阅读说明：本技术 高密度抗高温油基钻完井液 (High-density high-temperature-resistant oil-based drilling and completion fluid ) 是由 孟虎 陈亚宁 谷团 冯伟 杨涛 王家锦 于 2019-11-07 设计创作，主要内容包括：本发明公开了一种高密度抗高温油基钻完井液,其按重量份计主要包括如下组分：基油80～100份,有机土0.5～6份,乳化剂1～2份,润湿剂2～3份,碱度调节剂1～5份,抗高温提切剂0.5～2份,抗高温降滤失剂1～3份以及加重剂30～60份；其中,所述加重剂为改性重晶石微粉,所述改性重晶石微粉的制备方法是,首先将碳微米管进行处理使其成为内亲水外亲油的碳微米管,然后将其与微米级得重晶石微粉混合超声,使所述内亲水外亲油的碳微米管包裹住重晶石微粉,制得本发明所述加重剂。本发明针对超深井、高温井、高密度井使用,最高可抗温240℃,密度最高可调整至2.6g/cm<Sup>3</Sup>,且性能优良。(The invention discloses a high-density high-temperature-resistant oil-based drilling and completion fluid which mainly comprises the following components in parts by weight: 80-100 parts of base oil, 0.5-6 parts of organic soil, 1-2 parts of emulsifier, 2-3 parts of wetting agent, 1-5 parts of alkalinity regulator, 0.5-2 parts of high-temperature resistant shear promoter, 1-3 parts of high-temperature resistant filtrate reducer and 30-60 parts of weighting agent; the weighting agent is modified barite micro powder, and the preparation method of the modified barite micro powder comprises the steps of firstly processing a carbon micron tube to form a carbon micron tube with hydrophilic inside and lipophilic outside, and then mixing the carbon micron tube with micron-sized barite micro powder for ultrasonic treatment to enable the carbon micron tube with hydrophilic inside and lipophilic outside to wrap the barite micro powder, so that the weighting agent is prepared. The invention is used for ultra-deep wells, high-temperature wells and high-density wells, can resist the temperature of 240 ℃ at most, and can adjust the density to 2.6g/cm at most 3 And has excellent performance.)

1. The high-density high-temperature-resistant oil-based drilling and completion fluid is characterized by mainly comprising the following components in parts by weight: 80-100 parts of base oil, 0.5-6 parts of organic soil, 1-2 parts of emulsifier, 2-3 parts of wetting agent, 1-5 parts of alkalinity regulator, 0.5-2 parts of high-temperature resistant shear promoter, 1-3 parts of high-temperature resistant filtrate reducer and 30-60 parts of weighting agent; the weighting agent is modified barite micro powder, and the preparation method of the modified barite micro powder comprises the following steps:

mixing a carbon micron tube and a strong oxidizing acid according to a weight ratio of 1 (0.1-10), carrying out ultrasonic treatment for 0.5-2 h, heating to 50-150 ℃, reacting for 12-24 h, filtering and washing until the mixture is neutral, carrying out vacuum drying, continuously adding thionyl chloride, wherein the weight of the thionyl chloride is 1-10 times that of the carbon micron tube, carrying out ultrasonic treatment for 0.5-2 h, heating to 30-100 ℃, reacting for 24-36 h under stirring and refluxing, carrying out suction filtration and washing, and thus obtaining an acylated carbon micron tube;

mixing the acylated carbon micron tube prepared in the step one with ethylene glycol according to the weight ratio of 1:50, repeatedly pumping and filling nitrogen for three times after sealing, carrying out ultrasonic treatment for 0.5-2 hours, heating to 30-120 ℃, reacting for 12-30 hours, carrying out suction filtration washing, vacuum drying, adding α -bromobutyryl bromide again, wherein the weight of the α -bromobutyryl bromide is 1-10 times that of the acylated carbon micron tube, repeatedly pumping and filling nitrogen for three times after sealing, carrying out ultrasonic treatment for 0.5-2 hours, heating to 50-150 ℃, reacting for 20-30 hours, carrying out suction filtration washing and vacuum drying to prepare the carbon micron tube with the initiation group on the surface;

step three, mixing the carbon micro-tube with the initiation group on the surface prepared in the step two with cuprous chloride, tetramethylethylenediamine and dichloromethane according to the weight ratio of 1 (0.01-1): (0.01-5): 0-50), sealing, charging nitrogen for 10-60 min, adding tert-butyl acrylate monomer, wherein the weight of the tert-butyl acrylate monomer is 1-20 times of that of the carbon micro-tube with the initiation group on the surface, continuing charging nitrogen for 10-60 min, heating to 80-150 ℃, stopping reaction after the system viscosity is obviously increased, precipitating, re-dissolving the precipitate, performing suction filtration washing, and performing vacuum drying to obtain the tert-butyl acrylate grafted carbon micro-tube with the polymerization degree of 5-200;

