A hydrolyzable polymer and its preparation method, a fracturing in-fracture hydrolyzable polymer drainage aid and its application

Abstract

This invention relates to the field of oil and gas reservoir production engineering, and discloses a hydrolyzable polymer, its preparation method, a fracturing in-fracture hydrolyzable polymer drainage aid, and its application. The hydrolyzable polymer contains: structural unit one provided by a styrene monomer; structural unit two provided by a maleic anhydride monomer; optionally, structural unit three provided by an amine and / or ammonium monomer having an olefin double bond; and structural unit four provided by a fluorine-containing monomer having an olefin double bond. The molar ratio of structural unit two to structural units one and three is 1:(3-7):(0-2.5); and the content of structural unit four is not less than 0.05 wt%. The drainage aid of this invention overcomes the shortcomings of existing drainage aids, such as excessive adsorption near the wellbore and "chromatographic separation" during migration. Furthermore, it exhibits low interfacial tension after hydrolysis, making it highly valuable for application.

Description

Technical Field

[0001] This invention relates to the field of oil and gas reservoir production engineering, specifically to a hydrolyzable polymer and its preparation method, an in-fracture hydrolyzable polymer drainage aid for fracturing, and its application. Background Technology

[0002] In the petroleum industry, fracturing refers to a method of creating fractures in oil and gas reservoirs using hydraulic force during oil or gas production; it is also known as hydraulic fracturing. Fracturing artificially creates fractures in the formation, improving the underground flow environment for oil and gas, increasing oil and gas well production, and playing an important role in improving bottomhole flow conditions, mitigating inter-layer flow, and improving reservoir activation.

[0003] Currently, the primary method of fracturing is hydraulic fracturing. Hydraulic fracturing involves injecting fluid at high speed into the well using a surface high-pressure pump unit. The high pressure generated at the bottom of the well causes the oil and gas reservoir rock to fracture. To prevent the fractures from closing automatically after the pump unit stops operating and the pressure drops, sand with a density several times greater than the formation is mixed into the injected fluid after the formation fractures. This sand enters the fractures along with the fluid and remains permanently within them, keeping the fractures open and ensuring a long-term improved oil and gas flow environment. Hydraulic fracturing technology is now very mature, with significant oil and gas well production enhancement effects, and has long been the preferred and commonly used technology. Its production enhancement effect is particularly outstanding for oil and gas reservoirs with very small oil and gas flow channels, i.e., low permeability. Furthermore, ultra-low permeability and shale oil and gas reservoirs are the main targets for future development. Their development is related to the fracture system (natural fractures and hydraulically fracturing artificial fractures) present in these reservoirs.

[0004] Fracturing fluid is a crucial component of fracturing technology. Its primary function is to create fractures and deliver proppant along the opened fractures; therefore, the fluid's viscosity is paramount. Successful fracturing operations require the fluid to not only have high viscosity within the fractures but also the ability to rapidly break down the gel; to quickly flow back after the operation; to effectively control fluid loss; to have low friction during pumping; and to be economically viable. Flow-through agents are important additives in fracturing fluids, significantly reducing oil-water interfacial tension and flow resistance in the core, thus achieving highly efficient flow-through.

[0005] Currently, most flow-out aids used in fracturing fluids are fluorocarbon surfactants or combinations thereof with other surfactants. Surfactants possess ionic polar heads or lone pairs of electrons, making them easily adsorbed into the formation. During fracturing, a large amount is adsorbed in the near-wellbore formation, leading to a loss of effective concentration and preventing high concentrations from reaching the far fracture end. Furthermore, compound flow-out aids, formulated with several surfactants, undergo "chromatographic separation" during reservoir migration, meaning the multiple components cannot maintain a consistently uniform distribution. Therefore, they do not achieve the comprehensive performance demonstrated in laboratory tests.

[0006] Therefore, the technical problem that needs to be solved is how to overcome the technical problems of existing drainage aids, such as large-scale adsorption near the wellbore formation, low effective concentration, and "chromatographic separation" during the migration of conventional compound drainage aids, which cannot achieve the comprehensive performance of compound drainage aids in laboratory experimental tests, and provide a new type of drainage aid. Summary of the Invention

[0007] As mentioned above, existing fracturing aids suffer from drawbacks such as excessive adsorption near the wellbore and "chromatographic separation" during migration. This invention provides a hydrolyzable polymer and its preparation method, an in-fracture hydrolyzable polymer fracturing aid, and its application. The fracturing aid of this invention is a polymeric surfactant, not a formulation, and unlike traditional formulation fracturing aids, it does not experience "chromatographic separation" (i.e., multiple components cannot maintain a uniform distribution) during reservoir migration, thus failing to achieve the comprehensive performance demonstrated in laboratory experiments. The hydrolyzable polymer and the in-fracture hydrolyzable polymer drainage aid of the present invention solve the technical problem that conventional formulation drainage aids are prone to "chromatographic separation" and their comprehensive performance in practical applications is far from what is achieved in experimental testing. It also solves the technical problem that conventional drainage aids are prematurely adsorbed during migration, resulting in a large amount of drainage aid loss. Moreover, the hydrolyzable polymer and the in-fracture hydrolyzable polymer drainage aid of the present invention have high surface activity and low interfacial tension after hydrolysis, which can meet the needs of fracturing drainage in ultra-low permeability oil and gas reservoirs and shale oil and gas, and have extremely high application value.

