Water-soluble anti-sloughing agent, preparation method thereof and water-based mud

Abstract

This invention discloses a water-soluble anti-collapse agent, its preparation method, and a water-based slurry. The raw materials for the water-soluble anti-collapse agent include melamine, formaldehyde aqueous solution, polyol, epichlorohydrin, water, initiator, organophosphonate, and comonomer. The preparation method includes the following steps: mixing melamine and formaldehyde aqueous solution, adjusting the pH, and then reacting; introducing polyol into the reaction system to continue the reaction; then introducing organophosphonate solution into the reaction system, followed by epichlorohydrin to continue the reaction; finally introducing comonomer and initiator to continue the reaction, and then drying and optionally crushing to obtain the water-soluble anti-collapse agent. A water-based slurry containing the above-mentioned water-soluble anti-collapse agent is also provided. The anti-collapse agent provided by this invention has a filtration loss reduction rate of more than 70% against complex salts and a shale secondary rolling recovery rate of more than 80%. It has good salt resistance, temperature resistance, wall consolidation, and filtration loss reduction performance, and also has the advantages of being environmentally friendly, having low fluorescence, and good water solubility.

Description

Technical Field

[0001] This invention belongs to the field of petroleum exploration technology, and relates to a drilling fluid additive and its preparation method, particularly to an anti-collapse agent and its preparation method. Background Technology

[0002] In drilling complex formations, wellbore leakage, collapse, borehole narrowing, and wellbore instability are major factors affecting the safe construction period. Increasing drilling fluid density has limited effect on maintaining wellbore stability and extending the safe construction period. High-performance anti-collapse wall-stabilizing agents are key to improving wellbore stability, reducing complex well conditions, and extending the safe construction period. Existing anti-collapse wall-stabilizing materials mainly include two categories: inhibitory anti-collapse agents and plugging anti-collapse agents. Inhibitors are mainly small molecule salts and polyamines, but while exerting a strong inhibitory effect, they also have a certain impact on drilling fluid stability. Plugging anti-collapse agents are mainly sulfonated asphalt materials. These materials are relatively mature, and sulfonated asphalt materials with high-temperature deformation, elastic plugging, and adhesive wall-stabilizing effects have good field application results. However, with increasingly stringent environmental regulations, the application of asphalt materials with dark color and poor environmental friendliness is gradually being restricted. There is an urgent need in the field for new environmentally friendly anti-collapse wall-stabilizing agents with similar anti-collapse wall-stabilizing effects to asphalt.

[0003] Existing research has focused on environmentally friendly anti-collapse and wall-stabilizing agents. Among related reports, CN111138594A reports a method for preparing an environmentally friendly, high-temperature resistant water-based drilling fluid plugging and anti-collapse agent. This method first involves thoroughly mixing styrene monomers, acrylic monomers, and emulsifiers to form a "pre-emulsion," followed by the addition of hydrophilic and cationic monomers for graft copolymerization. The resulting environmentally friendly anti-collapse agent has a core-shell structure, is non-toxic, environmentally friendly, and exhibits good high-temperature resistance. CN104151493A reports a method for preparing an emulsion-type anti-collapse agent. This method uses N-vinylpyrrolidone and (3-methacrylamido)propyltrimethylammonium chloride as raw materials, employing a reverse emulsion polymerization method to obtain the emulsion-type anti-collapse agent. The resulting product has a molecular weight of not less than 5 million, low monomer residual rate, and good stability. CN 109652031 A reports a strong wall-strengthening drilling fluid system and its preparation method. The method uses a strong cementing wall-strengthening material containing a polyethyleneimine structure as the main agent, combined with nano-plugging agent, wetting reversal agent, etc. to form a strong wall-strengthening drilling fluid system. No asphalt-based materials are used in the system, but it still achieves good effects of plugging and strengthening the wall and inhibiting clay hydration and expansion.

[0004] The aforementioned reports disclosed preparation and application methods for different types of environmentally friendly anti-collapse wall-stabilizing agents and drilling fluid systems. None of these methods used asphalt-based materials, but rather focused on material development from various angles, including inhibiting clay hydration and swelling, slowing down slurry formation and spalling, blocking hydration channels, mitigating pressure transmission, and maintaining wellbore stability. All methods achieved beneficial technical effects, meeting the wellbore stability and logging requirements during drilling and production in deep and complex wells. However, existing technologies pay less attention to the salt and calcium resistance properties of anti-collapse wall-stabilizing agents, and further research is needed on anti-collapse agents for high-temperature and high-salinity reservoirs.

[0005] Melamine resin, made from melamine and formaldehyde, is inexpensive and readily available. It exhibits stable performance, good film-forming properties, and excellent water resistance, and has already found mature applications in the coatings industry. In the oilfield chemicals sector, melamine resin, after water-soluble modification with sodium metabisulfite, has also been reported as an additive for oil well cement. However, overall, the application of water-soluble melamine resin in drilling and production processes is still largely unexplored. Developing water-soluble anti-collapse and wall-stabilizing agents using inexpensive and highly customizable melamine resin as a raw material holds great potential in terms of economy and applicability, and has broad application prospects. Summary of the Invention

[0006] This invention addresses the shortcomings of existing technologies, with the core objective of providing a novel water-soluble anti-collapse agent with melamine resin as its backbone, its preparation method, and water-based slurry. The anti-collapse agent has a temperature resistance of not less than 150℃, exhibits a filtration loss reduction rate of over 70% against complex salts (10wt% NaCl, 2wt% calcium chloride, and 5wt% magnesium chloride), and achieves a shale secondary rolling recovery rate of over 80%. It possesses excellent salt and temperature resistance, wall-solidifying properties, and filtration loss reduction, while also being environmentally friendly, low-fluorescence, and highly water-soluble.

