Redundant Drill String Cutting System with Shaped Charge and Fluid Ablation
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Solution Overview
Problem
Deep earth drilling for fluid minerals like gas and oil often results in drill strings becoming seized due to friable formations collapsing or being washed away, leading to costly cutter failures and lengthy rig time for pipe cutting and removal.
Innovation Solution
A drill string assembly with strategically placed seating/sealing subs and a pair of cutters, including an explosive shaped charge and a fluid ablative cutter, where the cutters are delivered by free-fall or pumped transport to a selected cut-away sub, allowing for immediate cutting alternatives in case of shaped charge failure, using fluid pressure to initiate and complete the cut.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If an explosive shaped charge cutter is used for pipe cutting, then the cutting speed and reliability are improved, but the risk of cutter failure and costly downtime increases due to the critical nature of the single cutting attempt
Solution Approach 1:
The cutting system is divided into two independent cutting tools: an explosive shaped charge cutter for primary cutting and a fluid ablative cutter for backup or completion. This segmentation allows the system to maintain high speed while improving reliability through redundancy, as the tools can be deployed in sequence rather than relying on a single critical attempt.
Solution Approach 2:
The system prepares a backup cutting method (fluid ablative cutter) in advance to cushion against the potential failure of the primary explosive cutter. This prior cushioning ensures that if the shaped charge fails, there is an immediate alternative ready, preventing costly downtime and rig time loss.
2Device complexity
If a single explosive shaped charge cutter is deployed, then the device complexity is reduced, but the loss of time increases due to withdrawal and replacement procedures upon cutter failure
Solution Approach 1:
The cutting system is divided into two independent cutting tools: an explosive shaped charge cutter for primary cutting and a fluid ablative cutter for backup or completion. This segmentation allows the system to maintain high speed while improving reliability through redundancy, as the tools can be deployed in sequence rather than relying on a single critical attempt.
Solution Approach 2:
The system prepares a backup cutting method (fluid ablative cutter) in advance to cushion against the potential failure of the primary explosive cutter. This prior cushioning ensures that if the shaped charge fails, there is an immediate alternative ready, preventing costly downtime and rig time loss.
3Reliability
If strategic positioning of multiple cutters is implemented, then the reliability of successful pipe separation is improved, but the device complexity and initial cost increase
Solution Approach 1:
The cutting system is divided into two independent cutting tools: an explosive shaped charge cutter for primary cutting and a fluid ablative cutter for backup or completion. This segmentation allows the system to maintain high speed while improving reliability through redundancy, as the tools can be deployed in sequence rather than relying on a single critical attempt.
Solution Approach 2:
The drop sub assembly serves multiple functions: it positions the cutting tools, provides pressure containment, enables tool deployment, and facilitates cutter replacement. This multi-functionality reduces the need for separate specialized components, thereby limiting the increase in device complexity while achieving improved 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
Enables quick and reliable severing of the drill string, reducing costly downtime and rig time by providing a backup cutting method that ensures successful pipe separation even in deep or challenging geological conditions.
Implementation Method 1
one is an explosive shaped charge cutter
Implementation Method 2
explosive shaped charge or thermite are frequently used in the oil industry for down hole pipe cutting
Implementation Method 3
the other is a fluid ablative cutter
Implementation Method 4
pressure in the upper drill string is raised to make the desired cut by fluid flow through the nozzles
Implementation Method 5
Fluid pressure in the drop sub tube drives a firing head pin into a shaped charge initiation booster
Implementation Method 6
the cutters are delivered by free-fall or pumped transport to a selected cut-away sub
Data Source
AI summary
Downhole drill pipe cutting is achieved by a free-falling sub carrying a shaped charge cutter and an ablative fluid cutter. Upon seating on a drill string flow bore orifice, fluid pressure is raised to detonate the shaped charge cutter. In the event the shaped charge cutter fails, pressure is further raised to effect a cut by fluid ablation.