Preparation method of conjoined three-way drill rod joint

Abstract

The invention discloses a preparation method of a conjoined three-way drill rod joint, belongs to the field of mechanical manufacturing, and aims to solve the problems of hidden danger of stress concentration, insufficient torsional property, poor sealing performance and the like of the existing welded joint and realize integral forming of the joint through an integral weldless structure. The preparation method comprises the steps of forging stock hot forging forming, tempering treatment, transverse edge rough turning, axial inner hole drilling, transverse edge outer circle finish turning, bypass connector milling, thread finish turning and thermal refining. The drill rod joint prepared through the method has a uniform and compact metal structure, a continuously fiberized metal structure is formed in the drill rod joint, the defect risk caused by welding seams is eliminated, and the torsion resistance and the fatigue resistance are remarkably improved; the structure is weldless, and the sealing performance is better; threaded connection precision is high, and safety and reliability of the connector and equipment are ensured. The preparation method is simple and efficient, the production cost is remarkably reduced, meanwhile, the method adapts to complex working conditions such as deep wells and ultra-deep wells, the service life of products is greatly prolonged, and the safety of the products is greatly improved.

Description

Technical Field

[0001] The present invention belongs to a machining preparation method in the field of mechanical manufacturing, and specifically, the present invention relates to a machining preparation method in the field of petroleum machinery manufacturing, in particular to a preparation method of a conjoined three-way drill pipe joint. Background Art

[0002] Under existing technical conditions, conventional oil drilling depths reach several thousand meters, and in some geologically complex areas, the depth of oil drilling even exceeds 10,000 meters. The standard length of oil drill pipes is about 10 meters, and the upper and lower drill pipes are connected by threads. During the drilling stage, the drill pipe must not only transmit extremely large torque, but also bear the accumulated weight formed by the drill pipe joints. In addition to requiring a reasonable connection structure and tight sealing, the rods that bear heavy loads must also have sufficient mechanical strength and rigidity.

[0003] In drilling projects, in order to facilitate the monitoring of downhole conditions, a three-way drill pipe joint with a bypass interface is usually connected in series in a group of drill pipes. The three-way drill pipe joint is mainly used to install a pressure gauge or pressure sensor. The bypass interface of the existing three-way drill pipe joint is usually located on the pipe wall, and an integrated connection is achieved by welding. Prior art CN111119753B discloses an automatic plug-in spiral drill pipe, in which the drill pipe male joint and the drill pipe female joint are respectively connected to the two ends of the rod body by welding. The advantages of this welding method are simple process and low manufacturing cost. However, this welding structure has the following defects and shortcomings: Stress concentration hazards: The welded structure formed by this welding process will cause stress concentration problems at the joints, and the quality of the connection depends entirely on the quality of the weld fusion. Once there are tiny defects in the weld, such as pores, inclusions or cracks, they may expand rapidly during the drilling process, seriously affecting the reliability of the product.

[0004] Insufficient torsional resistance: Due to the difference in material strength between the welded part and the parent material, and the weakening of the heat-affected zone in the weld area, the welded joint is more susceptible to fatigue failure when subjected to high torque and vibration loads during drilling.

[0005] Limited sealing performance: The bypass interface is connected to the pipe wall by welding. The welding area is easily corroded by external high-pressure fluid, resulting in reduced sealing performance and increased risk of downhole leakage.

[0006] Low safety: In high-depth drilling operations, the three-way drill pipe joint is subjected to more stringent loads and environmental conditions. Since the three-way drill pipe joint is subjected to the same torque as the matching drill pipe during the drilling process, if there are defects in the connecting welds, when subjected to high torque during the drilling process, once the welded joint fails, it may cause a rod breakage accident, resulting in huge economic losses and engineering risks.

