Anti-wax and anti-corrosion internal coating and anti-wax precipitation method

Abstract

The invention discloses an anti-wax and anti-corrosion internal coating and an anti-wax precipitation method, and belongs to the technical field of coatings. The inner coating provided by the invention comprises a first paraffin-proof and corrosion-proof layer coated on the inner surface of the steel pipe and a second paraffin-proof and corrosion-proof layer coated on the surface of the first paraffin-proof and corrosion-proof layer; the first anti-wax and anti-corrosion layer comprises 8-25 parts of epoxy resin, 10-36 parts of phenolic resin, 6-18 parts of methanol, 10-35 parts of ethanol and 1-15 parts of an adhesion enhancer; and the second paraffin and corrosion prevention layer comprises 10-30 parts of epoxy resin, 9-25 parts of phenolic resin, 20-50 parts of zirconium oxide powder, 1-16 parts of a wear-corrosion-resistant reinforcing agent, 0.5-10 parts of a surface wettability conversion agent and 0.5-6 parts of a surface leveling agent. The anti-wax and anti-corrosion inner coating provided by the invention has good anti-wax and anti-corrosion performance and also has relatively good economical efficiency, and the anti-wax and anti-corrosion inner coating is excellent in anti-wax and anti-corrosion effect and long in service life through related oil field field tests and has very good application and popularization values.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, and specifically relates to an anti-wax and anti-corrosion inner coating and a method for preventing wax buildup. Background Technology

[0002] With the rapid development of oil and gas exploration and development in various countries, oil and gas fields containing high levels of corrosive media such as H2S, CO2, chloride ions, and hydrates have emerged, making problems such as safety, corrosion, waxing, and scaling in oil pipeline working environments increasingly prominent. Most crude oils have a relatively high wax content; in some regions of China, the wax content of crude oil is as high as... Figure 1 As shown, the high wax content of crude oil reduces the permeability of the oil reservoir. During oil and gas extraction, wax separates and precipitates from the oil. Continuous wax deposition leads to blockage of the producing layer, reduced well production, and even production shutdowns, causing significant disruptions. During water injection and crude oil transportation in oilfields, changes in environmental conditions such as pressure and temperature, as well as the adsorption between the fluid medium and the pipe surface, cause wax and inorganic salts in the transported medium to deposit on the pipe wall, forming a wax and scale layer. This reduces the pipeline's flow area and increases transport resistance. In principle, the surface energy of the material is a crucial factor in triggering wax and scale formation.

[0003] Organic coatings are now widely used on the inner walls of pipes. Due to their low polarity and low surface roughness, organic coatings also exhibit significant anti-wax and anti-scaling properties. For example, patent CN110294982A discloses an anti-corrosion, anti-wax, and anti-scaling coating and its preparation method. This coating includes an inner layer and an outer layer. The inner layer raw materials include: polytetrafluoroethylene resin, a first filler, boron phenolic resin, methyl methacrylate, a first solvent, and a first curing agent (cashew shell oil modified phenolic amine). The outer layer raw material components, by weight, include: metronidazole modified graphene oxide composite material, polyimide resin, α-amino-α-iminophosphonic acid inner salt, hydrophobically modified magnetic particles, a second curing agent (a mixture of diaminodiphenyl ether, cashew shell oil modified phenolic amine, and organic phosphite), a second filler, and a second solvent. The filler is selected from nano-silica, nano-titanium dioxide, and polytetrafluoroethylene micro powder. The thickness ratio of the inner layer to the outer layer is 1:(3.2-3.6). The coating provided by this invention has a high scale prevention rate, good corrosion resistance and wax prevention effect, and can be widely used to protect oil casing, drill pipe and tubing in oilfield extraction. However, the composition of the inner and outer coatings of the above-mentioned coatings is quite different, and some of the raw materials need to be modified in advance before use, making the preparation process cumbersome. Summary of the Invention

[0004] To address the above problems, this invention selects a low surface energy material and reduces the surface energy of the material through surface modification to achieve the purpose of preventing wax deposition and scaling. The specific technical solution is as follows:

[0005] One of the objectives of this invention is to provide an anti-wax and anti-corrosion inner coating, which includes a first anti-wax and anti-corrosion layer applied to the inner surface of a steel pipe and a second anti-wax and anti-corrosion layer applied to the surface of the first anti-wax and anti-corrosion layer.

