Oil well pipe thread coating, preparation method thereof and oil well pipe thread surface treatment process

Abstract

The invention discloses an oil well pipe thread coating, a preparation method thereof and an oil well pipe thread surface treatment process. The oil well pipe thread coating comprises a component A and a component B, wherein the mass ratio of the component A to the component B is 1: 5; the component A comprises epoxy resin, an organic solvent, a filler, a flatting agent, a defoaming agent and a solid lubricant; the component B comprises a curing agent, an accelerant and an organic solvent. The oil well pipe thread surface treatment process adopting the oil well pipe thread coating comprises the steps of pretreatment, high-temperature cleaning, sand blasting cleaning, coating spraying and coating curing. A thread surface phosphating process is replaced with a paint coating, the problem of environment pollution of the phosphating process is avoided, the economical efficiency and stability of thread surface treatment are improved, and the thread gluing phenomenon in oil well pipe operation is effectively prevented.

Description

Technical Field

[0001] This invention relates to the field of organic coatings, and in particular to a coating for oil well pipe threads, its preparation method, and a surface treatment process for oil well pipe threads. Background Technology

[0002] Currently, the main surface treatment processes for oil well pipe threads include copper plating and phosphating, to achieve wear resistance and thread anti-sticking properties. Cyanide copper plating, due to its complex process, high cost, and the difficulty in treating the waste liquid (containing cyanide), which easily causes environmental pollution, has been gradually replaced by phosphating. However, in recent years, with increasing environmental awareness, the phosphating process for drilling tool joint threads has also been required to be gradually phased out.

[0003] Given that phosphating is still the primary method for thread treatment, it is of great significance to develop a thread surface treatment process that has anti-corrosion, anti-gluing, and environmentally friendly properties. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides an oil well pipe thread coating, its preparation method, and an oil well pipe thread surface treatment process. This invention replaces the phosphating process on the thread surface with a coating, avoiding the environmental pollution problems associated with phosphating, improving the economy and stability of thread surface treatment, and effectively preventing sticking during oil well pipe operations.

[0005] In a first aspect, the present invention provides an oil well pipe thread coating, which is achieved through the following technical solution.

[0006] A coating for oil well pipe threads, comprising component A and component B, wherein the mass ratio of component A to component B is 1:5;

[0007] Component A comprises the following raw materials by weight percentage: epoxy resin 18-35%, organic solvent 11-42%, filler 20-33%, leveling agent 0.5-1%, defoamer 0.5-1%, and solid lubricant 0.5-5%.

[0008] Component B comprises the following raw materials by weight percentage: 30-50% curing agent, 15-42% accelerator, and 10-28% organic solvent.

[0009] Furthermore, in component A, the epoxy resin is bisphenol A epoxy resin E42; the organic solvent is xylene and n-butanol, with a mass ratio of xylene to n-butanol of (6-25):(5-17); the filler is talc and barium sulfate, with a mass ratio of talc to barium sulfate of (10-18):(10-15); the leveling agent is polyether modified silicone oil (Hubei Jusheng Technology Co., Ltd., H-204); the defoamer is trifluoropropylmethylcyclotrisiloxane defoamer (Zhejiang Huanxin Fluorine Materials Co., Ltd.); and the solid lubricant is modified graphene.

[0010] Furthermore, the modification method of the modified graphene is as follows: graphene and 1,3-diazole are added to distilled water at a mass ratio of 1:(0.5-2), and ultrasonically treated at 300-500W for 30-60 minutes. Then, alumina nanoparticles are added, with a mass ratio of graphene to alumina nanoparticles of 1:(0.5-2). The resulting reaction solution is heated in a water bath at 60-80℃ for 4-8 hours. After filtration, washing, and drying, alumina-modified graphene is obtained.

[0011] Furthermore, in component B, the curing agent is a polyamide curing agent, which is composed of 60wt%-80wt% of polyamide 200 curing agent (polyamide 650, Wuxi Xinye) and 20wt%-40wt% of polyamide 300 curing agent (Shandong Pinshang PS-300); the accelerator is isophorone diisocyanate and hexamethylene diisocyanate, with a mass ratio of (5-18):(10-24); and the organic solvent is methyl ethyl ketone (MEK).

[0012] Secondly, the present invention provides a method for preparing a coating for oil well pipe threads, which is achieved through the following technical solution.

