A high-strength grade fully sulfur-resistant drill pipe and its processing method

Abstract

The present application discloses a high-strength grade all-sulfur-resistant drill pipe and its processing method. On the one hand, the present application provides a processing method for a high-strength hydrogen sulfide corrosion-resistant drill pipe, including the following steps: S1. Friction welding is used to weld the drill pipe body and the drill pipe joint into a formed body; S2. After welding stops, under the maintenance of the high-temperature waste heat generated by welding, the flash in the welding zone is punched; S3. The drill pipe with external flash is subjected to normalizing treatment of the drill pipe welding zone; S4. The drill pipe welding zone is air-cooled to below 300 °C, and the external flash in the welding zone is removed by turning to obtain a drill pipe semi-finished product; S5. Quenching treatment is carried out on the drill pipe welding zone of the drill pipe semi-finished product; S6. Then tempering treatment is carried out on the drill pipe welding zone of the drill pipe semi-finished product to obtain a high-strength hydrogen sulfide corrosion-resistant drill pipe finished product. On the other hand, the present application also provides a high-strength hydrogen sulfide corrosion-resistant drill pipe obtained by the above processing method. The present application can effectively change the hardness microstructure and mechanical properties of the welding zone, facilitate processing, and can effectively improve the overall hydrogen sulfide stress corrosion resistance of the drill pipe.

Description

Technical Field

[0001] This application relates to the technical field of oil and gas well drill pipes, and particularly relates to a high-strength grade fully sulfur-resistant drill pipe and a processing method thereof. Background Art

[0002] A drill pipe is a drilling tool used to connect surface equipment of a drilling rig and drilling and grinding equipment or bottom hole devices located at the bottom of a well, and is an important component of drilling equipment. An oil and gas well drill pipe mainly consists of a drill pipe body and a drill pipe joint, and the two are fixedly connected by welding. Since most of the oil and gas fields in China are acidic oil and gas fields with a relatively high H2S content, and the H2S content in some highly acidic oil and gas fields exceeds 10%, metal components are extremely prone to cracking due to H2S stress corrosion when operating in the above-mentioned acidic oil and gas fields. Therefore, there is a large demand for drill pipes resistant to hydrogen sulfide corrosion in China.

[0003] According to existing research results, when the hardness of the oil well pipe material is less than 26RC, it is not necessary to conduct an H2S stress corrosion performance evaluation, and low-hardness metal pipe fittings will not crack due to H2S stress corrosion. Therefore, hardness control is the key to affecting the resistance of materials to hydrogen sulfide stress corrosion (SSC). Currently, most of the drill pipes on the market are formed by friction welding of a drill pipe body and a drill pipe joint. Generally, the hardness of the weld line fusion zone is relatively high after heat treatment of the drill pipe weld area. The current API standard has strict requirements for drill pipe bodies and joints of different steel grades, and the hardness requirement for the weld area of all steel grade drill pipes does not exceed 37HRC; however, in the production process, it is difficult to control the hardness of the weld area of high steel grade drill pipes above 105ksi.

[0004] At present, the delivery standard for drill pipes in the market only stipulates that drill pipes resistant to hydrogen sulfide corrosion with a yield strength of 75 ksi to 105 ksi are required to evaluate the SSC performance of the pipe body and joints under a certain stress according to the uniaxial tensile test (Method A, Solution A) in NACE TM0177 "Test Method for Resistance of Metals to Sulfide Stress Cracking and Stress Corrosion in a Hydrogen Sulfide Environment". Among them, the loading stress for the pipe body is 85% SMYS, and the loading stress for the joints is 65% SMYS. However, the current market delivery standard does not require the SSC performance of the drill pipe welds. For drill pipes resistant to hydrogen sulfide corrosion that need to be used in more severe environments, the mechanical properties and safety factor design requirements are higher than those of ordinary drill pipes. In recent years, relevant international standards have recommended evaluating the SSC performance of the weld area of drill pipes resistant to hydrogen sulfide corrosion with a yield strength of 75 ksi to 105 ksi. For example, the API 5DP-2020 standard requires the weld to be subjected to an uniaxial tensile test (Method A, Solution D) according to the NACE TM0177 standard, with a loading stress of 80% SMYS; the ISO11961-2018 standard requires the weld to be subjected to an uniaxial tensile test (Method A, Solution A) according to the NACE TM0177 standard, with a loading stress of 60% SMYS, but there are no technical requirements for drill pipes resistant to hydrogen sulfide corrosion with higher grades such as 115 ksi, 120 ksi, 125 ksi, and 135 ksi applicable to ultra-deep wells and extended reach horizontal wells.

[0005] Based on the changing market demands in this field, it is urgent to solve the problem in the prior art that it is difficult to control the hardness of the drill pipe weld area. Summary of the Invention

[0006] To solve at least one of the above technical problems, a processing method is developed that can effectively change the hardness microstructure and mechanical properties of the weld area, is easy to process, and can effectively improve the overall hydrogen sulfide stress corrosion resistance of the drill pipe. The present application provides a high-strength grade fully sulfur-resistant drill pipe and its processing method.

