Modified asphalt for water-based drilling fluid and preparation method thereof

Abstract

The invention discloses modified asphalt for water-based drilling fluid and a preparation method of the modified asphalt. The preparation method of the modified asphalt for the water-based drilling fluid comprises the following steps: (1) preparing an activating agent; (2) carrying out activating treatment on silicon dioxide by adopting the activating agent obtained in the step (1) to prepare a modifying agent; and (3) adding matrix asphalt into an organic solvent for dissolving, then adding the modifier prepared in the step (2), reacting while stirring, and then adding halogenated hydrocarbon for continuous reaction to obtain the modified asphalt for the water-based drilling fluid. By adopting the modifier containing a specific functional group structure, the obtained modified asphalt for the water-based drilling fluid is high in softening point, has cationic characteristics, high temperature resistance and high well wall adhesion capacity, and can continuously play a role in the high-temperature water-based drilling fluid.

Description

Technical Field

[0001] The present invention belongs to the field of modified asphalt, and particularly relates to a modified asphalt for water-based drilling fluid and a preparation method thereof. Background Art

[0002] Asphalt products have a wide range of uses in the process of oil and gas drilling. They can be used as an important component of drilling fluid and are one of the indispensable important agents in modern drilling engineering, with comprehensive effects such as good anti-collapse, lubrication, reduced filtration loss, and high-temperature stability. With the development of oil exploration and development, the drilling depth is continuously increasing, the drilled formations are becoming more and more complex, and the number of special process wells such as directional wells and horizontal wells is gradually increasing. This has put forward higher requirements for asphalt products and their systems used in drilling fluid. Ordinary softening point asphalt cannot meet the high-temperature operation requirements in deep wells because of excessive softening or even flowing. Developing high softening point asphalt with good high-temperature performance, good plugging property, and filtration loss reduction property to meet the needs of oilfield drilling engineering is of great significance.

[0003] At present, the most commonly used method to improve the performance of asphalt products used in drilling fluid is to sulfonate asphalt. Such as US3485745, CN1239133A, CN101906311A, etc. After asphalt is sulfonated, sulfonates are mainly generated, and the softening point of the product can hardly be measured and can only be used under lower temperature conditions. It cannot play a good role in plugging and reducing filtration loss. At the same time, this process is relatively complex and is easy to cause environmental pollution.

[0004] High softening point petroleum asphalt is mainly oil-soluble, so it has good dispersibility in oil-based drilling fluid and there is no problem in application. However, in water-based drilling fluid, due to its very low water solubility, there are problems of difficult dispersion and instability. This is also a major factor restricting the wide application of high softening point asphalt in water-based drilling fluid.

[0005] When high softening point asphalt is used in drilling fluid, it is required to be dispersed into the mud system in the form of tiny particles, which can not only ensure uniform dispersion of asphalt but also avoid problems such as coalescence into larger lumps and blocking the vibrating screen, resulting in unusability. Usually, the particle size of asphalt particles is required to be below 120μm, or even below 100μm for normal use. General high softening point asphalt is mostly petroleum asphalt, coal tar pitch, natural asphalt, etc.

[0006] High softening point asphalt used in deep wells and ultra-deep wells not only requires a high softening point but also needs to have good compatibility and stability with the drilling fluid system, especially the water-based drilling fluid system. Since the wellbore rock formation usually has a negative charge, asphalt with cationic characteristics can not only be easily and stably dispersed in the drilling fluid system but also combine more firmly with the wellbore wall, and can better play the role of stabilizing the wellbore wall and plugging.

[0007] Overall, the asphalt products currently used in water-based drilling fluids have a low softening point and poor dispersion performance in the drilling fluid, and cannot well meet the usage requirements of the drilling fluid for plugging, preventing collapse, stabilizing the wellbore, reducing the filtration loss, etc. Summary of the Invention

[0008] Aiming at the deficiencies of the prior art, the present invention provides a modified asphalt for water-based drilling fluids and a preparation method thereof. By using a modifier containing a specific functional group structure, the modified asphalt for water-based drilling fluids obtained has a high softening point, cationic characteristics, strong high-temperature resistance and adhesion ability to the wellbore, and can continuously play a role in high-temperature water-based drilling fluids.

