Flexible pup joint for well completion of large-curvature horizontal well and method of flexible pup joint

Abstract

The invention relates to the technical field of oil and gas drilling, and discloses a flexible pup joint for well completion of a large-curvature horizontal well and a method thereof.The flexible pup joint comprises an upper connector, a sheath, a steel ball and a lower connector, a plurality of spherical grooves are distributed in the outer circumference direction of the lower portion of the upper connector, the end of the lower portion of the upper connector is a spherical surface, and the spherical surface is covered with vulcanized rubber; the end of the upper portion of the lower connector is provided with male threads, a plurality of through holes are distributed in the outer circumference of the upper portion of the lower connector in the circumferential direction, the positions of the through holes correspond to the positions of the spherical grooves of the upper connector in a one-to-one mode, an inner hole in the middle of the lower connector is a spherical surface and covered with vulcanized rubber, the end of the sheath is provided with female threads, and a plurality of through holes are distributed in the circumferential direction of the sheath. The device is connected into a well completion pipe string, so that the large-curvature horizontal well completion pipe string can be smoothly tripped into a preset position, and the device has torque transmission and sealing functions and does not influence rotation and circulating operation of the pipe string in the tripping-in process.

Description

Technical Field

[0001] This invention relates to the field of oil and gas drilling technology, specifically to a flexible short connector and its method for completing horizontal wells with high curvature. Background Technology

[0002] As oilfield development gradually enters its later stages, short-radius and ultra-short-radius sidetracking horizontal well technology has gradually become one of the most economical and effective means of tapping remaining oil potential and improving the production of inefficient wells. This technology mainly involves sidetracking with casing opening above the target layer in the old wellbore. By using specialized tools and instruments, it achieves high-curvature build-up and horizontal drilling, thereby forming a horizontal branch wellbore. To prevent wellbore collapse and sand blockage from affecting production, appropriate tubing strings need to be run during the completion stage. However, due to the large curvature characteristics of short-radius and ultra-short-radius horizontal wells, conventional completion tubing strings encounter great difficulties during the running-in process, and in some cases, cannot even be run smoothly.

[0003] Specifically, short-radius and ultra-short-radius sidetracking horizontal well technology involves sidetracking with casing windows above the target formation in the old wellbore. Using specialized tools and instruments, it enables high-curvature build-up and horizontal drilling. This process allows for the formation of horizontal branch wellbores, effectively tapping remaining oil potential and increasing production from inefficient wells. However, during the completion phase, to prevent wellbore collapse and sand blockage from affecting production, appropriate completion tubing strings need to be run. However, due to the significant curvature of short-radius and ultra-short-radius horizontal wells, conventional completion tubing strings encounter considerable difficulties during running, and in some cases, cannot be run at all. This not only increases the complexity and risk of the operation but also leads to increased operating costs, thus impacting overall economic efficiency. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a flexible short connector and its method for completing horizontal wells with high curvature, which solves the problems of low efficiency, poor sealing, severe equipment wear, and insufficient adaptability in the completion process of horizontal wells with high curvature.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a flexible short connector and method for completing horizontal wells with high curvature, comprising an upper connector, a sheath, a steel ball, and a lower connector. The lower outer circumference of the upper connector has multiple spherical grooves distributed therein, and the lower end is a spherical surface covered with vulcanized rubber. The upper end of the lower connector has a male thread, and the upper outer circumference of the lower connector has multiple through holes distributed therein, the positions of which correspond one-to-one with the positions of the spherical grooves of the upper connector. The middle inner hole of the lower connector has a spherical surface covered with vulcanized rubber. The end of the sheath has a female thread and multiple through holes distributed therein.

[0006] Preferably, the vulcanized rubber covering the spherical surfaces of the upper and lower connectors has a sealing function to prevent fluid leakage at the connection.

