Preparation method of polymer-grafted modified sulfomethylated phenolic resin filtrate reducer for drilling fluid

Abstract

The invention provides a preparation method of a polymer graft modified sulfomethylated phenolic resin filtrate reducer, which comprises the following steps: (1) synthesis of polymer graft modified sulfomethylated phenolic resin: adding molten phenol into a reaction container, slowly adding an alkaline solution which is uniformly dissolved, water-soluble polymer powder, a 37% formaldehyde solution and a pre-dissolved sulfonating agent solution under a stirring condition, and carrying out reflux reaction; and (2) controlling the reaction degree, namely supplementing water into the system every 30-80 minutes during the reaction, adjusting the reaction degree, reducing the temperature of the reaction glue solution to 50 DEG C by utilizing circulating water after the reaction is finished, and drying the reaction glue solution into powder by spray drying. The prepared sulfomethylated phenolic resin is used as a filtrate reducer, the temperature resistance can reach 180 DEG C, the salt resistance can reach 30% NaCl, meanwhile, the use amount is only 50% of that of similar products, and the product has no obvious effect of increasing the apparent viscosity of drilling fluid when used.

Description

Technical Field

[0001] The invention belongs to the technical field of drilling fluid treatment agents in the petroleum and natural gas industry, and particularly relates to a preparation method of a polymer-grafted modified sulfomethylphenolic resin fluid loss reducer for drilling fluid. Background Art

[0002] With the continuous development of shallow and simple formations, oil exploration and development are expanding into deeper and more complex formations. The drilling environment is becoming increasingly complex, often accompanied by high temperatures, high pressures, and highly mineralized formations. Filter loss reducers for drilling fluids effectively control fluid loss, ensuring safe and efficient drilling. They are the most widely used and most expensive drilling fluid treatment agent in the oil drilling process. Complex and harsh formation environments require filter loss reducers with superior resistance to high temperatures, salt, and calcium and magnesium ion contamination.

[0003] Since the 1970s, sulfomethyl phenolic resin (SMP) fluid loss additives have been widely used in deep and complex well exploration and operations due to their excellent resistance to high temperatures and salts. Numerous modified derivatives have been developed. These products offer stable temperature and salt tolerance and excellent fluid loss reduction. A high-temperature, deep-well drilling fluid system ("tri-sulfonated" drilling fluid) composed of sulfonated lignite (SMC) and sulfonated tannin (SMT) effectively reduces high-temperature, high-pressure fluid loss. SMP products have become one of the most widely used key treatment agents in high-temperature, deep-well water-based drilling fluids both domestically and internationally.

[0004] SMP products must meet three conditions to be effective in field applications: first, they must be used in deep-well drilling fluids; second, they must be used in saline drilling fluids, particularly when the salt content is high; and third, they must be used simultaneously with cross-linking treatment agents such as sulfonated lignite or sulfonated tannin extracts, making them ineffective when used independently. Furthermore, the dosage of sulfomethylphenolic resin is high, typically 4%-6%, resulting in waste of drilling fluid material and increased drilling costs. Furthermore, SMP products generate a large number of bubbles during use, affecting the stability of drilling fluid performance.

[0005] Chinese patent application CN114736342A, "A method for preparing a high-temperature-resistant and high-efficiency sulfomethylphenol-formaldehyde resin," discloses a method for preparing a high-temperature-resistant and high-efficiency sulfomethylphenol-formaldehyde resin. The method comprises reacting phenol, p-hydroxyphenoxyacetic acid, and an alkaline sulfonic acid agent, followed by dropwise addition of formaldehyde. The reaction is heated to a system viscosity of 60-80 mPa·s, followed by dilution with water, followed by addition of sodium p-hydroxybenzenesulfonate, and then an oxidant. Finally, a cross-linking agent is added to react, thereby obtaining a high-temperature-resistant and salt-resistant sulfomethylphenol-formaldehyde resin. The added oxidant can further oxidize the non-temperature-resistant groups such as ether bonds produced by the side reaction to form temperature-resistant groups such as carboxyl groups. An appropriate amount of cross-linking agent increases the degree of cross-linking of the resin material, allowing the prepared product to be used alone. At the same time, the sulfomethylphenol-formaldehyde resin obtained by this method introduces carboxyl and benzenesulfonic acid groups into its structure, which can better adsorb on the clay surface, forming a spatial grid structure, giving the product good fluid loss reduction performance. However, its preparation process is relatively complex and the production cycle is long.

