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, and belongs to the technical field of oil and gas field drilling. The modified nano-zinc oxide blocking agent is a nano-scale material prepared by taking 20-40nm nano-zinc oxide, an amino-containing silane coupling agent, a polycarboxylic compound, an olefinic bond-containing primary alcohol compound, a benzene ring-containing olefin compound, an initiator and a cross-linking agent as raw materials. The particle size of the modified nano-zinc oxide ranges from 60 nm to 320 nm, nano-scale cracks in a shale stratum can be effectively blocked, the well wall is stabilized, and well collapse accidents are prevented. And the oil-based drilling fluid used in the invention has good rheological property, stability, plugging property and the like under the shale formation condition.

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 structure and the strong demand for clean energy, shale gas production will increase. However, there are still some difficulties in shale gas development, especially the key technology of shale gas development - the stability of the horizontal section of shale gas wellbore is still poor. There are many factors that cause the instability of the horizontal section of shale gas wellbore, including the unique formation characteristics of shale gas and the hydraulic wedge effect caused by drilling fluid penetration.

[0003] The nano-scale micro-cracks, bedding and other weak surface structures in shale formations are extremely developed. During the drilling process, the drilling fluid filtrate preferentially invades the interior of the shale along the micro-cracks, bedding and other weak surface structures, causing strong local hydration and reducing the rock strength. At the same time, the porosity and permeability of shale are extremely low. The invasion of a small amount of filtrate can significantly increase the pore pressure near the wellbore wall, weakening the effective mechanical support of the liquid column pressure on the wellbore wall, and easily leading to the collapse and instability of the wellbore wall. The particle size of the asphalt and polyol plugging and anti-collapse materials commonly used in drilling fluids is at the micron level, which makes it difficult to enter the nano-scale pore structure of shale and form a tight sealing plugging 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 by the present invention is as follows:

[0006] A modified nano zinc oxide plugging agent is a nano-scale material prepared from nano zinc oxide, amino-containing silane coupling agent, polycarboxyl compounds, olefinic primary alcohol compounds, benzene ring-containing olefin compounds, initiators and crosslinking agents as raw materials.

[0007] The invention uses nano zinc oxide as the main material. Nano zinc oxide has extremely high specific surface area and chemical activity, and provides 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 the organic matrix or other materials, and enhancing its dispersibility and stability. The polycarboxyl functional group can react with the hydroxyl group on the surface of the nano zinc oxide to form a stable chemical bond, thereby further improving the surface properties of the nano zinc oxide. The primary alcohol compound containing an olefin bond and the olefin compound containing a benzene ring are combined with the active site on the surface of the nano zinc oxide through free radical polymerization or addition reaction, thereby giving the plugging agent more functionality, such as enhancing adhesion and improving weather resistance. The initiator triggers the crosslinking reaction of the crosslinking agent, thereby forming a three-dimensional network structure between the nano zinc oxide particles and between the nano zinc oxide particles and 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 into tiny pores and cracks to achieve 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 mudstone.

[0008] Furthermore, the modified nano zinc oxide plugging agent is prepared from nano zinc oxide, amino-containing silane coupling agent, polycarboxyl compounds, olefinic primary alcohol compounds, benzene ring-containing olefin compounds, initiator and 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 10-12h, weigh 10-12g of the dried nano zinc oxide into a round-bottom flask, add 200mL of ethanol and 200mL of water into the flask, ultrasonically disperse for 40-50min, add 0.3-0.36g of silane coupling agent, condense and reflux for 4-5 hours, centrifuge at 10000r / min high-speed centrifuge for 10min to obtain a precipitate, wash with ethanol, repeat 3-5 times, and vacuum dry for 20-24h to obtain nano zinc oxide modified by 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 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, centrifuging 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 for 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 amide groups and terminal functional groups of carboxyl groups obtained in step S2 with deionized water for 20-30 min, adding 0.2-0.3 mol of primary alcohol compounds containing olefinic bonds and 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 bonds and ester functional groups; 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 bonds 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 to 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. Grind the dried modified nano zinc oxide plugging agent and seal it 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-hexene-1-ol, 7-octen-1-ol, and 9-decene-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 the tiny cracks and pores in the shale formation to achieve effective plugging. This nano-level matching makes the plugging more precise and efficient, reduces the situation where drilling fluid filtrate enters the formation, and thus reduces the risk of formation damage and well wall instability. In addition, the modified nano zinc oxide plugging agent of the present invention is a surface-modified material, and the modified nano material has an extremely high specific surface area, which increases its surface active sites, enhances the 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 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 filtrate reducer, and 1-4 parts by weight of 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 into tiny pores and cracks to achieve efficient plugging. Its 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;

