Water-in-oil-based drilling fluid and preparation method thereof

Abstract

The invention discloses a water-in-oil based drilling fluid and a preparation method thereof. The water-in-oil-based drilling fluid comprises the following components in percentage by mass: 0.5-5% of an emulsifier, 0.5-5% of a water-in-oil-based additive and the balance of water. 1-3% of organic soil; 1-5% of cation modified high softening point asphalt particles; 87-95% of an oil-water base solution; wherein the cation modified high-softening-point asphalt particles comprise matrix asphalt and a modifier, and the modifier is obtained by activating silicon dioxide with an activating agent. The water-in-oil-based drilling fluid disclosed by the invention can well solve the problem that asphalt particles are difficult to disperse in the drilling fluid and the like, has good plugging and filtrate loss reduction effects, and meanwhile, improves the rock-carrying capacity of the drilling fluid.

Description

Technical Field

[0001] The present invention relates to the technical field of oil drilling and production, and particularly relates to a water-in-oil based drilling fluid and a preparation method thereof. Background Art

[0002] With the gradual development of oil and gas exploration towards deeper layers, the chance of encountering high-temperature and high-pressure formations gradually increases. These all put forward higher requirements for the drilling fluid system. Compared with water-based drilling fluids, oil-based drilling fluids have the characteristics of strong anti-pollution ability, good lubricity, strong inhibition, being conducive to maintaining wellbore stability, being able to protect oil and gas reservoirs to the greatest extent, and being easy to maintain. The excellent high-temperature stability and inhibition of oil-based drilling fluids make their advantages more obvious in drilling complex wells, especially in drilling high-temperature deep wells and water-sensitive formations. It can effectively protect water-sensitive oil and gas reservoirs and increase oil and gas production.

[0003] Oil-based drilling fluids refer to drilling fluids with oil as the continuous phase, which are divided into full oil-based drilling fluids and water-in-oil emulsified drilling fluids. The water content in full oil-based drilling fluids is mostly below 5%. Water-in-oil emulsified drilling fluids are composed of oil, water, emulsifiers, filtration loss reducers, activity balance agents, etc. The water content in the drilling fluid is mostly between 5% and 30%. However, the water content in water-in-oil drilling fluids with high-temperature resistance above 180°C is generally between 5% and 10%, and rarely exceeds 15%. The increase in water content will increase the dynamic shear force of the system, improve the rheology, and enhance the ability to carry cuttings. However, it will reduce its thermal stability and electrical stability. CN1660958A discloses a synthetic-based drilling fluid. Although it can maintain good rheology and electrical stability after aging at 150°C for 16 hours, the highest water content is 25%. The performance under higher temperatures and water contents has not been reported.

[0004] Although oil-based drilling fluids have many advantages, when applied in high-temperature deep wells, the high-temperature resistant treatment agents suitable for them have become one of the factors restricting their development. The filtration loss reducer in the treatment agent is mainly used to control the filtration loss and stability of the drilling fluid system. For this high-temperature and high-pressure operating environment, foreign countries have developed an oil-soluble polymer particle filtration loss reducer with good solubility and strong high-temperature resistance in oil-based drilling fluids. These polymer particles can form a thin and easily deformable mud cake on the outside during the filtration loss process, and the internal polymer particles will block the formation pores. Although it can achieve a good filtration loss reduction effect, the price is expensive.

[0005] Compared with special polymers, asphalt products are low in price and wide in material sources. They are one of the important agent types indispensable in modern drilling engineering at home and abroad, and have comprehensive effects such as good anti-collapse, lubrication, filtration loss reduction, and high-temperature stability. However, general softening point asphalt cannot meet the high-temperature operation requirements in deep wells due to excessive softening or even flowing.

[0006] High softening point asphalt refers to asphalt with a softening point above 100°C, especially above 120°C. High softening point asphalt has relatively wide applications due to its excellent high-temperature resistance. High softening point asphalt can be used in the drilling operations of deep oil and gas fields. As an important component of drilling fluid, it can play a role in plugging, preventing collapse, stabilizing the wellbore, and reducing the filtration loss under high-temperature conditions.

