A polymer material, its preparation method and use

Abstract

The application discloses a polymer material and a preparation method and application thereof. The polymer material is a polymer with an anion group, a cation group and a hydrophobic group simultaneously existing on a molecular chain; the polymer is a straight-chain polymer, and the anion group, the cation group and the hydrophobic group are randomly distributed on a main chain of the polymer through a covalent bond. The polymer material prepared by the application introduces the anion group through 2-alkenecarboxamide-2-methylpropane sulfonic acid and an unsaturated carboxylic acid monomer, introduces the cation group and the hydrophobic group through an amphiphilic unsaturated cation monomer, realizes specific functions by using the three groups, and can achieve the purpose of intelligent leakage prevention and effectively play a plugging role.

Description

Technical Field

[0001] This invention relates to a polymer material, its preparation method, and its application. Background Technology

[0002] According to OPEC's "World Oil Outlook 2020," oil will continue to be the largest contributor to the energy mix, accounting for over 27% by 2045, followed by natural gas (25%). With increasing demand for oil and gas, global resource exploration is gradually shifting towards unconventional oil and gas resources. However, fracture-related leakage, porosity-related leakage, and high-permeability leakage have become key challenges restricting the efficient exploitation of unconventional oil and gas. Currently, research on leakage prevention and plugging in easily leaky formations, particularly in drilling fluids, has made significant progress. However, during cementing, to ensure displacement efficiency, the design density of cement slurry is often higher than that of drilling fluid. Therefore, cement slurry places higher demands on formation pressure, leading to continued cementing leakage risks in fractured and high-permeability formations even after drilling fluid-based leakage prevention and plugging. Furthermore, friction and collision between the casing and wellbore during casing running can cause damage and failure of the plugging layer structure, further widening fractures and increasing the risk of cementing leakage. Cementing loss can cause cement slurry to invade the formation, causing pollution. At the same time, severe loss can lead to insufficient return, affecting the quality of cementing.

[0003] Currently, there are three main methods for reducing cementing leakage: one is to reduce the density of the cementing fluid column, thereby reducing the column pressure; the second is to increase the thixotropic properties of the cement slurry; and the third is to add leakage prevention and plugging materials to the cementing fluid. Because cementing fluid needs to stabilize the formation and displace drilling fluid, its column density range is often limited. To ensure safe operation, the rheological properties of the slurry also need to be controlled within a reasonable range. Therefore, the first two methods are not suitable for preventing leakage in complex deep wells, and the third method is currently the more commonly used and universally applicable approach to solving cementing leakage. Cementing leakage prevention and plugging materials are typically combinations of polymers, gels, fiber materials, and solid particulate materials. Summary of the Invention

[0004] In order to increase the selectivity of raw materials for cementing and plugging materials, this invention provides a polymer material that can overcome the problems of poor adaptability to different types of leakage in existing technologies, as well as the complex composition of current adaptive cementing and plugging materials, so as to realize industrial production and large-scale application.

[0005] As one aspect of the present invention, a polymer material is provided, wherein the polymer material refers to a polymer in which anionic groups, cationic groups and hydrophobic groups are present simultaneously on the molecular chain; the polymer is a linear polymer, and the anionic groups, the cationic groups and the hydrophobic groups are randomly distributed on the main chain of the polymer through covalent bonds.

[0006] In a specific embodiment, the polymer material, by weight, comprises the following components: 15-22 parts of 2-enamido-2-methylpropanesulfonic acid, 0.8-1.8 parts of amphiphilic unsaturated cationic monomer, and 2.5-4 parts of unsaturated carboxylic acid monomer.

[0007] Further, the polymer material, by weight, comprises the following components: 15-22 parts of 2-enamido-2-methylpropanesulfonic acid, 0.8-1.8 parts of amphiphilic unsaturated cationic monomer, 2.5-4 parts of unsaturated carboxylic acid monomer, and 10-20 parts of unsaturated amide monomer.

[0008] In a specific embodiment, the amphiphilic unsaturated cationic monomer is as shown in formula (Ⅰ):

[0009]

[0010] In the formula, R is H or a C1 to C4 alkyl group, and n is 11, 13, 15, 17 or 19.

[0011] In a specific embodiment, the unsaturated carboxylic acid monomer is selected from maleic acid, itaconic acid, or acrylic acid.

[0012] In a specific embodiment, the unsaturated amide monomer is selected from one of diacetone acrylamide, N,N-dimethylacrylamide, or N,N-diethylacrylamide.

[0013] In a specific embodiment, the polymer material further includes an initiator.

[0014] Furthermore, the initiator accounts for 0.15 to 0.5% of the total mass of the four substances: 2-enamido-2-methylpropanesulfonic acid, the amphiphilic unsaturated cationic monomer, the unsaturated carboxylic acid monomer, and the unsaturated amide monomer.

[0015] In a specific embodiment, the initiator adopts an oxidant-reducant initiation system.

[0016] Furthermore, the oxidant is selected from ammonium persulfate and / or potassium persulfate; the reducing agent is selected from sodium bisulfite and / or sodium hydroxide.

[0017] Specifically, the molar ratio of the oxidant to the reducing agent is 1:(0.5~1).

[0018] As another aspect of the present invention, a method for preparing the above-mentioned polymer material is provided, wherein the method uses 2-enamido-2-methylpropanesulfonic acid, an anionic group introduced by an unsaturated carboxylic acid monomer, and a cationic group and a hydrophobic group introduced by an amphiphilic unsaturated cationic monomer simultaneously when preparing the polymer material.

[0019] In a specific embodiment, the method includes the following steps:

[0020] Preparation of S1 and mixture M1

[0021] Dissolve the amphiphilic unsaturated cationic monomer in water to prepare mixture M1;

[0022] Preparation of S2 and mixture M2

[0023] 2-enamido-2-methylpropanesulfonic acid, unsaturated amide monomer and unsaturated carboxylic acid monomer were added to water in sequence, stirred to dissolve, and the pH of the solution was adjusted to obtain mixture M2.

[0024] S3, Preparation of polymer solution

[0025] Mixture M1 is prepared by heating S1 in a water bath. Mixture M2 prepared by S2 and an aqueous solution of initiator are added dropwise under stirring conditions. After the addition is completed, the temperature is raised to react and a polymer solution is obtained.

[0026] In a specific embodiment, in step S2, the pH value of the solution is adjusted to 6-7.

[0027] In a specific embodiment, in S3, the water bath temperature is set to 40-50°C.

[0028] In a specific embodiment, in S3, the stirring speed is set to 50-150 rpm.

[0029] In a specific embodiment, in S3, the dripping time is controlled to be 3 to 5 hours.

[0030] In a specific embodiment, in step S3, the temperature is raised to 50-55°C and the reaction proceeds for 4-6 hours.

[0031] As another aspect of the present invention, a leak-proof material is provided, said leak-proof material using the aforementioned polymer material.

[0032] As another aspect of the present invention, a pre-filling fluid for cementing leak prevention is provided, the pre-filling fluid for cementing leak prevention comprising the aforementioned leak prevention material.

[0033] As another aspect of the present invention, a cementing process is provided, wherein the above-mentioned cementing pre-flush fluid is used in the cementing process.