[0006] Chinese patent application CN114085343A, "A Modified Sulfomethyl Phenolic Resin Fluid Loss Control Agent for Drilling Fluids and Its Preparation Method," discloses a method for preparing a modified sulfomethyl phenolic resin for drilling fluids. The modified sulfomethyl phenolic resin fluid loss control agent is obtained by sulfonating and polycondensing raw materials such as hydroxyphenylacetate, phenol, formaldehyde, and sulfite. The high sulfonic acid content in the sulfomethyl phenolic resin structure improves the product's solubility, but its adsorption to solids is weak. The introduction of sodium hydroxyphenylacetate increases the carboxyl content in the product's molecular structure, improving its adsorption to solids. Therefore, the appropriate amount of sodium hydroxyphenylacetate incorporated into the sulfomethyl phenolic resin structure can increase the product's adsorption to solids such as clay, improving its fluid loss control performance. When added at a dosage of 4%, the product maintained good fluid loss control performance after aging at temperatures between 90°C and 180°C, indicating its applicability as a fluid loss control agent in deep, medium-deep, and shallow wells. However, its high-temperature and high-pressure fluid loss performance was not tested.

[0007] Chinese patent application CN106608958A, "A Method for Producing Carboxymethylsulfonylphenol-Formaldehyde Resin and Application of Carboxymethylsulfonylphenol-Formaldehyde Resin," discloses a method for producing a carboxymethylsulfonylphenol-Formaldehyde resin. The resin is synthesized using partially carboxymethylated phenol and phenol, and then subjected to cationization and sulfonation reactions to obtain a modified carboxymethylsulfonylphenol-Formaldehyde resin. A substitution reaction adds carboxymethyl groups to the benzene ring, thereby improving the product's resistance to calcium and magnesium ions. Subsequent cationic modification of the carboxymethylsulfonylphenol-Formaldehyde resin significantly enhances its adsorption capacity on clay surfaces. This product can maintain the drilling fluid's temperature and salt resistance while reducing the amount of treatment agent used, but the preparation process involves numerous steps and is somewhat complex.

[0008] Chinese patent application CN106188446A "A modified sulfomethyl phenolic resin and a drilling mud treating agent containing the same" provides a modified sulfomethyl phenolic resin, which is prepared by the following steps, calculated by weight: (1) adding phenol, dihydric phenol, formaldehyde and 20% hydrochloric acid solution into a reaction kettle, and reacting at 97°C-105°C for 10-15 minutes; (2) adding 20% ​​sulfonating agent solution, and then adding sulfonating agent solution, and reacting at 97°C-105°C for 10-15 minutes; The invention also provides a drilling mud treating agent, which is composed of the following components in parts by weight: 16-22 parts of modified sulfonyl phenolic resin, 8-12 parts of sodium hydroxypropyl sulfonate, 6-10 parts of oleamide hydroxysulfobetaine, 5-8 parts of trifluoropropyl methylcyclotrisiloxane, 12-18 parts of acrylamide, 0.02-0.1 parts of ammonium persulfate, 1-5 parts of nano titanium dioxide, and 3-6 parts of sodium bicarbonate. The obtained drilling fluid mud treatment agent has a temperature resistance of up to 200°C, and the addition amount is generally 1.0%-3.0%; the dosage is only about 50% of similar products, which reduces production costs and reduces the amount of mud used. However, its preparation process is cumbersome, the production cycle is long, and the production efficiency is low.

