Glass fiber reinforced plastic oil pipe connecting structure and preparation method thereof

Abstract

The invention provides a glass fiber reinforced plastic oil pipe connecting structure and a preparation method thereof.The method comprises the steps that 40-60 parts by mass of bisphenol A epoxy resin, 3-8 parts by mass of polyfunctionality epoxy, 2-5 parts by mass of epoxy diluent, 0.1-0.5 part by mass of coupling agent, 20-40 parts by mass of curing agent and 0.1-0.5 part by mass of accelerant are mixed, stirred and left to stand, and thermosetting resin mixed liquid is obtained; the fiber soaked with the thermosetting resin mixed liquid glue solution is wound on a core mold to be cured and formed to obtain the glass fiber reinforced plastic oil pipe connecting structure, the fiber is carbon fiber or aramid fiber with the modulus higher than that of glass fiber, and the core mold is set according to the size of the glass fiber reinforced plastic oil pipe connecting structure. The connecting structure is matched with the application of high well depth, high-temperature-resistant epoxy resin is used in a composite material, two resins with different epoxy equivalents ensure the toughness of the epoxy resin (the toughness is increased by high epoxy equivalents), the viscosity of the resin is reduced by the diluent, but no solvent exists. The final resin formula has good processability and good toughness, can be cured at medium and high temperatures, and has a long-term use temperature of 120 DEG C or above.

Description

Technical Field

[0001] The invention belongs to the field of exploration, and in particular relates to a glass fiber reinforced plastic oil pipe connection structure and a preparation method thereof. Background Art

[0002] Oil pipes play an extremely important role in the exploration and development of oil and gas fields. At present, most of the oil pipes used in domestic and foreign oil fields are made of steel. However, with the in-depth development of oil and gas fields, H2S, CO2, Cl - The content of associated substances such as water and microorganisms gradually increases, resulting in aggravated corrosion of underground steel oil pipes, frequent perforation failures, and greatly reduced pipe service life. FRP material has excellent corrosion resistance and can fundamentally solve the corrosion problem of steel pipes. FRP oil pipes also have a series of advantages such as moderate price, high specific strength, and strong structural designability, and have gradually become one of the important choices to replace steel oil pipes.

[0003] However, with the increase in the depth of wells, the downhole temperature has also gradually increased, which has put forward higher requirements for various downhole tool materials. At present, according to the requirements of standard SY / T 7043-2016, the long-term maximum operating temperature of my country's FRP oil pipes is 93°C (corresponding to a well depth of 2500m). In order to further expand the scope of application of FRP oil pipes, it is necessary to improve the temperature resistance of the oil pipe resin. At the same time, as the well depth increases, the weight of the pipe body increases, so the connection strength of the oil pipe also needs to be increased. The strength of the FRP couplings currently used is limited, and there is a relatively serious sticking problem. There is a method to use stainless steel and other metal material couplings to replace FRP couplings, but the metal material still has the problem of easy corrosion. The present invention provides a method for preparing a corrosion-resistant, high-temperature-resistant, high-strength composite material oil pipe coupling, which can effectively expand the application range of FRP oil pipes.

[0004] FRP oil pipe is a type of oil pipe used downhole. Its main material is continuous fiber reinforced thermosetting resin material, which can effectively avoid the corrosion problem of metal oil pipe. The connection method is threaded. Usually, there is a male thread processed on the pipe end. The two pipe sections share a coupling, and the coupling is processed with a female thread. Figure 1 As shown, the existing FRP oil pipe couplings mainly include two types, one is FRP with the same material as the pipe body, and the other is a metal coupling such as stainless steel. However, the FRP coupling has low strength and is prone to sticking. In addition, due to the limited strength of glass fiber, a coupling that is too thick to increase the strength will occupy more annulus of the oil well. Metal couplings have the same corrosion problem as metal oil pipes, and cannot give full play to the corrosion resistance of FRP oil pipes. Summary of the Invention

[0005] In view of the above problems, the present invention proposes a method for preparing a glass fiber reinforced plastic oil pipe connection structure, the method comprising:

[0006] Mix 40-60 parts of bisphenol A epoxy resin, 3-8 parts of multifunctional epoxy, 2-5 parts of epoxy diluent, 0.1-0.5 parts of coupling agent, 20-40 parts of curing agent and 0.1-0.5 parts of accelerator according to mass ratio, stir and stand to obtain a thermosetting resin mixture;

[0007] The fiber soaked in the thermosetting resin mixture is wound onto a core mold and solidified to form a glass fiber reinforced plastic oil pipe connection structure, wherein the core mold is set according to the size of the glass fiber reinforced plastic oil pipe connection structure.

