A modified nano zinc oxide plugging agent and oil-based drilling fluid

Abstract

The invention discloses a modified nano zinc oxide plugging agent and an oil-based drilling fluid, belonging to the field of oil and gas field drilling technology, wherein the modified nano zinc oxide plugging agent is a nano-scale material prepared by using nano zinc oxide of 20 40 nm levels, a silane coupling agent containing amino groups, a polycarboxyl compound, a primary alcohol compound containing an olefinic bond, an olefin compound containing a benzene ring, an initiator and a cross-linking agent as raw materials. The particle size distribution of the modified nano zinc oxide of the present invention is between 60 320 nm, which can effectively plug the nano-scale cracks in the mud shale formation, stabilize the well wall, and prevent the occurrence of well collapse accidents. And the oil-based drilling fluid used in the present invention has good performance in terms of rheology, stability and plugging under mud shale formation conditions.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas field drilling and relates to a modified nano zinc oxide plugging agent and an oil-based drilling fluid. Background Art

[0002] With the transformation and upgrading of industrial structures and the growing demand for clean energy, shale gas production is expected to continue to grow. However, shale gas development still faces challenges, particularly the poor stability of horizontal wellbore sections, a key technology for shale gas development. Many factors contribute to horizontal wellbore instability in shale gas reservoirs, including the unique formation characteristics of shale gas and the hydraulic wedge effect caused by drilling fluid penetration.

[0003] Shale formations are extremely well-developed with weak structures such as nanoscale microcracks and bedding. During drilling, drilling fluid filtrate preferentially intrudes into the shale along these weak structures, causing intense local hydration and reducing rock strength. Furthermore, shale has extremely low porosity and permeability. Even a small amount of filtrate intrusion can significantly increase pore pressure near the wellbore wall, weakening the effective mechanical support provided by the fluid column pressure, and potentially leading to wellbore collapse and instability. However, the asphalt and polyol plugging and anti-collapse materials commonly used in drilling fluids have a particle size of micrometers, making it difficult for them to penetrate the nanoscale pore structure of shale and form a tight sealing layer. Summary of the Invention

[0004] The purpose of the present invention is to provide a modified nano zinc oxide plugging agent and an oil-based drilling fluid, which solves the problem of wellbore instability caused by the inability of conventional plugging agents to effectively plug nano cracks in shale.

[0005] The technical solution adopted in the present invention is as follows:

[0006] A modified nano zinc oxide plugging agent is a nano-scale material prepared from nano zinc oxide, an amino-containing silane coupling agent, a polycarboxyl compound, an olefinic primary alcohol compound, an olefinic olefin compound containing a benzene ring, an initiator and a cross-linking agent as raw materials.

[0007] The present invention uses nano zinc oxide as the main material. Nano zinc oxide has extremely high specific surface area and chemical activity, providing a good physical and chemical basis for the plugging agent; the amino-containing silane coupling agent can form a chemically bonded organic layer on the surface of the nano zinc oxide, thereby improving the compatibility of the nano zinc oxide with organic matrices or other materials, while enhancing its dispersibility and stability; the polycarboxyl functional groups can react with the hydroxyl groups on the surface of the nano zinc oxide to form stable chemical bonds, further improving the surface properties of the nano zinc oxide; the primary alcohol compounds containing olefinic bonds and the olefin compounds containing benzene rings combine with the active sites on the surface of the nano zinc oxide through free radical polymerization or addition reaction, giving the plugging agent more functionality, such as enhanced adhesion and improved weather resistance; the initiator triggers the cross-linking reaction of the cross-linking agent, thereby forming a three-dimensional network structure between the nano zinc oxide particles and with other components, thereby preparing a plugging agent with high strength and high stability. The nanometer-scale particle size of the present invention enables the plugging agent to penetrate deep into tiny pores and cracks, achieving efficient plugging. The high specific surface area and chemical activity enhance the interaction between the plugging agent and the substrate, improve the plugging effect, and can effectively plug nano-cracks in mud shale.

[0008] Furthermore, the modified nano zinc oxide plugging agent is prepared from nano zinc oxide, an amino-containing silane coupling agent, a polycarboxyl compound, an olefinic primary alcohol compound, an olefinic olefin compound containing a benzene ring, an initiator and a cross-linking agent as raw materials by the following method;

[0009] The specific steps of the method are as follows:

[0010] S1. Dry the nano-zinc oxide at 60-70° C. for 10-12 h, weigh 10-12 g of the dried nano-zinc oxide into a round-bottom flask, add 200 mL of ethanol and 200 mL of water into the flask, ultrasonically disperse for 40-50 min, add 0.3-0.36 g of a silane coupling agent, condense and reflux for 4-5 hours, centrifuge at 10,000 rpm for 10 min to obtain a precipitate, wash with ethanol, repeat 3-5 times, and vacuum dry for 20-24 h to obtain nano-zinc oxide modified with a silane coupling agent;

