Temperature-resistant and salt-resistant polyion liquid lubricant for water-based drilling fluid as well as preparation method and application of temperature-resistant and salt-resistant polyion liquid lubricant

Abstract

The invention provides a temperature-resistant and salt-resistant polyion liquid lubricant for a water-based drilling fluid as well as a preparation method and application of the temperature-resistant and salt-resistant polyion liquid lubricant, and belongs to the technical field of drilling. The lubricant disclosed by the invention is prepared from the following raw materials in parts by weight: 80 to 120 parts of water, 10 to 15 parts of N-hydroxymethyl acrylamide, 5 to 10 parts of 1-vinylpyridine-tetrafluoroborate, 5 to 10 parts of (3-acrylamidopropyl) trimethyl ammonium chloride, 5 to 10 parts of polyethylene glycol methyl ether methacrylate, 0.01 to 0.03 part of an emulsifier, 0.20 to 0.80 part of an initiator and 1 to 3 parts of a de-foaming agent. The lubricant disclosed by the invention can resist the temperature of 220 DEG C, can resist the salt to be saturated, and has excellent temperature resistance, salt resistance and lubricating performance. In addition, the lubricant disclosed by the invention is low in molecular weight, small in influence on the rheological property of the water-based drilling fluid, easy to disperse and good in environmental protection property, and meets the drilling requirements of environment-sensitive areas.

Description

Technical Field

[0001] The invention belongs to the technical field of drilling, and in particular relates to a temperature-resistant and salt-resistant polyionic liquid lubricant for water-based drilling fluid, and a preparation method and application thereof. Background Art

[0002] As the "blood" of drilling projects, drilling fluid has important functions such as carrying cuttings, balancing formation pressure, stabilizing the well wall, lubricating and cooling the drill bit, and determines the success or failure of deep drilling. However, deep formations have three super-complex and harsh conditions of "ultra-high temperature, ultra-high pressure, and ultra-high salt". Existing lubricants are easily degraded under these harsh conditions and cannot be effectively adsorbed on the surface of the drill bit to form a lubricating film, making it difficult to effectively reduce drilling friction. If the friction torque during drilling is too large, it will bring about complex downhole problems such as reduced mechanical drilling speed and frequent resistance to drilling. In severe cases, it may even lead to major accidents such as drill bit breakage, drill bit drop, and wellbore scrapping, threatening drilling safety. Therefore, it is urgent to develop a lubricant with excellent high temperature and salt resistance to support safe and efficient drilling in deep formations.

[0003] Existing lubricants can be divided into two categories: liquid lubricants and solid lubricants. Liquid lubricants mainly include mineral oil (such as crude oil, diesel, etc.), vegetable oil, polyol ether, alkyl glycoside, etc. Although mineral oil has a good lubricating effect, it has technical problems such as serious environmental pollution and high fluorescence, which limits its application. Compared with mineral oil, vegetable oil, ether alcohol and alkyl glycoside have low fluorescence and are more environmentally friendly, but have the disadvantage of insufficient temperature resistance. Their temperature resistance can be improved by chemical modification. Chinese patent document CN111560238A discloses an environmentally friendly lubricant, which synergistically exerts lubricating effect through cationic alkyl glycoside and quaternized nano-silica, but the temperature resistance is only 120°C. Chinese patent document CN119193116A discloses a high temperature resistant drilling fluid lubricant, in which the modified alkyl glycoside contains imidazole quaternary ammonium cation, ester group and polycarbodiimide structure, and the temperature resistance reaches 190°C. Chinese patent document CN114686188A discloses a nucleoside phospholipid drilling fluid lubricant. The phosphate group in sodium nucleoside monophosphate is used to open the epoxy bond, graft the amino group and the sulfonic acid group, and introduce the long fatty chain and the sulfonic acid group in the form of diphospholipids into the structure of nucleoside monophosphate, so that the lubricant can resist the temperature up to 150°C. Chinese patent document CN114644910A discloses a soybean lecithin lubricant modified with epichlorohydrin, amine, and nitrogen-containing heterocyclic compound, which can resist the temperature up to 150°C. Although the existing technology has various modification methods for alkyl glycosides and vegetable oils, their temperature resistance has not yet reached 220°C. Although there are a variety of existing lubricants, their temperature resistance and salt resistance are generally insufficient, and it is difficult to exert an effective lubricating effect under high temperature and high salt conditions. It is urgent to develop a drilling fluid lubricant that is resistant to high temperature and high salt. Summary of the invention