[0007] On the one hand, the present application provides a processing method for a high-strength hydrogen sulfide corrosion-resistant drill pipe, including the following steps:

[0008] S1. Weld the drill pipe body and the drill pipe joint into a shape by inertial friction welding, forming a drill pipe weld area, as well as flash inside and outside the weld area.

[0009] S2. After the welding in step S1 stops, under the maintenance of the high-temperature waste heat generated by the welding, punch the flash inside the weld area to obtain a drill pipe with flash outside.

[0010] S3. Subject the drill pipe with flash outside obtained in step S2 to normalizing treatment of the drill pipe weld area. Heat the drill pipe weld area to 860 - 920 °C within 50 - 70 s and keep it warm for 80 - 100 s.

[0011] S4. Air-cool the drill pipe welding zone of the drill pipe with external flash obtained in step S3 after normalizing to below 300°C, and turn to remove the external flash of the welding zone to obtain a semi-finished drill pipe.

[0012] S5. Quench the drill pipe welding zone of the semi-finished drill pipe obtained in step S4. Heat the drill pipe welding zone to 840 - 900°C, hold for 90 - 110 s, and then adopt a cooling method of external liquid cooling and internal compressed air air-cooling, and cool for 50 - 80 s.

[0013] S6. Temper the drill pipe welding zone of the semi-finished drill pipe quenched in step S5. Heat the drill pipe welding zone to 670 - 710°C, hold for 220 - 240 s, and air-cool to room temperature to obtain a finished high-strength hydrogen sulfide corrosion-resistant drill pipe.

[0014] By adopting the above technical solution, this application designs a processing method for a high-strength hydrogen sulfide corrosion-resistant drill pipe. The heat treatment process steps of flash-on normalizing + turning off the flash + quenching + tempering are adopted after welding, which can effectively change the metallographic structure mainly composed of martensite and other structures generated due to the high temperature of friction welding in the drill pipe welding zone into a metallographic structure mainly composed of pearlite and ferrite, and then carry out quenching + tempering and conditioning treatment, greatly reducing the hardness of the welding zone of the high-grade hydrogen sulfide corrosion-resistant drill pipe, thereby improving the SSC performance of the drill pipe welding zone; in the processing method of this application, the internal flash in the welding zone is immediately cut off after welding, and the external flash of the welding zone is removed by turning after normalizing, effectively solving the problem of difficult processing caused by the high hardness and brittleness of the external flash in the drill pipe welding zone in the prior art, not only effectively reducing the machining difficulty, but also greatly improving the machining accuracy and the yield rate; in the processing method of this application, through specific heat treatment steps, the metallographic structure uniformity and stability of the drill pipe welding zone are improved, effectively solving the problem of tissue and performance inheritance caused by friction welding, effectively improving the problem of abnormal local hardness in the welding zone of the high-grade hydrogen sulfide corrosion-resistant drill pipe, and the temperature range of the heat treatment in this application is wider than that in the prior art, easier to control, without extending the tempering time, subcritical quenching or multiple quenching and tempering, and the production efficiency is also greatly improved.

[0015] Optionally, in step S2, immediately after the welding in step S1 stops, punch and cut the internal flash in the welding zone.

[0016] Optionally, in step S4, air-cool the drill pipe welding zone of the drill pipe with external flash obtained in step S3 after normalizing to below 300°C, and turn to remove the external flash of the welding zone to obtain a semi-finished drill pipe.

[0017] Optionally, in steps S3 - S6, the heating is carried out by an induction heating coil.

[0018] Further optionally, in step S3 during normalizing, the center of the induction heating coil is aligned with the center of the flash outside the welding zone.

[0019] Further optionally, in step S3, for drill pipes with a specification of more than 4 inches, heat to 880 - 920 °C, and for drill pipes with a specification less than 4 inches, heat to 860 - 880 °C.

[0020] Further optionally, in steps S5 and S6 during quenching and tempering, the center of the induction heating coil is aligned with the center of the drill pipe welding zone.

[0021] Further optionally, in step S5, within 60 - 80 s, heat the drill pipe welding zone to 840 - 900 °C.

[0022] Further optionally, in step S5 during quenching cooling, the outside of the drill pipe welding zone is sprayed with a water-soluble PAG medium with a concentration of 12.5% for cooling.

[0023] Further optionally, in step S6, within 60 - 80 s, heat the drill pipe welding zone to 670 - 710 °C.

[0024] On the other hand, the present application provides a high-strength hydrogen sulfide corrosion-resistant drill pipe prepared by the above processing method, including a drill pipe body and a drill pipe joint. The drill pipe body and the drill pipe joint are fixedly connected by friction welding, and a drill pipe welding zone is formed between the drill pipe body and the drill pipe joint. The materials of the drill pipe body and the drill pipe joint are made of steel with a steel grade of 115 - 135 ksi; the strength grade of the drill pipe welding zone (3) reaches above 105 ksi, the metallographic structure is a uniform tempered sorbite structure, the hardness does not exceed 30 HRC, and it has the performance of resisting hydrogen sulfide stress corrosion cracking.