[0007] The first aspect of this invention provides a water-soluble anti-collapse agent, wherein, based on parts by weight, the raw materials of the water-soluble anti-collapse agent include: 12 parts melamine, 24-40 parts formaldehyde aqueous solution, 6-18 parts polyol, 4.5-18.5 parts epichlorohydrin, 120-240 parts water, 0.09-0.8 parts initiator, 10-20 parts organophosphonate, and 5-20 parts comonomer.

[0008] More preferably, based on parts by weight, the raw materials for the water-soluble anti-collapse agent include: 12 parts melamine, 28-36 parts formaldehyde aqueous solution, 9-15 parts polyol, 9-13.5 parts epichlorohydrin, 150-200 parts water, 0.18-0.5 parts initiator, 12-16 parts organophosphonate, and 10-15 parts comonomer.

[0009] Furthermore, in the above-mentioned water-soluble anti-collapse agent, the polyol is any one or more of ethylene glycol, propylene glycol, and glycerol.

[0010] Furthermore, in the above-mentioned water-soluble anti-collapse agent, the mass concentration of the formaldehyde aqueous solution is 30wt% to 55wt%, preferably an industrial-grade formaldehyde aqueous solution with a mass concentration of 37%, 44%, or 50%.

[0011] Furthermore, in the above-mentioned water-soluble anti-collapse agent, the initiator is any one or more of potassium persulfate, sodium persulfate, and ammonium persulfate.

[0012] Furthermore, in the above-mentioned water-soluble anti-collapse agent, the comonomer is one or more of acrylamide (AM), 2-methyl-2-acryloylaminopropanesulfonic acid (AMPS), acrylic acid (AA), fumaric acid (FA), sodium allyl sulfonate (SSS), and sodium 2-acryloyloxyisopentene sulfonate (AOIAS).

[0013] Furthermore, in the aforementioned water-soluble anti-collapse agent, the organophosphonate is diallylaminomethylphosphonate, with the molecular formula C7H. 12 NO3, PM2.5 and / or C7H 12 NO3PN, (C7H) 12 NO3P)3X2、(C7H 12 NO3P)2Y, M is one or more monovalent metals, N is one or more divalent metals, X is one or more trivalent metals, and Y is one or more tetravalent metals; preferably, it is one or more of sodium diallylaminomethylphosphonate, potassium diallylaminomethylphosphonate, magnesium diallylaminomethylphosphonate, and calcium diallylaminomethylphosphonate.

[0014] A second aspect of the present invention provides a method for preparing a water-soluble anti-collapse agent, comprising the following steps:

[0015] S1: Mix melamine and formaldehyde aqueous solution, add alkaline solution to adjust pH to 8-9, and then carry out the reaction at the first reaction temperature;

[0016] S2: Adjust the temperature of the reaction system to the second reaction temperature, and introduce a polyol into the reaction system to continue the reaction;

[0017] S3: Under mixed conditions, an organophosphonate solution is introduced into the reaction system, and then epichlorohydrin is added to carry out the reaction at the second reaction temperature;

[0018] S4: Introduce a comonomer into the reaction system, adjust the temperature of the reaction system to the third reaction temperature, add an initiator to carry out the reaction, and then obtain a water-soluble anti-collapse agent after drying and optional crushing treatment.

[0019] Furthermore, in the above-mentioned method for preparing the water-soluble anti-collapse agent, the alkaline solution in step S1 is an inorganic alkaline solution, specifically at least one of sodium hydroxide solution and potassium hydroxide solution.

[0020] Furthermore, in the above-mentioned method for preparing the water-soluble anti-collapse agent, the first reaction temperature in step S1 is 70-90°C, and the reaction time is 0.5-6h.

[0021] Furthermore, in the above-mentioned method for preparing the water-soluble anti-collapse agent, the mass concentration of the formaldehyde aqueous solution in step S1 is 30wt% to 55wt%, preferably an industrial-grade formaldehyde aqueous solution with a mass concentration of 37%, 44%, or 50%.

[0022] Furthermore, in the above-mentioned method for preparing the water-soluble anti-collapse agent, the second reaction temperature in step S2 is 40-60°C, and the reaction time is 0.5-6h.

[0023] Furthermore, in the above-mentioned method for preparing the water-soluble anti-collapse agent, the polyol in step S2 is any one or more of ethylene glycol, propylene glycol, and glycerol.

[0024] Furthermore, in the above-mentioned method for preparing the water-soluble anti-collapse agent, the epichlorohydrin in step S3 is introduced into the reaction system by slow addition, specifically by dropwise addition.

[0025] Furthermore, in the above-mentioned method for preparing the water-soluble anti-collapse agent, the reaction time in step S3 is 0.5 to 4 hours.

[0026] Furthermore, in the above-mentioned method for preparing the water-soluble anti-collapse agent, the organophosphonate in step S3 is diallylaminomethylphosphonate, with the molecular formula C7H. 12 NO3PM2, C7H 12 NO3PN, (C7H) 12 NO3P)3X2、(C7H 12 NO3P)2Y, M is one or more monovalent metals, N is one or more divalent metals, X is one or more trivalent metals, and Y is one or more tetravalent metals; preferably, it is one or more of sodium diallylaminomethylphosphonate, potassium diallylaminomethylphosphonate, magnesium diallylaminomethylphosphonate, and calcium diallylaminomethylphosphonate.

[0027] Furthermore, in the above-mentioned method for preparing the water-soluble anti-collapse agent, the organophosphonate solution in step S3 is obtained by mixing organophosphonate with water until homogeneous.

