An oil-based drilling fluid antifreeze agent, a preparation method and application thereof

Abstract

The application belongs to the technical field of oil drilling fluid treating agent, and particularly relates to an oil-based drilling fluid antifreeze agent, a preparation method and application thereof. The application provides an oil-based drilling fluid antifreeze agent, which comprises the following raw materials in parts by weight: 60-80 parts of methyl acrylate, 4-10 parts of diene, 0.5-1.5 parts of an initiator, 0.2-0.6 parts of a chain transfer agent, 10-30 parts of styrene, 5-15 parts of vinyl pyrrolidone and 0.5-1.5 parts of a polymerization inhibitor; the methyl acrylate comprises one or more of methyl myristate, cyclohexyl methacrylate and lauryl methacrylate. The oil-based drilling fluid antifreeze agent provided by the application has little influence on the flow performance of the oil-based drilling fluid and can greatly improve the antifreezing capacity of the oil-based drilling fluid.

Description

Technical Field

[0001] This invention belongs to the technical field of petroleum drilling fluid treatment agents, specifically relating to an oil-based drilling fluid antifreeze agent, its preparation method, and its application. Background Technology

[0002] When drilling with oil-based drilling fluids, during winter operations (below -10°C), if the drilling mud containing the fluid remains stagnant in the mud tank pipeline, it will quickly solidify, becoming immobile and causing pipeline blockages, thus hindering the smooth completion of on-site operations. Alternatively, the on-site mud may solidify in the storage tank due to low temperatures, rendering it unusable despite its presence, significantly increasing drilling costs. This problem arises from two main factors: firstly, some components in the oil-based drilling fluid system, such as saturated fatty acids, tend to precipitate waxy crystals at low temperatures, causing the drilling fluid to solidify easily; secondly, as drilling progresses, underground crude oil intrusion increases the crude oil content in the drilling fluid, and the wax, colloids, and asphaltene contained in the crude oil cause the mud's freezing point to rise rapidly.

[0003] Therefore, there is an urgent need to develop an oil-based drilling fluid antifreeze agent. When added to drilling fluid, this antifreeze agent will not only have little impact on the flow properties (including viscosity and shear stress) of the oil-based drilling fluid, but will also significantly improve the antifreeze ability of the oil-based drilling fluid and solve the problem of low-temperature solidification of drilling mud. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide an oil-based drilling fluid antifreeze, its preparation method, and its application. The oil-based drilling fluid antifreeze provided by this invention has little impact on the flow properties of oil-based drilling fluids and can significantly improve the antifreeze capability of oil-based drilling fluids.

[0005] This invention provides an oil-based drilling fluid antifreeze agent, comprising the following raw materials in parts by weight: 60-80 parts of methacrylate, 4-10 parts of diene, 0.5-1.5 parts of initiator, 0.2-0.6 parts of chain transfer agent, 10-30 parts of styrene, 5-15 parts of vinylpyrrolidone, and 0.5-1.5 parts of polymerization inhibitor. The methacrylates include one or more of tetradecyl methacrylate, cyclohexyl methacrylate, and lauryl methacrylate.

[0006] Preferably, the diene includes 1,5-hexadiene and / or 1,3-pentadiene.

[0007] Preferably, the initiator includes one or more of benzoyl peroxide, azobisisoheptanenitrile, azobisisovalerate, and azobiscyclohexylformonitrile.

[0008] Preferably, the chain transfer agent comprises α-methylstyrene dimer.

[0009] Preferably, the polymerization inhibitor includes one or more of hydroquinone, tert-butylcatechol, hydrophenol monobutyl ether, and diethylhydroxylamine.

[0010] Preferably, the oil-based drilling fluid antifreeze comprises the following raw materials in parts by weight: 60 parts methacrylate, 4 parts diene, 0.5 parts initiator, 0.2 parts chain transfer agent, 30 parts styrene, 15 parts vinylpyrrolidone, and 1 part polymerization inhibitor; Alternatively, it may include: 80 parts methacrylate, 10 parts diene, 1.5 parts initiator, 0.4 parts chain transfer agent, 20 parts styrene, 10 parts vinylpyrrolidone, and 1 part polymerization inhibitor; Alternatively, it may include: 70 parts methacrylate, 7 parts diene, 1.0 part initiator, 0.6 parts chain transfer agent, 30 parts styrene, 15 parts vinylpyrrolidone, and 1 part polymerization inhibitor.

