the bottom of the well to break the rock of the oil and gas layer to produce cracks. In order to prevent the pressure from dropping after the pump truck stops working and the cracks from closing again, sand with a density several times greater than that of the formation is mixed into the injected liquid after the formation is broken, and enters the cracks together with the fluid and stays in the cracks permanently, supporting the cracks in an open state, so that the oil and gas flow environment can be improved for a long time. At present, hydraulic fracturing technology is very mature, and the effect of increasing oil and gas well production is obvious. It has long become the preferred common technology. Especially for oil and gas layers with small oil and gas flow channels, that is, low permeability oil and gas layers, the effect of increasing production is particularly prominent. Furthermore, ultra-low and ultra-low permeability oil and gas reservoirs and shale oil and gas reservoirs are the main objects for further exploitation in the future. The reason why they can be developed is related to the fracture system (natural fractures and hydraulic fracturing artificial fractures) existing in their oil and gas reservoirs.

[0004] Fracturing fluid is an important part of fracturing technology. Its main function is to create cracks and transport proppant along the opened cracks, so the viscosity of the fluid is crucial. Successful fracturing operations require that the fluid not only has high viscosity in the cracks, but also can break gel quickly; can be quickly returned after the operation; can well control the liquid loss; has low friction during pumping; and is economically feasible. Drainage aid is one of the important adjuvants in fracturing fluid, which significantly reduces the oil-water interfacial tension and the flow resistance of the liquid in the core, achieving efficient drainage.

[0005] At present, the drainage aids used in fracturing fluids are mainly fluorocarbon surfactants or their composites formed by compounding with other surfactants. Surfactants have ionic polar heads or lone pairs of electrons, and are easily adsorbed on the formation. During the construction process, they will be adsorbed in large quantities in the formation near the wellbore of the fracturing wellbore, resulting in a loss of effective concentration, and cannot reach the far end of the fracture in a large concentration. In addition, the compound drainage agent is formulated by several surfactants, and "chromatographic separation" will occur during the migration of the reservoir, that is, the multiple components cannot be kept uniformly distributed all the time, so the comprehensive performance achieved in indoor experimental tests cannot be achieved.

[0006] Therefore, how to overcome the technical problems of existing drainage aids, such as large amount of adsorption in the near-wellbore formation, low effective concentration, "chromatographic separation" during the migration of conventional compound drainage agents, and failure to achieve the comprehensive performance achieved by compound drainage agents in indoor experimental tests, and provide a new type of drainage agent, is a technical problem that needs to be solved at present. Summary of the invention

[0007] As mentioned above, existing drainage aids have the disadvantages of large amount of adsorption near the wellbore formation and "chromatographic separation" during migration. The present invention provides a hydrolyzable polymer and its preparation method, a hydrolyzable polymer drainage aid for fracturing and its application. The drainage aid of the present invention is a polymer surfactant, not a formula. Unlike traditional formula drainage aids, "chromatographic separation" will not occur during reservoir migration (i.e., multiple components cannot be uniformly distributed all the time), and the comprehensive performance achieved in indoor experimental tests cannot be achieved. The hydrolyzable polymer and intra-fracture hydrolyzable polymer drainage aid of the present invention solve the technical problem that conventional formula drainage aids are prone to "chromatographic separation" and the comprehensive performance achieved in actual applications is far from that achieved in experimental tests. They also solve the technical problem that conventional drainage aids are adsorbed prematurely during migration, resulting in a large loss of drainage agents. Moreover, the hydrolyzable polymer and intra-fracture hydrolyzable polymer drainage aid of the present invention have higher surface activity and lower surface-interfacial tension after hydrolysis, can meet the needs of fracturing drainage aids for ultra-low permeability oil and gas reservoirs, shale oil and gas, etc., and have extremely high application value.

[0008] Specifically, taking the intra-fracture hydrolyzable polymer drainage agent for fracturing as an example, the intra-fracture hydrolyzable polymer drainage agent for fracturing of the present invention is in a liquid state as a finished product, which is easy to pump; after meeting water, the drainage agent is precipitated in the fracturing fluid in a solid form because the solvent is soluble in water, and enters the formation together with the fracturing fluid, and migrates to the far end as the fracture extends; since the hydrolyzable functional groups in the polymer molecular structure of the drainage agent require a certain amount of time to hydrolyze, the drainage agent is in a solid form during the migration process to avoid premature adsorption near the wellbore; when it reaches the far end of the fracture, it will quickly dissolve (tens of minutes) during the process of soaking the well (several days or weeks) to play a role; and since the drainage agent is a polymer surfactant and not a formula, it will not undergo "chromatographic separation" during the reservoir migration process like the traditional formula drainage agent, that is, the multiple components cannot always remain evenly distributed, and the comprehensive performance achieved in indoor experimental tests cannot be achieved. The groups of the polymer surfactant of the present invention that play a role do not have "chromatographic separation", can act synergistically, have high surface activity, and have low surface tension, and can meet the needs of fracturing and drainage assistance for ultra-low permeability oil and gas reservoirs, shale oil and gas, etc.