[0006] The first anti-wax and anti-corrosion layer comprises the following components in parts by weight: 8-25 parts epoxy resin, 10-36 parts phenolic resin, 6-18 parts methanol, 10-35 parts ethanol and 1-15 parts adhesion enhancer;

[0007] The second anti-wax and anti-corrosion layer comprises the following components by weight: 10-30 parts epoxy resin, 9-25 parts phenolic resin, 20-50 parts zirconium oxide powder, 1-16 parts abrasion and corrosion reinforcing agent, 0.5-10 parts surface wettability conversion agent, and 0.5-6 parts surface smoothing agent.

[0008] Furthermore, the adhesion enhancer is one or more of titanium dioxide, cobalt trioxide, and chromium trioxide.

[0009] Furthermore, the wear-resistant reinforcing agent is one or more of silicon dioxide, molybdenum disulfide, silicon carbide, and carbon fiber.

[0010] Furthermore, the surface wettability conversion agent is one or more of polytetrafluoroethylene, polyvinyl alcohol, and molybdenum disulfide.

[0011] Furthermore, the surface smoothing agent is one or more of titanium dioxide, tantalum pentoxide, and octyl acrylate copolymer.

[0012] The second objective of this invention is to propose a method for preventing wax buildup, which involves applying the aforementioned anti-wax and anti-corrosion inner coating to the inner surface of the pipe, specifically including the following steps:

[0013] Receive the pipes used for coating and inspect the pipes, including inspecting the appearance, specifications, quantity, and whether there are sharp edges and burrs on the inner surface of the pipes;

[0014] Prepare the first and second anti-wax and anti-corrosion layers respectively;

[0015] The pipe is placed in a gas-fired heating furnace to remove oil and impurities from the inner wall of the pipe, resulting in a clean pipe.

[0016] The inner surface of the clean pipe was sandblasted using brown fused alumina, and the defects of the pipe and the wall thickness of the pipe after sandblasting were measured to confirm the surface cleanliness, roughness, temperature and relative humidity of the steel pipe surface, and the dwell time before coating after shot blasting.

[0017] The first anti-wax and anti-corrosion layer is sprayed onto the inner wall of the pipe at room temperature and pre-cured. Then, the second anti-wax and anti-corrosion layer is sprayed onto the first anti-wax and anti-corrosion layer for a second curing.

[0018] After complete curing, the coating appearance, thickness, and leaks are inspected, and qualified products are selected.

[0019] Furthermore, the thickness of the first anti-wax and anti-corrosion layer is 25–50 μm.

[0020] Furthermore, the thickness of the second anti-wax and anti-corrosion layer is 100-150 μm.

[0021] Furthermore, the surface roughness of the first anti-wax and anti-corrosion layer is 0.10 to 0.20 μm.

[0022] The third objective of this invention is to propose the application of the aforementioned anti-wax and anti-corrosion inner coating or the aforementioned anti-wax deposition method in the wellbore tubing of a production well.

[0023] The beneficial effects of this invention are:

[0024] The anti-corrosion coating proposed in this invention has a very low surface free energy and extremely strong dual repellency (oleophobic and hydrophobic), preventing the formation of stable water and oil films on the inner wall of the pipe and making it less prone to wax buildup. Furthermore, the polymer coating containing titanium and tantalum in this invention possesses unique properties such as excellent resistance to acid and alkali corrosion, high adhesion, and wear resistance, effectively protecting the normal operation of oil / casing in oil and gas wells and saving oil and gas fields significant unnecessary costs. The epoxy phenolic coating forms Fe-O bonds between the epoxy groups in the epoxy resin and the iron in the iron pipe, allowing the coating to adhere tightly to the surface of the inner wall of the oil / casing. The polymers in the coating are cured at high temperatures, forming a dense network structure. The coating surface is smooth and glossy, hard, with a low coefficient of friction and low surface energy, exhibiting anti-fouling properties and extremely strong dual repellency (oleophobic and hydrophobic), making it difficult for various scales and waxes to adhere to the coating film. In addition, the coating also has resistance to CO2, a small amount of H2S, and Cl. - Corrosion by hydrochloric acid, oxalic acid, and sodium hydroxide.