[0011] This invention also provides a method for preparing the oil-based drilling fluid antifreeze described in the above technical solution, comprising the following steps: Methacrylate, diene, initiator and organic solvent are mixed and subjected to a first reaction to obtain a first reaction solution; The first reaction solution and the chain transfer agent are mixed to carry out a second reaction to obtain a second reaction solution; The second reaction solution, styrene, and vinylpyrrolidone are mixed to carry out a third reaction to obtain a third reaction solution; The third reaction solution and the polymerization inhibitor are mixed to carry out a fourth reaction. The organic solvent is removed from the obtained fourth reaction solution to obtain an oil-based drilling fluid antifreeze.

[0012] Preferably, the temperatures of the first reaction, the second reaction, the third reaction and the fourth reaction are independently 80~90℃.

[0013] Preferably, the first reaction takes 0.5 to 1 hour; the second reaction takes 1 to 3 hours; the third reaction takes 2 to 4 hours; and the fourth reaction takes 1 to 2 hours.

[0014] The present invention also provides the application of the oil-based drilling fluid antifreeze agent described in the above technical solution or the oil-based drilling fluid antifreeze agent obtained by the above preparation method in oil-based mud.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention provides an oil-based drilling fluid antifreeze agent, comprising the following raw materials in parts by weight: 60-80 parts of methacrylate, 4-10 parts of diene, 0.5-1.5 parts of initiator, 0.2-0.6 parts of chain transfer agent, 10-30 parts of styrene, 5-15 parts of vinylpyrrolidone, and 0.5-1.5 parts of polymerization inhibitor; wherein the methacrylate includes one or more of tetradecyl methacrylate, cyclohexyl methacrylate, and lauryl methacrylate.

[0016] The raw materials for preparing the oil-based drilling fluid antifreeze of this invention include methacrylate, diene, chain transfer agent, styrene, and vinylpyrrolidone. The resulting polymer contains long alkyl chains or cyclic chains, has a branched structure, and contains ester groups, benzene rings, and nitrogen-containing cyclic compounds. Its addition has little impact on the flow properties of the oil-based drilling fluid and can significantly improve its antifreeze ability, as detailed below: (1) The long alkyl chains (12-14 carbons) or cyclic chains contained therein can not only improve the oil solubility of the polymer, but also can co-crystallize with the wax crystals in the oil-based drilling fluid at low temperature. The polar ester groups and nitrogen-containing cyclic compounds can be adsorbed on the surface of the wax crystals, thereby changing the growth direction of the wax crystals, preventing the wax crystals from forming a three-dimensional network structure, thereby reducing the freezing point of the oil-based drilling fluid and improving the antifreeze ability of the oil-based drilling fluid.

[0017] (2) The present invention introduces diene into the main molecular chain to form a polymer with a certain degree of branching, which makes it more soluble in drilling fluid and more interactive with wax crystals. This not only makes it more effective at preventing freezing, but also, due to its unique branched structure, it has little impact on the viscosity and other properties of the drilling fluid after being added to oil-based drilling fluid.

[0018] (3) By adding a chain transfer agent, the present invention can effectively control the molecular weight of the synthesized polymer, making its molecular weight more concentrated (number average molecular weight 2000~5000), thereby achieving a better antifreeze effect.

[0019] (4) The antifreeze prepared by the present invention not only contains ester groups, but also contains benzene rings and nitrogen-containing rings, which makes it have good high temperature resistance. After aging at high temperature (120°C), it can still play a good role in reducing the solidification point of oil-based mud.

[0020] This invention also provides a method for preparing and applying the oil-based drilling fluid antifreeze described in the above technical solution. The synthesis process is simple, and the application has the advantages of low dosage and good antifreeze effect.