step four, mixing the tertiary butyl acrylate grafted carbon micron tube prepared in the step three with cuprous chloride, tetramethylethylenediamine and dichloromethane in a weight ratio of 1 (0.01-1): (0.01-5): 0-50), sealing, filling nitrogen for 10-60 min, adding a styrene monomer, wherein the weight of the styrene monomer is 1-5 times that of the tertiary butyl acrylate grafted carbon micron tube, continuing filling nitrogen for 10-60 min, heating to 80-150 ℃, stopping reaction after the system viscosity is obviously increased, precipitating, redissolving, suction filtering, washing and vacuum drying the precipitate to prepare the two-block polymer grafted carbon micron tube;

step five, mixing the two-block polymer grafted carbon micro-tube prepared in the step four with ethanol and hydrochloric acid according to the weight ratio of 1 (0.1-50) to (0.1-50), carrying out sealing reaction for 12-30 h, removing the solvent and the catalyst to obtain an inner hydrophilic and outer oleophilic type carbon micro-tube, mixing the inner hydrophilic and outer oleophilic type carbon micro-tube and barite micro-powder according to the weight ratio of 1:100 in a small amount of base oil, and carrying out ultrasonic treatment for 3-10 h to finally obtain the weighting agent.

2. The high-density high-temperature-resistant oil-based drilling and completion fluid as claimed in claim 1, wherein the carbon micro-pipe has a pipe wall thickness of 5 to 50nm and a pipe diameter of 100 to 500 μm.

3. The high density high temperature resistant oil-based drilling and completion fluid of claim 1, wherein the barite micropowder has an average particle size of 10 μm.

4. The high density high temperature resistant oil based drilling and completion fluid of claim 1, wherein the base oil is one or more of white oil, diesel oil, biodiesel oil or vegetable oil.

5. The high density high temperature resistant oil based drilling and completion fluid according to claim 1, wherein the emulsifier is one or more selected from coconut oil fatty acid diethanolamide, octyl phenol polyoxyethylene ether, oleic acid polyoxyethylene ether, stearic acid polyoxyethylene ether and fatty alcohol polyoxyethylene ether.

6. The high density, high temperature resistant oil-based completion drilling fluid of claim 1, wherein the wetting agent is one or more of alkyl benzene sulfonates, higher fatty amide sulfonates, oleic acid, naphthenic acid amides, which are commonly used in oil-based completion drilling fluids.

7. The high density high temperature resistant oil-based drilling and completion fluid of claim 1, wherein the alkalinity modifier is one or more of calcium oxide, sodium hydroxide or potassium hydroxide.

8. The high density high temperature resistant oil-based drilling and completion fluid of claim 1, wherein the high temperature resistant shear promoter comprises at least one of xanthan gum and sodium hydroxyethyl cellulose.

9. The high density high temperature resistant oil-based drilling and completion fluid of claim 1, wherein the high temperature resistant fluid loss additive comprises at least one of hydroxyethylcellulose, polyanionic cellulose, sulfonated phenolic resin, sulfonated lignite, lignite resin.

Technical Field

The invention relates to the technical field of petroleum engineering oilfield chemistry. More particularly, the present invention relates to a high density high temperature resistant oil-based drilling and completion fluid.

Background

With the continuous increase of the world demand on petroleum resources and the further development of conventional easy-to-extract petroleum resources, the exploration and development of petroleum resources are developed to high-difficulty areas such as high temperature and high pressure. The oil-based drilling and completion fluid is the first choice in the drilling process of complex structural wells such as ultra-deep wells, high-temperature wells, high-density wells and the like due to excellent properties such as inhibition, lubricity, thermal stability, pollution resistance, reservoir protection and the like.

The high-density drilling and completion fluid can press the stratum and maintain the well wall to stably prevent accidents such as overflow, blowout and the like, so the high-density drilling and completion fluid has very important significance for the exploration and development of deep stratum oil and gas reservoirs. The high temperature can cause the well drilling and completion fluid to ferment, thicken and lose efficacy, thereby causing the performance of the well drilling and completion fluid to be changed sharply, and the well drilling and completion fluid is not easy to adjust and control, and can cause the well drilling operation to be carried out normally in serious cases. When the conventional drilling and completion fluid using the barite as the weighting material works in a high-temperature high-pressure well, because the surface of the barite is hydrophilic and oleophobic, agglomeration and sedimentation are easily generated in the oil-based drilling and completion fluid, the barite which is settled at the bottom of the well increases the drilling difficulty, the drilling progress is seriously influenced, the barite is also wasted greatly, and the drilling cost is increased. Therefore, the method solves the problem of the sedimentation of the barite in the oil, and the barite can still be well dispersed in the oil for a long time, which is very important.