[0009] The first aspect of the present invention is to provide a hydrolyzable polymer comprising four structural units respectively connected by copolymerization of olefin double bonds: structural unit 1, structural unit 2, structural unit 4 and optional structural unit 3; wherein structural unit 1 is provided by a styrene monomer;

[0010] Structural unit two is provided by maleic anhydride monomers;

[0011] Structural unit three is provided by amine and / or ammonium monomers having an olefin double bond;

[0012] Structural unit four is provided by a fluorine-containing monomer having an olefin double bond;

[0013] Wherein, the molar content ratio of the structural unit 2 to the structural unit 1 and the structural unit 3 is 1:(3-7):(0-2.5);

[0014] Based on the total mass of all structural units of the hydrolyzable polymer being 100 wt %, the content of structural unit four in the hydrolyzable polymer is not less than 0.05 wt %.

[0015] According to the present invention, the molar content ratio of the structural unit two to the structural unit one and the structural unit three is 1:(3-7):(0-2.5). In a preferred embodiment of the present invention, the molar content ratio of the structural unit two to the structural unit one and the structural unit three is 1:(4-6):(0-2).

[0016] According to the present invention, the hydrolyzable polymer contains four structural units connected by olefin double bonds: structural unit one, structural unit two, structural unit four and optional structural unit three, that is, it may not contain structural unit three, but preferably contains structural unit one, structural unit two, structural unit four and structural unit three, that is, the content of structural unit three is not 0.

[0017] According to the present invention, based on the total mass of all structural units of the hydrolyzable polymer as 100wt%, the content of structural unit four in the hydrolyzable polymer is not less than 0.05wt%, preferably 0.05wt%-1wt%. In a more preferred embodiment of the present invention, based on the total mass of all structural units of the hydrolyzable polymer as 100wt%, the content of structural unit four in the hydrolyzable polymer is 0.1wt%-0.5wt%.

[0018] According to the present invention, the styrene monomer can be selected from a wide range. In a preferred embodiment of the present invention, the styrene monomer is selected from at least one of styrene, diphenylethylene, and methyl styrene, preferably styrene.

[0019] According to the present invention, the amine and / or ammonium monomer having an olefin double bond can be selected from a wide range. In a preferred embodiment of the present invention, the amine and / or ammonium monomer having an olefin double bond is selected from amine and / or ammonium monomer having an olefin double bond having 8 to 20 carbon atoms; preferably selected from at least one of tetraallylammonium chloride, dimethyldiallylammonium chloride, dodecyldimethylallylammonium chloride, tetradecyldimethylallylammonium chloride, hexadecyldimethylallylammonium chloride and octadecyldimethylallylammonium chloride.

[0020] According to the present invention, the fluorine-containing monomer having an olefin double bond can be selected from a wide range. In a preferred embodiment of the present invention, the fluorine-containing monomer having an olefin double bond is selected from fluorine-containing monomers having an olefin double bond having 6 to 18 carbon atoms, preferably selected from at least one of perfluorohexylethylene, perfluorooctylethylene, perfluorododecylethylene, and 1,8-divinylperfluorooctane.

[0021] The second aspect of the present invention is to provide a method for preparing the hydrolyzable polymer described in the first aspect, comprising copolymerizing monomer raw materials including the styrene monomer, the maleic anhydride monomer, the amine and / or ammonium monomer having an olefin double bond, and the fluorine-containing monomer having an olefin double bond in a solvent in the presence of a protective atmosphere and an initiator to obtain the hydrolyzable polymer.

[0022] In a preferred embodiment of the present invention, the preparation method comprises:

[0023] The solvent is used in at least three parts, and the first part of the solvent is mixed with the maleic anhydride monomer, the amine and / or ammonium monomer having an olefin double bond, and the fluorine-containing monomer having an olefin double bond at a temperature not higher than 30° C. to obtain a solution 1;

[0024] The second part of the solvent and the initiator are mixed under the condition that the initiator temperature is not higher than 30° C. to obtain solution 2; the third part of the solvent and the styrene monomer are mixed to obtain solution 3;

[0025] When the temperature of solution three is 75-85°C, solution one and solution two are added dropwise to solution three, and the temperature of the reaction mixture is controlled not to be higher than 90°C during the addition process, preferably when the temperature of the reaction mixture is below 85°C, until the addition is completed, and the preferred addition time is 90-180min; after the addition is completed, the reaction mixture is kept at 75-85°C for 0.5-1.5h;

[0026] Preferably, during the dropwise addition and reaction process, the mixed solution is mixed at a rotation speed of 80-200 r / min.

[0027] As mentioned above, according to the present invention, the molar ratio of the maleic anhydride monomer to the styrene monomer, the amine having an olefin double bond and / or the ammonium monomer is 1:(3-7):(0-2.5). In a preferred embodiment of the present invention, the molar ratio of the maleic anhydride monomer to the styrene monomer, the amine having an olefin double bond and / or the ammonium monomer is 1:(4-6):(0-2);

[0028] As mentioned above, according to the present invention, based on the total mass of all monomer raw materials as 100wt%, the content of the fluorine-containing monomer having an olefin double bond is not less than 0.05wt%, preferably 0.05wt%-1wt%. In a preferred embodiment of the present invention, based on the total mass of all monomer raw materials as 100wt%, the content of the fluorine-containing monomer having an olefin double bond is 0.1wt%-0.5wt%.

[0029] According to the present invention, the ratio of the total mass of the solvent to all monomer raw materials can be selected within a wide range. In a preferred embodiment of the present invention, the ratio of the total mass of the solvent to all monomer raw materials is (1-20):1, more preferably (1.5-4):1.