[0021] Test data shows that adding the oil-based drilling fluid antifreeze of the present invention to the old mud in the shale block can lower the freezing point of the old mud by more than 30°C, and the oil-based mud still has good fluidity at lower temperatures. Detailed Implementation

[0022] This invention provides an oil-based drilling fluid antifreeze agent, comprising the following raw materials in parts by weight: 60-80 parts of methacrylate, 4-10 parts of diene, 0.5-1.5 parts of initiator, 0.2-0.6 parts of chain transfer agent, 10-30 parts of styrene, 5-15 parts of vinylpyrrolidone, and 0.5-1.5 parts of polymerization inhibitor. The methacrylates include one or more of tetradecyl methacrylate, cyclohexyl methacrylate, and lauryl methacrylate.

[0023] Unless otherwise specified, all materials and equipment used in this invention are commercially available products in the field.

[0024] In this invention, the methacrylate is preferably tetradecyl methacrylate, cyclohexyl methacrylate, or lauryl methacrylate. The weight percentage of the methacrylate in the raw material is preferably 60, 70, or 80 parts. The methacrylate of this invention contains long alkyl chains or cyclic chains, making the antifreeze product easier to disperse in the oil phase, thereby lowering the pour point.

[0025] In this invention, the diene preferably includes 1,5-hexadiene and / or 1,3-pentadiene. The diene can impart a certain degree of branching to the formed polymer, reducing its impact on properties such as drilling fluid viscosity after addition.

[0026] Based on the weight parts of methacrylate, the weight parts of the diene are preferably 4, 7 or 10 parts.

[0027] In this invention, the initiator preferably includes one or more of benzoyl peroxide, azobisisoheptanenitrile, azobisisovalerate, and azobiscyclohexylformonitrile.

[0028] Based on the weight parts of methacrylate, the weight parts of the initiator are preferably 0.5 parts, 1 part, or 1.5 parts.

[0029] In this invention, the chain transfer agent preferably comprises α-methylstyrene dimer (AMSD). The chain transfer agent can control the molecular weight of the synthesized polymer, with a polymer number-average molecular weight of 2000-5000.

[0030] Based on the weight parts of methacrylate, the weight parts of the chain transfer agent are preferably 0.2 parts, 0.4 parts, or 0.6 parts.

[0031] Based on the weight parts of methacrylate, the weight parts of styrene are preferably 10, 20, or 30 parts. The styrene can act as a steric hindrance, enhancing the pour point depressant effect.

[0032] Based on the weight parts of methacrylate, the preferred weight parts of vinylpyrrolidone are 5, 10, or 15 parts. The addition of vinylpyrrolidone in this invention facilitates adsorption onto the surface of wax crystals.

[0033] In this invention, the polymerization inhibitor preferably includes one or more of hydroquinone, tert-butylcatechol, hydrophenol monobutyl ether, and diethylhydroxylamine.

[0034] Based on the weight parts of methacrylate, the preferred weight parts of the polymerization inhibitor are 1 part.

[0035] In this invention, the oil-based drilling fluid antifreeze preferably comprises the following raw materials in parts by weight: 60 parts methacrylate, 4 parts diene, 0.5 parts initiator, 0.2 parts chain transfer agent, 30 parts styrene, 15 parts vinylpyrrolidone, and 1 part polymerization inhibitor. Alternatively, it may include: 80 parts methacrylate, 10 parts diene, 1.5 parts initiator, 0.4 parts chain transfer agent, 20 parts styrene, 10 parts vinylpyrrolidone, and 1 part polymerization inhibitor; Alternatively, it may include: 70 parts methacrylate, 7 parts diene, 1.0 part initiator, 0.6 parts chain transfer agent, 30 parts styrene, 15 parts vinylpyrrolidone, and 1 part polymerization inhibitor.

[0036] In this invention, the raw materials for preparing the oil-based drilling fluid antifreeze also include an organic solvent (which is removed after preparation), and the organic solvent is preferably toluene.

[0037] This invention also provides a method for preparing the oil-based drilling fluid antifreeze described in the above technical solution, comprising the following steps: Methacrylate, diene, initiator and organic solvent are mixed and subjected to a first reaction to obtain a first reaction solution; The first reaction solution and the chain transfer agent are mixed to carry out a second reaction to obtain a second reaction solution; The second reaction solution, styrene, and vinylpyrrolidone are mixed to carry out a third reaction to obtain a third reaction solution; The third reaction solution and the polymerization inhibitor are mixed to carry out a fourth reaction. The organic solvent is removed from the obtained fourth reaction solution to obtain an oil-based drilling fluid antifreeze.

