Weldless integral high-strength feeding drill rod and preparation method thereof

Abstract

The invention discloses a weldless integral high-strength feeding drill rod and a preparation method thereof. The drill rod comprises a female connector, an elevator groove, a thick-wall slip clamping section, a drill rod pipe body and a male connector which are integrally formed and have the same inner diameter. The drill rod is manufactured by integrally machining a solid bar or a thick-wall pipe body. The yield strength of the drill rod pipe body, the yield strength of the thick-wall slip clamping section and the yield strength of the elevator groove are 135 ksi-180 ksi, and the yield strength of the male connector and the yield strength of the female connector are 130 ksi-150 ksi; the outer diameter of the thick-wall slip clamping section is larger than that of the drill rod pipe body; the outer diameter of the elevator groove is smaller than that of the clamping section of the thick-wall slip; the outer diameter of the elevator groove is not smaller than that of the drill rod pipe body. The outer diameter of the connector does not need to be obviously increased, meanwhile, enough elevator lifting capacity is guaranteed, and the problem of poor structure performance caused by friction welding seams and welding area heat treatment is avoided. Complicated welding, postweld heat treatment and other procedures are omitted, the possibility that a weld joint serves as a performance weak link is avoided, higher comprehensive tensile mechanical performance is achieved, and the method is suitable for well drilling application of extra-deep wells, ocean deep wells and the like.

Description

Technical Field

[0001] This invention relates to the technical field of drill pipe and drill pipe manufacturing, and in particular to a seamless, integral, high-strength feed drill pipe and its preparation method. Background Technology

[0002] When conducting ultra-deep land drilling or ultra-deep water drilling operations, drill pipes are used to lower and send in the casing. As the drilling depth continues to increase, the problems of excessively long and heavy casing strings become more and more prominent. The weight of the casing string may exceed 900 tons. If we also consider the complex lifting and lowering operations, the drill pipes need to have a higher load-bearing capacity to ensure safety. Conventional drilling pipes obviously cannot meet this requirement. Therefore, there is an urgent need to develop large-size, thick-walled, and high-strength drill pipes.

[0003] As the outer diameter and wall thickness of the drill pipe continue to increase, the corresponding weld neck size will also be larger, which will lead to the following two problems: (1) In order to meet the lifting capacity of the jack, the outer diameter of the drill pipe joint can only be passively increased further. For example, for a 6-5 / 8in, 20.65mm thick 165ksi high-strength drill pipe, the outer diameter of the drill pipe weld neck is designed to be 185mm, and the outer diameter of the drill pipe joint needs to reach more than 230mm to provide sufficient lifting capacity. Such a large joint outer diameter will bring many difficulties in both the manufacturing process and the drilling use. (2) With the increase of the weld neck size, the weld neck wall thickness may reach or exceed 40mm. It is difficult to achieve uniform heating or quenching and cooling of the inner and outer walls by using medium frequency induction heating to temper the weld area, resulting in a large difference in the microstructure and properties of the inner and outer walls. In addition, due to the quenching temperature gradient, a heat-affected zone inevitably exists in the welding area. The microstructure of this area is a low-strength duplex microstructure, resulting in low strength, poor toughness, and poor fatigue performance in the welding area. Therefore, the welded area will become the weak point in the tensile strength of the entire drill string, and may fracture and fail in the event of a complex accident.

[0004] Therefore, for large-size, thick-walled, high-strength drill pipes, two major challenges urgently need to be addressed: first, how to achieve a good match between the tensile strength of the pipe body and the lifting capacity of the hoist through reasonable structural and strength design; and second, how to effectively avoid the differences in the microstructure and properties of the inner and outer walls and the low strength in the two-phase region caused by existing friction welding and weld zone heat treatment processes during the manufacturing process.