[0004] In view of the technical difficulty that the existing lubricants are insufficient in temperature and salt resistance and it is difficult to effectively reduce friction and drag under high temperature and high salt, the present invention provides a temperature and salt resistant polyionic liquid lubricant for water-based drilling fluid and its preparation method and application. The lubricant of the present invention has a temperature resistance of up to 220°C and a salt resistance of up to saturation, and has excellent temperature and salt resistance and lubrication properties. In addition, the lubricant of the present invention has a low molecular weight, has little effect on the rheological properties of the water-based drilling fluid, is easy to disperse, has good environmental protection, and meets the drilling requirements in environmentally sensitive areas.

[0005] The present invention is achieved through the following technical solutions: A temperature-resistant and salt-resistant polyionic liquid lubricant for water-based drilling fluid is prepared from the following raw materials in parts by weight: 80-120 parts of water, 10-15 parts of N-hydroxymethyl acrylamide, 5-10 parts of 1-vinylpyridine-tetrafluoroborate, 5-10 parts of (3-acrylamidopropyl)trimethylammonium chloride, 5-10 parts of polyethylene glycol methyl ether methacrylate, 0.01-0.03 parts of emulsifier, 0.20-0.80 parts of initiator and 1-3 parts of defoamer.

[0006] Preferably according to the present invention, the temperature-resistant and salt-resistant polyionic liquid lubricant for water-based drilling fluid includes the following raw materials in parts by weight: 80 parts of water, 10 parts of N-hydroxymethyl acrylamide, 5-10 parts of 1-vinylpyridine-tetrafluoroborate, 5-10 parts of (3-acrylamidopropyl)trimethylammonium chloride, 5-10 parts of polyethylene glycol methyl ether methacrylate, 0.03 parts of emulsifier, 0.5 parts of initiator, and 1 part of defoaming agent.

[0007] According to the preferred embodiment of the present invention, the preparation method of 1-vinylpyridine-tetrafluoroborate comprises the steps of: Vinyl pyridine and ethyl bromide are mixed evenly, and reacted by stirring under reflux at 65-75°C for 6-8h to obtain an intermediate product; the intermediate product and NH4BF4 are fully dispersed in acetone, and reacted by stirring under reflux at 65-75°C for 6-8h, and then distilled under reduced pressure to obtain 1-vinyl pyridine-tetrafluoroborate. The reaction mechanism is shown in the following formula:

[0008] Preferably, the mass ratio of vinyl pyridine to ethyl bromide is 8-18:20-23, preferably 15:20; the mass ratio of NH4BF4 to vinyl pyridine is 12-18:8-18, preferably 18:15; the mass ratio of NH4BF4 to acetone is 12-18:40-60 g / mL.

[0009] Preferably according to the present invention, the number average molecular weight of polyethylene glycol methyl ether methacrylate is 2000-4000.

[0010] According to the present invention, preferably, the emulsifier is sodium dodecylbenzene sulfonate.

[0011] According to the present invention, the initiator is preferably 2,2'-azobisisobutylamidine dihydrochloride.

[0012] According to the present invention, preferably, the defoaming agent is n-octanol.

[0013] The method for preparing the temperature-resistant and salt-resistant polyionic liquid lubricant for the water-based drilling fluid comprises the following steps: N-hydroxymethyl acrylamide, 1-vinylpyridine-tetrafluoroborate and (3-acrylamidopropyl) trimethylammonium chloride are fully dispersed in water, an emulsifier and polyethylene glycol methyl ether methacrylate are added, and shear emulsification is performed; an initiator is added to react; and then a defoamer is added and mixed uniformly to obtain a temperature-resistant and salt-resistant polyionic liquid lubricant for a water-based drilling fluid.

[0014] Preferably according to the present invention, the rotation speed of shear emulsification is 7000-9000 rpm, and the shear emulsification time is 10-30 min.

[0015] According to the preferred embodiment of the present invention, the reaction temperature is 60°C-80°C, the reaction time is 4-8h, and the reaction is carried out under protective gas protection and stirring conditions. The stirring speed is 300-500 rpm; the protective gas is nitrogen or argon.

[0016] The application of the temperature-resistant and salt-resistant polyionic liquid lubricant for water-based drilling fluid in water-based drilling fluid lubrication.