[0025] By adopting the above technical solution, for the high-strength hydrogen sulfide corrosion-resistant drill pipe of the present application, the hardness of both the whole and the local parts can be controlled within 30 HRC. The SSC performance of the whole drill pipe and the SSC performance of the drill pipe welding zone are both excellent. Any part of the drill pipe has the performance of long-term resistance to hydrogen sulfide stress corrosion, can effectively meet the needs of high-acid oil and gas fields in China, and will not be damaged under harsh environments or abnormal loads during deep well operations, greatly reducing the drill pipe replacement frequency, saving costs, and effectively improving the operation efficiency at the same time.

[0026] In summary, the present invention includes at least one of the following beneficial technical effects:

[0027] 1. The present application designs a processing method for high-strength drill pipes resistant to hydrogen sulfide corrosion. By adopting a heat treatment process step of normalizing with flash + quenching + tempering for the drill pipes after welding, it can effectively transform the metallographic structure mainly composed of martensite and other structures generated due to the high temperature of friction welding in the welded area of the drill pipes into a metallographic structure mainly composed of pearlite and ferrite. Then, through quenching and tempering treatment, a tempered sorbite structure with better uniformity and stability is obtained, significantly reducing the hardness of the welded area of the drill pipes, and thus improving the SSC performance of the welded area of the drill pipes.

[0028] 2. The processing method of the present application adopts a machining step of immediately removing the flash inside the welded area after welding and turning to remove the flash outside the welded area after normalizing. After normalizing treatment, the metallographic structure mainly composed of martensite and other structures generated due to the high temperature of friction welding in the welded area of the drill pipes is transformed into a metallographic structure mainly composed of pearlite and ferrite with lower hardness, effectively solving the problem of difficult machining caused by the high hardness and brittleness of the flash outside the welded area of the drill pipes in the prior art. It not only effectively reduces the machining difficulty, but also greatly improves the machining accuracy and the yield rate.

[0029] 3. The processing method of the present application improves the uniformity and stability of the metallographic structure in the welded area of the drill pipes through specific heat treatment steps, effectively solving the problem of tissue and performance inheritance caused by friction welding, effectively improving the problem of abnormal local hardness in the welded area of high-grade drill pipes resistant to hydrogen sulfide corrosion. Moreover, the temperature range of the heat treatment in the present application is wider than that in the prior art, easier to control, without the need to extend the tempering time, subcritical quenching or multiple quenching and tempering, and the production efficiency is also greatly improved.

[0030] 4. For the high-strength drill pipes resistant to hydrogen sulfide corrosion of the present application, the hardness of both the whole and the local parts can be controlled within 30 HRC. The overall SSC performance of the drill pipes and the SSC performance of the welded area of the drill pipes are both excellent. Any part of the drill pipes has the performance of long-term resistance to hydrogen sulfide stress corrosion, can effectively meet the needs of high-acid oil and gas fields in China, and will not be damaged under harsh environments or abnormal loads during deep well operations, greatly reducing the replacement frequency of the drill pipes, saving costs and effectively improving the operation efficiency at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the structure with external flash after friction welding of the drill pipe resistant to hydrogen sulfide corrosion;

[0032] Figure 2 Schematic diagram of the structure after turning the external flash after friction welding of the drill pipe resistant to hydrogen sulfide corrosion;

[0033] Figure 3 Microstructure diagram of the welding heat affected zone after friction welding of the drill pipe resistant to hydrogen sulfide corrosion;

[0034] Figure 4Microstructure diagram of the normalized heat-affected zone of the drill pipe for anti-hydrogen sulfide corrosion after the normalizing treatment in Example 7;

[0035] Figure 5 Microstructure diagram of the drill pipe for anti-hydrogen sulfide corrosion after the quenching + tempering heat treatment in the welding zone of Example 7;

[0036] In the figure: 1, drill pipe body; 2, drill pipe joint; 3, drill pipe welding zone; 4, external flash outside the welding zone. Detailed implementation manners

[0037] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0038] As Figure 1 shown, the present application designs a processing method for a high-strength anti-hydrogen sulfide corrosion drill pipe, including the following steps:

[0039] S1. The drill pipe body 1 and the drill pipe joint 2 are welded and formed by inertial friction welding, a drill pipe welding zone 3 is formed by welding, as well as internal flash in the welding zone and external flash 4 outside the welding zone;

[0040] S2. After the welding in step S1 stops, under the maintenance of the high-temperature waste heat generated by welding, the internal flash in the welding zone is punched to obtain a drill pipe with external flash;

[0041] S3. The drill pipe with external flash obtained in step S2 is subjected to normalizing treatment for the drill pipe welding zone 3. Within 50 - 70 s, the drill pipe welding zone 3 is heated to 860 - 920 °C and held for 80 - 100 s;

[0042] S4. The drill pipe welding zone 3 of the drill pipe with external flash obtained in step S3 after normalizing treatment is air-cooled to below 300 °C, and the external flash 4 outside the welding zone is removed by turning to obtain a drill pipe semi-finished product;

[0043] S5. The drill pipe welding zone 3 of the drill pipe semi-finished product obtained in step S4 is subjected to quenching treatment. The drill pipe welding zone 3 is heated to 840 - 900 °C, held for 90 - 110 s, and then cooled by an external liquid cooling and internal compressed air air-cooling method for 50 - 80 s;

[0044] S6. The drill pipe welding zone 3 of the drill pipe semi-finished product obtained in step S5 after quenching treatment is subjected to tempering treatment. The drill pipe welding zone 3 is heated to 670 - 710 °C, held for 220 - 240 s, and air-cooled to room temperature to obtain a finished high-strength anti-hydrogen sulfide corrosion drill pipe.

