Flapper Disk Buoyancy Tool for Reducing Casing Drag
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Solution Overview
Problem
Running well casing to the desired depth in deviated or horizontal well bores is challenging due to high casing drag, which creates significant friction and can result in the casing becoming stuck before reaching the intended location.
Innovation Solution
A buoyancy chamber is created within the casing using a fluid lighter than the well bore fluid, such as air or a gas like nitrogen, to reduce drag and facilitate easier placement by utilizing a buoyancy assist tool with a float device and a flapper disk mechanism that allows fluid flow downward but prevents upward flow until additional pressure is applied, allowing the buoyant fluid to be released.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If long lengths of casing are used to reach the desired depth in deviated or horizontal well bores, then the casing can reach the toe of the well bore, but significant friction and casing drag occur making it difficult to run the casing to the desired depth
Solution Approach 1:
The patent applies buoyancy as a counteracting force to offset the weight of the casing. A buoyancy chamber is created within the casing string, filling with well bore fluid while displacing an equal volume of casing material. This reduces the effective weight of the casing string, thereby reducing friction and drag forces that oppose casing movement during installation in deviated or horizontal well bores.
Solution Approach 2:
The patent introduces a buoyancy assist tool as an intermediary device between the casing string and the well bore environment. This tool includes a float device and flow control mechanism that mediates the interaction between the casing and well bore fluid, enabling controlled filling of the buoyancy chamber and subsequent reduction of casing drag during running operations.
2Ease of operation
If a buoyancy chamber is created in the casing to reduce drag, then it becomes easier to overcome friction and run the casing to the desired depth, but additional mechanisms are needed to control fluid flow and maintain buoyancy
Solution Approach 1:
The buoyancy assist tool employs a float device that automatically responds to fluid level changes within the buoyancy chamber. As the chamber fills with well bore fluid, the float rises and automatically triggers the flow control mechanism to open, allowing excess fluid to escape and maintaining the desired buoyancy level without requiring external control systems.
Solution Approach 2:
The patent utilizes hydraulic principles through the float device mechanism, which responds to changes in fluid level and pressure within the buoyancy chamber. The float device converts hydraulic pressure changes into mechanical motion that actuates the flow control mechanism, enabling automatic regulation of fluid flow and buoyancy maintenance through fluid-mechanical coupling.
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 buoyancy chamber significantly reduces friction, enabling the casing to reach the desired depth without becoming stuck and allows for the passage of other tools through the well bore without obstruction once the casing is in place.
Implementation Method 1
Creating a buoyant chamber in the casing utilizing air or a fluid lighter than the well bore fluid can reduce the drag making it easier to overcome the friction and run the casing to the desired final depth
Implementation Method 2
The float devices are generally a one-way check valve. The float device 30 is thus a fluid barrier that will be configured such that it will hold the buoyant fluid in the buoyancy chamber 26 until additional pressure is applied
Data Source
AI summary
A buoyancy assist tool and a fluid barrier in a casing string define a buoyancy chamber therebetween. The buoyancy assist tool has a housing connected in the casing string with a retaining sleeve detachably connected in the housing. The retaining sleeve is movable from a first to a second position in the housing. A flapper disk is positioned in the housing and covers an upper end of the retaining sleeve in the first position of the retaining sleeve. In the second position of the retaining sleeve the flapper disk is in a retracted position out of the flow path through the housing.