[0028] Furthermore, in the above-mentioned method for preparing the water-soluble anti-collapse agent, the comonomer in step S4 is one or more of acrylamide (AM), 2-methyl-2-acryloylaminopropanesulfonic acid (AMPS), acrylic acid (AA), fumaric acid (FA), sodium allyl sulfonate (SSS), and sodium 2-acryloyloxyisoprene sulfonate (AOIAS).

[0029] Furthermore, in the above-mentioned method for preparing the water-soluble anti-collapse agent, the third reaction temperature in step S4 is 60-80℃, and the reaction time is 1-6h.

[0030] Furthermore, in the above-mentioned method for preparing the water-soluble anti-collapse agent, the initiator in step S4 is any one or more of potassium persulfate, sodium persulfate, and ammonium persulfate.

[0031] Furthermore, in the above-mentioned method for preparing the water-soluble anti-collapse agent, the drying conditions in step S4 are as follows: drying temperature is 105-120℃, and drying time is 12-48h.

[0032] Furthermore, in the above-mentioned method for preparing the water-soluble anti-collapse agent, the amounts of melamine, formaldehyde aqueous solution, polyol, epichlorohydrin, water, initiator, organophosphonate, and comonomer, based on weight parts, are as follows: 12 parts melamine, 24-40 parts formaldehyde aqueous solution, 6-18 parts polyol, 4.5-18.5 parts epichlorohydrin, 120-240 parts water, 0.09-0.8 parts initiator, 10-20 parts organophosphonate, and 5-20 parts comonomer; preferably, the amounts are 12 parts melamine, 28-36 parts formaldehyde aqueous solution, 9-15 parts polyol, 9-13.5 parts epichlorohydrin, 150-200 parts water, 0.18-0.5 parts initiator, 12-16 parts organophosphonate, and 10-15 parts comonomer.

[0033] Furthermore, in the above-mentioned method for preparing the water-soluble anti-collapse agent, the crushing process in step S4 can be carried out using any existing method that can crush solid materials, without any special restrictions.

[0034] A third aspect of the present invention provides a water-soluble anti-collapse agent obtained by the above preparation method.

[0035] A fourth aspect of the present invention provides a water-based mud, the water-based mud comprising the above-mentioned water-soluble anti-collapse agent or a water-soluble anti-collapse agent obtained by the above preparation method; further, the amount of water-soluble anti-collapse agent is 0.5wt% to 5wt% of the total weight of the water-based mud.

[0036] The water-soluble anti-collapse agent provided by this invention can play a good role in preventing collapse, consolidating the wall and reducing filtration loss when added at a dosage of 0.5-5wt%. It has good salt resistance and temperature resistance, low cost, low fluorescence effect, and does not affect logging. It is suitable for use in drilling and production of deep wells, high-salt formations and other complex wells. It has a good effect of sealing and consolidating the wall, blocking the hydration channel, slowing down the pressure transmission effect, and extending the safe construction period.

[0037] Compared with the prior art, the water-soluble anti-collapse agent and its preparation method provided by the present invention have the following advantages:

[0038] 1. The water-soluble anti-collapse agent of this invention has a temperature resistance of not less than 150℃, a filtration loss reduction rate of more than 70% against compound salts (NaCl content 10wt%, calcium chloride content 2wt%, magnesium chloride content 5wt%), and a secondary rolling recovery rate of more than 80% for shale. It has good performance in salt resistance, temperature resistance, wall solidification and filtration loss reduction, and also has the advantages of being environmentally friendly, low fluorescence and good water solubility. It can meet the requirements of water-based mud anti-collapse and wall solidification in complex well conditions such as deep wells and high-salt brine wells, and extend the safe construction period.

[0039] 2. In the preparation method of the water-soluble anti-collapse agent of the present invention, a melamine resin skeleton with water-phase dispersibility is first constructed by hydroxymethylation reaction and condensation reaction of melamine and formaldehyde. In the later stage of the reaction, a polyol is added to participate in the condensation reaction to form ether bonds, which protects the hydroxymethyl groups and avoids deep condensation of primary / secondary amines with hydroxymethyl groups. This makes the molecular weight of the melamine resin skeleton suitable and controllable, and further increases the water solubility of the melamine resin.

[0040] 3. In the preparation method of the water-soluble anti-collapse agent of the present invention, phosphonic acid groups and double bond structures are introduced into the melamine resin skeleton structure through crosslinking, and further grafted with hydrated monomers through free radical polymerization, resulting in an amphiphilic melamine resin anti-collapse agent with the melamine resin skeleton as the core and hydrophilic molecular chains as the arms. The phosphonic acid groups in the structural unit can complex with metal cations of different valence states, significantly improving the resistance to salt and dehydration. Meanwhile, the synthesis method of diallylaminomethylphosphonate containing acidic structural units is green and environmentally friendly, with low energy consumption, high product purity, and high yield, which is beneficial for industrial production and application.

[0041] 4. The preparation method of the water-soluble anti-collapse agent of the present invention integrates hydroxymethylation, etherification, crosslinking and free radical polymerization reactions in an orderly manner. The reaction conditions are generally simple and controllable, and the raw materials used are widely available and inexpensive, which is conducive to the production and industrial application of the technical method. Attached Figure Description

[0042] Figure 1 This is a scanning electron microscope image of the anti-collapse agent obtained in Example 5 of the present invention. Detailed Implementation

[0043] The following specific embodiments further describe the melamine resin-based water-soluble anti-collapse agent and its preparation method involved in the present invention, but do not constitute a limitation on the present invention.

