Vibratory Casing Recovery Bottom Hole Assembly
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for well abandonment and casing recovery are inefficient due to stuck casings caused by drilling fluid sediments and cement, requiring multiple trips and excessive time and cost, with current vibration techniques failing to effectively transfer energy to stuck casings due to low dynamic amplification factors.
Innovation Solution
A vibratory casing recovery method that tunes elements of the bottom hole assembly to resonate at a frequency matching the flow modifier, using a casing spear, flow modifier, and extension/retraction means to induce cyclic variations and maximize tension on the stuck casing, enhancing the dynamic amplification factor and energy transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional pulling methods are used to recover stuck casing, then the equipment complexity is low, but the productivity is reduced due to multiple trips being required
Solution Approach 1:
The patent applies mechanical vibration by incorporating a vibratory unit in the bottom hole assembly that generates high-frequency vibrations to agitate and dislodge stuck casing from the wellbore. This vibration mechanism enables single-trip recovery of longer casing sections, significantly improving productivity while the modular design keeps the added complexity manageable
Solution Approach 2:
The vibratory unit operates through periodic cyclic motion, creating repeated vibration cycles that progressively work loose stuck casing. This periodic action allows the system to overcome static friction and binding materials without requiring multiple separate pulling operations, thus reducing the number of trips needed
2Productivity
If vibration is applied to free stuck casing, then the productivity improves by reducing trips, but the energy transfer efficiency is low due to insufficient dynamic amplification
Solution Approach 1:
The patent employs parameter changes by tuning the vibratory unit's frequency to match the natural frequency of the stuck casing section, creating resonance conditions. This frequency matching maximizes the dynamic amplification factor, ensuring that vibrational energy is efficiently transferred to the casing rather than being dissipated, thereby improving energy utilization while reducing the number of trips required
3Device complexity
If shock subs with springs are used for vibration, then the device complexity is low, but the natural frequency is orders of magnitude lower than required for effective vibration
Solution Approach 1:
The patent changes the spring constant parameter in the vibratory unit to adjust the natural frequency of the system. By selecting appropriate spring stiffness values, the system's natural frequency is raised from the low frequencies of conventional shock subs to the higher frequencies (10-100 Hz) needed for effective casing vibration, while maintaining the simple spring-mass-damper structure
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 method allows for the efficient recovery of longer casing lengths by maximizing vibrational energy transfer, effectively dislodging stuck casings and reducing the number of trips required, thereby minimizing time and cost.
Implementation Method 1
a flow modifier for producing cyclic variations at a first frequency in the flow of fluid through the string, and one or more elements, the one or more elements including an extension and retraction means for location in the string and adapted to axially extend or contract in response to variations in the flow of fluid through the string
Implementation Method 2
at least one element is configured to have a natural frequency in the assembly when vibrated wherein: 0.6 < Ω/ω < 1.2
Data Source
AI summary
A method of recovering casing in a wellbore using a vibratory casing recovery bottom hole assembly. In a vibratory casing recovery bottom hole assembly having a casing spear, a flow modifier and one or more further elements including a shock sub. The flow modifier produces cyclic variations in fluid flow through the assembly at a first frequency and at least one of the elements is configured to have a natural or resonant frequency when vibrated to be near or at the first frequency. By tuning elements of the bottom hole assembly to be close or at the frequency of the output of the flow modifier, the dynamic amplification factor of the system is maximised and longer lengths of casing can be recovered. A method of recovering casing using the vibratory casing recovery bottom hole assembly is also described. Further embodiments include a casing cutter and a hydraulic jack.