[0034] This invention introduces hydrophobic groups by using water-soluble amphiphilic unsaturated cationic monomers, which ensures that the amphiphilic unsaturated cationic monomers participate better in the polymerization reaction. Furthermore, since the amphiphilic unsaturated cationic monomers can dissolve in aqueous solutions, they can be more uniformly distributed on the polymer chain during synthesis, ensuring a more random distribution of hydrophobic groups in the polymer, which is beneficial for improving the hydrophobic association of the polymer. The specific monomer mixing sequence in this invention can improve the conversion rate of surfactant monomers, which have large molecular weights and large polymerization steric hindrance.

[0035] The special molecular structure designed in this invention introduces anionic groups through 2-enamido-2-methylpropanesulfonic acid and unsaturated carboxylic acid monomers, and introduces cationic and hydrophobic groups through amphiphilic unsaturated cationic monomers. By utilizing these three groups, specific functions are achieved, thereby realizing the purpose of intelligent leak prevention and playing a sealing role.

[0036] The preparation method of the present invention adopts the solution polymer method, which has a simple process, is green, safe and environmentally friendly, uses readily available raw materials and has low production costs, and can realize industrial production and large-scale application.

[0037] The present invention employs a specific order of ingredient addition, which is beneficial to increasing the conversion rate of macromolecular monomers and effectively controlling the polymer molecular structure and molecular weight.

[0038] The leak-proof material prepared by this invention has a simple composition, strong adaptability to different types of pre-fluids, and good compatibility with pre-fluids.

[0039] The intelligent polymer leak-proof material for cementing pre-filling fluid prepared by this invention has strong adaptability to cracks and voids, and can adapt to voids and cracks of various shapes and types, thus playing an intelligent leak-proof role.

[0040] The intelligent polymer anti-leakage material for cementing pre-fill fluid of the present invention has strong adaptability and can be used to deal with various leakage problems such as fracture leakage, porosity leakage, and high permeability leakage, and meet the cementing technology requirements of easily leaking formations such as fractured formations and high permeability formations.

[0041] The polymer material prepared by this invention undergoes intramolecular association at room temperature through the electrostatic interaction of ionic groups and the hydrophobic association of hydrophobic groups, reducing the polymer's hydrodynamic radius and minimizing its impact on the rheology of the pre-fluid. As the temperature increases, the molecular chains extend, gradually forming intermolecular associations. When the minimum association critical temperature is reached, a large number of hydrophobic associations occur between polymer molecules. With the increase of polymer concentration, the probability of contact between hydrophobic groups of polymer molecules increases, and a large number of hydrophobic associations also occur between different polymers. Based on the characteristic of self-assembled polymers undergoing hydrophobic association after reaching specific temperatures and concentrations, and by introducing ionic groups to adsorb solid particles during polymerization, a deformable polymer-solid particle composite structure is formed. Under pressure difference, this structure adaptively flows into cracks and pores of different types and openings. In the crack space, the polymer concentration further increases, the associated structure becomes larger and denser, and finally a structure of "rigid material bridging + flexible material filling" is formed, realizing a system for intelligent leak prevention in applicable types of formations.

[0042] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained in accordance with the structures particularly pointed out in the description, claims and drawings. Detailed Implementation

[0043] With increasing demands for efficiency and success rates in leak prevention and sealing, leak prevention and sealing materials are increasingly being given more performance requirements, such as adaptability to cracks, temperature sensitivity, and sufficient pressure-bearing sealing capacity. Therefore, the design of polymers and compound material systems is becoming increasingly complex. During their material research, the inventors discovered that:

[0044] CN 105062440 B discloses a leak-stopping and leak-proof material comprising fibers, polymer microspheres, polymer powder, and blast furnace slag. The polymer microspheres and fibers are intertwined, and the polymer powder binds the polymer microspheres, fibers, and blast furnace slag, ensuring the pressure-bearing capacity of the leak-stopping and leak-proof material. This method can meet the leak-stopping requirements of cementing wells in fractured, porous, and seeping formations, while also possessing high temperature resistance. However, the inventors believe that the synthesis method for preparing leak-proof materials using polymer microspheres is complex, the size of the microspheres is difficult to control, and the application cost is high.

[0045] CN 115029926 A discloses the composition and preparation method of a fiber-grafted expandable resin plugging material and its application in cementing and leak prevention. This fiber-grafted expandable resin plugging material is obtained by grafting and copolymerizing modified polypropylene fibers with acrylic acid, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and N,N-methylenebisacrylamide under certain conditions. It can deformably be extruded into the pores formed by the bridging material and effectively seals cracks of 1-5 mm at temperatures of 20-120℃. However, the inventors believe that during the preparation process, it is necessary to ensure the control of the water absorption and expansion rate of the expandable resin material to avoid problems such as premature expansion.

[0046] CN 114426818 A discloses a cement slurry system for well cementing and leak prevention based on temperature-sensitive memory polymer, comprising oil well cement, temperature-sensitive memory expansion balls, temperature-sensitive memory expansion mesh, rigid particles, a high-temperature suspension stabilizer, and water. The density of the cement slurry system is 1.20–1.50 g / cm³. 3 It is adjustable, and the pressure resistance of 0.5-6mm cracks is not less than 6MPa when applied at temperatures of 90-150℃. However, the inventors believe that the current manufacturing process of temperature-sensitive memory materials is complex and costly, and its intelligent response factor is mainly temperature, resulting in insufficient intelligent adaptability to different types of lost formations.

[0047] CN 110002798 A discloses a well cementing slurry for preventing leakage, comprising the following components: water, oil well cement, bridging particles, quartz sand, silica fume, and cement additives; the median particle size of the oil well cement is 10μm to 30μm; the particle size of the bridging particles is 1 / 2 to 2 / 3 of the average pore throat diameter or average fracture width of the target formation; the particle size of the quartz sand is 180μm to 425μm; and the particle size of the silica fume is 0.1μm to 0.3μm. This well cementing slurry forms a bridge through the reasonable gradation of particles of different sizes, thereby effectively sealing porous formations prone to leakage and formations with induced fractures caused by pressure differentials, and has high pressure resistance. However, the inventors believe that this system needs to consider the formation pore throat diameter or fracture width when selecting components, and its adaptability to different types of leakage is insufficient.

[0048] In summary, given that existing technologies do not meet the inventor's expectations, the inventor developed this invention through further research and development.

[0049] The present invention will be further described below with reference to specific embodiments. The scope of protection of the present invention is not limited to the following embodiments. The main sources of materials involved in the embodiments are shown in Table 1 below. Other materials not specified are all conventional commercially available products.

[0050] Table 1 Material Source Description

[0051]

[0052]

[0053] Through extensive experimental research, the inventors have made the following optimized selections of the raw materials and preparation methods of polymer materials, and provided Examples 1 to 9.

[0054] Example 1

[0055] The polymer material of this embodiment, by weight, comprises the following components: 20g of 2-enamido-2-methylpropanesulfonic acid, 15g of N,N-dimethylacrylamide, 3g of itaconic acid, 1.2g of an amphiphilic unsaturated cationic monomer (wherein, in the structure of the amphiphilic unsaturated cationic monomer, R is methyl and n is 13), 0.12g of ammonium persulfate (oxidation initiator), and 0.07g of sodium bisulfite (reduction initiator);

[0056] The polymer material in this embodiment is prepared through the following steps:

[0057] Preparation of S1 and mixture M1

[0058] 1.2 g of an amphiphilic unsaturated cationic monomer was dissolved in 140 g of deionized water to prepare mixture M1;

[0059] Preparation of S2 and mixture M2

[0060] 20g of 2-enamido-2-methylpropanesulfonic acid, 15g of N,N-dimethylacrylamide, and 3g of itaconic acid were dissolved in 25g of deionized water, and 4.4g of NaOH was added to adjust the pH to 6 to obtain mixture M2.