[0011] S2, adding 0.1-0.15 mol of the silane coupling agent-modified nano-zinc oxide obtained in step S1 and 50 mL of acetone solvent into a round-bottom flask, ultrasonically dispersing for 20-30 min, placing the mixture in a magnetic heating stirrer, and after heating to 70° C., adding 0.1-0.15 mol of a polycarboxyl compound and an initiator azobisisobutyronitrile, stirring and reacting for 2-3 h, and then centrifuging the mixture at a speed of 10000 r / min for 5 min to obtain a precipitate, soaking the precipitate in acetone for 16-20 h, washing it with ethanol 5 times, and finally drying it for 20-24 h to obtain a modified nano-zinc oxide containing an amide group and a carboxyl terminal functional group;

[0012] S3, dispersing 0.1-0.2 mol of the modified nano zinc oxide containing an amide group and a carboxyl terminal functional group obtained in step S2 with deionized water for 20-30 min, adding 0.2-0.3 mol of a primary alcohol compound containing an olefinic bond and a catalyst ionic liquid [BSO3HMIm]HSO4 in a three-necked flask, stirring at 100-110°C for 4-5 h, separating the product, vacuum drying for 2-4 h, washing with a saturated sodium chloride solution and a saturated sodium carbonate solution, and drying with anhydrous magnesium sulfate for 3-4 h to obtain a modified nano zinc oxide containing an olefinic bond and an ester functional group; the [BSO3HMIm]HSO4 is 1-butylsulfonic acid-3-methylimidazole hydrogen sulfate;

[0013] S4. Add 0.15-0.2 mol of the modified nano zinc oxide containing olefinic and ester functional groups obtained in step S3 and 50 mL of acetone solvent into a round-bottom flask, ultrasonically disperse for 20-30 min, heat to 70-80° C., add 0.3-0.4 mol of an olefin compound containing a benzene ring, an initiator azobisisobutyronitrile, and 0.02 mol of a cross-linking agent divinylbenzene, stir and react for 3-4 h, centrifuge at 10000 r / min for 5 min, soak the precipitate in acetone for 16-20 h, wash it with ethanol 3-5 times, and dry it in a drying oven to obtain a modified nano zinc oxide plugging agent after drying. The dried modified nano zinc oxide plugging agent is ground and sealed for storage.

[0014] Furthermore, the silane coupling agent is one of N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane, and N-β(aminoethyl)-γ-aminopropylmethyldiethoxysilane.

[0015] Furthermore, the polycarboxyl compound is one of suberic acid, cyclohexane-1,2,4,5-tetracarboxylic acid, and 3,3-dimethylglutaric acid.

[0016] Furthermore, the primary alcohol compound containing an olefinic bond is one of 5-hexen-1-ol, 7-octen-1-ol, and 9-decen-1-ol.

[0017] Furthermore, the benzene ring-containing olefin compound is one of p-1-butenyltoluene, 4-allylanisole, and 4-(3-methylphenyl)-butene.

[0018] An oil-based drilling fluid contains the modified nano zinc oxide plugging agent.

[0019] The modified nano zinc oxide plugging agent of the present invention can penetrate deep into tiny cracks and pores in shale formations to achieve effective plugging. This nanoscale matching makes the plugging more precise and efficient, reduces the entry of drilling fluid filtrate into the formation, and thus reduces the risk of formation damage and wellbore instability. In addition, the modified nano zinc oxide plugging agent of the present invention is a surface-modified material. The modified nanomaterial has an extremely high specific surface area, which increases its surface active sites, enhances its interaction with the formation rock, and improves the firmness and durability of the plugging.

[0020] Furthermore, an oil-based drilling fluid also includes the following components: base oil, primary emulsifier, auxiliary emulsifier, CaCl2 solution, organic soil, CaO, and fluid loss reducer.

[0021] Furthermore, the base oil is white oil, the primary emulsifier is oleic acid, the secondary emulsifier is Span-80 emulsifier, and the fluid loss reducer is oxidized asphalt.

[0022] Furthermore, an oil-based drilling fluid comprises the following components in parts by weight: 270 parts by weight of white oil, 6.75 parts by weight of oleic acid, 8.1 parts by weight of an auxiliary emulsifier Span-80, 80 mL of a 50% CaCl2 solution, 8.1 parts by weight of organic soil, 2.7 parts by weight of CaO, 5.4 parts by weight of a fluid loss reducer oxidized asphalt, and 1-4 parts by weight of a modified nano zinc oxide plugging agent.

