Anti-collapse plugging agent for drilling fluid and preparation method of anti-collapse plugging agent

Abstract

The invention discloses an anti-collapse plugging agent for drilling fluid and a preparation method thereof. The preparation method comprises the following steps: preparing 2.0-generation dendrimers or 3.0-generation dendrimers; dispersing the unsaturated silane coupling agent modified nanoparticles in a first solvent to form a dispersion liquid; dissolving 2.0-generation dendrimers or 3.0-generation dendrimers in a first solvent, dropwise adding an unsaturated hydrophilic monomer solution and an unsaturated hydrophobic monomer solution, dropwise adding the dispersion liquid at the same time, heating, and after the reaction is finished, removing the solvent to obtain the anti-sloughing plugging agent for the drilling fluid. The preparation method is simple, and has the advantages that the plugging performance is improved, the temperature resistance and pressure resistance are improved, the environmental pollution is reduced, and the drilling efficiency is improved. The prepared anti-sloughing plugging agent is not only suitable for a conventional drilling operation environment, but also can play a good role in complex environments such as high temperature and high pressure.

Description

Technical Field

[0001] This invention belongs to the field of oilfield chemical agents technology, and relates to an anti-collapse sealing agent for drilling fluid and its preparation method. Background Technology

[0002] Traditional water-based drilling fluid systems cannot meet the wellbore stability requirements of complex shale formations, generally necessitating the addition of anti-collapse plugging agents to improve their sealing and anti-collapse performance. Currently, the most commonly used anti-collapse plugging agents are asphalt-based plugging agents such as sulfonated asphalt, cationic asphalt, and emulsified asphalt. These agents primarily work by softening and deforming at high temperatures, effectively sealing micro-cracks in the wellbore to form a thin and tough mud cake. Simultaneously, they form a hydrophobic film on the surface of clay minerals, hindering the penetration of water molecules into the clay minerals. However, asphalt-based anti-collapse plugging agents not only affect drilling fluid performance but are also difficult to degrade, making it difficult to meet increasingly stringent environmental protection requirements.

[0003] Polyamidoamine dendritic molecules are macromolecular materials. Due to their hyperbranched structure, internal cavities, and highly symmetrical structure, they are commonly used in pharmaceuticals and surfactants. However, conventional polyamidoamine dendritic molecules are usually synthesized using aliphatic diamines and methyl acrylate. When added to aqueous solutions, their amide bonds are easily degraded and broken under acidic, alkaline, or high-temperature conditions, making them unsuitable for oil and gas extraction. For example, Chinese patent CN109181659A discloses a dendritic intercalating agent with quaternary ammonium groups at the end and its preparation method. This method involves directly grafting quaternary ammonium groups onto conventional polyamidoamine dendritic molecules to create inhibitors. Although these inhibitors can withstand high temperatures for a short time, water-based drilling fluids are typically weakly alkaline and contain a large amount of water. Under these conditions, the amide groups of this type of dendritic molecule degrade rapidly, causing the molecular chains to break quickly and reducing their inhibitory performance. Meanwhile, in actual drilling operations, for shale formations, increasing their temperature resistance involves not only adding inhibitors but also adding corresponding nano-plugging agents. The current approach is usually to add corresponding nanoparticles and inhibitors. However, nanoparticles and inhibitors act independently. When some nanoparticles block the shale, the inhibitors have difficulty penetrating into the shale molecules, thus weakening the inhibitor's effect. In addition, after conventional anti-collapse plugging agents are added to the drilling fluid, corresponding thickeners are also needed to maintain the viscosity of the drilling fluid, which further increases the cost. Summary of the Invention

[0004] The purpose of this invention is to provide a drilling fluid anti-collapse plugging agent and its preparation method, thereby solving the problem of low plugging and anti-collapse performance of existing anti-collapse plugging agents.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A method for preparing a drilling fluid anti-collapse plugging agent, comprising:

[0007] Prepare 2.0 generation dendritic molecules or 3.0 generation dendritic molecules;

[0008] Unsaturated silane coupling agent modified nanoparticles are dispersed in a first solvent to form a dispersion;

[0009] Dissolve the 2.0 generation or 3.0 generation dendritic molecule in a first solvent, add dropwise an unsaturated hydrophilic monomer solution and an unsaturated hydrophobic monomer solution, and simultaneously add a dispersion. Heat the mixture, and after the reaction is complete, remove the solvent to obtain an anti-collapse plugging agent for drilling fluid.

