A kind of double-repellent nano plugging agent for drilling fluid and its preparation method and application

Abstract

The present invention discloses an amphiphobic nanometer plugging agent for drilling fluid, a preparation method thereof, and an application thereof. The preparation method of the amphiphobic nanometer plugging agent for drilling fluid comprises: surface modification of nanometer calcium carbonate by using a silane coupling agent, and then, under the condition of adding an initiator, mixing and reacting the modified nanometer calcium carbonate with a reaction monomer to prepare the amphiphobic nanometer plugging agent for drilling fluid; the reaction monomer comprises a fluorine-containing short carbon chain acrylate, 2-acrylamide-2-methylpropanesulfonic acid, and acrylic acid. The amphiphobic nanometer plugging agent provided by the present invention can mainly enrich the fluorine element in the shell layer, thereby reducing the amount of fluorine monomer used while maintaining the original performance of the organic fluorine polymer. The functional chain segments containing fluorine and silicon migrate to the surface of the matrix, thereby obtaining an excellent hydrophobic polymer surface. At the same time, the amount of expensive fluorine and silicon raw materials used can be significantly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of drilling fluids, and in particular to an amphoteric nanometer plugging agent for drilling fluids, a preparation method thereof, and an application thereof. Background Art

[0002] The exploration and development of shale gas and other oil and gas resources currently present numerous challenges, particularly when drilling into muddy shale formations in long horizontal sections. Hydration, expansion, and dispersion can easily occur, leading to wellbore instability. According to statistics from experts and scholars, the vast majority of shale pores are between 5 and 300 nanometers in diameter. Even a small amount of filtrate intrusion can significantly increase pore pressure near the wellbore wall, weakening the effective support provided by the hydrostatic column pressure, leading to wellbore collapse and instability.

[0003] Conventional plugging agents, such as asphalt and polymeric alcohols, have a micron-sized particle size distribution and only form a temporary plugging layer on the formation surface, making it difficult to penetrate the nano-scale pore structure of shale and effectively seal it. Therefore, the key to maintaining shale wellbore stability is the ability of the plugging material to penetrate micropores, microcracks, and bedding structures, thereby forming a tight seal and reducing filtrate intrusion and pressure transmission. Due to their extremely small particle size and high surface energy, traditional nano-plugging materials are in a very unstable thermodynamic state and are prone to agglomeration, which increases the particle size and makes it difficult to penetrate the micro- and nano-pores of shale formations, resulting in poor plugging effectiveness and affecting the overall performance of the drilling fluid.

[0004] At the same time, during the drilling process of long horizontal sections, in order to reduce friction and improve the lubricity of water-based drilling fluid, a large amount of lubricants such as crude oil are usually added. As the drilling time increases, these oil-philic treatment agents enter the shale formation, which will also increase the pore pressure near the well wall and aggravate the instability of the well wall in the broken formation.

[0005] Patent CN113355072A discloses a micro-nano liquid plugging agent, its preparation method, and its application. Its components are as follows: 25% to 45% asphalt, 2% to 10% polymer monomer, 1.0% to 5.0% emulsifier, 10% to 35% nano-micron plugging particles, 10% to 20% water, and 15% to 35% solvent oil. The composition of the agent indicates that it forms only a temporary plugging layer on the shale surface and cannot penetrate into the shale pores to effectively block the plugging.

[0006] Patent CN112430455A discloses a nano-blocking agent, its preparation method, and its application. The nano-blocking agent comprises, by weight, 500-600 parts white oil; 5 parts graphene; 5 parts modifier; 300-350 parts nano-calcium carbonate; 30-50 parts nano-silicon dioxide; and 20-40 parts stabilizer. This nano-blocking agent has a wide particle size distribution, suitable for plugging nanopores in various shale formations during drilling. However, component analysis indicates that the agent's surface is not oleophobic, allowing lipophilic agents such as crude oil to easily penetrate the formation.

[0007] Therefore, it is urgent to develop a nano-sealing agent that can effectively block nano-scale pore throats and has hydrophobic and oleophobic properties, so that it can effectively block pores while changing the wettability of the rock surface, slowing down the invasion of liquid phases such as water-based drilling fluid filtrate and lubricants into the formation, and maintaining the stability of the well wall. Summary of the Invention

[0008] In order to overcome the problems existing in the prior art, such as the easy agglomeration of nano-plugging materials and the inability of conventional nano-plugging agents to achieve a good oleophobic effect, which makes the lipophilic treatment agent in the drilling fluid extremely easy to invade the formation and cause well wall instability, the present invention provides a double-phobic nano-plugging agent for drilling fluid that can effectively plug nano-scale pore throats, has good hydrophobic and oleophobic effects, can improve the plugging strength, reduce the penetration of drilling fluid into the formation during drilling, and ensure the stability of the well wall.

