A high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids, its preparation method and application

Abstract

The present invention provides a temperature and salt resistant polyionic liquid lubricant for water-based drilling fluids, its preparation method and application, belonging to the field of drilling technology. The lubricant of the present invention is prepared from the following raw materials in parts by weight: 80-120 parts of water, 10-15 parts of N-hydroxymethylacrylamide, 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. The lubricant of the present invention has a temperature resistance of up to 220°C and a salt tolerance up to saturation, and has excellent temperature and salt resistance and lubricating properties. In addition, the lubricant of the present invention has a low molecular weight, has little influence on the rheological properties of water-based drilling fluids, is easy to disperse, has good environmental protection, and meets the drilling requirements of environmentally sensitive areas.

Description

Technical Field

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

[0002] As the "blood" of drilling engineering, drilling fluids have important functions such as carrying cuttings, balancing formation pressure, stabilizing the wellbore, lubricating and cooling the drill bit, and determine the success or failure of deep drilling. However, in deep formations, there are three ultra-complex and harsh conditions of "ultra-high temperature, ultra-high pressure, and ultra-high salinity". Existing lubricants are prone to degradation under such harsh conditions, cannot effectively adsorb on the surface of drill tools to form a lubricating film, and are difficult to effectively reduce the drilling friction. If the friction torque during drilling is too large, it will bring downhole complex problems such as reduced mechanical drilling speed and frequent sticking during tripping in and out of the hole. In severe cases, it may even lead to major accidents such as drill tool breakage, drill bit dropping, and wellbore abandonment, threatening drilling safety. Therefore, there is an urgent need to develop a lubricant with excellent high-temperature and high-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 oils (such as crude oil, diesel, etc.), vegetable oils, polyol ethers, alkyl glycosides, etc. Although mineral oils have good lubrication effects, they have technical problems such as serious environmental pollution and high fluorescence, which limit their applications. Vegetable oils, ether alcohols, and alkyl glycosides have lower fluorescence and are more environmentally friendly than mineral oils, but they have the disadvantage of insufficient high-temperature resistance. Their high-temperature resistance can be improved through chemical modification. Chinese patent document CN111560238A discloses an environmentally friendly lubricant that synergistically exerts a lubricating effect through cationic alkyl glycosides and quaternized nano-silica, but its high-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 an imidazole-type quaternary cation, an ester group, and a polycarbodiimide structure, and its high-temperature resistance reaches 190°C. Chinese patent document CN114686188A discloses a nucleoside phospholipid drilling fluid lubricant. By carrying out a ring-opening reaction of the epoxy bond with the phosphate group in nucleoside monophosphate, grafting amino groups and sulfonic acid groups, and introducing long fatty chains and sulfonic acid groups in the form of double phospholipids on the structure of nucleoside monophosphate, the high-temperature resistance of the lubricant reaches 150°C. Chinese patent document CN114644910A discloses a soybean lecithin lubricant modified by epichlorohydrin, amine, and nitrogen-containing heterocyclic compounds, and its high-temperature resistance can reach 150°C. Although there are various modification methods for alkyl glycosides and vegetable oils in the current prior art, their high-temperature resistance capabilities still do not reach 220°C. Although there is a rich variety of existing lubricants, their high-temperature and high-salt resistance performances are generally insufficient, and it is difficult to exert effective lubricating effects under high-temperature and high-salt conditions. There is an urgent need to develop a drilling fluid lubricant with high-temperature and high-salt resistance. Summary of the Invention

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

[0005] The present invention is achieved through the following technical solutions:

[0006] A temperature- and salt-resistant polyionic liquid lubricant for water-based drilling fluids is prepared from the following raw materials in parts by weight: 80 - 120 parts of water, 10 - 15 parts of N-hydroxymethylacrylamide, 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.

[0007] According to a preferred embodiment of the present invention, the temperature- and salt-resistant polyionic liquid lubricant for water-based drilling fluids is prepared from the following raw materials in parts by weight: 80 parts of water, 10 parts of N-hydroxymethylacrylamide, 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.

