Perforating Safety Apparatus with Rotatable Ballistic Section
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Solution Overview
Problem
Existing safety systems for perforating operations, such as tubing conveyed perforating (TCP), face challenges in preventing accidental detonation of firing heads during attachment or removal, particularly due to insufficient pressure at the surface and issues with eutectic materials melting and flowing away, which can lead to safety hazards and property damage.
Innovation Solution
A safety apparatus that includes a tubular housing with rotatable ballistic sections and an annular piston, which is initially misaligned to prevent detonation at the surface and aligns only under downhole pressure, ensuring the ballistic train can detonate downhole but returns to a safe position upon retrieval, featuring a frangible rupture disc for permanent disarmament.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If eutectic material is used to block the firing pin at the surface, then safety during surface operations is improved, but the material melts and flows away when run downhole, causing the safety mechanism to fail
Solution Approach 1:
The invention changes the physical state parameter of the blocking mechanism. Instead of using eutectic material that changes state with temperature, the patent uses a spring-loaded blocking pin that is mechanically held in place by well pressure. The parameter changed is from temperature-dependent material properties to pressure-dependent mechanical locking, resolving the stability issue while maintaining safety functionality.
Solution Approach 2:
The invention replaces the thermal/eutectic mechanical system with a purely mechanical spring-loaded system. The spring-loaded pin provides mechanical blocking that is controlled by well pressure rather than temperature-dependent material melting, substituting one mechanical principle for another more reliable one.
2Ease of operation
If the firing head is installed on the rig floor with personnel nearby, then ease of operation is improved, but the risk of severe property damage and bodily harm increases if detonation occurs
Solution Approach 1:
The invention applies preliminary anti-action by pre-installing a safety apparatus between the firing head and gun string before any detonation risk exists. The spring-loaded blocking pin is pre-positioned to automatically prevent ballistic train transfer if accidental detonation occurs during surface operations, counteracting the harmful effect before it can manifest.
Solution Approach 2:
The safety apparatus acts as an intermediary component between the firing head and gun string. This intermediate device with its spring-loaded blocking pin provides a protective barrier that allows easy installation of the firing head while preventing direct transmission of detonation forces to personnel and equipment.
3Reliability
If a radial blocking pin held by a spring is used to interrupt the ballistic train, then safety is improved, but the pin moves to a clear position under downhole pressure, allowing detonation
Solution Approach 1:
The invention inverts the conventional approach by making the blocking mechanism default-active (blocking by spring) and requiring pressure to disengage it, rather than having it default-passive and requiring a trigger to engage. This inversion ensures safety by default while allowing controlled detonation when needed, resolving the contradiction between safety and operational capability.
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 apparatus effectively prevents accidental detonation during surface operations by ensuring the ballistic train is only armed downhole and disarmed upon retrieval, enhancing safety by maintaining the firing head below the perforating guns and providing a mechanism for permanent disarmament.
Implementation Method 1
a compression spring, when there is no pressure on the safety apparatus... holds the third ballistic section in a position that is misaligned with the first and second ballistic sections
Implementation Method 2
As apparatus in accordance with the present invention is run into the hole, downhole pressure forces the annular sealed piston against the compression spring... the third ballistic section is rotated into alignment with the first and second ballistic sections
Implementation Method 3
a frangible member such as a rupture disc... Once the rupture disc has burst, further fluctuations of well pressure have no effect on the annular piston position and the third ballistics section will permanently remain in a misaligned position
Data Source
AI summary
Safety apparatus is disclosed for providing ballistic train interruption in a perforating system. The safety apparatus comprises a generally tubular shaped housing having first and second ends which are fabricated to permit the housing to be positioned at any location in the perforating system. The apparatus comprises first and second ballistic sections in the housing and a third ballistic section which is rotatably mounted in the housing to move between a disarmed position and an armed position based on downhole pressure. Upon retrieval of the perforating system from the wellbore, the safety apparatus functions to return a third ballistic section to its disarmed position. Additionally, apparatus is provided to permanently disable the third ballistic section to insure that no inadvertent detonation of the guns occurs when retrieving the system from a wellbore.