[0030] According to the present invention, the amount of the initiator can be selected within a wide range. In a preferred embodiment of the present invention, the amount of the initiator is 0.1%-0.5% of the total mass of all monomer raw materials.

[0031] As described in the first aspect, according to the present invention, the styrene-based monomer can be selected from a wide range. In a preferred embodiment of the present invention, the styrene-based monomer is selected from at least one of styrene, diphenylethylene, and methyl styrene, preferably styrene.

[0032] According to the present invention, the amine and / or ammonium monomer having an olefin double bond can be selected from a wide range. In a preferred embodiment of the present invention, the amine and / or ammonium monomer having an olefin double bond is selected from amine and / or ammonium monomer having an olefin double bond having 8 to 20 carbon atoms, preferably selected from at least one of tetraallylammonium chloride, dimethyldiallylammonium chloride, dodecyldimethylallylammonium chloride, tetradecyldimethylallylammonium chloride, hexadecyldimethylallylammonium chloride and octadecyldimethylallylammonium chloride.

[0033] According to the present invention, the fluorine-containing monomer having an olefin double bond can be selected from a wide range. In a preferred embodiment of the present invention, the fluorine-containing monomer having an olefin double bond is selected from at least one of perfluorohexylethylene, perfluorooctylethylene, perfluorododecylethylene, and 1,8-divinylperfluorooctane.

[0034] According to the present invention, the solvent can be selected from a wide range. In a preferred embodiment of the present invention, the solvent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, and acetone, preferably N,N-dimethylformamide;

[0035] According to the present invention, the initiator can be selected from a wide range. In a preferred embodiment of the present invention, the initiator is at least one of azobisisobutyronitrile, benzoyl peroxide, and di-tert-butyl peroxide, preferably azobisisobutyronitrile.

[0036] The third aspect of the present invention is to provide a hydrolyzable polymer drainage aid, which contains the hydrolyzable polymer described in the first aspect, or the hydrolyzable polymer prepared by the preparation method described in the second aspect, and an optional solvent; preferably,

[0037] The hydrolyzable polymer drainage aid contains a solvent, and the hydrolyzable polymer drainage aid is in liquid state; more preferably,

[0038] The hydrolyzable polymer discharge aid is a reaction mixture obtained as follows: in the presence of a protective atmosphere and an initiator, monomer raw materials including the styrene monomer, the maleic anhydride monomer, the amine and / or ammonium monomer with an olefin double bond, and the fluorine-containing monomer with an olefin double bond are copolymerized in a solvent.

[0039] The fourth aspect of the present invention is to provide a fracturing fluid composition, comprising a fracturing fluid and the hydrolyzable polymer described in the first aspect, or the hydrolyzable polymer prepared by the preparation method described in the second aspect, or the hydrolyzable polymer drainage aid described in the third aspect, wherein the fracturing fluid contains water;

[0040] Preferably, the mass ratio of the hydrolyzable polymer to water in the fracturing fluid composition is (0.05-1):100.

[0041] According to the present invention, the hydrolyzable polymer of the present invention may be directly added to the fracturing fluid, or a hydrolyzable polymer drainage aid (i.e., containing a hydrolyzable polymer and a solvent, which is a liquid) may be added, and both can achieve the present invention. Preferably, the hydrolyzable polymer drainage aid is directly added.

[0042] The fifth aspect of the present invention is to provide a polymer surfactant comprising four structural units respectively connected by copolymerization of olefin double bonds: structural unit 1, structural unit 2, structural unit 4 and optional structural unit 3;

[0043] Wherein, structural unit one is provided by styrene monomer;

[0044] Structural unit 2 is

[0045] Structural unit three is provided by amine and / or ammonium monomers having an olefin double bond;

[0046] Structural unit four is provided by a fluorine-containing monomer having an olefin double bond;

[0047] Wherein, the molar content ratio of the structural unit 2 to the structural unit 1 and the structural unit 3 is 1:(3-7):(0-2.5), preferably 1:(4-6):(0-2);

[0048] Based on the total mass of all structural units of the polymeric surfactant as 100wt%, the content of structural unit 4 in the polymeric surfactant is not less than 0.05wt%, preferably 0.05wt%-1wt%, more preferably 0.1wt%-0.5wt%;

[0049] Preferably, the polymer surfactant is obtained by hydrolysis of the hydrolyzable polymer; the hydrolyzable polymer is the hydrolyzable polymer described in the first aspect, or the hydrolyzable polymer prepared by the preparation method described in the second aspect.

[0050] For the sake of explanation, as an example, the polymer degassing agent of the present invention can be prepared and used as follows:

[0051] (1) Synthesis method

[0052] The reaction was carried out using DMF as solvent.

[0053] The reactants are polymerized from a hydrophobic monomer styrene, a hydrophilic monomer maleic anhydride, an amine / ammonium hydrophilic monomer and one or more fluorine-containing monomers.

[0054] Pre-mixing outside the kettle is adopted. Pre-mixing: ①Part of the solvent DMF, hydrophilic monomer maleic anhydride, amine / ammonium hydrophilic monomer and one or more fluorine-containing monomers are dissolved at room temperature (≤30℃). ②Part of the solvent DMF, initiator azobisisobutyronitrile are dissolved at room temperature (≤30℃). Note that the temperature should not be too high to prevent accidental polymerization of monomers due to impurities.