[0008] Specifically, taking the in-fracture hydrolyzable polymer drainage aid for fracturing as an example, the in-fracture hydrolyzable polymer drainage aid of the present invention is in a liquid state, which is convenient for pumping. After contact with water, since the solvent dissolves in water, the drainage aid precipitates in solid form in the fracturing fluid and enters the formation with the fracturing fluid, migrating to the far end with the fracture extension. Since the hydrolyzable functional groups in the polymer molecular structure of the drainage aid require a certain amount of time to hydrolyze, the drainage aid is in solid form during migration, avoiding premature adsorption near the wellbore. When it reaches the far end of the fracture, it will dissolve rapidly (within tens of minutes) during the well stagnation process (a few days or weeks) and play its role. Moreover, since this drainage aid is a polymer surfactant and not a formulation, it will not undergo "chromatographic separation" during reservoir migration, unlike traditional formulation drainage aids, where multiple components cannot maintain a uniform distribution and cannot achieve the comprehensive performance achieved in laboratory experimental tests. The polymer surfactant of this invention does not have "chromatographic separation" of functional groups, can work synergistically, has high surface activity and low interfacial tension, and can meet the needs of fracturing and drainage in ultra-low permeability oil and gas reservoirs and shale oil and gas.

[0009] The first aspect of the present invention is to provide a hydrolyzable polymer containing four structural units respectively copolymerized by olefin double bonds: structural unit one, structural unit two, structural unit four and optional structural unit three; wherein structural unit one 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 olefin double bonds;

[0012] Structural unit four is provided by a fluorinated monomer with an olefin double bond;

[0013] The molar ratio of structural unit two to structural unit one and structural unit three is 1:(3-7):(0-2.5).

[0014] Based on a total mass of 100 wt% of all structural units of the hydrolyzable polymer, 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 ratio of the second structural unit to the first and third structural units is 1:(3-7):(0-2.5). In a preferred embodiment of the present invention, the molar ratio of the second structural unit to the first and third structural units is 1:(4-6):(0-2).

[0016] According to the present invention, the hydrolyzable polymer contains four structural units respectively copolymerized by olefin double bonds: structural unit one, structural unit two, structural unit four and optional structural unit three, that is, structural unit three may not be contained, 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 being 100 wt%, the content of structural unit four in the hydrolyzable polymer is not less than 0.05 wt%, preferably 0.05 wt%-1 wt%. In a more preferred embodiment of the present invention, 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 0.1 wt%-0.5 wt%.

[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, stilbene, and methylstyrene, preferably styrene.

[0019] According to the present invention, amine and / or ammonium monomers having olefin double bonds can be selected from a wide range. In a preferred embodiment of the present invention, the amine and / or ammonium monomers having olefin double bonds are selected from amine and / or ammonium monomers having 8-20 carbon atoms; preferably selected from at least one of tetraallyl ammonium chloride, dimethyldiallyl ammonium chloride, dodecyl dimethyl allyl ammonium chloride, tetradecyl dimethyl allyl ammonium chloride, hexadecyl dimethyl allyl ammonium chloride and octadecyl dimethyl allyl ammonium chloride.

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

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

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

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

[0024] The second solvent and the initiator are mixed at a temperature not exceeding 30°C to obtain solution two; the third solvent is mixed with the styrene monomer to obtain solution three.

[0025] When the temperature of solution three is 75-85℃, solutions one and two are added dropwise to solution three. During the dropwise addition process, the temperature of the reaction mixture is controlled not to exceed 90℃, preferably when the temperature of the reaction mixture is below 85℃, until the dropwise addition is completed. The preferred dropwise addition time is 90-180 min. After the dropwise addition is completed, the reaction mixture is kept at 75-85℃ and the reaction continues for 0.5-1.5 h.

[0026] Preferably, the mixture is mixed at a speed of 80-200 r / min during the dropping and reaction processes.

[0027] As previously stated, according to the present invention, the molar ratio of the maleic anhydride monomer to the styrene monomer, the amine and / or ammonium monomer having an olefin double bond 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 and / or ammonium monomer having an olefin double bond is 1:(4-6):(0-2).