[0007] However, when simple high softening point asphalt particles are applied to the drilling fluid system, especially in the water-in-oil drilling fluid system with a relatively high water content, problems such as easy aggregation and difficult dispersion will occur, affecting the overall performance of the drilling fluid. Summary of the Invention

[0008] Aiming at the problems existing in the prior art, such as easy agglomeration, poor suspension ability and high-temperature resistance during the application of asphalt particles to water-in-oil-based drilling fluid, the present invention provides a water-in-oil-based drilling fluid and its preparation method, which can well solve the problems such as difficult dispersion of asphalt particles in the drilling fluid, achieve good plugging and filtration loss reduction effects, and improve the cuttings carrying capacity of the drilling fluid at the same time.

[0009] The first aspect of the present invention provides a water-in-oil-based drilling fluid, which includes the following components in terms of mass fraction:

[0010]

[0011] Among them, the cation-modified high softening point asphalt particles include matrix asphalt and a modifier, and the modifier is obtained by activating silica with an activator.

[0012] Furthermore, the preparation method of the activator includes: first, synthesizing a cyclic monomer from a nitrile monomer under the action of a catalyst; then carrying out ring-opening polymerization on the above cyclic monomer to form a polymer of the cyclic monomer; finally, hydrolyzing the polymer of the cyclic monomer under acidic conditions to obtain the activator. Specifically:

[0013] (a) Adding the nitrile monomer and the catalyst to a reactor, heating to 90 - 120°C, and then adding an amino alcohol monomer, reacting for 30 - 60 h to obtain a cyclic monomer;

[0014] (b) Mixing the cyclic monomer obtained in step (a), an initiator and the 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;

[0015] (c) Dissolve the polymer of the cyclic monomer obtained in step (b) in hot water, heat under reflux, add hydrochloric acid solution, react for 24 - 72 h, remove the solvent, redissolve the residual polymer in hot water, add 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 the activator.

[0016] Further, in step (a), the nitrile monomer is preferably ultra-dry acetonitrile and / or propionitrile. The catalyst is zinc acetate dihydrate. Among them, 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 - 1:3.

[0017] 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 - 1:3.

[0018] Further, in step (b), after mixing the cyclic monomer, the initiator and the nitrile monomer, the reaction is carried out in a microwave reactor.

[0019] 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.

[0020] Further, in step (b), the stirring is carried out at 20 - 30 °C, preferably at room temperature.

[0021] Further, in step (b), the solvent can be removed 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.

[0022] Further, in step (c), the temperature of the hot water is 40 - 80 °C. The temperature of the heating under reflux is 80 - 120 °C, and the heating under 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 solvent can be removed by rotary evaporation. The drying conditions are: drying in vacuum at 50 - 70 °C for 24 - 72 h.

[0023] Further, the average particle size of the cation-modified high softening point asphalt particles is 60-100 mesh.

[0024] Further, the softening point of the base asphalt is 80-180 °C, preferably at least one of oxidized asphalt, solvent-deoiled asphalt, and natural asphalt.

[0025] Further, based on the weight of the cation-modified high softening point asphalt particles, the content of the modifier is 1%-10%, and the content of the base asphalt is 90%-99%.

[0026] Further, the particle size of the silica is 5 μm-50 μm.

[0027] Further, the emulsifier is a long-chain fatty amide series surfactant, preferably at least one of lauroyl diethanolamine, oleamide, oleoyl diethanolamine, and cocoyl diethanolamine.

[0028] Further, in the oil-water base liquid, by volume ratio, it includes oil phase: water phase = 90:10-60:40;

[0029] Further, in the oil-water base liquid, the oil phase is at least one of diesel oil, biodiesel, white oil, or vegetable oil, preferably white oil; the water phase is an aqueous calcium chloride solution with a mass concentration of 10%-30%.