[0044] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values ​​stated herein, and such ranges or values ​​should be understood to include values ​​close to such ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0045] All material ratios appearing in the following examples and comparative examples are mass fractions of the materials.

[0046] In this paper, electron micrographs of the anti-collapse agent were taken using a JEOL JEM-7500F scanning electron microscope with an accelerating voltage of 5 kV.

[0047] More preferably, the preparation method of diallylaminomethylphosphonate in this article includes the following steps:

[0048] (1) Mix the organic solvent and phosphorous acid, and then adjust the pH of the reaction system to be no greater than 7, preferably 1-6.8, more preferably 1-4, and even more preferably 1-3; the organic solvent can be one or more of alcohols, esters, ethers, and ketones; further, the number of carbon atoms of the alcohol, ester, ether, and ketone can be 1-12, specifically selected from one or more of methanol, ethanol, butanol, ethyl acetate, butyl acetate, isoamyl acetate, diethyl ether, butyl ether, acetone, and methyl ethyl ketone; the volume ratio of organic solvent to phosphorous acid is 1-1:1-15, preferably 1-2:1-8;

[0049] (2) Slowly add diallylamine to the reaction system of step (1) and react at a temperature of -20°C to 10°C, preferably -10°C to 5°C;

[0050] (3) Slowly add aldehyde to the system after step (2) to carry out the reaction. The reaction temperature is -20℃ to 10℃, preferably -10℃ to 5℃. The aldehyde can be one or more of formaldehyde, dioxyformaldehyde, trioxyformaldehyde, and paraoxyformaldehyde, preferably formaldehyde.

[0051] (4) Adjust the pH value of the system after the reaction in step (3) to 6-8, and continue the reaction. The reaction temperature is 0-90℃, preferably 20-40℃; the reaction time is 0.5-6h, preferably 1-3h; the reaction product is further separated, and the solid phase obtained by separation is dried to obtain the product.

[0052] Furthermore, in the above preparation method, the pH value of the reaction system in step (1) can be adjusted by adding an acidic substance. The acidic substance is preferably an inorganic acid and / or an organic acid, specifically selected from one or more of hydrochloric acid, sulfuric acid, nitric acid, oxalic acid, glacial acetic acid, carbonic acid, hydrofluoric acid, citric acid, malic acid, tartaric acid, succinic acid, etc.

[0053] Furthermore, in the above preparation method, the slow addition of diallylamine in step (2) can be done by dripping, and more preferably at a rate of 10 mL / h to 200 mL / h.

[0054] Furthermore, in the above preparation method, the aldehyde in step (3) is preferably added in liquid form. For example, when formaldehyde is used, it can be added directly in liquid form; when dioxymethylene, trioxymethylene, or paraoxymethylene is used, it can be dissolved in an organic solvent first and then added in liquid form. The organic solvent used can be one or more of alcohols, esters, ethers, and ketones. Furthermore, the number of carbon atoms of the alcohol, ester, ether, or ketone can be 1 to 12, and can be specifically selected from one or more of methanol, ethanol, butanol, ethyl acetate, butyl acetate, isoamyl acetate, diethyl ether, butyl ether, acetone, and methyl ethyl ketone.

[0055] Furthermore, in the above preparation method, the slow addition of aldehyde in step (3) can be done by dripping, and more preferably by dripping at a rate of 10 mL / h to 200 mL / h.

[0056] Furthermore, in the above preparation method, the pH value of the system in step (4) can be adjusted to 6-8 by adding an alkaline substance. The alkaline substance can be an inorganic base and / or an alkaline inorganic salt. The metal in the inorganic base and / or alkaline inorganic salt is selected from one or more monovalent, divalent, trivalent, and tetravalent metal elements. More specifically, it can be selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, magnesium hydroxide, magnesium carbonate, calcium carbonate, calcium hydroxide, iron hydroxide, copper hydroxide, titanium hydroxide, zirconium hydroxide, etc. Preferably, sodium hydroxide, potassium hydroxide, magnesium hydroxide, and calcium hydroxide are selected.

[0057] In the above preparation method, the separation in step (4) is solid-liquid separation. The solid-liquid separation can be achieved by any means that can separate the solid and liquid phases. The selection of such liquid-solid separation means is a basic skill that must be possessed by those skilled in the art. It can be reasonably selected according to the actual situation. Specifically, one or more of the following methods can be used: filtration separation, centrifugal separation, etc.

[0058] Furthermore, in the above preparation method, the liquid phase separated in step (4) can be recycled back to step (1) for continued use, and the reaction can continue after supplementing other raw materials.

[0059] Furthermore, in the above preparation method, the drying temperature in step (4) is 60-120℃ and the drying time is 6-12h.

[0060] Furthermore, in the above preparation method, the molar ratio of diallylamine, phosphorous acid, and aldehyde is diallylamine:phosphorous acid:aldehyde = 1:(1-2):(1-2), preferably 1:1-1.5:1-1.5.

[0061] Example 1

[0062] Add 5.7 g of phosphorous acid and 7 mL of anhydrous ethanol to the reaction vessel, then add 2 mL of concentrated sulfuric acid (98 wt%) to adjust the pH of the system to 1. Place the reaction vessel in an ice-water bath and add 8.6 mL of diallylamine dropwise through a constant dropping funnel, controlling the addition to be completed within 45 min. After the addition is completed, continue the reaction under reflux for 2 h. Then, add a mixture of 12.6 g of paraformaldehyde and 7 mL of anhydrous ethanol dropwise through a constant dropping funnel, controlling the addition to be completed within 20 min. After the addition is completed, continue the reaction under reflux for 3 h. Then, add 5.6 g of NaOH to the system to adjust the pH of the system to 7, and react at 20 °C for 1 h. After further centrifugation, the obtained solid phase material is further dried at 80 °C for 10 h to obtain the target product A, with a yield of 91.1% and a product purity of 98.5%.