[0009] The first aspect of the present invention provides a preparation method of a modified asphalt for water-based drilling fluids, including:

[0010] (1) Prepare an activator;

[0011] (2) Use the activator obtained in step (1) to activate silica to prepare a modifier;

[0012] (3) Dissolve the matrix asphalt in an organic solvent, then add the modifier prepared in step (2), react under stirring, and then add a halogenated hydrocarbon to continue the reaction to obtain a modified asphalt for water-based drilling fluids.

[0013] Further, in step (1), the preparation method of the activator includes: First, synthesize a cyclic monomer from a nitrile monomer under the action of a catalyst; then carry out ring-opening polymerization on the above cyclic monomer to form a polymer of the cyclic monomer; finally, hydrolyze the polymer of the cyclic monomer under acidic conditions to obtain an activator. The specific method includes:

[0014] (a) Add the nitrile monomer and the catalyst to a reactor, heat to 90 - 120 °C, then add an amino alcohol monomer, and react for 30 - 60 h to obtain a cyclic monomer;

[0015] (b) Mix the cyclic monomer obtained in step (a), an initiator and a nitrile monomer, react at 100 - 160 °C for 30 - 90 min, then add a methanol solution of KOH at -10 °C - 10 °C, stir for 8 - 24 h, remove the solvent, dissolve the residual polymer in chloroform, precipitate and purify, and dry to obtain a polymer of the cyclic monomer;

[0016] (c) Dissolve the polymer of the cyclic monomer obtained in step (b) in hot water, heat under reflux, add a hydrochloric acid solution, react for 24 - 72 h, remove the solvent, redissolve the residual polymer in hot water, add a NaOH solution until the pH value of the solution is 9 - 10, precipitate by centrifugation, remove the supernatant, repeat 2 - 3 times, and dry to obtain an activator.

[0017] Further, in step (a), the nitrile monomer is preferably ultra-dry acetonitrile and / or propionitrile. The catalyst is zinc acetate dihydrate. The volume-mass ratio of the nitrile monomer to the catalyst addition amount is 10 - 20∶1 mL / g. The amino alcohol monomer is preferably one or more of 2-aminoethanol and 3-amino-1-propanol. The volume ratio of the nitrile monomer to the amino alcohol monomer addition amount is 1∶1 - 3.

[0018] Further, in step (b), the initiator is a sulfonate cation initiator, preferably one or more of methyl p-toluenesulfonate (MeOTs), ethyl trifluoromethanesulfonate, 3-butynyl p-toluenesulfonate, etc. In step (b), the nitrile monomer is preferably ultra-dry acetonitrile and / or propionitrile. Among them, the nitrile monomer in step (b) can be the same as or different from that in step (a). The volume ratio of the initiator to the cyclic monomer addition amount is 0.01 - 0.1∶1; the volume ratio of the cyclic monomer to the nitrile monomer is 1∶1 - 3.

[0019] Further, in step (b), after the cyclic monomer, the initiator and the nitrile monomer are mixed, the reaction is carried out in a microwave reactor.

[0020] Further, in step (b), the concentration of KOH in the methanol solution of KOH is 0.8 - 1.2 mol / L. The addition amount of the methanol solution of KOH is 1 / 10 - 1 / 40 of the volume of the cyclic monomer.

[0021] Further, in step (b), the stirring is carried out at 20 - 30 °C, preferably at room temperature.

[0022] Further, in step (b), the solvent removal can be carried out by rotary evaporation. The precipitation purification can be carried out in n-hexane. The drying conditions are: drying in vacuum at 30 - 50 °C for 24 - 72 h.

[0023] Further, in step (c), the temperature of the hot water is 40 - 80 °C. The temperature of the heating reflux is 80 - 120 °C, and the heating reflux time is 10 - 30 min. The mass concentration of the hydrochloric acid solution is 30% - 38%. The mass ratio of the addition amount of the hydrochloric acid solution to the polymer addition amount of the cyclic monomer is 1 - 20∶1. The solvent removal can be carried out by rotary evaporation. The drying conditions are: drying in vacuum at 50 - 70 °C for 24 - 72 h.

[0024] Further, the method for preparing the modifier in step (2) specifically includes:

[0025] (i) Mix silica, epoxy - type silane coupling agent and ethanol, heat under reflux, centrifuge the resulting suspension, ultrasonically disperse the precipitate with ethanol, remove the supernatant, wash, and dry to obtain an intermediate product;

[0026] (ii) Dissolve an activator in ethanol, add the intermediate product obtained in step (i), heat under reflux, centrifuge the resulting suspension, ultrasonically disperse the precipitate with water, remove the supernatant, wash, and dry to obtain a modifier.