[0007] In view of the above problems, the existing technology is difficult to meet the high requirements of joint strength, safety and sealing performance for deep well and ultra-deep well drilling. Therefore, it is urgent for technical personnel to develop a method for preparing a weld-free, integrated structure of a three-way drill pipe joint, which can fundamentally eliminate the hidden danger of stress concentration caused by welding and significantly improve the product's torsion resistance, sealing performance and safety and reliability. Summary of the invention

[0008] The present invention mainly aims at the problem of potential safety hazards in the three-way drill pipe joint prepared by the prior art, and proposes a method for preparing a conjoined three-way drill pipe joint. The three-way drill pipe joint prepared by the method has an integral structure, and since the product has no weld, there is no potential stress concentration problem. In addition, the three-way drill pipe joint with an integral structure also improves the connection quality and sealing performance of the bypass interface.

[0009] The present invention achieves the technical objectives through the following technical solutions.

[0010] A method for preparing a conjoined three-way drill pipe joint comprises the following steps: S1. Hot forging of forging blank: hot forging is used to form the forging blank. The forging blank is T-shaped, with the horizontal side longer than the vertical side. The cross-sections of the horizontal and vertical sides are both polygonal structures. A machining allowance is reserved on one side of the outer wall of the forging blank. S2. Tempering treatment: placing the forging blank as a whole in a furnace for tempering treatment; S3, rough turning of horizontal edge: first insert one end of the horizontal edge of the forging blank into the four-jaw chuck equipped with the horizontal lathe, and after correction, roughly turn the exposed end of the horizontal edge of the forging blank into a cylindrical shape, leaving enough machining allowance on one side, and then turn around and use the same process to machine the other end of the horizontal edge into a cylindrical shape; S4. Axial drilling of inner hole: Install the rough-turned forging blank on the workbench of the deep hole drilling machine, clamp the two ends of the horizontal side of the forging blank with a four-guar chuck and a center frame respectively, and after position correction, axially drill the inner hole to the size according to the calibrated hole diameter; S5. Finish turning the outer circle of the horizontal edge: Use the centers at both ends of the lathe to position and support the inner holes of the horizontal edge of the forging blank, and finish turning the outer circle of the horizontal edge on both sides of the longitudinal edge of the forging blank to the calibrated size; S6. Milling the bypass interface: Then, the forging blank is placed on the workbench of the turning and milling machining center as the positioning reference, and the bypass interface and its shoulder are machined according to the calibrated size at the upper end surface of the longitudinal edge; S7, thread finishing: first clamp one end of the horizontal side of the forging blank with the three-jaw chuck equipped with the horizontal lathe, and finish turning the internal thread at the other end of the horizontal side after correction. After completion, remove the forging blank, and then turn around and finish turn the remaining section of external thread on the horizontal side of the forging blank using the internal thread as the positioning reference; S8, quenching and tempering treatment: the manufactured joint three-way drill pipe joint is sent into the furnace as a whole for quenching and tempering treatment.

[0011] As a further improvement, in step S1, the cross-sections of the horizontal and vertical sides of the forging blank are in an even-numbered polygonal structure, preferably with four sides forming a hexagon or an octagon.

[0012] As a further improvement, in step S1, a machining allowance of 8-12 mm is reserved on each side of the outer wall of the horizontal and vertical sides of the forging blank.

[0013] As a further improvement, when the outer circle of the horizontal side of the forging blank is rough turned in step S3, the forging blank is fixed and corrected by a four-jaw chuck equipped with a horizontal lathe. After the outer circle of the horizontal side of the forging blank is rough turned, a machining allowance of 4-6 mm is reserved on one side to provide a uniform machining surface for subsequent machining.

[0014] As a further improvement, in step S4, when both ends of the forging blank are clamped and fixed by the four-jaw chuck and the center frame respectively, the drill bit is continuously cooled by coolant to prevent thermal deformation during the processing.

[0015] As a further improvement, in step S6, the shoulder of the bypass interface is formed by one-time milling, and its shape is circular or polygonal. The bypass interface is formed by one-time milling, and the weld-free structure avoids stress concentration and corrosion hazards at the interface position. At the same time, the processing accuracy of the interface is higher, which can better meet the installation requirements of equipment such as pressure sensors. The bypass interface quality is optimized, with strong adaptability and high reliability.

[0016] As a further improvement, in step S7, the thread processing adopts a combination of internal thread and external thread, wherein the internal thread is used for connecting the drill rod with supporting equipment, and the external thread is used for connecting with other drill rods.