[0063] Example 2

[0064] 5.7 g of phosphorous acid and 7 mL of methanol were added to the reaction vessel, followed by 7 mL of oxalic acid to adjust the pH to 2. The reaction vessel was then placed in an ice-water bath, and 8.6 mL of diallylamine was added dropwise through a constant dropping funnel, completing the addition within 45 min. After the addition was complete, the reaction was refluxed for 2 h. Subsequently, a mixture of 6.3 g of paraformaldehyde and 3.5 mL of methanol was added dropwise through a constant dropping funnel, completing the addition within 10 min. After the addition was complete, the reaction was refluxed for 1.5 h. Then, 5.6 g of NaOH was added to the system to adjust the pH to 7, and the reaction was carried out at 20 °C for 2 h. After further centrifugation, the obtained solid phase was dried at 80 °C for 10 h to obtain the target product B, with a yield of 90.2% and a purity of 97.9%.

[0065] Example 3

[0066] 11.4 g of phosphorous acid and 7 mL of anhydrous ethanol were added sequentially to the reaction vessel. Then, 7 mL of concentrated sulfuric acid was added to adjust the pH of the system to 1. The reaction vessel was then placed in an ice-water bath, and 8.6 mL of diallylamine was added dropwise through a constant dropping funnel, with the addition completed within 45 min. After the addition was completed, the reaction was refluxed for 2.5 h. Subsequently, a mixture of 6.3 g of paraformaldehyde and 7 mL of anhydrous ethanol was added dropwise through a constant dropping funnel, with the addition completed within 10 min. After the addition was completed, the reaction was refluxed for 1.5 h. Then, 5.6 g of KOH was added to the system to adjust the pH to 7, and the reaction was carried out at 20 °C for 2.5 h. After further centrifugation, the obtained solid phase was dried at 80 °C for 10 h to obtain the target product C, with a yield of 90.0% and a purity of 98.2%.

[0067] Example 4

[0068] 11.4 g of phosphorous acid and 7 mL of butanol were added sequentially to the reaction vessel. Then, 7 mL of glacial acetic acid was added to adjust the pH to 2. The reaction vessel was then placed in an ice-water bath, and 8.6 mL of diallylamine was added dropwise through a constant-drop funnel over 45 minutes. After the addition was complete, the reaction was refluxed for 2.5 h. Subsequently, a mixture of 12.6 g of paraformaldehyde and 7 mL of butanol was added dropwise through a constant-drop funnel over 10 minutes. After the addition was complete, the reaction was refluxed for 1.5 h. Then, 5.6 g of NaOH was added to adjust the pH to 7, and the reaction was carried out at 20 °C for 2.5 h. After further centrifugation, the resulting solid phase was dried at 80 °C for 10 h to obtain the target product D, with a yield of 90.2% and a purity of 98.1%.

[0069] Example 5

[0070] Add 12 parts of melamine to 30 parts of formaldehyde aqueous solution (44 wt%), stir thoroughly, adjust the pH of the system to 8.5 with sodium hydroxide, heat to 80℃ and keep the reaction at that temperature for 3.5 h, maintaining the pH of the system at 8-9 during this period. Cool down to 55℃, add 12 parts of ethylene glycol to the system, and continue the reaction for 4 h. Weigh 15 parts of phosphonic acid monomer A and add it to 185 parts of water to prepare a solution, add it to the reaction system, stir thoroughly, then weigh 10 parts of epichlorohydrin and add it dropwise. After the addition is complete, stir the reaction at the same temperature for 2.5 h. Add 12 parts of comonomer (AA:AMPS=4:1) to the system, stir thoroughly, heat to 68℃, add 0.36 parts of potassium persulfate, react for 3.5 h, discharge the material, dry at 115℃ for 36 h, and pulverize to obtain a white melamine resin-based water-soluble anti-collapse agent a. The scanning electron microscope image of anti-collapse agent a is shown in [image missing]. Figure 1 .

[0071] Example 6

[0072] Add 12 parts of melamine to 40 parts of formaldehyde aqueous solution (mass concentration of 55 wt%), stir thoroughly, adjust the pH of the system to 9 with potassium hydroxide, heat to 90℃ and maintain the reaction temperature for 0.5 h, during which time the pH of the system is maintained at 8-9. Cool down to 60℃, add 18 parts of propylene glycol to the system, and continue the reaction for 6 h. Weigh 20 parts of phosphonic acid monomer B and add it to 240 parts of water to prepare a solution, add it to the reaction system, stir thoroughly, then weigh 18.5 parts of epichlorohydrin and add it dropwise. After the addition is complete, stir the reaction for 0.5 h under the same temperature conditions. Add 20 parts of AM to the system, stir thoroughly, heat to 80℃, add 0.8 parts of ammonium persulfate, react for 1 h, discharge the material, dry at 120℃ for 12 h, and then pulverize to obtain white melamine resin-based water-soluble anti-collapse agent b.

[0073] Example 7

[0074] Add 12 parts of melamine to 24 parts of formaldehyde aqueous solution (mass concentration 37 wt%), stir thoroughly, adjust the pH of the system to 8 with sodium hydroxide, heat to 70℃ and maintain the reaction temperature for 6 hours, during which time the pH of the system is maintained at 8-9. Cool down to 40℃, add 6 parts of glycerol to the system, and continue the reaction for 0.5 hours. Weigh 10 parts of phosphonic acid monomer C and add it to 120 parts of water to prepare a solution, add it to the reaction system, stir thoroughly, then weigh 4.5 parts of epichlorohydrin and add it dropwise. After the addition is complete, stir the reaction at the same temperature for 6 hours. Add 5 parts of comonomer AMPS to the system, stir thoroughly, heat to 60℃, add 0.09 parts of potassium persulfate, react for 6 hours, discharge the material, dry at 105℃ for 48 hours, and then pulverize to obtain white melamine resin-based water-soluble anti-collapse agent C.