[0055] First add DMF and styrene into the kettle, then heat to 75-85℃ and stir at 80-200r / min;

[0056] Use a diaphragm pump to slowly drop the prepared solutions ① and ② into the kettle, respectively, and control the dropping time to 90-180 minutes. During this period, the temperature in the kettle cannot exceed 90℃. If it exceeds 90℃, stop dropping, and continue dropping when the temperature drops below 85℃ until all the solutions are added. Keep the temperature at 75-85℃ and continue the reaction for 0.5-1.5 hours.

[0057] After the final reaction was completed, the reactants in the kettle turned into a light yellow, uniform, stable, slightly viscous liquid.

[0058] (2) Principle of hydrolysis in cracks

[0059] The styrene polymer part in the polymer provides hydrophobicity, and maleic anhydride provides two carboxyl groups after hydrolysis ( Figure 1 ), the cationic monomer provides a cationic head and partial hydrophobicity, and a small amount of fluorinated monomer can further reduce the surface interfacial tension.

[0060] The product itself is a liquid with DMF as solvent, which is easy to pump. When the product is pumped into the fracturing fluid, DMF will dissolve in water. At this time, because the anhydride part of the polymer has not yet been hydrolyzed, the whole molecule is highly hydrophobic. Under stirring, it will precipitate in the form of loose solid particles and enter the wellbore with the fracturing fluid, further enter the fracture system generated by fracturing, and gradually move to the far end of the fracture network.

[0061] The fracturing operation has a large displacement (10-20m / min). 3 ), the precipitated solid polymer will quickly (within a few minutes) enter the formation fracture system with the fracturing fluid, and migrate with the fracturing gap, avoiding premature adsorption near the wellbore, so that it is easier to approach the oil layer. When it reaches the distal gap, it will quickly dissolve (tens of minutes) during the soaking process (several days or weeks). (After the fracturing is completed, a well will be soaked according to the specific situation, usually for a few days or longer, and the wellhead will be closed. After the designed soaking time is reached, the well will be opened for backflow (part of the fracturing fluid will be discharged, and oil and gas will gradually appear). Because the dissolution time of the polymer drainage agent is short, most of it will be dissolved during fracturing, and a small amount of undissolved will also be completely dissolved in this process), thereby obtaining a hydrolyzed polymer surfactant and playing a role.

[0062] (3) Surface interfacial tension test

[0063] The surface interfacial tension test is carried out in accordance with standards SY / T 5370 and Q / SH 3580 0160.

[0064] The synthetic polymer drainage agent is a light yellow liquid. The performance test of its hydrolyzate shows that the interfacial tension of a 0.1% aqueous solution (based on the mass of the polymer in the polymer drainage agent) is less than 1mN / m and the surface tension is less than 23mN / m. (Note: At present, it is generally required that the surface tension of a 0.1% aqueous solution of the drainage agent is ≤28mN / m; but for wells with high drainage requirements, the surface tension is often required to be ≤23mN / m).

[0065] In summary, the invention uses hydrophobic monomer styrene, hydrolyzable hydrophilic monomer maleic anhydride and the like as raw materials and DMF as solvent to synthesize a fracture hydrolyzable polymer drainage aid for fracturing. The product itself is a liquid and is easy to pump. When pumped into the fracturing fluid, the anhydride part of the polymer has not yet been hydrolyzed, and the entire molecule exhibits strong hydrophobicity. Under stirring, as the solvent dissolves in water, the product will precipitate in the form of loose solid particles, and enter the wellbore together with the fracturing fluid, migrate to the far end of the fracture network, and gradually dissolve. The hydrolyzate of the polymer of the present invention has a relatively low surface tension and can meet the needs of fracturing drainage aids such as ultra-low permeability oil and gas reservoirs and shale oil and gas.

[0066] The sixth aspect of the present invention is to provide an application of the hydrolyzable polymer described in the first aspect, or the hydrolyzable polymer prepared by the preparation method described in the second aspect, or the hydrolyzable polymer drainage agent described in the third aspect, or the fracturing fluid composition described in the fourth aspect, or the polymer surfactant described in the fifth aspect in the petroleum field; preferably,

[0067] Application in the field of fracturing and recovery in oil production.

[0068] Preferably, the application includes:

[0069] The hydrolyzable polymer or the hydrolyzable polymer drainage aid is mixed with a fracturing fluid to obtain a fracturing fluid composition containing a hydrolyzable polymer, wherein the hydrolyzable polymer exists in the form of solid particles;

[0070] The hydrolyzable polymer is transported with the fracturing fluid to the fracture system generated by fracturing and migrates to the far end of the fracture network;

[0071] When the hydrolysis conditions of the hydrolyzable polymer are reached, the hydrolyzable polymer is hydrolyzed and dissolved in water to obtain a polymer surfactant;

[0072] The polymeric surfactant is contacted with an oil reservoir.

[0073] According to the present invention, there is no particular restriction on the hydrolysis conditions of the hydrolyzable polymer. When it encounters water, the polymer drainage aid begins to dissolve. Because of different molecular structures and temperatures, the dissolution time is also different. It has been verified that in the presence of water, regardless of the temperature, the polymer drainage aid of the present invention will be completely hydrolyzed in 6 hours, that is, a polymer surfactant is obtained. For example, when the temperature is 90°C, the hydrolysis time is about 5-20 minutes.