[0008] Furthermore, the bisphenol A epoxy resin includes two resins with different epoxy equivalents, wherein the epoxy equivalent of one resin is 180g / eq-250g / eq, and the epoxy equivalent of the other resin is 500g / eq-700g / eq.

[0009] Furthermore, the functionality of the multifunctional epoxy is 2.5-4.0.

[0010] Furthermore, the epoxy diluent is a glycidyl ether compound, and the viscosity of the glycidyl ether compound is 1.2 mPa·s-4 mPa·s.

[0011] Furthermore, the curing agent is an acid anhydride curing agent, including one or more of phthalic anhydride, tetrahydrophthalic anhydride, phthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and aliphatic anhydrides.

[0012] Furthermore, the accelerator is an organic amine or imidazole accelerator.

[0013] Furthermore, the curing temperature of the curing molding is 120° C.-180° C., and the curing time is 1 hour-3 hours.

[0014] Furthermore, the fiber weight accounts for 25%-35%, and the fiber includes carbon fiber and aramid fiber.

[0015] The present invention also provides a connection structure, which is obtained by the preparation method of the present invention. The connection structure includes a cylinder, an internal thread is provided on the contact surface between the cylinder and the fiberglass reinforced plastic oil pipe, and an external thread is provided on the outer surface of the fiberglass reinforced plastic oil pipe. The internal thread and the external thread cooperate to complete the connection of the fiberglass reinforced plastic oil pipe.

[0016] Furthermore, the load-bearing flank angle of the thread is greater than the embedding flank angle, and is 2-3 times the embedding flank angle.

[0017] The fiberglass reinforced plastic (FRP) oil pipe connection structure and its preparation method utilize high-modulus composite materials, such as carbon fiber, to ensure strength while avoiding corrosion issues associated with metal couplings. Furthermore, due to the modulus difference with FRP, the problem of galling between the FRP external thread and the high-modulus coupling internal thread can be effectively resolved. Furthermore, the internal thread of the present invention utilizes a load-bearing flank angle greater than the embedding flank angle to ensure thread tensile strength. The connection structure of the present invention utilizes a highly heat-resistant epoxy resin in the composite material for high-well depth applications. Two resins with different epoxy equivalent weights ensure the epoxy resin's toughness (high epoxy equivalent weight increases toughness), while a diluent reduces resin viscosity. The solvent-free design allows for easy processing and excellent toughness. The resulting resin formulation exhibits excellent curing properties at medium to high temperatures, with long-term operating temperatures exceeding 120°C.

[0018] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 A schematic diagram of a coupling thread in the prior art is shown;

[0021] Figure 2 A schematic diagram of the thread structure of the fiberglass reinforced plastic oil pipe connection structure in an embodiment of the present invention is shown.

[0022] In the figure, 1-embedding flank angle, 2-load flank angle. DETAILED DESCRIPTION

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0024] An embodiment of the present invention provides a fiberglass reinforced plastic oil pipe connection structure, including a threaded structure and a barrel portion, wherein the thread and the barrel are composed of a high-modulus fiber composite material; a high-temperature resistant thermosetting resin is used in the high-modulus composite material; the thread structure is a special thread with high tensile strength; the thread and the barrel are formed by composite material molding methods such as fiber winding, wherein the fiber weight accounts for 25%-35%.

[0025] In the embodiment of the present invention, the high modulus composite material is composed of continuous fibers and thermosetting resin, and the fibers are materials such as carbon fibers and aramid fibers having a modulus higher than that of glass fibers.

[0026] In the embodiment of the present invention, the resin is a high-temperature resistant resin system that can be cured at medium to high temperatures, and the resin system includes bisphenol A epoxy resin (40-60), multifunctional epoxy (3-8), epoxy diluent (2-5), coupling agent (0.1-0.5), curing agent (20-40) and accelerator (0.1-0.5);

[0027] In an embodiment of the present invention, in order to increase the operating temperature while reducing the toughness of the resin, the bisphenol A epoxy resin is composed of two types of resins with different epoxy equivalents, one of which has an epoxy equivalent of 180g / eq-250g / eq, such as E44, E51, E54, etc., and one has an epoxy equivalent of 500g / eq-700g / eq, such as E12, E20, etc., and the ratio of the two is 4:1 to 5:1;

[0028] The multifunctional epoxy functionality is 2.5-4.0, such as AG-80, TED85, etc.

[0029] The epoxy diluent is a glycidyl ether compound with a viscosity of 1.2 mPa·s (25°C) to 4 mPa·s (25°C), such as butyl glycidyl ether, butanediol diglycidyl ether, etc.;

[0030] The curing agent is an acid anhydride curing agent, such as one or more of phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, aliphatic anhydride, etc.;

[0031] The accelerator is an organic amine or imidazole, such as DMP-30, 2-methylimidazole, etc.