[0025] This invention proposes an anti-wax and anti-corrosion inner coating that not only has good anti-wax and anti-corrosion performance but also good economic efficiency. The coating has excellent mechanical properties, good electrical insulation and chemical stability, a smooth and glossy surface, and is hard with a low surface friction coefficient. Field tests in relevant oil fields have shown that it has excellent anti-wax and anti-corrosion effects, a long service life, and has great application and promotion value.

[0026] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This chart shows statistical data on the wax content of crude oil from most oil fields in China.

[0029] Figure 2 A schematic diagram of the structure of the anti-wax and anti-corrosion inner coating proposed in an embodiment of the present invention is shown;

[0030] Figure 3 A flowchart of an anti-waxing method proposed in an embodiment of the present invention is shown;

[0031] Figure 4 This shows the relationship between contact angle and interfacial energy;

[0032] Figure 5 The wetting condition is represented by the contact angle. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] This invention proposes an anti-wax and anti-corrosion inner coating and a method for preventing wax buildup. The structure of the inner coating is as follows: Figure 2 As shown, it includes a first anti-wax and anti-corrosion layer applied to the inner surface of the steel pipe and a second anti-wax and anti-corrosion layer applied to the surface of the first anti-wax and anti-corrosion layer.

[0035] The thickness of the first anti-wax and anti-corrosion layer is 25-50 μm; the thickness of the second anti-wax and anti-corrosion layer is 100-150 μm; and the surface roughness of the first anti-wax and anti-corrosion layer is 0.10-0.20 μm.

[0036] The first anti-wax and anti-corrosion layer comprises the following components by weight: 8-25 parts epoxy resin, 10-36 parts phenolic resin, 6-18 parts methanol, 10-35 parts ethanol and 1-15 parts adhesion enhancer; in this invention, methanol and ethanol are used as dispersants to promote the rapid drying of the coating and improve its fluidity, while also improving the surface tension wetting properties of the coating.

[0037] The second paraffin and corrosion prevention layer comprises the following components in parts by mass: 10-30 parts of epoxy resin, 9-25 parts of phenolic resin, 20-50 parts of zirconium oxide powder, 1-16 parts of wear and corrosion resistance enhancer, 0.5-10 parts of surface wettability conversion agent, and 0.5-6 parts of surface leveling agent.

[0038] In some embodiments of the present invention, the adhesion enhancer is one or more of titanium dioxide, cobalt sesquioxide, and chromium sesquioxide, and the bonding strength between the first paraffin and corrosion prevention layer and the steel pipe is enhanced by providing the adhesion enhancer.

[0039] The wear and corrosion resistance enhancer is one or more of silicon dioxide, molybdenum disulfide, silicon carbide, and carbon fiber, and the wear resistance and corrosion resistance of the steel pipe are improved by adding the wear and corrosion resistance enhancer.

[0040] The surface leveling agent is one or more of titanium dioxide, tantalum pentoxide, and octyl acrylate copolymer, and the flatness of the second paraffin and corrosion prevention layer is improved by providing the surface leveling agent.

[0041] As Figure 3 shown, the paraffin anti - deposition method proposed by the present invention comprises the following steps: <000009​​​​​​​​​​​​​​​​​​The following specific embodiments illustrate the anti-corrosion inner coating and anti-waxing method proposed in this invention, as well as the performance of the anti-corrosion inner coating of this invention.

[0049] Example 1

[0050] The first and second anti-wax and anti-corrosion layers, as well as the method for preventing wax buildup, proposed in this embodiment are as follows:

[0051] Receive the pipes used for coating and inspect the pipes, including inspecting the appearance, specifications, quantity, and whether there are sharp edges and burrs on the inner surface of the pipes;

[0052] The first anti-wax and anti-corrosion layer was prepared by mixing 8 parts epoxy resin, 36 parts phenolic resin, 6 parts methanol, 35 parts ethanol and 15 parts titanium dioxide as adhesion enhancer. The second anti-wax and anti-corrosion layer was prepared by mixing 10 parts epoxy resin, 25 parts phenolic resin, 50 parts zirconium oxide powder, 1 part silica as wear-resistant enhancer, 10 parts polytetrafluoroethylene as surface wettability conversion agent and 4 parts titanium dioxide as surface smoothing agent.

