Streamline drill rod joint
The streamlined drill pipe joint, made of streamlined design and high-strength materials, solves the problem of excessive annular circulation pressure loss in small-diameter drilling, thereby improving drilling efficiency and safety, and is suitable for oil drilling equipment.
Patent Information
- Application Number
- CN202520453455.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-16
- Publication Date
- 2026-02-06
- Estimated Expiration
- 2035-03-16
AI Technical Summary
Excessive annular circulation pressure loss during small-diameter drilling affects drilling efficiency and safety. Traditional drill pipe joints experience high flow resistance during high-speed rotation, leading to excessive energy consumption.
The streamlined drill pipe joint is designed with streamlined curved surfaces on the outer walls of the male and female joints that smoothly transition into the drill pipe body, reducing annular flow resistance. High-strength alloy steel and a special thread design are used to ensure reliable connection and sealing.
It significantly reduces annular circulation pressure loss by 15-20%, improves drilling efficiency, extends equipment life, adapts to complex formations and harsh environments, and meets the needs of small-diameter drilling.
Smart Images
Figure CN223881128U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to the technical field of petroleum drilling equipment, especially to the solution of the problem of excessive annular circulation pressure loss in the slim hole drilling process. BACKGROUND
[0002] In the field of petroleum drilling operation, the slim hole drilling technology is widely applied due to its advantages of reducing drilling cost, reducing environmental impact and improving resource utilization. However, the slim hole drilling also faces many challenges. The slim hole drilling speed is fast, and the high-speed rotation of the mud in the high-speed return annulus generates a large centrifugal force, which not only destroys the performance of the mud and the carrying effect of the rock, but also greatly increases the annular pressure loss, excessively consumes the energy of the drilling fluid, weakens the ability to carry cuttings, and requires strict well control. The traditional drill rod joint has a regular shape, and when the drilling fluid circulates, the annular fluid flow resistance between the drill rod joint and the well wall is large, which causes the circulation pressure loss to increase, seriously affecting the drilling efficiency and quality. Therefore, there is an urgent need for a drill rod joint that can effectively reduce the annular circulation pressure loss of the slim hole to solve the above technical problems, improve the drilling efficiency, reduce the drilling risk, and meet the special requirements of slim hole drilling. SUMMARY
[0003] The core purpose of the utility model is to provide a streamlined drill rod joint, which effectively reduces the annular circulation pressure loss of the slim hole and improves the drilling efficiency by optimizing its shape structure.
[0004] To achieve the above purpose, the utility model provides the following technical scheme:
[0005] 1. Joint basic structure: the drill rod joint is composed of a male joint and a female joint. The front end of the male joint is a connecting end for connecting with the female joint of the adjacent drill rod, and the rear end is connected with the drill rod body; the front end of the female joint is a receiving end for receiving the connecting end of the male joint, and the rear end is also connected with the drill rod body.
[0006] 2. Streamlined curved surface design: the outer side wall of the male joint gradually transitions from the connecting end to the rear end to a streamlined curved surface, which smoothly transitions with the outer side wall of the drill rod body; the outer side wall of the female joint also adopts a similar streamlined curved surface design from the receiving end to the rear end, which smoothly transitions with the outer side wall of the drill rod body. This design can significantly reduce the resistance of the drilling fluid when flowing in the annulus and reduce the circulation pressure loss.
[0007] 3. Connection thread design: the connecting end of the male joint is provided with external threads, and the receiving end of the female joint is provided with matching internal threads. In the actual drill rod connection process, the external threads are rotated with the internal threads to realize reliable connection between the drill rods. BRIEF DESCRIPTION OF DRAWINGS
[0008] Figure 1 Front view of the streamlined drill rod joint male joint
[0009] Figure 2 Front view of streamlined drill pipe joint female joint Figure 3 Front view of male joint and female joint connection
[0010] Marked description in the figure
[0011] 1-drill pipe, 2-streamlined surface of male joint, 3-external thread of male joint, 4-receiving end of female joint, 5-streamlined surface of female joint DETAILED DESCRIPTION
[0012] 1. Manufacture of drill pipe joint: high-quality alloy steel material is selected, and first, the blanks of male joint and female joint are manufactured through forging process. Then, the blanks are processed by high-precision numerical control processing equipment, and the streamlined surface, external thread and internal thread of the male joint and female joint are accurately processed according to the design requirements.