[0061] S3, Preparation of polymer materials

[0062] The mixture M1 obtained in S1 was transferred to a three-necked flask and heated in a 50°C water bath. The mixture M1 was stirred using a magnetic stirrer at a speed of 50 rpm. Subsequently, an aqueous solution of mixture M2 and the initiator was simultaneously added dropwise to the three-necked flask containing mixture M1 using a metering pump, with the addition time controlled at 5 hours. After the addition was completed, the temperature was raised to 55°C and the reaction was carried out for 5 hours. The polymer material SSL1 was obtained.

[0063] The initiator aqueous solution refers to the solution of 0.12g ammonium persulfate and 0.07g sodium bisulfite in 10g deionized water.

[0064] Example 2

[0065] The polymer material of this embodiment, by weight, comprises the following components: 15g of 2-enamido-2-methylpropanesulfonic acid, 10g of diacetone acrylamide, 2.5g of itaconic acid, 0.8g of an amphiphilic unsaturated cationic monomer (wherein, in the structure of the amphiphilic unsaturated cationic monomer, R is methyl and n is 13), 0.08g of ammonium persulfate (oxidation initiator), and 0.048g of sodium bisulfite (reduction initiator);

[0066] The polymer material in this embodiment is prepared through the following steps:

[0067] Preparation of S1 and mixture M1

[0068] 0.8 g of an amphiphilic unsaturated cationic monomer was dissolved in 120 g of deionized water to prepare mixture M1;

[0069] Preparation of S2 and mixture M2

[0070] 15g of 2-enamido-2-methylpropanesulfonic acid, 10g of diacetone acrylamide, and 2.5g of itaconic acid were dissolved in 25g of deionized water, and 3.2g of NaOH was added to adjust the pH to 6.5 to obtain mixture M2.

[0071] S3, Preparation of polymer materials

[0072] The mixture M1 obtained in S1 was transferred to a three-necked flask and heated in a 50°C water bath. The mixture M1 was stirred using a magnetic stirrer at 100 rpm. Subsequently, an aqueous solution of mixture M2 and the initiator was simultaneously added dropwise to the three-necked flask containing mixture M1 using a metering pump, with the addition time controlled at 4 hours. After the addition was completed, the temperature was raised to 55°C and the reaction was carried out for 4 hours. The polymer material SSL2 was obtained.

[0073] The initiator aqueous solution refers to the solution of 0.08g ammonium persulfate and 0.048g sodium bisulfite in 10g deionized water.

[0074] Example 3

[0075] The polymer material of this embodiment, by weight, comprises the following components: 22g 2-enamido-2-methylpropanesulfonic acid, 20g N,N-diethylacrylamide, 4g itaconic acid, 1.8g amphiphilic unsaturated cationic monomer (wherein, in the structure of the amphiphilic unsaturated cationic monomer, R is methyl and n is 11), 0.12g ammonium persulfate (oxidation initiator), and 0.07g sodium bisulfite (reduction initiator);

[0076] The polymer material in this embodiment is prepared through the following steps:

[0077] Preparation of S1 and mixture M1

[0078] 1.8 g of an amphiphilic unsaturated cationic monomer was dissolved in 180 g of deionized water to prepare mixture M1;

[0079] Preparation of S2 and mixture M2

[0080] 22g of 2-enamido-2-methylpropanesulfonic acid, 20g of N,N-diethylacrylamide, and 4g of itaconic acid were dissolved in 40g of deionized water, and 4.5g of NaOH was added to adjust the pH to 6.5 to obtain mixture M2.

[0081] S3, Preparation of polymer materials

[0082] The mixture M1 obtained in S1 was transferred to a three-necked flask and heated in a 50°C water bath. The mixture M1 was stirred using a magnetic stirrer at 150 rpm. Subsequently, an aqueous solution of mixture M2 and the initiator was simultaneously added dropwise to the three-necked flask containing mixture M1 using a metering pump, with the addition time controlled at 3 hours. After the addition was completed, the temperature was raised to 55°C and the reaction was carried out for 5 hours. The polymer material SSL3 was obtained.

[0083] The initiator aqueous solution refers to the solution of 0.12g ammonium persulfate and 0.07g sodium bisulfite in 10g deionized water.

[0084] Example 4

[0085] The polymer material of this embodiment, by weight, comprises the following components: 20g of 2-enamido-2-methylpropanesulfonic acid, 15g of N,N-dimethylacrylamide, 3g of itaconic acid, 1.2g of an amphiphilic unsaturated cationic monomer (wherein, in the structure of the amphiphilic unsaturated cationic monomer, R is H and n is 11), 0.12g of ammonium persulfate (oxidation initiator), and 0.07g of sodium bisulfite (reduction initiator);

[0086] The polymer material in this embodiment is prepared through the following steps:

[0087] Preparation of S1 and mixture M1

[0088] 1.2 g of an amphiphilic unsaturated cationic monomer was dissolved in 140 g of deionized water to prepare mixture M1;

[0089] Preparation of S2 and mixture M2

[0090] 20g of 2-enamido-2-methylpropanesulfonic acid, 15g of N,N-dimethylacrylamide, and 3g of itaconic acid were dissolved in 25g of deionized water, and 4.4g of NaOH was added to adjust the pH to 7 to obtain mixture M2.

[0091] S3, Preparation of polymer materials

[0092] The mixture M1 obtained in S1 was transferred to a three-necked flask and heated in a 50°C water bath. The mixture M1 was stirred using a magnetic stirrer at 100 rpm. Subsequently, an aqueous solution of mixture M2 and the initiator was simultaneously added dropwise to the three-necked flask containing mixture M1 using a metering pump, with the addition time controlled at 3 hours. After the addition was completed, the temperature was raised to 50°C and the reaction was carried out for 6 hours. The polymer material SSL4 was obtained.

[0093] The initiator aqueous solution refers to the solution of 0.12g ammonium persulfate and 0.07g sodium bisulfite in 10g deionized water.

[0094] Example 5

[0095] The polymer material of this embodiment, by weight, comprises the following components: 20g of 2-enamido-2-methylpropanesulfonic acid, 15g of N,N-dimethylacrylamide, 3g of itaconic acid, 1.2g of an amphiphilic unsaturated cationic monomer (wherein, in the structure of the amphiphilic unsaturated cationic monomer, R is -(CH2)3CH3 and n is 11), 0.12g of ammonium persulfate (oxidation initiator), and 0.07g of sodium bisulfite (reduction initiator);

[0096] The polymer material in this embodiment is prepared through the following steps:

[0097] Preparation of S1 and mixture M1

[0098] 1.2 g of an amphiphilic unsaturated cationic monomer was dissolved in 140 g of deionized water to prepare mixture M1;

[0099] Preparation of S2 and mixture M2

[0100] 20g of 2-enamido-2-methylpropanesulfonic acid, 15g of N,N-dimethylacrylamide, and 3g of itaconic acid were dissolved in 25g of deionized water, and 4.4g of NaOH was added to adjust the pH to 7 to obtain mixture M2.