[0008] According to a preferred embodiment of the present invention, the preparation method of 1-vinylpyridine tetrafluoroborate includes the steps of:

[0009] Vinylpyridine and bromoethane are mixed evenly and refluxed and stirred at 65 - 75 °C for 6 - 8 h to obtain an intermediate product; the intermediate product and NH4BF4 are fully dispersed in acetone and refluxed and stirred at 65 - 75 °C for 6 - 8 h, and then distilled under reduced pressure to obtain 1-vinylpyridine tetrafluoroborate. The reaction mechanism is shown in the following formula:

[0010]

[0011] Preferably, the mass ratio of vinylpyridine to bromoethane is 8 - 18:20 - 23, preferably 15:20; the mass ratio of NH4BF4 to vinylpyridine is 12 - 18:8 - 18, preferably 18:15; the mass ratio of NH4BF4 to the volume of acetone is 12 - 18:40 - 60 g / mL.

[0012] According to a preferred embodiment of the present invention, the number average molecular weight of polyethylene glycol methyl ether methacrylate is 2000 - 4000.

[0013] Preferably according to the present invention, the emulsifier is sodium dodecylbenzenesulfonate.

[0014] Preferably according to the present invention, the initiator is 2,2'-azobis(2-methylpropionamidine) dihydrochloride.

[0015] Preferably according to the present invention, the defoamer is n-octanol.

[0016] The preparation method of the high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluid described above includes the steps:

[0017] Disperse N-hydroxymethylacrylamide, 1-vinylpyridinium tetrafluoroborate and (3-acrylamidopropyl) trimethylammonium chloride sufficiently in water, add an emulsifier and polyethylene glycol methyl ether methacrylate, and perform shear emulsification; add an initiator and carry out a reaction; then add a defoamer and mix evenly to obtain the high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluid.

[0018] Preferably according to the present invention, the rotation speed of shear emulsification is 7000 - 9000 r / min, and the shear emulsification time is 10 - 30 min.

[0019] Preferably according to the present invention, the reaction temperature is 60°C - 80°C, the reaction time is 4 - 8 h, and the reaction is carried out under the protection of a protective gas and stirring conditions. The stirring speed is 300 - 500 r / min; the protective gas is nitrogen or argon.

[0020] The application of the high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluid described above in the lubrication of water-based drilling fluid.

[0021] Preferably according to the present invention, the addition amount of the lubricant in the water-based drilling fluid is 0.01 - 0.02 g / mL.

[0022] The technical features and beneficial effects of the present invention are as follows:

[0023] 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 the 1-vinylpyridinium tetrafluoroborate ionic liquid with strong temperature resistance and N-hydroxymethylacrylamide, (3-acrylamidopropyl) trimethylammonium chloride, and polyethylene glycol methyl ether methacrylate with strong adsorption. The obtained lubricant contains strong adsorption groups such as pyridinium cations, quaternary ammonium cations, and hydroxyl groups. 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 the mud cake through molecular forces such as ionic bonds and covalent bonds, forming a dense lubricating film, effectively reducing the friction between the drill tool and the wellbore wall, reducing the risk of sticking the drill, and supporting the safe and efficient drilling of deep complex formations.

[0024] 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.

[0025] 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

[0026] 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.

[0027] 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.

[0028] Preparation Example 1

[0029] Preparation of 1-vinylpyridine-tetrafluoroborate ionic liquid:

[0030] 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

[0031] A high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids is prepared from the following raw materials by mass: 80 g of deionized water, 10 g of N-hydroxymethylacrylamide, 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 of 2000), 0.03 g of emulsifier sodium dodecylbenzenesulfonate, 0.5 g of initiator 2,2'-azobis(2-methylpropionamidine) dihydrochloride, and 1 g of defoamer n-octanol.

[0032] The preparation method of the above high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids includes the steps:

[0033] Add deionized water, N-hydroxymethylacrylamide, 1-vinylpyridine tetrafluoroborate, and (3-acrylamidopropyl) trimethylammonium chloride into a three-necked flask, and stir at 400 rpm for 10 min to fully dissolve the monomers. Then add sodium dodecylbenzenesulfonate and polyethylene glycol methyl ether methacrylate, and shear and emulsify at 8000 rpm for 20 min to form a stable oil-in-water emulsion. Pass nitrogen for 30 min to remove oxygen, heat up to 75 °C, add 2,2'-azobis(2-methylpropionamidine) dihydrochloride to initiate free radical polymerization, and continuously react under magnetic stirring at 400 rpm for 6 h to obtain a transparent solution with a certain viscosity but can flow. Add 1 g of n-octanol and mix evenly to obtain the high-temperature and high-salt resistant polyionic liquid lubricant A1 for water-based drilling fluids. Example 2

[0034] A high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids is as described in Example 1, except that the amount of 1-vinylpyridine tetrafluoroborate used is 10 g; the composition of other raw materials is the same as that in Example 1.

