A method for preparing a conjoined tee drill pipe joint

Abstract

The present invention discloses a method for preparing a combined three-way drill pipe joint, which belongs to the field of mechanical manufacturing. In order to solve the problems of stress concentration, insufficient torsional resistance, poor sealing performance and the like existing in existing welded joints, the integrated forming of the joint is realized through an overall weld-free structure. The preparation method includes hot forging of the forging blank, tempering treatment, rough turning of the horizontal edge, axial drilling of the inner hole, fine turning of the horizontal edge outer circle, milling of the bypass interface, fine turning of the thread, and tempering treatment. The drill pipe joint prepared by the present invention has a uniform and dense metal structure, and a continuously fibrous metal structure is formed inside, which eliminates the risk of defects caused by welds and significantly improves torsional resistance and fatigue resistance; the structure has no welds and better sealing; the threaded connection has high precision, ensuring the safety and reliability of the joint and the equipment. The present preparation method is simple and efficient, significantly reduces production costs, and is adaptable to complex working conditions such as deep wells and ultra-deep wells, greatly improving the service life and safety of the product.

Description

Technical Field

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

[0002] Under current technological conditions, conventional oil drilling reaches depths of several thousand meters, and in some geologically complex areas, the depth even exceeds 10,000 meters. The standard length of an oil drill pipe is approximately 10 meters, with the upper and lower sections connected by threads. During drilling, the drill pipe must transmit extremely high torque while also bearing the cumulative weight of the connected sections. Such heavy-duty rods require not only a rational connection structure and tight sealing, but also sufficient mechanical strength and rigidity.

[0003] In drilling projects, in order to facilitate monitoring of downhole working 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 is welded to achieve an integrated connection. The 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:

[0004] Stress Concentration Hazards: This welding process creates stress concentration at the joints, and the quality of the connection depends entirely on the quality of the weld fusion. Any small defects in the weld, such as pores, inclusions, or cracks, can rapidly expand during drilling, seriously affecting product reliability.

[0005] Insufficient torsional resistance: Due to the difference in material strength between the welded area 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.

[0006] 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 a decrease in sealing performance and an increased risk of downhole leakage.

[0007] Lower safety: In high-depth drilling operations, the three-way drill pipe joint is subject 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 weld joint fails, it may cause a rod breakage accident, resulting in huge economic losses and engineering risks.

[0008] Given these issues, existing technologies struggle to meet the stringent requirements for joint strength, safety, and sealing performance in deep and ultra-deep well drilling. Therefore, it is imperative for those skilled in the art to develop a method for fabricating a weld-free, integrated, three-way drill pipe joint. This method would fundamentally eliminate the stress concentration risks associated with welding and significantly improve the product's torsional resistance, sealing performance, and safety and reliability. Summary of the Invention

[0009] This invention addresses the safety risks associated with conventional three-way drill pipe joints and proposes a method for manufacturing a one-piece three-way drill pipe joint. This method results in a one-piece three-way drill pipe joint with no welds, eliminating the potential stress concentration risk. Furthermore, this one-piece three-way drill pipe joint improves the connection quality and sealing performance of the bypass interface.

[0010] The present invention achieves the technical objectives through the following technical solutions.

[0011] A method for preparing a conjoined tee drill pipe joint comprises the following steps:

[0012] 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 polygonal structures. A machining allowance is reserved on one side of the outer wall of the forging blank.

[0013] S2. Tempering treatment: placing the forging blank as a whole in a furnace for tempering treatment;

[0014] S3. Rough turning of horizontal edge: First, insert one end of the horizontal edge of the forging blank into the four-jaw chuck of the horizontal lathe. After correction, rough turn the exposed end of the horizontal edge of the forging blank into a cylindrical shape, leaving sufficient machining allowance on one side. Then turn around and use the same process to machine the other end of the horizontal edge into a cylindrical shape.

[0015] S4. Axial drilling of inner hole: After rough turning, the 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 by a four-guar chuck and a center stand respectively. After position correction, the inner hole is axially drilled to the size according to the calibrated hole diameter;

[0016] 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 hole 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;

[0017] S6. Milling the bypass interface: Then, the forging blank is placed on the workbench of the turning and milling center as the positioning reference, and the bypass interface and its shoulder are machined according to the calibrated dimensions at the upper end face of the longitudinal edge;

[0018] S7, thread finishing: First, use the three-jaw chuck equipped with the horizontal lathe to clamp one end of the horizontal edge of the forging blank. After correction, finish turning the internal thread at the other end of the horizontal edge. After completion, remove the forging blank, then turn around and use the internal thread as the positioning reference to finish turning the remaining external thread on the horizontal edge of the forging blank.