[0074] From the above analysis, it can be seen that the present invention has the following advantages compared with the prior art:

[0075] The drainage aid of the present invention is a polymer surfactant, not a formula, and will not undergo "chromatographic separation" (i.e., multiple components cannot be uniformly distributed all the time) during the migration of the reservoir like the traditional formula drainage aid, and cannot achieve the comprehensive performance achieved during the indoor experimental test. The hydrolyzable polymer and the intra-fracture hydrolyzable polymer drainage aid of the present invention solve the technical problem that the conventional formula drainage aid is prone to "chromatographic separation" and the comprehensive performance achieved in practical applications is far from that achieved during the experimental test, and solves the technical problem that the conventional drainage aid is adsorbed too early during the migration process, resulting in a large loss of the drainage aid. Moreover, the hydrolyzable polymer and intra-fracture hydrolyzable polymer drainage aid of the present invention have higher surface activity and lower surface-interfacial tension after hydrolysis, and can meet the needs of fracturing drainage aids such as ultra-low permeability oil and gas reservoirs and shale oil and gas, and have extremely high application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Figure 1 Schematic diagram of partial hydrolysis of anhydride in polymer. DETAILED DESCRIPTION

[0077] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0078] (1) Raw materials

[0079] ①Monomer:

[0080] Styrene molecular weight 104.14 boiling point 145.2℃

[0081] Maleic anhydride (Maleic anhydride) molecular weight 98.06

[0082] Tetraallyl ammonium chloride molecular weight 135.64

[0083] Dimethyldiallylammonium chloride molecular weight 161.67

[0084] Dodecyl dimethyl allyl ammonium chloride molecular weight 289.93

[0085] Tetradecyl dimethyl allyl ammonium chloride molecular weight 317.69

[0086] Hexadecyl dimethyl allyl ammonium chloride molecular weight 346.04

[0087] Octadecyl dimethyl allyl ammonium chloride molecular weight 374.09

[0088] Perfluorohexylethylene molecular weight 346.09

[0089] Perfluorooctylethylene molecular weight 446.10

[0090] Perfluorododecylethylene molecular weight 646.13

[0091] 1,8-Bisvinylperfluorooctane Molecular weight 454.15

[0092] Note: Considering the high price of fluorinated monomers and the fact that a certain low surface tension is sufficient for practical application, the preferred amount is 0.1%-0.5% of the total monomer mass.

[0093] ②Solvent: N,N-dimethylformamide (DMF) molecular weight 73.10 boiling point 153°C

[0094] ③Initiator: Azobisisobutyronitrile, molecular weight 164.21

[0095] Unless otherwise specified, the raw materials used in the present invention are conventional commercially available products.

[0096] Comparative Example 1

[0097] (1) Raw materials

[0098] Styrene 416g

[0099] Maleic anhydride 98g

[0100] (2) Process

[0101] The reactants used DMF as solvent, and the total amount of solvent used was the total weight of all monomers, 514 g.

[0102] Pre-mixing outside the autoclave is adopted. Pre-mixing: ① Maleic anhydride is mixed with 98g of solvent DMF of equal mass, and dissolved at room temperature (≤30°C) to obtain solution ①.

[0103] ② The initiator azobisisobutyronitrile is 0.3% of the total mass of the monomers, and 50g of solvent DMF is additionally added to dissolve, and dissolved at room temperature (≤30°C) to obtain solution ②.

[0104] First, add 416 g of DMF and styrene into the kettle, then heat it to 75-85°C and stir at 100 r / min.

[0105] Use a diaphragm pump to slowly add the prepared solutions ① and ② to the kettle, respectively, and control the adding time to 120 minutes. During this period, the temperature in the kettle cannot exceed 90℃. If it exceeds 90℃, stop adding, and continue adding when the temperature drops below 85℃ until all the solutions are added, and keep the temperature at 75-85℃ and continue the reaction for 1 hour.

[0106] After the final reaction is completed, the reactants in the kettle are transformed into a light yellow, uniform, stable, slightly viscous liquid, which serves as a hydrolyzable polymer drainage agent.

[0107] Example 1

[0108] (1) Raw materials

[0109] Styrene 520g

[0110] Maleic anhydride 98g

[0111] Tetraallyl ammonium chloride 271g

[0112] Perfluorododecylethylene 0.45g

[0113] 1,8-Bisvinylperfluorooctane 0.45g

[0114] (2) Process

[0115] Pre-mixing outside the kettle: ① 1200g solvent DMF, hydrophilic monomer maleic anhydride, amine / ammonium hydrophilic monomer and fluorine-containing monomer are dissolved at room temperature (≤30°C) to obtain solution ①.

[0116] ②100g solvent DMF, 2.5g initiator azobisisobutyronitrile, dissolved at room temperature (≤30°C) to obtain solution ②.

[0117] First add DMF and styrene into the kettle, then heat to 75-85℃ and stir at 80r / min;

[0118] Use a diaphragm pump to slowly add the prepared solution ① and solution ② to the kettle respectively, and control the adding time to 160 minutes. During this period, the temperature in the kettle cannot exceed 90℃. If it exceeds 90℃, stop adding, and continue adding when the temperature drops below 85℃ until all the addition is completed, and keep the temperature at 75-85℃ to continue the reaction for 1.5 hours.

[0119] After the final reaction is completed, the reactants in the kettle are transformed into a light yellow, uniform, stable, slightly viscous liquid, namely, a hydrolyzed polymer drainage aid.