[0005] A search revealed several technical solutions for "landing drill pipes" and "integral drill pipes" in publicly available patent documents. CN201320542945.7 discloses a deep-water landing drill pipe that uses friction welding to connect the drill pipe body, thick-walled pipe section, male drill pipe connector, and female drill pipe connector. Its main purpose is to improve the drill pipe's resistance to slip crushing by increasing the thick-walled pipe section; however, it does not consider the lifting capacity of the chuck and does not provide a treatment plan for the weld area after friction welding. CN201620450654.9 discloses a deep-water landing drill pipe with a chuck groove and slip clamping section, but does not provide a corresponding manufacturing method. CN101259580A discloses a processing technology for an integral drill pipe, where the drill pipe connector and drill pipe body are connected using a male-female thread. While this avoids welding and subsequent processing, the process is more complex, and the number of threaded connections on the drill pipe doubles, increasing the likelihood of failure. CN200920048132.6 discloses an integral drill pipe, which aims to solve the problem of poor performance in the welded part and the adjacent area. The joint is formed at the thickened part at both ends of the pipe body, but no feasible implementation steps are given.

[0006] In summary, currently available patent documents do not provide feasible solutions to the aforementioned two problems. Summary of the Invention

[0007] The purpose of this invention is to provide a seamless, integral, high-strength drill pipe and its manufacturing method, overcoming the shortcomings of the existing technology. This invention ensures sufficient lifting capacity without significantly increasing the joint's outer diameter, while avoiding the poor microstructure and properties caused by friction welds and weld zone heat treatment. It not only eliminates the complex welding and post-weld heat treatment processes but also avoids the possibility of welds being weak points, and possesses higher overall tensile mechanical properties, making it suitable for drilling applications in ultra-deep wells and deep-water offshore wells.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] A seamless, integral, high-strength feed drill pipe, characterized in that it comprises an integrally formed female connector with the same inner diameter, a lifting groove, a thick-walled slip clamping section, a drill pipe body, and a male connector, wherein the drill pipe is integrally machined from solid bar stock or a thick-walled tube body.

[0010] The yield strength of the drill pipe body, the thick-walled slip clamping section, and the lifting slot is 135ksi-180ksi, and the yield strength of the male and female joints is 130ksi-150ksi.

[0011] The outer diameter of the thick-walled slip clamping section is larger than the outer diameter of the drill pipe body;

[0012] The outer diameter of the hanging slot is smaller than the outer diameter of the thick-walled clamping section;

[0013] The outer diameter of the hanging slot is not less than the outer diameter of the drill pipe body.

[0014] The seamless integral high-strength feed drill pipe is characterized in that: the outer diameter of the drill pipe body is 139.7mm-177.8mm and the wall thickness is 12.7mm-38.1mm.

[0015] The seamless integral high-strength feed drill pipe is characterized in that the length of the thick-walled slip clamping section is 800mm-1200mm.

[0016] The seamless integral high-strength feed drill pipe is characterized in that the length of the lifting slot is >400mm.

[0017] A method for manufacturing a seamless, integral, high-strength feed drill pipe as described above, characterized by comprising the following steps:

[0018] First, rough machine the blank outline of the drill pipe, then perform overall heat treatment, then perform local heat treatment on the joint area, and finally machine the joint thread.

[0019] The method for preparing the seamless, integral, high-strength feed drill pipe is characterized by the following specific steps:

[0020] S1. Rough machining of drill pipe blank outline: Machining the blank outline of the drill pipe on machining equipment, leaving finishing allowance at the threaded parts of the male and female joints of the drill pipe and the lifting slot;

[0021] S2. Overall heat treatment: The drill pipe blank is heat-treated in a walking beam continuous heating furnace. The quenching temperature is 860-920℃ and the holding time is 60-90min. The quenching cooling is achieved by internal spraying and external water spraying. The tempering temperature is 570℃-620℃ and the holding time is 90-150min. After taking it out of the furnace, it is hot straightened at a temperature above 300℃ and then air-cooled to room temperature on a cooling bed.

[0022] S3. Hanger slot machining: Machining the outer diameter of the hanger slot on a machining equipment;

[0023] S4. Local heat treatment of joint area: The male and female joints at both ends, including the pliers area and the threaded area to be processed, are subjected to local heating and tempering heat treatment at a tempering temperature of 600℃-660℃. After holding at the temperature for a certain time, they are air-cooled to room temperature.