[0010] Furthermore, the preparation method of the 2.0 generation dendritic molecule or the 3.0 generation dendritic molecule includes:

[0011] Aromatic diamine was dissolved in a first solvent, and excess methyl acrylate or methyl methacrylate was added dropwise at 2-4°C. After the addition was complete, the temperature was raised to 30-70°C and the reaction was allowed to proceed for 10-20 hours. After the reaction was completed, the solvent and unreacted raw materials were removed to obtain 0.5 generation dendritic molecules.

[0012] Dissolve 0.5 generation dendritic molecules in the first solvent, and add excess aromatic diamine solution dropwise at 2-4℃. After the addition is complete, raise the temperature to 15-35℃ and react for 15-30 h. After the reaction is complete, remove the solvent to obtain 1.0 generation dendritic molecules.

[0013] Repeat the above operation several times to obtain 2.0 generation dendritic molecules or 3.0 generation dendritic molecules.

[0014] Furthermore, the aromatic diamine is p-phenylenediamine, m-phenylenediamine, diaminodiphenyl sulfone, or diaminodiphenyl ether.

[0015] Furthermore, the preparation of integer-generation dendritic molecules also includes separation and purification steps, including:

[0016] After removing the solvent, add sufficient water, shake well, and let stand to allow it to separate into layers. After separation, take the oil phase and remove the water to obtain integer generation dendritic molecules.

[0017] Furthermore, the first solvent is methanol, ethanol, or glacial acetic acid.

[0018] Furthermore, in the unsaturated silane coupling agent modified nanoparticles, the unsaturated silane coupling agent is KH-570, KH-171 or KH-151, and the nanoparticles are nano-silica or nano-zinc oxide.

[0019] The mass ratio of the 2.0 generation dendritic molecule or 3.0 generation dendritic molecule to the unsaturated silane coupling agent modified nanoparticles is 1:0.8 to 1.5.

[0020] Furthermore, the unsaturated hydrophilic monomer is at least one of allyl polyoxyethylene ether and unsaturated ammonium salt;

[0021] The unsaturated ammonium salt is trimethylallylammonium, methacryloylpropyltrimethylammonium, or acryloylpropyltrimethylammonium;

[0022] The unsaturated hydrophobic monomer is styrene, vinyltrimethylsilane, hexafluorobutyl acrylate, or hexafluorobutyl methacrylate.

[0023] The molar ratio of the unsaturated hydrophilic monomer solution to the unsaturated hydrophobic monomer solution is 1:0.3 to 0.6;

[0024] The sum of the molar amounts of the unsaturated hydrophilic monomer and the unsaturated hydrophobic monomer is 0.6m to 0.8m, where m is the total molar amount of hydrogen atoms in the amine group of the 2.0 generation dendritic molecule or the 3.0 generation dendritic molecule.

[0025] Furthermore, the unsaturated hydrophilic monomer is allyl polyoxyethylene ether and unsaturated ammonium salt, and the molar ratio of allyl polyoxyethylene ether to unsaturated ammonium salt is 1:1.0 to 1.5.

[0026] Furthermore, the unsaturated hydrophilic monomer solution and the unsaturated hydrophobic monomer solution are added at a temperature of 2–4°C, the heating temperature is 30–80°C, and the reaction time is 8–20 h.