[0023] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0024] 1. The nanometer-scale particle size of the modified nano-zinc oxide plugging agent of the present invention enables the plugging agent to penetrate deep into tiny pores and cracks, achieving efficient plugging. Its high specific surface area and chemical activity enhance the interaction between the plugging agent and the substrate, improving the plugging effect and effectively plugging nano-cracks in shale.

[0025] 2. The modified nano zinc oxide plugging agent of the present invention can penetrate deep into the tiny cracks and pores in the shale formation to achieve effective plugging. This nanoscale matching makes the plugging more precise and efficient, reduces the situation of drilling fluid filtrate entering the formation, thereby reducing the risk of formation damage and wellbore instability. In addition, the oil-based drilling fluid used in the present invention has good performance in terms of rheology, stability and plugging properties under the conditions of mud shale formations. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be considered as limiting the scope. A person of ordinary skill in the art can also derive other relevant drawings based on these drawings without inventive effort, among which:

[0027] Figure 1 This is the particle size distribution diagram of the modified nano zinc oxide plugging agent in Example 1;

[0028] Figure 2 This is the particle size distribution diagram of the modified nano zinc oxide plugging agent in Example 2;

[0029] Figure 3 This is the particle size distribution diagram of the modified nano zinc oxide plugging agent in Example 3;

[0030] Figure 4 This is the particle size distribution diagram of the modified nano zinc oxide plugging agent in Example 4; DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present invention and are not intended to limit the present invention. That is, the embodiments described herein are only some embodiments of the present invention, not all embodiments. Generally, the components of the embodiments of the present invention described and illustrated in the drawings herein may be arranged and designed in various different configurations.

[0032] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but is merely intended to represent selected embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0033] It should be noted that relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus comprising the element.

[0034] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0035] A modified nano zinc oxide plugging agent is a nano-scale material prepared from 20-40 nm nano zinc oxide, an amino-containing silane coupling agent, a polycarboxyl compound, an olefinic primary alcohol compound, an olefinic olefin compound containing a benzene ring, an initiator, and a cross-linking agent as raw materials and is prepared by the following method;

[0036] The specific steps of the method are as follows:

[0037] S1. Dry the nano-zinc oxide at 60-70° C. for 10-12 h, weigh 10-12 g of the dried nano-zinc oxide into a round-bottom flask, add 200 mL of ethanol and 200 mL of water into the flask, ultrasonically disperse for 40-50 min, add 0.3-0.36 g of a silane coupling agent, condense and reflux for 4-5 hours, centrifuge at 10,000 rpm for 10 min to obtain a precipitate, wash with ethanol, repeat 3-5 times, and vacuum dry for 20-24 h to obtain nano-zinc oxide modified with a silane coupling agent;

[0038] S2, adding 0.1-0.15 mol of the silane coupling agent-modified nano-zinc oxide obtained in step S1 and 50 mL of acetone solvent into a round-bottom flask, ultrasonically dispersing for 20-30 min, placing the mixture in a magnetic heating stirrer, and after heating to 70° C., adding 0.1-0.15 mol of a polycarboxyl compound and an initiator azobisisobutyronitrile, stirring and reacting for 2-3 h, and then centrifuging the mixture at a speed of 10000 r / min for 5 min to obtain a precipitate, soaking the precipitate in acetone for 16-20 h, washing it with ethanol 5 times, and finally drying it for 20-24 h to obtain a modified nano-zinc oxide containing an amide group and a carboxyl terminal functional group;

[0039] S3, dispersing 0.1-0.2 mol of the modified nano zinc oxide containing an amide group and a carboxyl terminal functional group obtained in step S2 with deionized water for 20-30 min, adding 0.2-0.3 mol of a primary alcohol compound containing an olefinic bond and a catalyst ionic liquid [BSO3HMIm]HSO4 in a three-necked flask, stirring at 100-110°C for 4-5 h, separating the product, vacuum drying for 2-4 h, washing with a saturated sodium chloride solution and a saturated sodium carbonate solution, and drying with anhydrous magnesium sulfate for 3-4 h to obtain a modified nano zinc oxide containing an olefinic bond and an ester functional group; the [BSO3HMIm]HSO4 is 1-butylsulfonic acid-3-methylimidazole hydrogen sulfate;

[0040] S4. Add 0.15-0.2 mol of the modified nano zinc oxide containing olefinic and ester functional groups obtained in step S3 and 50 mL of acetone solvent into a round-bottom flask, ultrasonically disperse for 20-30 min, heat to 70-80° C., add 0.3-0.4 mol of an olefin compound containing a benzene ring, an initiator azobisisobutyronitrile, and 0.02 mol of a cross-linking agent divinylbenzene, stir and react for 3-4 h, centrifuge at 10000 r / min for 5 min, soak the precipitate in acetone for 16-20 h, wash it with ethanol 3-5 times, and dry it in a drying oven to obtain a modified nano zinc oxide plugging agent after drying. The dried modified nano zinc oxide plugging agent is ground and sealed for storage.