[0101] S3, Preparation of polymer materials

[0102] The mixture M1 obtained in S1 was transferred to a three-necked flask and heated in a 50°C water bath. The mixture M1 was stirred using a magnetic stirrer at 100 rpm. Subsequently, an aqueous solution of mixture M2 and the initiator was simultaneously added dropwise to the three-necked flask containing mixture M1 using a metering pump, with the addition time controlled at 3 hours. After the addition was completed, the temperature was raised to 55°C and the reaction was carried out for 5 hours. The polymer material SSL5 was obtained.

[0103] The initiator aqueous solution refers to the solution of 0.12g ammonium persulfate and 0.07g sodium bisulfite in 10g deionized water.

[0104] Example 6

[0105] The polymer material of this embodiment, by weight, comprises the following components: 20g of 2-enamido-2-methylpropanesulfonic acid, 15g of N,N-dimethylacrylamide, 3g of itaconic acid, 1.2g of an amphiphilic unsaturated cationic monomer (wherein, in the structure of the amphiphilic unsaturated cationic monomer, R is methyl and n is 15), 0.12g of ammonium persulfate (oxidation initiator), and 0.07g of sodium bisulfite (reduction initiator);

[0106] The polymer material in this embodiment is prepared through the following steps:

[0107] Preparation of S1 and mixture M1

[0108] 1.2 g of an amphiphilic unsaturated cationic monomer was dissolved in 140 g of deionized water to prepare mixture M1;

[0109] Preparation of S2 and mixture M2

[0110] 20g of 2-enamido-2-methylpropanesulfonic acid, 15g of N,N-dimethylacrylamide, and 3g of itaconic acid were dissolved in 25g of deionized water, and 4.4g of NaOH was added to adjust the pH to 7 to obtain mixture M2.

[0111] S3, Preparation of polymer materials

[0112] The mixture M1 obtained in S1 was transferred to a three-necked flask and heated in a 50°C water bath. The mixture M1 was stirred using a magnetic stirrer at 100 rpm. Subsequently, an aqueous solution of mixture M2 and the initiator was simultaneously added dropwise to the three-necked flask containing mixture M1 using a metering pump, with the addition time controlled at 3 hours. After the addition was completed, the temperature was raised to 55°C and the reaction was carried out for 5 hours. The polymer material SSL6 was obtained.

[0113] The initiator aqueous solution refers to the solution of 0.12g ammonium persulfate and 0.07g sodium bisulfite in 10g deionized water.

[0114] Example 7

[0115] The polymer material of this embodiment, by weight, comprises the following components: 20g 2-enamido-2-methylpropanesulfonic acid, 15g N,N-dimethylacrylamide, 4g maleic acid, 1.2g amphiphilic unsaturated cationic monomer (wherein, in the structure of the amphiphilic unsaturated cationic monomer, R is methyl and n is 17), 0.12g ammonium persulfate (oxidation initiator), and 0.07g sodium bisulfite (reduction initiator);

[0116] The polymer material in this embodiment is prepared through the following steps:

[0117] Preparation of S1 and mixture M1

[0118] 1.2 g of an amphiphilic unsaturated cationic monomer was dissolved in 140 g of deionized water to prepare mixture M1;

[0119] Preparation of S2 and mixture M2

[0120] 20g of 2-enamido-2-methylpropanesulfonic acid, 15g of N,N-dimethylacrylamide, and 4g of maleic acid were dissolved in 25g of deionized water, and 4.4g of NaOH was added to adjust the pH to 7 to obtain mixture M2.

[0121] S3, Preparation of polymer materials

[0122] The mixture M1 obtained in S1 was transferred to a three-necked flask and heated in a 50°C water bath. The mixture M1 was stirred using a magnetic stirrer at 100 rpm. Subsequently, an aqueous solution of mixture M2 and the initiator was simultaneously added dropwise to the three-necked flask containing mixture M1 using a metering pump, with the addition time controlled at 3 hours. After the addition was completed, the temperature was raised to 55°C and the reaction was carried out for 5 hours. The polymer material SSL7 was obtained.

[0123] The initiator aqueous solution refers to the solution of 0.12g ammonium persulfate and 0.07g sodium bisulfite in 10g deionized water.

[0124] Example 8

[0125] The polymer material of this embodiment, by weight, comprises the following components: 20g 2-enamido-2-methylpropanesulfonic acid, 15g N,N-dimethylacrylamide, 4g maleic acid, 1.2g amphiphilic unsaturated cationic monomer (wherein, in the structure of the amphiphilic unsaturated cationic monomer, R is methyl and n is 17), 0.12g potassium persulfate (oxidation initiator), and 0.07g sodium hydroxide (reduction initiator);

[0126] The polymer material in this embodiment is prepared through the following steps:

[0127] Preparation of S1 and mixture M1

[0128] 1.2 g of an amphiphilic unsaturated cationic monomer was dissolved in 140 g of deionized water to prepare mixture M1;

[0129] Preparation of S2 and mixture M2

[0130] 20g of 2-enamido-2-methylpropanesulfonic acid, 15g of N,N-dimethylacrylamide, and 4g of maleic acid were dissolved in 25g of deionized water, and 4.4g of NaOH was added to adjust the pH to 7 to obtain mixture M2.

[0131] S3, Preparation of polymer materials

[0132] The mixture M1 obtained in S1 was transferred to a three-necked flask and heated in a 40°C water bath. The mixture M1 was stirred using a magnetic stirrer at 100 rpm. Subsequently, an aqueous solution of mixture M2 and the initiator was simultaneously added dropwise to the three-necked flask containing mixture M1 using a metering pump, with the addition time controlled at 3 hours. After the addition was completed, the temperature was raised to 50°C and the reaction was carried out for 5 hours. The polymer material SSL8 was obtained.

[0133] The initiator aqueous solution refers to the solution of 0.12g potassium persulfate and 0.07g sodium hydroxide in 10g deionized water.

[0134] Example 9

[0135] The polymer material of this embodiment, by weight, comprises the following components: 20g 2-enamido-2-methylpropanesulfonic acid, 15g N,N-dimethylacrylamide, 4g acrylic acid, 1.2g amphiphilic unsaturated cationic monomer (wherein, in the structure of the amphiphilic unsaturated cationic monomer, R is methyl and n is 19), 0.12g ammonium persulfate (oxidation initiator), and 0.07g sodium bisulfite (reduction initiator);

[0136] The polymer material in this embodiment is prepared through the following steps:

[0137] Preparation of S1 and mixture M1

[0138] 1.2 g of an amphiphilic unsaturated cationic monomer was dissolved in 140 g of deionized water to prepare mixture M1;

[0139] Preparation of S2 and mixture M2

[0140] 20g of 2-enamido-2-methylpropanesulfonic acid, 15g of N,N-dimethylacrylamide, and 4g of maleic acid were dissolved in 25g of deionized water, and 4.4g of NaOH was added to adjust the pH to 7 to obtain mixture M2.

[0141] S3, Preparation of polymer materials

[0142] The mixture M1 obtained in S1 was transferred to a three-necked flask and heated in a 50°C water bath. The mixture M1 was stirred using a magnetic stirrer at 100 rpm. Subsequently, an aqueous solution of mixture M2 and the initiator was simultaneously added dropwise to the three-necked flask containing mixture M1 using a metering pump, with the addition time controlled at 3 hours. After the addition was completed, the temperature was raised to 50°C and the reaction was carried out for 5 hours. The polymer material SSL9 was obtained.