[0120] Example 2

[0121] (1) Raw materials

[0122] Styrene 625g

[0123] Maleic anhydride 98g

[0124] Dimethyldiallylammonium chloride 324g

[0125] 1,8-Bisvinylperfluorooctane 5.3g

[0126] (2) Process

[0127] Pre-mixing outside the kettle is adopted. Pre-mixing: ① 4000g solvent DMF, hydrophilic monomer maleic anhydride, amine / ammonium hydrophilic monomer and fluorine-containing monomer are dissolved at room temperature (≤30°C) to obtain solution ①.

[0128] ②200g solvent DMF and 1.2g initiator azobisisobutyronitrile were dissolved at room temperature (≤30°C) to obtain solution ②.

[0129] First add DMF and styrene into the kettle, then heat to 75-85℃ and stir at 100r / min;

[0130] Use a diaphragm pump to slowly add the prepared solution ① and solution ② to the kettle respectively, and control the adding time to 100 minutes. During this period, the temperature in the kettle cannot exceed 90℃. If it exceeds 90℃, stop adding, and continue adding when the temperature drops below 85℃ until all the addition is completed, and keep the temperature at 75-85℃ and continue the reaction for 1 hour.

[0131] After the final reaction is completed, the reactants in the kettle are transformed into a light yellow, uniform, stable, slightly viscous liquid, namely, a hydrolyzed polymer drainage aid.

[0132] Example 3

[0133] (1) Raw materials

[0134] Styrene 416g

[0135] Maleic anhydride 98g

[0136] Dodecyl dimethyl allyl ammonium chloride 579g

[0137] Perfluorododecylethylene 3.3g

[0138] (2) Process

[0139] Pre-mixing outside the kettle is adopted. Pre-mixing: ① 2400g solvent DMF, hydrophilic monomer maleic anhydride, amine / ammonium hydrophilic monomer and fluorine-containing monomer are dissolved at room temperature (≤30°C) to obtain solution ①.

[0140] ②150g solvent DMF and 5g initiator azobisisobutyronitrile were dissolved at room temperature (≤30°C) to obtain solution ②.

[0141] First add DMF and styrene into the kettle, then heat to 75-85℃ and stir at 200r / min;

[0142] Use a diaphragm pump to slowly drop solution ① and solution ② into the kettle respectively, and control the dropping time to 90 minutes. During this period, the temperature in the kettle cannot exceed 90℃. If it exceeds 90℃, stop dropping, and continue dropping when the temperature drops below 85℃ until all the drops are added, and keep the temperature at 75-85℃ to continue the reaction for 0.5h.

[0143] After the final reaction is completed, the reactants in the kettle are transformed into a light yellow, uniform, stable, slightly viscous liquid, namely, a hydrolyzed polymer drainage aid.

[0144] Example 4

[0145] (1) Raw materials

[0146] Styrene 416g

[0147] Maleic anhydride 98g

[0148] Tetradecyl dimethyl allyl ammonium chloride 635g

[0149] 1,8-Bisvinylperfluorooctane 5.8g

[0150] The solvent was DMF, and the amount used was 1200 g.

[0151] The process is the same as that in Example 1 to obtain a hydrolyzable polymer drainage aid.

[0152] Example 5

[0153] (1) Raw materials

[0154] Styrene 416g

[0155] Maleic anhydride 98g

[0156] Hexadecyl dimethyl allyl ammonium chloride 692g

[0157] Perfluorooctylethylene 1.2g

[0158] The solvent was DMF, and the amount used was 1500 g.

[0159] The process is the same as that in Example 1 to obtain a hydrolyzable polymer drainage aid.

[0160] Example 6

[0161] (1) Raw materials

[0162] Styrene 416g

[0163] Maleic anhydride 98g

[0164] Octadecyl dimethyl allyl ammonium chloride 748g

[0165] Perfluorohexylethylene 12.7g

[0166] The solvent was DMF, and the amount used was 1500 g.

[0167] The process is the same as that in Example 1 to obtain a hydrolyzable polymer drainage aid.

[0168] Example 7

[0169] Styrene 416g

[0170] Maleic anhydride 98g

[0171] Perfluorohexylethylene 12.7g

[0172] The solvent was DMF, and the amount used was 1500 g.

[0173] The process is the same as that in Example 1 to obtain a hydrolyzable polymer drainage aid.

[0174] Comparative Example 2

[0175] (1) Raw materials

[0176] Styrene 416g

[0177] Maleic anhydride 98g

[0178] Octadecyl dimethyl allyl ammonium chloride 748g

[0179] The solvent was DMF, and the amount used was 1500 g.

[0180] The process is the same as that in Example 1 to obtain a hydrolyzable polymer drainage aid.

[0181] Test example

[0182] The following experiments were carried out using the polymer drainage aids in the examples and comparative examples:

[0183] A mixed solution of the polymer drainage aid with a concentration of 0.1 wt% was prepared with deionized water based on the mass of the polymer in the polymer drainage aid. The solution was placed at 90°C for hydrolysis for 2 hours, and the surface tension of the hydrolyzate was tested. The interfacial tension of the hydrolyzate was also tested.

[0184] During the experiment, it was found that the polymer drainage aid of the present invention is in a liquid state. After it meets water, the solvent dissolves in water, and the drainage aid precipitates in the fracturing fluid in a solid form. It can be seen that the finished drainage aid of the present invention is in a liquid state, which is convenient for pumping; after it meets water, the solvent dissolves in water, and the drainage aid precipitates in the fracturing fluid in a solid form. In this way, during the migration process, the drainage aid is in a solid form to avoid premature adsorption near the wellbore.