[0045] As Figure 2As shown, the high-strength hydrogen sulfide corrosion-resistant drill pipe prepared by the processing method of the high-strength hydrogen sulfide corrosion-resistant drill pipe of the present application includes a drill pipe body 1 and a drill pipe joint 2, which are fixedly connected by friction welding; a drill pipe welding zone 3 is formed between the drill pipe body 1 and the drill pipe joint 2 by the friction welding. After heat treatment, the strength grade of the drill pipe welding zone 3 of the present application reaches above 105 ksi, the metallographic structure is a uniform tempered sorbite structure, and the hardness does not exceed 30 HRC, having the performance of resisting hydrogen sulfide stress corrosion cracking. The materials of the drill pipe body 1 and the drill pipe joint 2 of the present application can adopt any steel with a steel grade of 115 - 135 ksi.

[0046] Before the present application, in the prior art, for improving the SSC performance of the welding area of hydrogen sulfide corrosion-resistant drill pipes, the method of repeated quenching was mostly adopted. Although repeated quenching can effectively reduce the hardness of the welding zone and improve the SSC performance of the welding zone; however, the repeated quenching process is complex, difficult to control, has a high cost, and there are risks such as decarburization and oxidation.

[0047] In addition, it is not easy to remove the welding flash, which is also a major problem in this field. However, the prior art has not paid attention to this problem, resulting in a low yield rate of drill pipe preparation in this field. Currently, the following method is usually adopted to remove the welding flash in this field: after welding, low-temperature annealing at about 650 °C is carried out to eliminate internal stress and reduce the hardness of the external flash, so as to facilitate the turning processing of the external flash. For the removal of the internal flash, a similar method is also adopted in this field. However, by using the above method of low-temperature annealing treatment, the metallographic structure of the welding zone and the flash cannot be changed, the hardness of the flash is reduced limitedly, and its brittleness problem cannot be solved. Therefore, there are still problems such as low turning processing efficiency, large consumption of processing cutting tools, and a high rejection rate.

[0048] After long-term research on the processing of hydrogen sulfide corrosion-resistant drill pipes by the inventors of the present application, it is found that when the hydrogen sulfide corrosion-resistant drill pipe body and the hydrogen sulfide corrosion-resistant drill pipe joint are friction welded, the melting temperature of the welding surface during the welding process can reach above 1200 °C; and after welding, when cooling in room-temperature air, due to the large cooling temperature difference, a large amount of martensite will be generated in the welding heat-affected zone.

[0049] As Figure 3 shown, Figure 3 the micrograph of Figure 3 is the metallographic structure obtained by the inventors of the present application after detecting the metallographic structure of a certain hydrogen sulfide corrosion-resistant drill pipe after welding. It can be seen from Figure 3 that after the hydrogen sulfide corrosion-resistant drill pipe is welded, the welding heat-affected zone contains a relatively high proportion of martensite structure, as well as bainite, troostite and other structures. Such a distribution of the metallographic structure results in a relatively high hardness and large internal stress. The high hardness brought by the high proportion of martensite structure is also the main reason for the abnormally high local hardness of the subsequent welding zone.

[0050] In the prior art, to solve the above problems, there are various heat treatment methods. For example, by reducing the quenching temperature and shortening the quenching holding time during the heat treatment of the welded zone, increasing the tempering temperature and prolonging the tempering holding time, or adopting process methods such as multi-stage low-temperature quenching and multi-stage tempering. Although the above process methods have certain beneficial effects, when quenching at a temperature below Ac3, the microstructure of the welded zone is particularly sensitive to the quenching process; when the tempering temperature reaches above 710 °C, over-tempering is likely to occur when on-site control is not strict; while prolonging the tempering holding time or adopting multi-stage quenching or tempering will seriously affect production efficiency.

[0051] For example, in a Chinese invention patent with the publication number CN113667799A and the invention title of a heat treatment method for improving the sulfur resistance of the welded zone of high-grade sulfur-resistant drill pipes, its technical solution adopts a heat treatment process of three-stage quenching and one-stage tempering. However, this method involves repeated quenching, and the process is extremely complex and difficult to control. It not only affects production efficiency, but also the metallographic structure of the welded zone is mainly tempered sorbite structure + ferrite, and the proportion of ferrite is only above 25%, and the local hardness is still higher than 30HRC. Another example is a Chinese invention patent with the publication number CN113667815A and the invention title of a heat treatment process for the welded zone of sulfur-resistant drill pipes and the drill pipes prepared thereby, which adopts a heat treatment process of two-stage quenching and one-stage tempering. The metallographic structure of the welded zone is also mainly tempered sorbite structure + ferrite, and there is also a problem that the local hardness is higher than 30HRC. In addition, it is very difficult to remove the flash for the above two prior art processes.