[0075] Example 8

[0076] Add 12 parts of melamine to 36 parts of formaldehyde aqueous solution (mass concentration 50 wt%), stir thoroughly, adjust the pH of the system to 8.8 with sodium hydroxide, heat to 85℃ and maintain the reaction for 1.5 h, during which time the pH of the system is maintained at 8-9. Cool down to 57℃, add 15 parts of polyol (ethylene glycol: propylene glycol = 1:1) to the system, and continue the reaction for 1 h. Weigh 16 parts of phosphonic acid monomer D, add it to 200 parts of water to prepare a solution, add it to the reaction system, stir thoroughly, then weigh 13.5 parts of epichlorohydrin and add it dropwise. After the addition is complete, stir the reaction for 1.5 h under the same temperature conditions. Add 15 parts of comonomer AOIAS to the system, stir thoroughly, heat to 76℃, add 0.5 parts of sodium persulfate, react for 2 h, discharge the material, dry at 118℃ for 15 h, and then pulverize to obtain white melamine resin-based water-soluble anti-collapse agent d.

[0077] Example 9

[0078] Add 12 parts of melamine to 28 parts of formaldehyde aqueous solution (mass concentration 37wt%), stir thoroughly, adjust the pH of the system to 8.2 with sodium hydroxide, heat to 74℃ and maintain the reaction for 4.5h, during which the pH of the system is maintained at 8-9. Cool down to 46℃, add 9 parts of polyol (ethylene glycol: glycerol = 2:1) to the system, and continue the reaction for 5.5h. Weigh 12 parts of phosphonic acid monomer A, add it to 150 parts of water to prepare a solution, add it to the reaction system, stir thoroughly, then weigh 9 parts of epichlorohydrin and add it dropwise. After the addition is complete, stir the reaction for 4h under the same temperature conditions. Add 10 parts of comonomer FA to the system, stir thoroughly, heat to 63℃, add 0.18 parts of initiator (potassium persulfate: ammonium persulfate = 1:1), react for 5h, discharge the material, dry at 107℃ for 26h, and then pulverize to obtain white melamine resin-based water-soluble anti-collapse agent e.

[0079] Comparative Example 1

[0080] Add 12 parts of melamine to 30 parts of formaldehyde aqueous solution (44 wt%), stir thoroughly, adjust the pH of the system to 8.5 with sodium hydroxide, heat to 80℃ and maintain the reaction for 3.5 h, during which time the pH of the system is maintained at 8-9. Cool down to 55℃, add 12 parts of ethylene glycol to the system, and continue the reaction for 4 h. Weigh 10 parts of epichlorohydrin and add it dropwise, and after the addition is complete, stir the reaction for 2.5 h under the same temperature conditions. Add 12 parts of comonomer (AA:AMPS=4:1) to the system, stir thoroughly, heat to 68℃, add 0.36 parts of potassium persulfate, react for 3.5 h, discharge the material, dry at 115℃ for 36 h, and then pulverize to obtain a white melamine resin-based water-soluble anti-collapse agent f.

[0081] Comparative Example 2

[0082] Add 12 parts of melamine to 30 parts of formaldehyde aqueous solution (mass concentration 44 wt%), stir thoroughly, adjust the pH of the system to 8.5 with sodium hydroxide, heat to 80℃ and keep the reaction at that temperature for 3.5 h, maintaining the pH of the system at 8-9 during this period. Cool down to 55℃, add 12 parts of ethylene glycol to the system, and continue the reaction for 4 h. Weigh 15 parts of phosphonic acid monomer A and add it to 185 parts of water to prepare a solution, add it to the reaction system, stir thoroughly, and stir the reaction at the same temperature for 2.5 h. Add 12 parts of comonomer (AA:AMPS=4:1) to the system, stir thoroughly, heat to 68℃, add 0.36 parts of potassium persulfate, react for 3.5 h, discharge the material, dry at 115℃ for 36 h, and pulverize to obtain g of white melamine resin-based water-soluble anti-collapse agent.

[0083] Comparative Example 3

[0084] Add 12 parts of melamine to 30 parts of formaldehyde aqueous solution (mass concentration 44 wt%), stir thoroughly, adjust the pH of the system to 8.5 with sodium hydroxide, heat to 80℃ and keep the reaction at this temperature for 3.5 h, maintaining the pH of the system at 8-9 during this period. Cool down to 55℃ and continue the reaction for 4 h. Weigh 15 parts of phosphonic acid monomer A and add it to 185 parts of water to prepare a solution, add it to the reaction system, stir thoroughly, then weigh 10 parts of epichlorohydrin and add it dropwise. After the addition is complete, stir the reaction at the same temperature for 2.5 h. Add 12 parts of comonomer (AA:AMPS=4:1) to the system, stir thoroughly, heat to 68℃, add 0.36 parts of potassium persulfate, react for 3.5 h, discharge the material, dry at 115℃ for 36 h, and then pulverize to obtain a white melamine resin-based water-soluble anti-collapse agent.