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

[0029] According to the present invention, the ratio of the solvent to the total mass of all monomer raw materials can be selected within a wide range. In a preferred embodiment of the present invention, the ratio of the solvent to the total mass of 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 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, stilbene, and methylstyrene, preferably styrene.

[0032] According to the present invention, amine and / or ammonium monomers having olefin double bonds can be selected from a wide range. In a preferred embodiment of the present invention, the amine and / or ammonium monomers having olefin double bonds are selected from amine and / or ammonium monomers having 8-20 carbon atoms, preferably selected from at least one of tetraallyl ammonium chloride, dimethyldiallyl ammonium chloride, dodecyl dimethyl allyl ammonium chloride, tetradecyl dimethyl allyl ammonium chloride, hexadecyl dimethyl allyl ammonium chloride, and octadecyl dimethyl allyl ammonium chloride.

[0033] According to the present invention, fluorinated monomers having olefin double bonds can be selected from a wide range. In a preferred embodiment of the present invention, the fluorinated monomers having olefin double bonds are 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] A third aspect of the present invention is to provide a hydrolyzable polymer discharge aid, said hydrolyzable polymer discharge aid comprising the hydrolyzable polymer described in the first aspect, or the hydrolyzable polymer prepared by the preparation method described in the second aspect, and optionally a solvent; preferably,

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

[0038] The hydrolytic polymer discharge aid is a reaction mixture obtained as follows: comprising copolymerizing monomeric raw materials, including the styrene monomers, the maleic anhydride monomers, the amine and / or ammonium monomers having olefin double bonds, and the fluorinated monomers having olefin double bonds, in a solvent under a protective atmosphere and in the presence of an initiator.

[0039] A 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 can be directly added to the fracturing fluid, or a hydrolyzable polymer drainage aid (i.e., containing a hydrolyzable polymer and a solvent, and being a liquid) can be added, both methods achieving the present invention. The preferred method is to directly add the hydrolyzable polymer drainage aid.

[0042] A fifth aspect of the present invention is to provide a polymeric surfactant comprising four structural units copolymerized from olefin double bonds: structural unit one, structural unit two, structural unit four, and optionally structural unit three;

[0043] Among them, structural unit one is provided by styrene monomers;

[0044] Structural Unit Two is

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

[0046] Structural unit four is provided by a fluorinated monomer with an olefin double bond;

[0047] The molar ratio of the second structural unit to the first and third structural units is 1:(3-7):(0-2.5), preferably 1:(4-6):(0-2);

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

[0049] Preferably, the polymeric surfactant is derived from the 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 ease of explanation, as an example, the polymer drainage aid of the present invention can be prepared and applied in the following manner:

[0051] (1) Synthesis method

[0052] The reactants used DMF as a 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 reactor is employed. Pre-mixing: ① Dissolve a portion of the solvent DMF, hydrophilic monomer maleic anhydride, amine / ammonium hydrophilic monomers, and one or more fluorine-containing monomers at room temperature (≤30℃). ② Dissolve a portion of the solvent DMF, initiator azobisisobutyronitrile, 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 to the reactor, then heat to 75-85℃ and stir at 80-200 r / min.

[0056] Using a diaphragm pump, slowly add solutions ① and ② dropwise into the reactor, controlling the dropping time to 90-180 minutes. During this period, the temperature inside the reactor must not exceed 90℃. If it exceeds 90℃, stop dropping and wait until the temperature drops below 85℃ before continuing to drop until all solutions have been added. Maintain the temperature at 75-85℃ and continue the reaction for 0.5-1.5 hours.

[0057] After the final reaction, the reactants in the reactor transformed into a pale yellow, homogeneous, stable, slightly viscous liquid.

[0058] (2) Mechanism of hydrolysis within the suture

[0059] The styrene polymerization moiety in the polymer provides hydrophobicity, and the hydrolysis of maleic anhydride provides two carboxyl groups. Figure 1 Cationic monomers provide a cationic head and some hydrophobicity, while a small amount of fluorinated monomers can further reduce interfacial tension.

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

[0061] Fracturing operations require a large displacement (10-20 m³ / min) 3 The precipitated solid polymer rapidly (within minutes) enters the formation fracture system along with the fracturing fluid and migrates with the fractures, preventing premature adsorption near the wellbore and thus facilitating access to the oil layer. Upon reaching the distal fracture, it dissolves rapidly (within tens of minutes) during the well-shutting process (which typically lasts several days or weeks after fracturing). (After fracturing, a well is shutted depending on the specific circumstances, usually for several days or even longer, during which time the wellhead is sealed. After the designed shutting time is reached, the well is opened for flowback (removing some of the fracturing fluid while gradually encountering oil and gas). Because the polymer flowback aid has a short dissolution time, most of it dissolves during fracturing, and the small amount that remains undissolved also dissolves completely during this process), thus yielding a hydrolyzed polymer surfactant that then functions.