[0143] The initiator aqueous solution refers to the solution of 0.12g ammonium persulfate and 0.07g sodium bisulfite in 10g deionized water.

[0144] Comparative Example 1

[0145] The difference between the smart polymer leak-proof material for cementing pre-fill fluid in Comparative Example 1 and Example 1 is that no amphiphilic unsaturated cationic monomer was added, and the resulting leak-proof material is DBL1.

[0146] Comparative Example 2

[0147] The difference between the smart polymer leak-proof material for cementing pre-fill fluid in Comparative Example 2 and Example 1 is that the amount of amphiphilic unsaturated cationic monomer added is 2g, and the resulting leak-proof material is DBL2.

[0148] Comparative Example 3

[0149] The difference between the smart polymer leak-proof material for cementing pre-fill fluid in Comparative Example 3 and Example 1 is that itaconic acid was not added, and the resulting leak-proof material is DBL3.

[0150] Comparative Example 4

[0151] The difference between the intelligent polymer leak-proof material for cementing pre-fill fluid in Comparative Example 4 and Example 1 is that the amount of itaconic acid added is 5g, and the resulting leak-proof material is DBL4.

[0152] Comparative Example 5

[0153] The smart polymer leak-proof material for cementing pre-fill fluid in Comparative Example 5 differs from that in Example 1 in that its preparation method is as follows:

[0154] A mixture M1 was prepared by dissolving an amphiphilic unsaturated cationic monomer in 180g of deionized water. Mixture M2 was prepared by dissolving propamido-2-methylpropanesulfonic acid, N,N-dimethylacrylamide, and itaconic acid in 40g of deionized water and adjusting the pH to 6.5 with 4.5g of NaOH. Initiator solution M3 was prepared by adding an initiator to 10g of deionized water. M1 was transferred to a three-necked flask and placed in a 50°C water bath, where it was stirred with a magnetic stirrer. Solutions M2 and M3 were simultaneously and completely added directly to the three-necked flask containing M1, rather than being added slowly and quantitatively using a metering pump. The temperature was then raised to 55°C for 5 hours to obtain a polymer solution, which was then used as a leak-proof material, DBL5.

[0155] The leak-proof performance of the polymer materials prepared in Examples 1-9 and Comparative Examples 1-5 was tested as follows, mainly including:

[0156] 1. Association effect

[0157] Association refers to the behavior of polymer molecular chains intertwining to form a spatial structure. Strong association is beneficial for forming a dense cemented structure during leak prevention and plugging. Association can be characterized by fluorescence spectroscopy of polymer aqueous solutions. Pyrene exhibits five fluorescence peaks in water, located near 373, 379, 384, 394, and 480 nm. When the number of hydrophobic associated structures in the polymer solution increases, pyrene can be more solubilized in these structures. Simultaneously, the fluorescence intensity ratio (I1 / I3) of peak 1 at 374 nm and peak 3 at 385 nm decreases. Therefore, the I1 / I3 value can be used to characterize the amount of hydrophobic associated structures; a lower I1 / I3 value indicates a greater number of hydrophobic associated structures. In the test, a fluorescence spectrophotometer was used to measure the emission spectrum of pyrene in the polymer solution, with a pyrene concentration of 5 × 10⁻⁶. -6 mol·L -1 The excitation wavelength is 335 nm, the excitation and emission slit widths are 5 nm and 2.5 nm, respectively, and the scan rate is 350-450 nm.

[0158] Following the above procedure, test the I1 / I3 values ​​of polymer materials with different concentrations at room temperature, and record the test results in Table 2 below; at the same time, test the I1 / I3 values ​​of polymer materials with a concentration of 0.5% at different temperatures, and record the test results in Table 3 below.

[0159] 2. Adsorption of solid particles

[0160] The total organic carbon (TOC) method can be used to analyze the adsorption of polymers on the surface of solid particles. 2g of polymer was added to 98g of water and fully dissolved. Then, 4g of a solid-phase auxiliary filling material was added to the aqueous solution and stirred thoroughly. Adsorption experiments were conducted under different conditions. After adsorption, the mixture was centrifuged and filtered. The filtrate was then diluted 20 times for TOC testing. The adsorption of polymers on the surface of solid particles can be obtained by analyzing the difference in total organic carbon (TOC) in the filtrate before and after the addition of the solid-phase auxiliary filling material. The calculation method is as follows:

[0161]

[0162] In the formula, q t : Adsorption amount during the test period (mg / g); CO: Initial concentration of the polymer solution (mg / L);

[0163] C t : Concentration of polymer solution at time t (mg / L); V: Volume of polymer solution (L); m: Mass of cement (g).

[0164] Using the above calculation formula, the amount of polymer material adsorbed on the surface of solid particles was determined at different temperatures.

[0165] Table 2 shows the I1 / I3 values ​​of polymer materials with different concentrations at room temperature.

[0166]

[0167]

[0168] As shown in Table 2, at room temperature, the I1 / I3 values ​​of the polymer materials SSL1 to SSL9 solutions prepared in the embodiments of this invention are all lower than those of pure water (1.8), indicating the presence of hydrophobic microregions in the system. With increasing polymer concentration, the polarity of the polymer solution decreases, indicating enhanced hydrophobic association. Within the concentration range of 0.3% to 0.7%, the micropolarity decreases rapidly, indicating that increasing polymer concentration enhances intermolecular association, and there exists a critical association concentration within this range; beyond this concentration, a large amount of hydrophobic association occurs in the solution.

[0169] Furthermore, the test results in Table 2 also reveal that, compared to Example 1, no amphiphilic cationic monomer was added in Comparative Example 1, therefore DBL1 did not exhibit significant hydrophobic association. In Comparative Example 5, because the polymer was prepared by directly mixing multiple monomers, the prepared DBL5 did not possess the designed molecular structure, thus its hydrophobic association was weak.

[0170] Table 3 shows the I1 / I3 values ​​of the 0.5% concentration polymer material at different temperatures.

[0171]

[0172]

[0173] The experimental results in Table 3 show that when the temperature rises to 50℃, the I1 / I3 value of the polymer materials prepared in Examples 1-9 decreases, indicating that more hydrophobic microdomains formed by the association of hydrophobic groups appear in the polymer solution. At 90℃, the I1 / I3 value decreases significantly, and the hydrophobicity of the solution is greatly enhanced, indicating the formation of a large number of hydrophobic microdomains. This is because as the temperature increases, the hydrophobic groups become more hydrophobic, and therefore they are more inclined to associate with each other, forming a denser network. This hydrophobic association can provide support for polymer leak prevention.

[0174] Table 4 shows the adsorption amount of 2% polymer material on the surface of solid particles at different temperatures and adsorption times of 1 hour.

[0175]

[0176] Based on the test results in Table 4, SSL1 to SSL9 exhibit high adsorption capacities. As the temperature increases to 90℃, the adsorption capacity first decreases and then increases. Comparing the adsorption capacities from 70℃ to 90℃, it can be seen that the equilibrium adsorption capacity increases with increasing adsorption temperature. This is because with higher temperature, the polymer molecular chains are in an extended state, increasing the number of groups in contact with cement particles, making them more easily adsorbed onto the adsorption sites on the surface of the hydration products. Furthermore, in Comparative Example 3, no unsaturated carboxylic acid monomer was added, therefore DBL3 had few adsorption sites and a very low adsorption capacity. In Comparative Example 5, because the polymer was prepared by directly mixing multiple monomers, the prepared DBL5 did not have the designed molecular structure, resulting in a low adsorption capacity. In Comparative Examples 2 to 4, the polymer structures did not match the design, and their adsorption capacities were also much lower than those in the examples.