[0030] Further, in the water-in-oil base drilling fluid, a weighting agent is also included. The addition amount of the weighting agent is such that the density of the drilling fluid reaches 1.50-2.10 g / cm 3 , and the weighting agent is barite and / or limestone.

[0031] The second aspect of the present invention provides a method for preparing a water-in-oil base drilling fluid, including the following steps:

[0032] (1) Prepare cation-modified high softening point asphalt particles;

[0033] (2) Mix the cation-modified high softening point asphalt particles with an emulsifier, organoclay, and an oil-water base liquid to obtain a water-in-oil base drilling fluid.

[0034] Further, in step (2), the addition order of each component is preferably to add the emulsifier to the oil-water base liquid, stir first, add the organoclay, stir second, and then add the cation-modified high softening point asphalt particles, stir third, to obtain a water-in-oil base drilling fluid.

[0035] Further, if it is necessary to adjust the density of the water-in-oil base drilling fluid, a weighting agent is added in step (2).

[0036] Further, in step (2), the time of the first stirring is 10 - 30 minutes, the time of the second stirring is 5 - 10 minutes, and the time of the third stirring is 20 - 40 minutes.

[0037] Further, the method for preparing the cation-modified high softening point asphalt particles in step (1) includes:

[0038] (I) Prepare the modifier;

[0039] (II) Dissolve the base asphalt in an organic solvent, then add the modifier obtained in step (I), and react under stirring to obtain the cation-modified high softening point asphalt.

[0040] Further, in step (I), the method for preparing the modifier includes:

[0041] (i) Mix silica, epoxy 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;

[0042] (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.

[0043] Further, in step (i), the epoxy silane coupling agent is 3-glycidoxypropylmethyldiethoxysilane (GPTMS). The mass-volume ratio of silica to the epoxy silane coupling agent is 1:1 - 3 g / mL; mix silica, the epoxy silane coupling agent, and ethanol, where the volume ratio of the epoxy silane coupling agent to ethanol is 1:1 - 5.

[0044] In steps (i) and (ii), the temperature of the heat under reflux is 80 - 120 °C, and the heat under reflux time is 12 - 36 h.

[0045] 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.

[0046] Further, the ethanol in steps (i) and (ii) is anhydrous ethanol.

[0047] 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.

[0048] Further, in step (ii), the rotation speed of the centrifugal separation is 5000-15000 rpm, and the centrifugal separation 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.

[0049] Further, in step (II), the organic solvent is selected from one or more of chloroform, dichloromethane, toluene, tetrahydrofuran, and carbon tetrachloride. The mass ratio of the organic solvent to the matrix asphalt is 1-20:1.

[0050] Further, in step (II), the rotation speed of the stirring is 80-2000 rpm. The reaction conditions are: the reaction temperature is 50-100 °C, and the reaction time is 2-10 h.

[0051] Further, in step (II), after the reaction, it is frozen and pulverized to obtain cation-modified high softening point asphalt particles with particle sizes meeting the requirements.

[0052] Compared with the prior art, the present invention has the following advantages:

[0053] (1) For the cation-modified high softening point asphalt particles of the present invention, a specific modifier is used, that is, micron SiO₂ treated with a special structure activator. The amine groups contained therein undergo a grafting reaction with the asphalt, solving the problem that micron SiO₂ is prone to agglomeration and difficult to disperse in the asphalt. In addition, the SiO₂ treated with the special structure activator is added to the asphalt, which can effectively increase the softening point of the asphalt. The obtained modified asphalt has high temperature resistance and strong activity, and can continuously play a role at high temperatures when applied to drilling fluids. 2 , and the amine groups contained therein undergo a grafting reaction with the asphalt, solving the problem that micron SiO₂ is prone to agglomeration and difficult to disperse in the asphalt. 2 In addition, the SiO₂ treated with the special structure activator is added to the asphalt, which can effectively increase the softening point of the asphalt. The obtained modified asphalt has high temperature resistance and strong activity, and can continuously play a role at high temperatures when applied to drilling fluids. 2 (2) The surface of the cation-modified high softening point asphalt particles of the present invention is grafted with cationic groups, having strong surface activity and being more easily and stably dispersed uniformly in the drilling fluid, solving the problem that asphalt-based treatment agents are difficult to be stably dispersed in water-based or high water content oil-based drilling fluids; and the surface of the cation-modified high softening point asphalt particles is positively charged, while the wellbore rock formation usually has a negative charge, so it binds more firmly to the wellbore and can better play the effects of plugging and filtrate loss reduction.