[0038] In this invention, methacrylate, diene, initiator and organic solvent are mixed to carry out a first reaction to obtain a first reaction solution.

[0039] In this invention, the organic solvent preferably includes toluene, and the mass ratio of toluene to methacrylate is preferably 100:60-80. The mixing of methacrylate, diene, initiator, and organic solvent is preferably carried out as follows: first, the organic solvent, methacrylate, and diene are stirred and mixed; then, the mixture is heated to dissolve the reactants (methacrylate and diene), pressurized, and then the initiator is added dropwise. Nitrogen gas is introduced during the stirring and mixing process to remove oxygen from the reactor; the stirring speed is preferably 300 r / min; the temperature inside the reaction vessel after heating is preferably 60-80°C, specifically 60°C, 70°C, or 80°C; and the pressurization pressure is preferably 0.08 MPa.

[0040] In this invention, the temperature of the first reaction is preferably 80~90℃, more preferably 85±3℃, and the time is preferably 0.5~1h. The first reaction is preferably carried out under a nitrogen atmosphere. During the first reaction, methacrylate and diene undergo a free radical polymerization reaction, and due to the presence of diene, a certain degree of branching can be formed in the product.

[0041] After obtaining the first reaction solution, the present invention mixes the first reaction solution with a chain transfer agent to carry out a second reaction to obtain the second reaction solution.

[0042] In this invention, the temperature of the second reaction is preferably 80-90°C, more preferably 85±3°C, and the time is preferably 1-3 hours. The second reaction is preferably carried out under a nitrogen atmosphere. During the second reaction, the molecular weight of the polymer is controlled by a chain transfer agent.

[0043] After obtaining the second reaction solution, the present invention mixes the second reaction solution, styrene and vinylpyrrolidone to carry out a third reaction to obtain the third reaction solution.

[0044] In this invention, styrene and vinylpyrrolidone are preferably added dropwise to the second reaction solution simultaneously, and the dropwise addition time is preferably controlled within 30 minutes.

[0045] In this invention, the temperature of the third reaction is preferably 80-90°C, more preferably 85±3°C, and the time is preferably 2-4 hours. The third reaction is preferably carried out under a nitrogen atmosphere. This invention incorporates styrene and vinylpyrrolidone for free radical polymerization, which can introduce benzene rings and nitrogen-containing rings.

[0046] After obtaining the third reaction liquid, the present invention mixes the third reaction liquid with a polymerization inhibitor to carry out a fourth reaction, and removes the organic solvent from the obtained fourth reaction liquid to obtain an oil-based drilling fluid antifreeze agent.

[0047] In this invention, the temperature of the fourth reaction is preferably 80-90°C, more preferably 85±3°C, and the time is preferably 1-2 hours. The fourth reaction is preferably carried out under a nitrogen atmosphere. A polymerization inhibitor is added to terminate the reaction in this invention.

[0048] In this invention, the removal of organic solvents is preferably carried out by vacuum distillation; the removal of organic solvents also preferably includes purification with ethanol, filtration and vacuum drying.

[0049] The present invention also provides the application of the oil-based drilling fluid antifreeze agent described in the above technical solution or the oil-based drilling fluid antifreeze agent obtained by the above preparation method in oil-based mud.

[0050] In this invention, the preferred mass ratio of the oil-based drilling fluid antifreeze to the volume of the oil-based drilling mud is 1-2 g: 100 mL. The oil-based drilling mud preferably comprises field mud and No. 3 white oil. In a specific embodiment of this invention, the field mud is sampled from the Yangzhou Huaye block, and the No. 3 white oil is manufactured by Sinopec Jingmen Petrochemical Plant. The volume ratio of the field mud to No. 3 white oil is 10:1.

[0051] Adding the oil-based drilling fluid antifreeze of the present invention to oil-based mud can significantly reduce its freezing point.