[0009] Chinese patent application CN1047886343A, "A Method for Preparing a High-Temperature-Resistant Modified Sulfomethylphenol-Formaldehyde Resin for Drilling Fluid," discloses a method for preparing a high-temperature-resistant modified sulfomethylphenol-formaldehyde resin for drilling fluid. The method comprises the following steps: 1) adding a phenolic reactant, an aldehyde reactant, and an acid catalyst to a reactor, mixing and stirring, and reacting at 50°C-110°C for 10-400 minutes; 2) adding an alkaline catalyst and an aldehyde reactant to the reactor, adding a sulfonating agent in batches while maintaining the temperature between 50°C-110°C, and reacting for 10-600 minutes; 3) after the reaction, cooling the reaction mixture, discharging the mixture, and spray drying the mixture to obtain the product. The modified sulfomethylphenol-formaldehyde resin prepared by this invention has a temperature resistance of up to 200°C. After addition, under aging conditions at 200°C, it can effectively reduce high-temperature and high-pressure fluid loss in drilling fluids, achieving salt tolerance of up to 15% NaCl. However, the production process is complex, and the high dosage required increases drilling costs.

[0010] Therefore, how to provide a high-temperature and salt-resistant sulfonated methylphenolic resin high-efficiency fluid loss reducer with a simple production process and low usage amount is a problem that people in this field need to solve urgently. Summary of the Invention

[0011] In response to the shortcomings of the existing technology, the present invention provides a method for preparing a polymer-grafted modified sulfomethylphenolic resin fluid loss reducer. The sulfomethylphenolic resin prepared by this method can be used as a fluid loss reducer with a temperature resistance of up to 180°C and a salt resistance of up to 30% NaCl. At the same time, the usage amount is only 50% of that of similar products. Moreover, when used, the product has no obvious effect on increasing the apparent viscosity of the drilling fluid.

[0012] In order to achieve the above object, the present invention provides a method for preparing a polymer-grafted modified sulfomethylphenolic resin fluid loss additive, comprising the following steps:

[0013] (1) Synthesis of polymer-grafted modified sulfomethylphenolic resin

[0014] Add molten phenol to the reaction vessel, then slowly add a uniformly dissolved alkaline solution, water-soluble polymer powder, 37% formaldehyde solution and pre-dissolved sulfonating agent solution under stirring conditions, and reflux reaction;

[0015] (2) Control of reaction degree

[0016] During the reaction, the viscosity of the system will gradually increase. During the reaction, water is added to the system every 30-80 minutes to adjust the reaction rate. After the reaction is completed, the temperature of the reaction solution is lowered to 50°C using circulating water, and then the reaction solution is dried into powder by spray drying.

[0017] The present invention introduces a water-soluble polymer in the early stage of synthesizing the sulfomethylphenolic resin. During the reaction process, polycondensation, sulfonation and grafting reactions occur simultaneously. This is different from the post-crosslinking process of the polymer and the sulfomethylphenolic resin studied by previous researchers. The process of the present invention has higher reaction efficiency, shorter production cycle and more stable product performance.

[0018] The product of the present invention increases the adsorption capacity of the resin product on the clay by introducing the polymer. During use, the added amount is only 50% of that of similar products, which can reduce drilling costs and reduce the amount of drilling fluid used.

[0019] According to a preferred embodiment of the technical solution of the present invention, the base used as a catalyst in step (1) is one or more of sodium hydroxide, potassium hydroxide or anhydrous sodium carbonate, which are prepared into an aqueous solution, preferably a 25% aqueous solution.

[0020] The mass ratio of the alkaline catalyst (based on dry mass): phenol is (10-40):80.

[0021] Preferably, in step (1), the polymer is a water-soluble high molecular weight drilling fluid temperature and salt resistance fluid loss reducer, such as one or more of hydrolyzed polyacrylonitrile salt, sodium polyacrylate, and sulfonate polymer, and the molecular weight is preferably 3000-500,000.

[0022] In the present invention, the addition amount of polymer powder is preferably such that the mass ratio of polymer powder to phenol is (8-40):80. If the amount of polymer added is too high, the viscosity of the reaction system will be too high, which will affect the polymerization reaction of the phenolic resin and result in poor product performance.

[0023] According to a preferred embodiment of the technical solution of the present invention, in step (1), the sulfonating agent used is one or more of sodium metabisulfite, anhydrous sodium sulfite and anhydrous sodium bisulfite, preferably prepared as a 40% aqueous solution for use.