[0013] A method for preparing the above-mentioned oil well pipe thread coating includes the following steps:

[0014] Preparation of component A:

[0015] a. Crush the talc powder and barium sulfate, and sieve them through a 120-mesh sieve for later use;

[0016] b. Mix and stir the epoxy resin and modified graphene at a temperature of 50-60℃, a stirring speed of 500 r / min, and a stirring time of 35-45 min to obtain solution A1;

[0017] c. Add talc and barium sulfate to solution A1 and stir. The stirring temperature is 60-70℃, the stirring speed is 800r / min, and the stirring time is 15-20min to obtain solution A2.

[0018] d. After solution A2 cools to 25-30℃, add n-butanol, xylene, polyether-modified silicone oil, and trifluoropropylmethylcyclotrisiloxane defoamer and stir at a speed of 500 r / min for 30-40 min to obtain component A.

[0019] Preparation of component B:

[0020] Add an organic solvent to the polyamide, mix and disperse it, then add isophorone diisocyanate and hexamethylene diisocyanate, stir for 20-30 minutes to obtain component B.

[0021] Thirdly, the present invention provides a surface treatment process for oil well pipe threads, which is achieved through the following technical solutions.

[0022] A surface treatment process for oil well pipe threads includes the following steps:

[0023] S1. Pretreatment: Use a cleaning agent to clean the thread grease and other oil stains on the well tubing, and wipe it clean;

[0024] S2. High-temperature cleaning: The oil well casing is baked at 381℃-399℃;

[0025] S3. Sandblasting cleaning: The internal or external threads of the oil well pipe are sandblasted using a sandblasting device. The sandblasting is carried out at room temperature and relative humidity of less than 90%, and the surface temperature of the thread is not lower than the dew point temperature +3℃. The sandblasting material is grade 1 brown corundum with a particle size of 100 mesh or higher.

[0026] S4. Coating Spraying: Before spraying, heat the above coating to 18°C, mix component A and component B in proportion, and adjust the viscosity to 10-15 seconds (Chai No. 3 cup, 20-22°C) with additives; within 30 minutes after sandblasting, under the condition that the air humidity is less than or equal to 90%, use a spraying device to spray the internal or external threads of the oil well pipe, and the wet film thickness of the coating is 25-50um;

[0027] S5. Coating curing.

[0028] Furthermore, in step S1, the cleaning agent used is No. 0 diesel oil.

[0029] Furthermore, in step S2, the temperature is raised from room temperature to the set temperature over 4 hours, and then kept at that temperature for 4 hours. After high-temperature cleaning, the special cleaning agent for oil well pipes evaporates.

[0030] Furthermore, in step S3, the blasting device includes a rotating roller and a blasting gun. The oil well pipe is fitted onto the rotating roller, and the front end of the blasting gun is equipped with a blasting head, which is at a 45° angle to the oil well pipe. When blasting the external threads of the oil well pipe, a blasting cover is also provided at the threaded end of the oil well pipe and outside the blasting gun to prevent abrasive from splashing everywhere during the blasting process.

[0031] Furthermore, in step S4, the additive is selected from one or more of butanone, ethanol, and butanol.

[0032] Furthermore, in step S4, the spraying device includes a paint spray gun, with a spraying motor at the front end of the spray gun. The spraying motor enables finer paint atomization, improves transfer efficiency, and enhances the appearance and stability of the coating. When spraying the external threads of the oil well pipe, a spray cover is provided at the threaded end of the oil well pipe and outside the paint spray gun to prevent paint from splashing everywhere during the spraying process.

[0033] Furthermore, in step S4, after the spraying is completed, the pipeline is cleaned with methyl ethyl ketone (MEK) to prevent the coating inside the pipeline from curing.

[0034] Furthermore, in step S5, the oil well pipe after being coated with paint is placed for 10-20 minutes, and then baked at 150℃-170℃ for 50-70 minutes; the temperature error inside the continuous furnace baking chamber should be controlled within ±10℃.

[0035] This application has the following beneficial effects.