[0052] In this embodiment of the invention, the preparation method of the oil-based drilling fluid antifreeze includes the following steps: toluene, methacrylate, and hexadiene are added to a reactor in a certain proportion, and the stirrer is turned on to stir and heat under nitrogen protection to dissolve them; when the polymerization temperature is reached, an initiator is added dropwise at a certain rate, and the reaction is allowed to proceed for a certain period of time; then a chain transfer agent is added and the reaction is allowed to proceed for a certain period of time; then styrene and vinylpyrrolidone are added dropwise and the reaction continues for a period of time; after adding a polymerization inhibitor and reacting for a period of time; finally, toluene is distilled off under reduced pressure, purified with ethanol, filtered, and vacuum dried to obtain the oil-based drilling fluid antifreeze. The synthesis process of this invention is simple, and it has the advantages of requiring a small dosage and providing good antifreeze effect when applied.

[0053] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, of the oil-based drilling fluid antifreeze agent provided by the present invention, its preparation method, and its application, should not be construed as limiting the scope of protection of the present invention.

[0054] Example 1 100 parts by weight of toluene, 60 parts by weight of tetradecyl methacrylate, and 4 parts by weight of 1,3-pentadiene were added to the reactor in proportion. The stirrer was turned on and nitrogen gas was introduced to remove oxygen from the reactor. The temperature was raised to 60°C to allow the reactants to mix and dissolve completely. A pressure of 0.08 MPa was applied. When the polymerization temperature reaches 85℃, 0.5 parts by weight of benzoyl peroxide are added dropwise at a certain rate (15 drops / min), and the reaction is carried out for 1 hour. Then add 0.2 parts by weight of chain transfer agent α-methylstyrene dimer (AMSD) and react for 3 hours; Add 30 parts by weight of styrene and 15 parts by weight of vinylpyrrolidone and continue the reaction for 2 hours; Add 1 part by weight of the polymerization inhibitor diethylhydroxylamine and react for 1 hour; Toluene is then distilled off under reduced pressure, purified with ethanol, filtered, and dried under vacuum. The resulting product is the oil-based drilling fluid antifreeze.

[0055] Example 2 Add 100 parts by weight of toluene, 80 parts by weight of lauryl methacrylate, and 10 parts by weight of 1,5-hexadiene to the reactor in a specific ratio. Turn on the stirrer and purge the reactor with nitrogen to remove oxygen. Heat the reactor to 70°C to ensure that the reactants are fully mixed and dissolved. Apply a pressure of 0.08 MPa. When the polymerization temperature reaches 85℃, 1.5 parts by weight of azodicyclohexyl formonitrile are added dropwise at a certain rate (15 drops / min), and the reaction is carried out for 1 hour. Then add 0.4 parts by weight of chain transfer agent α-methylstyrene dimer (AMSD) and react for 3 hours; Add 20 parts by weight of styrene and 10 parts by weight of vinylpyrrolidone and continue the reaction for 4 hours; Add 1 part by weight of polymerization inhibitor p-phenol monobutyl ether and react for 1 hour; Toluene is then distilled off under reduced pressure, purified with ethanol, filtered, and dried under vacuum. The resulting product is the oil-based drilling fluid antifreeze.

[0056] Example 3 Add 100 parts by weight of toluene, 70 parts by weight of cyclohexyl methacrylate, and 7 parts by weight of 1,5-hexadiene to the reactor in a specific ratio. Turn on the stirrer and purge the reactor with nitrogen to remove oxygen. Heat the reactor to 80°C to ensure that the reactants are fully mixed and dissolved. Apply a pressure of 0.08 MPa. When the polymerization temperature reaches 85℃, 1.0 parts by weight of azobisisoheptanenitrile are added dropwise at a certain rate (15 drops / min), and the reaction is carried out for 1 hour. Then add 0.6 parts by weight of chain transfer agent α-methylstyrene dimer (AMSD) and react for 3 hours; Add 30 parts by weight of styrene and 15 parts by weight of vinylpyrrolidone and continue the reaction for 4 hours; Add 1 part by weight of hydroquinone, a polymerization inhibitor, and react for 1 hour; Toluene is then distilled off under reduced pressure, purified with ethanol, filtered, and dried under vacuum. The resulting product is the oil-based drilling fluid antifreeze.

