Wear-resistant sucker rod coupling and preparation method thereof

Abstract

The application relates to an oil extraction technology field and relates to a wear-resistant sucker rod coupling and a preparation method thereof. The wear-resistant sucker rod coupling solves the problem that the existing method for treating the wear between the sucker rod coupling and the oil pipe cannot realize bidirectional protection and the service period is short after being lowered into a well. The preparation raw materials of the wear-resistant sucker rod coupling include carborundum, polyhexamethylene adipamide, a multi-element curing polymer and molybdenum disulfide; the mass percentage content of each raw material component is as follows: carborundum 91.5-95%, polyhexamethylene adipamide 3-5%, the multi-element curing polymer 0.5-2% and molybdenum disulfide 1.5%; the preparation method comprises the following steps: S1. raw material pretreatment; S2. melt blending: polyhexamethylene adipamide is heated to a melt state, and carborundum, molybdenum disulfide and multi-element curing polymer powder are mixed after being preheated; S3. forming and curing; and S4. post-treatment. The wear-resistant sucker rod coupling can realize bidirectional protection and effectively prolong the pump inspection period of the pumping unit well.

Description

Technical Field

[0001] This invention relates to the field of oil extraction technology, and in particular to a wear-resistant sucker rod coupling and its preparation method. Background Technology

[0002] Wear between the sucker rod coupling and the tubing refers to the unavoidable contact friction caused by the tension, compression, or non-linear motion of the pumping unit during its up-and-down movement. Due to prolonged reciprocating motion, the sucker rod coupling and the tubing in contact with it experience wear, or even damage and breakage.

[0003] Reducing the wear between the sucker rod coupling and the tubing, and extending the working time of the sucker rod and tubing in the well, can increase the pump inspection cycle of the pumping unit and reduce the amount of maintenance work in production, thereby reducing operation and maintenance costs and labor costs.

[0004] Currently, with the continuous increase in water cut in oilfields, rod and tubing wear has become the biggest bottleneck restricting the development of oil production technology in pumping wells. In water-fuel dual-drive oil wells, rod and tubing wear has become a major factor leading to shortened pump inspection cycles and increased maintenance workload. In recent years, tools such as externally coated couplings, integrated protectors, and cast-in-place centralizers have been used to address rod and tubing wear, achieving some results. However, two problems remain: First, existing anti-wear measures are less effective in treating wells with severe wear in high water cuts; second, while existing anti-wear rod coupling measures can avoid many problems associated with installing nylon centralizers, they cannot achieve both bidirectional protection and delayed wear of the rod coupling and tubing. This results in severe tubing wear when the rod coupling is protected, and vice versa, leading to a shortened service life when both the rod coupling and tubing are protected. Summary of the Invention

[0005] This invention addresses the problems of existing methods for handling wear between sucker rod couplings and tubing in pumping wells, which lack bidirectional protection and have short service life after being run into the well. The invention provides a wear-resistant sucker rod coupling. This wear-resistant coupling provides bidirectional protection, extending the working time of both the sucker rod and tubing, thus effectively extending the pump inspection cycle of the pumping well. This invention also provides a method for manufacturing the wear-resistant sucker rod coupling.

[0006] The present invention solves its problems through the following technical solution:

[0007] This invention provides a wear-resistant sucker rod coupling, the raw materials for which include corundum, polyhexamethylene adipamide, multi-component cured polymer and molybdenum disulfide;

[0008] The mass percentage content of each raw material component is as follows: corundum 91.5-95%, polyhexamethylene adipamide 3-5%, multi-component cured polymer 0.5-2%, and molybdenum disulfide 1.5%.

[0009] Furthermore, it includes a mandrel, the central hole of which is internally threaded to a sucker rod; a rotating anti-friction body is connected to the middle of the outer wall of the mandrel;

[0010] The outer working surface of the rotary wear reducer is a circular arc surface; the curvature of the circular arc surface of the rotary wear reducer is the same as the curvature of the circular arc surface of the inner wall of the oil pipe.

[0011] Furthermore, anti-detachment grooves are respectively opened at both the front and rear ends of the outer wall of the mandrel.

[0012] Furthermore, the openings at both ends of the mandrel have inner and outer chamfers; the edge of the anti-detachment groove has an outer chamfer.

[0013] Furthermore, ball bearings are installed at the connection between the rotating friction reducing body and the spindle.