[0027] A drilling fluid anti-collapse sealing agent prepared by the aforementioned method.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] This invention provides a method for preparing an anti-collapse plugging agent for drilling fluids. By preparing 2.0-generation or 3.0-generation dendritic molecules, their unique highly branched structure enables the formation of a denser and more stable network structure in the drilling fluid, thereby more effectively preventing fluid leakage and formation collapse during drilling. Further, using an unsaturated silane coupling agent to modify nanoparticles and dispersing them in a first solvent to form a dispersion significantly improves the high-temperature and high-pressure resistance of the plugging agent. The introduction of nanoparticles not only increases the strength of the plugging agent but also ensures stable plugging performance in complex downhole environments with high temperature and high pressure, ensuring safe drilling operations. Finally, the 2.0-generation or 3.0-generation dendritic molecules are dissolved in the first solvent, and unsaturated hydrophilic monomer solutions and unsaturated hydrophobic monomer solutions are added dropwise, along with the dispersion, to react and obtain the anti-collapse plugging agent for drilling fluids. This invention offers a simple preparation method with advantages such as improved plugging performance, enhanced temperature and pressure resistance, reduced environmental pollution, and increased drilling efficiency. This invention utilizes environmentally friendly primary solvents and modified materials to prepare an anti-collapse plugging agent with excellent environmental performance. In drilling operations, using this plugging agent can reduce pollution to groundwater and soil, thus lowering environmental risks. Furthermore, the anti-collapse plugging agent prepared by this invention is not only suitable for conventional drilling environments but also performs well in complex environments such as high temperature and high pressure. Therefore, it has a wider range of applications and higher application value.

[0030] This invention also provides a drilling fluid anti-collapse plugging agent, which exhibits good anti-collapse plugging performance and good aging resistance. After aging in water at pH 9.5 for 20 days, its performance remains essentially unchanged, still meeting the anti-collapse plugging requirements of actual shale formations. Furthermore, this drilling fluid anti-collapse plugging agent has a certain viscosity, good compatibility with conventional drilling fluids, and good temperature resistance. It requires no additional thickener during use, significantly reducing costs. Detailed Implementation

[0031] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0032] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0033] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0034] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0035] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0036] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0037] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0038] The present invention will now be described in further detail:

[0039] This invention provides a method for preparing an anti-collapse plugging agent for drilling fluids, comprising the following steps:

[0040] Step 1: Prepare 2.0 generation or 3.0 generation dendritic molecules using aromatic diamine, methyl acrylate or methyl methacrylate as raw materials.

[0041] The use of 2.0 or 3.0 generation dendritic molecules is due to the fact that aromatic diamines are either not water-soluble or have poor water solubility. When they react with methyl acrylate or methyl methacrylate, although hydrophilic amide bonds are formed, the molecular weight increases while the overall hydrophilicity of the molecule decreases. If the generation is too high, the subsequent molecules will have poor hydrophilicity and be difficult to dissolve in water, resulting in poor compatibility with drilling fluids. When it is only 1.0 generation, both its branching degree and molecular weight are low, making it difficult to meet the requirements.

[0042] Meanwhile, using aromatic diamines as raw materials, compared to aliphatic diamines, results in greater steric hindrance and poorer water solubility. Therefore, it not only has better temperature and salt resistance, but also degrades more slowly in drilling fluid, making it better suited for shale formation anti-collapse sealing.

[0043] The preparation methods for 2.0 generation or 3.0 generation dendritic molecules are as follows:

[0044] Aromatic diamine was dissolved in a first solvent, and excess methyl acrylate or methyl methacrylate was added dropwise at 2-4°C. After the addition was complete, the temperature was raised to 30-70°C and the reaction was allowed to proceed for 10-20 hours. After the reaction was completed, the solvent and unreacted raw materials were removed to obtain 0.5 generation dendritic molecules.

[0045] Dissolve 0.5 generation dendritic molecules in the first solvent, and add an excess of aromatic diamine solution dropwise at 2-4℃. After the addition is complete, raise the temperature to 15-35℃ and react for 15-30 h. After the reaction is complete, remove the solvent to obtain 1.0 generation dendritic molecules.

[0046] Repeat the above operation several times to obtain 2.0 generation dendritic molecules or 3.0 generation dendritic molecules.

[0047] Among them, the aromatic diamine is p-phenylenediamine, m-phenylenediamine, diaminodiphenyl sulfone, or diaminodiphenyl ether.