[0013] 2. Connection of drill pipe joint: during drilling site operation, the connecting end of the male joint of a drill pipe is inserted into the receiving end of the female joint of the adjacent drill pipe, and then the drill pipe is rotated to make the external thread of the male joint engage with the internal thread of the female joint, thereby realizing reliable connection between the drill pipes.
[0014] 3. Drilling fluid circulation: during drilling, the drilling fluid flows downward from the drill pipe bore, passes through the drill pipe joint, and then flows upward from the annulus between the drill pipe and the well wall. Since the male joint and the female joint are designed in a streamlined manner, the resistance of the drilling fluid when flowing in the annulus is significantly reduced, and the circulation pressure consumption is reduced, thereby ensuring the normal circulation of the drilling fluid and good rock carrying capacity, and effectively improving the drilling efficiency.
[0015] Application example
[0016] (1) Drilling of complex formations in offshore oilfields
[0017] An offshore oilfield has complex formation structure, multiple high-pressure oil and gas layers and easily collapsed mud shale layers, and the seawater environment is highly corrosive to drilling tools. The traditional drill pipe joint not only faces the problem of low drilling efficiency caused by high circulation pressure consumption, but also often damages due to corrosion and stress concentration. The use of this streamlined drill pipe joint can effectively resist seawater erosion due to its strong corrosion-resistant alloy material. The streamlined design reduces the circulation pressure consumption by about 20%, reduces the energy consumption of the mud pump, and prolongs the service life of the equipment.
[0018] (2) Shale gas horizontal well exploitation
[0019] In shale gas horizontal well production, the long horizontal sections and complex wellbore trajectories place high demands on drill pipe flexibility and joint sealing. Traditional joints can easily cause poor drilling fluid flow at bends, increasing friction and affecting drilling progress. This streamlined drill pipe joint features a smooth, streamlined curved surface that connects tightly to the drill pipe body, reducing friction at bends and lowering circulating pressure loss by approximately 16%. The threaded connection provides excellent sealing, withstands complex stresses during production, and prevents gas leakage.
[0020] (III) High-temperature and high-pressure drilling of geothermal wells
[0021] Geothermal well drilling faces harsh conditions with high temperatures (up to 250°C and above) and high pressures (high formation pressure). Traditional drill pipe joints suffer from easily aging and failure of sealing materials, and high circulating pressure loss, affecting the drilling fluid's ability to cool the drill bit. This streamlined drill pipe joint utilizes special high-temperature and high-pressure resistant alloys and sealing materials, maintaining excellent performance even under these conditions. The streamlined design effectively reduces circulating pressure loss by approximately 17%, allowing the drilling fluid to better cool the drill bit and extend its service life.
[0022] I. Overall Structural Parameters
[0023] (I) Connector Composition and Applicable Scenarios
[0024] This streamlined drill pipe connector consists of a male connector ( Figure 1 ) and female connector ( Figure 2 Composed of two parts, this joint is specifically designed for small-diameter drilling operations. In small-diameter environments, traditional drill pipe joints can easily lead to excessive annular circulation pressure loss, while this joint, through its special design, can effectively reduce this pressure loss, making it suitable for small-diameter drilling projects in the extraction of resources such as oil and natural gas.
[0025] (II) Overview of External Dimensions
[0026] The overall joint's length, outer diameter, and other dimensional parameters are designed to match different specifications of drill pipe, ensuring compatibility with existing drilling equipment and drill pipe systems while meeting the working space requirements in small wellbores.
[0027] II. Male connector parameters (I) Front end connection (3)
[0028] 1. Thread Parameters: The external thread adopts a special thread design conforming to API (American Petroleum Institute) or other internationally recognized standards to ensure the reliability and sealing of the connection. The thread specification is NC38, the pitch is 6mm, the thread angle is 60°, and the thread tolerance is strictly controlled within the 6g precision grade. The external thread is 50mm long and has undergone mechanical performance testing. Even with an axial tensile force of 300kN and a torque of 15000N·m, it maintains a good connection condition without significant deformation or loosening.