[0014] Another aspect of the present invention provides a method for preparing a wear-resistant sucker rod coupling, comprising the following steps:

[0015] S1. Prepare raw materials and pre-treat them;

[0016] S2. Melt-blending the raw material components.

[0017] Polyhexamethylene adipamide is heated to a molten state, while corundum, molybdenum disulfide, and multi-component curable polymer powder are preheated to an appropriate temperature and then mixed in proportion. During the mixing process, the pressure is 0.1 MPa to 1 MPa. The mixed material is then processed through a melt blending process (injection molding).

[0018] The mixed materials are processed through melt blending (injection molding); the multi-component cured polymer undergoes a cross-linking reaction when blended with nylon 66 to form a three-dimensional network structure, which enhances the mechanical properties and heat resistance of the material; as a thermoplastic polymer, nylon 66 is combined with corundum and MoS2 through melt blending, and corundum and MoS2 serve as fillers to enhance its mechanical properties;

[0019] S3, Molding and Curing

[0020] The molten blended material is injected into a mold and then pressed or injection molded to obtain the desired shape. During the molding process, the temperature and pressure are controlled to ensure that the material is fully cured and forms a uniform structure.

[0021] S4. Cooling and Post-treatment

[0022] The shaped material is annealed and gradually cooled to room temperature; during the cooling process, a pressure of 0.1 MPa to 1 MPa is maintained to prevent deformation.

[0023] Furthermore, the raw materials for preparing the wear-resistant sucker rod coupling connecting the mandrel and the rotating anti-friction body include corundum, polyhexamethylene adipamide (nylon 66), multi-component cured polymer, and molybdenum disulfide;

[0024] Furthermore, in the melt blending stage, polyhexamethylene adipamide is heated to a molten state temperature of approximately 260°C; simultaneously, corundum, molybdenum disulfide, and multi-component cured polymer powder are preheated to a temperature of 100-200°C.

[0025] Furthermore, during the molding process, the temperature is controlled at 220-240℃ and the pressure is controlled at 0.1-1MPa.

[0026] Furthermore, the components of the raw materials undergo pretreatment, including:

[0027] The surface of the corundum is polished using a silane coupling agent to improve its compatibility with the polymer matrix; the polyhexamethylene adipamide is dried to remove moisture and prevent the formation of bubbles or degradation during processing.

[0028] Compared with the above-mentioned background technology, the present invention has the following beneficial effects:

[0029] This invention provides a specific sucker rod coupling, which is designed for oil wells where sucker rod couplings and tubing are prone to wear. It can effectively reduce the wear of sucker rod couplings and tubing, thus reducing the number of wells requiring pump inspection due to wear of sucker rod couplings and tubing. This results in an overall extension of the oil well production cycle, extending the pump inspection cycle by more than 2 times, with an input-output ratio of 1:2.3.

[0030] This invention features simple process and strong operability, which is conducive to the field promotion and application of wells with worn couplings; the wear-resistant sucker rod coupling of this invention has strong applicability and is suitable for maintenance operations of all pumping wells with worn couplings and worn tubing.

[0031] This invention enables targeted placement of wells with uneven wear, which can reduce rod and tubing wear while extending the pump inspection cycle and reducing operation and maintenance costs and labor costs. Attached Figure Description

[0032] Figure 1 This is a front view of the wear-resistant sucker rod coupling of the present invention;

[0033] Figure 2 For the appendix Figure 1 Sectional view along line EE;

[0034] Figure 3 For the appendix Figure 1 Sectional view along the CC line;

[0035] Figure 4 This is a schematic diagram of the three-dimensional structure of the wear-resistant sucker rod coupling of the present invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0037] Terminology and description of this invention:

[0038] 1. As used herein, numerical range: Unless otherwise expressly indicated, all ranges or ratios disclosed herein shall be understood to include any and all subranges or subratios contained herein. For example, a stated range or ratio of 1 to 30 shall be considered to be included between a minimum value of 1 and a maximum value of 30, and includes any subranges or subratios, integers, decimals, or subranges or subratios consisting of integers or decimals, including endpoints.

[0039] 2. As used herein, the terms “comprising,” “including,” “having,” “possessing,” “may,” “containing,” and their variations are open-ended conjunctions or terms that do not exclude the possibility of other components or structures.