[0019] S8. Quenching and tempering treatment: The manufactured three-way drill pipe joint is sent into the furnace as a whole for quenching and tempering treatment.

[0020] As a further improvement, the cross-sections of the horizontal and vertical sides of the forging blank in step S1 are in an even-numbered polygonal structure, preferably with four sides forming a hexagon or an octagon.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] As a further improvement, in step S6, the shoulder of the bypass interface is formed by a single milling operation, and its shape is circular or polygonal. This single milling operation eliminates weld seams, avoiding stress concentration and corrosion risks at the interface. Furthermore, the interface achieves higher machining precision, better meeting the installation requirements of equipment such as pressure sensors. This optimizes the bypass interface's quality, ensuring greater adaptability and reliability.

[0025] As a further improvement, in step S7, the thread processing adopts a combination of internal and external threads, wherein the internal thread is used to connect the drill rod with supporting equipment, and the external thread is used to connect with other drill rods.

[0026] As a further improvement, the quenching and tempering treatment uses a heating temperature of 850°C-900°C and air cooling after high-temperature tempering to improve the torsional strength and fatigue resistance of the drill pipe joint, enabling the product to withstand high-intensity operation requirements under complex working conditions for a long time, adapt to complex working conditions, and significantly extend its service life.

[0027] As a further improvement, the present invention utilizes carbon steel or low-alloy steel as the forging blank, employing a hot forging process. This fully utilizes the joint material during processing, ensuring the blank exhibits excellent plasticity and toughness during hot forging. After heat treatment, the overall strength and toughness of the product are evenly distributed, further enhancing the mechanical properties of the joint. This results in high material utilization and uniform product strength.

[0028] As a further improvement, the shape and processing method of the forging blank eliminate the hidden dangers of welds and the stress concentration caused by welds, thereby significantly improving the safety of the product.

[0029] Compared with the prior art, the present invention has the following beneficial technical effects:

[0030] This invention utilizes a seamless, weld-free structure to create a one-piece, three-way drill pipe joint, fundamentally eliminating the potential stress concentration risks associated with welded structures. Compared to existing joints that rely on welding, this integrally formed joint offers greater reliability during drilling, effectively avoiding the risk of pipe breakage due to weld defects and eliminating stress concentration risks. This structural feature significantly enhances product safety.

[0031] Through hot forging and tempering, the drill rod joint produced in this invention has a uniform and dense metal structure with a continuous, fibrous metal structure formed within. This improvement significantly improves the joint's fatigue resistance under high torque conditions, significantly reduces the likelihood of fracture during use, and significantly enhances torsional resistance.

[0032] The three-way drill pipe joint prepared by the present invention realizes a high-quality bypass interface and threaded connection structure through precision machining, avoiding the problem that the bypass interface is easily corroded by high-pressure fluid in the welding method, and at the same time improves the sealing between the joint and the supporting equipment, ensuring the safety of underground operations, and improving the sealing performance and connection quality.

[0033] This invention utilizes a single-piece hot forging and finishing process, eliminating the complex welding steps and quality control challenges, and reducing the workload for subsequent repair and inspection. This integrated forming process not only improves processing efficiency but also reduces production costs. The product blanks are easily forged and prepared, streamlining the production process and improving production efficiency.

[0034] The process method and products 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.

[0035] After repeated hot forging, the blank of the product of the present invention makes the metal structure of the material denser and more fibrous, thereby increasing the mechanical strength of the product and also facilitating improvement of the connection quality and sealing performance of the bypass interface. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a three-dimensional schematic diagram of the conjoined three-way drill pipe joint of the present invention.

[0037] Figure 2 It is a three-dimensional schematic diagram of the shape of the forging blank made in this embodiment.

[0038] Figure 3 yes Figure 2 The shown figure is a three-dimensional schematic diagram of the outer circles at both ends of the rough-turned horizontal edges of the blank.

[0039] Figure 4 is Figure 3 A three-dimensional schematic diagram of drilling an axial through hole on the basis shown.