[0052] Based on a detailed study of the above problems, the inventor of the present application designed the processing method of the present application, which includes the heat treatment process steps of normalizing + quenching + tempering with flash after welding, adopts a one-stage quenching process, and adopts a specific flash removal step, effectively solving the above problems, and can ensure uniform hardness of the welded zone, and the hardness of the welded zone does not exceed 30HRC.

[0053] The following are the preparation examples of the present application.

[0054] Preparation Example 1

[0055] The processing method of the high-strength hydrogen sulfide corrosion-resistant drill pipe in this preparation example adopts the following steps:

[0056] S1. Inertia friction weld the drill pipe body 1 and the drill pipe joint 2 of the drill pipe to form a welded shape;

[0057] S2. After welding stops, before the temperature of the welded zone 3 of the drill pipe formed by welding drops to 1000 °C, punch the internal flash in the welded zone of the drill pipe to obtain a drill pipe with external flash.

[0058] S3. Send the drill pipe with external flash obtained in step S2 to the induction heating coil for normalizing. Align the center of the induction heating coil with the center of the external flash of the welded zone 4, offset by the drill pipe joint 2. Raise the temperature of the welded zone to 920 °C in 50 s and hold for 100 s.

[0059] S4. Air-cool the drill pipe welded zone 3 of the drill pipe with external flash obtained in step S3 after normalizing to below 300 °C, and turn and remove the external flash of the welded zone 4 to obtain a semi-finished drill pipe.

[0060] S5. Quench the drill pipe welded zone 3 of the semi-finished drill pipe obtained in step S4. Send the semi-finished drill pipe to the induction heating coil. Align the center of the induction heating coil with the center of the drill pipe welded zone 3, offset by the drill pipe joint 2. Raise the temperature of the drill pipe welded zone 3 to 900 °C in 60 s and hold for 110 s. Immediately after heating, quench and cool the drill pipe welded zone 3. Adopt the cooling method of external spraying of cooling oil and internal spraying of compressed air, and the cooling time is 80 s.

[0061] S6. Temper the drill pipe welded zone 3 of the semi-finished drill pipe obtained in step S5 after quenching. Send the semi-finished drill pipe to the induction heating coil. Align the center of the induction heating coil with the center of the drill pipe welded zone 3, offset by the drill pipe joint 2. Raise the temperature of the welded zone to 670 °C in 80 s and hold for 240 s, and then air-cool to room temperature to obtain the high-strength hydrogen sulfide corrosion-resistant drill pipe of this embodiment.

[0062] Preparation Example 2

[0063] The difference between this preparation example and Preparation Example 1 is that in step S2 of this preparation example, immediately after welding stops, the internal flash of the welded zone of the drill pipe is punched.

[0064] Preparation Example 3

[0065] The difference between this preparation example and Preparation Example 2 is that in step S3 of this preparation example, for normalizing, align the center of the induction heating coil with the center of the external flash of the welded zone 4, and raise the temperature of the welded zone to 880 °C in 60 s and hold for 90 s.

[0066] Preparation Example 4

[0067] The difference between this preparation example and Preparation Example 2 is that in step S3 of this preparation example, for normalizing, align the center of the induction heating coil with the center of the external flash of the welded zone 4, and raise the temperature of the welded zone to 860 °C in 70 s and hold for 80 s.

[0068] Preparation Example 5

[0069] The difference between this preparation example and Preparation Example 3 is that in steps S5 and S6 of this preparation example, during quenching and tempering, the center of the induction heating coil is aligned with the center of the drill pipe welded zone.

[0070] In addition, in step S5 of this preparation example, during the quenching treatment, the temperature of the drill pipe welding zone 3 is raised to 880 °C in 70 s and held for 100 s; then, the drill pipe welding zone 3 is immediately quenched and cooled by using an external spray of a water-soluble PAG medium with a concentration of 12.5% and an internal spray of compressed air, and the cooling time is 65 s.

[0071] Preparation Example 6

[0072] The difference between this preparation example and Preparation Example 4 is that in steps S5 and S6 of this preparation example, during the quenching treatment and the tempering treatment, the center of the induction heating coil is aligned with the center of the drill pipe welding zone.

[0073] In addition, in step S5 of this preparation example, during the quenching treatment, the temperature of the drill pipe welding zone 3 is raised to 840 °C in 60 s and held for 90 s; then, the drill pipe welding zone 3 is immediately quenched and cooled by using an external spray of a water-soluble PAG medium with a concentration of 12.5% and an internal spray of compressed air, and the cooling time is 50 s.

[0074] Preparation Example 7

[0075] The difference between this preparation example and Preparation Example 5 is that in step S6 of this preparation example, during the tempering treatment, the temperature of the welding zone is raised to 695 °C in 70 s and held for 230 s.

