Free point from pipe stretch
Length of the free pipe above the stuck point from the stretch measured for an increase in pull — an estimate of where tubing or drill pipe is stuck.
L = E · A · ΔL / ΔFA = π/4 · (D² − (D − 2t)²)E = 2.068·10⁵ MPa (30·10⁶ psi)The string is taken as uniform; for a tapered string work section by section from the bottom. Upsets, tool joints and couplings stiffen the string, so the result is an estimate; locate the stuck point exactly with a free-point tool. Keep the pull within the limits of the pipe and connections. Field form: L (ft) = 735 294 · ΔL (in) · w (lb/ft) / ΔF (lbf), w being the plain-end pipe weight.
Source: Hooke's law for a pipe in tension; field form L = 735 294 · e · w / ΔF — Lapeyrouse N. J., Formulas and Calculations for Drilling, Production and Workover (Gulf Professional Publishing)
Inputs
You can change a field's unit: the value is converted to the formula's units automatically.
Distance between the marks on the pipe at the rotary for two pulls, both above the free string weight.
Unit converter for this formulaLength · Force and load · Area
- m1
- cm100
- mm1,000
- km0.001
- ft3.28084
- in39.3701
- 1/32 in1,259.84
- 1/64 in2,519.69
- mile0.000621371
- A — Pipe body cross-section–
More in Tubing and stuck pipe
Stretch of a freely hanging string from an axial pull, from its own weight in fluid and from a temperature change, and the thermal force in a string fixed at both ends (e.g. on a packer).
Volume of a spotting fluid (oil, water or acid) that covers the stuck zone in the annulus with a reserve inside the pipe, the displacement volume, and the drop in bottomhole pressure caused by the lighter pill.
Results are engineering estimates from standard formulas; for design decisions check them against the codes, project documents and specialists' calculations. The formulas carried over from the original set are unchanged, and their errors are described in the notes.