[0035] The preparation method of the above high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids is the same as that in Example 1. The high-temperature and high-salt resistant polyionic liquid lubricant A2 for water-based drilling fluids is obtained. Example 3

[0036] A high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids is as described in Example 1, except that the amount of 1-vinylpyridine tetrafluoroborate used is 10 g and the amount of (3-acrylamidopropyl) trimethylammonium chloride used is 10 g; the composition of other raw materials is the same as that in Example 1.

[0037] The preparation method of the above high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids is the same as that in Example 1. The high-temperature and high-salt resistant polyionic liquid lubricant A3 for water-based drilling fluids is obtained. Example 4

[0038] A high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids, as described in Example 1, except that the dosage of 1-vinylpyridine tetrafluoroborate is 10 g, the dosage of (3-acrylamidopropyl) trimethylammonium chloride is 10 g, and the dosage of polyethylene glycol methyl ether methacrylate is 10 g; the other raw material components are the same as those in Example 1.

[0039] The preparation method of the above high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids is the same as that in Example 1. The high-temperature and high-salt resistant polyionic liquid lubricant A4 for water-based drilling fluids is obtained. Example 5

[0040] A high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids, as described in Example 4, except that:

[0041] 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 components are the same as those in Example 4.

[0042] The preparation method of the above high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids is the same as that in Example 4. The high-temperature and high-salt resistant polyionic liquid lubricant A5 for water-based drilling fluids is obtained. Comparative Example 1

[0043] A high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids, as described in Example 1, except that N-hydroxymethylacrylamide is not added; the other raw material components are the same as those in Example 1.

[0044] The preparation method of the above high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids is as described in Example 1, except that N-hydroxymethylacrylamide is not added; the other preparation steps and conditions are the same as those in Example 1. The high-temperature and high-salt resistant polyionic liquid lubricant D1 for water-based drilling fluids is obtained. Comparative Example 2

[0045] A high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids, as described in Example 1, except that (3-acrylamidopropyl) trimethylammonium chloride is not added; the other raw material components are the same as those in Example 1.

[0046] The preparation method of the above high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids 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 those in Example 1. The high-temperature and high-salt resistant polyionic liquid lubricant D2 for water-based drilling fluids is obtained. Comparative Example 3

[0047] A high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids, as described in Example 1, except that: 1-vinylpyridine is used instead of 1-vinylpyridine tetrafluoroborate; the other raw material components are the same as in Example 1.

[0048] The preparation method of the above high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids, as described in Example 1, except that: 1-vinylpyridine is used instead of 1-vinylpyridine tetrafluoroborate; the other preparation steps and conditions are the same as in Example 1. A high-temperature and high-salt resistant polyionic liquid lubricant D3 for water-based drilling fluids is obtained. Comparative Example 4

[0049] A high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids, as described in Example 1, except that: 1-vinylpyridine tetrafluoroborate is not added; the other raw material components are the same as in Example 1.

[0050] The preparation method of the above high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids, as described in Example 1, except that: 1-vinylpyridine tetrafluoroborate is not added; the other preparation steps and conditions are the same as in Example 1. A high-temperature and high-salt resistant polyionic liquid lubricant D4 for water-based drilling fluids is obtained. Comparative Example 5

[0051] A high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids, as described in Example 1, except that: polyethylene glycol methyl ether methacrylate is not added; the other raw material components are the same as in Example 1.

[0052] The preparation method of the above high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids, 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 in Example 1. A high-temperature and high-salt resistant polyionic liquid lubricant D5 for water-based drilling fluids is obtained. Comparative Example 6

[0053] A high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids, as described in Example 1, except that: N-hydroxymethylacrylamide is replaced by acrylamide; the other raw material components are the same as in Example 1.