[0041] The silane coupling agent is one of N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane and N-β(aminoethyl)-γ-aminopropylmethyldiethoxysilane.

[0042] The polycarboxyl compound is one of suberic acid, cyclohexane-1,2,4,5-tetracarboxylic acid and 3,3-dimethylglutaric acid.

[0043] The primary alcohol compound containing an olefinic bond is one of 5-hexene-1-ol, 7-octen-1-ol and 9-decen-1-ol.

[0044] The benzene ring-containing olefin compound is one of p-1-butenyltoluene, 4-allylanisole, and 4-(3-methylphenyl)-butene.

[0045] An oil-based drilling fluid contains the modified nano zinc oxide plugging agent.

[0046] An oil-based drilling fluid comprises the following components in parts by weight: 270 parts by weight of white oil, 6.75 parts by weight of oleic acid as a primary emulsifier, 8.1 parts by weight of Span-80 as an auxiliary emulsifier, 80 mL of a 50% CaCl2 solution, 8.1 parts by weight of organic soil, 2.7 parts by weight of CaO, 5.4 parts by weight of oxidized asphalt as a fluid loss reducer, and 1-4 parts by weight of a modified nano-zinc oxide plugging agent.

[0047] Example 1

[0048] The modified nano zinc oxide plugging agent provided in this embodiment is obtained by the following preparation method, the specific steps of which are as follows:

[0049] S1. Dry the nano-zinc oxide at 65° C. for 10 h, weigh 10 g of the dried nano-zinc oxide into a round-bottom flask, add 200 mL of ethanol and 200 mL of water into the flask, ultrasonically disperse for 40 min, add 0.3 g of N-(2-aminoethyl)-3-aminopropyltriethoxysilane, react under condensation and reflux for 5 hours, centrifuge at 10,000 rpm for 10 min to obtain a precipitate, wash with ethanol, repeat 5 times, and vacuum dry for 24 h to obtain nano-zinc oxide modified with a silane coupling agent;

[0050] S2, adding 0.1 mol of the silane coupling agent-modified nano-zinc oxide obtained in step S1 and 50 mL of acetone solvent into a round-bottom flask, ultrasonically dispersing for 20 min, placing the flask in a magnetic heating stirrer, and after heating to 70° C., adding 0.1 mol of suberic acid and initiator azobisisobutyronitrile, stirring and reacting for 3 h, and then centrifuging the precipitate at a speed of 10,000 r / min for 5 min to obtain a precipitate, soaking the precipitate in acetone for 20 h, washing it with ethanol 5 times, and finally drying it for 24 h to obtain a modified nano-zinc oxide containing an amide group and a carboxyl terminal functional group;

[0051] S3, dispersing 0.1 mol of the modified nano zinc oxide containing an amide group and a carboxyl terminal functional group obtained in S2 with deionized water for 20 min, adding 0.2 mol of 5-hexen-1-ol and the catalyst ionic liquid [BSO3HMIm]HSO4 in a three-necked flask, stirring at 100°C for 4 h, separating the product, vacuum drying for 2 h, washing with a saturated sodium chloride solution and a saturated sodium carbonate solution, and drying with anhydrous magnesium sulfate for 3 h to obtain a modified nano zinc oxide containing an olefinic bond and an ester functional group;

[0052] S4. Add 0.15 mol L S3 of the modified nano zinc oxide containing olefinic and ester functional groups and 50 mL of acetone solvent into a round-bottom flask, ultrasonically disperse for 20 minutes, heat to 70°C, add 0.3 mol 4-allyl anisole, initiator azobisisobutyronitrile and 0.02 mol cross-linking agent divinylbenzene, stir and react for 3 hours, centrifuge at 10000 r / min for 5 minutes, soak the precipitate in acetone for 16 hours, wash it with ethanol 3 times, and dry it in a drying oven to obtain the modified nano zinc oxide plugging agent after drying. Grind the dried sample and seal it for storage.