[0032] In order to ensure the tensile strength of the thread, the load flank angle of the thread is greater than the embedding flank angle, and is 2-3 times the embedding flank angle. In the embodiment of the present invention, Figure 2 It shows a schematic diagram of the thread structure of the glass fiber reinforced plastic oil pipe connection structure in an embodiment of the present invention. Figure 2In the embodiment of the present invention, the angle of the load-bearing tooth side angle is set to 81°, the angle of the embedded tooth side angle is set to 35°, and the load-bearing tooth side angle is 2.3 times the embedded tooth side angle. In the embodiment of the present invention, the setting of the embedded tooth side angle and the load-bearing tooth side angle is only an example. As long as it does not deviate from the content of the angle change of the present invention, it is within the protection scope of the present invention.

[0033] After winding on the core mold, it is cured to form a composite material coupling, with a curing temperature of 120°C-180°C and a curing time of 1h-3h.

[0034] After the preparation of the FRP oil pipe connection structure in the embodiment of the present invention is completed, the FRP oil pipe connection structure is installed on the FRP oil pipe, wherein the coupling has an internal thread and the oil pipe end has an external thread, and the make-up and breakout and tensile tests are performed to measure the performance of the FRP oil pipe connection structure prepared by the present invention.

[0035] The present invention also provides comparative examples and multiple examples to better illustrate the performance of the glass fiber reinforced plastic oil pipe connection structure prepared by the present invention:

[0036] Example 1

[0037] 40 parts of E54, 10 parts of E20, 5 parts of AG-80, 3 parts of butyl glycidyl ether, 0.5 parts of KH-550, 25 parts of phthalic anhydride, 5 parts of triethylenetetramine, and 0.5 parts of DMP-30 were mixed, stirred, and allowed to stand to obtain a thermosetting resin mixture;

[0038] The carbon fiber T300 impregnated with a thermosetting resin mixture is wound onto a core mold and cured to form a glass fiber reinforced plastic oil pipe connection structure. In the embodiment of the present invention, in order to better measure the glass fiber reinforced plastic oil pipe connection structure, the core mold is prepared with a uniform size.

[0039] Example 2

[0040] Take 50 parts of E54, 10 parts of E20, 6 parts of TED85, 2 parts of butyl glycidyl ether, 0.5 parts of KH-550, 20 parts of phthalic anhydride, 5 parts of methyltetrahydrophthalic anhydride, and 0.5 parts of DMP-30 by mass ratio, mix and stir, and let it stand to obtain a thermosetting resin mixture;

[0041] The carbon fiber T300 impregnated with a thermosetting resin mixture is wound onto a core mold and cured to form a fiberglass reinforced plastic oil pipe connection structure.

[0042] Example 3

[0043] 40 parts of E54, 10 parts of E12, 5 parts of AG-80, 2 parts of allyl glycidyl ether, 0.5 parts of KH-550, 25 parts of phthalic anhydride, 5 parts of triethylenetetramine, and 0.5 parts of DMP-30 were mixed, stirred, and allowed to stand to obtain a thermosetting resin mixture;

[0044] A glass fiber reinforced plastic oil pipe connection structure is obtained by winding aramid Kevlar-29 impregnated with a thermosetting resin mixture onto a core mold and curing and forming it.

[0045] Example 4

[0046] 50 parts of E44, 5 parts of E20, 5 parts of TED85, 2 parts of butyl glycidyl ether, 0.5 parts of KH-560, 20 parts of phthalic anhydride, 5 parts of triethylenetetramine, and 0.5 parts of triethylamine were mixed, stirred, and allowed to stand to obtain a thermosetting resin mixture;

[0047] The carbon fiber T300 impregnated with a thermosetting resin mixture is wound onto a core mold and cured to form a fiberglass reinforced plastic oil pipe connection structure.

[0048] Comparative Example 1

[0049] 40 parts of E54, 10 parts of E20, 5 parts of AG-80, 3 parts of butyl glycidyl ether, 0.5 parts of KH-550, 25 parts of phthalic anhydride, 5 parts of triethylenetetramine, and 0.5 parts of DMP-30 were mixed, stirred, and allowed to stand to obtain a thermosetting resin mixture;

[0050] The glass fiber SE2348 impregnated with a thermosetting resin mixture is wound onto a core mold and solidified to form a glass fiber reinforced plastic oil pipe connection structure.