[0027] Further, in step (i), the particle size of the silica is 10 nm - 100 nm.

[0028] Further, in step (i), the epoxy - type silane coupling agent is 3 - glycidoxypropylmethyldiethoxysilane (GPTMS). The mass - to - volume ratio of the silica to the epoxy - type silane coupling agent is 1∶1 - 3 g / mL; mix the silica, epoxy - type silane coupling agent and ethanol, where the volume ratio of the epoxy - type silane coupling agent to ethanol is 1∶1 - 5.

[0029] In steps (i) and (ii), the temperature of heat under reflux is 80 - 120 °C, and the heat - reflux time is 12 - 36 h.

[0030] Further, in step (i), the rotation speed of the centrifugation is 5000 - 15000 rpm, and the centrifugation time is 10 - 30 min. The frequency of the ultrasonic dispersion is 20 kHz - 60 kHz, and the ultrasonic dispersion time is 5 - 20 min. The drying temperature is 50 - 80 °C, and the drying time is 5 - 20 h.

[0031] Further, the ethanol in steps (i) and (ii) is anhydrous ethanol.

[0032] Further, in step (ii), based on the mass of ethanol, the addition amount of the activator is 1 - 20%. Based on the mass of ethanol, the addition amount of the intermediate product is 1 - 30%. Among them, the mass ratio of the addition amount of the activator to the intermediate product is 1∶1 - 2.

[0033] Further, in step (ii), the rotation speed of the centrifugation is 5000 - 15000 rpm, and the centrifugation time is 10 - 30 min. The frequency of the ultrasonic dispersion is 20 kHz - 60 kHz, and the ultrasonic dispersion time is 5 - 20 min. The stirring - reflux time is 12 - 36 h. The drying temperature is 50 - 80 °C, and the drying time is 5 - 20 h.

[0034] Further, in step (3), the softening point of the matrix asphalt is 100 - 200 °C.

[0035] Further, in step (3), the organic solvent is selected from one or more of chloroform, dichloromethane, toluene, tetrahydrofuran, and carbon tetrachloride. The mass ratio of the matrix asphalt to the organic solvent is 1:1 - 1:20.

[0036] Further, in step (3), the stirring speed is 90 - 2000 rpm, and the reaction conditions under stirring are: reacting at 10 - 120 °C for 1 - 24 h, preferably reacting at 30 - 110 °C for 2 - 12 h. After the reaction, the excess organic solvent can be removed by rotary evaporation.

[0037] Further, in step (3), the halogenated hydrocarbon is benzyl chloride and / or hexadecyl bromide.

[0038] Further, the mass ratio of the modifier to the halogenated hydrocarbon is 1 - 3:1.

[0039] Further, in step (3), after adding the halogenated hydrocarbon, the continued reaction conditions are: reacting at 80 - 120 °C for 1 - 4 h, preferably reacting at 80 - 100 °C for 2 - 3 h.

[0040] Further, in step (3), based on the weight of the modified asphalt for water-based drilling fluid obtained, the content of the matrix asphalt is 90 wt% - 99.9 wt%, and the content of the modifier is 0.1 wt% - 10 wt%.

[0041] The second aspect of the present invention provides a modified asphalt for water-based drilling fluid prepared by the above method.

[0042] The third aspect of the present invention provides an application of the above modified asphalt for water-based drilling fluid in drilling fluid.

[0043] Further, when the modified asphalt for water-based drilling fluid is applied to drilling fluid, it can be pulverized by a conventional method in the art. For example, the modified asphalt for water-based drilling fluid is frozen at -10 °C to -50 °C for 1 - 10 hours, and then pulverized by a universal pulverizer for 1 - 60 s to obtain modified asphalt particles for water-based drilling fluid with an average particle size of 80 - 120 mesh.

[0044] Further, the addition amount of the modified asphalt particles for water-based drilling fluid in the water-based drilling fluid is 1% - 10% by weight percentage.

[0045] Compared with the prior art, the present invention has the following advantages:

[0046] (1) The present invention uses nano-SiO treated with an activator 2As an asphalt modifier, the amine groups it contains undergo a grafting reaction with asphalt, which can show positive charge. The rock formations on the well wall are usually negatively charged, so the cationic asphalt will bond more firmly to the well wall and can better play the role of sealing and reducing filtration loss.