[0036] This invention developed a coating formulation suitable for threaded wire coatings and completed research on the production process of threaded wire coatings, including thread surface sandblasting, spraying, and curing processes. The sandblasting process parameters, spraying parameters, and curing temperature were determined. This invention also designed threaded wire sandblasting and spraying equipment, including equipment for internal thread sandblasting and spraying, and equipment for external thread sandblasting and spraying. Tests showed that the threaded wire coating produced using this invention achieved an adhesion grade of A, a friction coefficient of 0.16, and remained intact after 10 cycles of uncoupling and re-coupling, meeting the required conditions. Attached Figure Description

[0037] Figure 1 This is a flow chart of the oil well pipe thread surface treatment process of the present invention;

[0038] Figure 2 This is a schematic diagram of sandblasting the external thread of the oil well pipe according to the present invention;

[0039] Figure 3 This is a schematic diagram of the internal thread sandblasting of the oil well pipe according to the present invention;

[0040] Figure 4 This is a schematic diagram of the internal thread spraying of the oil well pipe according to the present invention;

[0041] Figure 5 This is a schematic diagram of the external thread spraying of the oil well pipe according to the present invention.

[0042] Among them, 1. oil well pipe; 2. external thread; 3. abrasive; 4. blasting head; 5. spray gun; 6. blasting cover; 7. internal thread; 8. paint spray gun; 9. spraying motor; 10. paint; 11. spraying cover. Detailed Implementation

[0043] The invention will be further described below with reference to the accompanying drawings and embodiments. Unless otherwise specified, the experimental methods used in this invention are conventional methods, and the experimental equipment, materials, reagents, etc. used can all be purchased from relevant material sales companies.

[0044] Preparation Example

[0045] The modification methods for modified graphene are as follows:

[0046] Graphene and 1,3-diazole were added to distilled water at a mass ratio of 1:1 and ultrasonically treated at 400W for 40 minutes. Then, alumina nanoparticles were added, with a mass ratio of graphene to alumina nanoparticles of 1:1. The resulting reaction solution was heated in a water bath at 70°C for 6 hours. After filtration, washing, and drying, alumina-modified graphene was obtained.

[0047] Example

[0048] A coating for oil well pipe threads, comprising component A and component B;

[0049] Component A includes 30 kg of epoxy resin (bisphenol A epoxy resin E42), 20 kg of xylene, 15 kg of n-butanol, 15 kg of talc, 15 kg of barium sulfate, 1 kg of polyether-modified silicone oil, 1 kg of trifluoropropylmethylcyclotrisiloxane defoamer, and 3 kg of modified graphene prepared in the preparation example.

[0050] Component B includes 45 kg of polyamide (60 wt% polyamide 200 curing agent and 40 wt% polyamide 300 curing agent), 15 kg of isophorone diisocyanate, 18 kg of hexamethylene diisocyanate, and 22 kg of methyl ethyl ketone (MEK).

[0051] The preparation method of the oil well pipe thread coating includes the following steps:

[0052] Preparation of component A:

[0053] (1) Weigh the talc powder and barium sulfate according to their weight, crush them, and sieve them with a 120-mesh vibrating screen for later use.

[0054] (2) Epoxy resin and modified graphene were added to the reaction vessel and stirred at a temperature of 55°C, a stirring speed of 500 r / min and a stirring time of 40 min to obtain solution A1.

[0055] (3) Add talc powder and barium sulfate to solution A1 and stir. The stirring temperature is 65℃, the stirring speed is 800r / min, and the stirring time is 20min to obtain solution A2.

[0056] (4) After solution A2 is cooled to 25°C, add n-butanol, xylene, polyether-modified silicone oil and trifluoropropylmethylcyclotrisiloxane defoamer and stir. The stirring speed is 500 r / min and the stirring time is 40 min to obtain component A.

[0057] Preparation of component B:

[0058] Add polyamide curing agent to the reaction vessel, add methyl ethyl ketone, mix evenly and disperse. Then add isophorone diisocyanate and hexamethylene diisocyanate to the reaction vessel, and stir for 20 minutes to obtain coating B.

[0059] like Figure 1 As shown, a surface treatment process for oil well pipe threads (using a pair of 5-inch drill pipe joints) includes the following steps:

[0060] 1. Pretreatment: Place the oil well pipe on the rotating roller and rotate it. Based on the principle of organic solvent compatibility, use a brush dipped in thread cleaning agent to clean thread grease and other oil stains, and wipe it clean.

[0061] 2. High-temperature cleaning: Place the oil well pipe in a hot cleaning furnace for baking. The baking temperature can be set to 390℃. The temperature will rise from room temperature to the set temperature in 4 hours and be kept at that temperature for 4 hours. After high-temperature cleaning, the special cleaning agent for oil well pipes will evaporate.