[0054] (2) The surface of the cation-modified high softening point asphalt particles of the present invention is grafted with cationic groups, having strong surface activity and being more easily and stably dispersed uniformly in the drilling fluid, solving the problem that asphalt-based treatment agents are difficult to be stably dispersed in water-based or high water content oil-based drilling fluids; and the surface of the cation-modified high softening point asphalt particles is positively charged, while the wellbore rock formation usually has a negative charge, so it binds more firmly to the wellbore and can better play the effects of plugging and filtrate loss reduction. Specific embodiments

[0055] The following non-limiting examples can enable those of ordinary skill in the art to more comprehensively understand the present invention, but do not limit the present invention in any way.

[0056] Example 1

[0057] Preparation of Modifier I

[0058] Add 31.2 mL of ultra-dry acetonitrile and 2.62 g of zinc acetate dihydrate into a 250 mL three-necked flask, heat to 105 °C. After the acetonitrile refluxes, slowly drop 62.5 mL of 2-aminoethanol into it using a constant-pressure dropping funnel, react for 40.5 h, and obtain a cyclic monomer after impurity removal. Mix 23.5 mL of the above cyclic monomer, 0.38 mL of methyl p-toluenesulfonate (MeOTs), and 38.5 mL of ultra-dry acetonitrile, place them in a microwave reactor at 140 °C and react for 50 min. Then add 0.75 mL of a methanol solution of KOH with a concentration of 1 mol / L at 0 °C, stir at room temperature for 12 h to terminate the polymerization. Rotate and evaporate to remove the solvent, dissolve the residual polymer in chloroform and then precipitate and purify it 3 times in n-hexane, and dry it in vacuo at 40 °C for 48 h to obtain a polymer of the cyclic monomer. Dissolve 22.5 g of the above cyclic monomer polymer in hot water at 60 °C, heat and reflux at 115 °C for 15 min, add it to 300 g of hydrochloric acid with a mass concentration of 37%, and react for 36 h. Rotate and evaporate to remove the solvent, redissolve the residual solid in hot water at 60 °C, add NaOH solution to neutralize to a solution pH of 9, centrifuge the precipitated precipitate, discard the supernatant, repeat 3 times, and dry it in vacuo at 65 °C for 48 h to obtain an activator.

[0059] Take 20 g of SiO 2 (particle size 10 μm), 40 mL of GPTMS, and 160 mL of ethanol, add them to a 500 mL flask, and stir and reflux the mixture at 100 °C for 24 h. Then centrifuge the suspension at 11000 rpm for 25 min to remove the supernatant; ultrasonically disperse it with 120 mL of ethanol for 20 min, the ultrasonic dispersion frequency is 20 kHz, remove the supernatant, repeat the washing 3 times, and put the product in an oven at 60 °C for 12 h to obtain an intermediate product. Take 22 g of the activator prepared above and dissolve it in 200 g of ethanol, then add 27.5 g of the intermediate product prepared above, and stir and reflux at 105 °C for 24 h. Then centrifuge the suspension at 11000 rpm for 25 min to remove the supernatant; ultrasonically disperse it with deionized water for 20 min, the ultrasonic dispersion frequency is 20 kHz, remove the supernatant, repeat the washing 3 times, and put the product in an oven at 60 °C for 12 h to obtain Modifier I.