[0053] Example 2

[0054] The modified nano zinc oxide plugging agent provided in this embodiment is obtained by the following preparation method, the specific steps of which are as follows:

[0055] S1. Dry the nano-zinc oxide at 60° C. for 12 h, weigh 10 g of the dried nano-zinc oxide into a round-bottom flask, add 200 mL of ethanol and 200 mL of water to the flask, ultrasonically disperse for 45 min, add 0.3 g of N-β (aminoethyl) -γ-aminopropylmethyldimethoxysilane, react under condensation and reflux for 4 hours, and centrifuge at 10,000 rpm for 10 min to obtain a precipitate, wash with ethanol, repeat this process three times, and vacuum dry for 20 h to obtain nano-zinc oxide modified with a silane coupling agent;

[0056] S2, adding 0.1 mol of the silane coupling agent-modified nano-zinc oxide obtained in step S1 and 50 mL of acetone solvent into a round-bottom flask, ultrasonically dispersing for 20-30 min, placing it in a magnetic heating stirrer, and after heating to 70° C., adding 0.1 mol of cyclohexane-1,2,4,5-tetracarboxylic acid and initiator azobisisobutyronitrile, stirring and reacting for 2.5 h, and then centrifuging it at a speed of 10000 r / min for 5 min to obtain a precipitate, soaking the precipitate in acetone for 18 h, washing it with ethanol 5 times, and finally drying it for 21 h to obtain a modified nano-zinc oxide containing an amide group and a carboxyl terminal functional group;

[0057] S3, dispersing 0.1 mol of the modified nano zinc oxide containing an amide group and a carboxyl terminal functional group obtained in S2 with deionized water for 25 min, adding 0.2 mol of 7-octen-1-ol and the catalyst ionic liquid [BSO3HMIm]HSO4 in a three-necked flask, stirring at 100°C for 4 h, separating the product, vacuum drying for 3 h, washing with saturated sodium chloride solution and saturated sodium carbonate solution, and drying with anhydrous magnesium sulfate for 3 h to obtain modified nano zinc oxide containing olefinic and ester functional groups;

[0058] S4. Add 0.15 mol of the modified nano-zinc oxide containing olefinic and ester functional groups obtained in S3 and 50 mL of acetone solvent into a round-bottom flask, ultrasonically disperse for 20 min, heat to 75°C, add 0.3 mol of 4-allylanisole, initiator azobisisobutyronitrile and 0.02 mol of cross-linking agent divinylbenzene, stir and react for 3 minutes, centrifuge at 10000 r / min for 5 min, soak the precipitate in acetone for 17 h, wash it with ethanol 4 times, and dry it in a drying oven to obtain the modified nano-zinc oxide plugging agent after drying. Grind the dried sample and seal it for storage.

[0059] Example 3

[0060] The modified nano zinc oxide plugging agent provided in this embodiment is obtained by the following preparation method, the specific steps of which are as follows:

[0061] S1. Dry the nano-zinc oxide at 70° C. for 12 h, weigh 12 g of the dried nano-zinc oxide into a round-bottom flask, add 200 mL of ethanol and 200 mL of water to the flask, ultrasonically disperse for 50 min, add 0.36 g of N-β (aminoethyl) -γ-aminopropylmethyldiethoxysilane, react under condensation and reflux for 5 hours, centrifuge at 10,000 rpm for 10 min to obtain a precipitate, wash with ethanol, repeat 5 times, and vacuum dry for 24 h to obtain nano-zinc oxide modified with a silane coupling agent;

[0062] S2, adding 0.15 mol of the silane coupling agent-modified nano-zinc oxide obtained in step S1 and 50 mL of acetone solvent into a round-bottom flask, ultrasonically dispersing for 30 min, placing the flask in a magnetic heating stirrer, and after heating to 70°C, adding 0.15 mol of 3,3-dimethylglutaric acid and initiator azobisisobutyronitrile, stirring and reacting for 3 h, and then centrifuging at a speed of 10000 r / min for 5 min to obtain a precipitate, soaking the precipitate in acetone for 20 h, washing it with ethanol 5 times, and finally drying it for 24 h to obtain modified nano-zinc oxide containing an amide group and a carboxyl terminal functional group;

[0063] S3, dispersing 0.2 mol of the modified nano zinc oxide containing an amide group and a carboxyl terminal functional group obtained in S2 with deionized water for 30 min, adding 0.3 mol of 9-decene-1-ol and the catalyst ionic liquid [BSO3HMIm]HSO4 in a three-necked flask, stirring at 110°C for 5 h, separating the product, vacuum drying for 4 h, washing with saturated sodium chloride solution and saturated sodium carbonate solution, and drying with anhydrous magnesium sulfate for 4 h to obtain modified nano zinc oxide containing olefinic and ester functional groups;

[0064] S4. Add 0.2 mol of the modified nano zinc oxide containing olefinic and ester functional groups obtained in S3 and 50 mL of acetone solvent into a round-bottom flask, ultrasonically disperse for 30 min, heat to 80°C, add 0.4 mol of 4-(3-methylphenyl)-butene, initiator azobisisobutyronitrile and 0.02 mol of cross-linking agent divinylbenzene, stir and react for 4 h, centrifuge at 10000 r / min for 5 min, soak the precipitate in acetone for 20 h, wash it with ethanol 5 times, and dry it in a drying oven to obtain the modified nano zinc oxide plugging agent after drying. Grind the dried sample and seal it for storage.

