Work out how much a pipe string stretches elastically under an applied pull — useful for space-out, stuck-pipe work and free-point estimates.
Steel is elastic — pull on a pipe string and it stretches, then springs back when you let off. The amount of stretch for a given pull depends on how long the free pipe is and how much steel is in the wall. This is the basis of the free-point measurement in stuck-pipe work: you pull a known extra load, measure how far the block moves, and back out how much pipe is free to stretch.
It also matters for space-out and for interpreting weight indicator readings when setting tools.
Pull in lbs, length in ft (×12 converts to inches), area is the steel cross-section in in², and E is Young's modulus for steel, 30 × 10⁶ psi. If you only have pipe weight in lb/ft, steel area ≈ weight / 3.4.
Elastic (Hooke's law) stretch only — valid below the pipe's yield. Assumes a uniform single-size string; for tapered strings, sum each section separately.
Pulling 50,000 lbs on 8,000 ft of pipe with 5.275 in² of steel: stretch = (50,000 × 8,000 × 12) / (5.275 × 30,000,000) ≈ 30.3 in, or about 2.5 ft.
Completion and workover engineering support — tubular selection, load cases and more.