[0017] As a further improvement plan, the tempering treatment adopts a heating temperature of 850℃-900℃ and air cooling after high-temperature tempering to improve the torsional strength and fatigue resistance of the drill pipe joint, so that the product can withstand high-intensity operation requirements under complex working conditions for a long time, adapt to complex working conditions, and significantly extend its service life.

[0018] As a further improvement, the forging blank uses carbon steel or low alloy steel as the material, uses carbon steel or low alloy steel as the raw material, and combines the hot forging process. The present invention makes full use of the joint material during the processing process to ensure that the forging blank has good plasticity and toughness during the hot forging process. After heat treatment, the overall strength and toughness of the product are evenly distributed, further improving the mechanical properties of the joint. The material utilization rate is high and the product strength is uniform.

[0019] As a further improvement, the shape and processing method of the forging blank eliminates the hidden dangers of welds and stress concentration caused by welds, thereby significantly improving the safety of the product.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention adopts an integral weld-free structure to prepare a three-way drill pipe joint, which fundamentally eliminates the stress concentration risk that may be caused by the welding structure. Compared with the joints that rely on welding technology in the prior art, the integrally formed drill pipe joint has higher reliability during the drilling process, effectively avoiding the risk of broken rod accidents caused by weld defects, eliminating the stress concentration risk, and this structural feature doubles the safety of the product.

[0021] The drill pipe joint prepared by the present invention has a uniform and dense metal structure through hot forging and quenching and tempering treatment, and a continuous fibrous metal structure is formed inside. This improvement significantly improves the fatigue resistance of the joint under high torque conditions, greatly reduces the possibility of fracture during use, and significantly improves the torsion resistance.

[0022] The three-way drill pipe joint prepared by the present invention realizes a high-quality bypass interface and a threaded connection structure through precision machining, avoids the problem that the bypass interface is easily corroded by high-pressure fluid in the welding method, and improves the sealing performance between the joint and the supporting equipment, ensuring the safety of underground operations, and improving the sealing performance and connection quality. The present invention adopts the manufacturing process of integral hot forging and finishing, which avoids the complex procedures and quality control difficulties in the welding process and reduces the workload of subsequent repair and inspection. The integral forming process not only improves the processing efficiency, but also reduces the production cost. The product blank is easy to forge and form, simplifies the preparation process, and improves production efficiency.

[0023] The process method and product of the present invention are not only suitable for deep well and ultra-deep well drilling scenarios, but can also maintain excellent performance in complex operating environments with high torque, high pressure and high vibration, significantly improving the safety and reliability of the overall drilling system.

[0024] After repeated hot forging, the product blank of the present invention makes the metal structure of the material more dense and more fibrous, thereby increasing the mechanical strength of the product and also facilitating the improvement of the connection quality and sealing performance of the bypass interface. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a three-dimensional schematic diagram of the combined three-way drill pipe joint of the present invention.

[0026] Figure 2 It is a three-dimensional schematic diagram of the shape of the forging blank made in this embodiment.

[0027] Figure 3 yes Figure 2 The shown figure is a three-dimensional schematic diagram of the outer circles at both ends of the horizontal edge of the blank after rough turning.

[0028] Figure 4 is Figure 3 A three-dimensional schematic diagram of drilling an axial through hole on the basis shown.

[0029] Figure 5 is Figure 4 A three-dimensional schematic diagram of a bypass interface milled out on the basis shown. DETAILED DESCRIPTION

[0030] The following is a further detailed description of the method for preparing a conjoined three-way drill pipe joint of the present invention in conjunction with the accompanying drawings and embodiments. However, this embodiment is not a limitation of the present invention, but is only a specific description of the principle and technical solution of the present invention. Example 1

[0031] This embodiment adopts the following steps to prepare the conjoined three-way drill pipe joint: Step S1: Hot forging of forging blank

[0032] Low alloy steel is selected as the material, and the blank is forged into a T-shaped forging blank by hot forging. Its horizontal side is longer than the vertical side, and the cross-sections of the horizontal side and the vertical side are both even-numbered polygonal structures. Figure 2 As shown, the horizontal and vertical cross-sections of the forging blank are quadrilaterals, and a processing allowance of 8-12mm is reserved on one side of the outer wall of the forging blank. In this embodiment, an 8-inch drill rod is matched, so the specification is centered, so a processing allowance of 10mm is reserved on one side of the outer wall for subsequent processing.