[0048] The first solvent is one of methanol, ethanol, or glacial acetic acid.

[0049] Because this invention uses aromatic diamines, which have high boiling points, they are difficult to purify using conventional methods. Therefore, a new purification method is proposed. The method for obtaining integer-generation dendritic molecules also includes a separation and purification step: after removing the solvent, sufficient water is added, the mixture is shaken well, and allowed to stand to separate into layers. After separation, the oil phase is collected and the water is removed to obtain the integer-generation dendritic molecules.

[0050] Step 2: Disperse unsaturated silane coupling agent modified nanoparticles in the first solvent to form a dispersion.

[0051] Among them, unsaturated silane coupling agent modified nanoparticles refer to products obtained by modifying nanoparticles with silane coupling agents containing double bonds. The nanoparticles must be capable of being modified with silane coupling agents. Specifically, the silane coupling agents containing double bonds are KH-570, KH-171, or KH-151, and the nanoparticles are nano-silica or nano-zinc oxide. Notably, nano-calcium carbonate is generally not used because it is difficult to graft silane coupling agents onto it. Of course, the effects vary slightly for modified nanoparticles with different grafting rates, but the overall difference is not significant.

[0052] Step 3: Dissolve the 2.0 generation or 3.0 generation dendritic molecule in the first solvent. Under the condition of 2-4℃, add dropwise an unsaturated hydrophilic monomer solution and an unsaturated hydrophobic monomer solution with a molar ratio of 1:0.3-0.6, and simultaneously add the dispersion. After the addition is complete, raise the temperature to 30-80℃ and react for 8-20 hours. After the reaction is completed, remove the solvent to obtain the anti-collapse sealing agent for drilling fluid.

[0053] The sum of the molar amounts of unsaturated hydrophilic monomers and unsaturated hydrophobic monomers is 0.6m to 0.8m, where m is the total molar amount of hydrogen atoms in the amine group of the 2.0 generation dendritic molecule or the 3.0 generation dendritic molecule.

[0054] The mass ratio of 2.0-generation dendritic molecules or 3.0-generation dendritic molecules to unsaturated silane coupling agent modified nanoparticles is 1:0.8 to 1.5.

[0055] Unsaturated hydrophilic monomers refer to monomers with good hydrophilic properties and containing a double bond. In this invention, the unsaturated hydrophilic monomer is at least one of allyl polyoxyethylene ether and an unsaturated ammonium salt. In the allyl polyoxyethylene ether, the molecular weight of the polyoxyethylene is 400–1500. The unsaturated ammonium salt is trimethylallyl ammonium, methacryloylpropyltrimethylammonium, or acryloylpropyltrimethylammonium. Specifically, for quaternary ammonium salts, the alkyl chain length should ideally not be too long. Excessively long alkyl chains result in relatively low hydrophilicity, affecting the hydrophilicity of the final product and thus reducing its compatibility with drilling fluids.

[0056] Preferably, for unsaturated hydrophilic monomers, a combination of allyl polyoxyethylene ether and unsaturated quaternary ammonium salt is typically chosen, resulting in a molecular structure that contains both flexible molecular chains and quaternary ammonium groups. When the unsaturated hydrophilic monomer is a mixture of allyl polyoxyethylene ether and unsaturated ammonium salt, the molar ratio of allyl polyoxyethylene ether to unsaturated ammonium salt is 1:1.0 to 1.5. Under these conditions, the synthesized anti-collapse plugging agent exhibits superior performance.

[0057] Unsaturated hydrophobic monomers are monomers that are hydrophobic overall and contain a double bond. In this invention, the unsaturated hydrophobic monomers are styrene, vinyltrimethylsilane, hexafluorobutyl acrylate, and hexafluorobutyl methacrylate.