[0024] Further preferably, in step (1), the dosage ratio of the materials used is preferably such that the mass ratio of phenol: 37% formaldehyde solution: sulfonating agent is 80: (10-40): (140-190): (60-85); more preferably, the mass ratio of phenol: 37% formaldehyde solution: sulfonating agent is 80: 160: 80.

[0025] In a preferred embodiment, in step (1), phenol, alkaline solution, polymer powder, 37% formaldehyde solution, and sulfonating agent are refluxed at 90°C-110°C for 3-5 hours; preferably, the phenol, alkaline solution, polymer powder, 37% formaldehyde solution, and sulfonating agent are reacted at 97°C-100°C for 3-4 hours.

[0026] According to a preferred embodiment of the technical solution of the present invention, in step (2), the mass ratio of the total amount of added water to phenol is (80-140):80; preferably, the mass ratio of the total amount of added water to phenol is 120:80.

[0027] In step (2), the time interval for adding water is 30 min-80 min; preferably, the time interval for adding water is 40-60 min.

[0028] The present invention has the following effects:

[0029] (1) The present invention introduces a polymer structure into the molecular chain of traditional sulfomethylphenolic resin, utilizing the excellent temperature and salt resistance of water-soluble polymers to increase the adsorption capacity of the product on clay. At the same time, the product still has a good fluid loss reduction effect when the usage amount is only 50% of similar products;

[0030] (2) In the synthesis process of the present invention, phenol, formaldehyde, sulfonating agent and polymer are subjected to graft polymerization reaction by a "one-pot process" to generate polymer-grafted modified sulfomethylphenolic resin. Therefore, the molecular weight of the polymer used should not be too large, otherwise the viscosity of the system in the initial stage of the reaction is too high, which affects the synthesis of the phenolic resin;

[0031] (3) The present invention uses a water-soluble polymer with a molecular weight of less than 300,000 as a modifier. During the reaction, polycondensation, sulfonation, and grafting reactions occur simultaneously. This is different from the post-crosslinking process studied by previous researchers. The process of the present invention has higher reaction efficiency, shorter production cycle, more stable product performance, and a lower proportion of high-cost polymer addition required.

[0032] (4) The preparation method of the present invention is simple and easy to operate, has a short production cycle, has fewer product side reactions, and the synthesis process does not require high equipment;

[0033] (5) The polymer grafted modified sulfomethylphenolic resin product of the present invention has certain temperature resistance and can withstand high temperatures of 180°C, which can meet the requirements of deep well drilling;

[0034] (6) The polymer grafted modified sulfomethylphenolic resin product of the present invention has strong salt resistance and can withstand a salt concentration of up to 30% NaCl. It can effectively reduce the filtration loss of drilling fluid in drilling fluids with a chloride ion content of 160 g / L or more near saturated brine, while maintaining good fluidity of the drilling fluid. It is an excellent salt-resistant filtration reducer.

[0035] (7) The product of the present invention can be used in an environment of 180°C and 30% NaCl, has no significant viscosity-increasing effect on the mud, and can effectively reduce the API fluid loss and high-temperature and high-pressure fluid loss of the drilling fluid;

[0036] (8) The types of polymer modifiers used in the present invention are relatively wide, and the technical versatility is high. More cost-effective polymers can be used to reduce production costs. Therefore, the products of the present invention have extremely high development potential and broad market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The process flow chart of the polymer grafted modified sulfomethylphenolic resin fluid loss reducer for drilling fluid of the present invention is shown. DETAILED DESCRIPTION

[0038] The present invention will be described in detail below through specific embodiments, and the features and advantages of the present invention will become clearer and more distinct with these descriptions.

[0039] Example

[0040] The phenol, sodium hydroxide, potassium hydroxide, anhydrous sodium carbonate, 37% formaldehyde solution, sodium metabisulfite, anhydrous sodium sulfite and anhydrous sodium bisulfite used in the examples were all chemically pure reagents and were purchased from Beijing Yili Fine Chemicals Co., Ltd.

[0041] The hydrolyzed polyacrylonitrile sodium salt (ST-NaPAN) used in the examples was purchased from Santuo Chemical Products Co., Ltd. in Baoding, Hebei Province. It was prepared by alkaline hydrolysis of waste acrylic fibers. The functional groups mainly contained amide, carboxyl and a small amount of cyano groups, and the molecular weight was about 500,000.