[0047] (2) The surface of the water-based drilling fluid modified asphalt of the present invention is grafted with cationic groups, which has strong surface activity and is easier to be evenly and stably dispersed in the drilling fluid, especially in the water-based drilling fluid, thereby solving the problem that the asphalt-based treatment agent is difficult to be stably dispersed in the water-based drilling fluid.

[0048] (3) The present invention uses a specific modifier to modify high softening point asphalt with the aid of a solvent. The resulting modified asphalt has a high softening point and strong activity, and can continue to function at high temperatures when used in drilling fluids. DETAILED DESCRIPTION

[0049] The following non-limiting embodiments may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0050] Example 1

[0051] 34.6mL of ultra-dry acetonitrile and 2.86g of zinc acetate dihydrate were added to a 250mL three-necked flask, heated to 100°C, and after the acetonitrile refluxed, 60mL of 2-aminoethanol was slowly dripped thereinto using a constant pressure dropping funnel, reacted for 45h, and a cyclic monomer was obtained after impurity removal. 26.5mL of the above cyclic monomer, 0.42mL of methyl toluenesulfonate (MeOTs) and 45.5mL of ultra-dry acetonitrile were mixed, placed in a 150°C microwave reactor for reaction for 60min, and then 1.8mL of a methanol solution of KOH with a concentration of 1mol / L was added at -5°C, stirred at room temperature for 15h, the polymerization was terminated, the solvent was removed by rotary evaporation, the residual polymer was dissolved in chloroform, and then precipitated and purified in n-hexane 3 times, and dried in a vacuum at 40°C for 40h to obtain a polymer of the cyclic monomer. 28.5 g of the above-mentioned cyclic monomer polymer was dissolved in 60°C hot water, heated to reflux at 115°C for 15 min, added to 300 g of 36% hydrochloric acid, reacted for 38 h, and the solvent was removed by rotary evaporation. The residual solid was redissolved in 55°C hot water, and NaOH solution was added to neutralize the solution to pH = 9. The precipitate was centrifuged and the supernatant was discarded. The process was repeated 3 times and vacuum dried at 60°C for 50 h to obtain an activator.

[0052] Take 20g SiO 2(Particle size 50 nm), 45 mL of GPTMS and 180 mL of ethanol were added to a flask, and the mixture was stirred and refluxed at 105 °C for 28 h. Then the suspension was centrifuged at 11000 rpm for 20 min to remove the supernatant; it was ultrasonically dispersed with 100 mL of ethanol for 15 min at an ultrasonic dispersion frequency of 20 kHz, the supernatant was removed, and the washing was repeated 3 times. The product was placed in an oven at 60 °C for 16 h to obtain an intermediate product. 24.5 g of the activator prepared above was added to 200 g of ethanol and dissolved, and then 32.5 g of the intermediate product prepared above was added, and the mixture was stirred and refluxed at 110 °C for 30 h. Then the suspension was centrifuged at 12000 rpm for 25 min to remove the supernatant; it was ultrasonically dispersed with deionized water for 20 min at an ultrasonic dispersion frequency of 20 kHz, the supernatant was removed, and the washing was repeated 3 times. The product was placed in an oven at 70 °C for 10 h to obtain modifier I.

[0053] Example 2

[0054] 42.4 mL of ultradry propionitrile and 3.85 g of zinc acetate dihydrate were added to a 250 mL three-necked flask, heated to 115 °C, and after the propionitrile refluxed, 58 mL of 3-amino-1-propanol was slowly added dropwise thereto using a constant pressure dropping funnel, and the reaction was carried out for 55.5 h. After removing impurities, a cyclic monomer was obtained. 34.2 mL of the above cyclic monomer, 0.5 mL of 3-butynyl p-toluenesulfonate and 48.6 mL of ultradry acetonitrile were mixed, placed in a microwave reactor at 140 °C and reacted for 75 min, and then 2.0 mL of a methanol solution of KOH with a concentration of 0.8 mol / L was added at 0 °C, and the mixture was stirred at room temperature for 18 h to terminate the polymerization. The solvent was removed by rotary evaporation, the residual polymer was dissolved in chloroform and then precipitated and purified 3 times in n-hexane, and dried in vacuo at 45 °C for 6 h to obtain a polymer of the cyclic monomer. 35.4 g of the above cyclic monomer polymer was dissolved in hot water at 70 °C, heated and refluxed at 110 °C for 20 min, added to 350 g of hydrochloric acid with a mass concentration of 36%, and reacted for 50 h. The solvent was removed by rotary evaporation, the residual solid was redissolved in hot water at 70 °C, and NaOH solution was added to neutralize to a solution pH of 9.5. The precipitated precipitate was centrifuged, and the supernatant was discarded. This was repeated 3 times, and dried in vacuo at 65 °C for 45 h to obtain an activator.