[0053] The pipe is placed in a gas-fired heating furnace to remove oil and impurities from the inner wall of the pipe, resulting in a clean pipe. In this embodiment, the furnace temperature of the gas-fired heating furnace is controlled at 320-400°C, thereby completely carbonizing the oil and impurities on the inner wall of the pipe.

[0054] The inner surface of the cleaned pipe is sandblasted using brown fused alumina. During the sandblasting process, the defects of the original pipe and the wall thickness of the sandblasted pipe need to be measured, and the surface cleanliness, roughness, surface temperature, relative humidity, and dwell time after shot blasting and before coating are confirmed. In this embodiment, brown fused alumina sandblasting is performed on the inner wall of the pipe according to the standard GB / T 2478. The treatment is considered qualified when the rust removal grade of the inner wall of the pipe reaches Sa2.5 or above, the anchor pattern depth is 25-76μm, and the requirements for internal anti-corrosion spraying are met.

[0055] The first anti-wax and anti-corrosion layer is sprayed onto the inner wall of the pipe at room temperature and pre-cured. Then, the second anti-wax and anti-corrosion layer is sprayed onto the first anti-wax and anti-corrosion layer for a second curing.

[0056] After complete curing, the appearance, thickness and leakage points of the coating are inspected. The coating is qualified if the coating thickness reaches the anti-wax and anti-corrosion thickness specified in the SY / T6717 standard, and the entire coated pipe is qualified if there are no leakage points.

[0057] In this embodiment, the thickness of the first anti-wax and anti-corrosion layer formed according to the above-described anti-wax method is 25 μm, the thickness of the second anti-wax and anti-corrosion layer is 100 μm, and the surface roughness of the first anti-wax and anti-corrosion layer is 0.10 μm.

[0058] Example 2

[0059] The same anti-wax treatment method as in Example 1 was used to treat the wellbore tubing of the oil and gas thermal recovery well to prevent wax deposition, with the following difference:

[0060] In this embodiment, the first anti-wax and anti-corrosion layer comprises the following components by weight:

[0061] 15 parts epoxy resin, 25 parts phenolic resin, 18 parts methanol, 30 parts ethanol and 12 parts cobalt trioxide adhesion enhancer;

[0062] The second anti-wax and anti-corrosion layer comprises the following components by weight:

[0063] 20 parts epoxy resin, 15 parts phenolic resin, 40 parts zirconium oxide powder, 15 parts abrasion-resistant reinforcing agent molybdenum disulfide, 8 parts surface wettability conversion agent polyvinyl alcohol, and 2 parts surface smoothing agent tantalum pentoxide.

[0064] In this embodiment, the thickness of the first anti-wax and anti-corrosion layer is 30 μm, the thickness of the second anti-wax and anti-corrosion layer is 120 μm, and the surface roughness of the first anti-wax and anti-corrosion layer is 0.15 μm.

[0065] Example 3

[0066] The same anti-wax treatment method as in Example 1 was used to treat the wellbore tubing of the oil and gas thermal recovery well to prevent wax deposition, with the following difference:

[0067] The first anti-wax and anti-corrosion layer in this embodiment comprises the following components by weight:

[0068] 25 parts epoxy resin, 20 parts phenolic resin, 15 parts methanol, 25 parts ethanol and 15 parts chromium trioxide adhesion enhancer;

[0069] The second anti-wax and anti-corrosion layer comprises the following components by weight:

[0070] 30 parts epoxy resin, 20 parts phenolic resin, 20 parts zirconium oxide powder, 16 parts abrasion-resistant reinforcing agent carbon fiber, 8 parts surface wettability conversion agent molybdenum disulfide, and 6 parts surface smoothing agent octyl acrylate copolymer.

[0071] In this embodiment, the thickness of the first anti-wax and anti-corrosion layer is 50 μm, the thickness of the second anti-wax and anti-corrosion layer is 150 μm, and the surface roughness of the first anti-wax and anti-corrosion layer is 0.20 μm.

[0072] Comparative Example 1

[0073] The same anti-wax treatment method as in Example 1 was used to treat the wellbore tubing of the oil and gas thermal recovery well to prevent wax deposition, with the following difference:

[0074] The first anti-wax and anti-corrosion layer in this embodiment comprises the following components by weight:

[0075] 23 parts epoxy resin, 36 parts phenolic resin, 6 parts methanol, 35 parts ethanol;

[0076] The second anti-wax and anti-corrosion layer comprises the following components by weight:

[0077] 10 parts epoxy resin, 25 parts phenolic resin, 50 parts zirconium oxide powder, 1 part abrasion-resistant reinforcing agent silica, 10 parts surface wettability conversion agent polytetrafluoroethylene, and 4 parts surface smoothing agent titanium dioxide.