[0177] Taking the polymer materials prepared in Examples 1-3 and Example 8 as examples, they were applied to a cementing intelligent leak-proof pre-flush fluid system, and the following performance evaluation tests were conducted. The specific operation was as follows: artificial cores or fracture simulation molds with different simulated fracture widths were fixed with a clamp, and then the clamp was placed in a high-temperature, high-pressure fracture sealing simulation device; the cementing intelligent leak-proof pre-flush fluid was poured into the vessel, the heating switch was turned on, and the slurry was heated to a preset temperature while simultaneously stirring the pre-flush fluid with a stirrer; the vessel containing the pre-flush fluid was connected to an air source, and the pressure was slowly increased to 1 MPa, then paused for 15 minutes, and this step was repeated, increasing the pressure by 1 MPa each time until a pressure breakthrough occurred; then the vessel was cooled to room temperature, depressurized, and cleaned. The cementing intelligent leak-proof pre-flush fluid was evaluated using the breakthrough pressure and cumulative leakage as indicators.

[0178] Application Example 1

[0179] The formula for intelligent cementing leak prevention pre-fill fluid is as follows: 100 parts by weight of tap water, 2 parts of polymer material SSL1, 2 parts of solid phase auxiliary filling material combination, 1.5 parts of solid phase support material, 2 parts of suspension stabilizer, and 0.3 parts of defoamer. After mixing evenly, the intelligent cementing leak prevention pre-fill fluid SP1 is obtained.

[0180] Application Example 2

[0181] The formula for intelligent cementing leak prevention pre-fill fluid is as follows: 100 parts by weight of tap water, 1 part of polymer material SSL1, 1 part of solid phase auxiliary filling material combination, 1 part of solid phase support material, 1.5 parts of suspension stabilizer, and 0.3 parts of defoamer are mixed evenly to obtain intelligent cementing leak prevention pre-fill fluid SP2.

[0182] Application Example 3

[0183] The formula for intelligent cementing leak prevention pre-fill fluid is as follows: 100 parts by weight of tap water, 3 parts of polymer material SSL1, 4 parts of solid phase auxiliary filling material combination, 2 parts of solid phase support material, 3 parts of suspension stabilizer, and 0.3 parts of defoamer are mixed evenly to obtain intelligent cementing leak prevention pre-fill fluid SP3.

[0184] Application Example 4

[0185] The formula for intelligent cementing leak prevention pre-fill fluid is as follows: 100 parts by weight of tap water, 2 parts of polymer material SSL2, 2 parts of solid phase auxiliary filling material combination, 1.5 parts of solid phase support material, 2 parts of suspension stabilizer, and 0.3 parts of defoamer. After mixing evenly, the intelligent cementing leak prevention pre-fill fluid SP4 is obtained.

[0186] Application Example 5

[0187] The formula for intelligent cementing leak prevention pre-fill fluid is as follows: 100 parts by weight of tap water, 2 parts of polymer material SSL3, 2 parts of solid phase auxiliary filling material combination, 1.5 parts of solid phase support material, 2 parts of suspension stabilizer, and 0.3 parts of defoamer. After mixing evenly, the intelligent cementing leak prevention pre-fill fluid SP5 is obtained.

[0188] Application Example 6

[0189] The formula for intelligent cementing leak prevention pre-fill fluid is as follows: 100 parts by weight of tap water, 2 parts of polymer material SSL8, 2 parts of solid phase auxiliary filling material combination, 1.5 parts of solid phase support material, 2 parts of suspension stabilizer, and 0.3 parts of defoamer. After mixing evenly, the intelligent cementing leak prevention pre-fill fluid SP6 is obtained.

[0190] Application Comparative Example 1

[0191] The difference from Application Example 1 is that the smart polymer leak-proof material 1 for cementing pre-flush fluid is not used.

[0192] Application Comparative Example 2

[0193] The difference from Application Example 1 is that no solid-phase auxiliary filling material combination is used.

[0194] Application Comparative Example 3

[0195] The difference from Application Example 1 is that no solid-phase support material is used.

[0196] Application Comparative Example 4

[0197] The difference from Application Example 1 is that the leak-proof material DBL1 prepared in Comparative Example 1 is used instead of the smart polymer leak-proof material 1 for cementing pre-filling fluid.

[0198] Application Comparative Example 5

[0199] The difference from Application Example 1 is that the leak-proof material DBL3 prepared in Comparative Example 3 is used instead of the smart polymer leak-proof material 1 for cementing pre-fill fluid.

[0200] Performance testing

[0201] 1. Test 1

[0202] The above application examples 1 to 6 and application comparative examples 1 to 5 were placed at 90°C to test the leak prevention and sealing performance of 1 mm cracks. The test results are recorded in Table 5 below.

[0203] Table 5. Leakage prevention and sealing performance of different pre-filled leak-proof liquids for 1mm cracks at 90℃.

[0204] Leak-proof pre-fluid Temperature / °C Pressure bearing capacity / MPa Pressure bearing time / min Leakage / mL SP1 90 9 >10 9 SP2 90 9 >10 14.2 SP3 90 9 >10 12.5 SP4 90 9 >10 14.5 SP5 90 8 >10 13 SP6 90 8 >10 10 SPD1 90 - - Total leak SPD2 90 - - Total leak SPD3 90 2 5 26 SPD4 90 2 4 22 SPD5 90 3 6 23

[0205] The data in Table 5 shows that the intelligent pre-flush fluids used in Application Examples 1-5 can effectively prevent and plug leaks in 1mm fractures at 90℃, with a pressure resistance >8MPa and a cumulative leakage of less than 15mL. However, in Comparative Example 1, no intelligent polymer pre-flush fluid material was added, thus failing to form a polymer-solid particle composite structure and preventing the formation of a "rigid material bridging + flexible material filling" structure in the fracture. Consequently, the pre-flush fluid completely failed to prevent and plug leaks, resulting in total leakage. In Comparative Example 2, no solid-phase auxiliary filling material was added, again failing to form a polymer-solid particle composite structure and resulting in total leakage. In Comparative Example 3, no solid-phase support material was added, failing to provide adequate support and thus exhibiting poor leak prevention capabilities. These three comparative examples demonstrate that the absence of any component renders the leak prevention and plugging function ineffective. The comparison between SP1 and SPD4 shows that polymers without the addition of amphiphilic unsaturated cationic monomers cannot associate effectively, resulting in poor leak prevention and plugging capabilities. The comparison between SP1 and SPD5 shows that polymers without the addition of unsaturated carboxylic acid monomers have poor adsorption capacity for solid phases, resulting in poor ability to form polymer-solid phase particle composite structures.

[0206] 2. Test Two

[0207] The above application example 1 was placed under different temperature conditions to test the leak prevention and sealing performance of a 1mm crack, and the test results are recorded in Table 6 below.

[0208] Table 6. Leak-proofing and sealing performance of pre-filled leak-proof fluid SP1 on 1mm cracks at different temperatures.