[0062] (3) Surface and interfacial tension test

[0063] The interfacial tension test shall be conducted in accordance with the standards SY / T 5370 and Q / SH 3580 0160.

[0064] The synthesized polymer drainage aid is a pale yellow liquid. Performance tests of its hydrolysate show that a 0.1% aqueous solution (based on the mass of the polymer in the drainage aid) has an interfacial tension of less than 1 mN / m and a surface tension of less than 23 mN / m. (Note: Currently, a 0.1% aqueous solution of the drainage aid is generally required to have a surface tension ≤28 mN / m; however, for wells with high drainage requirements, a surface tension ≤23 mN / m is often required.)

[0065] In summary, this invention synthesizes a fracture hydrolyzable polymeric drainage aid for fracturing using hydrophobic monomers such as styrene and hydrolyzable hydrophilic monomers such as maleic anhydride, and DMF as a solvent. The product itself is a liquid, facilitating pumping. When pumped into fracturing fluid, the anhydride portion of the polymer is not yet hydrolyzed, and the entire molecule exhibits strong hydrophobicity. Under stirring, as the solvent dissolves in water, the product precipitates as loose solid particles and enters the wellbore with the fracturing fluid, migrating to the distal end of the fracture network and gradually dissolving. The hydrolysate of the polymer of this invention has low interfacial tension, meeting the fracturing drainage requirements of ultra-low permeability oil and gas reservoirs and shale oil and gas fields.

[0066] A sixth aspect of the present invention is to provide the 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 aid described in the third aspect, or the fracturing fluid composition described in the fourth aspect, or the polymeric surfactant described in the fifth aspect, in the petroleum field; preferably,

[0067] Application in fracturing and extraction in oil extraction.

[0068] Preferably, the application includes:

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

[0070] The hydrolyzable polymer is transported along 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 met, the hydrolyzable polymer hydrolyzes and dissolves in water to obtain a polymeric surfactant.

[0072] The polymeric surfactant comes into contact with the reservoir.

[0073] According to the present invention, the hydrolysis conditions of the hydrolyzable polymer are not particularly limited. The polymeric drainage aid begins to dissolve upon contact with water, and the dissolution time varies depending on the molecular structure and temperature. It has been verified that, in the presence of water and at any temperature, the polymeric drainage aid of the present invention will be completely hydrolyzed within 6 hours, yielding a polymeric surfactant. For example, at a temperature of 90°C, the hydrolysis time is approximately 5-20 minutes.

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

[0075] The drainage aid of this invention is a polymeric surfactant, not a formulation. Unlike traditional formulation drainage aids, it does not undergo "chromatographic separation" during reservoir migration (i.e., multiple components cannot maintain a uniform distribution), thus failing to achieve the comprehensive performance tested in laboratory experiments. This invention's hydrolyzed polymer, specifically the in-fracture hydrolyzed polymer drainage aid for fracturing, solves the technical problem of conventional formulation drainage aids being prone to "chromatographic separation," resulting in a significant discrepancy between practical application and experimental performance. It also addresses the issue of premature adsorption during migration, leading to substantial drainage aid losses. Furthermore, the invented hydrolyzed polymer, after hydrolysis, exhibits high surface activity and low interfacial tension, meeting the drainage needs of ultra-low permeability oil and gas reservoirs and shale oil and gas reservoirs, demonstrating extremely high application value. Attached Figure Description

[0076] Figure 1 Schematic diagram of partial hydrolysis of acid anhydrides in polymers. Detailed Implementation

[0077] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0078] (1) Raw materials

[0079] ① Monomer:

[0080] Styrene has a molecular weight of 104.14 and a boiling point of 145.2℃.

[0081] Maleic anhydride has a molecular weight of 98.06.

[0082] Tetraallylammonium chloride has a molecular weight of 135.64.

[0083] Dimethyl diallyl ammonium chloride has a molecular weight of 161.67.

[0084] The molecular weight of dodecyl dimethyl allyl ammonium chloride is 289.93.

[0085] Tetradecyl dimethyl allyl ammonium chloride has a molecular weight of 317.69.

[0086] The molecular weight of hexadecyl dimethyl allyl ammonium chloride is 346.04.

[0087] Octadecyldimethylallylammonium chloride has a molecular weight of 374.09.

[0088] Perfluorohexylethylene has a molecular weight of 346.09.

[0089] Perfluorooctylethylene has a molecular weight of 446.10.

[0090] Perfluorododecylethylene has a molecular weight of 646.13.

[0091] 1,8-Divinylperfluorooctane has a molecular weight of 454.15.