[0055] Take 25 g of SiO 2(Particle size 100 nm), 60 mL of GPTMS and 195 mL of ethanol were added to a flask, and the mixture was stirred and refluxed at 115 °C for 36 h. Then the suspension was centrifuged at 14000 rpm for 25 min to remove the supernatant; it was ultrasonically dispersed in 120 mL of ethanol for 18 min at a frequency of 40 kHz, the supernatant was removed, and the washing was repeated 3 times. The product was placed in an oven at 65 °C for 20 h to obtain an intermediate product. After dissolving 27.6 g of the activator prepared above in 280 g of ethanol, 40.5 g of the intermediate product prepared above was added, and the mixture was stirred and refluxed at 115 °C for 20 h. Then the suspension was centrifuged at 14000 rpm for 30 min to remove the supernatant; it was ultrasonically dispersed in deionized water for 20 min at a frequency of 40 kHz, the supernatant was removed, and the washing was repeated 3 times. The product was placed in an oven at 65 °C for 18 h to obtain modifier II.

[0056] Example 3

[0057] 200 g of eluted asphalt with a softening point of 118.5 °C was placed in 380 g of chloroform. After complete dissolution, the modifier I prepared above was added, and mechanical stirring was carried out at a rotation speed of 1200 rpm. The reaction was stirred at 85 °C for 4 h. After adding 6.56 g of benzyl chloride, the reaction was continued at 85 °C for 2 h. After the reaction was completed, the excess organic solvent was removed by rotary evaporation, frozen at -25 °C for 4 hours, and then crushed with a universal crusher for 50 s. The sieved water-based drilling fluid modified asphalt particles had an average particle size of 80 mesh, and the modified asphalt particles contained 5.5 wt% of modifier I.

[0058] Example 4

[0059] 200 g of eluted asphalt with a softening point of 126.4 °C was placed in 450 g of chloroform. After complete dissolution, the modifier II prepared above was added, and mechanical stirring was carried out at a rotation speed of 1500 rpm. The reaction was stirred at 90 °C for 10 h. After adding 6.46 g of cetyl bromide, the reaction was continued at 90 °C for 2.5 h. After the reaction was completed, the excess organic solvent was removed by rotary evaporation, frozen at -35 °C for 6 hours, and then crushed with a universal crusher for 40 s. The sieved water-based drilling fluid modified asphalt particles had an average particle size of 100 mesh, and the modified asphalt particles contained 4.8 wt% of modifier II.

[0060] Example 5

[0061] 200 g of oxidized asphalt with a softening point of 138.5 °C was placed in 560 g of chloroform and tetrahydrofuran. After complete dissolution, the above-prepared modifier I was added, and mechanical stirring was carried out at a rotation speed of 1100 rpm. The reaction was stirred at 75 °C for 6 h. After adding 7.32 g of benzyl chloride, the reaction was continued at 90 °C for 2 h. After the reaction, the excess organic solvent was removed by rotary evaporation, frozen at -25 °C for 8 h, then pulverized with a universal pulverizer for 35 s, and sieved to obtain modified asphalt particles for water-based drilling fluid with an average particle size of 80 mesh. The modified asphalt particles contained 6.8 wt% of modifier I.

[0062] Example 6

[0063] 200 g of oxidized asphalt with a softening point of 151.4 °C was placed in 500 g of chloroform. After complete dissolution, the above-prepared modifier II was added, and mechanical stirring was carried out at a rotation speed of 1800 rpm. The reaction was stirred at 100 °C for 7.5 h. After adding 5.68 g of benzyl chloride, the reaction was continued at 90 °C for 3 h. After the reaction, the excess organic solvent was removed by rotary evaporation, frozen at -30 °C for 8.5 h, then pulverized with a universal pulverizer for 60 s, and sieved to obtain modified asphalt particles for water-based drilling fluid with an average particle size of 100 mesh. The modified asphalt particles contained 6.0 wt% of modifier II.