[0017] Preferably according to the present invention, the amount of lubricant added to the water-based drilling fluid is 0.01-0.02 g / mL.

[0018] The technical features and beneficial effects of the present invention are as follows: 1. The high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid of the present invention is prepared by free radical polymerization of 1-vinylpyridine-tetrafluoroborate ionic liquid with strong temperature resistance and N-hydroxymethyl acrylamide, (3-acrylamidopropyl) trimethylammonium chloride, and polyethylene glycol methyl ether methacrylate with strong adsorption, and the obtained lubricant contains strong adsorption groups such as pyridinium cations, quaternary ammonium cations, and hydroxyls. Under high temperature, high pressure, and high salt conditions, the lubricant of the present invention can be tightly adsorbed on the surface of the drill tool and mud cake through molecular forces such as ionic bonds and covalent bonds to form a dense lubricating film, effectively reducing the friction between the drill tool and the well wall, reducing the risk of stuck drill, and supporting safe and efficient drilling in deep complex formations.

[0019] 2. The lubricant of the present invention has a temperature resistance of 220°C and a salt resistance of saturation. When the addition amount is 0.01 g / mL, the lubrication coefficient reduction rate of fresh water and saturated salt water-based slurries reaches 85% and 65% or more, respectively, and the mud cake adhesion coefficient reduction rate reaches 80% and 60% or more, respectively, and has excellent temperature resistance, salt resistance and lubrication performance. In addition, the lubricant of the present invention has a low molecular weight, a small viscosity-increasing effect in water-based drilling fluids, is easy to disperse, and has good environmental protection, meeting the drilling requirements in environmentally sensitive areas.

[0020] 3. The type of raw materials and the ratio of raw materials used in the lubricant of the present invention have an important influence on the performance of the obtained lubricant. If the type of raw materials or the ratio is not suitable, the performance of the obtained lubricant, i.e., the temperature resistance, salt resistance and lubrication performance will be reduced. The raw material composition of the present invention works together as a whole to achieve the excellent effect of the present invention. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with specific examples so that those skilled in the art can better understand the present invention and implement it, but the examples are not intended to limit the present invention. The materials used in the examples can be obtained from commercial sources unless otherwise specified.

[0022] In Examples 1-4, the number average molecular weight of the polyethylene glycol methyl ether methacrylate used is 2000, in Example 5, the number average molecular weight of the polyethylene glycol methyl ether methacrylate used is 4000, and the number average molecular weight of the polyethylene glycol methyl ether methacrylate used in Comparative Example 8 is 300. The above-mentioned polyethylene glycol methyl ether methacrylate is available from Shanghai Aladdin Biochemical Technology Co., Ltd. Preparation Example 1

[0023] Preparation of 1-vinylpyridine-tetrafluoroborate ionic liquid: Add 15g of vinyl pyridine and 20g of ethyl bromide to a three-necked flask, install a condensing reflux device, reflux and stir at 70°C for 7h to obtain a viscous milky white product, transfer the viscous milky white product and 18g of NH4BF4 to 60mL of acetone, fully disperse, and continue to reflux and stir at 70°C for 7h to obtain a mixture A of a white solid and a reddish brown liquid. Distill the mixed product A in the three-necked flask under reduced pressure while heating at 80-90°C to remove impurities, and cool in an ice bath at -20°C for 2h to obtain a dark brown liquid, namely 1-vinyl pyridine-tetrafluoroborate. Example 1

[0024] A high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluid is prepared from the following raw materials: 80 g of deionized water, 10 g of N-hydroxymethyl acrylamide, 5 g of 1-vinylpyridine-tetrafluoroborate prepared by the method of Preparation Example 1, 5 g of (3-acrylamidopropyl)trimethylammonium chloride, 5 g of polyethylene glycol methyl ether methacrylate (number average molecular weight is 2000), 0.03 g of emulsifier sodium dodecylbenzene sulfonate, 0.5 g of initiator 2,2'-azobisisobutylamidine dihydrochloride, and 1 g of defoaming agent n-octanol.