Disclosure of Invention

An object of the present invention is to solve at least the above problems and to provide at least the advantages described later.

The invention also aims to provide the high-density high-temperature-resistant oil-based drilling and completion fluid which is prepared by wrapping barite micro powder by using carbon micro tubes with hydrophilic property and oleophilic property inside as the weighting agent of the invention, so that the high-density oil-based drilling and completion fluid is suitable for ultra-deep wells, high-temperature wells and high-density wells.

To achieve these objects and other advantages in accordance with the present invention, there is provided a high density high temperature resistant oil-based drilling and completion fluid consisting essentially of, in parts by weight: 80-100 parts of base oil, 0.5-6 parts of organic soil, 1-2 parts of emulsifier, 2-3 parts of wetting agent, 1-5 parts of alkalinity regulator, 0.5-2 parts of high-temperature resistant shear promoter, 1-3 parts of high-temperature resistant filtrate reducer and 30-60 parts of weighting agent; the weighting agent is modified barite micro powder, and the preparation method of the modified barite micro powder comprises the following steps:

mixing a carbon micron tube and a strong oxidizing acid according to a weight ratio of 1 (0.1-10), carrying out ultrasonic treatment for 0.5-2 h, heating to 50-150 ℃, reacting for 12-24 h, filtering and washing until the mixture is neutral, carrying out vacuum drying, continuously adding thionyl chloride, wherein the weight of the thionyl chloride is 1-10 times that of the carbon micron tube, carrying out ultrasonic treatment for 0.5-2 h, heating to 30-100 ℃, reacting for 24-36 h under stirring and refluxing, carrying out suction filtration and washing, and thus obtaining an acylated carbon micron tube;

mixing the acylated carbon micron tube prepared in the step one with ethylene glycol according to the weight ratio of 1:50, repeatedly pumping and filling nitrogen for three times after sealing, carrying out ultrasonic treatment for 0.5-2 hours, heating to 30-120 ℃, reacting for 12-30 hours, carrying out suction filtration washing, vacuum drying, adding α -bromobutyryl bromide again, wherein the weight of the α -bromobutyryl bromide is 1-10 times that of the acylated carbon micron tube, repeatedly pumping and filling nitrogen for three times after sealing, carrying out ultrasonic treatment for 0.5-2 hours, heating to 50-150 ℃, reacting for 20-30 hours, carrying out suction filtration washing and vacuum drying to prepare the carbon micron tube with the initiation group on the surface;

step three, mixing the carbon micro-tube with the initiation group on the surface prepared in the step two with cuprous chloride, tetramethylethylenediamine and dichloromethane according to the weight ratio of 1 (0.01-1): (0.01-5): 0-50), sealing, charging nitrogen for 10-60 min, adding tert-butyl acrylate monomer, wherein the weight of the tert-butyl acrylate monomer is 1-20 times of that of the carbon micro-tube with the initiation group on the surface, continuing charging nitrogen for 10-60 min, heating to 80-150 ℃, stopping reaction after the system viscosity is obviously increased, precipitating, re-dissolving the precipitate, performing suction filtration washing, and performing vacuum drying to obtain the tert-butyl acrylate grafted carbon micro-tube with the polymerization degree of 5-200;

step four, mixing the tertiary butyl acrylate grafted carbon micron tube prepared in the step three with cuprous chloride, tetramethylethylenediamine and dichloromethane in a weight ratio of 1 (0.01-1): (0.01-5): 0-50), sealing, filling nitrogen for 10-60 min, adding a styrene monomer, wherein the weight of the styrene monomer is 1-5 times that of the tertiary butyl acrylate grafted carbon micron tube, continuing filling nitrogen for 10-60 min, heating to 80-150 ℃, stopping reaction after the system viscosity is obviously increased, precipitating, redissolving, suction filtering, washing and vacuum drying the precipitate to prepare the two-block polymer grafted carbon micron tube;

step five, mixing the two-block polymer grafted carbon micro-tube prepared in the step four with ethanol and hydrochloric acid according to the weight ratio of 1 (0.1-50) to (0.1-50), carrying out sealing reaction for 12-30 h, removing the solvent and the catalyst to obtain an inner hydrophilic and outer oleophilic type carbon micro-tube, mixing the inner hydrophilic and outer oleophilic type carbon micro-tube and barite micro-powder according to the weight ratio of 1:100 in a small amount of base oil, and carrying out ultrasonic treatment for 3-10 h to finally obtain the weighting agent.