[0058] For dendritic molecules of integer generations, their end-capping groups are primary amine groups. Therefore, in this invention, the added unsaturated hydrophilic monomers, unsaturated hydrophobic monomers, and unsaturated silane coupling agent-modified nanoparticles are all used to react with the primary amine groups, thereby modifying the dendritic molecules. The unsaturated hydrophilic monomers enhance the hydrophilicity of the system, giving the dendritic molecules and unsaturated silane coupling agent-modified nanoparticles good hydrophilicity after reaction. This not only allows them to disperse in water-based drilling fluids, giving them good compatibility, but also enables them to adsorb onto shale. The unsaturated hydrophobic monomers give the grafted portions of the dendritic molecules a certain degree of hydrophobicity. When adsorbed onto shale, these hydrophobic groups prevent water molecules from entering the shale interior, further increasing its anti-collapse performance. As for the nanoparticles, since most shale pores are nanoscale, using nanoparticles can effectively seal shale pores.

[0059] Another object of the present invention is to disclose a drilling fluid anti-collapse plugging agent, which is prepared by the above-described method. The anti-collapse plugging agent prepared by this method has good anti-collapse plugging effect and good aging resistance.

[0060] The present invention will be further described in detail below with reference to specific embodiments:

[0061] In the following examples, the average particle size of the nano-silica used is approximately 60 nm.

[0062] In the following examples, the degree of reaction of the dendritic molecules is considered to be 100%, that is, for a 0.5 generation dendritic molecule, it is considered that 1 mol of aromatic diamine reacts completely with 4 mol of methyl acrylate or methyl methacrylate; for a 1.0 generation dendritic molecule, it is considered that 1 mol of 0.5 generation dendritic molecule reacts completely with 2 mol of aromatic diamine, and so on.

[0063] The method for modifying nanoparticles with silane coupling agent in the following examples is as follows: 10g of nano-silica is ultrasonically dispersed in water, followed by the addition of ethanol and 1g of silane coupling agent, wherein the mass ratio of nano-silica, water, and ethanol is 1:3:50. The mixture is then refluxed at 80°C for 15 hours. After the reaction is complete, the nanoparticles are separated by centrifugation to obtain the silane coupling agent-modified nanoparticles. In use, the modified nanoparticles are ultrasonically dispersed in a solvent.

[0064] Example 1:

[0065] Preparation of dendritic molecules: 10.8 g of m-phenylenediamine was dissolved in 100 mL of ethanol in an ice-water bath at 2 °C. 38.0 g of methyl acrylate was added dropwise under continuous stirring. After the addition was complete, the temperature was raised to 50 °C and the reaction was continued for 13 h. After the reaction was completed, the solvent was removed by vacuum distillation to obtain the 0.5 generation dendritic molecule.

[0066] Under ice-water bath conditions at 2℃, the above-mentioned 0.5 generation dendritic molecule was dissolved in 200 mL of ethanol, and 43.2 g of m-phenylenediamine was dissolved in 350 mL of ethanol. Then, the ethanol solution of m-phenylenediamine was added dropwise to the 0.5 generation dendritic molecule solution. After the addition was complete, the temperature was raised to 25℃ and the reaction was carried out for 24 h. After the reaction was completed, the solvent was removed by vacuum distillation, and then 100 mL of water was added. The mixture was shaken well and allowed to stand to separate into layers. The oil phase was taken and the water in the oil phase was removed by vacuum distillation to obtain the 1.0 generation dendritic molecule.

[0067] Repeat the above steps until the 2.0 generation dendritic molecule is obtained.

[0068] Preparation of anti-collapse sealing agent: 100g of KH570 modified nano-silica was added to 200mL of ethanol and sonicated for 30min to form a dispersion. 102.7g of 2.0 generation dendritic molecules was dissolved in 1500mL of ethanol. 151g of APEG-800 (allyl polyoxyethylene ether with a molecular weight of approximately 800) was dissolved in 400mL of ethanol. 29.7g of trimethylallyl ammonium chloride was dissolved in 200mL of ethanol. 16.6g of styrene was dissolved in 150mL of ethanol. Under ice bath conditions and continuous stirring, the dispersion, APEG-800 solution, trimethylallyl ammonium chloride solution, and styrene solution were added dropwise to the 2.0 generation dendritic molecule solution. After the addition was complete, the temperature was raised to 60℃ and the reaction was allowed to proceed for 10h. After the reaction was completed, the solvent was removed by vacuum distillation to obtain the final product.