[0009] To solve the above technical problems, the first aspect of the present invention provides a method for preparing an amphiphobic nano plugging agent for drilling fluid, comprising: surface modification of nano-calcium carbonate using a silane coupling agent, and then mixing and reacting the modified nano-calcium carbonate with a reactive monomer under the condition of adding an initiator to prepare the amphiphobic nano-plugging agent for drilling fluid; the reactive monomer includes a fluorine-containing short carbon chain acrylate, 2-acrylamide-2-methylpropanesulfonic acid (AMPS) and acrylic acid (AA).

[0010] According to some embodiments of the present invention, the modified nano-calcium carbonate is grafted with a copolymer of fluorine-containing short carbon chain acrylate, 2-acrylamide-2-methylpropanesulfonic acid and acrylic acid.

[0011] The dual-repellent nano plugging agent for drilling fluid of the present invention introduces a certain amount of a copolymer containing a fluorine-containing short carbon chain acrylate. The copolymer has excellent heat resistance and chemical stability, extremely low surface energy, excellent hydrophobicity and oleophobicity, and good film-forming ability. The use of the polymer to graft-modify nano-calcium carbonate can not only solve the problem of poor dispersibility of the nano-calcium carbonate, but also change the surface wettability of the nano-calcium carbonate, giving it a super strong hydrophobic and oleophobic effect, thereby enhancing the membrane strength of the plugging layer.

[0012] According to some embodiments of the present invention, a method for preparing an amphiphobic nano plugging agent for drilling fluid comprises the following steps:

[0013] (1) Surface modification of nano calcium carbonate:

[0014] Prepare nano-calcium carbonate solid slurry and silane coupling agent solution respectively, add the silane coupling agent solution dropwise to the nano-calcium carbonate solid slurry under nitrogen atmosphere and heating conditions, stir and react to obtain modified nano-calcium carbonate;

[0015] (2) Under the condition of adding an initiator, the modified nano-calcium carbonate and the reaction monomer are mixed and reacted:

[0016] Step A: In a nitrogen atmosphere, mixing the first part of the emulsifier aqueous solution with the first part of the reaction monomer, and stirring to obtain a pre-emulsion;

[0017] Step B: In a nitrogen atmosphere, anhydrous ethanol, modified nano-calcium carbonate, the second part of the emulsifier aqueous solution and the second part of the reaction monomer are mixed, an initiator is added, and after heating and stirring, the pre-emulsion obtained in step A is added dropwise to continue the reaction, and finally an amphiphobic nano plugging agent for drilling fluid is obtained.

[0018] According to some embodiments of the present invention, the mass ratio of fluorinated short carbon chain acrylate, 2-acrylamide-2-methylpropanesulfonic acid (AMPS) and acrylic acid (AA) in the reaction monomers is (10-30):(20-40):(30-60), for example, 10:20:30 or 20:30:50 or 30:40:60.

[0019] According to some embodiments of the present invention, the fluorine-containing short carbon chain acrylate is any one of trifluoroethyl methacrylate, hexafluorobutyl methacrylate, and dodecafluoroheptyl methacrylate.

[0020] According to some embodiments of the present invention, the silane coupling agent is an unsaturated hydrocarbon alkoxysilane.

[0021] According to some embodiments of the present invention, the ratio of the amount of the silane coupling agent to the amount of nano-calcium carbonate is (0.5-2.5) mL:10 g, for example, 0.5 mL:10 g, 1.5 mL:10 g, 2.5 mL:10 g.

[0022] According to some embodiments of the present invention, the unsaturated hydrocarbon alkoxysilane is any one of vinyltriethoxysilane, vinyltrimethoxysilane, vinyltributoxysilane, γ-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, and 3-acryloxypropyltrimethoxysilane, preferably vinyltributoxysilane, γ-methacryloxypropyltrimethoxysilane, or 3-acryloxypropyltriethoxysilane.

[0023] According to some embodiments of the present invention, the mass ratio of the modified nano-calcium carbonate to the reaction monomer is (4-7):10, for example, 4:10, 5:10, or 7:10.

[0024] According to some embodiments of the present invention, the average particle size of the modified nano-calcium carbonate is 70-150 nm, for example, 70 nm, 100 nm, or 150 nm.

[0025] According to some embodiments of the present invention, in the surface modification process of the nano-calcium carbonate, the nano-calcium carbonate solid slurry is prepared by mixing nano-calcium carbonate, anhydrous ethanol, ammonia water and water in a ratio of 1g:(19-22)mL:(0.25-0.30)mL:(0.3-0.5)mL and then ultrasonically dispersing the mixture, for example, 10g:190mL:2.5mL:3mL, 10g:200mL:3mL:4mL, 10g:220mL:3mL:5mL; preferably, the ultrasonic dispersion is for 25-40min, for example, 30min.