Preferably, the carbon micron tube has a tube wall thickness of 5-50 nm and a tube diameter of 100-500 μm.

Preferably, the barite fine powder has an average particle size of 10 μm.

Preferably, the base oil is one or more of white oil, diesel oil, biodiesel oil or vegetable oil.

Preferably, the emulsifier is one or more of coconut oil fatty acid diethanolamide, octyl phenol polyoxyethylene ether, oleic acid polyoxyethylene ether, stearic acid polyoxyethylene ether or fatty alcohol polyoxyethylene ether.

Preferably, the wetting agent is one or more of alkyl benzene sulfonate, higher fatty amide sulfonate, oleic acid and naphthenic acid amide which are commonly used in oil-based drilling and completion fluids.

Preferably, the alkalinity regulator is one or more of calcium oxide, sodium hydroxide or potassium hydroxide.

Preferably, the high temperature resistant shear enhancing agent comprises at least one of xanthan gum and sodium hydroxyethyl cellulose.

Preferably, the high temperature resistant fluid loss additive comprises at least one of hydroxyethyl cellulose, polyanionic cellulose, sulfonated phenolic resin, sulfonated lignite and lignite resin.

The invention at least comprises the following beneficial effects:

firstly, acidizing and acylating a carbon micron tube, then treating the surface of the carbon micron tube to obtain the carbon micron tube with an initiation group on the surface, then initiating tert-butyl acrylate monomer polymerization by utilizing atom transfer radical polymerization reaction, and continuing initiating styrene monomer polymerization by utilizing atom transfer radical polymerization reaction to obtain a carbon micron tube grafted by two blocks of macromolecules, and then hydrolyzing inner layer poly tert-butyl acrylate to make the inner layer poly tert-butyl acrylate monomer hydrophilic, thus obtaining the carbon micron tube with hydrophilic and oleophilic inner and unique amphiphilic properties in a solvent;

secondly, the prepared inner hydrophilic and outer oleophylic carbon micron tubes are used as wrapping materials, and are mixed with barite micro powder to be ultrasonically dispersed in an oil medium, so that the inner hydrophilic and outer oleophylic carbon micron tubes fully wrap the barite micro powder to prepare the weighting agent, and the density of the system is increased;

thirdly, the invention is used for ultra-deep wells, high-temperature wells and high-density wells, the highest temperature resistance can be 240 ℃, and the density can be adjusted to 2.6g/cm ³The device can provide reliable performance guarantee for complex working conditions such as well killing, settlement, hole diameter expansion, borehole wall instability, sticking prevention and the like in the well drilling and completion process, and has excellent performance.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.

Detailed Description

The present invention is further described in detail below with reference to examples so that those skilled in the art can practice the invention with reference to the description.

It will be understood that terms such as "having," "including," and "comprising," as used herein, do not preclude the presence or addition of one or more other elements or groups thereof.

It is to be noted that the experimental methods described in the following embodiments are all conventional methods unless otherwise specified, and the reagents and materials are commercially available unless otherwise specified.

< example 1>

The high-density high-temperature-resistant oil-based drilling and completion fluid mainly comprises the following components in parts by weight: 100 parts of diesel oil, 3 parts of organic soil, 1 part of stearic acid polyoxyethylene ether, 2 parts of naphthenic acid amide, 3 parts of sodium hydroxide, 1 part of xanthan gum, 2 parts of hydroxyethyl cellulose and 50 parts of weighting agent; the weighting agent is modified barite micro powder, and the preparation method of the modified barite micro powder comprises the following steps:

step one, mixing a carbon micron tube with the tube wall thickness of 10nm and the tube diameter of 500 microns and concentrated nitric acid according to the weight ratio of 1:8, carrying out ultrasonic treatment for 0.5h, heating to 120 ℃, reacting for 24h, filtering and washing until the mixture is neutral, carrying out vacuum drying, continuously adding thionyl chloride, wherein the weight of the thionyl chloride is 6 times that of the carbon micron tube, carrying out ultrasonic treatment for 0.5h, heating to 60 ℃, carrying out reaction for 24h under stirring and refluxing, carrying out suction filtration and washing, and preparing an acylated carbon micron tube;