[0054] The preparation method of the above high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids, as described in Example 1, except that: N-hydroxymethylacrylamide is replaced by acrylamide; the other preparation steps and conditions are the same as in Example 1. A high-temperature and high-salt resistant polyionic liquid lubricant D6 for water-based drilling fluids is obtained. Comparative Example 7

[0055] A high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids, as described in Example 1, except that: polyethylene glycol methyl ether methacrylate is replaced by methyl methacrylate; the other raw material components are the same as those in Example 1.

[0056] The preparation method of the above high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids, 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 those in Example 1. The high-temperature and high-salt resistant polyionic liquid lubricant D7 for water-based drilling fluids is obtained. Comparative Example 8

[0057] A high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids, 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 components are the same as those in Example 1.

[0058] The preparation method of the above high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids, 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; the other preparation steps and conditions are the same as those in Example 1. The high-temperature and high-salt resistant polyionic liquid lubricant D8 for water-based drilling fluids is obtained. Comparative Example 9

[0059] A high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids, as described in Example 1, except that: (3-acrylamidopropyl) trimethyl ammonium chloride is replaced by acryloyloxyethyl trimethyl ammonium chloride, and the other raw material components are the same as those in Example 1.

[0060] The preparation method of the above high-temperature and high-salt resistant polyionic liquid lubricant for water-based drilling fluids, as described in Example 1, except that: (3-acrylamidopropyl) trimethyl ammonium chloride is replaced by acryloyloxyethyl trimethyl ammonium chloride; the other preparation steps and conditions are the same as those in Example 1. The high-temperature and high-salt resistant polyionic liquid lubricant D9 for water-based drilling fluids is obtained.

[0061] Application test example

[0062] Preparation of fresh water-based mud: Add 400 mL of deionized water to a slurry cup, add 0.7 g of anhydrous sodium carbonate and 20.0 g of sodium-based bentonite, stir for 20 min under the condition of a stirring rate of 10000 r / min, stop stirring twice during the stirring process to scrape off the bentonite adhering to the stirring cup with a glass rod, and obtain fresh water-based mud after sealing and curing at room temperature for 24 h.

[0063] Preparation of saturated brine base slurry: 144 g of sodium chloride was added to 400 mL of fresh water base slurry and stirred at a rate of 10,000 r / min for 20 min to obtain saturated brine base slurry.

[0064] Drilling fluid preparation: 4 g of the lubricants of Examples 1-5 and Comparative Examples 1-9 were respectively added to 400 mL of fresh water base slurry and stirred at a rate of 10,000 r / min for 20 min to obtain fresh water drilling fluids F1-F5 and DF1-DF9. According to the same method, 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.

[0065] 1. According to the petroleum and natural gas industry standard GB / T 29170-2012 "Petroleum and natural gas industry - Drilling fluid laboratory testing", the apparent viscosity (AV, mPa·s), plastic viscosity (PV, mPa·s), yield point (YP, Pa), and API filtration loss FL of drilling fluids F1-F5 and fresh water base slurry without lubricant before and after aging at 220°C for 16 h were measured. API (at 25°C, 100 psi), and the results are shown in Table 1.

[0066] Table 1. Drilling fluid performance test

[0067]

[0068] As can be seen from Table 1, after adding the lubricants A1-A5 of the present invention, the increase in the apparent viscosity and plastic viscosity of the drilling fluid before and after aging at 220°C is less than 5 mPa·s compared with the fresh water base slurry, the increase in shear force is less than 1.0 Pa, and the FL after aging at 220°C API is 38.8, 38.0, 37.2, 36.8, and 38.4 mL respectively, and 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 low molecular weight, has no obvious effect on the rheological properties of the drilling fluid, and is beneficial to reducing the filtration loss.