[0064] Comparative Example 1

[0065] 200 g of eluted asphalt with a softening point of 126.4 °C was frozen at -35 °C for 6 h, then pulverized with a universal pulverizer for 40 s, and sieved to obtain asphalt particles for water-based drilling fluid with an average particle size of 100 mesh.

[0066] Comparative Example 2

[0067] Take 25 g of SiO 2 (particle size 100 nm), 60 mL of GPTMS and 195 mL of ethanol, add them to a flask, and stir and reflux the mixture at 115 °C for 36 h. Then centrifuge the suspension at 14000 rpm for 25 min to remove the supernatant; disperse it ultrasonically with 120 mL of ethanol for 18 min, the ultrasonic dispersion frequency is 40 kHz, remove the supernatant, repeat the washing 3 times, and place the product in an oven at 65 °C for 20 h to obtain modifier III.

[0068] 200 g of deasphalted bitumen with a softening point of 126.4 °C was placed in 450 g of chloroform. After complete dissolution, the above-prepared modifier III was added, and mechanical stirring was carried out at a rotation speed of 1500 rpm. The reaction was carried out at 90 °C for 10 h. After adding 6.46 g of cetyl bromide, the reaction was continued at 90 °C for 2.5 h. After the reaction, the excess organic solvent was removed by rotary evaporation, frozen at -35 °C for 6 h, then pulverized with a universal pulverizer for 40 s, and sieved to obtain modified asphalt particles for water-based drilling fluid with an average particle size of 100 mesh. The modified asphalt particles contained 4.8 wt% of modifier III.

[0069] Comparative Example 3

[0070] 42.4 mL of ultra-dry propionitrile and 3.85 g of zinc acetate dihydrate were added to a 250 mL three-necked flask and heated to 115 °C. After the propionitrile refluxed, 58 mL of 3-amino-1-propanol was slowly added dropwise thereto using a constant pressure dropping funnel, and the reaction was carried out for 55.5 h. After impurity removal, a cyclic monomer was obtained. 34.2 mL of the above cyclic monomer, 0.5 mL of 3-butynyl p-toluenesulfonate, and 48.6 mL of ultra-dry acetonitrile were mixed and placed in a microwave reactor at 140 °C for reaction for 75 min. Then, 2.0 mL of a methanol solution of KOH with a concentration of 0.8 mol / L was added at 0 °C, and the mixture was stirred at room temperature for 18 h to terminate the polymerization. The solvent was removed by rotary evaporation, and the residual polymer was dissolved in chloroform and then precipitated and purified three times in n-hexane, and dried in vacuo at 45 °C for 6 h to obtain a polymer of the cyclic monomer. 35.4 g of the above cyclic monomer polymer was dissolved in hot water at 70 °C, heated to reflux at 110 °C for 20 min, and added to 350 g of hydrochloric acid with a mass concentration of 36%, and the reaction was carried out for 50 h. The solvent was removed by rotary evaporation, the residual solid was redissolved in hot water at 70 °C, and the solution was neutralized with NaOH solution to a solution pH of 9.5. The precipitated precipitate was centrifuged, and the supernatant was discarded. This was repeated three times, and the product was dried in vacuo at 65 °C for 45 h to obtain an activator.

[0071] 200 g of deasphalted bitumen with a softening point of 126.4 °C was placed in 450 g of chloroform. After complete dissolution, the above-prepared activator was added, and mechanical stirring was carried out at a rotation speed of 1500 rpm. The reaction was carried out at 90 °C for 10 h. After adding 6.46 g of cetyl bromide, the reaction was continued at 90 °C for 2.5 h. After the reaction, the excess organic solvent was removed by rotary evaporation, frozen at -35 °C for 6 h, then pulverized with a universal pulverizer for 40 s, and sieved to obtain modified asphalt particles for water-based drilling fluid with an average particle size of 100 mesh. The modified asphalt particles contained 4.8 wt% of the activator.

[0072] The properties of the modified asphalt for water-based drilling fluids obtained in the above Examples 3-6 and Comparative Examples 1-3 are shown in Table 1. The particles were placed in the prepared base slurry (the addition amount of the modified asphalt for drilling fluid was 4.6 wt% based on the weight of the drilling fluid), and sheared at high speed for 20 min to obtain a water-based drilling fluid system. The drilling fluid performance was tested, as shown in Table 2.