[0026] According to some embodiments of the present invention, during the surface modification process of the nano-calcium carbonate, the silane coupling agent solution is prepared by mixing the silane coupling agent, anhydrous ethanol and water in a volume ratio of 1: (5-10): (0.2-0.4) and then ultrasonically dispersing the mixture, for example, 2.5:25:1, 1.5:10.5:0.45, or 0.5:2.5:0.1; preferably, the ultrasonic dispersion is performed for 15-25 minutes, for example, 20 minutes.

[0027] According to some embodiments of the present invention, during the surface modification process of the nano-calcium carbonate, the heating temperature is 65-80°C, for example, 65°C or 80°C.

[0028] According to some embodiments of the present invention, during the surface modification process of the nano-calcium carbonate, the stirring speed is 600-800 rpm / min, preferably 700-800 rpm / min, such as 700 rpm / min, 800 rpm / min, and the stirring time is 3-7h, such as 3h, 5h, 7h.

[0029] According to some embodiments of the present invention, in the surface modification process of the nano-calcium carbonate, the stirring reaction further includes repeated filtration and washing with anhydrous ethanol, and then drying; the drying temperature is 60°C-65°C, and the drying time is 6-8h, preferably 8h.

[0030] According to some embodiments of the present invention, during the mixing and reaction of the modified nano-calcium carbonate graft with the reaction monomer under the condition of adding an initiator, the mass ratio of the first part of the emulsifier aqueous solution to the second part of the emulsifier aqueous solution is (2-9): (1-3), preferably (2-4): 1, for example, 2: 1, 3: 1, 4: 1; the ratio of the mass of the first part of the reaction monomer to the mass of the second part of the reaction monomer is (7-9): (0.5-2), for example, 9: 1.

[0031] According to some embodiments of the present invention, the mass ratio of the emulsifier to water in the emulsifier aqueous solution is 1:(20-30), for example, 2.5:50, 1.5:40, or 1:30.

[0032] According to some embodiments of the present invention, the amount of the emulsifier is 0.05-0.2 of the mass of the reaction monomer, preferably 0.05-0.1, such as 0.1, 0.075, or 0.07.

[0033] According to some embodiments of the present invention, the emulsifier is selected from one or more of disodium dodecyl diphenyl ether sulfonate, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, octylphenol polyoxyethylene ether, and nonylphenol polyoxyethylene ether in any proportion, preferably a mixture of sodium dodecylbenzene sulfonate or octylphenol polyoxyethylene ether or sodium dodecyl sulfate and nonylphenol polyoxyethylene ether in a mass ratio of 1:1.

[0034] According to some embodiments of the present invention, in step A, the stirring rate is 800-1200 rpm / min, such as 800 rpm / min, 1000 rpm / min, 1200 rpm / min, and the stirring time is 1-2 h, such as 1 h, 1.5 h, 2 h.

[0035] According to some embodiments of the present invention, in step B, the mass ratio of the modified nano-calcium carbonate to anhydrous ethanol is (1-3):(15-30), for example 1:20.

[0036] According to some embodiments of the present invention, in step B, before adding the initiator, the step further includes adjusting the pH value of the solution, preferably, the pH value is 7-8, for example, the pH value is 7 or 8; preferably, the pH value is adjusted with aqueous ammonia;

[0037] More preferably, the amount of the initiator is 0.02-0.04 of the mass of the reaction monomers, for example, 0.02, 0.04.

[0038] According to some embodiments of the present invention, the initiator is potassium persulfate or azobisisobutyronitrile.

[0039] According to some embodiments of the present invention, in step B, the heating temperature is 70°C-80°C, for example, 70°C, 75°C, or 80°C.

[0040] According to some embodiments of the present invention, in step B, the stirring rate is 1200-1800 rpm / min, for example, 1500 rpm / min, and the stirring time is 1-2 h, for example, 1 h, 2 h.

[0041] According to some embodiments of the present invention, in step B, the reaction is continued for 3-4 hours, for example, 3 hours or 4 hours.

[0042] The second aspect of the present invention provides the above-mentioned amphiphobic nano plugging agent for drilling fluid obtained by the above-mentioned preparation method.

[0043] A third aspect of the present invention provides the use of the above-mentioned amphiphobic nanometer plugging agent for drilling fluid or the amphiphobic nanometer plugging agent for drilling fluid obtained by the above-mentioned preparation method in the field of drilling fluid.

[0044] Beneficial effects:

[0045] The present invention provides a dual-repellent nanometer plugging agent for drilling fluid. By reacting modified nanometer calcium carbonate with fluorine-containing short carbon chain acrylate, 2-acrylamide-2-methylpropanesulfonic acid and acrylic acid in the presence of an initiator, the problem of poor dispersibility of the nanometer calcium carbonate can be solved, and the surface wettability of the nanometer calcium carbonate can be effectively changed to make it have better hydrophobic and oleophobic effects, thereby enhancing the membrane strength of the plugging layer.