[0040] 3. As used in this article, equal curvature means that two or more geometric objects (such as curves or surfaces) have the same degree of curvature at a certain point or within a certain region. Curvature is a mathematical quantity that describes the degree of curvature of a geometric object, and its specific definition is as follows:

[0041] The definition of curvature, for a planar curve, is the degree of bending of the curve at a given point. The greater the curvature, the more pronounced the bending; when the curvature is zero, the curve is a straight line. For a surface, curvature is usually described by principal curvatures (i.e., the maximum and minimum degree of bending of the surface at a given point).

[0042] The same curvature means that if two curves have the same curvature at a point, it means that they bend to the same degree at that point. If two surfaces have the same curvature at a point, it means that they have the same principal curvature at that point.

[0043] The following non-limiting embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way. The following content is merely an exemplary description of the scope of protection claimed by the present invention, and those skilled in the art can make various changes and modifications to the present invention based on the disclosed content, and such changes should also fall within the scope of protection claimed by the present invention.

[0044] like Figure 1 , Figure 2As shown, a wear-resistant sucker rod coupling is prepared from the following raw materials: corundum, polyhexamethylene adipamide (nylon 66), a multi-component cured polymer, and molybdenum disulfide. The mass percentage content of each raw material is as follows: corundum 91.5-95%, polyhexamethylene adipamide 3-5%, multi-component cured polymer 0.5-2%, and molybdenum disulfide 1.5%. The multi-component cured polymer is sebacate dihydrazide.

[0045] The wear-resistant sucker rod coupling includes a mandrel 1 with an internal thread on its inner wall for connecting the sucker rod and transmitting torque; a rotating anti-friction body 2 is connected to the middle of the outer wall of the mandrel; anti-slip grooves 3 are respectively opened at the front and rear ends of the outer wall of the mandrel to prevent relative slippage between the coupling and the sucker rod under axial load; the mandrel 1 has an inner chamfer 5 and an outer chamfer 4 at both ends; the inner chamfer 5 at the end avoids sharp corners and serves as a guide slope to reduce collision damage during docking and facilitate installation guidance; the outer chamfer 4 at the end guides the smooth flow of downhole fluid, reduces erosion caused by turbulence, reduces stress concentration, and optimizes fluid flow. Figure 4 As shown, the anti-slip groove edge is provided with an outer chamfer 7, which is used to reduce stress concentration at the groove opening and avoid crack initiation. In particular, it significantly delays fatigue failure under alternating loads, thereby improving the fatigue life of the anti-slip groove.

[0046] like Figure 3 As shown, ball bearings 6 are installed at the connection between the rotating wear-reducing body and the mandrel. These ball bearings are embedded between the sliding sleeve and the mandrel, forming a rolling pair. Their function is to convert sliding friction into rolling friction, significantly reducing friction and wear. The outer working surface of the rotating wear-reducing body is a curved surface; the curvature of the curved surface of the rotating wear-reducing body is the same as the curvature of the curved surface of the inner wall of the tubing. Common tubing curvature is: for small casing wells with a diameter of 60mm, the tubing curvature is 0.0161 mm. -1 For conventional casing wells, the tubing curvature is 0.0132 mm (∮73). -1 ), 89mm tubing curvature in large-casing wells: 0.0112 (mm) -1 ).

[0047] The preparation method of sucker rod coupling raw material includes the following steps:

[0048] Step 1: Prepare raw materials and pre-treat them; specifically including:

[0049] S11 Standards for Selecting Sucker Rod Coupling Materials

[0050] The selection criteria for sucker rod couplings are: after being subjected to a positive pressure of 20N (3MPa) and operating for 300,000 cycles, the wear rate of the tubing surface is less than 4.96×10⁻⁶. -7 g / n, the wear rate of the sucker rod coupling surface is less than 2.29×10 -7g / n; corrosion resistant in crude oil; impact resistant; high surface finish.

[0051] S12. Determination of coupling material

[0052] The sucker rod coupling is mainly composed of diamond, polyhexamethylene adipamide (nylon 66), a multi-component cured polymer, and molybdenum disulfide as a solid lubricant. The functions of each component are as follows:

[0053] Carborundum, as a reinforcing filler, improves the hardness and wear resistance of the material; polyhexamethylene adipamide (Nylon 66), with impact resistance and wear resistance, serves as a matrix material, providing mechanical strength and toughness; multi-component cured polymer (dihydrazide sebacate), as a curing agent or crosslinking agent, enhances the heat resistance and chemical stability of the material; molybdenum disulfide (MoS2), as a lubricant, reduces the coefficient of friction and improves the self-lubricating properties of the material.

