Formation Saver Sub Anti-Surge Pressure Management
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional pump out subs are susceptible to formation surge due to differential pressures required to release the plug, necessitating an improved design that reduces or eliminates this issue while allowing for multiple pressure increases and dual packer applications.
Innovation Solution
The formation saver sub incorporates a tubular body with a mandrel, piston, and sleeve system, featuring shear pins and a spring mechanism that allows for controlled pressure management, enabling the sub to bleed off tubing pressure before releasing the plug and seat, and includes a retractable dog system for backup contingency, accommodating both ball and dart systems and dual packer applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pump out subs are used to increase well tubing pressure, then the well tool can be actuated, but formation surge occurs due to differential pressures required to release the plug
Solution Approach 1:
The pump out sub is divided into separate functional components: a plug for sealing, a seat for receiving the plug, a piston for pressure actuation, and a shear pin for controlled release. This segmentation allows each component to perform its specific function independently, enabling pressure buildup for tool actuation while controlling the release process to minimize formation surge.
Solution Approach 2:
The shear pin is pre-positioned to shear at a predetermined pressure level, automatically initiating the release sequence before the operator needs to manually intervene. This preliminary action ensures controlled pressure reduction that minimizes formation surge while maintaining well tool actuation reliability.
2Stress or pressure
If high pressure is applied to release the plug and seat, then the well tubing pressure increases, but formation surge is caused by rapid pressure changes
Solution Approach 1:
The pressure buildup and release process is performed in controlled periodic cycles rather than continuous rapid changes. The shear pin releases pressure in controlled increments as the piston moves, creating a periodic action that builds pressure sufficiently for tool actuation while avoiding the harmful rapid pressure changes that cause formation surge.
Solution Approach 2:
The piston acts as an intermediary mechanism between the pressure source and the plug/seat assembly. It provides controlled mechanical movement that mediates the pressure changes, allowing gradual pressure buildup and release rather than abrupt changes, thereby minimizing formation surge while achieving necessary pressure levels.
3Device complexity
If a simple plug release mechanism is used, then the device complexity is reduced, but the capability to manage multiple pressure increases and backup contingencies is limited
Solution Approach 1:
The pump out sub integrates multiple functions into a single device: plug sealing, pressure buildup, tool actuation, controlled pressure release, and backup contingency mechanisms. The shear pin provides both primary pressure-controlled release and backup contingency functionality, while the piston handles both pressure buildup and controlled release operations, achieving multi-functionality without excessive complexity.
Solution Approach 2:
The shear pin is designed to shear at a predetermined pressure level, providing a built-in safety mechanism that prevents excessive pressure buildup. This beforehand cushioning protects the system from over-pressurization while maintaining the necessary pressure for tool actuation, adding reliability without significant complexity increase.
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
This design effectively reduces formation surge, allows for multiple pressure increases, and ensures reliable actuation of well tools by controlling fluid pressure, ensuring efficient operation and reduced obstruction in the well tubing.
Implementation Method 1
a spring mechanism that allows for controlled pressure management
Implementation Method 2
shear pins and a spring mechanism that allows for controlled pressure management
Implementation Method 3
enabling the sub to bleed off tubing pressure before releasing the plug and seat
Data Source
AI summary
A formation saver sub or pump out sub incorporating an anti-surge feature. The sub includes a body, a mandrel, a piston (or an annulus fluid pressure chamber and a tubular pressure chamber), a sleeve, a spring, a releasable seat, and a plug. The plug and seat are released from the sub when one or more dogs releasably positioning the seat in the mandrel bore disengages from the seat due to a bleed off of fluid pressure in the well bore.