[0057] Comparative Example 1 (using methyl methacrylate) 100 parts by weight of toluene, 60 parts by weight of methyl methacrylate, and 4 parts by weight of 1,3-pentadiene were added to the reactor in proportion. The stirrer was turned on and nitrogen gas was introduced to remove oxygen from the reactor. The temperature was raised to 60°C to allow the reactants to mix and dissolve completely. A pressure of 0.08 MPa was applied. When the polymerization temperature reaches 85℃, 0.5 parts by weight of benzoyl peroxide are added dropwise at a certain rate (15 drops / min), and the reaction is carried out for 1 hour. Then add 0.2 parts by weight of chain transfer agent α-methylstyrene dimer (AMSD) and react for 3 hours; Add 30 parts by weight of styrene and 15 parts by weight of vinylpyrrolidone and continue the reaction for 2 hours; Add 1 part by weight of the polymerization inhibitor diethylhydroxylamine and react for 1 hour; Toluene is then distilled off under reduced pressure, purified with ethanol, filtered, and dried under vacuum. The resulting product is the oil-based drilling fluid antifreeze.

[0058] Comparative Example 2 (branching without the addition of diene) Add 100 parts by weight of toluene and 60 parts by weight of tetradecyl methacrylate to the reactor in a certain proportion, turn on the stirrer and purge the oxygen in the reactor with nitrogen, raise the temperature to 60°C to make the reactants fully mix and dissolve, and apply a pressure of 0.08 MPa. When the polymerization temperature reaches 85℃, 0.5 parts by weight of benzoyl peroxide are added dropwise at a certain rate (15 drops / min), and the reaction is carried out for 1 hour. Then add 0.2 parts by weight of chain transfer agent α-methylstyrene dimer (AMSD) and react for 3 hours; Add 30 parts by weight of styrene and 15 parts by weight of vinylpyrrolidone and continue the reaction for 2 hours; Add 1 part by weight of the polymerization inhibitor diethylhydroxylamine and react for 1 hour; Toluene is then distilled off under reduced pressure, purified with ethanol, filtered, and dried under vacuum. The resulting product is the oil-based drilling fluid antifreeze.

[0059] Comparative Example 3 (without chain transfer agent) 100 parts by weight of toluene, 60 parts by weight of tetradecyl methacrylate, and 4 parts by weight of 1,3-pentadiene were added to the reactor in proportion. The stirrer was turned on and nitrogen gas was introduced to remove oxygen from the reactor. The temperature was raised to 60°C to allow the reactants to mix and dissolve completely. A pressure of 0.08 MPa was applied. When the polymerization temperature reaches 85℃, 0.5 parts by weight of benzoyl peroxide are added dropwise at a certain rate (15 drops / min), and the reaction is carried out for 4 hours. Add 30 parts by weight of styrene and 15 parts by weight of vinylpyrrolidone and continue the reaction for 2 hours; Add 1 part by weight of the polymerization inhibitor diethylhydroxylamine and react for 1 hour; Toluene is then distilled off under reduced pressure, purified with ethanol, filtered, and dried under vacuum. The resulting product is the oil-based drilling fluid antifreeze.

[0060] Comparative Example 4 (without styrene monomer) 100 parts by weight of toluene, 60 parts by weight of tetradecyl methacrylate, and 4 parts by weight of 1,3-pentadiene were added to the reactor in proportion. The stirrer was turned on and nitrogen gas was introduced to remove oxygen from the reactor. The temperature was raised to 60°C to allow the reactants to mix and dissolve completely. A pressure of 0.08 MPa was applied. When the polymerization temperature reaches 85℃, 0.5 parts by weight of benzoyl peroxide are added dropwise at a certain rate (15 drops / min), and the reaction is carried out for 1 hour. Then add 0.2 parts by weight of chain transfer agent α-methylstyrene dimer (AMSD) and react for 3 hours; Add 15 parts by weight of vinylpyrrolidone and continue the reaction for 2 hours; Add 1 part by weight of the polymerization inhibitor diethylhydroxylamine and react for 1 hour; Toluene is then distilled off under reduced pressure, purified with ethanol, filtered, and dried under vacuum. The resulting product is the oil-based drilling fluid antifreeze.