step two, mixing the acylated carbon micron tube prepared in the step one with ethylene glycol according to the weight ratio of 1:50, repeatedly pumping and filling nitrogen for three times after sealing, heating to 100 ℃ after ultrasonic treatment for 0.5h, reacting for 24h, pumping, filtering, washing, vacuum drying, adding α -bromobutyryl bromide with the same amount as the acylated carbon micron tube again, repeatedly pumping and filling nitrogen for three times after sealing, heating to 50 ℃ after ultrasonic treatment for 0.5h, reacting for 20h, pumping, washing and vacuum drying to prepare the carbon micron tube with the initiating group on the surface;

mixing the carbon microtube with the initiation group on the surface prepared in the second step with cuprous chloride, tetramethylethylenediamine and dichloromethane according to the weight ratio of 1:0.5:0.7:10, filling nitrogen for 10min after sealing, adding a tert-butyl acrylate monomer, wherein the weight of the tert-butyl acrylate monomer is 5 times that of the carbon microtube with the initiation group on the surface, continuing filling nitrogen for 10min, heating to 100 ℃, stopping reaction after the system viscosity is obviously increased, precipitating, redissolving the precipitate, performing suction filtration and washing, and performing vacuum drying to obtain the tert-butyl acrylate grafted carbon microtube with the polymerization degree of 50;

step four, mixing the tertiary butyl acrylate grafted carbon micron tube prepared in the step three with cuprous chloride, tetramethylethylenediamine and dichloromethane according to the weight ratio of 1:0.5:1:30, sealing, filling nitrogen for 10min, adding a styrene monomer, wherein the weight of the styrene monomer is 3 times that of the tertiary butyl acrylate grafted carbon micron tube, continuously filling nitrogen for 10min, heating to 80 ℃, stopping reaction after the viscosity of the system is obviously increased, precipitating, re-dissolving the precipitate, performing suction filtration and washing, and performing vacuum drying to obtain a two-block polymer grafted carbon micron tube;

step five, mixing the two-block polymer grafted carbon micron tube prepared in the step four with ethanol and hydrochloric acid according to the weight ratio of 1:1:1, carrying out sealing reaction for 24 hours, removing the solvent and the catalyst to obtain an inner hydrophilic and outer oleophilic type carbon micron tube, mixing the inner hydrophilic and outer oleophilic type carbon micron tube with barite micro powder with the average particle size of 10 microns according to the weight ratio of 1:100, and carrying out ultrasonic treatment for 10 hours to finally obtain the weighting agent.

< example 2>

The high-density high-temperature-resistant oil-based drilling and completion fluid mainly comprises the following components in parts by weight: 80 parts of white oil, 1 part of organic soil, 1 part of octylphenol polyoxyethylene ether, 3 parts of oleic acid, 5 parts of calcium oxide, 0.5 part of hydroxyethyl cellulose sodium, 1 part of sulfonated phenolic resin and 30 parts of weighting agent; the weighting agent is modified barite micro powder, and the preparation method of the modified barite micro powder comprises the following steps:

mixing a carbon micron tube with the tube wall thickness of 10nm and the tube diameter of 500 microns and sulfuric acid according to the weight ratio of 1:5, carrying out ultrasonic treatment for 1h, heating to 120 ℃, reacting for 24h, filtering and washing until the mixture is neutral, carrying out vacuum drying, continuously adding thionyl chloride, wherein the weight of the thionyl chloride is 10 times that of the carbon micron tube, carrying out ultrasonic treatment for 0.5h, heating to 60 ℃, reacting for 24h under stirring and refluxing, carrying out suction filtration and washing, and preparing an acylated carbon micron tube;

mixing the acylated carbon micron tube prepared in the step one with ethylene glycol according to the weight ratio of 1:50, repeatedly pumping and filling nitrogen for three times after sealing, carrying out ultrasonic treatment for 1h, heating to 100 ℃, reacting for 24h, carrying out suction filtration washing, carrying out vacuum drying, adding α -bromobutyryl bromide again, wherein the weight of the α -bromobutyryl bromide is 3 times that of the acylated carbon micron tube, repeatedly pumping and filling nitrogen for three times after sealing, heating to 60 ℃ after ultrasonic treatment for 1h, reacting for 24h, carrying out suction filtration washing, and carrying out vacuum drying to obtain the carbon micron tube with the initiation group on the surface;

mixing the carbon microtube with the initiation group on the surface prepared in the second step with cuprous chloride, tetramethylethylenediamine and dichloromethane according to the weight ratio of 1:1:5:10, sealing, filling nitrogen for 30min, adding a tert-butyl acrylate monomer, wherein the weight of the tert-butyl acrylate monomer is 10 times that of the carbon microtube with the initiation group on the surface, continuously filling nitrogen for 30min, heating to 100 ℃, stopping reaction after the viscosity of the system is obviously increased, precipitating, re-dissolving the precipitate, performing suction filtration and washing, and performing vacuum drying to obtain the tert-butyl acrylate grafted carbon microtube with the polymerization degree of 10;