[0025] The method for preparing the high temperature and high salt resistant polyionic liquid lubricant for the water-based drilling fluid comprises the steps of: Add deionized water, N-hydroxymethyl acrylamide, 1-vinylpyridine-tetrafluoroborate, (3-acrylamidopropyl) trimethylammonium chloride to a three-necked flask, stir at 400 rpm for 10 min to fully dissolve the monomers. Then add sodium dodecylbenzene sulfonate and polyethylene glycol methyl ether methacrylate, and shear emulsify at 8000 rpm for 20 min to form a stable water-in-oil emulsion. Pass nitrogen for 30 min to remove oxygen, heat to 75°C, add 2,2'-azobisisobutylamidine dihydrochloride to initiate free radical polymerization, continue to react for 6 h under magnetic stirring at 400 rpm to obtain a transparent solution with a certain viscosity but flowable, add 1g of n-octanol, mix well to obtain high temperature and high salt resistant polyionic liquid lubricant A1 for water-based drilling fluid. Example 2

[0026] A high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid is as described in Example 1, except that the amount of 1-vinylpyridine-tetrafluoroborate is 10 g; and the other raw material compositions are the same as those in Example 1.

[0027] The preparation method of the above-mentioned high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid is the same as that of Example 1. The high temperature and high salt resistant polyionic liquid lubricant A2 for water-based drilling fluid is obtained. Example 3

[0028] A high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid is as described in Example 1, except that the amount of 1-vinylpyridine-tetrafluoroborate is 10g, the amount of (3-acrylamidopropyl)trimethylammonium chloride is 10g; the other raw material compositions are the same as in Example 1.

[0029] The preparation method of the above-mentioned high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid is the same as that of Example 1. The high temperature and high salt resistant polyionic liquid lubricant A3 for water-based drilling fluid is obtained. Example 4

[0030] A high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid is as described in Example 1, except that: the amount of 1-vinylpyridine-tetrafluoroborate is 10g, the amount of (3-acrylamidopropyl)trimethylammonium chloride is 10g, and the amount of polyethylene glycol methyl ether methacrylate is 10g; the other raw material compositions are the same as in Example 1.

[0031] The preparation method of the above-mentioned high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid is the same as that of Example 1. A high temperature and high salt resistant polyionic liquid lubricant A4 for water-based drilling fluid is obtained. Example 5

[0032] A high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid, as described in Example 4, except that: The polyethylene glycol methyl ether methacrylate with a number average molecular weight of 2000 is replaced by polyethylene glycol methyl ether methacrylate with a number average molecular weight of 4000; the other raw material compositions are the same as those in Example 4.

[0033] The preparation method of the above-mentioned high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid is the same as that of Example 4. The high temperature and high salt resistant polyionic liquid lubricant A5 for water-based drilling fluid is obtained. Comparative Example 1

[0034] A high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid is as described in Example 1, except that: N-hydroxymethyl acrylamide is not added; other raw material compositions are the same as those in Example 1.

[0035] The preparation method of the above-mentioned high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid is as described in Example 1, except that N-hydroxymethyl acrylamide is not added; the other preparation steps and conditions are the same as Example 1. The high temperature and high salt resistant polyionic liquid lubricant D1 for water-based drilling fluid is obtained. Comparative Example 2

[0036] A high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid is as described in Example 1, except that (3-acrylamidopropyl)trimethylammonium chloride is not added; other raw material compositions are the same as those in Example 1.

[0037] The preparation method of the above-mentioned high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid is as described in Example 1, except that (3-acrylamidopropyl)trimethylammonium chloride is not added; the other preparation steps and conditions are the same as Example 1. The high temperature and high salt resistant polyionic liquid lubricant D2 for water-based drilling fluid is obtained. Comparative Example 3

[0038] A high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid is as described in Example 1, except that 1-vinylpyridine is used instead of 1-vinylpyridine-4-fluoroborate; other raw material compositions are the same as those in Example 1.

[0039] The preparation method of the high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid is as described in Example 1, except that 1-vinylpyridine is used instead of 1-vinylpyridine-4-fluoroborate; the other preparation steps and conditions are the same as Example 1. The high temperature and high salt resistant polyionic liquid lubricant D3 for water-based drilling fluid is obtained. Comparative Example 4

[0040] A high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid is as described in Example 1, except that 1-vinylpyridine-tetrafluoroborate is not added; other raw material compositions are the same as those in Example 1.

[0041] The preparation method of the above-mentioned high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid is as described in Example 1, except that 1-vinylpyridine-tetrafluoroborate is not added; the other preparation steps and conditions are the same as Example 1. The high temperature and high salt resistant polyionic liquid lubricant D4 for water-based drilling fluid is obtained. Comparative Example 5

[0042] A high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid is as described in Example 1, except that polyethylene glycol methyl ether methacrylate is not added; other raw material compositions are the same as those in Example 1.