[0046] The dual-repellent nano-blocking agent provided by the present invention can enrich the fluorine element mainly in the shell layer, thereby reducing the amount of fluorine monomer used while maintaining the original properties of the organic fluorine polymer. The functional chain segments containing fluorine and silicon migrate to the surface of the matrix to obtain an excellent hydrophobic polymer surface. At the same time, the amount of expensive fluorine and silicon raw materials used can be significantly reduced.

[0047] The amphiphobic nano plugging agent for drilling fluid provided by the present invention introduces the sulfonic acid group in 2-acrylamide-2-methylpropanesulfonic acid AMPS, which can improve the stability of the amphiphobic nano plugging agent for drilling fluid at high temperature to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The present invention provides a method for preparing a double-repellent nanometer plugging agent for drilling fluid, which can be used to infer the preparation route of the double-repellent nanometer plugging agent for drilling fluid, as shown in the accompanying drawings:

[0049] Figure 1 Schematic diagram of the route for surface modification of nano-calcium carbonate: R1 is a saturated alkane, and R2 contains an unsaturated olefin;

[0050] Figure 2 Schematic diagram of the route for grafting modified nano-calcium carbonate with a copolymer containing a fluorine-containing short carbon chain acrylate: wherein R3 is H, CH3, CF3, R f A fluorine-containing group. DETAILED DESCRIPTION

[0051] The present invention will be further described below with reference to the following examples, but the present invention is not limited to these examples.

[0052] Example 1

[0053] This embodiment provides a nanometer-sized ampholyte for drilling fluid. The preparation method of the nanometer-sized ampholyte for drilling fluid is as follows:

[0054] (1) Surface modification of nano calcium carbonate:

[0055] Step a: In beaker 1, 10 g of nano-calcium carbonate (average particle size 70 nm), 190 mL of anhydrous ethanol, 2.5 mL of ammonia water, and 3 mL of water were added to prepare a nano-calcium carbonate solid slurry in proportion. After ultrasonic dispersion for 30 minutes, the slurry was transferred to a four-necked flask 1 equipped with a stirrer, a nitrogen inlet tube, a condenser, and a separatory funnel.

[0056] Step b: In beaker 2, add 2.5 mL of vinyltributoxysilane, 25 mL of anhydrous ethanol and 1.0 mL of water, and ultrasonically disperse for 20 min to fully hydrolyze the vinyltributoxysilane. The fully hydrolyzed silane coupling agent solution is transferred to a separatory funnel;

[0057] Step c, under the condition of a water bath heating temperature of 65° C. and a nitrogen atmosphere, using the separatory funnel in step b, dropwise adding fully hydrolyzed vinyltributoxysilane to the four-necked flask 1 containing the nano-calcium carbonate solid slurry in step a, stirring at a stirring rate of 800 rpm / min for 7 hours, repeatedly filtering and washing with anhydrous ethanol, and then drying at a temperature of 60° C. to 65° C. for 8 hours to obtain modified nano-calcium carbonate;

[0058] (2) Under the condition of adding an initiator, the modified nano-calcium carbonate and the reaction monomer are mixed and reacted:

[0059] Step A: In a nitrogen atmosphere, 2.0 g of sodium dodecylbenzenesulfonate, 40 g of deionized water, 3.753 g of trifluoroethyl methacrylate, 7.497 g of 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and 11.25 g of acrylic acid (AA) were mixed and pre-emulsified at a stirring rate of 1200 rpm / min for 2 h to obtain a pre-emulsion;

[0060] Step B, in a nitrogen atmosphere, to a four-necked flask 2 equipped with an agitator, a nitrogen inlet tube, a condenser, and a separatory funnel, 200g of anhydrous ethanol was added as a solvent, 10g of modified nano-calcium carbonate was added, and then the remaining 0.5g of sodium dodecylbenzenesulfonate, 10g of deionized water, 0.417g of trifluoroethyl methacrylate, 0.833g of 2-acrylamide-2-methylpropanesulfonic acid AMPS and 1.25g of acrylic acid AA were added and mixed, the pH value of the solution was adjusted to 7 with aqueous ammonia, and finally 1.0g of potassium persulfate was added. After stirring and reacting for 2h at a stirring speed of 1500rpm / min under the condition of a water bath heating temperature of 75°C, the pre-emulsion obtained in step A was added dropwise and the reaction was continued for 4h to obtain a double-thin nano plugging agent for drilling fluid.