[0209] Leak-proof pre-fluid Temperature / °C Pressure bearing capacity / MPa Pressure bearing time / min Leakage / mL SP1 50 6 >10 11.2 SP1 60 6 >10 11 SP1 70 7 >10 10.5 SP1 80 8 >10 10.7 SP1 90 9 >10 9 SP1 100 9 >10 9 SP1 110 10 >10 8.5 SP1 120 10 >10 8.2 SP1 130 10 >10 8.5 SP1 140 9 >10 9 SP1 150 7 >10 10

[0210] Comparing the plugging effects at different temperatures reveals that as the temperature rises from 50℃ to 120℃, the plugging and sealing capabilities of the intelligent pre-flush cementing fluid gradually increase, along with its pressure-bearing capacity. Further temperature increases lead to a stable plugging capability, although the pressure-bearing capacity slightly decreases at 150℃. This is because the association effect of the intelligent polymer plugging material in the pre-flush cementing fluid is the primary characteristic responsible for its plugging ability, and the degree of association gradually increases with temperature. As the temperature rises from 50℃ to 120℃, the pressure-bearing capacity of the intelligent pre-flush cementing fluid increases. However, at 150℃, the water solubility of the polymer decreases, and the intermolecular network effect weakens, resulting in a reduced plugging capacity.

[0211] 3. Test Three

[0212] The leakage prevention and plugging performance of the cementing intelligent anti-leakage pre-filled fluids prepared for use cases 1 to 6 were tested at different temperatures on 3mm cracks, and the results are shown in Table 7.

[0213] Table 7. Leakage prevention and sealing performance of intelligent pre-flushing liquid for 3mm cracks at different temperatures.

[0214] Leak-proof pre-fluid Temperature / °C Pressure bearing capacity / MPa Pressure bearing time / min Leakage / mL SP1 50 6 >10 11.2 SP1 120 10 >10 8.2 SP1 150 7 >10 10 SP2 50 6 >10 11.5 SP2 120 10 >10 9.1 SP2 150 7 >10 10.5 SP3 50 6 >10 14.1 SP3 120 10 >10 8.5 SP3 150 8 >10 11.8 SP4 50 6 >10 13.5 SP4 120 10 >10 8.3 SP4 150 7 >10 13.7 SP5 50 6 >10 13.8 SP5 120 9 >10 9.1 SP5 150 6 >10 13.4 SP6 50 6 >10 14.1 SP6 120 9 >10 9.2 SP6 150 6 >10 13.9

[0215] The data in Table 7 shows that the intelligent cementing pre-fluid still exhibits good leakage prevention and plugging capabilities for 3mm fractures. Furthermore, the pressure-bearing capacity and cumulative filtration loss do not decrease with increasing fracture width; the pressure-bearing capacity is consistently greater than 6MPa, and the cumulative filtration loss is less than 15mL. Comparing the leakage prevention and plugging capabilities of different compositions of the intelligent cementing pre-fluid at different temperatures reveals a significant enhancement in leakage prevention at 120℃. This indicates that the system possesses certain temperature-sensitive characteristics, stemming from the intelligent cementing leakage prevention material. This is beneficial for precise leakage prevention in formations at specific depths.

[0216] 4. Test Four

[0217] The leakage prevention and plugging performance of the cementing intelligent anti-leakage pre-filled fluids prepared for use cases 1 to 6 were tested at different temperatures on 5mm cracks, and the results are shown in Table 8.

[0218] Table 8. Leakage prevention and sealing performance of different pre-filled leak-proof liquids for 5mm cracks at 90℃.

[0219] Leak-proof pre-fluid Temperature / °C Pressure bearing capacity / MPa Pressure bearing time / min Leakage / mL SP1 50 6 >10 11.7 SP1 120 10 >10 8.7 SP1 150 7 >10 10.8 SP2 50 6 >10 12.3 SP2 120 8 >10 9.3 SP2 150 5 >10 14.8 SP3 50 6 >10 14.4 SP3 120 10 >10 9 SP3 150 8 >10 12 SP4 50 6 >10 13.7 SP4 120 9 >10 8.6 SP4 150 6 >10 14 SP5 50 6 >10 14 SP5 120 8 >10 9 SP5 150 6 >10 13.8 SP6 50 6 >10 14.7 SP6 120 8 >10 9.9 SP6 150 6 >10 14.1

[0220] The results in Table 8 show that the intelligent pre-flush cementing fluid still exhibits good leak prevention and plugging capabilities for 5mm fractures. Furthermore, the pressure-bearing capacity and cumulative filtration loss do not decrease with increasing fracture width; the pressure-bearing capacity is consistently greater than 5MPa, and the cumulative filtration loss is less than 15mL. Comparing SP2 and SP3 reveals that when the fracture width is larger, the leak prevention and plugging capabilities of the pre-flush cementing fluid system, which uses a combination of intelligent polymer leak prevention material, solid-phase auxiliary filling material, and a lower content of solid-phase support material, decrease to some extent. This is because a 5mm fracture is relatively large, requiring a certain concentration of pressure-bearing material for plugging. Therefore, this system should not be designed for fracture widths exceeding 5mm.

[0221] 5. Test Five

[0222] The leakage prevention and plugging performance of the cementing intelligent anti-leakage pre-filled fluids prepared for use cases 1 to 6 were tested at different temperatures on a 0.5 mm crack. The results are shown in Table 9.

[0223] Table 9. Leak-proofing and sealing performance of different pre-filled leak-proofing solutions for 0.5mm cracks.

[0224] Leak-proof pre-fluid Temperature / °C Pressure bearing capacity / MPa Pressure bearing time / min Leakage / mL SP1 50 8 >10 10.2 SP1 120 12 >10 7.5 SP1 150 10 >10 8.8 SP2 50 8 >10 10 SP2 120 11 >10 7 SP2 150 8 >10 8.4 SP3 50 8 >10 8.8 SP3 120 11 >10 8.1 SP3 150 8 >10 102 SP4 50 7 >10 9.8 SP4 120 10 >10 7.4 SP4 150 8 >10 10.9 SP5 50 7 >10 10.1 SP5 120 10 >10 7.1 SP5 150 7 >10 8.7 SP6 50 7 >10 12.4 SP6 120 9 >10 7.5 SP6 150 7 >10 9.6

[0225] The data in Table 9 show that the intelligent cementing pre-flushing fluid has good leakage prevention and plugging capabilities for 0.5mm fractures, with pressure-bearing capacity greater than 9MPa and cumulative leakage less than 13mL. Test examples 1-5 demonstrate that the intelligent cementing pre-flushing fluid has good adaptability to fractures ranging from 0.5mm to 5mm, exhibiting intelligent leakage prevention characteristics.

[0226] 6. Test Six

[0227] The pre-filled cementing fluids prepared for use cases 1 to 6 were tested for their leak prevention and plugging performance on loose sandstone at different temperatures. The sandstone was mainly composed of pores of 60-120μm. The results are shown in Table 10.

[0228] Table 10. Leakage prevention and plugging performance of different pre-treatment fluids for loose sandstone at 90℃.