[0043] The preparation method of the above-mentioned high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid is as described in Example 1, except that polyethylene glycol methyl ether methacrylate is not added; the other preparation steps and conditions are the same as Example 1. The high temperature and high salt resistant polyionic liquid lubricant D5 for water-based drilling fluid is obtained. Comparative Example 6

[0044] A high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid is as described in Example 1, except that N-hydroxymethyl acrylamide is replaced by acrylamide; and the other raw material compositions are the same as those in Example 1.

[0045] The preparation method of the high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid is as described in Example 1, except that N-hydroxymethyl acrylamide is replaced by acrylamide; the other preparation steps and conditions are the same as Example 1. The high temperature and high salt resistant polyionic liquid lubricant D6 for water-based drilling fluid is obtained. Comparative Example 7

[0046] A high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid is as described in Example 1, except that polyethylene glycol methyl ether methacrylate is replaced by methyl methacrylate; other raw material compositions are the same as in Example 1.

[0047] The preparation method of the above-mentioned high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid is as described in Example 1, except that polyethylene glycol methyl ether methacrylate is replaced by methyl methacrylate; the other preparation steps and conditions are the same as Example 1. The high temperature and high salt resistant polyionic liquid lubricant D7 for water-based drilling fluid is obtained. Comparative Example 8

[0048] A high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid is as described in Example 1, except that polyethylene glycol methyl ether methacrylate with a number average molecular weight of 2000 is replaced by polyethylene glycol methyl ether methacrylate with an average molecular weight of 300, and the other raw material compositions are the same as in Example 1.

[0049] The preparation method of the above-mentioned high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid is as described in Example 1, except that the polyethylene glycol methyl ether methacrylate with a number average molecular weight of 2000 is replaced with polyethylene glycol methyl ether methacrylate with an average molecular weight of 300; the other preparation steps and conditions are the same as in Example 1. The high temperature and high salt resistant polyionic liquid lubricant D8 for water-based drilling fluid is obtained. Comparative Example 9

[0050] A high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid is as described in Example 1, except that (3-acrylamidopropyl)trimethylammonium chloride is replaced by acryloyloxyethyltrimethylammonium chloride, and the other raw material compositions are the same as those in Example 1.

[0051] The preparation method of the above-mentioned high temperature and high salt resistant polyionic liquid lubricant for water-based drilling fluid is as described in Example 1, except that (3-acrylamidopropyl)trimethylammonium chloride is replaced by acryloyloxyethyltrimethylammonium chloride; the other preparation steps and conditions are the same as Example 1. The high temperature and high salt resistant polyionic liquid lubricant D9 for water-based drilling fluid is obtained. Application test examples

[0052] Preparation of freshwater-based slurry: Add 400 mL of deionized water, 0.7 g of anhydrous sodium carbonate and 20.0 g of sodium bentonite into a slurry cup, and stir for 20 min at a stirring rate of 10,000 r / min. Stop twice during the stirring process and use a glass rod to scrape off the bentonite adhering to the stirring cup. After stirring, seal and cure at room temperature for 24 h to obtain the freshwater-based slurry.

[0053] Preparation of saturated salt water base slurry: Add 144 g of sodium chloride to 400 mL of fresh water base slurry and stir at a rate of 10,000 r / min for 20 min to obtain saturated salt water base slurry.

[0054] Drilling fluid preparation: 4 g of the lubricants of Examples 1-5 and Comparative Examples 1-9 were added to 400 mL of fresh water base slurry, and stirred at 10000 r / min for 20 min to obtain fresh water drilling fluids F1-F5 and DF1-DF9. In the same way, 4 g of the lubricants of Examples 1-5 and Comparative Examples 1-9 were added to 400 mL of saturated brine base slurry to prepare saturated brine drilling fluids SF1-SF5 and DSF1-DSF9.

[0055] 1. According to the petroleum and natural gas industry standard GB / T 29170-2012 "Petroleum and Natural Gas Industry-Drilling Fluid Laboratory Test", the apparent viscosity (AV, mPa·s), plastic viscosity (PV, mPa·s), dynamic shear force (YP, Pa), and API filtration loss FL of drilling fluid F1-F5 and fresh water-based slurry without lubricant before and after aging at 220℃ for 16 hours were measured. API (25°C, 100psi), the results are shown in Table 1.