step four, mixing the tertiary butyl acrylate grafted carbon micron tube prepared in the step three with cuprous chloride, tetramethylethylenediamine and dichloromethane according to the weight ratio of 1:0.2:0.2:5, filling nitrogen for 30min after sealing, adding a styrene monomer, wherein the weight of the styrene monomer is 2 times that of the tertiary butyl acrylate grafted carbon micron tube, continuing filling nitrogen for 30min, heating to 100 ℃, stopping reaction after the system viscosity is obviously increased, precipitating, re-dissolving the precipitate, performing suction filtration and washing, and performing vacuum drying to obtain a two-block polymer grafted carbon micron tube;

step five, mixing the two-block polymer grafted carbon micron tube prepared in the step four with ethanol and hydrochloric acid according to the weight ratio of 1:10:10, carrying out sealing reaction for 24 hours, removing the solvent and the catalyst to obtain an inner hydrophilic and outer oleophilic type carbon micron tube, mixing the inner hydrophilic and outer oleophilic type carbon micron tube and barite micro powder with the average particle size of 10 microns according to the weight ratio of 1:100 in a small amount of base oil, and carrying out ultrasonic treatment for 5 hours to finally prepare the weighting agent.

< example 3>

The high-density high-temperature-resistant oil-based drilling and completion fluid mainly comprises the following components in parts by weight: 80 parts of biodiesel, 0.5 part of organic soil, 2 parts of oleic acid polyoxyethylene ether, 2 parts of alkylbenzene sulfonate, 5 parts of sodium hydroxide, 0.5 part of xanthan gum, 3 parts of sulfonated phenolic resin and 60 parts of weighting agent; the weighting agent is modified barite micro powder, and the preparation method of the modified barite micro powder comprises the following steps:

step one, mixing a carbon micron tube with the tube wall thickness of 10nm and the tube diameter of 500 microns and concentrated nitric acid according to the weight ratio of 1:3, carrying out ultrasonic treatment for 0.5h, heating to 100 ℃, reacting for 24h, filtering and washing until the mixture is neutral, carrying out vacuum drying, continuously adding thionyl chloride, wherein the weight of the thionyl chloride is 8 times that of the carbon micron tube, carrying out ultrasonic treatment for 0.5h, heating to 100 ℃, carrying out reaction for 24h under stirring and refluxing, carrying out suction filtration and washing, and preparing an acylated carbon micron tube;

mixing the acylated carbon micron tube prepared in the step one with ethylene glycol according to the weight ratio of 1:50, repeatedly pumping and filling nitrogen for three times after sealing, carrying out ultrasonic treatment for 0.5h, heating to 100 ℃, reacting for 24h, carrying out suction filtration washing, carrying out vacuum drying, adding α -bromobutyryl bromide again, wherein the weight of the α -bromobutyryl bromide is 5 times that of the acylated carbon micron tube, repeatedly pumping and filling nitrogen for three times after sealing, carrying out ultrasonic treatment for 0.5h, heating to 100 ℃, reacting for 20h, carrying out suction filtration washing, and carrying out vacuum drying to prepare the carbon micron tube with the initiating group on the surface;

mixing the carbon microtube with the initiation group on the surface prepared in the second step with cuprous chloride, tetramethylethylenediamine and dichloromethane according to the weight ratio of 1:1:5:30, sealing, filling nitrogen for 30min, adding a tert-butyl acrylate monomer, wherein the weight of the tert-butyl acrylate monomer is 20 times that of the carbon microtube with the initiation group on the surface, continuously filling nitrogen for 30min, heating to 120 ℃, stopping reaction after the viscosity of the system is obviously increased, precipitating, re-dissolving the precipitate, performing suction filtration and washing, and performing vacuum drying to obtain the tert-butyl acrylate grafted carbon microtube with the polymerization degree of 100;

step four, mixing the tertiary butyl acrylate grafted carbon micron tube prepared in the step three with cuprous chloride, tetramethylethylenediamine and dichloromethane according to the weight ratio of 1:1:5:10, sealing, filling nitrogen for 30min, adding a styrene monomer, wherein the weight of the styrene monomer is 5 times that of the tertiary butyl acrylate grafted carbon micron tube, continuing filling nitrogen for 40min, heating to 120 ℃, stopping reaction after the system viscosity is obviously increased, precipitating, redissolving the precipitate, performing suction filtration and washing, and performing vacuum drying to obtain a two-block polymer grafted carbon micron tube;

step five, mixing the two-block polymer grafted carbon micron tube prepared in the step four with ethanol and hydrochloric acid according to the weight ratio of 1:10:20, carrying out sealing reaction for 24 hours, removing the solvent and the catalyst to obtain an inner hydrophilic and outer oleophilic type carbon micron tube, mixing the inner hydrophilic and outer oleophilic type carbon micron tube and barite micro powder with the average particle size of 10 microns according to the weight ratio of 1:100 in a small amount of base oil, and carrying out ultrasonic treatment for 10 hours to finally prepare the weighting agent.

