Flow Restrictor Elements for Oil Well Cementing Surge Control
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Solution Overview
Problem
Existing flow restrictors for controlling fluid flow in oil wells during cementing operations often lead to U tubing, causing turbulent or slow flow rates, erosion of formations, and pressure surges, which are exacerbated by deep water drilling conditions, and require multiple specifications for varying casing dimensions.
Innovation Solution
A flow restrictor device with slidingly received restrictor elements that define an indirect flowpath between the elements and the tubing, maximizing the direct flowpath diameter and minimizing surge effects, and featuring adaptable seals for various tubing diameters, allowing rapid installation and use in different casing types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flow restrictors are installed to control cement slurry flow and prevent U tubing, then fluid flow control is improved, but surge effects are exacerbated causing undesirable pressures on open formation
Solution Approach 1:
The flow restrictor is divided into multiple stacked elements, each defining a portion of the indirect flowpath. This segmentation allows the device to provide flow control while maintaining a larger overall structure that can accommodate a larger direct flowpath to reduce surge effects.
Solution Approach 2:
The indirect flowpath acts as an intermediary mechanism that provides controlled resistance to cement slurry flow without directly blocking the main flowpath. This mediator approach allows pressure control while avoiding the surge effects that would result from direct throttling.
2Productivity
If a large direct flowpath is provided to reduce surge effects, then installation speed is improved, but the device complexity increases requiring multiple specifications for varying casing dimensions
Solution Approach 1:
The flow restrictor elements are designed with adaptable seals that can conform to various tubing internal diameters. This universal design allows a single device specification to be used across multiple casing sizes, eliminating the need for multiple specifications while maintaining rapid installation.
Solution Approach 2:
The seal elements are designed to change their dimensional parameters (radial expansion) to adapt to different tubing diameters. This parameter change capability allows the same restrictor device to function universally across varying casing specifications without requiring multiple device variants.
3Reliability
If flow restrictors resist upward fluid flow through casing, then cement slurry flow control is improved, but pressure increases causing erosion of weak formations
Solution Approach 1:
The flow restrictor provides localized flow control at specific points within the casing, creating controlled resistance zones. This localized approach allows precise management of pressure gradients to prevent both U tubing and formation erosion by distributing pressure changes along the flowpath.
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 device effectively reduces U tubing and minimizes surge effects during cementing operations, enabling rapid installation and adaptability to different casing specifications, thus improving fluid flow control and reducing the risk of formation damage.
Implementation Method 1
Each first seal element comprises a split ring made from a resilient metal providing an integral restoring force. The resilient material radially outwardly biases the seal elements radially outwardly so as to adapt conformably to different tubing types having different internal diameters.
Implementation Method 2
flow restrictors may be installed in the tubing downhole so as to provide an indirect flowpath which limits the downward rate of flow of the cement. The indirect flowpath extends between each element and the wall of the casing portion.
Implementation Method 3
The cement slurry has a density which is greater than the density of the mud which it displaces. This can result in a phenomenon known as U tubing in which the force resisting the flow of cement is insufficient to allow the pumping pressure to be maintained and the cement slurry falls in the casing under the effect of gravity faster than the pumping rate.
Implementation Method 4
The end of the casing includes a non return valve which, when cementing is complete, prevents the cement from passing back up inside the casing.
Data Source
AI summary
A flow restrictor for controlling the flow of cement or other fluid in oil wells comprises a plurality of restrictor elements, each defining first and second apertures, which are assembled in a stacked configuration and slidingly inserted into the well casing or other tubing so that the first apertures define a direct flowpath, preferably including a non-return valve, and the second apertures define a second, indirect flowpath between the elements and the inner surface of the tubing. The elements include seals for fluidly sealing each element in the bore of the tubing which are preferably slidably retractable and resiliently radially outwardly biased so as to adapt conformably to different tubing types having different internal diameters. The restrictor may slide along the tubing in use.