[0061] Example 2

[0062] This embodiment provides a nanometer-sized ampholyte for drilling fluid. The preparation method of the nanometer-sized ampholyte for drilling fluid is as follows:

[0063] (1) Surface modification of nano calcium carbonate:

[0064] Step a: In beaker 1, 10 g of nano-calcium carbonate (average particle size 100 nm), 200 mL of anhydrous ethanol, 3.0 mL of ammonia water, and 4 mL of water were added to prepare a nano-calcium carbonate slurry in proportion. After ultrasonic dispersion for 30 minutes, the slurry was transferred to a four-necked flask 1 equipped with a stirrer, a nitrogen inlet tube, a condenser, and a separatory funnel.

[0065] Step b: In beaker 2, add 1.5 mL of γ-methacryloxypropyltrimethoxysilane, 10.5 mL of anhydrous ethanol, and 0.45 mL of water, and ultrasonically disperse for 20 minutes to fully hydrolyze the γ-methacryloxypropyltrimethoxysilane. Transfer the fully hydrolyzed silane coupling agent solution to a separatory funnel;

[0066] Step c, under the condition of a water bath heating temperature of 65°C, in a nitrogen atmosphere, using the separatory funnel in step b to dropwise add the fully hydrolyzed γ-methacryloxypropyltrimethoxysilane to the four-necked flask 1 containing the nano-calcium carbonate solid slurry in step a, stirring at a stirring rate of 700 rpm / min for 5 hours, repeatedly filtering and washing with anhydrous ethanol, and then drying at a temperature of 60°C to 65°C for 8 hours to obtain modified nano-calcium carbonate;

[0067] (2) Under the condition of adding an initiator, the modified nano-calcium carbonate and the reaction monomer are mixed and reacted:

[0068] Step A: In a nitrogen atmosphere, 1.2 g of octylphenol polyoxyethylene ether, 30 g of deionized water, 3.6 g of hexafluorobutyl methacrylate, 5.4 g of 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and 9.1 g of acrylic acid (AA) were mixed and pre-emulsified at a stirring rate of 1000 rpm / min for 1.5 h to obtain a pre-emulsion;

[0069] Step B, in a nitrogen atmosphere, to a four-necked flask 2 equipped with an agitator, a nitrogen inlet tube, a condenser tube, and a separatory funnel, 200g of anhydrous ethanol was added as a solvent, 10g of modified nano-calcium carbonate was added, and then the remaining 0.3g of octylphenol polyoxyethylene ether, 10g of deionized water, 0.4g of hexafluorobutyl methacrylate, 0.6g of 2-acrylamide-2-methylpropanesulfonic acid AMPS and 0.9g of acrylic acid AA were added and mixed, the pH value of the solution was adjusted to 7 with aqueous ammonia, and finally 0.8g of potassium persulfate was added. After the reaction was stirred at a stirring speed of 1500rpm / min for 1h in a water bath heating temperature of 80°C, the pre-emulsion obtained in step A was added dropwise and the reaction was continued for 4h to obtain a double-thin nano plugging agent for drilling fluid.

[0070] Example 3

[0071] This embodiment provides a nanometer-sized ampholyte for drilling fluid. The preparation method of the nanometer-sized ampholyte for drilling fluid is as follows:

[0072] (1) Surface modification of nano calcium carbonate:

[0073] Step a: In beaker 1, 10 g of nano-calcium carbonate (average particle size of 150 nm), 220 mL of anhydrous ethanol, 3.0 mL of ammonia water, and 5 mL of water were added to prepare a nano-calcium carbonate solid slurry in proportion. After ultrasonic dispersion for 30 min, the slurry was transferred to a four-necked flask 1 equipped with a stirrer, a nitrogen inlet tube, a condenser, and a separatory funnel.

[0074] Step b: In beaker 2, add 0.5 mL of 3-acryloxypropyltriethoxysilane, 2.5 mL of anhydrous ethanol and 0.1 mL of water, and ultrasonically disperse for 20 minutes to fully hydrolyze the 3-acryloxypropyltriethoxysilane. Transfer the fully hydrolyzed silane coupling agent solution to a separatory funnel;

[0075] Step c, under the condition of a water bath heating temperature of 80° C., in a nitrogen atmosphere, using the separatory funnel in step b, dropwise adding fully hydrolyzed 3-acryloxypropyltriethoxysilane to the four-necked flask 1 containing the nano-calcium carbonate solid slurry in step a, stirring at a stirring rate of 800 rpm / min for 3 hours, repeatedly filtering and washing with anhydrous ethanol, and then drying at a temperature of 60° C. to 65° C. for 8 hours to obtain modified nano-calcium carbonate;

[0076] (2) Under the condition of adding an initiator, the modified nano-calcium carbonate and the reaction monomer are mixed and reacted:

[0077] Step A: In a nitrogen atmosphere, 0.4 g of sodium lauryl sulfate, 0.4 g of nonylphenol polyoxyethylene ether, 20 g of deionized water, 2.967 g of dodecafluoroheptyl methacrylate, 3.956 g of 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and 5.934 g of acrylic acid (AA) were mixed and pre-emulsified at a stirring rate of 800 rpm / min for 1 hour to obtain a pre-emulsion;

[0078] Step B, in a nitrogen atmosphere, to a four-necked flask 2 equipped with a stirrer, a nitrogen inlet tube, a condenser, and a separatory funnel, 200g of anhydrous ethanol was added as a solvent, 10g of modified nano-calcium carbonate was added, and the remaining 0.1g of sodium lauryl sulfate, 0.1g of nonylphenol polyoxyethylene ether, 10g of deionized water, 0.330g of dodecafluoroheptyl methacrylate, 0.440g of 2-acrylamide-2-methylpropanesulfonic acid AMPS and 0.660g of acrylic acid AA were added and mixed, the pH value of the solution was adjusted to 8 with aqueous ammonia, and finally 0.286g of azobisisobutyronitrile was added. After stirring at a water bath temperature of 70°C and a stirring speed of 1500rpm / min for 1h, the pre-emulsion obtained in step A was added dropwise and the reaction was continued for 3h to obtain a double-repellent nano plugging agent for drilling fluid.

[0079] Comparative Example 1

[0080] This embodiment provides a nano plugging agent for drilling fluid

[0081] The preparation method of Example 1 was followed, except that 12.5 g of trifluoroethyl methacrylate in total in Example 1 was replaced by 12.5 g of methyl acrylate, and other conditions remained unchanged.

[0082] Comparative Example 2

[0083] This embodiment provides a nano plugging agent for drilling fluid

[0084] The preparation method of Example 1 was followed, except that AMPS monomer was not added and other conditions remained unchanged.

[0085] Experimental example

[0086] In order to further illustrate the advancement of the nano-blocking agents for drilling fluid prepared in Examples 1 to 3 of the present invention and the nano-blocking agents for drilling fluid prepared in Comparative Examples 1 to 2, the following tests were performed:

[0087] Test Example 1

[0088] Surface tension evaluation: The amphiphobic nano-plugging agents for drilling fluid prepared in Examples 1-3 of the present invention and the nano-plugging agents for drilling fluid prepared in Comparative Examples 1-2 were prepared in water to prepare solutions of different concentrations. The surface tension of the amphiphobic nano-plugging agents for drilling fluid prepared in different concentrations was measured at a temperature of 25°C using the platinum plate method (for details, see the method described in GB / T18396-2001). The results are shown in Table 1.

[0089] Table 1

[0090]

[0091] As can be seen from Table 1, the amphiphobic nano plugging agents for drilling fluid prepared in Examples 1-3 of the present invention have strong surface activity and can effectively reduce the surface tension of deionized water. In particular, when the amphiphobic nano plugging agent for drilling fluid prepared in Example 1 is formulated to a concentration of less than 0.3%, the surface tension of deionized water can be reduced to below 13.9 mN / m; the nano plugging agents for drilling fluid prepared in Comparative Examples 1-2 have weaker activity, especially in Comparative Example 1, which lacks the fluorine-containing short carbon chain acrylate, and the prepared plugging agent has an unsatisfactory effect in reducing the surface tension of deionized water.

[0092] Test Example 2

[0093] Hydrophobicity and oleophobicity evaluation: The double-repellent nano plugging agents for drilling fluids prepared in Examples 1-3 of the present invention and the nano plugging agents for drilling fluids prepared in Comparative Examples 1-2 were respectively prepared into 0.3% aqueous solutions, and artificial cores were placed therein and soaked at a temperature of 150°C for 8 hours. The cores were taken out, cooled and dried, and then the contact angles θ of the oil phase and the water phase on the surface of the core were measured using a contact angle meter (model JC2000D3 contact angle meter from Shanghai Zhongchen Digital Technology Equipment Co., Ltd.). o and θ w , the results are shown in Table 2, where the oil phase is n-hexadecane and the water phase is distilled water;

[0094] Table 2

[0095]

[0096] It can be seen from the data in Table 2 that the amphiphobic nano plugging agents for drilling fluid prepared in Examples 1-3 of the present invention can make the rock surface have strong hydrophobicity and oleophobicity, achieving a surface amphiphobic effect; the nano plugging agents for drilling fluid prepared in Comparative Examples 1-2 have poor surface amphiphobic properties, especially in Comparative Example 1, which lacks the fluorine-containing short carbon chain acrylate, and the prepared plugging agent does not have hydrophobic and oleophobic properties.

