High-temperature-resistant and salt-resistant polymer additive for oil drilling and preparation method thereof

Abstract

The application discloses a high-temperature-resistant and salt-resistant polymer additive for oil drilling, which is prepared by the following method: S1, carrying out nucleophilic addition on ferrocene formaldehyde and 5-amino-2-chlorobenzoic acid; S2, adding a reducing agent to the system to reduce the intermediate 1; S3, adding a catalyst to carry out aromatic nucleophilic substitution reaction under the condition of strong base and high temperature; S4, finally, carrying out esterification reaction with methacryloyl chloride; and S5, carrying out reaction on the synthetic monomer, acrylamide monomer and alkenyl monomer to obtain the polymer. The application introduces the amphiphilic macromolecular benzene ring into the main chain by reasonably controlling the process, so that the prepared additive has the advantages of less by-product, stable performance, good filtration loss reduction effect, excellent temperature resistance and salt resistance.

Description

Technical Field

[0001] This invention relates to the field of drilling fluid technology, and in particular to a high-temperature and salt-resistant polymer additive for oil drilling and its preparation method. Background Technology

[0002] As oil and gas drilling continues, well depths are increasing, formation temperatures are rising, and the encountered formations are becoming more complex, particularly with the increasing prevalence of water-sensitive shale, salt rock, and salt-gypsum formations. This places higher demands on drilling fluid performance, especially its temperature resistance and damping properties. Polyacrylamide is primarily used in drilling fluids as a viscosity improver, filtration reducer, and coating agent to increase viscosity, control filtration loss, coat drill cuttings, and stabilize the wellbore. In high-temperature wells, polyacrylamide is prone to thermal and oxidative degradation, leading to a significant decrease in its viscosity-improving and filtration-reducing effects, and a deterioration in drilling fluid performance. Typically, its performance deteriorates significantly when the bottom hole temperature exceeds 150°C, necessitating modification treatment to improve its resistance to high temperatures and salt concentrations.

[0003] Current polyacrylamide modification typically involves introducing a benzene ring structure with strong temperature resistance into the main chain. For example, patent CN116425920B discloses a metallocene-modified polyacrylamide and its preparation method. This method involves polymerizing ferrocene comonomers containing polymeric double bonds, styrene monomers, acrylamide, and other monomers to introduce ferrocene containing benzene rings into the polymer main chain. Simultaneously, it forms a weakly crosslinked π-π stacking structure with the aromatic rings to improve its temperature resistance and shear strength. However, the amine groups on the polyacrylamide main chain are hydrophilic, while the introduced ferrocene and aromatic rings are strongly hydrophobic. The copolymerized alkenyl groups are also not hydrophilic. Even with the addition of a cosolvent for oil-water co-solvent mixing, the hydrophobic groups will spontaneously aggregate locally in the aqueous solution, resulting in an uneven distribution of hydrophilic and hydrophobic groups on the final polymer main chain. This significantly reduces its performance in drilling fluids. Furthermore, the subsequent mixing of hydrophilic and oleophilic cosolvents is difficult to separate from the modified product, resulting in low product purity. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-temperature and salt-resistant polymer additive for oil drilling and its preparation method, so as to solve the problems of uneven group distribution, small molecular weight of rigid groups, and weak high-temperature and salt resistance caused by the introduction of aromatic ring modification process in existing polyacrylamide oil drilling additives.

[0005] The objective of this invention is achieved through the following technical solution: a high-temperature and salt-resistant polymer additive for oil drilling, prepared according to the following steps. S1. Ferrocene formaldehyde was nucleophilically added to 5-amino-2-chlorobenzoic acid to obtain intermediate 1; S2. Add a reducing agent to the system to reduce intermediate 1 to obtain intermediate 2; S3. Intermediate 2 is added to a catalyst and subjected to an aromatic nucleophilic substitution reaction under strong base and high temperature conditions to obtain intermediate 3; S4. Intermediate 3 is esterified with methacryloyl chloride to obtain intermediate 4; S5. Intermediate 4 is reacted with acrylamide monomer and alkenyl monomer to obtain a polymer.

[0006] Preferably, in step S1, 5-amino-2-chlorobenzoic acid and glacial acetic acid catalyst are added to a solvent, heated to 45-60°C, and ferrocene formaldehyde is added and stirred for 6-8 hours. The mixture is then concentrated, crystallized, filtered, and dried to obtain intermediate 1.

[0007] Preferably, in step S1, the molar ratio of ferrocene formaldehyde to 5-amino-2-chlorobenzoic acid is 1.1-1.2:1.