[0025] 2. The modified nano zinc oxide plugging agent in the present invention can penetrate into the tiny cracks and pores in the shale formation to achieve effective plugging. This nano-level matching makes the plugging more accurate and efficient, reduces the situation where the drilling fluid filtrate enters the formation, thereby reducing the risk of formation damage and well wall instability. The oil-based drilling fluid used in the present invention has good performance in terms of rheology, stability and plugging properties under shale formation conditions. 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 regarded as limiting the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative work, 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 purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings herein can 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 claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making 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 such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

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

[0035] A modified nano zinc oxide plugging agent is a nano-scale material prepared from 20-40nm nano zinc oxide, amino-containing silane coupling agent, polycarboxyl compounds, olefinic primary alcohol compounds, benzene ring-containing olefin compounds, initiators and cross-linking agents 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 10-12h, weigh 10-12g of the dried nano zinc oxide into a round-bottom flask, add 200mL of ethanol and 200mL of water into the flask, ultrasonically disperse for 40-50min, add 0.3-0.36g of silane coupling agent, condense and reflux for 4-5 hours, centrifuge at 10000r / min high-speed centrifuge for 10min to obtain a precipitate, wash with ethanol, repeat 3-5 times, and vacuum dry for 20-24h to obtain nano zinc oxide modified by 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 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, centrifuging 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 for 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 amide groups and terminal functional groups of carboxyl groups obtained in step S2 with deionized water for 20-30 min, adding 0.2-0.3 mol of primary alcohol compounds containing olefinic bonds and 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 bonds and ester functional groups; 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 bonds 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 to 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. Grind the dried modified nano zinc oxide plugging agent and seal it 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 olefinic bonds is one of 5-hexene-1-ol, 7-octen-1-ol and 9-decene-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 a primary emulsifier, 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.

[0047] Example 1

[0048] A modified nano zinc oxide plugging agent provided in this embodiment is obtained by the following preparation method, the specific steps 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, condense and reflux for 5 hours, centrifuge at 10000 r / min high-speed centrifuge 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 by 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 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, 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 for 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 amide groups and terminal functional groups of carboxyl groups obtained in S2 with deionized water for 20 min, adding 0.2 mol of 5-hexene-1-ol and 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 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 bonds and ester functional groups;

[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, and perform ultrasonic dispersion for 20 min. After heating to 70°C, add 0.3 mol 4-allyl anisole, initiator azobisisobutyronitrile and 0.02 mol cross-linking agent divinylbenzene. After stirring for 3 h, centrifuge at 10000 r / min for 5 min. Soak the precipitate in acetone for 16 h, wash it with ethanol 3 times, and dry it in a drying oven to obtain the modified nano zinc oxide plugging agent. Grind the dried sample and seal it for storage.

[0053] Example 2

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

[0055] S1. Dry the nano zinc oxide at 60°C for 12h, weigh 10g of the dried nano zinc oxide into a round-bottom flask, add 200mL of ethanol and 200mL of water into the flask, ultrasonically disperse for 45min, add 0.3g of N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane, condense and reflux for 4h, centrifuge at 10000r / min high-speed centrifuge for 10min to obtain a precipitate, wash with ethanol, repeat 3 times, and vacuum dry for 20h to obtain nano zinc oxide modified by 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 in a magnetic heating stirrer, and 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, centrifuging 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 for 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 amide groups and terminal functional groups of carboxyl groups obtained in S2 with deionized water for 25 min, adding 0.2 mol of 7-octen-1-ol and 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 bonds 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, and perform ultrasonic dispersion for 20 min. After heating to 75°C, add 0.3 mol of 4-allylanisole, initiator azobisisobutyronitrile and 0.02 mol of cross-linking agent divinylbenzene. After stirring for 3 min, 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. Grind the dried sample and seal it for storage.