[0042] The low molecular weight sulfonate polymer (WH-Polymer) used in the examples was purchased from Weihui Chemical Co., Ltd., Henan Province. It is modified by polymerization of AMPS, low molecular weight amide, polyhydroxycarboxylic acid, cosolvent, etc. The functional groups mainly contain sulfonic acid group, amide group and carboxyl group, and the molecular weight is about 200,000.

[0043] The low molecular weight sodium polyacrylate (CUP) used in the examples was purchased from Hubei Tianyi Chemical Co., Ltd. Its main component is sodium polyacrylate, the functional groups mainly contain carboxyl groups, and the molecular weight is about 3000.

[0044] The 5A polymer used in the examples was prepared in the inventor's laboratory. It was copolymerized using acrylic acid (AA), acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), attapulgite (ATP), and 2-allyl-2-methylammonium chloride (DMDAAC) in a mass ratio of 2.25:3.75:0.75:2.5:0.75. Ammonium persulfate and sodium bisulfite were used as a composite redox initiator in a molar ratio of 1:1, with the initiator added at a concentration of 0.2% of the total monomer mass. The polymer was reacted at 80°C for 30 minutes, then dried and pulverized. The functional groups primarily include carboxyl, amide, and sulfonic acid groups, with a molecular weight of approximately 300,000.

[0045] The sulfomethylphenolic resin products (SMP-I and SMP-II) used in the comparative examples are industrial-grade products purchased from Shandong Weifang Sanlibenuo Chemical Industry Co., Ltd. and Sichuan Zhengrong Industrial Co., Ltd., respectively.

[0046] The sulfonated tannin extract (SMK) used in the experimental test is an industrial-grade reagent purchased from Chengdu Chuanfeng Chemical Engineering Co., Ltd. Example 1 Preparation of polymer-grafted modified sulfonated methylphenolic resin fluid loss reducer

[0047] (1) 8 g of sodium hydroxide was uniformly dissolved in 25 g of water to prepare an alkaline catalyst solution; 40 g of sodium metabisulfite was uniformly dissolved in 80 g of water to prepare a sulfonating agent solution;

[0048] (2) Under stirring conditions, 40 g of molten phenol, the prepared alkaline solution, 13 g of hydrolyzed polyacrylonitrile sodium salt ST-NaPAN powder, 75 g of 37% formaldehyde solution, and the prepared sulfonating agent solution were slowly added to a three-necked flask in sequence. After adding 20 g of water, stirring was continued and the reaction was refluxed at 100°C for 3 h.

[0049] (3) Observe the change in the viscosity of the system in the three-necked flask, and add 20 mL of water to the system at 60 min, 100 min, and 140 min of reaction to adjust the reaction degree. After the reaction is completed, reduce the temperature of the reaction gel to 50 °C, and then dry the reaction gel into powder by spray drying.

[0050] Example 2 Preparation of polymer grafted modified sulfomethylphenolic resin fluid loss reducer

[0051] (1) 15 g of anhydrous sodium carbonate was uniformly dissolved in 50 g of water to prepare an alkaline catalyst solution; 43 g of sodium metabisulfite was uniformly dissolved in 80 g of water to prepare a sulfonating agent solution;

[0052] (2) Under stirring conditions, 40 g of molten phenol, the prepared alkaline solution, 12 g of low molecular weight sulfonate polymer WH-Polymer powder, 80 g of 37% formaldehyde solution, and the prepared sulfonating agent solution were slowly added to a three-necked flask in sequence. After adding 20 g of water, stirring was continued and the mixture was refluxed at 97°C for 3 h.

[0053] (3) Observe the change in the viscosity of the system in the three-necked flask, and add 20 mL of water to the system at 40 min, 80 min, 120 min, and 160 min of reaction to adjust the reaction degree. After the reaction is completed, reduce the temperature of the reaction gel to 50 °C, and then dry the reaction gel into powder by spray drying.