[0060] Example 2

[0061] Preparation of Modifier II

[0062] 46.5 mL of ultra-dry propionitrile and 4.25 g of zinc acetate dihydrate were added to a 250 mL three-necked flask. After heating to 115 °C and refluxing of propionitrile, 72 mL of 3-amino-1-propanol was slowly added dropwise thereto using a constant pressure dropping funnel. The reaction was carried out for 54.5 h, and after impurity removal, a cyclic monomer was obtained. 28.2 mL of the above-mentioned cyclic monomer, 0.62 mL of 3-butynyl p-toluenesulfonate and 49.6 mL of ultra-dry acetonitrile were mixed and placed in a microwave reactor at 150 °C for reaction for 60 min. Then, 1.2 mL of a methanol solution of KOH with a concentration of 1 mol / L was added at 2 °C, and the mixture was stirred at room temperature for 20 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 3 times in n-hexane, and dried in vacuo at 45 °C for 52 h to obtain a polymer of the cyclic monomer. 27.4 g of the above-mentioned cyclic monomer polymer was dissolved in hot water at 70 °C, heated to reflux at 110 °C for 20 min, and added to 250 g of hydrochloric acid with a mass concentration of 36%. The reaction was carried out for 48 h. The solvent was removed by rotary evaporation, and the residual solid was redissolved in hot water at 70 °C, and neutralized with NaOH solution until the pH of the solution was 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 52 h to obtain an activator.

[0063] Take 25 g of SiO 2 (with a particle size of 20 μm), 70 mL of GPTMS and 185 mL of ethanol, and add them to a 500 mL flask. The mixture was stirred and refluxed at 95 °C for 30 h. Then, the suspension was centrifuged at 14000 rpm for 20 min to remove the supernatant; it was ultrasonically dispersed with 150 mL of ethanol for 18 min, and the ultrasonic dispersion frequency was 40 kHz. The supernatant was removed, and this washing was repeated 3 times. The product was placed in an oven at 65 °C for 20 h to obtain an intermediate product. 28.6 g of the activator prepared above was added to 265 g of ethanol and dissolved, and then 37.8 g of the intermediate product prepared above was added. The mixture was stirred and refluxed at 110 °C for 20 h. Then, the suspension was centrifuged at 14000 rpm for 25 min to remove the supernatant; it was ultrasonically dispersed with deionized water for 20 min, and the ultrasonic dispersion frequency was 20 kHz. The supernatant was removed, and this washing was repeated 3 times. The product was placed in an oven at 65 °C for 16 h to obtain modifier II.

[0064] Example 3

[0065] 100 g of eluted asphalt with a softening point of 118.5 °C was placed in 240 g of chloroform. After complete dissolution, the modifier I prepared above was added, and mechanical stirring was carried out at a rotation speed of 1000 rpm, and the reaction was carried out at 85 °C for 4 h. After the reaction was completed, the excess organic solvent was removed by rotary evaporation, frozen at -25 °C for 4 hours, and then pulverized with a universal pulverizer for 50 s. The obtained cation-modified high softening point asphalt particles with an average particle size of 80 mesh contained 5.2 wt% of modifier I.

[0066] Take No. 5 white oil and calcium chloride aqueous solution (concentration 20 wt%), prepare the base fluid according to the oil-water volume ratio (80:20), add 2.5 wt% oleic acid amide, stir at room temperature for 10 min, add 1.2 wt% organoclay, stir for 5 min, add the cation-modified high softening point asphalt particles prepared above accounting for 4.8 wt% of the total amount of the drilling fluid, continue to stir for 20 min, add the weighting agent barite, and adjust the density of the drilling fluid to the required value to obtain a stable water-in-oil drilling fluid.

[0067] Example 4

[0068] Place 100 g of deasphalted asphalt with a softening point of 126.4 °C in 200 g of tetrahydrofuran, fully dissolve it and add the modifier II prepared above, stir using mechanical stirring, with a rotation speed of 1500 rpm, and stir and react at 75 °C for 8 h. After the reaction is completed, use the method of rotary evaporation to remove the excess organic solvent, freeze at -30 °C for 4.5 hours, then crush with a universal crusher for 45 s, and sieve to obtain cation-modified high softening point asphalt particles with an average particle size of 100 mesh. The cation-modified high softening point asphalt particles contain 5.8 wt% of modifier II.

