Drillstring stretch is the elongation of the drillstring under tension when it is subjected to axial forces during drilling operations.
Drillstring Stretch Formula
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\( \Delta L \;=\; \dfrac{ F \cdot L \cdot 12 }{ \lambda \cdot A_c } \) (Drillstring Stretch) \( F \;=\; \dfrac{ \Delta L \cdot \lambda \cdot A_c }{ L \cdot 12 } \) \( L \;=\; \dfrac{ \Delta L \cdot \lambda \cdot A_c }{ F \cdot 12 } \) \( \lambda \;=\; \dfrac{ F \cdot L \cdot 12 }{ \Delta L \cdot A_c } \) \( A_c \;=\; \dfrac{ F \cdot L \cdot 12 }{ \Delta L \cdot \lambda } \) |
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| Symbol | English | Metric |
| \( \Delta L \) = Stretch Length | \(in\) | - |
| \( F \) = Pull Force | \(lbf\) | - |
| \( L \) = Pipe Length | \(ft\) | - |
| \( \lambda \) (Greek symbol lambda) = Elastic Modulus (psi) | \( lbf \;/\; in^2 \) | - |
| \( A_c \) = Area Cross-section | \( in^2 \) | - |