[0059] Example 3

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

[0061] S1. Dry the nano zinc oxide at 70°C for 12h, weigh 12g of the dried nano zinc oxide into a round-bottom flask, add 200mL of ethanol and 200mL of water into the flask, and after ultrasonic dispersion for 50min, add 0.36g of N-β (aminoethyl) -γ-aminopropylmethyldiethoxysilane, condense and reflux for 5 hours, centrifuge at 10000r / min high-speed centrifuge for 10min to obtain a precipitate, wash with ethanol, repeat 5 times, and vacuum dry for 24h to obtain nano zinc oxide modified by 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 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, 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 for 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;

[0063] S3, dispersing 0.2 mol of the modified nano zinc oxide containing amide groups and terminal functional groups of carboxyl groups obtained in S2 with deionized water for 30 min, adding 0.3 mol of 9-decene-1-ol and 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 bonds 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] A modified nano zinc oxide plugging agent provided in this embodiment is obtained by the following preparation method, the specific steps are as follows:

[0067] S1. Dry the nano zinc oxide at 65°C for 11 hours, weigh 11 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, and after ultrasonic dispersion for 45 minutes, add 0.34 g of N-(2-aminoethyl)-3-aminopropyltriethoxysilane, condense and reflux for 5 hours, centrifuge at 10000 r / min high-speed centrifuge for 10 minutes to obtain a precipitate, wash with ethanol, repeat 4 times, and vacuum dry for 22 hours to obtain nano zinc oxide modified by 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 in a magnetic heating stirrer, and heating to 70°C, adding 0.12 mol of cyclohexane-1,2,4,5-tetracarboxylic acid and initiator azobisisobutyronitrile, stirring for 3 h, and centrifuging 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 for 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 terminal functional group of a carboxyl group obtained in S2 with deionized water for 25 min, adding 0.25 mol of 9-decene-1-ol 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;

[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, and perform ultrasonic dispersion for 25 min. After heating to 75°C, add 0.35 mol of p-1-butenyltoluene, initiator azobisisobutyronitrile and 0.02 mol of cross-linking agent divinylbenzene. After stirring for 4 h, centrifuge at 10000 r / min for 5 min. Soak the precipitate in acetone for 20 h, wash it with ethanol 4 times, and dry it in a drying oven to obtain the modified nano zinc oxide plugging agent. 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 Instruments, 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-sized sizes.

[0073] Test Example 2

[0074] Drilling fluid rheology and water loss wall building performance testing:

[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 formula of oil-based drilling fluid by the following method. The specific formula of oil-based drilling fluid (base slurry) 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 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 filtrate reducer oxidized asphalt, 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 10000 rap; add 6.75 parts by weight of primary emulsifier oleic acid + 6.75 parts by weight of auxiliary emulsifier Span-80 and stir for 10 minutes; add 8.1 parts by weight of organic soil and stir for 10 minutes; add 80mL of 50% CaCl2 solution and stir for 10 minutes; add 5.4 parts by weight of oxidized asphalt as a filter loss reducer and stir for 10 minutes; add 2.7 parts by weight of CaO and stir for 10 minutes;

[0079] After stirring, 0 weight parts, 1 weight parts, 2 weight parts, 3 weight parts, and 4 weight parts of the modified nano zinc oxide plugging agent prepared in the above embodiments 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 same oil-based drilling fluids, respectively. Therefore, the modified nano zinc oxide plugging agent of one embodiment corresponds to four experimental oil-based drilling fluids, and the oil-based drilling fluid without the modified nano zinc oxide plugging agent is used as a blank experimental group.

[0080] According to the standard GB / T 16783.1-2014 "Field Test of Drilling Fluids in 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 rheology and water loss wall-forming properties before and after aging, and 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, in mPa·s; PV—plastic viscosity, in mPa·s; YP—dynamic shear force, in Pa; API—normal temperature and medium pressure filtration loss, in mL; HTHP—high temperature and high pressure filtration loss, in mL.