[0061] Comparative Example 5 (without vinylpyrrolidone monomer) 100 parts by weight of toluene, 60 parts by weight of tetradecyl methacrylate, and 4 parts by weight of 1,3-pentadiene were added to the reactor in proportion. The stirrer was turned on and nitrogen gas was introduced to remove oxygen from the reactor. The temperature was raised to 60°C to allow the reactants to mix and dissolve completely. A pressure of 0.08 MPa was applied. When the polymerization temperature reaches 85℃, 0.5 parts by weight of benzoyl peroxide are added dropwise at a certain rate (15 drops / min), and the reaction is carried out for 1 hour. Then add 0.2 parts by weight of chain transfer agent α-methylstyrene dimer (AMSD) and react for 3 hours; Add 30 parts by weight of styrene and continue the reaction for 2 hours; Add 1 part by weight of the polymerization inhibitor diethylhydroxylamine and react for 1 hour; Toluene is then distilled off under reduced pressure, purified with ethanol, filtered, and dried under vacuum. The resulting product is the oil-based drilling fluid antifreeze.

[0062] Comparative Example 6 100 parts by weight of toluene, 60 parts by weight of tetradecyl methacrylate, 4 parts by weight of 1,3-pentadiene, 0.5 parts by weight of benzoyl peroxide, 0.2 parts by weight of chain transfer agent α-methylstyrene dimer (AMSD), 30 parts by weight of styrene, and 15 parts by weight of vinylpyrrolidone were added to the reactor in proportion. The stirrer was turned on and nitrogen gas was introduced to remove oxygen from the reactor. The temperature was raised to 60°C to ensure that the reactants were fully mixed and dissolved. A pressure of 0.08 MPa was applied. When the polymerization temperature reaches 85°C, the reaction is carried out at this temperature for 6 hours. Add 1 part by weight of the polymerization inhibitor diethylhydroxylamine and react for 1 hour; Toluene is then distilled off under reduced pressure, purified with ethanol, filtered, and dried under vacuum. The resulting product is the oil-based drilling fluid antifreeze.

[0063] The antifreeze performance of the oil-based drilling fluid antifreeze agents synthesized in the examples and comparative examples was evaluated in field mud, and their impact on the basic properties of oil-based mud was assessed. Field mud (old mud) samples were taken from the Yangzhou Huaye block. The No. 3 white oil was supplied by Sinopec Jingmen Petrochemical Plant. Details are as follows: Base slurry: 400mL of on-site mud + 40mL of No. 3 white oil; Experimental mud: base mud + 1% oil-based drilling fluid antifreeze (1% - the mass of the antifreeze is a percentage of the volume of the mud on site). After stirring evenly, age at 120℃ for 16 hours, cool, and then stir at 11000r / min for 20 minutes. The apparent viscosity, plastic viscosity, dynamic shear force, static shear force, demulsification voltage, and high-temperature and high-pressure water loss of the base slurry and the test slurry are determined according to the standard GB / T 16783.2 "Field Testing of Drilling Fluids for Petroleum and Natural Gas Industry - Part 2: Oil-based Drilling Fluids".

[0064] Antifreeze test: After aging, a portion of the drilling fluid (basic slurry or experimental slurry) was tested for its freezing point using a freezing point tester. The test results are shown in Table 1.

[0065] Table 1. Results of the Influence of Antifreeze on the Performance of Oil-Based Drilling Fluids

[0066] As can be seen from the data in Table 1, the addition of 1% antifreeze has little effect on the performance of oil-based drilling fluid, but its freezing point is reduced from the original 15℃ to -15℃, -16℃ and -18℃ respectively, showing a good antifreeze effect.

[0067] As can be seen from the comparative data in Table 1, neither the impact on drilling fluid performance nor the antifreeze effect is as good as the examples. Comparative Example 1 used methyl methacrylate, resulting in the addition of antifreeze to the field mud. Although it had a certain antifreeze effect, it only lowered the freezing point to -1℃, which is less effective than the -15℃ effect of Example 1, demonstrating the specific influence of methyl methacrylate on the antifreeze effect. Comparative Example 2 did not add diene for branching, resulting in a linear product. Although it lowered the mud freezing point to -5℃, it thickened the mud and affected drilling fluid performance, thus illustrating the importance of adding diene. Comparative Example 3 did not add chain transfer agent, resulting in an inability to control the polymer molecular weight. Although it lowered the freezing point to -7℃, it thickened the mud, demonstrating the important role of chain transfer agent. Comparative Example 4 did not add styrene monomer, and Comparative Example 5 did not add vinylpyrrolidone monomer. Although these two comparative examples had no significant impact on the drilling fluid system performance, they only lowered the freezing point to -8℃ and -7℃, respectively, which is far less effective than the examples. In Comparative Example 6, the solvent, initiator, and corresponding monomers were all added at once during the reaction, instead of being added gradually. This not only significantly reduced the demulsification voltage of the drilling fluid, but also, after adding the antifreeze from Comparative Example 6, the freezing point was only lowered to 11°C, which was a negligible effect. This demonstrates the importance of a gradual reaction for the desired effect.