[0054] The raw materials for preparing the sucker rod coupling, which is formed by connecting the mandrel and the rotating friction reducer, are determined to be corundum, polyhexamethylene adipamide (nylon 66), a multi-component curing polymer, and molybdenum disulfide; the mass percentage content of each raw material is: corundum 91.5-95%, polyhexamethylene adipamide 3-5%, multi-component curing polymer 0.5-2%, and molybdenum disulfide 1.5%; the multi-component curing polymer is sebacate dihydrazide.

[0055] For the corundum in the raw materials, a silane coupling agent is used to polish the surface of the corundum to improve its compatibility with the polymer matrix; molybdenum disulfide is used to ensure that the particles are evenly dispersed and to avoid agglomeration; for the nylon 66 in the raw materials, a drying process is performed to remove moisture and prevent the generation of bubbles or degradation during processing.

[0056] Step 2: Melt blending

[0057] Nylon 66 is heated to a molten state (temperature 259-267℃), while the corundum, molybdenum disulfide and multi-component curable polymer powder are preheated to an appropriate temperature (100-200℃) and then mixed; during the mixing process, the pressure is controlled at 0.1-1MPa.

[0058] The mixed materials are processed through melt blending (injection molding); sebacic acid dihydrazide undergoes a cross-linking reaction when blended with nylon 66, forming a three-dimensional network structure that enhances the material's mechanical properties and heat resistance. As a thermoplastic polymer, nylon 66 is melt-blended with corundum and MoS2, with corundum and MoS2 acting as fillers to enhance its mechanical properties.

[0059] Step 3: Molding and Curing

[0060] The molten blended material is injected into a mold and then pressed or injection molded to obtain the desired shape. During the molding process, the temperature is controlled at 220-240℃ and the pressure is controlled at 0.1-1MPa to ensure that the material is fully cured and forms a uniform structure.

[0061] Step 4, Post-processing

[0062] The formed material is annealed and gradually cooled to room temperature to avoid rapid cooling that could cause internal stress, thus improving dimensional stability and mechanical properties. During the cooling process, a pressure of 0.1-1 MPa is maintained to prevent deformation.

[0063] Testing of sucker rod coupling performance

[0064] The RFT-III reciprocating friction and wear testing machine was used to test the wear rate of the sucker rod coupling surface after 400,000 cycles with a normal load of 30 N (3.5 MPa). The result was 2.29 × 10⁻⁶. -8 g / n, the wear rate of the oil pipe surface is 4.96×10 -8 g / n.

[0065] Example 1

[0066] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and the actual application effect of well xxxx in a certain oil field.

[0067] For a certain oilfield, 217 wells with severe uneven wear were selected for specific sucker rod coupling anti-uneven wear field tests. All of them were tested in the well during maintenance operations.

[0068] The wear-resistant sucker rod coupling is prepared from the following raw materials: corundum, polyhexamethylene adipamide (nylon 66), a multi-component cured polymer, and molybdenum disulfide. The mass percentage content of each raw material is as follows: corundum 93.5%, polyhexamethylene adipamide 4%, multi-component cured polymer 1.5%, and molybdenum disulfide 1.5%. The wear-resistant sucker rod coupling is prepared according to the method of this invention.

[0069] After being connected to the well via a wear-resistant sucker rod coupling, the sucker rod is lowered into the well. As the sucker rod coupling reciprocates up and down, the inner diameter of the rotating body matches the outer diameter of the sucker rod coupling itself. When the sucker rod coupling contacts the tubing, under the normal pressure between the tubing and the rod, one of the working surfaces of the rotating wear-resistant body automatically adapts to the shape of the tubing's inner wall and contacts the tubing. Through the contact between the rotating wear-resistant body and the tubing, the rotating wear-resistant body of the coupling changes the previous line contact method to surface contact, thereby effectively reducing the contact stress between the tubing and the rod. Furthermore, combined with the specific material of the sucker rod coupling, it reduces the wear between the sucker rod and the tubing, achieving the purpose of bidirectional protection, increasing the service life of the tubing and the sucker rod, and thus extending the oil well production cycle.