[0065] Example 4

[0066] The modified nano zinc oxide plugging agent provided in this embodiment is obtained by the following preparation method, the specific steps of which are as follows:

[0067] S1. Dry the nano-zinc oxide at 65° C. for 11 h, weigh 11 g of the dried nano-zinc oxide into a round-bottom flask, add 200 mL of ethanol and 200 mL of water to the flask, ultrasonically disperse for 45 min, add 0.34 g of N-(2-aminoethyl)-3-aminopropyltriethoxysilane, react under condensation and reflux for 5 hours, and centrifuge at 10,000 rpm for 10 min to obtain a precipitate, wash with ethanol, repeat 4 times, and vacuum dry for 22 h to obtain nano-zinc oxide modified with a silane coupling agent;

[0068] S2, adding 0.12 mol of the silane coupling agent-modified nano-zinc oxide prepared in step S1 and 50 mL of acetone solvent into a round-bottom flask, ultrasonically dispersing for 25 min, placing the mixture in a magnetic heating stirrer, and after heating to 70° C., adding 0.12 mol of cyclohexane-1,2,4,5-tetracarboxylic acid and initiator azobisisobutyronitrile, stirring and reacting for 3 h, and then centrifuging the mixture at a speed of 10,000 r / min for 5 min to obtain a precipitate, soaking the precipitate in acetone for 18 h, washing it with ethanol 5 times, and finally drying it for 22 h to obtain a modified nano-zinc oxide containing an amide group and a carboxyl terminal functional group;

[0069] S3, dispersing 0.15 mol of the modified nano zinc oxide containing an amide group and a carboxyl terminal functional group obtained in S2 with deionized water for 25 min, adding 0.25 mol of 9-decene-1-ol and the catalyst ionic liquid [BSO3HMIm]HSO4 in a three-necked flask, stirring at 100-110°C for 4-5 h, separating the product, vacuum drying for 2-4 h, washing with saturated sodium chloride solution and saturated sodium carbonate solution, and drying with anhydrous magnesium sulfate for 3-4 h to obtain modified nano zinc oxide containing olefinic and ester functional groups;

[0070] S4. Add 0.16 mol of the modified nano zinc oxide containing olefinic and ester functional groups obtained in S3 and 50 mL of acetone solvent into a round-bottom flask, ultrasonically disperse for 25 minutes, heat to 75°C, add 0.35 mol of p-1-butenyltoluene, initiator azobisisobutyronitrile and 0.02 mol of cross-linking agent divinylbenzene, stir and react for 4 hours, centrifuge at 10000 r / min for 5 minutes, soak the precipitate in acetone for 20 hours, wash it with ethanol 4 times, and dry it in a drying oven to obtain the modified nano zinc oxide plugging agent after drying. Grind the dried sample and seal it for storage.

[0071] Test Example 1

[0072] Particle size test of modified nano zinc oxide plugging agent: The particle size of nano-microemulsion plugging agent was tested using BI-200SM laser scattering instrument produced by Brookhaven Instrument Company, USA. The particle size test results of modified nano zinc oxide plugging agent prepared in Examples 1-4 are as follows: Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 The particle size distribution of the modified nano zinc oxide plugging agent of the present invention is between 60-320 nm, indicating that the plugging agent synthesized by the present invention is nano-sized, and the particle size distribution range of the plugging agent is large, and it can effectively plug nano cracks of different nano sizes.

[0073] Test Example 2

[0074] Testing of drilling fluid rheology and water loss wall building performance:

[0075] This test example uses the following specific formula to illustrate the application of modified nano zinc oxide plugging agent;

[0076] Taking 270 parts by weight of white oil as a benchmark, this test example illustrates the oil-based drilling fluid formula by the following method. The specific oil-based drilling fluid (base slurry) formula is as follows: 270 parts by weight of white oil, 6.75 parts by weight of primary emulsifier oleic acid, 8.1 parts by weight of secondary emulsifier Span-80, 80 mL of 50% CaCl2 solution, 8.1 parts by weight of organic soil, 2.7 parts by weight of CaO, 5.4 parts by weight of oxidized asphalt as a fluid loss reducer, and 1-4 parts by weight of modified nano zinc oxide plugging agent.