[0097] Test Example 3

[0098] Plugging performance evaluation: Referring to GB16783.1-2014 "Field Test of Drilling Fluids in the Petroleum and Natural Gas Industry Part 1: Water-Based Drilling Fluids", the viscosity, fluid loss reduction, and plugging performance of the dual-repellent nano-plugging agents for drilling fluids prepared in Examples 1-3 of the present invention and the nano-plugging agents for drilling fluids prepared in Comparative Examples 1-2 were evaluated in a 6 wt % bentonite-based slurry. The plugging fluid loss was measured using an OFITE plugging filter loss meter under test conditions of 150° C., 21 MPa pressure, a filter disc model 170-55, a pore size of 3 μm, and a permeability of 400 mD. The test sample was a 6 wt % bentonite-based slurry containing 3 wt % of the dual-repellent nano-plugging agent for drilling fluids of the present invention. The test results are shown in Table 3 below.

[0099] Table 3

[0100]

[0101] As can be seen from the data in Table 3, when 3 wt % of the amphiphobic nano plugging agents for drilling fluid prepared in Examples 1-3 of the present invention were added to 6 wt % of the bentonite-based slurry, the viscosity of the test sample increased, and the fluid loss reduction effect was obvious; and after aging at a temperature of 150° C. for 16 h, it still had good fluid loss reduction and plugging effects. The nano plugging effects for drilling fluid prepared in Comparative Examples 1-2 were poor, especially in Comparative Example 2. Without the addition of AMPS monomer, the temperature resistance of the plugging agent was greatly reduced. After aging at 150° C. for 16 h, the apparent viscosity decreased, the plugging fluid loss increased significantly, and the plugging effect was poor.

[0102] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation of the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for preparing a double-repellent nano plugging agent for drilling fluid, characterized in that: include: Nano-calcium carbonate is surface-modified using a silane coupling agent, and then the modified nano-calcium carbonate is mixed and reacted with reactive monomers under the condition of adding an initiator to prepare an amphiphobic nano-plugging agent for drilling fluid; the reactive monomers are fluorine-containing short carbon chain acrylate, 2-acrylamide-2-methylpropanesulfonic acid and acrylic acid; The fluorine-containing short carbon chain acrylate is any one of trifluoroethyl methacrylate, hexafluorobutyl methacrylate, and dodecafluoroheptyl methacrylate; The silane coupling agent is an unsaturated hydrocarbon alkoxysilane; The mass ratio of the modified nano-calcium carbonate to the reaction monomer is (4-7):

10.

2. The preparation method according to claim 1, characterized in that The modified nano-calcium carbonate is grafted onto a copolymer of fluorine-containing short carbon chain acrylate, 2-acrylamide-2-methylpropanesulfonic acid and acrylic acid.

3. The preparation method according to claim 1, characterized in that The surface modification of nano-calcium carbonate using a silane coupling agent comprises: preparing a nano-calcium carbonate solid slurry and a silane coupling agent solution respectively, adding the silane coupling agent solution dropwise to the nano-calcium carbonate solid slurry under a nitrogen atmosphere and heating conditions, stirring and reacting, and obtaining modified nano-calcium carbonate; And / or, the modified nano-calcium carbonate is mixed with the reaction monomer under the condition of adding an initiator, and the reaction comprises: Step A, in a nitrogen atmosphere, mixing a first portion of the mass of the emulsifier aqueous solution with a first portion of the mass of the reactive monomer, and stirring to obtain a pre-emulsion; Step B: In a nitrogen atmosphere, anhydrous ethanol, modified nano-calcium carbonate, the remaining mass of the emulsifier aqueous solution and the remaining mass of the reaction monomer are mixed, an initiator is added, and after heating and stirring, the pre-emulsion obtained in step A is added dropwise to continue the reaction to obtain an amphiphobic nano plugging agent for drilling fluid.

4. The preparation method according to any one of claims 1 to 3, characterized in that The mass ratio of fluorine-containing short carbon chain acrylate, 2-acrylamide-2-methylpropanesulfonic acid and acrylic acid in the reaction monomer is (10-30): (20-40): (30-60); And / or, the unsaturated hydrocarbon alkoxysilane is any one of vinyltriethoxysilane, vinyltrimethoxysilane, vinyltributoxysilane, γ-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, and 3-acryloxypropyltrimethoxysilane; And / or, the ratio of the amount of the silane coupling agent to the amount of nano-calcium carbonate is (0.5-2.5) mL:10 g.

5. The preparation method according to any one of claims 1 to 3, characterized in that The average particle size of the modified nano calcium carbonate is 70-150 nm.

