Shearable Drill Collar Design for Blowout Prevention
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Solution Overview
Problem
The thick cross-section of high-strength steel drill collars cannot be sheared by conventional blowout preventer shear rams, posing a risk in deepwater drilling scenarios where unexpected pressure situations can lead to a blowout, as the drill collars cannot be cut or sealed effectively.
Innovation Solution
Designing drill collars with a thin-walled tube structure and adding heavy weight material like lead between the tube sections, which reduces the length required while maintaining the necessary weight on the drill bit, allowing them to be sheared by conventional shear rams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If drill collars are made of high-strength steel with thick cross-section to provide necessary weight and strength, then the weight on the drill bit is maintained, but the drill collars cannot be sheared by conventional blowout preventer shear rams
Solution Approach 1:
The drill collar is divided into two distinct sections: an upper section made of high-strength steel for structural integrity and connections, and a lower section made of lower-strength material that can be easily sheared by conventional blowout preventer shear rams. This segmentation allows each section to fulfill its specific function while resolving the contradiction between strength and shearability.
Solution Approach 2:
Different materials with different properties are used in different sections of the drill collar. The upper section uses high-strength steel for areas requiring strength (connections and upper structure), while the lower section uses lower-strength material specifically where shearing is needed, creating local quality differences that resolve the contradiction.
2Weight of moving object
If drill collars are made longer to provide sufficient weight on the drill bit, then the necessary weight is achieved, but the length increases the risk in deepwater drilling where unexpected pressure situations can occur
Solution Approach 1:
The material density parameter is changed by using lower-density material in the lower section of the drill collar. This allows the same weight to be achieved with a shorter length, or alternatively, the lower section can be made longer to provide shearability while the high-density upper section provides the necessary weight, thus resolving the contradiction between weight and length.
3Weight of moving object
If conventional drill collars with thick cross-section are used, then the weight on the drill bit is maintained, but the well bore cannot be closed in deepwater drilling situations when unexpected pressure situations occur
Solution Approach 1:
The drill collar is segmented into shearable and non-shearable sections, with the lower section designed to be sheared by conventional blowout preventer shear rams. This ensures that in deepwater drilling situations, the well bore can be closed reliably by shearing the drill collar at the appropriate location, resolving the reliability issue while maintaining necessary weight through the upper section.
Data Source
AI summary
The method of shearing drill collars used in the drilling of oil and gas wells, comprising providing an outer sleeve of a first material for carrying structural loads, providing a second material within the outer sleeve which is lower in shear strength and is greater in unit weight than the first material, and providing a hole in the second material for the circulation of fluids.