[0008] Preferably, in step S2, intermediate 1 is cooled to 0-5°C, sodium borohydride is slowly added to carry out a reduction reaction, the reaction is refluxed for 2-3 hours, quenched by adding saturated ammonium chloride solution, the organic phase is extracted with dichloromethane, washed with saturated brine, dried, and the solvent is removed by evaporation to obtain intermediate 2.

[0009] Preferably, in step S3, intermediate 2 is added to purified water, the pH is adjusted to alkaline, copper powder is added, the temperature is raised to 150-200℃ and reacted for 8-12 hours, the temperature is lowered and the pH is adjusted to acidic, and the product is obtained by filtration, washing and drying.

[0010] Preferably, in step S4, intermediate 3 and triethylamine are added to dichloromethane solvent, and methacryloyl chloride is slowly added dropwise while the temperature is controlled at 0-5°C. After the addition is complete, the temperature is raised to room temperature, and the reaction is stirred for 6-8 hours. After the reaction is complete, the mixture is washed with water, the organic phase is dried with anhydrous sodium sulfate, filtered, and concentrated under reduced pressure to obtain the final product.

[0011] Preferably, in step S4, the molar ratio of intermediate 3: methacryloyl chloride: acid binder is 1:1.1-1.3:1.2-1.5.

[0012] Preferably, in step S5, intermediate 4, acrylamide monomer, and alkenyl monomer are added to an aqueous solution and adjusted to a weakly alkaline state. Under the protection of an inert gas, an initiator is added and the polymerization reaction is carried out at 50-70°C for 6-8 hours.

[0013] Preferably, the alkenyl monomer is one or more of 2-acrylamido-2-methylpropanesulfonic acid, N-vinylpyrrolidone, vinylsulfonic acid, and dimethyldiallylamine chloride.

[0014] The present invention has the following advantages: 1. This invention modifies the main chain of polyacrylamide by introducing a rigid benzene ring to improve its temperature and salt resistance. Existing technologies directly introduce ferrocene groups into the main chain. Due to the strong hydrophobicity of ferrocene, even with the addition of a co-solvent, the problem of group aggregation during emulsion polymerization cannot be completely solved. This invention employs an indirect grafting modification method. By selecting 5-amino-2-chlorobenzoic acid and ferrocene formaldehyde, the reaction between the amine and aldehyde groups grafts hydrophilic carboxyl groups onto the ferrocene, transforming the strongly hydrophobic ferrocene into an amphiphilic substance, replacing the added co-solvent and resulting in a more uniform distribution of the grafted groups. Furthermore, the benzene ring in 5-amino-2-chlorobenzoic acid can... Together with the benzene ring in ferrocene formaldehyde, it forms a sterically hindered macromolecule, making the polymer chain less prone to coiling and thermal degradation at high temperatures. This endows the polymer with excellent temperature resistance, achieving a gradient improvement in temperature resistance. Moreover, this sterically hindered macromolecule can also "shield" the amide groups on the main chain, slowing down the interaction between high-valence calcium and magnesium metal ions and the polymer chain, thereby delaying precipitation and maintaining the stability of the polymer in the brine system. Multiple uniformly distributed sterically hindered macromolecules can synergistically stretch the polyacrylamide main chain to keep it in an extended state, not only maintaining viscosity under high-temperature conditions, but also facilitating the adsorption of amide groups on the main chain onto the drilling inner wall, achieving excellent filtration loss reduction effect in conjunction with hydrophobic groups. 2. The present invention provides a method for preparing a high-temperature and salt-resistant polymer additive for oil drilling. First, an amine group is reacted with an aldehyde group, which not only introduces ferrocene but, more importantly, converts the active amino group into a stable secondary amine (-NH-), thus providing "permanent protection" to the amino group. Then, aromatic chlorine is converted into phenolic hydroxyl groups, which can "activate" the "inert" sites of aromatic chlorine, resulting in a thorough reaction, high conversion rate, and reduced side reactions caused by raw material residues. Next, a double bond is introduced through an esterification reaction, which avoids the double bond being destroyed or prematurely polymerized under strong alkaline and high-temperature conditions, achieving precise positioning of the reaction. Finally, alkenyl free radical polymerization is carried out, which can be precisely and dynamically adjusted according to the actual drilling conditions to meet the needs of different working conditions.

[0015] 3. The drilling polymer additive provided by this invention has few byproducts, stable performance, good filtration loss reduction effect, and excellent temperature and salt resistance. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will now be clearly and completely described.