[0069] Example 2:

[0070] Preparation of modified nanoparticles: The difference from Example 1 is that the final product is a 3.0 generation dendritic molecule.

[0071] Preparation of anti-collapse sealing agent: The difference from Example 1 is that the amount of 3.0 generation dendritic molecules added is 232.5g, the amount of KH570 modified nano silica added is 325g instead of 100g, and APEG-800 is replaced with APEG-500 with an amount of 97g, and it does not need to be dissolved in ethanol.

[0072] Example 3:

[0073] Preparation of modified nanoparticles: Same as in Example 1.

[0074] Preparation of anti-collapse sealing agent: The difference from Example 1 is that the amount of APEG-800 added is 151g (0.18), the amount of trimethylallyl ammonium chloride added is 25.6g (0.19), styrene is replaced with vinyltrimethylsilane and its amount is 13g (0.13) and it does not need to be dissolved in ethanol. The reaction conditions are 40°C for 18h.

[0075] Example 4:

[0076] Preparation of modified nanoparticles: Same as in Example 1.

[0077] Preparation of anti-collapse sealing agent: The difference from Example 1 is that trimethylallyl ammonium chloride was not added, and the amount of APEG-800 added was 336g.

[0078] Example 5:

[0079] Preparation of modified nanoparticles: Same as in Example 1.

[0080] Preparation of anti-collapse sealing agent: The difference from Example 1 is that APEG-800 was not added, and the amount of trimethylallyl ammonium chloride added was 54g.

[0081] Comparative Example 1:

[0082] The difference from Example 1 is that the 2.0 generation dendritic molecule was prepared using ethylenediamine and methyl acrylate as raw materials, while the rest are the same.

[0083] Comparative Example 2:

[0084] The difference from Example 1 is that the number of generations of the dendritic molecules is 1.0, while the rest are the same.

[0085] Comparative Example 3:

[0086] The difference from Example 1 is that the number of generations of the dendritic molecules is 4.0, while the rest are the same.

[0087] Performance comparison of the drilling fluid anti-collapse plugging agents prepared in Examples 1-5 of this invention with those in Comparative Examples 1-3:

[0088] 1. Thickening effect

[0089] The drilling fluid composition is as follows: by mass percentage, it contains 1% anti-collapse plugging agent, 0.2% flow aid DRKJ-16, 0.05% sodium carbonate, and 0.1% bactericide SK-1, with the remainder being water. Its viscosity was measured using a rotational viscometer at 25°C. The final test results are shown in Table 1.

[0090] Table 1. Thickening Test

[0091]

[0092] As shown in Table 1, the anti-collapse plugging agents for drilling fluids prepared in Examples 1-5 of this invention all have high viscosity and can meet the requirements of drilling fluids. For Comparative Examples 2-3, it was found that the prepared anti-collapse plugging agents are spherical and uniformly dispersed in water, resulting in poor solubility of their dendritic molecular components in water, ultimately providing virtually no thickening effect.

[0093] 2. Expansion resistance and long-term high-temperature stability

[0094] Take the anti-collapse sealing agents prepared in Examples 1-5 and Comparative Examples 1-3 above, add water to make the concentration 1%, and adjust its pH to 9.5 for measuring its anti-swelling rate; take a portion of the prepared solution, age it at 90°C for 30 days, and measure its anti-swelling rate again.

[0095] The anti-swelling rate was tested according to the method in "SY / T 5971-2016 Performance Evaluation Method of Clay Stabilizer for Fracturing, Acidizing and Water Injection in Oil and Gas Fields". Specifically, 0.50g of sodium-based bentonite was added to a test tube, along with 10mL of drilling fluid anti-collapse sealing agent solution. The mixture was shaken well, allowed to stand for 2 hours, and then centrifuged at 1500r / min for 15min. The volume V1 of the sodium-based bentonite was read. 0.50g of sodium-based bentonite was added to a test tube, along with 10mL of water. The mixture was shaken well, allowed to stand for 2 hours, and then centrifuged at 1500r / min for 15min. The volume V2 of the sodium-based bentonite was read. 0.50g of sodium-based bentonite was added to a test tube, along with 10mL of kerosene. The mixture was shaken well, allowed to stand for 2 hours, and then centrifuged at 1500r / min for 15min. The volume V0 of the sodium-based bentonite was read.