[0033] Step S2: Tempering

[0034] The forging blank is placed in a tempering furnace as a whole, and is treated at a constant temperature of 600° C. for 2 hours and then slowly cooled to eliminate the residual stress generated during the forging process and improve the toughness and processing stability of the forging blank.

[0035] Step S3: Rough cutting of horizontal edges

[0036] First, insert one end of the horizontal edge of the forging blank into the four-jaw chuck equipped with the horizontal lathe. After correction, the exposed end of the horizontal edge of the forging blank is roughly turned into a cylindrical shape, and a processing allowance of 4-6mm is reserved on one side of the outer wall. After completion, turn around and process the other end of the horizontal edge of the forging blank into a cylindrical shape using the same process to ensure that the coaxiality error of both ends after rough turning does not exceed 0.1mm. In this implementation, a processing allowance of 5mm is reserved on one side of the outer wall.

[0037] Step S4: Axial drilling of inner hole

[0038] The rough-turned forging blank is mounted on the workbench of the deep hole drilling machine. The two ends of the horizontal side of the forging blank are clamped and fixed by the four-jaw chuck and the center frame respectively. After position correction, the inner hole is axially drilled to the size according to the calibrated hole diameter. The drill bit is continuously cooled by coolant, and the through hole is drilled axially to the specified depth according to the calibrated hole diameter to ensure that the inner hole wall is smooth and has no thermal deformation.

[0039] Step S5: Finish turning the outer circle of the horizontal edge

[0040] Place the inner holes at both ends of the horizontal side of the forging billet against the tops at both ends of the lathe, use the lathe as the positioning reference, and fine-turn the horizontal side outer circles on both sides of the longitudinal side of the forging billet to the calibrated size to ensure that the dimensional accuracy reaches ±0.02mm. The coaxiality is controlled within 0.05mm to improve the matching accuracy of subsequent connections.

[0041] Step S6: Milling bypass interface

[0042] The forging blank is installed on the turning and milling composite machining center, and the forging blank is placed with the working table of the turning and milling machining center as the positioning reference, and the longitudinal edge facing upward end surface is used as the positioning reference, and the bypass interface and shoulder are processed according to the calibrated size. In this embodiment, the shoulder shape of the bypass interface is designed to be circular, which is formed by one-time milling, and the interface size accuracy is ±0.01mm. This structure can directly install the pressure sensor to avoid stress concentration and sealing problems caused by welding.

[0043] Step S7: Thread finishing

[0044] Place one end of the horizontal edge of the forging blank into the three-jaw chuck of the horizontal lathe, and after calibration, fine-turn the internal thread of the other end of the horizontal edge to the calibrated size. After completion, remove the forging blank, turn around and fine-turn the remaining external thread of the horizontal edge of the forging blank using the internal thread as the positioning reference. This embodiment adopts the international standard thread specification, and the thread surface roughness is controlled within Ra1.6 to ensure the sealing and high reliability of the connecting parts.

[0045] Step S8: Tempering treatment

[0046] The processed joint three-way drill pipe joint is put into the tempering furnace as a whole, heated to a constant temperature of 850℃, kept warm for 1 hour and then taken out of the furnace, and quickly cooled by air cooling. Then it is subjected to high-temperature tempering treatment, the temperature is controlled at 580℃, kept warm for 2 hours and then taken out of the furnace. The tempering treatment significantly improves the torsional strength and fatigue resistance of the joint, enabling it to withstand the high-intensity operation requirements of complex working conditions.

[0047] Example 2

[0048] On the basis of Example 1, the horizontal and vertical cross-sections of the forging blank are octagonal in structure, and the remaining process steps and parameters are the same.

[0049] The shoulder shape of the bypass interface is processed into a polygon to meet the connection requirements of different types of equipment.

[0050] The quenching and tempering temperature is 900℃, and high temperature tempering is performed after air cooling. After this improvement, the mechanical properties of the joint are further improved, especially the reliability in high vibration and high pressure environments is significantly enhanced.