[0056] Table 1. Drilling fluid performance test

[0057] As can be seen from Table 1, after adding lubricants A1-A5 of the present invention, the apparent viscosity and plastic viscosity of the drilling fluid before and after aging at 220°C increased by less than 5 mPa·s compared with the fresh water base slurry, and the shear force increased by less than 1.0 Pa, and the FL after aging at 220°C API The medium pressure filtration loss is reduced compared with the fresh water base slurry without lubricant. The experimental results show that the high temperature and high salt resistant polyionic liquid lubricant of the present invention has a lower molecular weight, has no obvious effect on the rheological properties of the drilling fluid, and is conducive to reducing the filtration loss.

[0058] 2. With reference to the standard QSY 17088-2016 "Technical Specifications for Liquid Lubricants for Drilling Fluids", the EP-2A extreme pressure lubrication instrument was used to test the lubrication coefficient of freshwater drilling fluids F1-F5, DF1-DF9 before and after aging at 220℃ for 16 hours. During the test, the stainless steel ring of the extreme pressure lubrication instrument will simulate the drill string and apply a certain load to it, so that it is pressed tightly against the stainless steel block that acts as the well wall. The stainless steel ring and the stainless steel block are both immersed in the drilling fluid sample. The NF-2 mud cake adhesion coefficient tester was used to test the mud cake adhesion coefficient of freshwater drilling fluids F1-F5, DF1-DF9 before and after aging at 220℃ for 16 hours. The lubrication coefficient, lubrication coefficient reduction rate, mud cake adhesion coefficient, and mud cake adhesion coefficient reduction rate are calculated according to the following formula. The experimental results are shown in Table 2-5.

[0059] The lubrication coefficient θ is calculated according to formula (1):

[0060] The lubrication coefficient reduction rate is calculated according to formula (2):

[0061] η—lubrication coefficient reduction rate, %; θ0—lubrication coefficient of drilling fluid when no lubricant is added; θ1—Lubrication coefficient of drilling fluid after adding lubricant.

[0062] The mud cake adhesion coefficient is calculated according to formula (3):

[0063] f—mud cake adhesion coefficient; M—torque meter reading, N·m; The reduction rate β of the mud cake adhesion coefficient is calculated according to formula (4).

[0064]

[0065] β—lubrication coefficient reduction rate, %; w0—mud cake adhesion coefficient when no lubricant is added; w1—mud cake adhesion coefficient after adding lubricant.

[0066] Table 2. Evaluation of lubricant lubricity coefficient reduction rate

[0067]

[0068] Table 3. Evaluation of lubricant lubrication coefficient reduction rate

[0069] Table 4. Evaluation of lubricant mud cake adhesion coefficient reduction rate

[0070] Table 5. Evaluation of lubricant mud cake adhesion coefficient reduction rate

[0071] From the experimental results, it can be seen that after adding the lubricant prepared by the embodiment of the present invention to the fresh water-based slurry, the lubrication coefficient reduction rate of the drilling fluid before aging is greater than 85%, and after aging at 220°C, the lubrication coefficient reduction rate is greater than 70%. The mud cake adhesion coefficient reduction rate before aging is greater than 70%, and the mud cake adhesion coefficient reduction rate after aging at 220°C is greater than 60%. The experimental results show that since the lubricant of the present invention has ionic liquid units and strong adsorption groups such as hydroxyl, amide, and pyridinium, the temperature resistance can reach 220°C, and it can effectively reduce friction under high temperature conditions, reduce the risk of adhesion and drill bit sticking, and improve the safety and efficiency of drilling.