[0017] A high-temperature and salt-resistant polymer additive for oil drilling is disclosed. This polymer has polyacrylamide as its main chain, with rigid benzene rings of macromolecules grafted onto the main chain to improve its salt and temperature resistance. It is prepared according to the following steps. S1. Ferrocene formaldehyde is nucleophilically added to 5-amino-2-chlorobenzoic acid. The nitrogen atom on 5-amino-2-chlorobenzoic acid acts as a nucleophile, attacking the carbonyl carbon of ferrocene formaldehyde to form an unstable alkanolamine (hydroxylamine) intermediate. Under acid catalysis, the alkanolamine intermediate is dehydrated to form an imine (Schiff base) containing a carbon-nitrogen double bond (C=N), i.e., intermediate 1. Intermediate 1 can link the benzene ring in 5-amino-2-chlorobenzoic acid to ferrocene, increasing the molecular weight of the rigid benzene ring, making the polymer less prone to aggregation under high temperature conditions, and improving the water solubility of ferrocene. S2. Add sodium borohydride reducing agent to the system to reduce intermediate 1 to obtain intermediate 2. Sodium borohydride can reduce the unstable imine (C=N) in intermediate 1 to a stable secondary amine (-CH2-NH-), improve its thermal decomposition ability, prepare for step 3, and avoid decomposition under high temperature and high alkalinity conditions to produce a large number of by-products. S3. Intermediate 2 is added to a catalyst and subjected to an aromatic nucleophilic substitution reaction under strong base and high temperature conditions to obtain intermediate 3. - Under the action of ), hydroxide ions, as nucleophiles, attack the electron-deficient aromatic ring carbon bonded to the chlorine atom, forming a negatively charged resonance stabilization intermediate. Chloride ions, as leaving groups, are removed, restoring the aromatic ring structure and generating phenoxy anions. After acidification, phenolic hydroxyl groups are obtained. S4. Intermediate 3 is esterified with methacryloyl chloride to obtain intermediate 4. The phenolic hydroxyl group (-OH) on intermediate 3 acts as a nucleophile to attack the carbonyl carbon of methacryloyl chloride, forming a tetrahedral intermediate. After the chloride ion is eliminated, a phenyl ester bond (-O-CO-) is generated to obtain intermediate 4. The polymerizable alkenyl group is attached to the rigid benzene ring of the macromolecule. S5. Intermediate 4 is subjected to free radical polymerization with acrylamide monomer and alkenyl monomer to introduce rigid macromolecules into the main chain of polyacrylamide to obtain the final product. Example 1

[0018] A high-temperature and salt-resistant polymer additive for oil drilling is prepared according to the following steps. S1. 1.2 mol of 5-amino-2-chlorobenzoic acid was added to anhydrous methanol, along with 1 mol of ferrocene formaldehyde and 1% of glacial acetic acid catalyst (1% of the total reaction volume). The mixture was heated to 60°C, stirred for 8 hours, concentrated under reduced pressure, crystallized, filtered, and dried to obtain intermediate 1. S2. Add 1 mol of intermediate 1 to anhydrous methanol, cool to 0-5℃, slowly add 3 mol of sodium borohydride to carry out the reduction reaction, reflux at 65℃ for 3 h, quench with saturated ammonium chloride solution, extract the organic phase with dichloromethane, wash with saturated brine, dry with anhydrous sodium sulfate, and evaporate to remove the solvent to obtain intermediate 2. S3. Add intermediate 2 to pure water, add 20% sodium hydroxide solution to adjust the pH to 12, add copper powder, heat to 200℃ and react for 8 hours, cool down and adjust the pH to 2, filter, wash and dry to obtain the product; S4. Add 1 mol of intermediate 3 and 1.5 mol of triethylamine to dichloromethane solvent, and slowly add methacrylamide chloride dropwise while controlling the temperature at 0-5℃. After the addition is complete, raise the temperature to room temperature and stir the reaction for 8 hours. After the reaction is complete, wash with water, dry the organic phase with anhydrous sodium sulfate, filter and concentrate under reduced pressure to obtain the final product. S5. According to the mass fraction, add 4-10 parts of intermediate, 40 parts of acrylamide monomer, and 5 parts of vinyl sulfonic acid to the aqueous solution, adjust to weak alkalinity, continuously introduce nitrogen gas, add sodium bisulfite initiator, and polymerize at 70°C for 6 hours to obtain a viscous adhesive. Example 2