[0024] S5. Joint thread finishing: Finish machining of the threads and shoulder surfaces of the male and female joints to obtain the final finished product of the drill pipe shape.

[0025] The method for preparing a seamless, integral, high-strength feed drill pipe is characterized in that: the drill pipe female connector and the slip groove in step S1 are machined into a structure with cylindrical ends and a conical middle during rough machining. That is, a conical slope is used to transition between the female connector and the slip clamping section (the location of the slip groove to be machined later), which facilitates the movement of the drill pipe on the conveyor roller conveyor during heat treatment.

[0026] The beneficial effects of this invention also include:

[0027] 1. By setting a smaller outer diameter lifting groove near the shoulder of the female connector lifting clamp, the contact area between the shoulder of the lifting clamp and the lifting clamp can be effectively increased without increasing the outer diameter of the connector, thereby increasing the lifting capacity of the lifting clamp.

[0028] 2. By using solid bar stock or thick-walled tube for integral processing, a seamless integral drill pipe can be obtained, avoiding the possibility of weld seams as weak points in performance and improving the safety factor of the drill pipe in service. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of a seamless, integral, high-strength drill pipe blank in the middle state according to the present invention.

[0030] Figure 2 This is a schematic diagram of a seamless, integral, high-strength drill pipe intermediate blank state according to the present invention.

[0031] Figure 3 This is a schematic diagram of a finished seamless integral high-strength feed drill pipe according to the present invention;

[0032] Figure 4 This is a schematic diagram of a finished drill pipe using a conventional design, shown in the comparison diagram.

[0033] In the diagram: 1-Female connector; 2-Cone transition zone; 2'-Lifting slot; 3-Thick-walled slip clamping section; 4-Drill pipe body; 5-Male connector; 6-First weld (thick-walled slip clamping section - female connector); 7-Second weld (drill pipe body - thick-walled slip clamping section); 8-Third weld (drill pipe body - male connector). Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings. The drawings are for illustrative purposes only and should not be construed as limiting the scope of this patent.

[0035] like Figure 3 As shown, the present invention discloses a seamless integral high-strength feed drill pipe, which includes an integrally formed female connector 1, a lifting groove 2', a thick-walled slip clamping section 3, a drill pipe body 4, and a male connector 5. The drill pipe is integrally processed from solid bar stock or a thick-walled tube body.

[0036] The yield strength of the drill pipe body 4, the thick-walled slip clamping section 3, and the lifting slot 2' is 135ksi-180ksi, and the yield strength of the male connector 5 and the female connector 1 is 130ksi-150ksi.

[0037] The outer diameter of the thick-walled slip clamping section 3 is larger than the outer diameter of the drill pipe body 4.

[0038] The outer diameter of the hanging slot 2' is smaller than the outer diameter of the thick-walled clamping section 3.

[0039] The outer diameter of the hanging slot 2' is not less than the outer diameter of the drill pipe body 4.

[0040] In this invention, the outer diameter of the drill pipe body 4 is 139.7mm-177.8mm, and the wall thickness is 12.7mm-38.1mm.

[0041] In this invention, the length of the thick-walled clamping section 3 is 800mm-1200mm.

[0042] In this invention, the length of the hanging slot 2' is greater than 400mm.

[0043] A method for manufacturing a seamless, integral, high-strength feed drill pipe as described above, characterized by comprising the following steps:

[0044] First, rough machine the blank outline of the drill pipe, then perform overall heat treatment, then perform local heat treatment on the joint area, and finally machine the joint thread.

[0045] The specific steps are as follows:

[0046] S1. Rough machining of drill pipe blank outline: The rough outline of the drill pipe blank is machined on a machining equipment, leaving finishing allowances at the male and female joint threads and the hanger groove; such as Figure 1 .