[0072] From the experimental results of the comparative example, it is known that when N-hydroxymethyl acrylamide is removed or replaced with acrylamide, the lubricant lacks amide or hydroxyl groups, the adsorption performance is weakened, and the lubrication performance is reduced. Similarly, when quaternary ammonium cations exist in the lubricant structure, the lubricant can be tightly adsorbed on the metal surface by electrostatic force, but after removing (3-acrylamide propyl) trimethyl ammonium chloride, the adsorption performance of the lubricant is weakened, and the lubrication performance is reduced. When the heat-resistant (3-acrylamide propyl) trimethyl ammonium chloride is replaced with the heat-resistant acryloyloxyethyl trimethyl ammonium chloride, the adsorption performance of the lubricant is greatly weakened after high-temperature aging, resulting in a decrease in lubrication performance. The ionic liquid 1-vinyl pyridine-tetrafluoroborate monomer contains positively charged pyridinium ions, and the six-membered pyridine ring has a π bond similar to a benzene ring, and has strong chemical stability, so that the lubricant has excellent adsorption and lubrication properties. After replacing it with 1-vinyl pyridine, the temperature resistance and adsorption performance of the lubricant are reduced, resulting in a deterioration of its lubrication performance after aging at 220°C. When the ionic liquid 1-vinylpyridine-tetrafluoroborate is removed, the lubricating effect of the lubricant is greatly reduced after aging at 220°C. When the ester monomer polyethylene glycol methyl ether methacrylate is removed, or replaced with methyl methacrylate, or the high molecular weight polyethylene glycol methyl ether methacrylate is replaced with low molecular weight polyethylene glycol methyl ether methacrylate, the lubricant cannot form an effective lubricating oil film on the metal surface and cannot effectively reduce friction.

[0073] 3. With reference to the standard QSY 17088-2016 "Technical Specifications for Liquid Lubricants for Drilling Fluids", the EP-2A extreme pressure lubrication tester and NF-2 mud cake adhesion coefficient tester were used to test the lubrication coefficient, mud cake adhesion coefficient, lubrication coefficient reduction rate, and mud cake adhesion coefficient reduction rate of saturated brine drilling fluids SF1-SF5, DSF1-DSF92 before and after aging at 20℃ for 16 hours. The experimental results are shown in Table 6-9.

[0074] Table 6. Evaluation of lubricant slip coefficient reduction in saturated salt water slurry

[0075] Table 7. Evaluation of lubricant slip coefficient reduction in saturated salt water slurry

[0076] Table 8. Evaluation of the reduction rate of mud cake adhesion coefficient of lubricants in saturated salt water base slurry

[0077] Table 9. Evaluation of the reduction rate of mud cake adhesion coefficient of lubricants in saturated salt water base slurry

[0078] It is known from the experimental results that under saturated salt conditions, after adding lubricants A1-A5 of the embodiments of the present invention, the lubrication coefficient reduction rate of drilling fluids SF1-SF4 before aging is greater than 80%, and the mud cake adhesion coefficient reduction rate is greater than 70%. After aging at 220°C, the lubrication coefficient reduction rate of drilling fluids SF1-SF4 is greater than 60%, and the mud cake adhesion coefficient reduction rate is greater than 60%. Since the lubricant has pyridinium cations and quaternary ammonium cation side groups that are insensitive to salt, as well as polar groups such as hydroxyl groups and amides, the lubricant can still be tightly adsorbed on the surface of the drill tool under high temperature and high salt conditions, and the ester group can form a dense lubricating film on the surface of the drill tool, thereby effectively reducing friction. The experimental results show that the lubricant of the present invention is temperature resistant up to 220°C and salt resistant up to saturation.

[0079] 4. Test the fluorescence level and foaming rate of lubricants A1-A5 prepared in the examples of the present invention. Lubricants A1-A5 prepared in the examples were added to 300 mL (V0) of deionized water and saturated sodium chloride brine, respectively, with the volume ratio of the lubricant mass to deionized water or saturated sodium chloride brine being 0.01 g / mL, aged at 220°C for 16 h, stirred at a rate of 11,000 rpm for 10 minutes, and allowed to stand for 30 seconds after the stirring was completed. The liquid volume was read and recorded as V1, and the foaming rate M (%) was calculated as follows:

[0080] M—foaming rate, %.

[0081] V0—initial volume of fresh water and saturated salt water, mL; V1—The volume of fresh water and saturated brine after being stirred at 11000 rpm for 10 minutes and allowed to stand for 30 seconds, mL.

[0082] Table 10. Lubricant fluorescence level and foaming rate test

[0083] It can be seen from Table 10 that the fluorescence level of lubricants A1-A5 of the present invention is level 2, which is within the range of level 1-8 and does not affect mud logging. In addition, after the fresh water and saturated salt water containing the lubricant of the present invention were stirred at 11000 rpm for 10 minutes, the foaming rate was less than 5%, indicating that the lubricant of the present invention has low foaming and is convenient for on-site use.