[0051] The forging blank made by the process of the present invention is hot forged and is shaped like a T-shaped member. The biggest structural feature of the forging is that there is no weld inside. Therefore, there is no weld inside the joint three-way drill pipe joint prepared by this forging. This technical measure directly eliminates the hidden dangers such as stress concentration caused by the weld from the structure, so that the safety of the prepared joint three-way drill pipe joint is significantly enhanced. On the other hand, after repeated forging, the metal structure of the material becomes denser and more fibrous, thereby significantly increasing the mechanical strength of the product and improving the connection quality and sealing performance of the bypass interface.

[0052] Although the cost of forging billet forming in the present invention is slightly higher than that of welding forming in the prior art, the overall quality of the manufactured three-way drill pipe joint is much better than that of the prior art. In the oil drilling industry, production safety is the first assessment indicator and is exclusive. Once a rod break accident occurs in a drilling project, it is a serious accident, and its losses are calculated in tens of millions of yuan. Therefore, the slightly increased production cost of the forging billet used in the present invention is negligible compared with its improvement in product drilling safety.

[0053] Example 3: Product testing and performance verification In order to verify the performance of the conjoined three-way drill pipe joint prepared by the present invention, the following tests were performed on the samples: 1. Mechanical properties test Test method: Standard tensile test and torque test equipment are used to test the tensile strength, torsional strength and hardness of the joint samples. The test data are as follows: in conclusion: The test results show that the mechanical properties of the combined three-way drill pipe joint are better than those of traditional welding products and meet the high standards of the industry.

[0054] Tests show that the tensile strength, torsional strength and hardness of the product of the present invention are significantly better than those of joints prepared by traditional welding methods, and the mechanical properties are evenly distributed without weak areas caused by stress concentration.

[0055] 2. Fatigue performance test Test method: Under simulated high torque conditions, 150% of the design rated load was applied to the joint sample for a cyclic loading test, and the fatigue life was recorded.

[0056] Test conditions: Rated torque: 8,000 Nm Applied load: 12,000 Nm (150% rated load) Cycle times: 1 million times Test data: in conclusion: Fatigue tests show that the joint operates stably for a long time under high-intensity working conditions, its lifespan is significantly higher than the industry standard, and it has excellent anti-fatigue performance.

[0057] Fatigue tests were carried out under simulated high torque conditions, and the results showed that the fatigue life of the joint was greatly improved, and it could withstand high-intensity operating requirements under complex working conditions for a long time.

[0058] 3. Sealing performance test Test method: Install a pressure sensor on the bypass interface, test the sealing performance under high pressure conditions, and observe the leakage.

[0059] Test conditions: Test medium: hydraulic oil Test pressure: 50 MPa (rated pressure) and 75 MPa (overload pressure) Duration: 30 minutes Test data: in conclusion: Tests show that the bypass interface has no leakage under high pressure conditions, and its sealing performance fully meets the requirements of the oil drilling industry.

[0060] After connecting the bypass interface to the pressure sensor, a sealing test was carried out under high pressure conditions. The results showed that there was no leakage in the interface and the sealing performance was excellent.

[0061] 4. Nondestructive Testing Detection method: Ultrasonic testing and magnetic particle testing are used to inspect the internal and external defects of the joint samples, and the defect detection results are recorded.

[0062] Test data: in conclusion: The results of non-destructive testing showed that no defects such as cracks and pores were found inside and on the surface of the joint, verifying the excellent processing quality of the product.

[0063] Through ultrasonic and magnetic particle testing, no defects such as cracks and pores were found inside or on the surface of the product, verifying the superiority of the overall structure.

[0064] The combined three-way drill pipe joint prepared according to the above method shows excellent performance under high torque and complex working conditions. The weld-free structure formed by integral hot forging effectively avoids stress concentration and fracture problems caused by welding defects; the metal structure after quenching and tempering is denser and fibrous, which helps to significantly improve the mechanical strength and fatigue resistance of the joint; the finely machined bypass interface and threaded connection ensure the sealing of the joint and its compatibility with other equipment. Overall, the product of the present invention fully meets the high strength and high reliability requirements of deep well and ultra-deep well drilling operations.