[0096] The formula for calculating its anti-swelling rate is:

[0097]

[0098] The final anti-swelling rate test results are shown in Table 2.

[0099] Table 2 Results of Anti-swelling Rate Test

[0100] sample Pre-aging anti-swelling rate % Anti-swelling rate after aging (%) Example 1 88.5 86.4 Example 2 84.3 83.9 Example 3 86.7 83.8 Example 4 79.2 76.4 Example 5 83.5 80.5 Comparative Example 1 89.1 54.2 Comparative Example 2 67.3 53.7 Comparative Example 3 55.1 54.9

[0101] As shown in Table 2, the anti-swelling and plugging agent for drilling fluid in this embodiment of the invention has a high anti-swelling rate, reaching up to 88% or more. Furthermore, after aging at 90°C for a period of time, the decrease in its anti-swelling rate is relatively small, indicating that it still possesses good long-term stability even under alkaline conditions. Referring to Comparative Example 1, its anti-swelling rate decreased sharply after 30 days of aging, indicating that the dendritic molecules prepared using conventional aliphatic diamines basically lack long-term stability. For current drilling processes, the shortest duration is approximately twenty days, and the longest can reach several tens of days. Clearly, dendritic molecules prepared using aliphatic diamines are difficult to adapt to long-term drilling processes. Referring to Comparative Examples 2 and 3, it is shown that the generation number of the dendritic molecule is a crucial factor; too high or too low a number do not result in good anti-swelling performance.

[0102] 3. Filtration loss reduction performance test

[0103] Using a high-temperature and high-pressure fluid loss meter and following the method in "Q / SH 0047-2007 General Technical Requirements for Salt-Resistant and High-Temperature Fluid Loss Reduction Agents for Drilling Fluids", the fluid loss reduction performance of the agent was measured after hot rolling at 120℃ for 16 hours. The base slurry was prepared by adding 50g of sodium-based bentonite to 700mL of water and stirring at high speed for 20min. The final measurement results are shown in Table 3.

[0104] Table 3 High Temperature and High Pressure Filtration Loss

[0105]

[0106] As can be seen from Table 3, the drilling fluid anti-collapse plugging agents prepared in Examples 1 to 5 of the present invention can all reduce their filtration loss and have a good plugging and inhibition effect.

[0107] 4. Blocking rate test

[0108] Shale core samples were taken, and 1% of drilling fluid anti-collapse plugging agent was added to the base slurry. The permeability was measured using a pressure transmission experiment, and the final results are shown in Table 4. The base slurry composition was: 1000 mL water + 100 g sodium-based bentonite + 5 g sodium carbonate.

[0109] Table 4. Changes in Permeability

[0110] sample <![CDATA[Initial core permeability / 10 -4 mD]]> <![CDATA[Permeability after core injection / 10 -4 mD]]> Blocking rate % Example 1 8.727 0.102 98.8 base slurry 6.425 5.686 11.5

[0111] As can be seen from Table 4, the drilling fluid anti-collapse plugging agents prepared in Examples 1 to 5 of the present invention can all effectively plug shale, and the plugging rate is relatively high.

[0112] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a sag-resistant plugging agent for a drilling fluid, characterized by, The application relates to a drilling fluid anti-sloughing plugging agent. The preparation of the 2.0 generation dendrimer or the 3.0 generation dendrimer comprises the following steps: The unsaturated silane coupling agent modified nanoparticles are dispersed in a first solvent to form a dispersion liquid; The 2.0 generation dendrimer or the 3.0 generation dendrimer is dissolved in the first solvent, unsaturated hydrophilic monomer solution and unsaturated hydrophobic monomer solution are added dropwise, the dispersion liquid is added dropwise, heating is conducted, after the reaction is completed, the solvent is removed, and the drilling fluid anti-sloughing plugging agent is obtained.