[0092] Note: Considering the high price of fluorinated monomers and the need to achieve a certain low surface tension in practical applications, it is preferable to add 0.1%-0.5% of the total monomer mass.

[0093] ② Solvent: N,N-Dimethylformamide (DMF), molecular weight 73.10, boiling point 153℃

[0094] ③ Initiator: Azobisisobutyronitrile (AIB) with a molecular weight of 164.21

[0095] Unless otherwise specified, all raw materials used in this invention are commercially available products.

[0096] Comparative Example 1

[0097] (1) Raw materials

[0098] 416g of styrene

[0099] maleic anhydride 98g

[0100] (2) Process

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

[0102] Pre-mixing outside the reactor was adopted. Pre-mixing: ① Maleic anhydride was mixed with an equal mass of 98g of solvent DMF and dissolved at room temperature (≤30℃) to obtain solution ①.

[0103] ②The initiator azobisisobutyronitrile is 0.3% of the total mass of the monomers. An additional 50g of solvent DMF is added to dissolve it at room temperature (≤30℃) to obtain solution ②.

[0104] First, add 416g each of DMF and styrene to the reactor, then heat to 75-85℃ and stir at 100r / min.

[0105] Using a diaphragm pump, slowly add solutions ① and ② dropwise into the reactor, controlling the dropwise addition time to 120 minutes. During this period, the temperature inside the reactor must not exceed 90℃. If it exceeds 90℃, stop the dropwise addition and wait for the temperature to drop below 85℃ before resuming the dropwise addition until all solutions have been added. Maintain the temperature at 75-85℃ and continue the reaction for 1 hour.

[0106] After the final reaction, the reactants in the reactor are transformed into a pale yellow, homogeneous, stable, slightly viscous liquid, which serves as a hydrolytic polymer discharge aid.

[0107] Example 1

[0108] (1) Raw materials

[0109] 520g of styrene

[0110] maleic anhydride 98g

[0111] 271g of tetraallylammonium chloride

[0112] 0.45g of perfluorododecylethylene

[0113] 0.45 g of 1,8-bisvinylperfluorooctane

[0114] (2) Process

[0115] Pre-mixing outside the reactor was adopted. Pre-mixing: ① 1200g of solvent DMF, hydrophilic monomer maleic anhydride, amine / ammonium hydrophilic monomer and fluorine-containing monomer were dissolved at room temperature (≤30℃) to obtain solution ①.

[0116] ② Dissolve 100g of solvent DMF and 2.5g of initiator azobisisobutyronitrile at room temperature (≤30℃) to obtain solution ②.

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

[0118] Using a diaphragm pump, slowly add solutions ① and ② dropwise into the reactor, controlling the dropwise addition time to 160 minutes. During this period, the temperature inside the reactor must not exceed 90℃. If it exceeds 90℃, stop the dropwise addition and wait for the temperature to drop below 85℃ before resuming the dropwise addition until all the solutions have been added. Maintain the temperature at 75-85℃ and continue the reaction for 1.5 hours.

[0119] After the final reaction, the reactants in the reactor are transformed into a pale yellow, homogeneous, stable, slightly viscous liquid, which is the hydrolyzed polymer discharge aid.

[0120] Example 2

[0121] (1) Raw materials

[0122] 625g of styrene

[0123] maleic anhydride 98g

[0124] 324g of dimethyldiallylammonium chloride

[0125] 1,8-Divinylperfluorooctane 5.3g

[0126] (2) Process

[0127] Pre-mixing outside the reactor was adopted. Pre-mixing: ① 4000g of solvent DMF, hydrophilic monomer maleic anhydride, amine / ammonium hydrophilic monomer and fluorine-containing monomer were dissolved at room temperature (≤30℃) to obtain solution ①.

[0128] ② Dissolve 200g of solvent DMF and 1.2g of initiator azobisisobutyronitrile at room temperature (≤30℃) to obtain solution ②.

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

[0130] Using a diaphragm pump, slowly add solutions ① and ② dropwise into the reactor, controlling the dropwise addition time to 100 minutes. During this period, the temperature inside the reactor must not exceed 90℃. If it exceeds 90℃, stop the dropwise addition and wait for the temperature to drop below 85℃ before resuming the dropwise addition until all solutions have been added. Maintain the temperature at 75-85℃ and continue the reaction for 1 hour.

[0131] After the final reaction, the reactants in the reactor are transformed into a pale yellow, homogeneous, stable, slightly viscous liquid, which is the hydrolyzed polymer discharge aid.

