Vented Explosive Pellet Tube for Deep Well Pipe Joint Release
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Solution Overview
Problem
Existing methods for decoupling or unthreading drill collar or pipe joints in deep well drilling face challenges in high temperature and pressure conditions, where traditional explosive devices fail to provide sufficient explosive energy and accuracy for successful joint release, especially at great depths.
Innovation Solution
A downhole mini-severing and back-off tool apparatus comprising a firing head, initiation body, and explosive pellet tube, with a detonator and booster explosive, and a pellet tube with vented apertures to equalize pressure, and a coil spring to bias explosive pellets into detonation proximity, allowing for precise explosive distribution and moderate torque application for joint disassembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional explosive devices are used in deep well drilling, then the device structure is simple, but the explosive energy is insufficient and the reliability is poor under high temperature and pressure conditions
Solution Approach 1:
The explosive device is divided into multiple segments: a detonator, a booster explosive charge, and multiple explosive pellet charges arranged in a tube. This segmentation allows each component to perform its specific function optimally - the detonator initiates the booster, which then propels the pellets against the pipe joint, providing reliable operation under high temperature and pressure conditions while maintaining manageable device complexity
Solution Approach 2:
The explosive pellets are pre-loaded into the tube with the booster explosive positioned at one end. The biasing mechanism is pre-configured to propel the pellets toward the booster. This preliminary arrangement ensures that when the detonator is activated, the entire explosive sequence operates automatically and reliably without requiring complex real-time control mechanisms
2Use of energy by moving object
If high pressure is applied to ensure explosive energy, then the explosive energy is sufficient, but the pressure balance is disrupted and the device cannot function properly
Solution Approach 1:
The tube with vented apertures acts as an intermediary between the high-pressure explosive reaction and the downhole environment. The vented apertures allow external downhole pressure to equalize with the internal pressure, preventing pressure imbalance that would disrupt device function while still containing and directing the explosive energy effectively against the pipe joint
3Manufacturing precision
If precise explosive distribution is implemented, then the manufacturing precision is high, but the device complexity increases
Solution Approach 1:
The explosive pellets are distributed locally at specific positions along the tube rather than uniformly throughout. The biasing mechanism ensures pellets are positioned at optimal locations where they can effectively engage the pipe joint. This local quality approach achieves precise explosive distribution for maximum effectiveness without requiring complex distribution systems
4Force
If moderate torque is applied for joint disassembly, then the force required is low, but the productivity is reduced
Solution Approach 1:
The explosive device delivers energy in a concentrated periodic impulse rather than continuous force. The detonation and subsequent pellet impact create a sudden, high-intensity shock wave that rapidly breaks the joint seizure, allowing moderate torque to complete the disassembly. This periodic action achieves quick joint release without requiring sustained high torque, thereby maintaining productivity
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
Enables effective decoupling of threaded pipe joints in high-pressure and high-temperature environments by ensuring sufficient explosive energy and pressure balance, overcoming limitations of prior art methods in deep well drilling.
Implementation Method 1
a detonator in ignition proximity to a booster explosive, and a tube secured in the initiation housing and comprising a plurality of explosive pellets in contiguous alignment
Implementation Method 2
detonating the plurality of explosive pellets with the booster explosive for disassembling the pipe string
Implementation Method 3
a pellet tube with vented apertures to equalize pressure
Data Source
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AI summary
A mini-severing and back-off tool includes a tubular magazine for a column of explosive pellets that are sized in diameter to provide a predetermined weight of explosive per unit column length. The tubular wall is vented at prescribed intervals for fluid pressure equalization between the internal bore of the tubular and the fluid pressure around the outside of the tubular. A fluid barrier is positioned between one end of the explosive pellet tubular and a detonator or an explosive booster provided to detonate the explosive pellet tubular. The explosive pellet tubular is positioned within the flow bore of a pipe string and adjacent to an intended pipe joint, and the explosive pellet tubular is detonated simultaneously with an application of torque on the pipe string, wherein the torque is applied in the thread release direction to disassemble the intended pipe joint.