[0229] Leak-proof pre-fluid Temperature / °C Pressure bearing capacity / MPa Pressure bearing time / min Leakage / mL SP1 50 10 >10 8.2 SP1 120 13 >10 6.5 SP1 150 12 >10 7.1 SP2 50 10 >10 8.1 SP2 120 12 >10 7.2 SP2 150 11 >10 8.1 SP3 50 11 >10 9.4 SP3 120 11 >10 9.1 SP3 150 10 >10 9.2 SP4 50 8 >10 10.4 SP4 120 11 >10 8.8 SP4 150 10 >10 8.9 SP5 50 12 >10 9.4 SP5 120 12 >10 8.3 SP5 150 11 >10 9.1 SP6 50 9 >10 9.1 SP6 120 10 >10 7.9 SP6 150 9 >10 8.6

[0230] The data recorded in Table 10 show that the intelligent cementing pre-fluid has good leakage prevention and plugging capabilities for loose sandstone, with pressure-bearing capacity greater than 9MPa and cumulative leakage less than 10mL. Test examples 1-6 demonstrate that the intelligent cementing pre-fluid has good adaptability to fractures and voids of different opening sizes.

[0231] 7. Compatibility evaluation of the pre-filled fluid and cement slurry for testing the seven-stage intelligent anti-leakage test.

[0232] Taking Application Example 1 as an example, the effects of the intelligent pre-filled cementing fluid on the rheology, thickening time, and compressive strength of cement slurry were tested according to the national standard GB / T19139-2012 "Test Methods for Cement in Oil Wells". The compatibility between the intelligent pre-filled cementing fluid and cement slurry was analyzed. The monitoring results are recorded in Table 11 below.

[0233] Table 11 shows the compatibility evaluation of SP1, the pre-fill fluid for cementing intelligent leak prevention, and cement slurry.

[0234]

[0235]

[0236] Note: The cement used in this invention is Jiahua G-grade oil well cement (high sulfur resistance, HSR). # represents the percentage by mass of cement. Cement slurry formula: 600g Jiahua G-grade cement + 25% reinforcing material DRB-2S (200 mesh) + 4% toughening material DRE-3S + 1% microsilica + 1% early strength agent DRA-1S + 1% dispersant DRS-1S + 0.2% DRK-3S stabilizer + 2% fluid loss reducer DRF-3L + 1.2% anti-channeling regulator DRT-LT + 8% latex anti-channeling agent DRT-1L + 45% water + 0.5% defoamer DRX-2L (density 1.89g / cm³). 3 ).

[0237] As can be seen from the test results in Table 11, the pre-flush fluid has little impact on the rheological properties of the cement slurry and has good rheological compatibility. At the same time, it does not significantly shorten the thickening time of the cement slurry or greatly reduce the compressive strength of the cement stone, which can meet the requirements of cementing construction and subsequent cementing quality.

[0238] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. All modifications or applications made in accordance with the above embodiments are within the scope of protection of this technical solution.

[0239] Although specific embodiments of the invention have been described in detail, those skilled in the art will understand that various modifications and substitutions can be made to those details based on all the teachings disclosed, and all such changes are within the scope of protection of this invention. The full scope of this invention is given by the appended claims and any equivalents thereof.

Claims

1. A polymer material, characterized in that, The polymer material refers to a polymer in which anionic groups, cationic groups, and hydrophobic groups exist simultaneously on the molecular chain; the main chain of the polymer is a continuous linear structure, and the anionic groups, cationic groups, and hydrophobic groups are randomly connected to the main chain of the polymer as side groups through covalent bonds; The polymer material, by weight, comprises the following components: 15-22 parts of 2-enamido-2-methylpropanesulfonic acid, 0.8-1.8 parts of amphiphilic unsaturated cationic monomer, 2.5-4 parts of unsaturated carboxylic acid monomer, and 10-20 parts of unsaturated amide monomer. The amphiphilic unsaturated cationic monomer is shown in formula (I): ， Formula (I); where R is H or a C1-C4 alkyl group, and n is 11, 13, 15, 17 or 19; The unsaturated carboxylic acid monomer is selected from maleic acid, itaconic acid, or acrylic acid. The unsaturated amide monomer is selected from one of diacetone acrylamide, N,N-dimethylacrylamide or N,N-diethylacrylamide; The preparation method of the polymer material includes the following steps: Preparation of S1 and mixture M1 Dissolve the amphiphilic unsaturated cationic monomer in water to prepare mixture M1; Preparation of S2 and mixture M2 2-enamido-2-methylpropanesulfonic acid, unsaturated amide monomer and unsaturated carboxylic acid monomer were added to water in sequence, stirred to dissolve, and the pH of the solution was adjusted to obtain mixture M2. S3, Preparation of polymer solution Mixture M1 is prepared by heating S1 in a water bath. Mixture M2 prepared by S2 and an aqueous solution of initiator are added dropwise under stirring conditions. After the addition is completed, the temperature is raised to react and a polymer solution is obtained.

2. The polymer material according to claim 1, characterized in that, The polymer material also includes an initiator.

3. The polymer material according to claim 2, characterized in that, The initiator accounts for 0.15 to 0.5% of the total mass of the four substances: 2-enamido-2-methylpropanesulfonic acid, the amphiphilic unsaturated cationic monomer, the unsaturated carboxylic acid monomer, and the unsaturated amide monomer.

4. The polymer material according to claim 3, characterized in that, The initiator adopts an oxidant-reducant initiation system.

5. The polymer material according to claim 4, characterized in that, The oxidizing agent is selected from ammonium persulfate and / or potassium persulfate; the reducing agent is selected from sodium bisulfite and / or sodium hydroxide.

6. The polymer material according to claim 5, characterized in that, The molar ratio of the oxidant to the reducing agent is 1:(0.5~1).

7. A method for preparing a polymer material according to any one of claims 1 to 6, characterized in that, The method, in preparing polymer materials, simultaneously uses anionic groups introduced by 2-enamido-2-methylpropanesulfonic acid and unsaturated carboxylic acid monomers, as well as cationic and hydrophobic groups introduced by amphiphilic unsaturated cationic monomers. The preparation method of the polymer material includes the following steps: Preparation of S1 and mixture M1 Dissolve the amphiphilic unsaturated cationic monomer in water to prepare mixture M1; Preparation of S2 and mixture M2 2-enamido-2-methylpropanesulfonic acid, unsaturated amide monomer and unsaturated carboxylic acid monomer were added to water in sequence, stirred to dissolve, and the pH of the solution was adjusted to obtain mixture M2. S3, Preparation of polymer solution Mixture M1 is prepared by heating S1 in a water bath. Mixture M2 prepared by S2 and an aqueous solution of initiator are added dropwise under stirring conditions. After the addition is completed, the temperature is raised to react and a polymer solution is obtained.

8. The method for preparing the polymer material according to claim 7, characterized in that, In step S2, the pH of the solution is adjusted to 6-7.

9. The method for preparing the polymer material according to claim 7, characterized in that, In S3, the water bath temperature is set to 40-50°C.

10. The method for preparing the polymer material according to claim 7, characterized in that, In S3, the stirring speed is set to 50-150 rpm.

11. The method for preparing the polymer material according to claim 7, characterized in that, In S3, the dripping time is controlled to be 3 to 5 hours.

12. The method for preparing the polymer material according to claim 7, characterized in that, In step S3, the temperature is raised to 50–55°C and the reaction proceeds for 4–6 hours.

13. A leak-proof material, characterized in that, The leak-proof material is a polymer material as described in any one of claims 1 to 6 or a polymer material prepared by the preparation method described in any one of claims 7 to 12.

14. A pre-filling fluid for cementing and leak prevention, characterized in that, The cementing pre-flush fluid contains the leak-proof material as described in claim 13.

15. A cementing process, characterized in that, The cementing process uses the cementing pre-flush fluid as described in claim 14.

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