[0069] 2. Refer to the standard QSY 17088-2016 "Technical Specification for Liquid Lubricants for Drilling Fluids", and use the EP-2A extreme pressure lubrication tester to test the lubrication coefficients of fresh water drilling fluids F1-F5 and DF1-DF9 before and after aging at 220°C for 16 hours. During the test, the stainless steel ring of the extreme pressure lubrication tester will simulate the drill string, apply a certain load to it, and press it tightly against the stainless steel block acting as the wellbore wall. Both the stainless steel ring and the stainless steel block are immersed in the drilling fluid sample. Use the NF-2 mud cake adhesion coefficient tester to test the mud cake adhesion coefficients of fresh water drilling fluids F1-F5 and DF1-DF9 before and after aging at 220°C for 16 hours. Calculate the lubrication coefficient, lubrication coefficient reduction rate, mud cake adhesion coefficient, and mud cake adhesion coefficient reduction rate according to the following formula. The experimental results are shown in Table 2-5.

[0070] The lubrication coefficient θ is calculated according to formula (1):

[0071]

[0072] The lubrication coefficient reduction rate is calculated according to formula (2):

[0073]

[0074] η—Lubrication coefficient reduction rate, %;

[0075] θ0—Lubrication coefficient of the drilling fluid without adding lubricant;

[0076] θ1—Lubrication coefficient of the drilling fluid after adding lubricant.

[0077] The mud cake adhesion coefficient is calculated according to formula (3):

[0078]

[0079] f—Mud cake adhesion coefficient;

[0080] M—Reading of the torque meter, N·m;

[0081] The mud cake adhesion coefficient reduction rate β is calculated according to formula (4).

[0082]

[0083] β—Lubrication coefficient reduction rate, %;

[0084] w0—Mud cake adhesion coefficient without adding lubricant;

[0085] w1—Mud cake adhesion coefficient after adding lubricant.

[0086] Table 2. Evaluation of the Lubrication Coefficient Reduction Rate of Lubricants

[0087]

[0088] Table 3. Evaluation of the reduction rate of the lubrication coefficient of the lubricant

[0089]

[0090] Table 4. Evaluation of the reduction rate of the mud cake adhesion coefficient of the lubricant

[0091]

[0092] Table 5. Evaluation of the reduction rate of the mud cake adhesion coefficient of the lubricant

[0093]

[0094] It can be seen from the experimental results that in the fresh water base slurry, after adding the lubricant prepared in the examples of the present invention, the reduction rate of the lubrication coefficient of the drilling fluid before aging is greater than 85%, and after aging at 220 °C, the reduction rate of the lubrication coefficient is greater than 70%. The reduction rate of the mud cake adhesion coefficient before aging is greater than 70%, and the reduction rate of the mud cake adhesion coefficient after aging at 220 °C is greater than 60%. The experimental results show that due to the ionic liquid unit and strong adsorption groups such as hydroxyl, amide, and pyridinium in the lubricant of the present invention, the temperature resistance can reach 220 °C, and it can effectively reduce the frictional resistance under high temperature conditions, reduce the risk of sticking and jamming, and improve the safety and efficiency of drilling.

[0095] It can be known from the experimental results of the comparative examples that when N-hydroxymethylacrylamide is removed or N-hydroxymethylacrylamide is replaced by acrylamide, the amide or hydroxyl group is missing in the lubricant, and the adsorption performance is weakened, resulting in a decrease in lubrication performance. Similarly, when there is a quaternary ammonium cation in the lubricant structure, the lubricant can be tightly adsorbed on the metal surface through electrostatic force. However, after removing (3-acrylamidopropyl) trimethylammonium chloride, the adsorption performance of the lubricant is weakened and the lubrication performance decreases. When the temperature-resistant (3-acrylamidopropyl) trimethylammonium chloride is replaced by the temperature-sensitive acryloyloxyethyltrimethylammonium chloride, the adsorption performance of the lubricant after high-temperature aging is greatly weakened, resulting in a decrease in lubrication performance. The ionic liquid 1-vinylpyridine-tetrafluoroborate monomer contains a positively charged pyridinium ion, and the six-membered pyridine ring has a π bond similar to that of a benzene ring, with strong chemical stability, making the lubricant have excellent adsorption and lubrication performance. After replacing it with 1-vinylpyridine, the temperature resistance and adsorption performance of the lubricant both decrease, resulting in poor lubrication performance after aging at 220 °C. When the ionic liquid 1-vinylpyridine-tetrafluoroborate is removed, the lubrication effect of the lubricant after aging at 220 °C is greatly reduced. When the ester monomer polyethylene glycol methyl ether methacrylate is removed, or replaced by methyl methacrylate, or the high molecular weight polyethylene glycol methyl ether methacrylate is replaced by the 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 the frictional resistance.