[0019] A high-temperature and salt-resistant polymer additive for oil drilling is prepared according to the following steps. S1. 1.1 mol of 5-amino-2-chlorobenzoic acid was added to anhydrous methanol, along with 1 mol of ferrocene formaldehyde and 1% of glacial acetic acid catalyst (1% of the total reaction volume). The mixture was heated to 45°C and stirred for 8 hours. The mixture was then concentrated under reduced pressure, crystallized, filtered, and dried to obtain intermediate 1. S2. Add 1 mol of intermediate 1 to anhydrous methanol, cool to 0-5℃, slowly add 2 mol of sodium borohydride to carry out the reduction reaction, reflux at 65℃ for 2 h, quench with saturated ammonium chloride solution, extract the organic phase with dichloromethane, wash with saturated brine, dry with anhydrous sodium sulfate, and evaporate to remove the solvent to obtain intermediate 2. S3. Add intermediate 2 to pure water, add 20% sodium hydroxide solution to adjust the pH to 11, add copper powder, heat to 160℃ and react for 8 hours, cool down and adjust the pH to 2, filter, wash and dry to obtain the product; S4. Add 1 mol of intermediate 3 and 1.2 mol of triethylamine to dichloromethane solvent, and slowly add methacryloyl chloride dropwise while controlling the temperature at 0-5℃. After the addition is complete, raise the temperature to room temperature and stir the reaction for 7 hours. After the reaction is complete, wash with water, dry the organic phase with anhydrous sodium sulfate, filter and concentrate under reduced pressure to obtain the final product. S5. According to the mass fraction, add 4-5 parts of intermediate, 40 parts of acrylamide monomer, and 5 parts of alkenyl monomer to the aqueous solution, adjust to weak alkalinity, continuously purge with nitrogen gas, add sodium bisulfite initiator, and polymerize at 70°C for 6 hours to obtain a viscous adhesive. Example 3

[0020] A high-temperature and salt-resistant polymer additive for oil drilling is prepared according to the following steps. S1. 1.1 mol of 5-amino-2-chlorobenzoic acid was added to anhydrous methanol, along with 1 mol of ferrocene formaldehyde and 1% of glacial acetic acid catalyst (1% of the total reaction volume). The mixture was heated to 45°C and stirred for 8 hours. The mixture was then concentrated under reduced pressure, crystallized, filtered, and dried to obtain intermediate 1. S2. Add 1 mol of intermediate 1 to anhydrous methanol, cool to 0-5℃, slowly add 3 mol of sodium borohydride to carry out the reduction reaction, reflux at 65℃ for 2 h, quench with saturated ammonium chloride solution, extract the organic phase with dichloromethane, wash with saturated brine, dry with anhydrous sodium sulfate, and evaporate to remove the solvent to obtain intermediate 2. S3. Add intermediate 2 to pure water, add 20% sodium hydroxide solution to adjust the pH to 12, add copper powder, heat to 180℃ and react for 10h, cool down and adjust the pH to 2, filter, wash and dry to obtain the product; S4. Add 1 mol of intermediate 3 and 1.4 mol of triethylamine to dichloromethane solvent, and slowly add methacrylamide chloride dropwise while controlling the temperature at 0-5℃. After the addition is complete, raise the temperature to room temperature and stir the reaction for 7 hours. After the reaction is complete, wash with water, dry the organic phase with anhydrous sodium sulfate, filter and concentrate under reduced pressure to obtain the final product. S5. According to the mass fraction, add 48 parts of intermediate, 40 parts of acrylamide monomer and 5 parts of alkenyl monomer to the aqueous solution, adjust to weak alkalinity, continuously introduce nitrogen gas, add sodium bisulfite initiator and polymerize at 60°C for 7 hours to obtain a viscous adhesive.

[0021] Comparative Example According to the mass fraction, 10 parts of vinyl ferrocene, 40 parts of acrylamide monomer, 5 parts of styrene monomer, and 5 parts of sodium hexadecyl sulfonate were added to an aqueous solution, adjusted to a weakly alkaline state, nitrogen gas was continuously introduced, sodium bisulfite initiator was added, and polymerization reaction was carried out at 70°C for 6 hours to obtain a viscous adhesive.