[0132] Example 3

[0133] (1) Raw materials

[0134] 416g of styrene

[0135] maleic anhydride 98g

[0136] 579g of dodecyl dimethyl allyl ammonium chloride

[0137] Perfluorododecylethylene 3.3g

[0138] (2) Process

[0139] Pre-mixing outside the reactor was adopted. Pre-mixing: ① 2400g of solvent DMF, hydrophilic monomer maleic anhydride, amine / ammonium hydrophilic monomer and fluorine-containing monomer were dissolved at room temperature (≤30℃) to obtain solution ①.

[0140] ② Dissolve 150g of DMF solvent and 5g of azobisisobutyronitrile initiator at room temperature (≤30℃) to obtain solution ②.

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

[0142] Using a diaphragm pump, slowly add solutions ① and ② dropwise into the reactor, controlling the dropwise addition time to 90 minutes. During this period, the temperature inside the reactor must not exceed 90℃. If it exceeds 90℃, stop the dropwise addition and wait for the temperature to drop below 85℃ before resuming the dropwise addition until all solutions have been added. Maintain the temperature at 75-85℃ and continue the reaction for 0.5 hours.

[0143] After the final reaction, the reactants in the reactor are transformed into a pale yellow, homogeneous, stable, slightly viscous liquid, which is the hydrolyzed polymer discharge aid.

[0144] Example 4

[0145] (1) Raw materials

[0146] 416g of styrene

[0147] maleic anhydride 98g

[0148] Tetradecyl dimethyl allyl ammonium chloride 635g

[0149] 1,8-Divinylperfluorooctane 5.8g

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

[0151] The process is the same as in Example 1, and a hydrolyzed polymer drainage aid is obtained.

[0152] Example 5

[0153] (1) Raw materials

[0154] 416g of styrene

[0155] maleic anhydride 98g

[0156] 692g of hexadecyl dimethyl allyl ammonium chloride

[0157] 1.2g of perfluorooctylethylene

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

[0159] The process is the same as in Example 1, and a hydrolyzed polymer drainage aid is obtained.

[0160] Example 6

[0161] (1) Raw materials

[0162] 416g of styrene

[0163] maleic anhydride 98g

[0164] 748g of octadecyl dimethyl allyl ammonium chloride

[0165] 12.7g of perfluorohexylethylene

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

[0167] The process is the same as in Example 1, and a hydrolyzed polymer drainage aid is obtained.

[0168] Example 7

[0169] 416g of styrene

[0170] maleic anhydride 98g

[0171] 12.7g of perfluorohexylethylene

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

[0173] The process is the same as in Example 1, and a hydrolyzed polymer drainage aid is obtained.

[0174] Comparative Example 2

[0175] (1) Raw materials

[0176] 416g of styrene

[0177] maleic anhydride 98g

[0178] 748g of octadecyl dimethyl allyl ammonium chloride

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

[0180] The process is the same as in Example 1, and a hydrolyzed polymer drainage aid is obtained.

[0181] Detection example

[0182] The following experiments were conducted using the polymer discharge aids from the examples and comparative examples:

[0183] Based on the mass of the polymer in the polymer drainage aid, a 0.1 wt% mixture of polymer drainage aid was prepared with deionized water, placed at 90°C, and hydrolyzed for 2 hours. The surface tension of the hydrolysate was tested, as was the interfacial tension of the hydrolysate.

[0184] During the experiment, it was found that the polymer drainage aid of the present invention is in a liquid state. Upon contact with water, the solvent dissolves in the water, and the drainage aid precipitates in solid form in the fracturing fluid. Therefore, the finished drainage aid of the present invention is in a liquid state, which facilitates pumping; upon contact with water, the solvent dissolves in the water, and the drainage aid precipitates in solid form in the fracturing fluid. Thus, during transport, the drainage aid remains in solid form, preventing premature adsorption near the wellbore.

[0185] Experiments revealed that the polymer-based drainage aid of this invention, when hydrolyzed at 90°C for 2 hours, completely dissolved in its solid form, transforming into a polymeric surfactant. The surface tension and interfacial tension were measured according to standards SY / T 5370 and Q / SH 3580 0160, and the specific results are shown in Table 1.

[0186] As verified above, the polymer drainage aid in the embodiments of this invention, when hydrolyzed at 90°C for 2 hours, yields a solution containing a polymeric surfactant. Further verification revealed that in an aqueous environment, the polymeric drainage aid of this invention completely hydrolyzes within 6 hours at temperatures above 25°C. Since the polymeric surfactant in this invention does not undergo chromatographic separation, the experimental test results of the surfactant are equivalent to those of practical applications. Experiments show that the hydrolysate of 0.1 wt% polymer exhibits low interfacial tension, with most surface tensions less than 20 mN / m and interfacial tensions less than 0.1 mN / m. The polymeric surfactant of this invention possesses low interfacial tension, meeting the requirements for fracturing and drainage in ultra-low permeability oil and gas reservoirs and shale oil and gas fields, and thus has extremely high application value.

