Firing Head Assembly for Horizontal Well Displacement Perforations
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Solution Overview
Problem
In horizontal wells, logging tools cannot be effectively pumped down due to the absence of an open annulus surrounding the casing, preventing cased-hole logging and requiring expensive and slow methods like tractor-assisted logging with high voltages.
Innovation Solution
Forming displacement perforations through the conduit and surrounding cement using a firing head assembly with a sealed chamber, piston, and detonator, allowing a pump-down logging tool to be used by displacing fluid into the formation, eliminating the need for tractors and high voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pump-down logging is used in horizontal wells, then logging efficiency and cost-effectiveness improve, but the absence of an open annulus surrounding the casing prevents fluid displacement and tool movement
Solution Approach 1:
The patent divides the conduit into segments by creating displacement perforations at specific locations. These perforations allow fluid to be displaced from one segment to another, enabling the pump-down tool to move through the conduit despite the absence of an open annulus. The segmentation approach transforms the continuous fluid displacement problem into manageable discrete segments.
Solution Approach 2:
The patent introduces displacement perforations as an intermediary mechanism between the pump-down tool and the formation. These perforations serve as a mediator that allows fluid to escape from the conduit into the formation, creating the necessary pressure differential to drive the tool downward without requiring an open annulus.
2Ease of operation
If tractor-assisted logging is used in horizontal wells, then logging can be performed, but operational cost and time increase significantly
Solution Approach 1:
The patent replaces the complex mechanical tractor system with a simpler pump-down mechanism. Instead of using a motor-driven tractor to physically move the logging tool, the system uses fluid pressure differential created by displacement perforations to push the tool through the conduit. This substitution eliminates the need for high-voltage power systems and complex mechanical drive mechanisms.
Solution Approach 2:
The patent employs hydraulic principles by using fluid pressure to move the logging tool. The pump-down tool utilizes the pressure differential created when fluid is displaced through the perforations into the formation. This hydraulic approach is far simpler and more efficient than the mechanical tractor system, reducing both operational time and cost.
3Ease of operation
If displacement perforations are formed before logging, then pump-down logging becomes feasible, but additional perforation operations are required
Solution Approach 1:
The patent merges the perforation operation with the logging operation by using the same conduit access for both purposes. The displacement perforations are created as part of the well completion process, and the same conduit is then used for both logging and potential production. This consolidation eliminates the need for separate perforation trips and reduces overall operational complexity.
Solution Approach 2:
The conduit serves multiple functions: it acts as both the logging pathway and the production flow path. The displacement perforations serve dual purposes by enabling both the pump-down logging operation and potential future production operations. This multi-functionality reduces the need for additional specialized equipment and operations.
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 efficient and cost-effective cased-hole logging in horizontal wells by allowing the use of pump-down logging tools, reducing operational time and expenses, and providing accurate formation surveys without the need for additional perforation trips or tractors.
Implementation Method 1
The downward movement of the pump-down head causes some of the fluid below the pump-down head to be displaced out through the displacement perforation into the formation
Implementation Method 2
The operator secures the sub to the string of conduit as it is being lowered into the wellbore. After cementing, the operator lowers a drill bit into the conduit and drills out cement left in the sub and in the lower portion of the conduit. The drill bit ruptures the sealed chamber of the firing head assembly, which exposes the sealed chamber to drilling fluid pressure. The fluid pressure causes the piston to drive the firing pin against the detonator, thereby detonating the perforating charge.
Data Source
AI summary
A firing head assembly has a sealed chamber containing a piston, a firing pin, and an impact detonator. The firing head assembly and a perforating charge are installed within a sub and the sub is secured into a string of conduit being lowered into a wellbore. After cementing the conduit, the operator drills out the cement in the conduit, disintegrating the chamber and exposing the sealed chamber to the fluid pressure of the drilling fluid in the conduit. The drilling fluid pressure causes the piston to drive the firing pin against the detonator, which detonates the perforating charge. The operator then pumps down a logging tool to survey the well. Fluid in the conduit below the pump-down head can flow out the displacement perforation into the earth formation while the logging tool is moving downward.