[0062] 3. Sandblasting Cleaning: Thread sandblasting utilizes a gun-type mechanical sandblasting system. The oil well tubing is placed on a rotating roller, and during sandblasting, the tubing is rotated. The sandblasting head (4) is positioned at a 45° angle to the tubing to facilitate rust removal at the thread root. Sandblasting is performed at room temperature and relative humidity below 90%, ensuring the thread surface temperature is not lower than the dew point temperature +3°C. To ensure tight thread clearance and cleanliness, brown corundum is used as the abrasive, with a grit size of 100 mesh or higher. The rust removal grade should meet Sa3 requirements, and the thread surface should be free of defects such as dents.

[0063] like Figure 2 As shown, Figure 2 This is a schematic diagram of sandblasting on the external thread of an oil well pipe. The oil well pipe 1 is fitted on a rotating roller. A sandblasting head 4 is set at the front end of the spray gun 5. The sandblasting head 4 is at a 45° angle to the oil well pipe 1. The abrasive 3 is sprayed onto the external thread 2 at the front end of the oil well pipe 1 through the sandblasting head 4. A sandblasting cover 6 is provided at the thread end of the oil well pipe 1 and outside the spray gun 5.

[0064] like Figure 3 As shown, Figure 3 This is a schematic diagram of sandblasting the internal thread of an oil well pipe. The oil well pipe 1 is fitted on a rotating roller. The front end of the spray gun 5 is equipped with a sandblasting head 4. The sandblasting head 4 enters the internal thread 7 of the oil well pipe 1. The sandblasting head 4 is at a 45° angle to the oil well pipe 1. The abrasive 3 is sprayed onto the internal thread 7 at the front end of the oil well pipe 1 through the sandblasting head 4.

[0065] 4. Coating Spraying: To prevent oxidation of the threaded surface before coating, spraying should be carried out within 30 minutes after sandblasting. Operation should be stopped when the air humidity exceeds 90%. Before spraying, heat the coating to 18℃, mix component A and component B in a 1:5 ratio, adjust the viscosity to 12 seconds with methyl ethyl ketone (MEK), and ensure the coating is thoroughly mixed. The wet film thickness of the sprayed coating should be 40µm. After spraying, clean the pipeline with MEK to prevent the coating from curing inside the pipeline.

[0066] like Figure 4 As shown, Figure 4 This is a schematic diagram of spraying the internal thread of an oil well pipe. The front end of the paint spray gun 8 is equipped with a spraying motor 9. The front part of the paint spray gun 8 is inserted into the internal thread 7 of the oil well pipe 1, and the paint 10 is sprayed onto the internal thread 7 of the oil well pipe 1 under the action of the spraying motor 9.

[0067] like Figure 5 As shown, Figure 5 This is a schematic diagram of spraying paint onto the external thread of an oil well pipe. The front end of the paint spray gun 8 is equipped with a spraying motor 9, and the paint 10 is sprayed onto the external thread 2 of the oil well pipe 1 under the action of the spraying motor 9. A spraying cover 11 is provided at the thread end of the oil well pipe 1 and outside the paint spray gun 8.

[0068] 5. Coating Curing: After the coating has been sprayed onto the oil well pipe, let it sit for 15 minutes, then place it in a continuous furnace for baking. Set the temperature to 165℃ and the time to 60 minutes. The temperature error inside the furnace should be controlled within ±10℃.

[0069] The finished coating is continuous and uniform, with a dry film thickness of 26μm. According to the standard SY / T5711 phosphate treatment technical conditions for drill thread, the surface was found to be free of rust. The coating has a pull-out adhesion of 11MPa, a friction coefficient of 0.16, and a wear resistance of 40mg / 1000 rpm. The coating did not fall off after 9 cycles of undocking and unhooking.

[0070] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An oil country tubular goods threaded coating characterized by: The A component and the B component, the mass ratio of the A component and the B component is 1:5; The A component comprises the following raw materials in weight percentage: epoxy resin 18-35%, organic solvent 11-42%, filler 20-33%, leveling agent 0.5-1%, defoaming agent 0.5-1%, solid lubricant 0.5-5%; The B component comprises the following raw materials in weight percentage: curing agent 30-50%, accelerator 15-42%, organic solvent 10-28%.

2. An oil country tubular thread coating according to claim 1, characterized in that: In the A component, the epoxy resin is bisphenol A epoxy resin E42; the organic solvent is selected from dimethylbenzene and n-butanol, the mass ratio of dimethylbenzene and n-butanol is (6-25):(5-17); the filler is selected from talcum powder and barium sulfate, the mass ratio of talcum powder and barium sulfate is (10-18):(10-15); the leveling agent is selected from polyether modified silicone oil; the defoaming agent is selected from trifluoropropylmethylcyclotrisiloxane defoaming agent; the solid lubricant is selected from modified graphene.

