Flat-Faced Shear Bolt Structure for Torque-Resistant Whipstocks
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Solution Overview
Problem
Conventional single-trip whipstock designs for multilateral wells face premature shear bolt failure due to torque, leading to increased costs and reduced efficiency in drilling operations.
Innovation Solution
The design incorporates a shear bolt with a reduced cross-sectional area notch and opposing flat faces, which reduces stress concentrations and enhances resistance to torsional forces, allowing for controlled shearing under axial loads while maintaining structural integrity during torque transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the shear bolt is designed with features that facilitate shearing (reduced cross-sectional area), then the shear bolt can shear upon assuming a particular set down weight in the axial direction, but the shear bolt becomes susceptible to premature shearing in torque due to fatigue
Solution Approach 1:
The shear bolt incorporates a reduced cross-sectional area notch at a specific location to enable controlled shearing under axial loads, while the remaining portions of the bolt maintain full cross-sectional area to provide enhanced torque resistance. This local differentiation allows the bolt to have different mechanical properties in different regions, facilitating shearing at the notch while resisting torque elsewhere.
Solution Approach 2:
The shear bolt features an asymmetric cross-sectional geometry with a notch that creates a preferred shearing plane. The notch breaks the symmetry of the bolt's cross-section, making it susceptible to shearing in the axial direction while maintaining asymmetrical stress distribution that enhances torque resistance in the rotational direction.
2Ease of manufacture
If conventional shear bolts are used without flat faces, then manufacturing is simpler, but stress concentrations occur during torque transmission leading to premature failure
Solution Approach 1:
The shear bolt incorporates flat faces at specific locations along its length, creating regions with different geometric properties. These flat faces reduce stress concentrations during torque transmission by providing larger surface areas for stress distribution, while the notched region maintains its reduced cross-section for controlled shearing. This localized geometric modification balances manufacturing feasibility with enhanced torque resistance.
Data Source
AI summary
Certain shear bolts described herein provide failure bending resistance when torque is applied to members being connected by the bolts, while maintaining shearability. Certain other shear bolts described herein provide a shear region having different shear limits dependent upon the direction of force being applied to the shear region.