[0069] Take No. 5 white oil and calcium chloride aqueous solution (concentration 30 wt%), prepare the base fluid according to the oil-water volume ratio (70:30), add 2.0 wt% lauroyl diethanolamine, stir at room temperature for 15 min, add 1.0 wt% organoclay, stir for 5 min, add the cation-modified asphalt particles prepared above accounting for 3.6 wt% of the total amount of the drilling fluid and continue to stir for 30 min, add the weighting agent barite, and adjust the density of the drilling fluid to the required value to obtain a stable water-in-oil drilling fluid.

[0070] Example 5

[0071] Place 100 g of oxidized asphalt with a softening point of 132.5 °C in 390 g of chloroform, fully dissolve it and add the modifier I prepared above, stir using mechanical stirring, with a rotation speed of 800 rpm, and stir and react at 65 °C for 6.5 h. After the reaction is completed, the method of rotary evaporation can be used to remove the excess organic solvent, freeze at -30 °C for 6 hours, then crush with a universal crusher for 30 s, and sieve to obtain cation-modified high softening point asphalt particles with an average particle size of 80 mesh. The cation-modified high softening point asphalt particles contain 6.4 wt% of modifier I.

[0072] Take white oil No. 5 and calcium chloride aqueous solution (concentration 25 wt%), prepare the base fluid according to the oil-water volume ratio (75:25), add 1.6 wt% lauroyl diethanolamine, stir at room temperature for 15 min, add 1.4 wt% organoclay, stir for 10 min, add the cation-modified asphalt particles prepared above accounting for 4.5 wt% of the total amount of the drilling fluid, continue to stir for 40 min, add the weighting agent barite, and adjust the density of the drilling fluid to the required value to obtain a stable water-in-oil drilling fluid.

[0073] Example 6

[0074] Place 100 g of oxidized asphalt with a softening point of 152.4 °C in 540 g of chloroform, fully dissolve it and add the modifier II prepared above, stir using mechanical stirring at a rotation speed of 1200 rpm, stir and react at 70 °C for 6 h. After the reaction is completed, remove the excess organic solvent by rotary evaporation, freeze at -35 °C for 7 h, then crush with a universal crusher for 40 s, and screen to obtain cation-modified high softening point asphalt particles with an average particle size of 100 mesh. The cation-modified high softening point asphalt particles contain 6.0 wt% of modifier II.

[0075] Take white oil No. 3 and calcium chloride aqueous solution (concentration 20 wt%), prepare the base fluid according to the oil-water volume ratio (65:35), add 2.2 wt% oleic acid amide, stir at room temperature for 15 min, add 2.5 wt% organoclay, stir for 5 min, add the cation-modified asphalt particles prepared above accounting for 4.0 wt% of the total amount of the drilling fluid, continue to stir for 30 min, add the weighting agent limestone, and adjust the density of the drilling fluid to the required value to obtain a stable water-in-oil drilling fluid.

[0076] Comparative Example 1

[0077] Freeze 100 g of oxidized asphalt with a softening point of 132.5 °C at -30 °C for 6 h, then crush with a universal crusher for 30 s, and screen to obtain modified asphalt particles for drilling fluid with an average particle size of 80 mesh.

[0078] Take white oil No. 5 and calcium chloride aqueous solution (concentration 25 wt%), prepare the base fluid according to the oil-water volume ratio (75:25), add 1.6 wt% lauroyl diethanolamine, stir at room temperature for 15 min, add 1.4 wt% organoclay, stir for 10 min, add the modified asphalt particles prepared above accounting for 4.5 wt% of the total amount of the drilling fluid, continue to stir for 40 min, add the weighting agent barite, and adjust the density of the drilling fluid to the required value to obtain a stable water-in-oil drilling fluid.