[0068] The oil-based drilling fluid antifreeze prepared by this invention not only has little impact on the performance of drilling fluid, but also has a good antifreeze effect, which can reduce the freezing point of oil-based mud on site by more than 30°C.

[0069] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, not all embodiments. People can obtain other embodiments based on the present invention without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. An oil-based drilling fluid antifreeze, characterized in that, The raw materials include the following parts by weight: 60-80 parts of methacrylate, 4-10 parts of diene, 0.5-1.5 parts of initiator, 0.2-0.6 parts of chain transfer agent, 10-30 parts of styrene, 5-15 parts of vinylpyrrolidone and 0.5-1.5 parts of polymerization inhibitor; The methacrylates include one or more of tetradecyl methacrylate, cyclohexyl methacrylate, and lauryl methacrylate.

2. The oil-based drilling fluid antifreeze agent according to claim 1, characterized in that, The diene includes 1,5-hexadiene and / or 1,3-pentadiene.

3. The oil-based drilling fluid antifreeze agent according to claim 1, characterized in that, The initiator includes one or more of benzoyl peroxide, azobisisoheptanenitrile, azobisisovalerate, and azobiscyclohexylformonitrile.

4. The oil-based drilling fluid antifreeze agent according to claim 1, characterized in that, The chain transfer agent includes α-methylstyrene dimer.

5. The oil-based drilling fluid antifreeze agent according to claim 1, characterized in that, The polymerization inhibitor includes one or more of hydroquinone, tert-butylcatechol, hydrophenol monobutyl ether, and diethylhydroxylamine.

6. The oil-based drilling fluid antifreeze agent according to any one of claims 1 to 5, characterized in that, The oil-based drilling fluid antifreeze comprises the following raw materials in parts by weight: 60 parts methacrylate, 4 parts diene, 0.5 parts initiator, 0.2 parts chain transfer agent, 30 parts styrene, 15 parts vinylpyrrolidone, and 1 part polymerization inhibitor. Alternatively, it may include: 80 parts methacrylate, 10 parts diene, 1.5 parts initiator, 0.4 parts chain transfer agent, 20 parts styrene, 10 parts vinylpyrrolidone, and 1 part polymerization inhibitor; Alternatively, it may include: 70 parts methacrylate, 7 parts diene, 1.0 part initiator, 0.6 parts chain transfer agent, 30 parts styrene, 15 parts vinylpyrrolidone, and 1 part polymerization inhibitor.

7. The method for preparing the oil-based drilling fluid antifreeze according to any one of claims 1 to 6, characterized in that, Includes the following steps: Methacrylate, diene, initiator and organic solvent are mixed and subjected to a first reaction to obtain a first reaction solution; The first reaction solution and the chain transfer agent are mixed to carry out a second reaction to obtain a second reaction solution; The second reaction solution, styrene, and vinylpyrrolidone are mixed to carry out a third reaction to obtain a third reaction solution; The third reaction solution and the polymerization inhibitor are mixed to carry out a fourth reaction. The organic solvent is removed from the obtained fourth reaction solution to obtain an oil-based drilling fluid antifreeze.

8. The preparation method according to claim 7, characterized in that, The temperatures of the first, second, third, and fourth reactions are independently 80-90°C.

9. The preparation method according to claim 8, characterized in that, The first reaction takes 0.5 to 1 hour; the second reaction takes 1 to 3 hours; the third reaction takes 2 to 4 hours; and the fourth reaction takes 1 to 2 hours.

10. The application of the oil-based drilling fluid antifreeze agent according to any one of claims 1 to 6 or the oil-based drilling fluid antifreeze agent obtained by the preparation method according to any one of claims 7 to 9 in oil-based mud.

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