[0084] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0085] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0086] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A temperature-resistant and salt-resistant polyionic liquid lubricant for water-based drilling fluid, characterized in that: The invention is prepared by the following raw materials in parts by weight: 80-120 parts of water, 10-15 parts of N-hydroxymethyl acrylamide, 5-10 parts of 1-vinylpyridine-tetrafluoroborate, 5-10 parts of (3-acrylamidepropyl)trimethylammonium chloride, 5-10 parts of polyethylene glycol methyl ether methacrylate, 0.01-0.03 parts of emulsifier, 0.20-0.80 parts of initiator and 1-3 parts of defoamer.

2. The temperature-resistant and salt-resistant polyionic liquid lubricant for water-based drilling fluid according to claim 1, characterized in that: The temperature-resistant and salt-resistant polyionic liquid lubricant for water-based drilling fluid is prepared by including the following raw materials in parts by weight: 80 parts of water, 10 parts of N-hydroxymethyl acrylamide, 5-10 parts of 1-vinylpyridine-tetrafluoroborate, 5-10 parts of (3-acrylamidopropyl)trimethylammonium chloride, 5-10 parts of polyethylene glycol methyl ether methacrylate, 0.03 parts of emulsifier, 0.5 parts of initiator and 1 part of defoamer.

3. The temperature-resistant and salt-resistant polyionic liquid lubricant for water-based drilling fluid according to claim 1, characterized in that: The preparation method of 1-vinylpyridine-tetrafluoroborate comprises the steps of: Vinyl pyridine and ethyl bromide are mixed evenly, and the mixture is refluxed and stirred at 65-75° C. for 6-8 hours to obtain an intermediate product; the intermediate product and NH4BF4 are fully dispersed in acetone, and the mixture is refluxed and stirred at 65-75° C. for 6-8 hours, and 1-vinyl pyridine tetrafluoroborate is obtained by vacuum distillation.

4. The temperature-resistant and salt-resistant polyionic liquid lubricant for water-based drilling fluid according to claim 3, characterized in that: The mass ratio of vinyl pyridine to ethyl bromide is 8-18:20-23; the mass ratio of NH4BF4 to vinyl pyridine is 12-18:8-18; the mass ratio of NH4BF4 to acetone is 12-18:40-60 g / mL.

5. The temperature-resistant and salt-resistant polyionic liquid lubricant for water-based drilling fluid according to claim 1, characterized in that: The number average molecular weight of polyethylene glycol methyl ether methacrylate is 2000-4000.

6. The temperature-resistant and salt-resistant polyionic liquid lubricant for water-based drilling fluid according to claim 1, characterized in that: The emulsifier is sodium dodecylbenzene sulfonate.

7. The temperature-resistant and salt-resistant polyionic liquid lubricant for water-based drilling fluid according to claim 1, characterized in that: The initiator is 2,2'-azobisisobutylamidine dihydrochloride.

8. The temperature-resistant and salt-resistant polyionic liquid lubricant for water-based drilling fluid according to claim 1, characterized in that: The defoaming agent is octanol.

9. The method for preparing the temperature-resistant and salt-resistant polyionic liquid lubricant for water-based drilling fluid according to any one of claims 1 to 8, characterized in that: Includes steps: The invention discloses a method for preparing a water-based drilling fluid lubricant comprising: dispersing N-hydroxymethyl acrylamide, 1-vinylpyridine-tetrafluoroborate and (3-acrylamidopropyl) trimethylammonium chloride in water, adding an emulsifier and polyethylene glycol methyl ether methacrylate, and performing shear emulsification; adding an initiator, and reacting; then adding a defoamer, and mixing the mixture evenly to obtain a temperature-resistant and salt-resistant polyionic liquid lubricant for a water-based drilling fluid; The shear emulsification speed is 7000-9000 rpm, and the shear emulsification time is 10-30 min; the reaction temperature is 60°C-80°C, and the reaction time is 4-8 h. The reaction is carried out under protective gas protection and stirring conditions; the stirring speed is 300-500 rpm; the protective gas is nitrogen or argon.

10. Use of the temperature-resistant and salt-resistant polyionic liquid lubricant for water-based drilling fluid according to any one of claims 1 to 8 in lubrication of water-based drilling fluid, characterized in that: The amount of lubricant added to the water-based drilling fluid is 0.01-0.02 g / mL.

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