[0054] Example 3 Preparation of polymer grafted modified sulfomethylphenolic resin fluid loss reducer

[0055] (1) 2 g of sodium hydroxide and 12 g of anhydrous sodium carbonate were uniformly dissolved in 50 g of water to prepare an alkaline catalyst solution; 45 g of sodium metabisulfite was uniformly dissolved in 80 g of water to prepare a sulfonating agent solution;

[0056] (2) Under stirring conditions, 40 g of molten phenol, the prepared alkaline solution, 16 g of low molecular weight sulfonate polymer WH-Polymer powder, 85 g of 37% formaldehyde solution, and the prepared sulfonating agent solution were slowly added to a three-necked flask in sequence. After adding 20 g of water, stirring was continued and the mixture was refluxed at 105°C for 4 h.

[0057] (3) Observe the change in the viscosity of the system in the three-necked flask, and add 20 mL of water to the system at 60 min, 120 min, and 180 min of reaction to adjust the reaction degree. After the reaction is completed, reduce the temperature of the reaction gel to 50 °C and then dry the reaction gel into powder by spray drying.

[0058] Example 4 Preparation of polymer grafted modified sulfomethylphenolic resin fluid loss reducer

[0059] (1) 1 g of sodium hydroxide and 14 g of anhydrous sodium carbonate were uniformly dissolved in 50 g of water to prepare an alkaline catalyst solution; 32 g of sodium metabisulfite was uniformly dissolved in 80 g of water to prepare a sulfonating agent solution;

[0060] (2) Under stirring conditions, 40 g of molten phenol, the prepared alkaline solution, 12 g of low molecular weight sodium polyacrylate CUP powder, 76 g of 37% formaldehyde solution, and the prepared sulfonating agent solution were slowly added to a three-necked flask in sequence. After adding 20 g of water, stirring was continued and the mixture was refluxed at 100°C for 3 h.

[0061] (3) Observe the change in the viscosity of the system in the three-necked flask, and add 20 mL of water to the system at 60 min, 100 min, and 140 min of reaction to adjust the reaction degree. After the reaction is completed, reduce the temperature of the reaction gel to 50 °C, and then dry the reaction gel into powder by spray drying.

[0062] Example 5 Preparation of polymer grafted modified sulfomethylphenolic resin fluid loss reducer

[0063] (1) 2 g of sodium hydroxide and 15 g of anhydrous sodium carbonate were uniformly dissolved in 50 g of water to prepare an alkaline catalyst solution; 35 g of sodium metabisulfite was uniformly dissolved in 80 g of water to prepare a sulfonating agent solution;

[0064] (2) Under stirring conditions, 40 g of molten phenol, the prepared alkaline solution, 3 g of 5A powder, 70 g of 37% formaldehyde solution, and the prepared sulfonating agent solution were slowly added to a three-necked flask in sequence. After adding 20 g of water, the mixture was stirred continuously and refluxed at 100°C for 3 h.

[0065] (3) Observe the change in the viscosity of the system in the three-necked flask, and add 20 mL of water to the system at 60 min, 100 min, and 140 min of reaction to adjust the reaction degree. After the reaction is completed, reduce the temperature of the reaction gel to 50 °C, and then dry the reaction gel into powder by spray drying.

[0066] Example 6 Preparation of polymer grafted modified sulfomethylphenolic resin fluid loss reducer

[0067] (1) 1.5 g of sodium hydroxide and 16 g of anhydrous sodium carbonate were uniformly dissolved in 50 g of water to prepare an alkaline catalyst solution; 38 g of sodium metabisulfite was uniformly dissolved in 80 g of water to prepare a sulfonating agent solution;

[0068] (2) Under stirring conditions, 40 g of molten phenol, the prepared alkaline solution, 6 g of 5A powder, 80 g of formaldehyde solution, and the prepared sulfonating agent solution were slowly added to a three-necked flask in sequence. After adding 20 g of water, stirring was continued and the mixture was refluxed at 100°C for 3 h.

[0069] (3) Observe the change in the viscosity of the system in the three-necked flask, and add 20 mL of water to the system at 60 min, 100 min, and 140 min of reaction to adjust the reaction degree. After the reaction is completed, reduce the temperature of the reaction gel to 50 °C, and then dry the reaction gel into powder by spray drying.