[0085] Performance testing

[0086] 1. Temperature and salt resistance test

[0087] The performance of the anti-collapse agents for drilling fluids obtained in Examples 5-9 and Comparative Examples 1-3 was evaluated using a medium-temperature, medium-pressure filtration analyzer. Experimental apparatus: medium-temperature, medium-pressure filtration analyzer, stirrer, settling vessel, roller furnace. Experimental materials: prepared drilling fluids, samples obtained in Examples 5-9, and samples obtained in Comparative Examples 1-3.

[0088] Experimental steps:

[0089] Add 400mL of distilled water to a high-speed stirring cup, then add 40g of sodium chloride, 8g of calcium chloride, and 20g of magnesium chloride. After dissolving under stirring, slowly add 60g of bentonite for drilling fluid test slurry preparation and 3.6g of sodium carbonate (accurate to 0.01g) while stirring at (11000±300)r / min. Stir at high speed for 20min, and then cure in a sealed container at room temperature for 24h to obtain the composite brine-based slurry. Prepare two slurries in total.

[0090] Take two 400 mL portions of the above base slurry, add 12.0 g of sample (3 wt%) to one portion, stir at high speed for 20 min at (11000±300) r / min, pour into an aging tank, place in a high-temperature roller furnace and roll at 150℃ for 16 h, then remove, cool to room temperature, stir at high speed for 5 min, and determine the medium-pressure filtration loss according to the provisions of GB / T 16783.1. Calculate the filtration loss reduction rate according to formula (1).

[0091] (1)

[0092] In the formula:

[0093] ƒ —Reduction rate of filtration loss, %

[0094] FL 0 —Filtration loss of the base slurry, mL;

[0095] FL — Sample loss due to filtration, mL.

[0096] Experimental results:

[0097] The reduction rate of drilling fluid filtration loss was evaluated 30 minutes after the start of the experiment. The experimental results are shown in Table 1.

[0098] Table 1 Evaluation of Filtration Loss

[0099]

[0100] 2. Anti-collapse and wall-stabilizing performance test

[0101] The base slurry was prepared according to the method in the temperature and salt resistance test. Shale was dried at 105℃±3℃ and cooled to room temperature (25℃). 50.00g (accurate to 0.01g) of shale particles M0 were weighed and added to 350g of the prepared base slurry. Then, 4wt% of samples from Examples 5-9 or Comparative Examples 1-3 were added to the base slurry, and the mixture was thoroughly stirred before being placed in a settling tank. The settling tank was placed in a 150℃ hot rolling furnace for 16 hours. After the hot rolling was completed, the shale particles were removed and cooled. The shale particles were recovered using 5-mesh and 10-mesh sieves. After drying at 105℃±3℃ and cooling to room temperature, the primary shale recovery mass M1 was obtained. The primary recovered shale was then placed in clean water and placed in a hot rolling tank, and hot rolled at 150℃ for 2 hours. After removal, it was dried, recovered, and weighed using the same method to obtain the secondary shale recovery mass M2.

[0102] Then, calculate the primary shale rolling recovery rate R1 = M1 / M0 × 100% and the secondary shale rolling recovery rate R2 = M2 / M1 × 100%.

[0103] Table 2 Evaluation of Shale Rolling Recovery Rate

[0104]

[0105] As shown in Tables 1 and 2, the anti-collapse agents prepared using Examples 5-9 have a significant effect on reducing filtration loss, with a filtration loss reduction rate of over 75%, and also have a good anti-collapse and wall-stabilizing effect, with a shale secondary rolling recovery rate of over 80%. In contrast, the samples prepared using Comparative Examples 1-3 do not have good anti-collapse and wall-stabilizing capabilities or filtration loss reduction capabilities, with a filtration loss reduction rate of less than 45% and a secondary shale rolling recovery rate of less than 40%.

Claims

1. A water-soluble anti-collapse agent, wherein, based on parts by weight, the raw materials of the water-soluble anti-collapse agent include: The composition comprises 12 parts melamine, 24-40 parts formaldehyde aqueous solution, 6-18 parts polyol, 4.5-18.5 parts epichlorohydrin, 120-240 parts water, 0.09-0.8 parts initiator, 10-20 parts organophosphonate, and 5-20 parts comonomer, wherein the comonomer is one or more of acrylamide, 2-methyl-2-acryloylaminopropanesulfonic acid, acrylic acid, fumaric acid, sodium allyl sulfonate, and sodium 2-acryloyloxyisoprene sulfonate, and the organophosphonate is diallylaminomethylphosphonate. The preparation method of water-soluble anti-collapse agent includes the following steps: S1: Mix melamine and formaldehyde aqueous solution, add alkaline solution to adjust pH to 8-9, and then carry out the reaction at the first reaction temperature; S2: Adjust the temperature of the reaction system to the second reaction temperature, and introduce a polyol into the reaction system to continue the reaction; S3: Under mixed conditions, an organophosphonate solution is introduced into the reaction system, and then epichlorohydrin is added to carry out the reaction at the second reaction temperature; S4: Introduce a comonomer into the reaction system, adjust the temperature of the reaction system to the third reaction temperature, add an initiator to carry out the reaction, and then obtain a water-soluble anti-collapse agent after drying and optional crushing treatment.

2. The water-soluble anti-collapse agent according to claim 1, wherein, Based on parts by weight, the raw materials for the water-soluble anti-collapse agent include: 12 parts melamine, 28-36 parts formaldehyde aqueous solution, 9-15 parts polyol, 9-13.5 parts epichlorohydrin, 150-200 parts water, 0.18-0.5 parts initiator, 12-16 parts organophosphonate, and 10-15 parts comonomer.

3. The water-soluble anti-collapse agent according to claim 1, wherein, The polyol is any one or more of ethylene glycol, propylene glycol, and glycerol.