[0007] Preferably, the spherical groove of the upper connector, the through hole of the lower connector, and the steel ball cooperate to achieve a flexible connection between the upper and lower connectors, enabling the completion string to be smoothly lowered into the predetermined position in a well with high curvature, and having the ability to rotate and twist during the lowering process.

[0008] Preferably, the sheath is welded to the lower connector through its circumferential through hole to prevent the threaded connection from buckling, thereby improving the connection reliability of the device.

[0009] Preferably, the spherical surfaces of the upper and lower connectors are bent at a certain angle through spherical mating, so that the two sides of the pipe string can be bent at a certain angle to adapt to the special requirements of horizontal wells with large curvature.

[0010] A method for using a flexible short-joint for completing a horizontal well with high curvature includes the following steps: Step 1: Provide an upper connector, a sheath, a steel ball, and a lower connector. The lower part of the upper connector has multiple spherical grooves distributed in the outer circumference, and the lower end has a spherical surface covered with vulcanized rubber. The upper end of the lower connector has a male thread, and multiple through holes are distributed in the outer circumference. The positions of the through holes correspond one-to-one with the positions of the spherical grooves of the upper connector. The inner hole in the middle has a spherical surface covered with vulcanized rubber. Step 2: Install the steel ball in the spherical groove of the upper connector, so that the upper connector and the lower connector can be flexibly connected with the cooperation of the steel ball, so that the spherical surface at the end of the upper connector and the spherical surface at the end of the lower connector can be matched to form a flexible connection that can rotate. Step 3: Connect the female thread of the sheath to the male thread of the lower connector, and weld the circumferential through hole of the sheath to the lower connector to prevent the thread from turning back. Step 4: Connect the flexible short joint in the completion string. Through the steel ball and spherical mating structure, the completion string can form a certain angle of bending in a horizontal well with large curvature, and maintain the functions of rotation, torsion transmission and sealing during the running process to ensure the smooth progress of the completion operation.

[0011] Preferably, in step 2, the upper and lower connectors are kept at a preset angle by the positioning and cooperation of the steel ball and the spherical groove of the upper connector, thereby increasing the smoothness of the pipe string insertion in the high curvature well.

[0012] Preferably, in step 3, the welding and fixing of the sheath is achieved through multi-point welding to further enhance the stability of the connection between the sheath and the lower connector and to prevent loosening under high torque conditions in the well.

[0013] Preferably, in step 3, the spherical surfaces of the upper and lower connectors are permeated with a vulcanized rubber layer to increase the friction of the spherical contact, thereby effectively improving the sealing performance and preventing fluid leakage.

[0014] Preferably, in step 4, during the installation of the completion tubing string, the rotation angles of the upper and lower connectors are adjusted to achieve precise positioning of the tubing string, thereby adapting to the requirements of different wellbore curvatures and improving the accuracy and safety of the completion operation.

[0015] This invention provides a flexible connector and method for completing horizontal wells with high curvature. It offers the following advantages: 1. This invention enables the smooth installation of completion tubing strings in horizontal wells with large curvature to the predetermined position. Moreover, this invention has torque transmission and sealing functions, and does not affect the rotation and circulation of the tubing strings during the installation process.

[0016] 2. This invention improves well completion efficiency through a flexible short-connector design, effectively adapting to changes in wellbore curvature, reducing resistance and friction during the running-in process, and accelerating operation. Secondly, enhanced sealing performance reduces the risk of fluid leakage, ensuring the safety of fluids within the well and environmental protection, while also improving operational safety. Furthermore, this device flexibly addresses complex wellbore conditions, avoiding the limitations of traditional rigid connectors, thus enhancing adaptability and broad application potential. The fit between the steel ball and the spherical surface in the design significantly reduces wear, extends equipment lifespan, and reduces maintenance requirements. Simultaneously, the simplified installation process requires no additional tools, reducing labor costs and improving efficiency. Fluid management is also optimized, ensuring smooth operation. Attached Figure Description

[0017] Figure 1 This is a perspective view of the present invention; Figure 2 This is a schematic diagram of the upper connector of the present invention; Figure 3 This is a schematic diagram of the structure of the sheath of the present invention; Figure 4 This is a schematic diagram of the lower connector of the present invention.