[0029] 2. Auxiliary structure: A chamfer with an angle of 15° is arranged at the front end of the thread, which facilitates the smooth insertion of the male joint into the receiving end of the female joint and reduces thread wear. At the same time, the thread surface is hardened or coated with a special coating to enhance wear resistance and corrosion resistance and prolong service life.
[0030] (II) Connection part with drill pipe body
[0031] 1. Size parameter: The inner diameter of the connection part with the drill pipe body is accurately matched with the inner diameter of the connected drill pipe, with a deviation controlled within ±0.1 mm, ensuring smooth flow of drilling fluid in the drill pipe without significant throttling loss. The outer diameter of this part is consistent with the outer diameter of the drill pipe body, which is 88.9 mm, and the length of the connection part is 80 mm. It is firmly connected with the drill pipe body through high-strength welding processes such as friction welding and butt welding, and the weld strength is not less than 95% of the strength of the parent material.
[0032] 2. Transition design: Smooth transition design is adopted between the connection part and the streamlined curved surface of the male joint, with a curvature radius of 600 mm in the transition area, effectively reducing the resistance and vortex generated during the flow of drilling fluid.
[0033] (III) Streamlined curved surface on the outer side wall (2)
[0034] 1. Curved surface profile: Gradually transitions to a streamlined curved surface from the connection end to the rear end, with a curved surface length of 150 mm. The shape of this curved surface is optimized through CFD (Computational Fluid Dynamics) simulation, conforming to NACA (National Advisory Committee for Aeronautics) airfoil or other suitable fluid dynamics curve equations to achieve minimum fluid resistance. The maximum outer diameter does not exceed the outer diameter of the drill pipe body, with a specific value of 88.9 mm (usually 0 mm smaller than the outer diameter of the drill pipe body), ensuring smooth running in the small hole.
[0035] 2. Curvature parameter: The curvature radius of the curved surface is designed in different positions for segmented optimization to adapt to the flow characteristics of drilling fluid in the annulus. The initial segment has a curvature radius of 400 mm, the middle segment has a curvature radius of 500 mm, and the transition segment connecting the end to the drill pipe body has a curvature radius of 700 mm, ensuring smooth transition of drilling fluid when flowing through the curved surface and reducing energy loss.
[0036] 3. Surface treatment: The streamlined curved surface is finely processed, with a surface roughness controlled below Ra0.8 μm, reducing the frictional resistance of drilling fluid and joint surface. At the same time, special surface treatments such as hard chromium plating, chemical nickel-phosphorus plating, etc. can be performed as needed to further improve surface hardness and corrosion resistance.
[0037] Three, female joint parameters (I) receiving end of the front end (4)
[0038] 1. Thread parameters: The internal thread is precisely matched with the external thread of the pin, and the same special thread of API or other international standards is adopted, with the same model as the external thread of the pin (NC38). The internal thread pitch and tooth angle are the same as the external thread of the pin (pitch 6mm, tooth angle 60°), and the accuracy grade is 6H. The internal thread length is 55mm, and after being screwed with the pin, a reliable sealing connection can be formed, and there is no leakage phenomenon when the internal pressure reaches 35MPa.
[0039] 2. Sealing structure: A sealing groove is provided in the receiving end for installing a sealing ring such as an O-ring, a metal sealing ring, etc. The size of the sealing groove is: width 10mm, depth 5mm, to ensure that the sealing ring can effectively fill the thread gap after installation and improve the sealing performance. At the same time, the inner surface of the sealing groove is treated specially, such as copper plating or coating sealing glue, to further enhance the sealing effect.
[0040] (II) Connection part of the rear end with the drill pipe body
[0041] 1. Size parameters: The inner diameter and outer diameter of the connection part of the rear end with the drill pipe body are the same as the corresponding part of the pin, which are 88.9mm and 88.9mm respectively, and the length is 80mm. The same welding process as the pin is adopted to connect with the drill pipe body, and the connection strength and reliability are guaranteed.