< comparative example 1>

The high-density high-temperature-resistant oil-based drilling and completion fluid mainly comprises the following components in parts by weight: 100 parts of diesel oil, 3 parts of organic soil, 1 part of stearic acid polyoxyethylene ether, 2 parts of naphthenic acid amide, 3 parts of sodium hydroxide, 1 part of xanthan gum, 2 parts of hydroxyethyl cellulose and 30 parts of barite micro powder, wherein the average particle size of the barite micro powder is 10 microns.

< comparative example 2>

The carbon nanotubes used in example 1 were changed to carbon nanotubes.

The high-density high-temperature-resistant oil-based drilling and completion fluid mainly comprises the following components in parts by weight: 100 parts of diesel oil, 3 parts of organic soil, 1 part of stearic acid polyoxyethylene ether, 2 parts of naphthenic acid amide, 3 parts of sodium hydroxide, 1 part of xanthan gum, 2 parts of hydroxyethyl cellulose and 50 parts of weighting agent; the weighting agent is modified barite micro powder, and the preparation method of the modified barite micro powder comprises the following steps:

mixing a carbon nano tube and concentrated nitric acid according to a weight ratio of 1:8, carrying out ultrasonic treatment for 0.5h, heating to 120 ℃, reacting for 24h, filtering and washing until the mixture is neutral, carrying out vacuum drying, continuously adding thionyl chloride, heating to 60 ℃ after ultrasonic treatment for 0.5h, carrying out reaction for 24h under stirring and reflux, and carrying out suction filtration and washing to obtain an acylated carbon nano tube;

mixing the acylated carbon nanotube prepared in the step one with ethylene glycol according to a weight ratio of 1:25, repeatedly pumping and filling nitrogen for three times after sealing, carrying out ultrasonic treatment for 0.5h, heating to 100 ℃, reacting for 24h, carrying out suction filtration washing, carrying out vacuum drying, adding α -bromobutyryl bromide with the same amount as the acylated carbon nanotube again, repeatedly pumping and filling nitrogen for three times after sealing, carrying out ultrasonic treatment for 0.5h, heating to 20 ℃, reacting for 10h, carrying out suction filtration washing, and carrying out vacuum drying to obtain the carbon nanotube with the initiating group on the surface;

mixing the carbon nano tube with the initiation group on the surface prepared in the second step with cuprous chloride, tetramethylethylenediamine and dichloromethane according to the weight ratio of 1:0.5:0.7:10, filling nitrogen for 10min after sealing, adding a tert-butyl acrylate monomer, wherein the weight of the tert-butyl acrylate monomer is 5 times of that of the carbon nano tube with the initiation group on the surface, continuously filling nitrogen for 10min, heating to 100 ℃, stopping reaction after the viscosity of the system is obviously increased, precipitating, re-dissolving the precipitate, performing suction filtration and washing, and performing vacuum drying to obtain the tert-butyl acrylate grafted carbon nano tube with the polymerization degree of 50;

step four, mixing the carbon nano tube grafted with the tert-butyl polyacrylate prepared in the step three with cuprous chloride, tetramethylethylenediamine and dichloromethane according to the weight ratio of 1:0.5:1:30, sealing, filling nitrogen for 10min, adding a styrene monomer, wherein the weight of the styrene monomer is 3 times of that of the carbon nano tube grafted with the tert-butyl polyacrylate, continuing filling the nitrogen for 10min, heating to 50 ℃, stopping reaction after the viscosity of the system is obviously increased, precipitating, redissolving the precipitate, performing suction filtration and washing, and performing vacuum drying to obtain the carbon nano tube grafted with the two blocks of the high polymers;

step five, mixing the two-block polymer grafted carbon nano tube prepared in the step four with ethanol and hydrochloric acid according to the weight ratio of 1:1:1, carrying out sealing reaction for 24 hours, removing the solvent and the catalyst to obtain an inner hydrophilic and outer oleophylic carbon nano tube, mixing the inner hydrophilic and outer oleophylic carbon nano tube with barite micro powder with the average particle size of 10 mu m according to the weight ratio of 1:100, and carrying out ultrasonic treatment for 10 hours to finally obtain the weighting agent.