[0022] Performance Evaluation Test method: Base slurry preparation: 3% bentonite slurry + 0.5% NaOH; Addition dosage: 2% filtration loss reducer; Aging conditions: 260℃ / 16h rolling aging; Test items: Apparent viscosity: GB / T16783.1 standard; High temperature and high pressure filtration loss: 220℃ / 3.5MPa; HTHP (High-Temperature Hydrochloride): A 4% NaCl saline solution; The test results are shown in the table below. As shown in the table above, the polymer prepared by this invention has a higher apparent viscosity than the comparative example and the base slurry value. The polymer prepared by this invention can improve the viscosity of drilling fluid. The introduction of the macromolecular benzene ring proves that the temperature resistance of polyacrylamide is improved, which is beneficial to maintaining the extension of the long chain at high temperature. The filtration loss value of the polymer prepared by this invention in brine is lower than that of the comparative example, which proves that the macromolecular benzene ring branched on the main chain has better filtration loss reduction performance than the small molecule benzene ring. The sulfonic acid group introduced on the macromolecular benzene ring is beneficial to the uniformity of the benzene ring branching on the main chain.

[0023] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a high-temperature and salt-resistant polymer additive for oil drilling, characterized in that, Includes the following steps, S1. Ferrocene formaldehyde was nucleophilically added to 5-amino-2-chlorobenzoic acid to obtain intermediate 1; S2. Add a reducing agent to the system to reduce intermediate 1 to obtain intermediate 2; S3. Intermediate 2 is added to a catalyst and subjected to an aromatic nucleophilic substitution reaction under strong base and high temperature conditions to obtain intermediate 3; S4. Intermediate 3 is esterified with methacryloyl chloride to obtain intermediate 4; S5. Intermediate 4 is reacted with acrylamide monomer and alkenyl monomer to obtain a polymer.

2. The method for preparing a high-temperature and salt-resistant polymer additive for oil drilling according to claim 1, characterized in that, In step S1, 5-amino-2-chlorobenzoic acid and glacial acetic acid catalyst are added to a solvent, heated to 45-60°C, and ferrocene formaldehyde is added and stirred for 6-8 hours. The mixture is then concentrated, crystallized, filtered, and dried to obtain intermediate 1.

3. The method for preparing a high-temperature and salt-resistant polymer additive for oil drilling according to claim 1, characterized in that, In step S1, the molar ratio of ferrocene formaldehyde to 5-amino-2-chlorobenzoic acid is 1.1-1.2:

1.

4. The method for preparing a high-temperature and salt-resistant polymer additive for oil drilling according to claim 1, characterized in that, In step S2, intermediate 1 is cooled to 0-5℃, sodium borohydride is slowly added to carry out a reduction reaction, the reaction is refluxed for 2-3 hours, quenched by adding saturated ammonium chloride solution, the organic phase is extracted with dichloromethane, washed with saturated brine, dried, and the solvent is removed by evaporation to obtain intermediate 2.

5. The method for preparing a high-temperature and salt-resistant polymer additive for oil drilling according to claim 1, characterized in that, In step S3, intermediate 2 is added to purified water, the pH is adjusted to alkaline, copper powder is added, the temperature is raised to 150-200℃ and reacted for 8-12 hours, the temperature is lowered and the pH is adjusted to acidic, and the product is obtained by filtration, washing and drying.

6. The method for preparing a high-temperature and salt-resistant polymer additive for oil drilling according to claim 1, characterized in that, In step S4, intermediate 3 and triethylamine are added to dichloromethane solvent, and methacryloyl chloride is slowly added dropwise while the temperature is controlled at 0-5℃. After the addition is complete, the temperature is raised to room temperature, and the reaction is stirred for 6-8 hours. After the reaction is complete, the mixture is washed with water, the organic phase is dried with anhydrous sodium sulfate, filtered, and concentrated under reduced pressure to obtain the final product.

7. The method for preparing a high-temperature and salt-resistant polymer additive for oil drilling according to claim 1, characterized in that, In step S4, the molar ratio of intermediate 3: methacryloyl chloride: acid binder is 1:1.1-1.3:1.2-1.

5.

8. The method for preparing a high-temperature and salt-resistant polymer additive for oil drilling according to claim 1, characterized in that, In step S5, intermediate 4, acrylamide monomer, and alkenyl monomer are added to an aqueous solution and adjusted to a weakly alkaline state. Under the protection of an inert gas, an initiator is added and the polymerization reaction is carried out at 50-70°C for 6-8 hours.

9. The method for preparing a high-temperature and salt-resistant polymer additive for oil drilling according to claim 1, characterized in that, The alkenyl monomer is one or more of 2-acrylamido-2-methylpropanesulfonic acid, N-vinylpyrrolidone, vinylsulfonic acid, and dimethyldiallylamine chloride.

10. A high-temperature and salt-resistant polymer additive for oil drilling and its preparation method, characterized in that, Prepared by any of the methods described in claims 1-9.

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