[0073] Among them, the process for preparing the base slurry was as follows: 2.75 g of anhydrous sodium carbonate was added to every 1000 mL of water, and then 60 g of sodium bentonite was added. After high-speed stirring for 20 min and curing at room temperature for 24 h, the base slurry was obtained.

[0074] Table 1 Physical and chemical parameters of the modified asphalt particles for water-based drilling fluids in each example and comparative example

[0075]

[0076]

[0077] Table 2 Performance of the water-based drilling fluid

[0078]

[0079] *Note: Aging temperature is 150 °C and aging time is 16 h.

[0080] It should be emphasized that the above-mentioned content is only a specific embodiment of the present invention, and it cannot be considered that the implementation of the present invention is limited to the above description in the specific process. For scientific research and technical personnel in the technical field to which the present invention belongs, any simple deduction and improvement made without departing from the idea and principle of the present invention shall be regarded as within the protection scope of the present invention.

Claims

1. A preparation method of modified asphalt for water-based drilling fluid, comprising: (1) Preparing an activator; (2) Using the activator obtained in step (1) to activate silica to prepare a modifier; (3) Adding matrix asphalt to an organic solvent for dissolution, then adding the modifier prepared in step (2), reacting under stirring, and then adding a halogenated hydrocarbon to continue the reaction to obtain modified asphalt for water-based drilling fluid.

2. The preparation method according to claim 1, characterized in that: In step (1), the preparation method of the activator includes: First, a nitrile monomer is synthesized into a cyclic monomer under the action of a catalyst; then the cyclic monomer is subjected to ring-opening polymerization to form a polymer of the cyclic monomer; the polymer of the cyclic monomer is hydrolyzed under acidic conditions to obtain an activator.

3. The preparation method according to claim 1 or 2, characterized in that: In step (1), the preparation method of the activator includes: (a) Adding a nitrile monomer and a catalyst to a reactor, heating to 90 - 120 °C, then adding an amino alcohol monomer, and reacting for 30 - 60 h to obtain a cyclic monomer; (b) Mixing the cyclic monomer obtained in step (a), an initiator, and a nitrile monomer, reacting at 100 - 160 °C for 30 - 90 min, then adding a methanol solution of KOH at -10 °C - 10 °C, stirring for 8 - 24 h, removing the solvent, dissolving the residual polymer in chloroform, precipitating and purifying, and drying to obtain a polymer of the cyclic monomer; (c) Dissolving the polymer of the cyclic monomer obtained in step (b) in hot water, heating under reflux, adding a hydrochloric acid solution, reacting for 24 - 72 h, removing the solvent, redissolving the residual polymer in hot water, adding an NaOH solution until the pH value of the solution is 9 - 10, precipitating by centrifugation, removing the supernatant, repeating 2 - 3 times, and drying to obtain an activator.

4. The preparation method according to claim 3, characterized in that: In step (a), the nitrile monomer is ultra-dry acetonitrile and / or propionitrile; the catalyst is zinc acetate dihydrate; wherein, the volume-mass ratio of the nitrile monomer to the catalyst added is 10 - 20:1 mL / g; the amino alcohol monomer is one or more of 2-aminoethanol and 3-amino-1-propanol; the volume ratio of the nitrile monomer to the amino alcohol monomer added is 1:1 - 3.

5. The preparation method according to claim 3, characterized in that: In step (b), the initiator is a sulfonate cationic initiator, preferably one or more of methyl p-toluenesulfonate, ethyl trifluoromethanesulfonate, and 3-butynyl p-toluenesulfonate; in step (b), the nitrile monomer is ultra-dry acetonitrile and / or propionitrile; the volume ratio of the initiator to the cyclic monomer added is 0.01 - 0.1:1; the volume ratio of the cyclic monomer to the nitrile monomer is 1:1 - 3.

6. The preparation method according to claim 3, characterized in that: In step (b), the concentration of KOH in the methanol solution of KOH is 0.8 - 1.2 mol / L; the addition amount of the methanol solution of KOH is 1 / 10 - 1 / 40 of the volume of the cyclic monomer.