[0047] S2. Overall heat treatment: The drill pipe blank is heat-treated in a walking beam continuous heating furnace. The quenching temperature is 860-920℃ and the holding time is 60-90min. The quenching cooling is achieved by internal spraying and external water spraying. The tempering temperature is 570℃-620℃ and the holding time is 90-150min. After taking it out of the furnace, it is hot straightened at a temperature above 300℃ and then air-cooled to room temperature on a cooling bed.

[0048] S3. Hanger slot machining: Machining the outer diameter of the hanger slot on a machining equipment; such as... Figure 2 .

[0049] S4. Local heat treatment of joint area: The male and female joints at both ends, including the pliers area and the threaded area to be processed, are subjected to local heating and tempering heat treatment at a tempering temperature of 600℃-660℃. After holding at the temperature for a certain period of time, they are air-cooled to room temperature.

[0050] S5. Joint Thread Finishing: Finish machining of the threads and shoulder surfaces of the male and female joints to obtain the final finished product with the correct drill pipe shape, such as... Figure 3 .

[0051] In step S1, the drill pipe female connector and the lifting slot are machined into a structure with cylindrical ends and a conical middle during rough machining.

[0052] Example

[0053] A seamless, integral, high-strength feed drill pipe, which is a thick-walled drill pipe with an outer diameter of 168.3 mm, a wall thickness of 27 mm, and a steel grade of 165 ksi, includes a female drill pipe joint, a lifting slot, a thick-walled slip clamping section, a drill pipe body, and a male drill pipe joint.

[0054] The drill pipe is made of thick-walled seamless tube with an outer diameter of 219mm, a wall thickness of about 55mm, and a length of 9.5-10m.

[0055] Specifically, it is prepared using the following methods:

[0056] S1. Rough machining of drill pipe blank outline: The above-mentioned thick-walled seamless tube is machined into the blank outline of the drill pipe on a lathe. The inner diameter is machined to 114.3mm, the outer diameter of the tube body is machined to 168.3mm, the outer diameter of the thick-walled slip clamping section is machined to 176.2mm, the length of the thick-walled slip clamping section is 1000mm, and the outer diameter of the male and female connectors is machined to 215.9mm. The thread area to be machined is machined into a tapered surface and a certain allowance is reserved for the thread finishing.

[0057] Furthermore, a tapered transition is used between the female connector and the slip clamping section to facilitate the drill rod's movement on the conveyor rollers during subsequent heat treatment. The length of the tapered transition zone is 450mm. A schematic diagram of the intermediate blank state of the drill rod after rough machining is shown below. Figure 1 As shown.

[0058] S2. Overall heat treatment: The drill pipe blank is heat-treated in a walking beam continuous heating furnace. The quenching temperature is 860-920℃ and the holding time is 60-90min. The quenching cooling is achieved by internal spraying and external water spraying. The tempering temperature is 570℃-620℃ and the holding time is 90-150min. After taking it out of the furnace, it is hot straightened at a temperature above 300℃ and then air-cooled to room temperature on a cooling bed.

[0059] S3. Finishing the hanger groove: Machining the outer diameter of the hanger groove to 168.3mm on a lathe. A schematic diagram of the drill rod intermediate blank after the hanger groove machining is shown below. Figure 2 As shown.

[0060] S4. Localized heat treatment of joint areas: For both male and female joints, including the clamp area and the threaded area to be machined, localized induction heating and tempering heat treatment is performed at a tempering temperature of 600℃-660℃ and a holding time of 240s-480s, followed by air cooling to room temperature. Samples are taken as required to analyze the mechanical properties of the pipe body and joints.

[0061] S5. Joint Thread Finishing: On a CNC threading lathe, the threads and shoulder surfaces of the male and female joints are machined. The final drill pipe product looks like... Figure 3 As shown.

[0062] Comparative Example

[0063] The following uses the production process of a thick-walled drill pipe with an outer diameter of 168.3 mm and a steel grade of 165 ksi, produced using conventional design and methods, as a comparative example.