3. An oil country tubular good threaded coating according to claim 2, characterized in that: The modification method of the modified graphene is as follows: graphene and 1,3-oxadiazole are added to distilled water in a mass ratio of 1:(0.5-2), ultrasonic treatment is carried out at 300-500W for 30-60 minutes, then alumina nanoparticles are added, the mass ratio of graphene and alumina nanoparticles is 1:(0.5-2), the obtained reaction solution is heated in a water bath at 60-80℃ for 4-8 hours, and then filtration, washing and drying are carried out to obtain alumina modified graphene.

4. An oil country tubular good threaded coating according to claim 1, characterized by: In the B component, the curing agent is selected from polyamide curing agent, the polyamide curing agent is composed of 60wt%-80wt% of polyamide 200 curing agent and 20wt%-40wt% of polyamide 300 curing agent; the accelerator is selected from isophorone diisocyanate and hexamethylene diisocyanate, the mass ratio of isophorone diisocyanate and hexamethylene diisocyanate is (5-18):(10-24); the organic solvent is selected from butanone.

5. A process for the preparation of the oil well pipe thread coating as claimed in any one of claims 1 to 4, characterized by: The method comprises the following steps: Preparation of the A component: a. The talcum powder and barium sulfate powder are crushed and sieved with a 120 mesh sieve for use; b. The epoxy resin and the modified graphene are mixed and stirred, the stirring temperature is 50-60℃, the stirring speed is 500r / min, and the stirring time is 35-45min to obtain solution A1; c. The talcum powder and barium sulfate are added to the solution A1 and stirred, the stirring temperature is 60-70℃, the stirring speed is 800r / min, and the stirring time is 15-20min to obtain solution A2; d. After the solution A2 is cooled to 25-30℃, the n-butanol, dimethylbenzene, polyether modified silicone oil, trifluoropropylmethylcyclotrisiloxane defoaming agent are added and stirred, the stirring speed is 500r / min, and the stirring time is 30-40min to obtain the A component; Preparation of the B component: The polyamide is mixed uniformly and dispersed by adding the organic solvent, then the isophorone diisocyanate and hexamethylene diisocyanate are added and stirred for 20-30 minutes to obtain the B component.

6. An oil country tubular goods thread surface treatment process characterized by: The method comprises the following steps: S1. Pretreatment: using a cleaning agent to clean the thread grease and other parts of the oil well pipe, and wiping clean; S2. High temperature cleaning: baking the oil well pipe at 381℃-399℃; S3. Sand blasting cleaning: the inner thread or outer thread of the oil well pipe is subjected to sand blasting treatment by using a sand blasting device, the sand blasting treatment is carried out under the condition that the room temperature is and the relative humidity of air is less than 90%, the temperature of the thread surface is not less than the dew point temperature + 3℃; the sand blasting material is first grade brown corundum, and the particle size is more than 100 mesh; S4. Coating spraying: the coating of any one of claims 1-4 is heated to 18℃ before spraying, the A component and the B component are proportioned according to the proportion, and the viscosity is adjusted to 10-15 seconds by using an additive; within 30 minutes after the sand blasting treatment, the air humidity is less than or equal to 90%, the inner thread or outer thread of the oil well pipe is subjected to spraying by using a spraying device, and the wet film thickness of the coating spraying is 25-50um; S5. Coating curing.

7. A process for surface treatment of threaded connections of oil well pipes according to claim 6, characterized in that: In step S2, the temperature is raised from room temperature to the set temperature for 4 hours, and the temperature is kept for 4 hours.

8. A process for surface treatment of threaded connections of oil well pipes as claimed in claim 6 wherein: In step S3, the sand blasting device includes a rotating roller and a spray gun, the oil well pipe is sleeved on the rotating roller, the front end of the spray gun is provided with a sand blasting head, and the sand blasting head is at an angle of 45° with the oil well pipe.

9. A process for surface treatment of threaded connections of oil well pipes as claimed in claim 6 wherein: In step S4, the spraying device includes a coating spray gun, and the front end of the coating spray gun is provided with a spraying motor.

10. A process for surface treatment of threaded connections of oil well pipes as claimed in claim 6 wherein: In step S5, the oil well pipe after spraying the coating is placed for 10-20 minutes, and then baked at 150℃-170℃ for 50-70 minutes.

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