[0187] Table 1. Surface and interfacial tension of hydrolysate of 0.1% polymer

[0188]

[0189] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on 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 terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

[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 commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0191] When this specification uses the prefixes "known to those skilled in the art," "prior art," or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those conventionally used in the art at the time the invention was proposed, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0192] The endpoints and any values ​​of the ranges disclosed in this invention document are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In the following, various technical solutions can, in principle, be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0193] In the context of this specification, except where expressly stated otherwise, any matters or issues not mentioned shall apply directly to those known in the art without any modification.

[0194] Furthermore, any implementation described herein can be freely combined with one or more other implementations described herein, and the resulting technical solutions or technical ideas shall be regarded as part of the original disclosure or original record of the present invention, and should not be regarded as new content not disclosed or anticipated herein, unless those skilled in the art consider the combination to be obviously unreasonable.

Claims

1. A hydrolyzable polymer containing four structural units copolymerized from olefin double bonds: structural unit one, structural unit two, structural unit four, and optional structural unit three; 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 olefin double bonds; Structural unit four is provided by a fluorinated monomer with an olefin double bond; The molar ratio of structural unit two to structural unit one and structural unit three is 1:(3-7):(0-2.5). Based on a total mass of 100wt% of all structural units of the hydrolyzable polymer, the content of structural unit four in the hydrolyzable polymer is 0.05wt%-1wt%.

2. The hydrolyzable polymer according to claim 1, characterized in that: The molar ratio of structural unit two to structural unit one and structural unit three is 1:(4-6):(0-2); and / or, Based on a total mass of 100 wt% of all structural units of the hydrolyzable polymer, the content of structural unit four in the hydrolyzable polymer is 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, stilbene, and methylstyrene; and / or, The amine and / or ammonium monomers having an olefin double bond are selected from amine and / or ammonium monomers having an olefin double bond having 8-20 carbon atoms; and / or, Fluorinated monomers with olefin double bonds are selected from fluorinated monomers with olefin double bonds having 6-18 carbon atoms.

4. The hydrolyzable polymer according to claim 1, characterized in that: The styrene monomer is styrene; and / or, The amine and / or ammonium monomers having olefin double bonds are selected from at least one of tetraallyl ammonium chloride, dimethyldiallyl ammonium chloride, dodecyl dimethylallyl ammonium chloride, tetradecyl dimethylallyl ammonium chloride, hexadecyl dimethylallyl ammonium chloride, and octadecyl dimethylallyl ammonium chloride; and / or, Fluorinated monomers having olefin double bonds are selected from at least one of perfluorohexylethylene, perfluorooctylethylene, perfluorododecylethylene, and 1,8-divinylperfluorooctane.

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

6. The preparation method according to claim 5, characterized in that... The preparation method includes: The solvent is used in at least three parts. The first part of the solvent is mixed with the maleic anhydride monomer, the amine and / or ammonium monomer with olefin double bonds, and the fluorine-containing monomer with olefin double bonds at a temperature not higher than 30°C to obtain solution one. The second solvent and the initiator were mixed under conditions where the initiator temperature did not exceed 30°C to obtain solution two; The third solvent is mixed with the styrene monomer to obtain solution three; When the temperature of solution three is 75-85℃, solutions one and two are added dropwise to solution three, and the temperature of the reaction mixture is controlled not to exceed 90℃ during the dropwise addition process; after the dropwise addition is completed, the reaction mixture is kept at 75-85℃ for 0.5-1.5h.

7. The preparation method according to claim 6, characterized in that... The preparation method includes: Add solutions one and two dropwise to solution three: add the solutions dropwise when the temperature of the reaction mixture is below 85℃, until the addition is complete, and the addition time is 90-180 minutes. During the dropwise addition and reaction process, the mixture is mixed at a speed of 80-200 r / min.

8. The preparation method according to any one of claims 5-7, characterized in that: The molar ratio of the maleic anhydride monomer to the styrene monomer, the amine and / or ammonium monomer having olefin double bonds is 1:(3-7):(0-2.5). Based on a total mass of 100 wt% for all monomer raw materials, the content of the fluorinated monomers with olefin double bonds is 0.1 wt%-0.5 wt%; and / or, The ratio of the solvent to the total mass of all monomer raw materials is (1-20):1; and / or, The amount of the initiator is 0.1%-0.5% of the total mass of all monomer raw materials.

9. The preparation method according to any one of claims 5-7, characterized in that: The molar ratio of the maleic anhydride monomer to the styrene monomer, the amine and / or ammonium monomer with olefin double bonds is 1:(4-6):(0-2). The ratio of the solvent to the total mass of all monomer raw materials is (1.5-4):

1.