[0084] From the results shown in Table 1, it can be seen that compared with the drilling fluid without modified nano zinc oxide plugging agent, the apparent viscosity and plastic viscosity of the drilling fluid gradually increase with the increase of the amount of modified nano zinc oxide plugging agent, while the effect of the amount of the plugging agent on the shear force is small. After aging for 16 hours at 150°C, the high temperature and high pressure filtration volume of the drilling fluid gradually decreases with the increase of the amount of modified nano zinc oxide plugging agent, and the high temperature and high pressure filtration loss is the smallest when the amount is 4 parts by mass. In summary, it shows that the modified nano zinc oxide plugging agent has good rheological properties and water loss wall building properties, and can effectively reduce the high temperature and high pressure filtration loss of the drilling fluid, and can provide efficient plugging performance even in high temperature environments, effectively preventing the filtrate from entering the formation and improving the stability of the well wall.

[0085] Test Example 3

[0086] Drilling fluid plugging performance test: artificial cores are used to simulate formation sodium micron fracture formations, and the average flow rate of the drilling fluid system in the artificial cores is measured. The permeability K = QμL / (AΔP) of the artificial cores before and after the addition of the modified nano zinc oxide plugging agent is calculated by the Darcy formula, thereby calculating the plugging rate of the modified nano zinc oxide plugging agent on the artificial core and evaluating its plugging performance. Table 2 shows a record of the plugging effect of the modified nano zinc oxide plugging agent on the artificial core. The plugging rate is (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 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 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 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] From the results shown in Table 2, it can be seen 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 principle 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 material prepared from 20-40nm nano zinc oxide, amino-containing silane coupling agent, polycarboxyl compounds, olefinic primary alcohol compounds, benzene ring-containing olefin compounds, initiator and crosslinking agent as raw materials.

2. A modified nano zinc oxide plugging agent according to claim 1, characterized in that: The modified nano zinc oxide plugging agent is prepared by using nano zinc oxide, amino-containing silane coupling agent, polycarboxyl compounds, olefinic primary alcohol compounds, benzene ring-containing olefin compounds, initiator and crosslinking agent as raw materials; The specific steps of the method are as follows: S1. Dry the nano zinc oxide at 60-70°C for 10-12h, weigh 10-12g of the dried nano zinc oxide into a round-bottom flask, add 200mL of ethanol and 200mL of water into the flask, ultrasonically disperse for 40-50min, add 0.3-0.36g of silane coupling agent, condense and reflux for 4-5 hours, centrifuge at 10000r / min high-speed centrifuge for 10min to obtain a precipitate, wash with ethanol, repeat 3-5 times, and vacuum dry for 20-24h to obtain nano zinc oxide modified by silane coupling agent; S2, adding 0.1-0.15 mol of the nano zinc oxide modified by 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 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, centrifuging 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 for 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 amide groups and terminal functional groups of carboxyl groups obtained in step S2 with deionized water for 20-30 min, adding 0.2-0.3 mol of primary alcohol compounds containing olefinic bonds and 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 bonds and ester functional groups; 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 bonds 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 to 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. Grind the dried modified nano zinc oxide plugging agent and seal it for storage.

3. A modified nano zinc oxide plugging agent according to claim 2, characterized in that: The silane coupling agent is one of N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane and N-β(aminoethyl)-γ-aminopropylmethyldiethoxysilane.

4. A modified nano zinc oxide plugging agent according to claim 2, characterized in that: The polycarboxyl compound is one of suberic acid, cyclohexane-1,2,4,5-tetracarboxylic acid and 3,3-dimethylglutaric acid.

5. A modified nano zinc oxide plugging agent according to claim 2, characterized in that: The primary alcohol compound containing olefinic bonds is one of 5-hexene-1-ol, 7-octen-1-ol and 9-decene-1-ol.

6. A modified nano zinc oxide plugging agent according to claim 1, characterized in that: The benzene ring-containing olefin compound is one of p-1-butenyltoluene, 4-allylanisole, and 4-(3-methylphenyl)-butene.

7. An oil-based drilling fluid, characterized in that: A modified nano zinc oxide plugging agent comprising any one of claims 1 to 6.

8. The oil-based drilling fluid according to claim 7, characterized in that: The following components are also included: base oil, primary emulsifier, auxiliary emulsifier, CaCl2 solution, organic soil, CaO, and fluid loss reducer.

9. The oil-based drilling fluid according to claim 8, 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.

10. The oil-based drilling fluid according to claim 9, 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 filter loss reducer, and 1-4 parts by weight of modified nano zinc oxide plugging agent.

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