[0079] Comparative Example 2

[0080] Take 20 g of SiO 2(Particle size 10 μm), 40 mL of GPTMS and 160 mL of ethanol were added to a 500 mL flask, and the mixture was stirred and refluxed at 100 °C for 24 h. Then, the suspension was centrifuged at 11000 rpm for 25 min to remove the supernatant; it was ultrasonically dispersed in 120 mL of ethanol 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 60 °C for 12 h to obtain modifier III.

[0081] 100 g of oxidized asphalt with a softening point of 132.5 °C was placed in 390 g of chloroform and completely dissolved. The above-prepared modifier III was added, and stirring was carried out using mechanical stirring at a rotation speed of 800 rpm. After stirring at 65 °C for 6.5 h, the excess organic solvent could be removed by rotary evaporation, frozen at -30 °C for 6 h, and then crushed with a universal crusher for 30 s. After screening, modified asphalt particles for drilling fluid with an average particle size of 80 mesh were obtained. The modified asphalt particles contained 6.4 wt% of modifier III.

[0082] Take 5# white oil and calcium chloride aqueous solution (concentration 25 wt%), prepare the base fluid according to the oil-water volume ratio (75:25), add 1.6 wt% of lauroyl diethanolamine, stir at room temperature for 15 min, add 1.4 wt% of organoclay, stir for 10 min, add the above-prepared cationic modified asphalt particles accounting for 4.5 wt% of the total amount of the drilling fluid, continue to stir for 40 min, add the weighting agent barite, and adjust the density of the drilling fluid to the required value to obtain a stable water-in-oil drilling fluid.

[0083] Table 1 Physical and chemical parameters of cationic modified high softening point asphalt particles in each example and modified asphalt particles in the comparative example

[0084]

[0085] Table 2 Performance of water-in-oil base drilling fluids obtained in each example and comparative example

[0086] <![CDATA[ρ / g.cm -3 > AV / mPa.s PV / mPa.s YP / Pa YP / PV <![CDATA[FL HTHP / mL]]> ES / V Example 3 1.7 44.2 31.5 14.8 0.47 6.0 1620 Example 4 1.8 43.5 30.4 14.0 0.46 6.5 1680 Example 5 1.6 44.0 33.6 16.2 0.48 5.7 1700 Example 6 1.7 45.2 29.5 13.9 0.47 5.2 1750 Comparative Example 1 1.6 43.4 28.8 8.6 0.30 57.4 1320 Comparative Example 2 1.6 44.2 30.2 11.5 0.38 38.6 1430

[0087] Note: In Table 2, the hot rolling conditions are as follows: time is 16 h, temperature is 180 °C;

[0088] The temperature for rheological property testing is 60 °C;

[0089] The conditions for measuring the high-temperature and high-pressure filtration loss are: 180 °C, 3.5 MPa;

[0090] Among them: AV: apparent viscosity,

[0091] PV: plastic viscosity,

[0092] YP: yield point,

[0093] YP / PV: yield point / plastic viscosity ratio,

[0094] FL HTHP : High temperature and high pressure fluid loss volume,

[0095] ES: Demulsification voltage.

Claims

1. A water-in-oil-based drilling fluid, characterized in that: by mass fraction, it comprises the following components: emulsifier 0.5 - 5%; organophilic clay 1 - 3%; cation-modified high softening point asphalt particles 1 - 5%; oil-water base fluid 87 - 95%; wherein, the cation-modified high softening point asphalt particles include matrix asphalt and a modifier, and the modifier is obtained by activating silica with an activator.

2. The water-in-oil-based drilling fluid according to claim 1, characterized in that: The preparation method of the activator includes: First, synthesize a cyclic monomer from a nitrile monomer under the action of a catalyst; then subject the above cyclic monomer to ring-opening polymerization to form a polymer of the cyclic monomer; finally, hydrolyze the polymer of the cyclic monomer under acidic conditions to obtain the activator.

3. The water-in-oil-based drilling fluid according to claim 2, characterized in that: The preparation method of the activator includes: (a) Add the nitrile monomer and the catalyst to a reactor, heat to 90 - 120 °C, then add the amino alcohol monomer, and react for 30 - 60 h to obtain a cyclic monomer; (b) Mix the cyclic monomer obtained in step (a), an initiator, and the 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; (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 an NaOH solution until the pH of the solution is 9 - 10, precipitate by centrifugation, remove the supernatant, repeat 2 - 3 times, and dry to obtain the activator.