[0076] Preparation Example 8

[0077] The difference between this preparation example and Preparation Example 6 is that in step S6 of this preparation example, during the tempering treatment, the temperature of the welding zone is raised to 710 °C in 60 s and held for 220 s.

[0078] The following are the examples of the present application.

[0079] For Examples 1 to 8 of the present application, high-strength hydrogen sulfide corrosion-resistant drill pipes with a 4 in specification (welded outer diameter 114.3 mm, welded inner diameter 97.5 mm) are prepared using steel of 120 ksi grade, and are obtained by using the processing methods of Preparation Examples 1 to 8 respectively.

[0080] The following are Examples 9 to 12 of the present application, which respectively prepare high-strength hydrogen sulfide corrosion-resistant drill pipes of different specifications.

[0081] Example 9

[0082] This example uses steel of 135 ksi grade to prepare a high-strength hydrogen sulfide corrosion-resistant drill pipe with a 3.5 in specification (welded outer diameter 98 mm, welded inner diameter 79.3 mm).

[0083] This example is obtained by using the processing method of Preparation Example 8.

[0084] Example 10

[0085] In this example, steel pipes 1 of high-strength hydrogen sulfide corrosion-resistant drill pipes with a 4 in specification (welded outer diameter 114.3 mm, welded inner diameter 97.5 mm) are prepared using steel with a steel grade of 115 ksi; drill pipe joints 2 of high-strength hydrogen sulfide corrosion-resistant drill pipes with a 4 in specification (welded outer diameter 114.3 mm, welded inner diameter 97.5 mm) are prepared using steel with a steel grade of 125 ksi.

[0086] This example is obtained by using the processing method of Preparation Example 7.

[0087] Example 11

[0088] In this example, steel pipes 1 of high-strength hydrogen sulfide corrosion-resistant drill pipes with a 5 in specification (welded outer diameter 130.2 mm, welded inner diameter 111.8 mm) are prepared using steel with a steel grade of 125 ksi; drill pipe joints 2 of high-strength hydrogen sulfide corrosion-resistant drill pipes with a 5 in specification (welded outer diameter 130.2 mm, welded inner diameter 111.8 mm) are prepared using steel with a steel grade of 95 ksi.

[0089] This example is obtained by using the processing method of Preparation Example 5.

[0090] Example 12

[0091] In this example, high-strength hydrogen sulfide corrosion-resistant drill pipes with a 5.5 in specification (welded outer diameter 144.5 mm, welded inner diameter 126.1 mm) are prepared using steel with a steel grade of 125 ksi.

[0092] This example is obtained by using the processing method of Preparation Example 5.

[0093] Comparative Example 1

[0094] In this application, taking the process of Example 1 of the Chinese invention patent with the publication number CN113667799A, high-strength hydrogen sulfide corrosion-resistant drill pipes with a 4 in specification (welded outer diameter 114.3 mm, welded inner diameter 97.5 mm) are prepared using steel with a steel grade of 120 ksi as Comparative Example 1.

[0095] Comparative Example 2

[0096] In this application, taking the process of Example 1 of the Chinese invention patent with the publication number CN113667815A, high-strength hydrogen sulfide corrosion-resistant drill pipes with a 4 in specification (welded outer diameter 114.3 mm, welded inner diameter 97.5 mm) are prepared using steel with a steel grade of 120 ksi as Comparative Example 2.

[0097] Comparative Example 3

[0098] This comparative example uses basically the same preparation process as Example 7 of this application.

[0099] The difference between this comparative example and Example 7 of the present application is that in step S4, a conventional annealing process at 650 °C is adopted.

[0100] Comparative Example 4

[0101] This comparative example adopts substantially the same preparation process as Example 7 of the present application.

[0102] The difference between this comparative example and Example 7 of the present application is that in step S5, during the quenching treatment, the temperature of the drill pipe welding zone 3 is raised to 920 °C in 70 s and held for 100 s.

[0103] Comparative Example 5

[0104] This comparative example adopts substantially the same preparation process as Example 7 of the present application.

[0105] The difference between this comparative example and Example 7 of the present application is that in step S6, during the tempering treatment, the temperature of the welding zone is raised to 655 °C in 70 s and held for 230 s.

[0106] Relevant performance tests are carried out on the high-strength hydrogen sulfide corrosion-resistant drill pipes prepared in Examples 1-12 of the present application and the hydrogen sulfide corrosion-resistant drill pipes prepared in Comparative Examples 1-5. The obtained test results are shown in Tables 1, 2 and 3 below.

[0107] For the hardness test of the drill pipe welding zone 3 of the present application, the test points are set in the following manner:

[0108] That is, one point is randomly taken inside and outside on one side of the drill pipe welding zone 3 where it is located at the drill pipe joint 2, one point is randomly taken inside and outside at the weld of the drill pipe welding zone 3, and one point is randomly taken inside and outside on one side of the drill pipe welding zone 3 where it is located at the drill pipe body 1, and a total of 6 points are used as the test points.