[0040] Figure 5 is Figure 4 A three-dimensional schematic diagram of a bypass interface milled out on the basis shown. DETAILED DESCRIPTION

[0041] The following is a further detailed description of the method for preparing a conjoined tee drill pipe joint of the present invention in conjunction with the accompanying drawings and examples. However, this example is not intended to limit the present invention, but is merely a specific illustration of the principles and technical solutions of the present invention. Example 1

[0042] This embodiment adopts the following steps to prepare the conjoined three-way drill pipe joint:

[0043] Step S1: Hot forging of forging blank

[0044] 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 and vertical sides are both even polygonal structures. Figure 2 As shown, the horizontal and vertical cross-sections of the forging blank are quadrilaterals. A machining allowance of 8-12mm is reserved on each side of the outer wall of the forging blank. In this implementation, an 8-inch drill rod is used, so the specification is medium, so a machining allowance of 10mm is reserved on each side of the outer wall to facilitate subsequent processing.

[0045] Step S2: Tempering

[0046] 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.

[0047] Step S3: Rough turning of horizontal edges

[0048] First, insert one end of the forging blank's horizontal edge into the four-jaw chuck of the horizontal lathe. After alignment, rough-turn the exposed end of the forging blank into a cylindrical shape, leaving a 4-6mm machining allowance on each side of the outer wall. Once completed, turn the machine around and use the same process to machine the other end of the forging blank into a cylindrical shape, ensuring that the coaxiality error after rough-turning does not exceed 0.1mm. In this implementation, a 5mm machining allowance is left on each side of the outer wall.

[0049] Step S4: Axial drilling of the inner hole

[0050] The rough-turned forging blank is mounted on the deep-hole drilling machine's workbench. The blank's transverse ends are clamped in place using a four-jaw chuck and a center rest. After position correction, the inner hole is axially drilled to the specified depth according to the calibrated diameter. Coolant is used to continuously cool the drill bit. The inner hole is drilled axially to the specified depth according to the calibrated diameter, ensuring a smooth inner hole wall with no thermal deformation.

[0051] Step S5: Finish turning the outer circle of the horizontal edge

[0052] Place the inner holes at both ends of the forging blank's horizontal edge against the centers of the lathe. Using the lathe as a positioning reference, precision lathe the outer diameters of the horizontal edges on both sides of the forging blank's longitudinal edge to the calibrated dimensions, ensuring a dimensional accuracy of ±0.02mm. Coaxiality is controlled within 0.05mm to improve the precision of subsequent connections.

[0053] Step S6: Milling bypass interface

[0054] The forging blank is mounted on a turning-milling machine, positioned using the turning-milling machine's worktable as a reference. The bypass port and shoulder are machined to the specified dimensions, using the longitudinal edge facing upward as a reference. In this embodiment, the bypass port shoulder is designed to be circular and milled in a single pass, achieving a dimensional accuracy of ±0.01mm. This structure allows for direct installation of pressure sensors, avoiding stress concentration and sealing issues caused by welding.

[0055] Step S7: Thread finishing

[0056] One end of the forging blank's horizontal edge is loaded into the three-jaw chuck of a horizontal lathe. After calibration, the internal threads at the other end of the edge are finish-turned to the specified dimensions. Upon completion, the forging blank is removed and the remaining external threads on the edge are finish-turned, using the internal threads as a reference. This embodiment utilizes international standard thread specifications, with a surface roughness of Ra1.6 or less, ensuring a leak-tight connection and high reliability.

[0057] Step S8: Tempering treatment

[0058] The finished, one-piece, three-way drill pipe joint is placed in a tempering furnace, heated to a constant temperature of 850°C, held for one hour, and then removed from the furnace for rapid cooling via air cooling. This is followed by a high-temperature tempering treatment at 580°C, held for two hours, and removed from the furnace. This tempering treatment significantly improves the joint's torsional strength and fatigue resistance, enabling it to withstand the high-intensity demands of complex working conditions.

[0059] Example 2

[0060] On the basis of Example 1, the horizontal and vertical cross-sections of the forging blank are octagonal structures, and the remaining process steps and parameters are the same.

[0061] The shoulder shape of the bypass interface is processed into a polygon to meet the connection requirements of different types of equipment.

[0062] The quenching and tempering temperature is 900°C, followed by air cooling and high-temperature tempering. This improvement further enhances the mechanical properties of the joint, especially its reliability in high-vibration and high-pressure environments.

[0063] The forging blank produced by the process described in this invention is hot-forged and shaped like a T-shaped member. The forging's most significant structural feature is the absence of internal welds. Consequently, the three-way drill pipe joint produced using this forging also contains no welds. This technical measure directly eliminates the potential stress concentration risks associated with welds, significantly enhancing the safety of the resulting three-way drill pipe joint. Furthermore, repeated forging of the forging blank results in a denser and more fibrous metallurgy, significantly increasing the mechanical strength of the product and improving the connection quality and sealing performance of the bypass interface.