[0070] Comparative Example 1

[0071] (1) 4 g of sodium hydroxide and 15 g of anhydrous sodium carbonate were uniformly dissolved in 50 g of water to prepare an alkaline catalyst solution; 45 g of sodium metabisulfite was uniformly dissolved in 80 g of water to prepare a sulfonating agent solution;

[0072] (2) Under stirring conditions, 40 g of molten phenol, the prepared alkaline solution, 30 g of hydrolyzed polyacrylonitrile sodium salt ST-NaPAN powder, 80 g of formaldehyde solution, and the prepared sulfonating agent solution were slowly added to a three-necked flask in sequence. After adding 20 g of water, stirring was continued and the mixture was refluxed at 100°C for 3 h.

[0073] (3) Observe the change in the viscosity of the system in the three-necked flask, and add 20 mL of water to the system at 60 min, 100 min, and 140 min of reaction to adjust the reaction degree. After the reaction is completed, reduce the temperature of the reaction gel to 50 °C, and then dry the reaction gel into powder by spray drying.

[0074] Comparative Example 2

[0075] (1) 2 g of sodium hydroxide and 14 g of anhydrous sodium carbonate were uniformly dissolved in 50 g of water to prepare an alkaline catalyst solution; 38 g of sodium metabisulfite was uniformly dissolved in 80 g of water to prepare a sulfonating agent solution;

[0076] (2) Under stirring conditions, 40 g of molten phenol, the prepared alkaline solution, 15 g of 5A powder, 75 g of formaldehyde solution, and the prepared sulfonating agent solution were slowly added to a three-necked flask in sequence. After adding 20 g of water, stirring was continued and the mixture was refluxed at 105°C for 3 h.

[0077] (3) Observe the change in the viscosity of the system in the three-necked flask, and add 20 mL of water to the system at 60 min, 100 min, and 140 min of reaction to adjust the reaction degree. After the reaction is completed, reduce the temperature of the reaction gel to 50 °C, and then dry the reaction gel into powder by spray drying.

[0078] Comparative Example 3

[0079] (1) 2.5 g of sodium hydroxide and 16 g of anhydrous sodium carbonate were uniformly dissolved in 50 g of water to prepare an alkaline catalyst solution; 40 g of sodium metabisulfite was uniformly dissolved in 80 g of water to prepare a sulfonating agent solution;

[0080] (2) Under stirring conditions, 40 g of molten phenol, the prepared alkaline solution, 40 g of low molecular weight sulfonate polymer WH-Polymer powder, 90 g of formaldehyde solution and the prepared sulfonating agent solution were slowly added to a three-necked flask in sequence. After adding 20 g of water, stirring was continued and the mixture was refluxed at 95°C for 3 h.

[0081] (3) Observe the change in the viscosity of the system in the three-necked flask, and add 20 mL of water to the system at 60 min, 100 min, and 140 min of reaction to adjust the reaction degree. After the reaction is completed, reduce the temperature of the reaction gel to 50 °C, and then dry the reaction gel into powder by spray drying.

[0082] Comparative Example 4

[0083] The sample of comparative example 4 selected the SMP-Ⅰ product of Shandong Weifang Sanlibennuo Chemical Co., Ltd.

[0084] Comparative Example 5

[0085] The sample of comparative example 5 selected the SMP-Ⅱ product of Shandong Weifang Sanlibennuo Chemical Co., Ltd.

[0086] Comparative Example 6

[0087] The sample of comparative example 6 selected the SMP-Ⅱ product of Sichuan Zhengrong Industrial Co., Ltd.

[0088] Comparative Example 7

[0089] The sample of comparative example 7 selected the SMP-III product used in the field operation of Korla Oilfield in Xinjiang.

[0090] Test example

[0091] According to the Petroleum and Natural Gas Industry Standard of the People's Republic of China "SY / T5094-2017 Sulfomethylphenolic Resin SMP for Drilling Fluid Loss Reducer", the drilling fluid properties of the products of Examples 1-6 and Comparative Examples 1-7 were tested. The specific results are shown in Tables 1, 2 and 3.