[0109] The SSC performance test of the present application adopts the following method:

[0110] The method for evaluating the sulfur resistance performance of the welding zone adopts the method described in NACE TM0177 standard. The SSC performance is evaluated by the uniaxial tensile stress test of Method A, and the SSC critical stress intensity factor K is tested by the double cantilever beam test of Method D ISSC .

[0111] Table 1 Mechanical property test results of examples and comparative examples of the present invention

[0112]

[0113] It can be seen from the data in Table 1 that the mechanical properties of the high-strength hydrogen sulfide corrosion-resistant drill pipes in Examples 1-8 of this application are all excellent, and are at a similar level to Comparative Example 1. All mechanical property parameters exceed the specified properties of the relevant standards for 120 ksi steel grade steel. It can be seen that by using the processing method of the high-strength hydrogen sulfide corrosion-resistant drill pipe of this application, the processed high-strength hydrogen sulfide corrosion-resistant drill pipe has excellent mechanical properties, and the heat treatment process of this application will not reduce the mechanical properties of the high-strength hydrogen sulfide corrosion-resistant drill pipe. However, the preparation of the drill pipe weld area in the technical solution of Comparative Example 1 includes flash annealing of the drill pipe weld area. The quenching and tempering heat treatment includes the first quenching, the second quenching, the third quenching and tempering heat treatment. The coil specifications for each heat treatment are different. The whole process flow is relatively complex. During mass production, multiple quenching heat treatment stations need to be set up on site, seriously affecting production efficiency. In addition, the quenching temperature is relatively low, reaching the subcritical quenching range, and it is difficult to accurately control the proportion of tempered sorbite and ferrite in the duplex structure.

[0114] The technical solution of Comparative Example 2 is suitable for hydrogen sulfide corrosion-resistant drill pipes with relatively low strength grades of 95 ksi and 105 ksi. For 120 ksi drill pipes, the hardness of the weld area exceeds 30 HRC, and only 3 samples passed the 720 h sulfur resistance test.

[0115] It can also be seen from the data in Table 1 that the mechanical properties of the high-strength hydrogen sulfide corrosion-resistant drill pipes in Examples 9-12 of this application are also excellent, and the relevant properties also exceed the specified properties of the relevant standards for the corresponding steel grade steel. Thus, it can be seen that the processing method of the high-strength hydrogen sulfide corrosion-resistant drill pipe of this application can be used for the processing and preparation of high-strength hydrogen sulfide corrosion-resistant drill pipes with a steel grade of 115-135 ksi and a specification of 3.5-5.5 in. The mechanical properties of the prepared high-strength hydrogen sulfide corrosion-resistant drill pipes are all very excellent.

[0116] Table 2 Weld area hardness test results of examples and comparative examples of the present invention

[0117]

[0118] Table 3 Hydrogen sulfide stress corrosion performance results of examples and comparative examples of the present invention

[0119]

[0120] From the data in Table 2 and Table 3, it can be seen that the hardness of each part of the drill pipe welding area 3 of the high-strength hydrogen sulfide corrosion-resistant drill pipes in Examples 1 to 12 of this application can be controlled within 30 HRC. Using the NACE TM0177 standard hydrogen sulfide stress corrosion evaluation method for the drill pipes, they can all reach no fracture within 720 h (except for the invalid fracture of Sample 5 in Example 9); while for the high-strength hydrogen sulfide corrosion-resistant drill pipes in Comparative Example 1 and Comparative Example 2 of this application, there are unstable problems when the sample size is large, and the hardness of the weld part is greater than 30 HRC. For the drill pipe welding area heat treatment in Comparative Examples 3 - 5 using conventional processes and conducting SSC performance evaluation according to the NACE TM0177 standard hydrogen sulfide stress corrosion evaluation, the samples all fractured in a short time. From the experimental results of the SSC critical stress intensity factor KISSC for the D-method double cantilever beam test, it can be seen that the minimum value of the SSC critical stress intensity factor for the samples using the technology of the present invention is , the SSC critical stress intensity factor of the sample in Comparative Example 1 is , the SSC critical stress intensity factor of Comparative Example 2 is , and the maximum SSC critical stress intensity factor among the samples of the process schemes in Comparative Examples 3 - 5 is only . Thus, it can be seen that the SSC performance of the high-strength hydrogen sulfide corrosion-resistant drill pipes prepared by the processing method of this application is significantly better than the existing process technical schemes of the comparative examples; this also fully shows that through heat treatment of the drill pipe welding area 3 by the processing method of this application, the SSC performance of the drill pipes can be significantly improved.

[0121] From the data in Table 2, as well as Figure 4 and Figure 5 , it can also be seen that in the processing method of this application, the control of process parameters is extremely important. By comparing the hardness test data of Example 5 and Example 6 of this application, and the hardness test data of Example 7 and Example 8 of this application, it can be seen that the control of the process parameters of this application is closely related to the specifications of the drill pipes processed. Small-sized drill pipes need to use relatively low heat treatment temperatures, while large-sized drill pipes need to use relatively high heat treatment temperatures. In addition, cooling with a specific cooling medium and strictly controlling the heat treatment time can effectively improve the uniformity and stability of the microstructure of the welding area, and further reduce the hardness and improve the SSC performance.