[0185] It is found from the experiment that the polymer drainage aid of the present invention is completely dissolved in the solid form after hydrolysis for 2 hours at a temperature of 90°C, and the polymer drainage aid is hydrolyzed into a polymer surfactant. The detection method of surface tension and interfacial tension is carried out according to standards SY / T 5370 and Q / SH 3580 0160, and the specific results are shown in Table 1.

[0186] From the above verification of the present invention, it can be known that the polymer drainage aid in the embodiment of the present invention is hydrolyzed at a temperature of 90°C for 2 hours to obtain a solution containing a polymer surfactant. After further verification, it is found that in an aqueous environment, the polymer drainage aid of the present invention will be completely hydrolyzed within 6 hours at a temperature greater than 25°C. Since the polymer surfactant in the present invention will not undergo chromatographic separation, the experimental test results of the surfactant of the present invention are equivalent to the results of actual application. It can be seen from the experiment that the hydrolyzate of 0.1wt% polymer has a low surface interfacial tension, most of which is less than 20mN / m; the interfacial tension is less than 0.1mN / m. The polymer surfactant of the present invention has a low surface interfacial tension, which can meet the needs of fracturing drainage of ultra-low permeability oil and gas reservoirs, shale oil and gas, etc., and has a very high application value.

[0187] Table 1 Surface interfacial tension of 0.1% polymer hydrolyzate

[0188]

[0189] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

[0190] All publications, patent applications, patents and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings conventionally understood by those skilled in the art. In the event of a conflict, the definition in this specification shall prevail.

[0191] When this specification uses the prefix "well-known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, etc., the objects introduced by the prefix cover those conventionally used in the art when the present invention was proposed, but also include those that are not commonly used at present but will become recognized in the art as being suitable for similar purposes.

[0192] The endpoints and any values ​​of the ranges disclosed in the present invention document are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be regarded as specifically disclosed in this article.

[0193] In the context of the present specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.

[0194] Moreover, any embodiment described in this document may be freely combined with one or more other embodiments described in this document, and the technical solutions or technical ideas formed thereby are deemed to be part of the original disclosure or original record of the present invention, and should not be regarded as new content that has not been disclosed or anticipated in this document, unless a person skilled in the art considers that the combination is obviously unreasonable.

Claims

1. A hydrolyzable polymer comprising four structural units respectively connected by copolymerization of olefin double bonds: structural unit 1, structural unit 2, structural unit 4 and optional structural unit 3; in, Structural unit one is provided by styrene monomers; Structural unit two is provided by maleic anhydride monomers; Structural unit three is provided by amine and / or ammonium monomers having an olefin double bond; Structural unit four is provided by a fluorine-containing monomer having an olefin double bond; Wherein, the molar content ratio of the structural unit 2 to the structural unit 1 and the structural unit 3 is 1:(3-7):(0-2.5); Based on the total mass of all structural units of the hydrolyzable polymer being 100 wt %, the content of structural unit four in the hydrolyzable polymer is not less than 0.05 wt %.

2. The hydrolyzable polymer according to claim 1, characterized in that: The molar content ratio of the structural unit 2 to the structural unit 1 and the structural unit 3 is 1:(4-6):(0-2); and / or, Based on the total mass of all structural units of the hydrolyzable polymer being 100 wt %, the content of structural unit four in the hydrolyzable polymer is 0.05 wt %-1 wt %, preferably 0.1 wt %-0.5 wt %.

3. The hydrolyzable polymer according to claim 1, characterized in that: The styrene monomer is selected from at least one of styrene, diphenylethylene and methyl styrene, preferably styrene; and / or, The amine and / or ammonium monomer having an olefin double bond is selected from amine and / or ammonium monomer having an olefin double bond having 8 to 20 carbon atoms; preferably at least one selected from tetraallylammonium chloride, dimethyldiallylammonium chloride, dodecyldimethylallylammonium chloride, tetradecyldimethylallylammonium chloride, hexadecyldimethylallylammonium chloride and octadecyldimethylallylammonium chloride; and / or, The fluorine-containing monomer having an olefin double bond is selected from fluorine-containing monomers having olefin double bonds having 6 to 18 carbon atoms, and is preferably selected from at least one of perfluorohexylethylene, perfluorooctylethylene, perfluorododecylethylene, and 1,8-bisvinylperfluorooctane.

4. A method for preparing the hydrolyzable polymer according to any one of claims 1 to 3, comprising copolymerizing monomer raw materials including the styrene monomer, the maleic anhydride monomer, the amine and / or ammonium monomer having an olefin double bond, and the fluorine-containing monomer having an olefin double bond in a solvent in the presence of a protective atmosphere and an initiator to obtain the hydrolyzable polymer.

5. The preparation method according to claim 4, characterized in that The preparation method comprises: The solvent is used in at least three parts, and the first part of the solvent is mixed with the maleic anhydride monomer, the amine and / or ammonium monomer having an olefin double bond, and the fluorine-containing monomer having an olefin double bond at a temperature not higher than 30° C. to obtain a solution 1; Mixing the second part of the solvent and the initiator at a temperature not higher than 30° C. to obtain a second solution; Mixing the third portion of the solvent with the styrene monomer to obtain solution three; When the temperature of solution three is 75-85°C, solution one and solution two are added dropwise to solution three, and the temperature of the reaction mixture is controlled not to be higher than 90°C during the addition process, preferably when the temperature of the reaction mixture is below 85°C, until the addition is completed, and the preferred addition time is 90-180min; after the addition is completed, the reaction mixture is kept at 75-85°C for 0.5-1.5h; Preferably, during the dropwise addition and reaction, the mixed solution is mixed at a rotation speed of 80-200 r / min.