7. The preparation method according to claim 3, It is characterized in that: In step (c), the temperature of the hot water is 40 - 80°C; the temperature of the heating reflux is 80 - 120°C, and the heating reflux time is 10 - 30 min; the mass concentration of the hydrochloric acid solution is 30% - 38%; the mass ratio of the addition amount of the hydrochloric acid solution to the addition amount of the polymer of the cyclic monomer is 1 - 20:1; the drying conditions are: vacuum drying at 50 - 70°C for 24 - 72 h.

8. The preparation method according to claim 1, It is characterized in that: The method for preparing the modifier in step (2) specifically includes: (i) Mix silica, epoxy - type silane coupling agent and ethanol, heat under reflux, centrifuge the obtained suspension, ultrasonically disperse the precipitate with ethanol, remove the supernatant, wash, and dry to obtain an intermediate product; (ii) Dissolve the activator in ethanol, add the intermediate product obtained in step (i), heat under reflux, centrifuge the obtained suspension, ultrasonically disperse the precipitate with water, remove the supernatant, wash, and dry to obtain the modifier.

9. The preparation method according to claim 8, It is characterized in that: In step (i), the epoxy - type silane coupling agent is 3 - glycidoxypropylmethyldiethoxysilane; the mass - to - volume ratio of silica to the epoxy - type silane coupling agent is 1:1 - 3 g / mL; mix silica, epoxy - type silane coupling agent and ethanol, and the volume ratio of the epoxy - type silane coupling agent to ethanol is 1:1 - 5.

10. The preparation method according to claim 8, It is characterized in that: In steps (i) and (ii), the temperature of the heating reflux is 80 - 120°C, and the heating reflux time is 12 - 36 h.

11. The preparation method according to claim 8, It is characterized in that: In step (i), the rotation speed of the centrifugation is 5000 - 15000 rpm, and the centrifugation time is 10 - 30 min; the frequency of the ultrasonic dispersion is 20 kHz - 60 kHz, and the ultrasonic dispersion time is 5 - 20 min; the drying temperature is 50 - 80°C, and the drying time is 5 - 20 h.

12. The preparation method according to claim 8, It is characterized in that: In step (ii), based on the mass of ethanol, the addition amount of the activator is 1 - 20%; based on the mass of ethanol, the addition amount of the intermediate product is 1 - 30%; among them, the mass ratio of the addition amount of the activator to the intermediate product is 1:1 - 2.

13. The preparation method according to claim 8, It is characterized in that: In step (ii), the rotation speed of the centrifugation is 5000 - 15000 rpm, and the centrifugation time is 10 - 30 min; the frequency of the ultrasonic dispersion is 20 kHz - 60 kHz, and the ultrasonic dispersion time is 5 - 20 min; the stirring reflux time is 12 - 36 h; the drying temperature is 50 - 80°C, and the drying time is 5 - 20 h.

14. The preparation method according to claim 1, It is characterized in that: In step (3), the organic solvent is selected from one or more of chloroform, dichloromethane, toluene, tetrahydrofuran, and carbon tetrachloride; the mass ratio of the matrix asphalt to the organic solvent is 1:1 - 1:

20.

15. According to the preparation method described in claim 1, it is characterized in that: In step (3), the rotation speed of the stirring is 90 - 2000 rpm, and the conditions for the reaction under stirring are: reacting at 10 - 120 °C for 1 - 24 h, preferably reacting at 30 - 110 °C for 2 - 12 h.

16. According to the preparation method described in claim 1, it is characterized in that: In step (3), the halogenated hydrocarbon is benzyl chloride and / or cetyl bromide; and / or, the mass ratio of the modifier to the halogenated hydrocarbon is 1 - 3:1; and / or, in step (3), after adding the halogenated hydrocarbon, the conditions for the continued reaction are: reacting at 80 - 120 °C for 1 - 4 h, preferably reacting at 80 - 100 °C for 2 - 3 h.

17. According to the preparation method described in claim 1, it is characterized in that: In step (3), based on the weight of the modified asphalt for water-based drilling fluid obtained, the content of the matrix asphalt is 90 wt% - 99.9 wt%, and the content of the modifier is 0.1 wt% - 10 wt%.

18. A modified asphalt for water-based drilling fluid prepared by the method according to any one of claims 1 - 17.

19. An application of a modified asphalt for water-based drilling fluid prepared by the method according to any one of claims 1 - 17 in a drilling fluid.

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