4. The water-soluble anti-collapse agent according to claim 1, wherein, The mass concentration of formaldehyde aqueous solution is 30wt% to 55wt%.

5. The water-soluble anti-collapse agent according to claim 1, wherein, The initiator is any one or more of potassium persulfate, sodium persulfate, and ammonium persulfate.

6. The water-soluble anti-collapse agent according to claim 1, wherein, Diallylaminomethylphosphonate has the molecular formula C7H. 12 NO3, PM2.5 and / or C7H 12 NO3PN, (C7H) 12 NO3P)3X2、(C7H 12 NO3P)2Y, where M is one or more monovalent metals, N is one or more divalent metals, X is one or more trivalent metals, and Y is one or more tetravalent metals.

7. The water-soluble anti-collapse agent according to claim 1, wherein, Diallylaminomethylphosphonate is one or more of sodium diallylaminomethylphosphonate, potassium diallylaminomethylphosphonate, magnesium diallylaminomethylphosphonate, and calcium diallylaminomethylphosphonate.

8. A method for preparing the water-soluble anti-collapse agent according to any one of claims 1-7, comprising the following steps: S1: Mix melamine and formaldehyde aqueous solution, add alkaline solution to adjust pH to 8-9, and then carry out the reaction at the first reaction temperature; S2: Adjust the temperature of the reaction system to the second reaction temperature, and introduce a polyol into the reaction system to continue the reaction; S3: Under mixed conditions, an organophosphonate solution is introduced into the reaction system, and then epichlorohydrin is added to carry out the reaction at the second reaction temperature; S4: Introduce a comonomer into the reaction system, adjust the temperature of the reaction system to the third reaction temperature, add an initiator to carry out the reaction, and then obtain a water-soluble anti-collapse agent after drying and optional crushing treatment.

9. The method for preparing the water-soluble anti-collapse agent according to claim 8, wherein, The alkaline solution in step S1 is an inorganic alkaline solution, which is at least one of sodium hydroxide solution and potassium hydroxide solution.

10. The method for preparing the water-soluble anti-collapse agent according to claim 8, wherein, The first reaction temperature in step S1 is 70–90°C, and the reaction time is 0.5–6 h.

11. The method for preparing the water-soluble anti-collapse agent according to claim 8, wherein, The mass concentration of the formaldehyde aqueous solution in step S1 is 30wt% to 55wt%.

12. The method for preparing the water-soluble anti-collapse agent according to claim 8, wherein, The second reaction temperature in step S2 is 40–60°C, and the reaction time is 0.5–6 h.

13. The method for preparing the water-soluble anti-collapse agent according to claim 8, wherein, The polyol in step S2 is any one or more of ethylene glycol, propylene glycol, and glycerol.

14. The method for preparing the water-soluble anti-collapse agent according to claim 8, wherein, The organophosphonate in step S3 is diallylaminomethylphosphonate, with the molecular formula C7H. 12 NO3PM2, C7H 12 NO3PN, (C7H) 12 NO3P)3X2、(C7H 12 NO3P)2Y, where M is one or more monovalent metals, N is one or more divalent metals, X is one or more trivalent metals, and Y is one or more tetravalent metals.

15. The method for preparing the water-soluble anti-collapse agent according to claim 8 or 14, wherein, The organophosphonate in step S3 is one or more of sodium diallylaminomethylphosphonate, potassium diallylaminomethylphosphonate, magnesium diallylaminomethylphosphonate, and calcium diallylaminomethylphosphonate.

16. The method for preparing the water-soluble anti-collapse agent according to claim 8, wherein, The comonomer in step S4 is one or more of acrylamide, 2-methyl-2-acryloylaminopropanesulfonic acid, acrylic acid, fumaric acid, sodium allyl sulfonate, and sodium 2-acryloyloxyisopentene sulfonate.

17. The method for preparing the water-soluble anti-collapse agent according to claim 8, wherein, The third reaction temperature in step S4 is 60–80°C, and the reaction time is 1–6 h.

18. The method for preparing the water-soluble anti-collapse agent according to claim 8, wherein, The initiator in step S4 is any one or more of potassium persulfate, sodium persulfate, and ammonium persulfate.

19. The method for preparing the water-soluble anti-collapse agent according to claim 8, wherein, The drying conditions in step S4 are as follows: drying temperature is 105-120℃, and drying time is 12-48h.

20. The method for preparing the water-soluble anti-collapse agent according to claim 8, wherein, Based on parts by weight, the amounts of melamine, formaldehyde aqueous solution, polyol, epichlorohydrin, water, initiator, organophosphonate, and comonomer are as follows: 12 parts melamine, 24-40 parts formaldehyde aqueous solution, 6-18 parts polyol, 4.5-18.5 parts epichlorohydrin, 120-240 parts water, 0.09-0.8 parts initiator, 10-20 parts organophosphonate, and 5-20 parts comonomer.

21. The method for preparing the water-soluble anti-collapse agent according to claim 8, wherein, Based on parts by weight, the amounts of melamine, formaldehyde aqueous solution, polyol, epichlorohydrin, water, initiator, organophosphonate, and comonomer are as follows: 12 parts melamine, 28-36 parts formaldehyde aqueous solution, 9-15 parts polyol, 9-13.5 parts epichlorohydrin, 150-200 parts water, 0.18-0.5 parts initiator, 12-16 parts organophosphonate, and 10-15 parts comonomer.

22. A water-soluble anti-collapse agent obtained by the preparation method according to any one of claims 8-21.

23. A water-based mud, said water-based mud comprising the water-soluble anti-collapse agent according to any one of claims 1-7 or the water-soluble anti-collapse agent obtained by the preparation method according to any one of claims 8-21.

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