[0051] In the examples of the present invention, the performance of the comparative examples and examples 1-3 will also be described:

[0052] Oil pipe connection tensile strength (kN) Number of make-up and break-out failures / times Comparative Example 1 247 32 Example 1 387 ＞50 Example 2 354 ＞50 Example 3 309 ＞50 Example 4 299 ＞50

[0053] By comparing the performance of the glass fiber reinforced plastic oil pipe connection structure prepared in Example 1 and Comparative Example 1, it can be clearly seen that the tensile strength of the oil pipe connection when glass fiber is selected as the fiber type is significantly lower than the tensile strength of the oil pipe connection when carbon fiber is selected as the fiber type, and the number of make-up and make-down failures when glass fiber is selected as the fiber type is lower than the number of make-up and make-down failures when carbon fiber is selected as the fiber type; Examples 1-3 of the present invention respectively illustrate the fiber type, the content of bisphenol A epoxy resin, and the type of high-functionality epoxy, and it can be clearly seen that the tensile strength of the oil pipe connection of the connection structure prepared from the high modulus fiber composite material of the present invention is greater than 300, and the number of make-up and make-down failures is greater than 50 times.

[0054] The high connection strength structure provided by the present invention allows the fiberglass reinforced plastic oil pipe to be used in deeper wells, while providing better corrosion resistance, effectively avoiding thread sticking, and not increasing the difficulty of installation operations.

[0055] The fiberglass reinforced plastic (FRP) oil pipe connection structure and its preparation method utilize high-modulus composite materials, such as carbon fiber, to ensure strength while avoiding corrosion issues associated with metal couplings. Furthermore, due to the modulus difference with FRP, the problem of galling between the FRP external thread and the high-modulus coupling internal thread can be effectively resolved. Furthermore, the internal thread of the present invention utilizes a load-bearing flank angle greater than the embedding flank angle to ensure thread tensile strength. The connection structure of the present invention utilizes a highly heat-resistant epoxy resin in the composite material for high-well depth applications. Two resins with different epoxy equivalent weights ensure the epoxy resin's toughness (high epoxy equivalent weight increases toughness), while a diluent reduces resin viscosity. The solvent-free design allows for easy processing and excellent toughness. The resulting resin formulation exhibits excellent curing properties at medium to high temperatures, with long-term operating temperatures exceeding 120°C.

[0056] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein; and these modifications or replacements 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 method for preparing a glass fiber reinforced plastic oil pipe connection structure, characterized in that: The method comprises: According to the mass ratio, 40-60 parts of bisphenol A epoxy resin, 3-8 parts of multifunctional epoxy, 2-5 parts of epoxy diluent, 0.1-0.5 parts of coupling agent, 20-40 parts of curing agent and 0.1-0.5 parts of accelerator are mixed, stirred and allowed to stand to obtain a thermosetting resin mixture; The fiber impregnated with the thermosetting resin mixed liquid glue is wound onto a core mold and solidified to obtain a glass fiber reinforced plastic oil pipe connection structure, wherein the core mold is set according to the size of the glass fiber reinforced plastic oil pipe connection structure.

2. The method for preparing the glass fiber reinforced plastic oil pipe connection structure according to claim 1, characterized in that: The bisphenol A epoxy resin comprises two resins with different epoxy equivalents, wherein the epoxy equivalent of one resin is 180 g / eq-250 g / eq, and the epoxy equivalent of the other resin is 500 g / eq-700 g / eq.

3. The method for preparing the glass fiber reinforced plastic oil pipe connection structure according to claim 2, characterized in that: The functionality of the multifunctional epoxy is 2.5-4.

0.

4. The method for preparing the glass fiber reinforced plastic oil pipe connection structure according to claim 1, characterized in that: The epoxy diluent is a glycidyl ether compound, and the viscosity of the glycidyl ether compound is 1.2 mPa·s-4 mPa·s.

5. The method for preparing the glass fiber reinforced plastic oil pipe connection structure according to claim 4, characterized in that: The curing agent is an acid anhydride curing agent, including one or more of phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and aliphatic anhydride.

6. The method for preparing the glass fiber reinforced plastic oil pipe connection structure according to claim 5, characterized in that: The accelerator is an organic amine or imidazole accelerator.

7. The method for preparing a glass fiber reinforced plastic oil pipe connection structure according to any one of claims 1 to 6, characterized in that: The curing temperature of the curing molding is 120° C.-180° C., and the curing time is 1 h-3 h.

8. The method for preparing a glass fiber reinforced plastic oil pipe connection structure according to claim 7, characterized in that: The fiber weight accounts for 25%-35%, and the fiber includes carbon fiber and aramid fiber.

9. A connection structure prepared by the method for preparing a fiberglass reinforced plastic oil pipe connection structure according to any one of claims 1 to 8, characterized in that: The connection structure comprises a cylinder, wherein the contact surface between the cylinder and the FRP oil pipe is provided with an internal thread, and the outer surface of the FRP oil pipe is provided with an external thread, and the internal thread and the external thread cooperate to complete the connection of the FRP oil pipe.

10. The connection structure according to claim 9, characterized in that: The load-bearing flank angle of the thread is greater than the embedding flank angle and is 2-3 times the embedding flank angle.

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