[0018] Among them, 1. upper connector; 2. sheath; 3. steel ball; 4. lower connector. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example

[0020] Please see the appendix Figure 1 - Appendix Figure 4 This invention provides a flexible short connector and method for completing horizontal wells with high curvature, aiming to improve the completion efficiency, operational safety, and economy of wells with high curvature through innovative structural design and implementation steps.

[0021] 1. Structural Composition The flexible shorting device of the present invention consists of four parts: an upper connector, a sheath, a steel ball, and a lower connector. The design and function of each part are as follows: Upper Connector: Multiple spherical grooves are evenly distributed around the lower outer circumference of the upper connector. These grooves are designed to distribute the load evenly in all directions. The lower end face is a spherical surface covered with a moderately thick layer of vulcanized rubber. The rubber layer provides a sealing function, reducing fluid leakage during the lowering process, while also absorbing vibration and shock, reducing the risk of equipment damage. The spherical groove design allows for easy installation of steel balls and creates a flexible, movable connection between the upper and lower connectors, facilitating adaptation to different wellbore shapes.

[0022] Lower Connector: The upper end of the lower connector has a male thread for easy connection and fixation to the sheath. Multiple through holes are provided on the outer circumference, their number and position corresponding one-to-one with the spherical grooves of the upper connector, forming a precise fit. The inner bore in the center of the lower connector is also designed with a spherical surface, covered with vulcanized rubber. This design not only provides a sealing function but also reduces wear during connector rotation. The through hole design ensures the steel ball can move freely, maintaining flexibility under high curvature well conditions, allowing the connection to effectively adapt to changes in wellbore curvature.

[0023] Sheath: The end of the sheath is threaded female, which tightly connects to the male thread of the lower connector. Multiple through holes are provided circumferentially around the sheath; these holes provide additional holding force during welding, ensuring the connection remains secure. The sheath's structural design not only provides fixation and protection but also ensures overall stability under high pressure environments. Furthermore, the outer surface of the sheath can be coated with an anti-corrosion material to enhance its durability, especially its service life in harsh environments.

[0024] Steel ball: As the core component of the connection, the steel ball is installed in the spherical groove of the upper connector. The steel ball is usually made of high-strength alloy steel, which undergoes precision machining and heat treatment to improve its wear resistance and corrosion resistance. The freedom of movement of the steel ball provides flexibility between the upper and lower connectors, allowing the completion string to adapt to various bends and torsions in the complex downhole environment.

[0025] 2. Principle Explanation The flexible connector of this invention, through its ingenious structural design, enables well completion operations in horizontal wells with high curvature. Its working principle is mainly reflected in the following aspects: Flexibility: The spherical surfaces of the upper and lower connectors, along with the use of steel balls, allow the connectors to rotate and bend freely within a certain angle range. This design enables the completion string to flexibly adapt to changes in wellbore curvature during installation, avoiding jamming and equipment damage caused by rigid connections.

[0026] Sealing performance: The application of vulcanized rubber significantly improves the sealing performance at joints. Under high pressure, the rubber layer effectively prevents fluid leakage, ensuring that fluid in the well does not enter the tubing string, thus enhancing the overall safety of the operation. By optimizing the thickness and hardness of the rubber, excellent sealing performance is maintained even under high temperature and high pressure conditions.

[0027] Torque transmission performance: During well completion, a certain torque needs to be applied to the tubing string. The flexible short joint, through its steel ball connection design, effectively transmits torque from the upper joint to the lower joint, allowing the tubing string to not only be smoothly lowered during installation but also to be rotated, ensuring efficient well completion operations. The steel balls are designed with wear and tensile strength in mind to guarantee stability during repeated torsion and cyclic operations.