[0077] The specific preparation process is as follows:

[0078] Take 270 parts by weight of 5# white oil in a high-stirring cup, then place it on a high-speed stirrer and stir at 10,000 rpm; add 6.75 parts by weight of oleic acid as a primary emulsifier and 6.75 parts by weight of Span-80 as a secondary emulsifier and stir for 10 minutes; add 8.1 parts by weight of organic soil and stir for 10 minutes; add 80 mL of 50% CaCl2 solution and stir for 10 minutes; add 5.4 parts by weight of oxidized asphalt as a fluid loss reducer and stir for 10 minutes; add 2.7 parts by weight of CaO and stir for 10 minutes;

[0079] After stirring, 0 parts by weight, 1 part by weight, 2 parts by weight, 3 parts by weight, and 4 parts by weight of the modified nano zinc oxide plugging agent prepared in Examples 1-4 were added to the oil-based drilling fluid, respectively. The modified nano zinc oxide plugging agent of one embodiment was added in four identical oil-based drilling fluids. Therefore, the modified nano zinc oxide plugging agent of one embodiment corresponded to four experimental oil-based drilling fluids, and the oil-based drilling fluid without the modified nano zinc oxide plugging agent was used as a blank experimental group.

[0080] According to the standard GB / T 16783.1-2014 "Field Testing of Drilling Fluids in the Petroleum and Natural Gas Industry Part 1: Oil-Based Drilling Fluids", the drilling fluids prepared in the steps and added with different mass fractions of plugging agents were tested for rheological properties and water loss wall formation before and after aging. The results are recorded in Table 1.

[0081] Table 1 Drilling fluid rheology and water loss wall building performance test results

[0082]

[0083] Note: AV—apparent viscosity, unit is mPa·s; PV—plastic viscosity, unit is mPa·s; YP—dynamic shear force, unit is Pa; API—normal temperature medium pressure filtration loss, unit is mL; HTHP—high temperature high pressure filtration loss, unit is mL.

[0084] The results shown in Table 1 indicate that, compared with drilling fluids without modified nano-zinc oxide plugging agents, the apparent viscosity and plastic viscosity of the drilling fluid gradually increase with increasing dosage of the modified nano-zinc oxide plugging agent, while the addition of the plugging agent has little effect on shear force. For drilling fluids aged at 150°C for 16 hours, the high-temperature and high-pressure filtration rate gradually decreases with increasing dosage of the modified nano-zinc oxide plugging agent, with the lowest high-temperature and high-pressure filtration loss at a dosage of 4 parts by mass. These results demonstrate that the modified nano-zinc oxide plugging agent exhibits excellent rheological properties and water loss-walling properties, effectively reducing high-temperature and high-pressure filtration loss in drilling fluids. It provides efficient plugging performance even in high-temperature environments, effectively preventing filtrate from entering the formation and improving wellbore stability.

[0085] Test Example 3

[0086] Drilling fluid plugging performance testing: Using artificial cores to simulate formations with sodium-micron fractures, the average flow rate of the drilling fluid system in the artificial cores was measured. The permeability of the artificial cores before and after the addition of the modified nano-zinc oxide plugging agent was calculated using the Darcy equation (K = QμL / (AΔP). This calculation yielded the plugging efficiency of the modified nano-zinc oxide plugging agent on the artificial cores and evaluated their plugging performance. Table 2 shows the plugging efficiency of the modified nano-zinc oxide plugging agent on the artificial cores. The plugging efficiency is calculated as (initial permeability - permeability after plugging) / initial permeability × 100%.

[0087] Table 2 Evaluation experimental data of artificial core plugging performance

[0088] name <![CDATA[Permeability after plugging / 10 -4 mD]]> Blockage rate (%) base slurry 25.20 - Base slurry + 1 part Example 1 16.20 35.71 Base slurry + 1 part Example 2 17.50 30.56 Base slurry + 1 part Example 3 15.90 36.90 Base slurry + 1 part Example 4 17.80 29.37 Base slurry + 2 parts of Example 1 12.10 51.98 Base slurry + 2 parts Example 2 13.20 47.62 Base slurry + 2 parts Example 3 11.30 55.16 Base slurry + 2 parts Example 4 13.20 47.62 Base slurry + 3 parts of Example 1 6.30 75.00 Base slurry + 3 parts Example 2 8.50 66.27 Base slurry + 3 parts Example 3 6.40 74.60 Base slurry + 3 parts Example 4 7.60 69.84 Base slurry + 4 parts Example 1 3.10 87.70 Base slurry + 4 parts of Example 2 5.60 77.78 Base slurry + 4 parts Example 3 3.50 86.11 Base slurry + 4 parts Example 4 5.40 78.57

[0089] The results shown in Table 2 show that compared with the base slurry without modified nano-zinc oxide plugging agent, the plugging rate of the core increased after adding different weight portions of modified nano-zinc oxide plugging agent, and when the modified nano-zinc oxide plugging agent was added at 4 weight portions, the plugging rate of the core reached more than 87%, which shows that the modified nano-zinc oxide plugging agent can effectively plug the micropores and prevent the drilling fluid from entering the core.