[0096] 3. Refer to the standard QSY 17088-2016 "Technical Specification for Liquid Lubricants for Drilling Fluids", and use the EP-2A extreme pressure lubrication instrument and NF-2 mud cake adhesion coefficient tester 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 and DSF1-DSF9 before and after aging at 220°C for 16 h. The experimental results are shown in Tables 6-9.

[0097] Table 6. Evaluation of the Lubrication Coefficient Reduction Rate of Lubricants in Saturated Brine Base Slurry

[0098]

[0099] Table 7. Evaluation of the Lubrication Coefficient Reduction Rate of Lubricants in Saturated Brine Base Slurry

[0100]

[0101] Table 8. Evaluation of the Mud Cake Adhesion Coefficient Reduction Rate of Lubricants in Saturated Brine Base Slurry

[0102]

[0103] Table 9. Evaluation of the Mud Cake Adhesion Coefficient Reduction Rate of Lubricants in Saturated Brine Base Slurry

[0104]

[0105] It can be seen from the experimental results that under saturated salt conditions, after adding the lubricants A1-A5 of the embodiments of the present invention, the lubrication coefficient reduction rates of drilling fluids SF1-SF4 before aging are all greater than 80%, and the mud cake adhesion coefficient reduction rates are all greater than 70%. After aging at 220°C, the lubrication coefficient reduction rates of drilling fluids SF1-SF4 are all greater than 60%, and the mud cake adhesion coefficient reduction rates are all greater than 60%. Since the lubricant has pyridinium cations and quaternary ammonium cation side chains 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 string under high-temperature and high-salt conditions, and the ester group can form a dense lubricating film on the surface of the drill string, thereby effectively reducing the frictional resistance. The experimental results show that the lubricant of the present invention has a temperature resistance of 220°C and a salt resistance up to saturation.

[0106] 4. Test the fluorescence level and foaming rate of the lubricants A1-A5 prepared in the embodiments of the present invention. Add the lubricants A1-A5 prepared in the embodiments to 300 mL (V0) of deionized water and saturated sodium chloride brine respectively. The mass ratio of the lubricant to the volume of deionized water or saturated sodium chloride brine is 0.01 g / mL. Age at 220°C for 16 h, stir at a rate of 11,000 r / min for 10 minutes, let stand for 30 s after stirring ends, read the liquid volume and record it as V1. The foaming rate M (%) is calculated according to the following formula:

[0107]

[0108] M—the foaming rate, %.

[0109] V0—the initial volume of fresh water and saturated brine, mL;

[0110] V1—the volume of fresh water and saturated brine after being stirred at a rate of 11,000 r / min for 10 minutes and then left standing for 30 s, mL.

[0111] Table 10. Fluorescence level and foaming rate test of lubricants

[0112]

[0113] As can be seen from Table 10, the fluorescence level of the lubricants A1 - A5 of the present invention is Grade 2, within the range of 1 - 8 grades, and does not affect mud logging. Moreover, after the fresh water and saturated brine containing the lubricant of the present invention are stirred at a high speed of 11,000 r / min for 10 minutes, the foaming rate is less than 5%, indicating that the lubricant of the present invention has little foaming and is convenient for on-site use.

[0114] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0115] In addition, it should be noted that, in the case of no conflict, the various specific technical features described in the above specific embodiments can be combined in any appropriate manner. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0116] Furthermore, any combination can be made between various different embodiments of the present invention as long as it does not violate the idea of the present invention, and it should also be regarded as the content 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 method comprises 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; The number average molecular weight of polyethylene glycol methyl ether methacrylate is 2000-4000.

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 emulsifier is sodium dodecylbenzene sulfonate.

6. 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.

7. 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.

8. 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 7, comprising the steps of: 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.

9. Use of the temperature-resistant and salt-resistant polyionic liquid lubricant for water-based drilling fluid as claimed in any one of claims 1 to 7 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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