Preloaded Fracturing Connection Assembly for Cyclic Pressure Fatigue
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Solution Overview
Problem
Hydraulic fracturing connections in oil or gas wells face challenges with fatigue damage due to cyclic pressure changes, as existing connections fail to effectively manage peak hydrodynamic loads, leading to potential loosening and failure under high-pressure conditions.
Innovation Solution
A threaded connection assembly with a preload mechanism, comprising circumferentially spaced bores and threaded fixings that apply an axial load between shoulders, exceeding peak hydrodynamic loads, using annular sealing members to ensure secure fluid flow and reduce fatigue damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing threaded connections are used in hydraulic fracturing operations, then the connection assembly can transmit high pressure fluid, but the connection is susceptible to fatigue damage and loosening due to cyclic pressure changes and peak hydrodynamic loads
Solution Approach 1:
The preload mechanism applies an axial compressive load to the connection assembly before the hydraulic fracturing operation begins. This preliminary action creates a clamping force that maintains thread engagement and prevents loosening during subsequent cyclic pressure changes and peak hydrodynamic loads, thereby reducing fatigue damage and improving connection reliability
Solution Approach 2:
The preload mechanism counteracts the tendency of the connection to loosen under hydraulic loads by applying a pre-compressive force in the opposite direction. This preliminary anti-action prevents the hydrodynamic forces from overcoming thread friction and causing disengagement, thus protecting against fatigue damage and maintaining connection integrity
2Reliability
If a preload mechanism with multiple threaded fixings is added to the connection assembly, then fatigue damage is reduced and connection integrity is improved, but the device complexity increases
Solution Approach 1:
The preload mechanism is segmented into multiple independent threaded fixings distributed around the connection assembly. Each fixing independently contributes to the overall preload, allowing the system to achieve the required clamping force through multiple smaller elements rather than a single complex mechanism, thereby managing device complexity while improving reliability
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 preload mechanism effectively reduces fatigue damage and maintains connection integrity under high-pressure cycling, allowing for secure high-pressure fluid transmission and extended connection life without requiring specialized tools for assembly.
Implementation Method 1
a preload mechanism comprising: a plurality of bores circumferentially spaced around the axis and extending through the first face in a direction towards the second face; a plurality of threaded fixings passing through the bores towards the second face adapted to engage a thread; and wherein the preload mechanism is arranged to apply an axial load between the first and second shoulders when torque is applied to the threaded fixings
Implementation Method 2
the assembly comprises at least one annular sealing member in compression between the first and second portions
Data Source
AI summary
A connection assembly and a method comprises first and second connector portions having a preload mechanism comprising a plurality of bores and threaded fixings circumferentially spaced around the axis, wherein the preload mechanism is arranged to apply an axial load between shoulders on the first and second connector portions when torque is applied to the threaded fixings. An annular sealing member is compressed between the first and second portions, and the axial load applied between the first and second shoulders by the preload mechanism exceeds a peak hydrodynamic load urging the first and second connector portions in a direction along the axis. The axial force applied by the preload mechanism advantageously reduces the fatigue damage experienced by the connection, for example, by cyclic pressure changes within the connector portions typically caused by pumps operating at high pressures.