[0064] The drill pipe body is made of thick-walled seamless tube with an outer diameter of 168.3mm, a wall thickness of 20.65mm, and a length of 7-8m; the thick-walled slip clamping section is made of thick-walled seamless tube with an outer diameter of 176.2mm and a wall thickness of 30.95mm, and is cut to a length of 1000mm; the drill pipe joint is made of hot-rolled annealed thick-walled tube with an outer diameter of 220mm and a wall thickness of 55mm, and the male joint is cut to a length of 500mm, and the female joint is cut to a length of 1000mm.

[0065] S1. Thickening of the drill pipe end: The end of the drill pipe is heated to 1000℃-1500℃ in stages and thickened in two stages. The thickening is done both inside and outside, with an outer diameter of 183-185mm and an inner diameter of 104-105mm.

[0066] S2. Heat Treatment of Drill Pipe Body: The drill pipe body is sequentially sent to a quenching and tempering furnace for heat treatment. The furnace type is a walking beam furnace. The quenching temperature is 860℃-900℃, and the holding time is 60-90min. Quenching cooling is achieved through internal spraying and external water spraying. After quenching, the pipe body temperature and the temperature of the thickened end are both below 90℃. The tempering temperature is 570℃-620℃, and the holding time is 90-150min. After exiting the furnace, hot straightening is performed when the pipe body temperature is above 300℃, followed by air cooling to room temperature. The inner and outer diameters of the ends are then precision machined, with the outer diameter machined to 176.2mm and the inner diameter to 114.3mm. Non-destructive testing is performed on the drill pipe.

[0067] S3. Drill Pipe Joint Machining: The male and female joint raw material pipes, cut to length, are first rough-machined into joint blanks, with a certain amount of finishing allowance reserved for the inner and outer diameters and the threaded area to be machined. Then, quenching and tempering heat treatment is performed: quenching temperature 880℃-940℃, holding time 120-240min, water cooling to room temperature; tempering temperature 600-660℃, holding time 120-240min, the performance after heat treatment reaches 135ksi. Then, the inner and outer diameters (outer diameter to 215.9mm, inner diameter to 114.3mm), threads, shoulder surface, and weld neck are finished.

[0068] S4. Welding of the thick-walled slip clamping section and male / female connectors onto the drill pipe body: One thickened end of the drill pipe body is friction-welded to the thick-walled slip clamping section, and the other thickened end is welded to the drill pipe male connector. Then, the female connector is welded to the other end of the thick-walled slip clamping section. After each welding, the inner flash is punched off; the outer flash is annealed and then machined. Subsequently, the weld area is quenched and tempered using medium-frequency induction heating: quenching temperature 880℃-920℃, holding time 180-360s, quenching cooling using external PAG quenching liquid and internal compressed air spraying; tempering temperature 620-660℃, holding time 180-360s, then air-cooled to room temperature. The inner and outer surfaces of the weld area are then ground smooth and flat using a grinding wheel or belt. The final drill pipe product is as follows: Figure 4 As shown.

[0069] For the drill pipes obtained in the above embodiments and comparative examples, the load-bearing capacity of each part was calculated based on material strength and dimensions, and the results are shown in Table 1:

[0070] Table 1. Calculation results of bearing capacity of various parts of the drill pipe obtained by conventional methods and the present invention.

[0071]

[0072]

[0073] Note: (1) When calculating the allowable suspended weight of the clamping section of the slip, the friction coefficient is taken as 0.08, the slip length is 22in, and the slip back angle is 14°.

[0074] (2) When calculating the lifting capacity of the lifting clamp, the clamp strength is selected as 130ksi.

[0075] The main differences between the two are as follows:

[0076] a. The embodiment uses a thick-walled tube for integral processing. Compared with the comparative example, its tube wall thickness is greater, and therefore the tensile load of the tube is higher.

[0077] b. In the hanging groove section, although the wall thickness of the comparative example is larger, its material strength is the same as that of the joint, which is 135ksi. In the embodiment, the hanging groove section is the same as that of the pipe body, which is 165ksi. Therefore, the hanging groove of the embodiment can withstand a higher tensile load.

