Hydraulic Frusto-Conical Coupling Assembly for High-Torque Drill Pipe Joints
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Solution Overview
Problem
Current couplings for deep well drilling and oil/gas reservoirs face challenges in handling high torque, pressure resistance, and friction losses, particularly in extended-reach drilling, where traditional threaded connections are inefficient and prone to deformation due to increased make-up torque and radial clamp force.
Innovation Solution
A coupling assembly featuring a pin and box member with key-and-lock configurations, including frusto-conical surfaces and recessed/protruding portions, which align before mating, and a method involving hydraulic fluid injection to achieve secure engagement without rotational motion, enhancing axial/tensile strength and torque performance while preventing micro-slip under repetitive loading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional threaded connections are used, then assembly is simple and device complexity is low, but torque resistance and pressure resistance are insufficient for deep well drilling
Solution Approach 1:
The coupling assembly is divided into distinct pin member and box member components with separate functional zones: external threads for initial engagement, internal threads for securing, and a shoulder interface for torque transmission. This segmentation allows each component to be optimized for its specific function while maintaining overall structural integrity for deep well applications
Solution Approach 2:
The coupling assembly employs composite structural design combining threaded metal components with integrated sealing elements and bearing surfaces. The pin and box members feature composite functional zones with different material properties optimized for threading, sealing, and torque resistance respectively, enabling superior performance in high-pressure deep well environments
2Strength
If premium connections with thicker walls are used, then pressure resistance and torque resistance improve, but hydrodynamic drag increases and ease of operation deteriorates
Solution Approach 1:
The pin and box members feature non-uniform wall thickness distribution with thicker sections at the shoulder interface for torque resistance and thinner sections in the cylindrical body to reduce hydrodynamic drag. This local quality variation optimizes the balance between mechanical strength requirements and fluid flow efficiency in deep well drilling operations
3Strength
If higher make-up torque is applied, then connection strength and torque resistance improve, but radial clamp force increases causing coupling deformation
Solution Approach 1:
The connection process follows a predetermined sequence: first external threads engage to establish initial connection, then internal threads are engaged to secure the joint, and finally the shoulder interface is compressed to create the sealing and torque-bearing connection. This preliminary action sequence distributes the make-up torque across multiple engagement stages, preventing excessive radial clamp force and coupling deformation
4Reliability
If threaded connections are used for deep well drilling, then connection security is achieved, but friction losses increase significantly in extended-reach drilling
Solution Approach 1:
The design extracts and separates the torque transmission function from the threaded connection function. The shoulder interface is designed to bear the majority of torque loads, allowing the threaded portions to serve primarily for alignment and initial securing. This extraction reduces the friction losses associated with threaded torque transmission while maintaining connection security for deep well drilling
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The coupling assembly provides improved torque and compression resistance, reduces friction losses, and allows for bidirectional torque transfer, enabling efficient connection and disconnection of elongated elements like drill pipes without rotational motion, thus addressing the inefficiencies of traditional threaded connections.
Implementation Method 1
a method involving hydraulic fluid injection to achieve secure engagement without rotational motion
Data Source
AI summary
A coupling assembly for elongate elements (1, 2) comprises a pin member (5) and a box member (6), said pin and box members having complementary and respective frusto-conical pin and box mating surfaces (12, 13). A bore (9; 9′) has as a first opening a port (9a) configured for connection to an injection fluid reservoir (10) and a second opening (9b) penetrating the pin mating surface (12) or the box mating surface (13). The surfaces (12, 13) may be plain surfaces without helical threads or other pronounced protrusions configured for mating engagement, but comprise a textured finish in order to augment static friction between the surfaces (12, 13) when the surfaces are connected. The pin surface may comprise a plurality of pin protruding portions (181-n) separated by pin recessed portions (191-n), and the box surface (13) comprise a plurality of box protruding portions (201-n) separated by box recessed portions (211-n). The pin protruding portions (18n) are shaped and dimensioned to fit into a designated box recessed portion (21n), and the box protruding portions (20n) are shaped and dimensioned to fit into a designated pin recessed portion (19n).