6. The preparation method according to claim 4 or 5, characterized in that: The molar ratio of the maleic anhydride monomer to the styrene monomer, the amine having an olefin double bond and / or the ammonium monomer is 1:(3-7):(0-2.5), preferably 1:(4-6):(0-2); Based on the total mass of all monomer raw materials as 100wt%, the content of the fluorinated monomer having an olefin double bond is not less than 0.05wt%, preferably 0.05wt%-1wt%, more preferably 0.1wt%-0.5wt%; and / or, The total mass ratio of the solvent to all monomer raw materials is (1-20):1, preferably (1.5-4):1; and / or, The amount of the initiator used is 0.1%-0.5% of the total mass of all monomer raw materials.

7. The preparation method according to claim 4 or 5, characterized in that: The styrene monomer is selected from at least one of styrene, diphenylethylene and methyl styrene, preferably styrene; and / or, The amine and / or ammonium monomer having an olefin double bond is selected from amine and / or ammonium monomer having an olefin double bond having 8 to 20 carbon atoms, preferably at least one selected from tetraallylammonium chloride, dimethyldiallylammonium chloride, dodecyldimethylallylammonium chloride, tetradecyldimethylallylammonium chloride, hexadecyldimethylallylammonium chloride and octadecyldimethylallylammonium chloride; and / or, The fluorine-containing monomer having an olefin double bond is selected from at least one of perfluorohexylethylene, perfluorooctylethylene, perfluorododecylethylene and 1,8-bisvinylperfluorooctane; and / or The solvent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide and acetone, preferably N,N-dimethylformamide; and / or, The initiator is at least one of azobisisobutyronitrile, benzoyl peroxide, and di-tert-butyl peroxide, preferably azobisisobutyronitrile.

8. A hydrolyzable polymer drainage aid, comprising the hydrolyzable polymer according to any one of claims 1 to 3, or the hydrolyzable polymer prepared by the preparation method according to any one of claims 4 to 7, and an optional solvent; preferably, The hydrolyzable polymer drainage aid contains a solvent, and the hydrolyzable polymer drainage aid is in liquid state; more preferably, The hydrolyzable polymer discharge aid is a reaction mixture obtained as follows: in the presence of a protective atmosphere and an initiator, monomer raw materials including the styrene monomer, the maleic anhydride monomer, the amine and / or ammonium monomer with an olefin double bond, and the fluorine-containing monomer with an olefin double bond are copolymerized in a solvent.

9. A fracturing fluid composition, comprising a fracturing fluid and a hydrolyzable polymer according to any one of claims 1 to 3, or a hydrolyzable polymer prepared by the preparation method according to any one of claims 4 to 7, or a hydrolyzable polymer drainage aid according to claim 8, wherein the fracturing fluid contains water; Preferably, the mass ratio of the hydrolyzable polymer to water in the fracturing fluid composition is (0.05-1):

100.

10. A polymer surfactant comprising four structural units respectively connected by copolymerization of olefin double bonds: structural unit 1, structural unit 2, structural unit 4 and optionally structural unit 3; in, Structural unit one is provided by styrene monomers; Structural unit 2 is Structural unit three is provided by amine and / or ammonium monomers having an olefin double bond; Structural unit four is provided by a fluorine-containing monomer having an olefin double bond; Wherein, the molar content ratio of the structural unit 2 to the structural unit 1 and the structural unit 3 is 1:(3-7):(0-2.5), preferably 1:(4-6):(0-2); Based on the total mass of all structural units of the polymeric surfactant as 100wt%, the content of structural unit 4 in the polymeric surfactant is not less than 0.05wt%, preferably 0.05wt%-1wt%, more preferably 0.1wt%-0.5wt%; Preferably, the polymer surfactant is obtained by hydrolysis of the hydrolyzable polymer; the hydrolyzable polymer is the hydrolyzable polymer described in any one of claims 1 to 3, or the hydrolyzable polymer prepared by the preparation method described in any one of claims 4 to 7.

11. Use of the hydrolyzable polymer according to any one of claims 1 to 3, or the hydrolyzable polymer prepared by the preparation method according to any one of claims 4 to 7, or the hydrolyzable polymer drainage aid according to claim 8, or the fracturing fluid composition according to claim 9, or the polymer surfactant according to claim 10 in the field of petroleum; preferably, Application in the field of fracturing and recovery in oil production.

12. The use according to claim 11, characterized in that The applications include: The hydrolyzable polymer or the hydrolyzable polymer drainage aid is mixed with a fracturing fluid to obtain a fracturing fluid composition containing a hydrolyzable polymer, wherein the hydrolyzable polymer exists in the form of solid particles; The hydrolyzable polymer is transported with the fracturing fluid to the fracture system generated by fracturing and migrates to the far end of the fracture network; When the hydrolysis conditions of the hydrolyzable polymer are reached, the hydrolyzable polymer is hydrolyzed and dissolved in water to obtain a polymer surfactant; The polymeric surfactant is contacted with an oil reservoir.

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