2. The method for preparing the anti-collapse sealing agent for drilling fluid according to claim 1, characterized in that, The preparation method of the 2.0 generation dendrimer or the 3.0 generation dendrimer comprises the following steps: The aromatic diamine is dissolved in a first solvent, an excess of methyl acrylate or methyl methacrylate is added dropwise at 2-4 DEG C, after the dropwise addition is completed, the temperature is increased to 30-70 DEG C and reaction is conducted for 10-20 h, after the reaction is completed, the solvent and unreacted raw materials are removed, and the 0.5 generation dendrimer is obtained; The 0.5 generation dendrimer is dissolved in a first solvent, an excess of aromatic diamine solution is added dropwise at 2-4 DEG C, after the dropwise addition is completed, the temperature is increased to 15-35 DEG C and reaction is conducted for 15-30 h, after the reaction is completed, the solvent is removed, and the 1.0 generation dendrimer is obtained; The above operation is repeated for several times, and the 2.0 generation dendrimer or the 3.0 generation dendrimer is obtained.

3. The method for preparing the anti-collapse sealing agent for drilling fluid according to claim 2, characterized in that, The aromatic diamine is p-phenylenediamine, m-phenylenediamine, diaminodiphenyl sulfone or diaminodiphenyl ether.

4. The method for preparing the anti-collapse sealing agent for drilling fluid according to claim 2, characterized in that, When the integer generation dendrimer is prepared, a separation and purification step is further included, which comprises the following steps: After the solvent is removed, sufficient water is added, shaking is conducted, and then standing is conducted to make the liquid layer, the oil phase is taken after the liquid layer is separated, and the water is removed, and the integer generation dendrimer is prepared.

5. The method of preparing the anti-sloughing plugging agent for drilling fluid according to claim 1 or 2, characterized in that, The first solvent is methanol, ethanol or glacial acetic acid.

6. The method of claim 1, wherein the anti-sloughing agent is prepared by the steps of: In the unsaturated silane coupling agent modified nanoparticles, the unsaturated silane coupling agent is KH-570, KH-171 or KH-151, and the nanoparticles are nanosilica or nanozinc oxide; The mass ratio of the 2.0 generation dendrimer or the 3.0 generation dendrimer to the unsaturated silane coupling agent modified nanoparticles is 1:(0.8-1.5).

7. The method for preparing the anti-collapse sealing agent for drilling fluid according to claim 1, characterized in that, The unsaturated hydrophilic monomer is at least one of allyl polyoxyethylene ether and unsaturated ammonium salt; The unsaturated ammonium salt is trimethylallyl ammonium, methacryloyl propyl trimethyl ammonium or acryloyl propyl trimethyl ammonium; The unsaturated hydrophobic monomer is styrene, vinyl trimethyl silane, hexafluorobutyl acrylate or hexafluorobutyl methacrylate; The molar ratio of the unsaturated hydrophilic monomer solution to the unsaturated hydrophobic monomer solution is 1:(0.3-0.6); The sum of the molar amounts of the unsaturated hydrophilic monomer and the unsaturated hydrophobic monomer is 0.6m-0.8m, and m is the total molar amount of hydrogen atoms in amine groups in the 2.0 generation dendrimer or the 3.0 generation dendrimer.

8. The method for preparing the anti-collapse sealing agent for drilling fluid according to claim 7, characterized in that, The unsaturated hydrophilic monomer is allyl polyoxyethylene ether and unsaturated ammonium salt, and the molar ratio of the allyl polyoxyethylene ether to the unsaturated ammonium salt is 1:(1.0-1.5).

9. The method for preparing the anti-collapse sealing agent for drilling fluid according to claim 1, characterized in that, The temperature for dropwise adding the unsaturated hydrophilic monomer solution and the unsaturated hydrophobic monomer solution is 2-4 DEG C, the heating temperature is 30-80 DEG C, and the reaction time is 8-20 h.

10. The drilling fluid anti-sloughing plugging agent prepared by the preparation method in any one of claims 1-9.

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