< determination of wall thickness and diameter of tube of inner hydrophilic and outer lipophilic carbon micro-tube >

The tube wall thickness and the tube diameter of the inner hydrophilic and outer oleophilic carbon nanotubes prepared in examples 1 to 3 and the inner hydrophilic and outer oleophilic carbon nanotubes prepared in comparative example 2 were measured, and the measurement results are shown in table 1:

TABLE 1

The measurement result shows that the average tube diameter of the tube wall thickness of the inner hydrophilic outer lipophilic carbon micron tube prepared by each example is 50nm, the average tube diameter can reach 350 mu m, and the tube wall thickness can be completely coated on the surface of the barite micro powder with the average particle size of 10 mu m so as to realize the lipophilic modification to the barite micro powder; in the comparative example 2, the carbon nano tube is used as a raw material, and the thickness and the diameter of the tube wall of the finally prepared inner hydrophilic and outer oleophylic carbon nano tube are both nano-scale, so that the micron-scale barite micro powder cannot be wrapped, and oleophylic modification of the micron-scale barite micro powder is difficult to perform.

< Dispersion Performance test >

The dispersing properties of the weighting agents of the present invention were evaluated by the sedimentation velocity method, and the sedimentation velocity of the weighting agents used in examples 1 to 3 and comparative examples 1 to 2 in the base oil was measured and recorded, and the test results are shown in table 2:

TABLE 2

Test results show that the weighting agent prepared by the invention, namely the modified barite micro powder prepared in examples 1-3, has good dispersibility in an oily medium due to the fact that the surface of the weighting agent is wrapped with the internal hydrophilic and external lipophilic carbon micro tubes. In the comparative example 1, barite micro powder is directly used as a weighting agent, the settling speed of the barite micro powder is 60 times that of the weighting agent, the settling speed is high, and the dispersibility in an oily medium is poor; comparative example 2 because the prepared inner hydrophilic and outer oleophylic carbon nano tube has the nano-scale tube wall thickness and the nano-scale tube diameter, the micron-scale barite micro powder can not be wrapped, and oleophylic modification is difficult to carry out, so that the sedimentation speed is not much different from that of comparative example 1, and the dispersibility in an oily medium is poor.

< oil-based drilling and completion fluid Density determination test >

The densities of the air-containing drilling fluids prepared in examples 1-3 and comparative examples 1-2 were accurately measured using a pressurized drilling fluid densitometer, and the results are shown in table 3:

TABLE 3

The measurement result shows that the density of the well completion liquid prepared according to the test procedures and the proportion of the examples 1 to 3 of the invention can reach 2.6g/cm ³(ii) a The comparative example 1 directly adopts barite micro powder as a weighting agent, the dispersibility of the barite micro powder in an oily medium is poor, the drilling difficulty is increased for preventing the drilling progress from being influenced by the massive settlement of the barite, and the addition amount of the barite is relatively small, so that the drilling completion density of a final preparation position is small; comparative example 2 because the carbon nano tube is added in the weighting agent, the density of the drilling completion fluid is increased compared with that of comparative example 2, but the carbon nano tube has smaller size, can not wrap micron-sized barite micropowder, is difficult to carry out oleophylic modification, can not improve the dispersibility of the weighting agent in an oil medium, and still has the problem of easy agglomeration and sedimentation.

< oil-based drilling and completion fluid temperature stability test >

The aging of the drilling fluid prepared in example 1 after 24 hours, 36 hours, 48 hours and 168 hours was measured at 240 ℃, and the temperature stability was tested, and the comparative data are shown in table 4:

as can be seen from Table 4, the apparent viscosity and the plastic viscosity of the drilling completion fluid prepared in example 1 are decreased after aging for 24h, 36h, 48h and 168h at 240 ℃, but the decrease is not large, and good rheological properties are still maintained, the HPHT fluid loss increase of the drilling completion fluid is large after the aging time is increased from 24h to 48h, the HPHT fluid loss increase is small after 48h, and the drilling completion fluid is in a stable state.

TABLE 3

The number of apparatuses and the scale of the process described herein are intended to simplify the description of the present invention. Applications, modifications and variations of the present invention will be apparent to those skilled in the art.

While embodiments of the invention have been described above, it is not limited to the applications set forth in the description and the embodiments, which are fully applicable to various fields of endeavor for which the invention may be embodied with additional modifications as would be readily apparent to those skilled in the art, and the invention is therefore not limited to the details given herein and to the examples shown and described without departing from the generic concept as defined by the claims and their equivalents.