[0065] The foregoing is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features of the invention described herein.

Claims

1. A method for preparing a conjoined three-way drill pipe joint, characterized in that: The following steps are involved: S1. Hot forging of forging blank: hot forging is used to form the forging blank. The forging blank is T-shaped, with the horizontal side longer than the vertical side. The cross-sections of the horizontal and vertical sides are both polygonal structures. A machining allowance is reserved on one side of the outer wall of the forging blank. S2. Tempering treatment: placing the forging blank as a whole in a furnace for tempering treatment; S3, rough turning of horizontal edge: first insert one end of the horizontal edge of the forging blank into the four-jaw chuck equipped with the horizontal lathe, and after correction, roughly turn the exposed end of the horizontal edge of the forging blank into a cylindrical shape, leaving enough machining allowance on one side, and then turn around and use the same process to machine the other end of the horizontal edge into a cylindrical shape; S4. Axial drilling of inner hole: Install the rough-turned forging blank on the workbench of the deep hole drilling machine, clamp the two ends of the horizontal side of the forging blank with a four-guar chuck and a center frame respectively, and after position correction, axially drill the inner hole to the size according to the calibrated hole diameter; S5. Finish turning the outer circle of the horizontal edge: Use the centers at both ends of the lathe to position and support the inner holes of the horizontal edge of the forging blank, and finish turning the outer circle of the horizontal edge on both sides of the longitudinal edge of the forging blank to the calibrated size; S6. Milling the bypass interface: Then, the forging blank is placed on the workbench of the turning and milling machining center as the positioning reference, and the bypass interface and its shoulder are machined according to the calibrated size at the upper end surface of the longitudinal edge; S7, thread finishing: first clamp one end of the horizontal side of the forging blank with the three-jaw chuck equipped with the horizontal lathe, and finish turning the internal thread at the other end of the horizontal side after correction. After completion, remove the forging blank, and then turn around and finish turn the remaining section of external thread on the horizontal side of the forging blank using the internal thread as the positioning reference; S8, quenching and tempering treatment: the manufactured joint three-way drill pipe joint is sent into the furnace as a whole for quenching and tempering treatment.

2. The method for preparing a conjoined three-way drill pipe joint according to claim 1, characterized in that: In the step S1, the cross-sections of the horizontal and vertical sides of the forging blank are in an even-numbered polygonal structure.

3. The method for preparing a conjoined three-way drill pipe joint according to claim 1, characterized in that: In the step S1, a machining allowance of 8-12 mm is reserved on each side of the outer wall of the horizontal and vertical sides of the forging blank.

4. The method for preparing a conjoined three-way drill pipe joint according to claim 1, characterized in that: When the outer circle of the horizontal side of the forging blank is rough turned in the step S3, the forging blank is fixed and corrected by a four-jaw chuck equipped with a horizontal lathe, and a machining allowance of 4-6 mm is reserved on one side after the outer circle of the horizontal side of the forging blank on both sides is rough turned.

5. The method for preparing the conjoined three-way drill pipe joint according to claim 1, characterized in that: In the step S4, the drill bit is continuously cooled by coolant when both ends of the forging blank are clamped and fixed by the four-jaw chuck and the center frame respectively.

6. The method for preparing the conjoined three-way drill pipe joint according to claim 1, characterized in that: In step S6, the shoulder of the bypass interface is formed by one-time milling, and its shape is circular or polygonal.

7. The method for preparing the conjoined three-way drill pipe joint according to claim 1, characterized in that: In step S7, the thread processing adopts a combination of internal thread and external thread, wherein the internal thread is used for connecting the drill rod with supporting equipment, and the external thread is used for connecting with other drill rods.

8. The method for preparing the conjoined three-way drill pipe joint according to claim 1, characterized in that: The quenching and tempering treatment adopts a heating temperature of 850° C.-900° C., and air cooling is performed after high-temperature tempering to improve the torsional strength and fatigue resistance of the drill pipe joint.

9. The method for preparing the conjoined three-way drill pipe joint according to claim 1, characterized in that: The forging blank is made of carbon steel or low alloy steel.

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