[0078] In this embodiment, the thickness of the first anti-wax and anti-corrosion layer is 25 μm, the thickness of the second anti-wax and anti-corrosion layer is 100 μm, and the surface roughness of the first anti-wax and anti-corrosion layer is 0.10 μm.

[0079] Comparative Example 2

[0080] The same anti-wax treatment method as in Example 1 was used to treat the wellbore tubing of the oil and gas thermal recovery well to prevent wax deposition, with the following difference:

[0081] The first anti-wax and anti-corrosion layer in this embodiment comprises the following components by weight:

[0082] 8 parts epoxy resin, 36 parts phenolic resin, 6 parts methanol, 35 parts ethanol, and 15 parts titanium dioxide (adhesion enhancer);

[0083] The second anti-wax and anti-corrosion layer comprises the following components by weight:

[0084] 11 parts epoxy resin, 25 parts phenolic resin, 50 parts zirconium oxide powder, 10 parts polytetrafluoroethylene (PTFE) surface wettability conversion agent, and 4 parts titanium dioxide (TIG) surface smoothing agent.

[0085] In this embodiment, the thickness of the first anti-wax and anti-corrosion layer is 25 μm, the thickness of the second anti-wax and anti-corrosion layer is 100 μm, and the surface roughness of the first anti-wax and anti-corrosion layer is 0.10 μm.

[0086] Comparative Example 3

[0087] The same anti-wax treatment method as in Example 1 was used to treat the wellbore tubing of the oil and gas thermal recovery well to prevent wax deposition, with the following difference:

[0088] The first anti-wax and anti-corrosion layer in this embodiment comprises the following components by weight:

[0089] 15 parts epoxy resin, 25 parts phenolic resin, 18 parts methanol, 30 parts ethanol, and 12 parts cobalt trioxide (adhesion enhancer).

[0090] The second anti-wax and anti-corrosion layer comprises the following components by weight:

[0091] 28 parts epoxy resin, 15 parts phenolic resin, 40 parts zirconium oxide powder, 15 parts abrasion-resistant reinforcing agent molybdenum disulfide, and 2 parts surface smoothing agent tantalum pentoxide.

[0092] In this embodiment, the thickness of the first anti-wax and anti-corrosion layer is 30 μm, the thickness of the second anti-wax and anti-corrosion layer is 120 μm, and the surface roughness of the first anti-wax and anti-corrosion layer is 0.15 μm.

[0093] Comparative Example 4

[0094] The same anti-wax treatment method as in Example 1 was used to treat the wellbore tubing of the oil and gas thermal recovery well to prevent wax deposition, with the following difference:

[0095] In this embodiment, the first anti-wax and anti-corrosion layer comprises the following components by weight:

[0096] 15 parts epoxy resin, 25 parts phenolic resin, 18 parts methanol, 30 parts ethanol, and 12 parts cobalt trioxide (adhesion enhancer).

[0097] The second anti-wax and anti-corrosion layer comprises the following components by weight:

[0098] 22 parts epoxy resin, 15 parts phenolic resin, 40 parts zirconium oxide powder, 15 parts abrasion-resistant reinforcing agent molybdenum disulfide, and 8 parts surface wettability conversion agent polyvinyl alcohol.

[0099] In this embodiment, the thickness of the first anti-wax and anti-corrosion layer is 30 μm, the thickness of the second anti-wax and anti-corrosion layer is 120 μm, and the surface roughness of the first anti-wax and anti-corrosion layer is 0.15 μm.

[0100] Comparative Example 5

[0101] The same anti-wax treatment method as in Example 1 was used to treat the wellbore tubing of the oil and gas thermal recovery well to prevent wax deposition, with the following difference:

[0102] The first anti-wax and anti-corrosion layer in this embodiment comprises the following components by weight:

[0103] 25 parts epoxy resin, 20 parts phenolic resin, 15 parts methanol, 25 parts ethanol, 15 parts chromium trioxide (adhesion enhancer);

[0104] The second anti-wax and anti-corrosion layer comprises the following components in parts by weight:

[0105] 30 parts epoxy resin, 20 parts phenolic resin, 15 parts organosilicon, 16 parts abrasion-resistant reinforcing agent carbon fiber, 8 parts surface wettability conversion agent molybdenum disulfide, 6 parts surface smoothing agent octyl acrylate copolymer, and 5 parts acrolein.

