Bottom Hole Firing Head Pressure Segmentation
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Solution Overview
Problem
Existing methods for detonating downhole explosives in well perforating guns often subject the entire well environment to increased fluid pressure, which can inhibit shaped charge detonations and potentially damage the perforating gun or casing, especially in deep wells.
Innovation Solution
A fluid pressure activated firing head using a piston-cylinder mechanism with a safety sub and venting apertures to prevent premature detonation, ensuring that the activation pressure is generated only at the desired depth and does not exceed the in-situ well pressure, thereby avoiding unnecessary stress on the gun and casing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fluid pressure is used to activate the firing head, then the shaped charges can be detonated effectively, but the increased pressure may inhibit detonation and damage the gun or casing in deep wells
Solution Approach 1:
The system divides the wellbore environment into two separate pressure zones: the activation chamber where high pressure is generated locally to detonate the firing head, and the surrounding well environment where pressure remains at in-situ levels. This segmentation is achieved by containing the pressure-generating piston mechanism within a localized chamber isolated from the external wellbore pressure
Solution Approach 2:
A piston mechanism acts as an intermediary between the low-pressure well environment and the high-pressure detonation requirement. The piston converts the mechanical force from the gun's weight into localized high pressure within the activation chamber, mediating the transition without transmitting excessive pressure to the surrounding gun and casing
2Object-affected harmful factors
If the gun weight is used to activate the piston, then no additional pressure is imposed on the well environment, but premature detonation may occur during descent
Solution Approach 1:
The system performs preliminary preparation by positioning the piston and sealing elements in advance, but delays the actual detonation action until the correct moment. The piston is pre-loaded with the gun's weight, but the sealing that traps pressure and enables detonation only occurs when the venting apertures are closed by the wellbore pressure at the target depth
Solution Approach 2:
The system uses feedback from the wellbore pressure environment to control the detonation timing. The wellbore pressure acts on the piston sleeve to close the venting apertures, providing feedback that confirms the system has reached the appropriate depth and pressure conditions for safe detonation
Data Source
AI summary
Detonation of a perforating gun is initiated by engagement of the lower distal end of the gun assembly against a bottom hole bore plug. A fluid pressure actuated firing head is initiated by well fluid that is pressurized by a free piston having an integral rod projecting from the distal end of the gun assembly. The piston is displaced against a closed fluid volume when the projecting rod engages the bore plug.