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions and improvements made by any technician familiar with the field within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A modified nano zinc oxide plugging agent, characterized in that: The modified nano zinc oxide plugging agent is a nano-scale material prepared by the following method using 20-40nm nano zinc oxide, amino-containing silane coupling agent, polycarboxyl compound, olefinic primary alcohol compound, benzene ring-containing olefin compound, initiator and cross-linking agent as raw materials; The silane coupling agent is one of N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane, and N-β(aminoethyl)-γ-aminopropylmethyldiethoxysilane; The polycarboxyl compound is one of suberic acid, cyclohexane-1,2,4,5-tetracarboxylic acid, and 3,3-dimethylglutaric acid; The primary alcohol compound containing an olefinic bond is one of 5-hexen-1-ol, 7-octen-1-ol, and 9-decen-1-ol; The olefin compound containing a benzene ring is one of p-1-butenyltoluene, 4-allylanisole, 4-(3-methylphenyl)-butene The specific steps of the method are as follows: S1. Dry the nano-zinc oxide at 60-70° C. for 10-12 h, weigh 10-12 g of the dried nano-zinc oxide into a round-bottom flask, add 200 mL of ethanol and 200 mL of water into the flask, ultrasonically disperse for 40-50 min, add 0.3-0.36 g of a silane coupling agent, condense and reflux for 4-5 hours, centrifuge at 10,000 rpm for 10 min to obtain a precipitate, wash with ethanol, repeat 3-5 times, and vacuum dry for 20-24 h to obtain nano-zinc oxide modified with a silane coupling agent; S2, adding 0.1-0.15 mol of the nano zinc oxide modified with the silane coupling agent in step S1 and 50 mL of acetone solvent into a round-bottom flask, ultrasonically dispersing for 20-30 min, placing it in a magnetic heating stirrer, and after heating to 70° C., adding 0.1-0.15 mol of a polycarboxyl compound and an initiator azobisisobutyronitrile, stirring and reacting for 2-3 h, and then centrifuging it at a speed of 10000 r / min for 5 min to obtain a precipitate, soaking the precipitate in acetone for 16-20 h, washing it with ethanol 5 times, and finally drying it for 20-24 h to obtain a modified nano zinc oxide containing an amide group and a carboxyl terminal functional group; S3, dispersing 0.1-0.2 mol of the modified nano zinc oxide containing an amide group and a carboxyl terminal functional group obtained in step S2 with deionized water for 20-30 min, adding 0.2-0.3 mol of a primary alcohol compound containing an olefinic bond and a catalyst ionic liquid [BSO3HMIm]HSO4 in a three-necked flask, stirring at 100-110°C for 4-5 h, separating the product, vacuum drying for 2-4 h, washing with a saturated sodium chloride solution and a saturated sodium carbonate solution, and drying with anhydrous magnesium sulfate for 3-4 h to obtain a modified nano zinc oxide containing an olefinic bond and an ester functional group; the [BSO3HMIm]HSO4 is 1-butylsulfonic acid-3-methylimidazole hydrogen sulfate; S4. Add 0.15-0.2 mol of the modified nano zinc oxide containing olefinic and ester functional groups obtained in step S3 and 50 mL of acetone solvent into a round-bottom flask, ultrasonically disperse for 20-30 min, heat to 70-80° C., add 0.3-0.4 mol of an olefin compound containing a benzene ring, an initiator azobisisobutyronitrile, and 0.02 mol of a cross-linking agent divinylbenzene, stir and react for 3-4 h, centrifuge at 10000 r / min for 5 min, soak the precipitate in acetone for 16-20 h, wash it with ethanol 3-5 times, and dry it in a drying oven to obtain a modified nano zinc oxide plugging agent after drying. The dried modified nano zinc oxide plugging agent is ground and sealed for storage.

2. An oil-based drilling fluid, characterized in that: Contains the modified nano zinc oxide plugging agent according to claim 1.

3. The oil-based drilling fluid according to claim 2, characterized in that: The following components are also included: base oil, primary emulsifier, auxiliary emulsifier, CaCl2 solution, organic soil, CaO, and fluid loss reducer.

4. The oil-based drilling fluid according to claim 3, characterized in that: The base oil is white oil, the main emulsifier is oleic acid, the auxiliary emulsifier is Span-80 emulsifier, and the fluid loss reducer is oxidized asphalt.

5. The oil-based drilling fluid according to claim 4, characterized in that: The invention comprises the following components in parts by weight: 270 parts by weight of white oil, 6.75 parts by weight of oleic acid, 8.1 parts by weight of auxiliary emulsifier Span-80, 80 mL of 50% CaCl2 solution, 8.1 parts by weight of organic soil, 2.7 parts by weight of CaO, 5.4 parts by weight of oxidized asphalt as a fluid loss reducer, and 1-4 parts by weight of a modified nano zinc oxide plugging agent.

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