[0106] In this embodiment, the thickness of the first anti-wax and anti-corrosion layer is 50 μm, the thickness of the second anti-wax and anti-corrosion layer is 150 μm, and the surface roughness of the first anti-wax and anti-corrosion layer is 0.2 μm.

[0107] The coatings prepared in Examples 1-3 and Comparative Examples 1-5 were subjected to performance tests, including the determination of surface contact angle and acid-base tests.

[0108] The contact angle refers to the tangent to the gas-liquid interface at the point where the gas, liquid, and solid phases meet. This tangent contacts the solid-liquid interface on the liquid side. The stronger the interaction force between the droplet and the solid surface, the stronger the surface tension of the droplet itself, and the stronger the interaction force between the liquid and the gas, the smaller the contact angle, and the easier it is for the droplet to spread on the solid surface. Conversely, when the interaction force between the droplet and the solid surface is weak, the contact angle is larger, and the droplet is more likely to form a spherical shape. Contact angle testing can be performed by using the principle of optical projection of the droplet onto the solid surface to analyze and measure the contact angle and surface tension of the liquid and solid samples. Wetting is a common phenomenon in nature and production processes; the process by which the solid-gas interface is replaced by the solid-liquid interface is called wetting. After a liquid and a solid come into contact, the free energy of the system decreases, and the degree of wetting of the liquid on the solid can be calculated by the amount of decrease in the system's free energy.

[0109] Figure 4 The relationship between contact angle and interfacial energy. Figure 5 To express wetting conditions using the contact angle, θ is called the contact angle, which is the angle between the tangents of the solid and liquid surfaces at the three-phase contact point. The size of the contact angle can measure the degree of wetting of the solid by the liquid, and the value of θ can range from 0 to 180°.

[0110] (1) When θ=0°, the liquid completely wets the solid surface or ideally wets it (a), and the liquid is dispersed on the solid surface to theoretically become a monomolecular film.

[0111] (2) When 0 < θ ≤ 90°, the liquid partially wets the solid (b), and the larger θ is, the smaller S is, and the greater the solid's ability to repel water and oil.

[0112] (3) When 90 < θ < 180°, the liquid does not wet the solid (c). If the liquid is water, the solid will repel water; if the liquid is oil, the solid will repel oil.

[0113] (4) When θ = 180°, it is called incomplete wetting (d). It can be seen that the smaller the contact angle θ, the better the wetting, and vice versa.

[0114] The performance test results of the prepared inner coating are shown in Table 1:

[0115] Table 1

[0116] Surface contact angle Acidity test Alkalinity test Example 1 96.2° The coating showed no blistering and had an adhesion rating of 5A. The coating showed no blistering and had an adhesion rating of 5A. Example 2 97.1° The coating showed no blistering and had an adhesion rating of 5A. The coating showed no blistering and had an adhesion rating of 5A. Example 3 98.7° The coating showed no blistering and had an adhesion rating of 5A. The coating showed no blistering and had an adhesion rating of 5A. Comparative Example 1 91.2° The coating has blistering, and the adhesion is rated 3A. The coating shows obvious blistering, and the adhesion is 2A. Comparative Example 2 93.6° The coating shows obvious blistering, and the adhesion is 2A. The coating has slight blistering, and the adhesion is rated 3A. Comparative Example 3 87.2° The coating showed no blistering and had an adhesion rating of 5A. The coating has slight blistering, and the adhesion is 4A. Comparative Example 4 86.5° The coating has slight blistering, and the adhesion is rated 3A. The coating has slight blistering, and the adhesion is 2A. Comparative Example 5 93.1° The coating has slight blistering, and the adhesion is 4A. The coating has slight blistering, and the adhesion is rated 3A.

[0117] As can be seen from the data of Examples 1-3 and Comparative Examples 1-5 above, and the above analysis, the pipe of the present invention has excellent anti-wax and anti-corrosion properties.