[0070] A survey of 217 wells that had their specific sucker rod couplings replaced revealed that 134 wells had exceeded the previous eccentric wear pump inspection cycle in the maintenance-free period. The average eccentric wear pump inspection cycle for these wells before the oil test was 109 days, and it has now exceeded the original eccentric wear pump inspection cycle by 294 days.

[0071] Table 1 shows a comparison of production conditions before and after the application of specific sucker rod couplings in the pumping unit. Analysis of the production data before and after the replacement of the specific sucker rod couplings shows that after replacing the conventional whole-well straightening measures with specific sucker rod couplings, the average maximum load of the oil well decreased by 3.1 kN, the average minimum load increased by 1.2 kN, and the average alternating load decreased by 4.3 kN. This not only effectively extended the pump inspection cycle due to uneven wear, but also significantly improved the pumping condition of the oil well, and further reduced the energy consumption of the pumping unit.

[0072] Table 1. Comparison of Production Status Before and After Applying Specific Sucker Rod Couplings to Oil Pumping Units

[0073]

[0074] The application results show that the overall production cycle of oil wells has been extended.

[0075] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the implementation methods of the present invention, and should be understood that the scope of protection of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of the present invention.

Claims

1. A wear-resistant sucker rod coupling, characterized in that: Its raw materials include corundum, polyhexamethylene adipamide, multi-component cured polymer and molybdenum disulfide; The raw materials contain the following percentages by mass: 91.5-95% corundum, 3-5% polyhexamethylene adipamide, 0.5-2% multi-component cured polymer, and 1.5% molybdenum disulfide.

2. The wear-resistant sucker rod coupling according to claim 1, characterized in that: The multi-component cured polymer is sebacate dihydrazide.

3. The wear-resistant sucker rod coupling according to claim 1, characterized in that: The wear-resistant sucker rod coupling includes a spindle (1), the central hole of the spindle (1) is threaded to the sucker rod; a rotating anti-friction body (2) is connected to the middle of the outer wall of the spindle; The outer working surface of the rotating anti-wear body (2) is a circular arc surface; the curvature of the circular arc surface of the rotating anti-wear body is the same as the curvature of the circular arc surface of the inner wall of the oil pipe.

4. The wear-resistant sucker rod coupling according to claim 3, characterized in that: The mandrel (1) has anti-detachment grooves (3) at both the front and rear ends of its outer wall.

5. The wear-resistant sucker rod coupling according to claim 4, characterized in that: The mandrel has an inner chamfer (5) and an outer chamfer (4) at both ends of the opening; the anti-detachment groove (3) has an outer chamfer (7) at its edge.

6. The wear-resistant sucker rod coupling according to claim 3, characterized in that: Ball bearings (6) are installed at the connection between the rotating anti-friction body and the spindle.

7. A method for preparing a wear-resistant sucker rod coupling according to any one of claims 1-6, characterized in that: Includes the following steps: 1) Prepare raw materials and pre-treat them; 2) Melt-blend the components of the raw materials: Polyhexamethylene adipamide is heated to a molten state, while corundum, molybdenum disulfide, and multi-component curable polymer powder are preheated to an appropriate temperature and then mixed in proportion. During the mixing process, the pressure is 0.1 MPa to 1 MPa. The mixed material is then processed by melt blending or injection molding. 3) Molding and curing The molten blended material is injected into a mold, and the desired shape is obtained by compression molding or injection molding. During the molding process, temperature and pressure are controlled to ensure that the material is fully cured and forms a uniform structure; 4) Post-processing The shaped material is annealed and gradually cooled to room temperature. During the cooling process, a pressure of 0.1 MPa to 1 MPa is maintained to prevent deformation.

8. The method for preparing the wear-resistant sucker rod coupling according to claim 7, characterized in that: During the melt blending stage, polyhexamethylene adipamide is heated to a molten state temperature of 259-267°C; at the same time, corundum, molybdenum disulfide and multi-component cured polymer powder are preheated to a temperature of 100-200°C.

9. The method for preparing the wear-resistant sucker rod coupling according to claim 7, characterized in that: During the molding process, the temperature is controlled at 220-240℃ and the pressure is controlled at 0.1-1MPa.

10. The method for preparing the wear-resistant sucker rod coupling according to claim 7, characterized in that: Pretreatment of the raw material components; specifically including: For the corundum in the raw materials, a silane coupling agent is used to polish the surface of the corundum to improve its compatibility with the polymer matrix; for the polyhexamethylene adipamide in the raw materials, a drying process is performed.

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