[0042] (III) Streamlined curved surface on the outer side wall (5)
[0043] 1. Curved surface profile: gradually transitions to a streamlined curved surface from the receiving end to the rear end, with a curved surface length of 150mm, the shape and size of which are matched with the streamlined curved surface design of the pin, and the maximum outer diameter is 88.9mm (not greater than the outer diameter of the drill pipe body). Similarly, CFD simulation optimization is performed to achieve the effect of cooperative drag reduction with the pin.
[0044] 2. Curvature parameters: The curvature radius distribution of the curved surface is similar to that of the pin, with a starting segment curvature radius of 400mm, an intermediate segment curvature radius of 500mm, and a transition segment curvature radius of 700mm at the end connected with the drill pipe body, to ensure the smoothness of the drilling fluid flow in the annulus.
[0045] 3. Surface treatment: the same surface treatment method as the streamlined curved surface of the pin is adopted, with a surface roughness controlled below Ra0.8μm, and the same special surface treatment can be performed to improve the performance.
[0046] Four, other parameters
[0047] (I) Material parameters
[0048] The male joint and the female joint are made of high-strength alloy steel material, such as 42CrMo, and the chemical composition thereof meets relevant national standards or industry standards. 2 After quenching and tempering treatment, the material has a tensile strength of ≥850 MPa, a yield strength of ≥650 MPa, an elongation of ≥12%, and an impact toughness of ≥60 J / cm
[0049] (II) weight parameters
[0050] The weight of the male joint is 3 kg, and the weight of the female joint is 3.2 kg. On the premise of meeting the performance requirements, the joint weight is reduced as much as possible by optimizing the structural design and material selection, thereby reducing the load of the drilling equipment.
[0051] (III) temperature and pressure adaptation parameters
[0052] The working temperature range of the streamline drill pipe joint is -20℃ to 150℃, and the mechanical properties and sealing performance of the material are not significantly affected within the temperature range. At the same time, the maximum internal pressure that can be withstood is 50 MPa, and the maximum external pressure is 40 MPa, which ensures reliable work in different downhole pressure environments.
[0053] Advantages
[0054] The male joint and the female joint are made of high-strength alloy steel material, such as 42CrMo, and the chemical composition thereof meets relevant national standards or industry standards.
[0055] In summary, the streamline drill pipe joint of the present application can effectively reduce the annular circulating pressure consumption during the slim hole drilling process, improve the drilling efficiency and safety, and has important practical application value and broad application prospect in the field of oil drilling equipment.
[0056] Although the present application has been described in detail above, it is obvious to those skilled in the art that appropriate modifications or improvements can be made on the basis of the present application. Therefore, these modifications or improvements made without departing from the core spirit of the present application should be included in the protection scope of the present application.
Claims
1. A streamlined drill pipe joint, characterized by The main part is composed of a male joint and a female joint in a smooth streamline curve, the front end of the male joint is a connecting end (3) for connecting with the female joint of the adjacent drill pipe, the rear end of the male joint is connected with the drill pipe body, the outer wall (2) of the male joint from the connecting end (3) to the rear end is a streamline curve, which is smoothly connected with the outer wall of the drill pipe body (1), the front end of the female joint is a receiving end (4) for receiving the connecting end (3) of the male joint, the rear end of the female joint is connected with the drill pipe body, the outer wall (5) of the female joint from the receiving end (4) to the rear end is a streamline curve, which is smoothly connected with the outer wall of the drill pipe body, the connecting end (3) of the male joint is provided with an external thread, and the receiving end (4) of the female joint is provided with an internal thread matched with the external thread.
2. A streamlined drill pipe joint as defined in claim 1, wherein, The curvature radius of the streamline curve smoothly connected with the outer wall of the drill pipe body is accurately controlled in the range of 500-800 mm.
3. A streamlined drill pipe joint as defined in claim 1, wherein, The male joint and the female joint are both made of high-strength alloy steel, the tensile strength of the high-strength alloy steel is ≥800 MPa, and the yield strength is ≥600 MPa.
4. A streamlined drill pipe joint as defined in claim 1, wherein, The pitch of the external thread and the internal thread is designed to be between 5-8 mm, and the thread angle is 55° or 60°.