[0028] 3. Detailed Explanation of Technical Content This invention solves several technical problems through optimized design, specifically in the following aspects: Wear resistance: All surfaces in contact with the fluid are treated with wear-resistant materials to reduce wear under high-flow-rate operating conditions. Simultaneously, the freedom of movement of the steel balls effectively reduces the risk of wear at the connection points, extending service life. The contact surfaces of the upper and lower connectors undergo special treatment to enhance their wear and corrosion resistance.

[0029] Ease of installation: This flexible connector design takes into account the complexity of downhole operations, eliminating the need for additional tools or equipment during installation. All connecting components can be quickly assembled downhole, reducing time and labor costs. The modular design allows operators to quickly understand and master the installation process, improving operational efficiency.

[0030] Welding Reliability: The sheath's welded fixing structure employs a multi-point welding method, significantly improving the strength and stability of the connection. Specialized equipment is used during the welding process to ensure weld quality meets industry standards, thereby guaranteeing that the connection will not break under high-load operation. The selection of welding materials also undergoes rigorous testing to ensure reliability under extreme conditions.

[0031] 4. Specific Implementation Steps To achieve the best operational results, the following are the specific implementation steps of this invention: Step 1: Preparation Before installation, prepare the upper connector, sheath, steel ball, and lower connector. Inspect all components for integrity, ensuring there are no cracks, defects, or other flaws that could affect performance. Clean each component, ensuring it is free of oil and impurities to improve the tightness of the connection.

[0032] Step 2: Steel ball installation Place the steel balls one by one into the spherical grooves of the upper connector, ensuring that the steel balls can move freely without restriction. At this stage, pay attention to the arrangement and orientation of the steel balls to ensure flexibility and stability in subsequent operations. It is recommended to use professional assembly tools to ensure accurate and consistent installation of the steel balls.

[0033] Step 3: Connecting the sheath Connect the female thread of the sheath to the male thread of the lower connector, ensuring a secure and loose connection. Next, align the circumferential through hole of the sheath with the through hole of the lower connector and weld them together. Automated welding equipment should be used to ensure uniform and defect-free welding. After welding, non-destructive testing should be performed to ensure the weld quality meets standards.

[0034] Step 4: Installation of the completion string Connect the assembled flexible connector to the completion tubing string, ensuring a tight fit at all connection points. During the running-in process, utilize the flexibility of the steel balls and the fit of the spherical surface to facilitate the smooth running of the tubing string into wells with high curvature. At this time, real-time monitoring of well pressure and fluid conditions is essential to ensure operational safety. It is recommended to use downhole monitoring instruments to provide real-time feedback on torque, pressure, and temperature changes.

[0035] Step 5: On-site adjustments Based on the actual wellbore curvature, the rotation angles of the upper and lower connectors are dynamically adjusted during the running-in process to achieve precise positioning. Adjustments should be made slowly and steadily to avoid shocks caused by excessive speed. Simultaneously, torque and pressure changes during the tubing string running-in process are recorded using on-site monitoring equipment to ensure operations remain within safe limits. Emergency plans are prepared to address unforeseen circumstances.

[0036] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A flexible connector for completion of a horizontal well with high curvature, comprising an upper connector (1), a sheath (2), a steel ball (3), and a lower connector (4), characterized in that: The upper connector (1) has multiple spherical grooves distributed in the lower outer circumference, and the lower end is a spherical surface covered with vulcanized rubber. The upper end of the lower connector (4) is a male thread, and multiple through holes are distributed in the upper outer circumference. The position of the through holes corresponds one-to-one with the position of the spherical grooves of the upper connector (1). The middle inner hole of the lower connector (4) is a spherical surface covered with vulcanized rubber. The end of the sheath (2) is a female thread, and multiple through holes are distributed in the circumference.