[0122] From the data in Tables 1 to 3, by comparing the data of Example 7 with that of Comparative Examples 3 to 5, for the process of Example 7 of the present application, the high-strength drill pipe resistant to hydrogen sulfide corrosion obtained has significantly better performance in all aspects than the drill pipes obtained by the processes of Comparative Examples 3 to 5. It can be seen that when using the process of the present application, if the quenching temperature is higher than the temperature of the present application, the hardness of the welded zone of the finally obtained drill pipe is very high, and the toughness will also be significantly reduced. After heat treatment, the sulfur resistance performance will also be significantly decreased; the applicant speculates that too high quenching temperature will cause changes in the metallographic structure of the final alloy. After rapid cooling at high temperature, the grain size distribution in the metallographic structure of the alloy will be uneven, thus affecting the performance of the alloy. In addition, the control of the tempering temperature also has a great influence on the performance of the alloy of the present application. If the tempering temperature is lower than the temperature of the present application, it will lead to incomplete elimination of the thermal stress generated by quenching and insufficient structure transformation, thereby affecting the performance of the alloy in various aspects.

[0123] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereby. Therefore, all equivalent changes made according to the structure, shape, and principle of the present application should be covered within the protection scope of the present application.

Claims

1. A method for processing a high-strength drill pipe resistant to hydrogen sulfide corrosion, characterized in that: The following steps are involved: S1, using inertia friction welding to weld a drill pipe body (1) and a drill pipe joint (2) to form a drill pipe welding area (3), as well as flash inside the welding area and flash outside the welding area (4); S2, after the welding in step S1 is stopped, the flash inside the welding area is punched out under the high temperature residual heat generated by the welding to obtain a drill pipe with an external flash; S3, subjecting the drill pipe with external flash obtained in step S2 to normalizing treatment of the drill pipe weld zone (3), heating the drill pipe weld zone (3) to 860-920° C. within 50-70 seconds, and keeping the temperature for 80-100 seconds, wherein, if the drill pipe is larger than 4 inches, it is heated to 880-920° C., and if the drill pipe is smaller than 4 inches, it is heated to 860-880° C.; S4, air-cooling the drill pipe welding area (3) of the drill pipe with external flash that has been normalized in step S3 to below 300° C., and removing the external flash (4) of the welding area by turning to obtain a semi-finished drill pipe; S5, quenching the drill pipe weld zone (3) of the drill pipe semi-finished product obtained in step S4, heating the drill pipe weld zone (3) to 840-900° C. within 60-80 seconds, keeping the temperature for 90-110 seconds, and then cooling the drill pipe weld zone (3) for 50-80 seconds by using external liquid cooling and internal compressed air cooling; S6, tempering the drill pipe welding area (3) of the drill pipe semi-finished product quenched in step S5, heating the drill pipe welding area (3) to 670-710° C. within 60-80 seconds, keeping the temperature for 220-240 seconds, and air cooling to room temperature to obtain a high-strength hydrogen sulfide corrosion-resistant drill pipe finished product.

2. The method for processing a high-strength hydrogen sulfide corrosion-resistant drill pipe according to claim 1, characterized in that: In the step S2, after the welding is stopped in the step S1, the flash in the welding area is immediately punched out.

3. The method for processing a high-strength hydrogen sulfide corrosion-resistant drill pipe according to claim 1, characterized in that: In the steps S3 to S6, the heating is performed using an induction heating coil.

4. The method for processing a high-strength hydrogen sulfide corrosion-resistant drill pipe according to claim 3, characterized in that: In the step S3, during the normalizing treatment, the center of the induction heating coil is aligned with the center of the flash (4) outside the welding area.

5. The method for processing a high-strength hydrogen sulfide corrosion-resistant drill pipe according to claim 3, characterized in that: In the step S5 and step S6, during the quenching treatment and the tempering treatment, the center of the induction heating coil is aligned with the center of the drill rod welding area (3).

6. The method for processing a high-strength hydrogen sulfide corrosion-resistant drill pipe according to claim 3, characterized in that: In the step S5, during the quenching treatment cooling, the drill pipe welding area (3) is externally sprayed with a PAG aqueous solution for cooling.

7. A high-strength hydrogen sulfide corrosion resistant drill pipe prepared by the processing method of a high-strength hydrogen sulfide corrosion resistant drill pipe according to any one of claims 1 to 6, comprising a drill pipe body (1) and a drill pipe joint (2), characterized in that: The drill pipe body (1) and the drill pipe joint (2) are fixedly connected by friction welding, and the friction welding forms a drill pipe weld zone (3) between the drill pipe body (1) and the drill pipe joint (2). The material of the drill pipe body (1) and the drill pipe joint (2) is a steel material with a steel grade of 115 to 135 ksi; the strength grade of the drill pipe weld zone (3) reaches above 105 ksi, the metallographic structure is a uniform tempered bainite structure, the hardness does not exceed 30 HRC, and has the performance of resisting hydrogen sulfide stress corrosion cracking.

Images