6. The preparation method according to claim 3, characterized in that The nano-calcium carbonate solid slurry is prepared by mixing nano-calcium carbonate, anhydrous ethanol, ammonia water and water in a ratio of 1 g: (19-22) mL: (0.25-0.30) mL: (0.3-0.5) mL and then ultrasonically dispersing the mixture. And / or, the silane coupling agent solution is prepared by mixing the silane coupling agent, anhydrous ethanol and water in a volume ratio of 1:(5-10):(0.2-0.4) and then ultrasonically dispersing the mixture; And / or, the heating temperature during the surface modification process of the nano-calcium carbonate is 65-80°C; And / or, the stirring speed during the surface modification process of the nano-calcium carbonate is 600-800 rpm / min, and the stirring time is 3-7 hours; And / or, the surface modification process of the nano-calcium carbonate further includes filtering with anhydrous ethanol, washing, and drying after the stirring reaction.

7. The preparation method according to claim 6, characterized in that The nano-calcium carbonate solid slurry is prepared by mixing nano-calcium carbonate, anhydrous ethanol, ammonia water and water in a ratio of 1 g: (19-22) mL: (0.25-0.30) mL: (0.3-0.5) mL and then ultrasonically dispersing the mixture; the ultrasonic dispersion lasts for 25-40 minutes; And / or, the silane coupling agent solution is prepared by mixing the silane coupling agent, anhydrous ethanol and water in a volume ratio of 1: (5-10): (0.2-0.4) and then ultrasonically dispersing the mixture; the ultrasonic dispersion lasts for 15-25 minutes; And / or, the stirring speed during the surface modification process of the nano-calcium carbonate is 700-800 rpm / min; And / or, the drying temperature is 60°C±5°C, and the drying time is 6-8 hours.

8. The preparation method according to claim 7, characterized in that The nano-calcium carbonate solid slurry is prepared by mixing nano-calcium carbonate, anhydrous ethanol, ammonia water and water in a ratio of 1 g: (19-22) mL: (0.25-0.30) mL: (0.3-0.5) mL and then ultrasonically dispersing the mixture; the ultrasonic dispersion lasts for 30 minutes; And / or, the silane coupling agent solution is prepared by mixing the silane coupling agent, anhydrous ethanol and water in a volume ratio of 1: (5-10): (0.2-0.4) and then ultrasonically dispersing the mixture; the ultrasonic dispersion is performed for 20 minutes; And / or, the drying time is 8 hours.

9. The preparation method according to claim 3, characterized in that The mass ratio of the first portion of the emulsifier aqueous solution to the remaining mass of the emulsifier aqueous solution is (2-9): (1-3); the mass ratio of the first portion of the reaction monomer to the remaining mass of the reaction monomer is (7-9): (0.5-2); and / or, the mass ratio of emulsifier to water in the emulsifier aqueous solution is 1:(20-30); and / or, the amount of the emulsifier is 0.05-0.2 of the mass of the reaction monomer; And / or, the emulsifier is one or a mixture of any proportions of disodium dodecyl diphenyl ether sulfonate, sodium dodecylbenzene sulfonate, sodium lauryl sulfate, octylphenol polyoxyethylene ether, and nonylphenol polyoxyethylene ether; And / or, in step A, the stirring rate is 800-1200 rpm / min, and the stirring time is 1-2 h; And / or, in step B, the mass ratio of the modified nano-calcium carbonate to anhydrous ethanol is (1-3): (15-30); And / or, in step B, the heating temperature is 70°C-80°C; And / or, in step B, the stirring rate is 1200-1800 rpm / min, and the stirring time is 1-2 h; And / or, in step B, the reaction is continued for 3-4 hours.

10. The preparation method according to claim 9, characterized in that The mass ratio of the first part of the mass of the emulsifier aqueous solution to the remaining mass of the emulsifier aqueous solution is (2-4):1; the mass ratio of the first part of the mass of the reaction monomer to the remaining mass of the reaction monomer is 9:1; and / or, the amount of the emulsifier is 0.05-0.1 of the mass of the reaction monomer; And / or, the emulsifier is sodium dodecylbenzenesulfonate or octylphenol polyoxyethylene ether or a mixture of sodium lauryl sulfate and nonylphenol polyoxyethylene ether in a mass ratio of 1:1; And / or, in step B, the mass ratio of the modified nano-calcium carbonate to anhydrous ethanol is 1:20; And / or, in step B, the stirring rate is 1500 rpm / min.

11. The preparation method according to claim 3, characterized in that In the step B, before adding the initiator, the pH value of the solution is further adjusted; and / or, the pH value is adjusted with aqueous ammonia; and / or, the amount of the initiator is 0.02-0.04 of the mass of the reaction monomer; And / or, the initiator is potassium persulfate or azobisisobutyronitrile.

12. The preparation method according to claim 11, characterized in that The pH value is 7-8.

13. An ambiphobic nano plugging agent for drilling fluid obtained by the preparation method according to any one of claims 1 to 12.

14. Use of the amphiphobic nano plugging agent for drilling fluid according to claim 13 in the field of drilling fluid.

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