[0092] Table 1 Technical indicators of the products of Examples 1-6 of the present invention

[0093]

[0094] Table 2 Performance evaluation results of products in Examples 1 to 6

[0095]

[0096] It can be seen from the data in Table 2 that the products of Examples 1-6 all have relatively low high-temperature and high-pressure fluid loss and have no obvious viscosity-increasing effect on the drilling fluid.

[0097] The polymer grafted modified sulfomethylphenolic resin products in Examples 1-6 have a medium-pressure filtration loss of less than 10 mL at room temperature and a high-pressure filtration loss of no more than 35 mL at high temperature, and have no obvious viscosity-increasing effect on drilling fluid mud, indicating that they have good filtration loss reduction effect.

[0098] Table 3 Performance evaluation results of products in comparative examples 1 to 5

[0099]

[0100] As shown in Figure 3, the high-temperature and high-pressure fluid loss of traditional sulfomethylphenolic resins (SMP-I and SMP-II) using phenol and formaldehyde as raw materials exceeds 100 mL at a 2.5% addition, far exceeding the required performance. This indicates that under these conditions, SMP-I and SMP-II have essentially lost their fluid loss performance.

[0101] As can be seen from Tables 2 and 3, the fluid loss reduction performance of the product of the present invention is better than that of SMP-I and SMP-II products on the market, and is comparable to that of SMP-III product used in oil fields.

[0102] The present invention has been described in detail above with reference to specific embodiments, exemplary examples, and accompanying drawings. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art will appreciate that various equivalent substitutions, modifications, or improvements may be made to the technical solutions and implementations of the present invention without departing from the spirit and scope of the present invention, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for preparing a polymer-grafted modified sulfomethylphenolic resin fluid loss additive, comprising the following steps: (1) Synthesis of polymer-grafted modified sulfomethylphenolic resin Add molten phenol to the reaction vessel, then slowly add a uniformly dissolved alkaline solution, water-soluble polymer powder, 37% formaldehyde solution and pre-dissolved sulfonating agent solution under stirring conditions, and reflux reaction; (2) Control of reaction degree During the reaction, water is added to the system every 30-80 minutes to adjust the reaction degree. After the reaction is completed, the temperature of the reaction gel is lowered to 50°C using circulating water, and then the reaction gel is dried into powder by spray drying.

2. The method according to claim 1, wherein In step (1), the polymer is a water-soluble high molecular weight drilling fluid temperature and salt resistance fluid loss reducer, such as one or more of hydrolyzed polyacrylonitrile salt, sodium polyacrylate, and sulfonate polymer, with a molecular weight of 3000-500,000.

3. The method according to claim 1, wherein In step (1), the amount of polymer powder added is calculated as a mass ratio of the polymer powder to phenol of (8-40):

80.

4. The method according to claim 1, wherein In step (1), the base is used as a catalyst, which is one or more of sodium hydroxide, potassium hydroxide or anhydrous sodium carbonate, and is prepared into an aqueous solution, preferably a 25% aqueous solution.

5. The method according to claim 1, wherein In step (1), the sulfonating agent used is one or more of sodium metabisulfite, anhydrous sodium sulfite and anhydrous sodium bisulfite, preferably prepared as a 40% aqueous solution for use.

6. The method according to claim 1, wherein In step (1), the mass ratio of the materials used is phenol: 37% formaldehyde solution: sulfonating agent is 80: (10-40): (140-190): (60-85); preferably, the mass ratio of phenol: 37% formaldehyde solution: sulfonating agent is 80: 160:

80.

7. The method according to claim 1, wherein In step (1), phenol, alkaline solution, polymer powder, 37% formaldehyde solution and sulfonating agent are refluxed at 90° C.-110° C. for 3-5 hours; preferably at 97° C.-100° C. for 3-4 hours.

8. The method according to claim 1, wherein In step (2), the mass ratio of the total amount of added water to phenol is (80-140):80; preferably 120:

80.

9. The method according to claim 1, wherein: In step (2), the time interval for adding water is 30 min-80 min, preferably 40-60 min.

10. A polymer grafted modified sulfomethylphenolic resin fluid loss additive, prepared by the method according to any one of claims 1 to 9.

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