4. The water-in-oil-based drilling fluid according to claim 3, characterized in that: In step (a), the nitrile monomer is superdry acetonitrile and / or propionitrile; the catalyst is zinc acetate dihydrate; the volume-mass ratio of the addition amount of the nitrile monomer to the catalyst 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 addition amount of the nitrile monomer to the amino alcohol monomer is 1:1 - 3.

5. The water-in-oil-based drilling fluid 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 preferably superdry acetonitrile and / or propionitrile; the volume ratio of the addition amount of the initiator to the cyclic monomer is 0.01 - 0.1:1; the volume ratio of the cyclic monomer to the nitrile monomer is 1:1 - 3; 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.

6. The water-in-oil-based drilling fluid according to claim 3, 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.

7. The water-in-oil based drilling fluid according to claim 1, characterized in that: the matrix asphalt is asphalt with a softening point of 80 - 180°C, preferably at least one of oxidized asphalt, solvent-deoiled asphalt, and natural asphalt.

8. The water-in-oil based drilling fluid according to claim 1, characterized in that: calculated by the weight of the cation-modified high softening point asphalt particles, the content of the modifier is 1% - 10%, and the content of the matrix asphalt is 90% - 99%.

9. The water-in-oil based drilling fluid according to claim 1, characterized in that: the particle size of the silicon dioxide is 5 μm - 50 μm.

10. The water-in-oil based drilling fluid according to claim 1, characterized in that: the emulsifier is a long-chain fatty amide series surfactant, preferably at least one of lauroyl diethanolamine, oleic acid amide, oiloyl diethanolamine, and coconut oil diethanolamine.

11. A preparation method of the water-in-oil based drilling fluid according to any one of claims 1 - 10, characterized in that: comprises the following steps: (1) Prepare cation-modified high softening point asphalt particles; (2) Mix the cation-modified high softening point asphalt particles with an emulsifier, organophilic clay, and an oil-water base liquid to obtain a water-in-oil based drilling fluid.

12. The preparation method according to claim 11, characterized in that: the method for preparing cation-modified high softening point asphalt particles in step (1) includes: (I) Prepare a modifier; (II) Add the matrix asphalt to an organic solvent for dissolution, then add the modifier obtained in step (I), and react under stirring to obtain cation-modified high softening point asphalt.

13. The preparation method according to claim 12, characterized in that: in step (I), the preparation method of the modifier includes: (i) Mix silicon dioxide, an 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 an 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.

14. The preparation method according to claim 13, characterized in that: in step (i), the epoxy-type silane coupling agent is 3-glycidoxypropylmethyldiethoxysilane; the mass-volume ratio of silicon dioxide to the epoxy-type silane coupling agent is 1:1 - 3 g / mL; mix silicon dioxide, the epoxy-type silane coupling agent, and ethanol, wherein the volume ratio of the epoxy-type silane coupling agent to ethanol is 1:1 - 5; And / or, in step (i), the rotational speed of the centrifugal separation is 5000 - 15000 rpm, and the centrifugal separation 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.

15. The preparation method according to claim 13, 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%; the mass ratio of the addition amount of the activator to the intermediate product is 1:1 - 2; And / or, in step (ii), the rotational speed of the centrifugal separation is 5000 - 15000 rpm, and the centrifugal separation 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.

16. The preparation method according to claim 12, characterized in that: in step (II), the organic solvent is selected from one or more of chloroform, dichloromethane, toluene, tetrahydrofuran, and carbon tetrachloride; the mass ratio of the organic solvent to the matrix asphalt is 1 - 20:1; And / or, in step (II), the rotational speed of the stirring is 80 - 2000 rpm; the reaction conditions are: the reaction temperature is 50 - 100 °C, and the reaction time is 2 - 10 h.

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