[0118] In an application example, the inner coating waxing method of the present invention is used to construct 2 3 / 8"-13 3 / 8" oil pipes.

[0119] First, a thermal cleaning oven is used to remove oil, impurities, and other contaminants from the pipe surface. Then, brown corundum abrasive is used to sandblast the pipe surface. Next, clean high-pressure air is used to blow away the inner wall. High-pressure electrostatic powder coating is then applied to the first anti-wax and anti-corrosion layer of this invention, followed by initial curing in a curing oven. Then, electrostatic powder coating to the second anti-wax and anti-corrosion layer is applied, followed by final complete curing in a curing oven. After complete curing, the pipe is allowed to cool naturally, and the coating thickness and leak detection are performed. The coating thickness meets the 80μm~225μm thickness specified in the SY / T6717 standard, and the entire coated pipe is free of leaks.

[0120] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A wax-resistant and corrosion-resistant inner coating, characterized in that, The inner coating includes a first anti-wax and anti-corrosion layer applied to the inner surface of the steel pipe and a second anti-wax and anti-corrosion layer applied to the surface of the first anti-wax and anti-corrosion layer. The first anti-wax and anti-corrosion layer comprises the following components in parts by weight: 8-25 parts epoxy resin, 10-36 parts phenolic resin, 6-18 parts methanol, 10-35 parts ethanol and 1-15 parts adhesion enhancer; The second anti-wax and anti-corrosion layer comprises the following components by weight: 10-30 parts epoxy resin, 9-25 parts phenolic resin, 20-50 parts zirconium oxide powder, 1-16 parts abrasion and corrosion reinforcing agent, 0.5-10 parts surface wettability conversion agent, and 0.5-6 parts surface smoothing agent.

2. The anti-wax and anti-corrosion inner coating according to claim 1, characterized in that, The adhesion enhancer is one or more of titanium dioxide, cobalt trioxide, and chromium trioxide.

3. The anti-wax and anti-corrosion inner coating according to claim 1, characterized in that, The wear-resistant reinforcing agent is one or more of silicon dioxide, molybdenum disulfide, silicon carbide, and carbon fiber.

4. The anti-wax and anti-corrosion inner coating according to claim 1, characterized in that, The surface wettability conversion agent is one or more of polytetrafluoroethylene, polyvinyl alcohol, and molybdenum disulfide.

5. The anti-wax and anti-corrosion inner coating according to claim 1, characterized in that, The surface smoothing agent is one or more of titanium dioxide, tantalum pentoxide, and octyl acrylate copolymer.

6. A method for preventing wax buildup, characterized in that, Applying the anti-wax and anti-corrosion inner coating as described in any one of claims 1-5 to the inner surface of the pipe specifically includes the following steps: Receive the pipes used for coating and inspect the pipes, including inspecting the appearance, specifications, quantity, and whether there are sharp edges and burrs on the inner surface of the pipes; Prepare the first and second anti-wax and anti-corrosion layers respectively; The pipe is placed in a gas-fired heating furnace to remove oil and impurities from the inner wall of the pipe, resulting in a clean pipe. The inner surface of the clean pipe was sandblasted using brown fused alumina, and the defects of the pipe and the wall thickness of the pipe after sandblasting were measured to confirm the surface cleanliness, roughness, temperature and relative humidity of the steel pipe surface, and the dwell time before coating after shot blasting. The first anti-wax and anti-corrosion layer is sprayed onto the inner wall of the pipe at room temperature and pre-cured. Then, the second anti-wax and anti-corrosion layer is sprayed onto the first anti-wax and anti-corrosion layer for a second curing. After complete curing, the coating appearance, thickness, and leaks are inspected, and qualified products are selected.

7. The method for preventing wax buildup according to claim 6, characterized in that, The thickness of the first anti-wax and anti-corrosion layer is 25-50 μm.

8. The method for preventing wax buildup according to claim 6, characterized in that, The thickness of the second anti-wax and anti-corrosion layer is 100-150 μm.

9. The method for preventing wax buildup according to claim 6, characterized in that, The surface roughness of the first anti-wax and anti-corrosion layer is 0.10 to 0.20 μm.

10. The application of the anti-wax and anti-corrosion inner coating according to any one of claims 1-5 or the anti-wax deposition method according to any one of claims 6-9 in the wellbore tubing of a production well.

Images