10. The preparation method according to any one of claims 5-7, characterized in that: The styrene monomer is selected from at least one of styrene, stilbene, and methylstyrene; and / or, The amine and / or ammonium monomers having an olefin double bond are selected from amine and / or ammonium monomers having an olefin double bond having 8-20 carbon atoms; and / or, Fluorinated monomers having olefin double bonds are selected from at least one of perfluorohexylethylene, perfluorooctylethylene, perfluorododecylethylene, and 1,8-divinylperfluorooctane; and / or, The solvent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, and acetone; and / or, The initiator is at least one of azobisisobutyronitrile, benzoyl peroxide, and di-tert-butyl peroxide.

11. The preparation method according to any one of claims 5-7, characterized in that: The styrene monomer is styrene; and / or, The amine and / or ammonium monomers having olefin double bonds are selected from at least one of tetraallyl ammonium chloride, dimethyldiallyl ammonium chloride, dodecyl dimethylallyl ammonium chloride, tetradecyl dimethylallyl ammonium chloride, hexadecyl dimethylallyl ammonium chloride, and octadecyl dimethylallyl ammonium chloride; and / or, The solvent is selected from N,N-dimethylformamide; and / or, The initiator is azobisisobutyronitrile.

12. A hydrolyzable polymer discharge aid, said hydrolyzable polymer discharge aid comprising the hydrolyzable polymer of any one of claims 1-4, or the hydrolyzable polymer prepared by the preparation method of any one of claims 5-11, and an optional solvent.

13. The hydrolyzable polymer drainage aid according to claim 12, characterized in that: The hydrolyzed polymer drainage aid contains a solvent and is in liquid form.

14. The hydrolyzable polymer drainage aid according to claim 13, characterized in that: The hydrolytic polymer discharge aid is a reaction mixture obtained as follows: comprising copolymerizing monomeric raw materials, including the styrene monomers, the maleic anhydride monomers, the amine and / or ammonium monomers having olefin double bonds, and the fluorinated monomers having olefin double bonds, in a solvent under a protective atmosphere and in the presence of an initiator.

15. A fracturing fluid composition comprising fracturing fluid and a hydrolyzable polymer according to any one of claims 1-4, or a hydrolyzable polymer prepared by any one of claims 5-11, or a hydrolyzable polymer drainage aid according to any one of claims 12-14, wherein the fracturing fluid contains water.

16. The fracturing fluid composition according to claim 15, characterized in that: The mass ratio of the hydrolyzable polymer to water in the fracturing fluid composition is (0.05-1):

100.

17. A polymeric surfactant comprising four structural units copolymerized from olefin double bonds: structural unit one, structural unit two, structural unit four, and optionally structural unit three; in, Structural unit one is provided by styrene monomers; Structural Unit Two is ; Structural unit three is provided by amine and / or ammonium monomers having olefin double bonds; Structural unit four is provided by a fluorinated monomer with an olefin double bond; The molar ratio of structural unit two to structural unit one and structural unit three is 1:(3-7):(0-2.5). Based on a total mass of 100wt% of all structural units of the polymeric surfactant, the content of structural unit four in the polymeric surfactant is 0.05wt%-1wt%.

18. The polymeric surfactant according to claim 17, characterized in that: The molar ratio of structural unit 2 to structural unit 1 and structural unit 3 is 1:(4-6):(0-2).

19. The polymeric surfactant according to claim 17, characterized in that: Based on a total mass of 100 wt% of all structural units of the polymeric surfactant, the content of structural unit four in the polymeric surfactant is 0.1 wt%-0.5 wt%.

20. The polymeric surfactant according to any one of claims 17-19, characterized in that: The polymeric surfactant is derived from the hydrolysis of a hydrolyzable polymer; the hydrolyzable polymer is the hydrolyzable polymer of any one of claims 1-4, or the hydrolyzable polymer prepared by the preparation method of any one of claims 5-11.

21. The application of a hydrolyzable polymer according to any one of claims 1-4, or a hydrolyzable polymer prepared by any one of claims 5-11, or a hydrolyzable polymer drainage aid according to any one of claims 12-14, or a fracturing fluid composition according to claim 15 or 16, or a polymeric surfactant according to any one of claims 17-20, in the petroleum field.

22. The application according to claim 21, characterized in that: The application is in the field of fracturing and extraction in oil extraction.

23. The application according to claim 21 or 22, characterized in that... The applications include: The hydrolyzable polymer or the hydrolyzable polymer drainage aid is mixed with fracturing fluid to obtain a fracturing fluid composition containing hydrolyzable polymer, wherein the hydrolyzable polymer exists in the form of solid particles. The hydrolyzable polymer is transported along 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 met, the hydrolyzable polymer hydrolyzes and dissolves in water to obtain a polymeric surfactant. The polymeric surfactant comes into contact with the reservoir.

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