[0078] c. In the comparative example, since conventional friction welding is used to connect the various parts and post-weld heat treatment is performed by induction heating, a heat-affected zone is inevitably present, resulting in low strength (generally below 115 ksi), and the corresponding weld tensile load is only 1123 t; while in the embodiment, since there is no weld, the material strength except for the joint reaches 165 ksi, so the tensile load at the corresponding position can reach 1638 t.

[0079] d. Finally, regarding the lifting capacity of the lifting clamp, the comparative example suffers from a small contact area of ​​the lifting clamp, which makes the lifting capacity a weakness in the overall tensile strength of the drill pipe; while the embodiment significantly increases the lifting capacity of the lifting clamp by adding a lifting clamp slot, which is about 200t higher than that of the comparative example.

[0080] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. All equivalent changes and modifications made within the scope of the claims of this invention should be considered within the technical scope of this invention.

Claims

1. A seamless, integral, high-strength feed drill pipe, characterized in that: It includes an integrally formed female connector (1) with the same inner diameter, a lifting groove (2'), a thick-walled slip clamping section (3), a drill pipe body (4), and a male connector (5). The drill pipe is made of solid bar stock or a thick-walled tube body. The yield strength of the drill pipe body (4), the thick-walled slip clamping section (3), and the lifting slot (2') is 135ksi-180ksi, and the yield strength of the male connector (5) and the female connector (1) is 130ksi-150ksi. The outer diameter of the thick-walled slip clamping section (3) is larger than the outer diameter of the drill pipe body (4); The outer diameter of the hanging slot (2') is smaller than the outer diameter of the thick-walled clamping section (3); The outer diameter of the hanging slot (2') is not less than the outer diameter of the drill pipe body (4).

2. The seamless integral high-strength feed drill pipe according to claim 1, characterized in that: The outer diameter of the drill pipe body (4) is 139.7mm-177.8mm, and the wall thickness is 12.7mm-38.1mm.

3. The seamless integral high-strength feed drill pipe according to claim 1, characterized in that: The length of the thick-walled slip clamping section (3) is 800mm-1200mm.

4. The seamless integral high-strength feed drill pipe according to claim 1, characterized in that: The length of the hanging slot (2') is >400mm.

5. A method for preparing a seamless, integral, high-strength feed drill pipe as described in any one of claims 1-4, characterized in that: It includes the following steps: First, rough machine the blank outline of the drill pipe, then perform overall heat treatment, then perform local heat treatment on the joint area, and finally machine the joint thread.

6. The method for preparing a seamless, integral, high-strength feed drill pipe according to claim 5, characterized in that: The specific steps are as follows: S1. Rough machining of drill pipe blank outline: Machining the blank outline of the drill pipe on machining equipment, leaving finishing allowance at the threaded parts of the male and female joints of the drill pipe and the lifting slot; S2. Overall heat treatment: The drill pipe blank is heat-treated in a walking beam continuous heating furnace. The quenching temperature is 860-920℃ and the holding time is 60-90min. The quenching cooling is achieved by internal spraying and external water spraying. The tempering temperature is 570℃-620℃ and the holding time is 90-150min. After taking it out of the furnace, it is hot straightened at a temperature above 300℃ and then air-cooled to room temperature on a cooling bed. S3. Hanger slot machining: Machining the outer diameter of the hanger slot on a machining equipment; S4. Local heat treatment of joint area: The male and female joints at both ends, including the pliers area and the threaded area to be processed, are subjected to local heating and tempering heat treatment at a tempering temperature of 600℃-660℃. After holding at the temperature for a certain time, they are air-cooled to room temperature. S5. Joint thread finishing: Finish machining of the threads and shoulder surfaces of the male and female joints to obtain the final product of the drill pipe shape.

7. The method for preparing a seamless, integral, high-strength feed drill pipe according to claim 6, characterized in that: In step S1, the drill pipe female connector and the lifting slot are machined into a structure with cylindrical ends and a conical middle during rough machining.

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