[0064] Although the forging process cost slightly more than welding in the prior art, the overall quality of the resulting three-way drill pipe joint is significantly better than that of the prior art. In the oil drilling industry, safety is paramount and a top priority. A broken rod accident during a drilling project is a serious hazard, with losses estimated in the tens of millions of yuan. Therefore, the slight increase in production cost associated with the use of forging in the present invention is negligible compared to the improvement in drilling safety.

[0065] Example 3: Product Testing and Performance Verification

[0066] To verify the performance of the conjoined tee drill pipe joint prepared by the present invention, the following tests were performed on the sample:

[0067] 1. Mechanical properties test

[0068] Test method:

[0069] Standard tensile testing and torque testing equipment are used to test the tensile strength, torsional strength and hardness of the joint samples. The test data are as follows:

[0070] in conclusion:

[0071] The test results show that the mechanical properties of the combined three-way drill pipe joint are better than those of traditional welded products and meet the high standards of the industry.

[0072] 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.

[0073] 2. Fatigue performance test

[0074] Test method:

[0075] Under simulated high torque conditions, 150% of the design rated load was applied to the joint sample for cyclic loading test, and the fatigue life was recorded.

[0076] Test conditions:

[0077] Rated torque: 8,000 Nm

[0078] Applied load: 12,000 Nm (150% rated load)

[0079] Number of cycles: 1 million times

[0080] Test data:

[0081] in conclusion:

[0082] 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 fatigue resistance.

[0083] Fatigue tests were conducted under simulated high-torque conditions, and the results showed that the fatigue life of the joint was greatly improved, and it can withstand high-intensity operation requirements under complex working conditions for a long time.

[0084] 3. Sealing performance test

[0085] Test method:

[0086] Install a pressure sensor on the bypass interface and test the sealing performance under high pressure conditions to observe leakage.

[0087] Test conditions:

[0088] Test medium: hydraulic oil

[0089] Test pressure: 50 MPa (rated pressure) and 75 MPa (overload pressure)

[0090] Duration: 30 minutes

[0091] Test data:

[0092] in conclusion:

[0093] 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.

[0094] 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.

[0095] 4. Nondestructive Testing

[0096] Detection method:

[0097] 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.

[0098] Test data:

[0099] in conclusion:

[0100] The non-destructive testing results showed that no defects such as cracks and pores were found inside or on the surface of the joint, verifying the excellent processing quality of the product.

[0101] 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.

[0102] The combined three-way drill pipe joint prepared according to the above method exhibits 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 more dense 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 and ultra-deep well drilling operations.

[0103] The foregoing description is intended only to provide specific embodiments of the present invention, which will enable those skilled in the art to understand and implement the present invention. Various modifications to these embodiments will be readily 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 is not intended to be limited to the embodiments shown herein, but is to be construed in the widest manner consistent with the principles and novel features of the invention described herein.

Claims

1. A method for preparing a conjoined tee 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 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 of the horizontal lathe. After correction, rough turn the exposed end of the horizontal edge of the forging blank into a cylindrical shape, leaving sufficient machining allowance on one side. 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: After rough turning, the 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 by a four-guar chuck and a center stand respectively. After position correction, the inner hole is axially drilled 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 hole 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 center as the positioning reference, and the bypass interface and its shoulder are machined according to the calibrated dimensions at the upper end face of the longitudinal edge; S7, thread finishing: First, use the three-jaw chuck equipped with the horizontal lathe to clamp one end of the horizontal edge of the forging blank. After correction, finish turning the internal thread at the other end of the horizontal edge. After completion, remove the forging blank, then turn around and use the internal thread as the positioning reference to finish turning the remaining external thread on the horizontal edge of the forging blank. S8. Quenching and tempering treatment: The manufactured 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 tee 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 tee drill pipe joint according to claim 1, characterized in that: 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.

4. The method for preparing a conjoined tee 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 step S3, the forging blank is fixed and corrected by a four-jaw chuck configured on the horizontal lathe. After the outer circle of the horizontal side of the forging blank on both sides is rough turned, a machining allowance of 4-6 mm is reserved on one side.

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

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

8. The method for preparing the conjoined tee drill pipe joint according to claim 1, characterized in that: The quenching and tempering treatment adopts a heating temperature of 850° C. to 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 tee 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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