2. The flexible connector for completion of a high-curvature horizontal well according to claim 1, characterized in that, The vulcanized rubber covering the spherical surfaces of the upper connector (1) and the lower connector (4) has a sealing function to prevent fluid leakage at the connection.

3. The flexible connector for completion of a high-curvature horizontal well according to claim 1, characterized in that, The spherical groove of the upper connector (1), the through hole of the lower connector (4), and the steel ball (3) work together to achieve a flexible connection between the upper connector (1) and the lower connector (4), so that the completion string can be smoothly lowered into the predetermined position in a well with high curvature and has the ability to rotate and twist during the lowering process.

4. The flexible connector for completion of a high-curvature horizontal well according to claim 1, characterized in that, The sheath (3) is welded to the lower connector (4) through its circumferential through hole to prevent the threaded connection from buckling, thereby improving the connection reliability of the device.

5. A flexible connector for completion of a horizontal well with high curvature according to claim 1, characterized in that, The spherical surfaces of the upper connector (1) and the lower connector (4) form a certain angle of curvature through spherical mating, so that the two sides of the pipe string can be bent at a certain angle to adapt to the special requirements of a large curvature horizontal well.

6. A method for a flexible short connector for completing a horizontal well with high curvature, as described in any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Provide an upper connector (1), a sheath (3), a steel ball (2), and a lower connector (4). The lower outer circumference of the upper connector (1) is distributed with multiple spherical grooves, and the lower end is a spherical surface covered with vulcanized rubber. The upper end of the lower connector (4) is male threaded, and multiple through holes are distributed in the outer circumference. The positions of the through holes correspond one-to-one with the positions of the spherical grooves of the upper connector (1). The inner hole in the middle is a spherical surface covered with vulcanized rubber. Step 2: Install the steel ball (2) in the spherical groove of the upper connector, so that the upper connector (1) and the lower connector (4) can be flexibly connected with the cooperation of the steel ball (2), so that the spherical surface at the end of the upper connector (1) and the spherical surface at the end of the lower connector (4) can cooperate to form a rotatable flexible connection. Step 3: Connect the female thread of the sheath (3) to the male thread of the lower connector (4), and weld the circumferential through hole of the sheath (3) to the lower connector (4) to prevent the occurrence of thread backing. Step 4: Connect the flexible short joint in the completion string. Through the steel ball (2) and the spherical mating structure, the completion string can form a certain angle of bending in a horizontal well with a large curvature, and maintain the functions of rotation, torsion transmission and sealing during the running process, so as to ensure the smooth progress of the completion operation.

7. A method for flexible shorting joints in the completion of horizontal wells with large curvature according to claim 6, characterized in that, In step 2, the upper connector (1) and the lower connector (4) are positioned and matched by the steel ball (2) and the spherical groove of the upper connector (1), so that the upper connector (1) and the lower connector (4) maintain a preset angle, thereby increasing the smoothness of the pipe string in the high curvature well.

8. A method for flexible short-joint completion of a horizontal well with high curvature according to claim 6, characterized in that, In step 3, the welding and fixing of the sheath (3) is achieved by multi-point welding to further enhance the stability of the connection between the sheath (3) and the lower connector (4) and avoid loosening under high torque conditions in the well.

9. A method for flexible short-joint completion of a horizontal well with high curvature according to claim 6, characterized in that, In step 3, the spherical surfaces of the upper connector (1) and the lower connector (4) are permeated with a vulcanized rubber layer, which increases the friction of the spherical contact, thereby effectively improving the sealing performance and preventing fluid leakage.

10. A method for flexible short-joint completion of a horizontal well with high curvature according to claim 6, characterized in that, In step 4, during the installation of the completion tubing string, the rotation angles of the upper connector (1) and the lower connector (4) are adjusted to achieve precise positioning of the tubing string, so as to adapt to the requirements of different wellbore curvatures and improve the accuracy and safety of the completion operation.

Images