Pipe Stretch Calculator
Calculate tubing and casing length changes from mechanical load, temperature, pressure (ballooning), and check for helical buckling using the Paslay-Dawson criterion.
Pipe & Loading Parameters
Total Length Change
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Mechanical Stretch
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Thermal Stretch
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Ballooning (Pressure)
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Buckling Shortening
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Buckling Status
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Cross-Sect. Area
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Axial Stress
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Paslay-Dawson Fcr
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Piston Force
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Length Change Breakdown
How this was calculated
Mechanical Stretch: ΔL = F × L / (E × A) where E = 30 × 10&sup6; psi (steel), A = cross-sectional area of pipe wall.
Thermal Stretch: ΔL = α × ΔT × L where α = 6.9 × 10&sup-6; in/in/°F for steel.
Ballooning: ΔL = (ΔPi × Ai - ΔPe × Ae) × 2ν × L / (E × A) where ν = 0.3 (Poisson's ratio), Ai/Ae = internal/external cross-sectional areas.
Paslay-Dawson Buckling: Fcr = sqrt(2 × E × I × w × sin(θ) / r) where I = moment of inertia, w = buoyed weight per foot, r = radial clearance. If net compressive force exceeds Fcr, helical buckling occurs.
Buckling Shortening: ΔL = -r² × F² / (4 × E × I × w) for helically buckled tubing (Lubinski).
Need completion design optimization, packer-to-tubing force analysis, or wellbore integrity assessment?
Book a free strategy call →Tubing & Casing Stretch in Well Operations
Understanding pipe length changes is critical for completion design, packer setting, and wellbore integrity. Tubing and casing strings experience length changes from four primary effects: mechanical loading (tension or compression from applied forces and pipe weight), thermal expansion or contraction (temperature changes during production, injection, or stimulation), ballooning (internal and external pressure changes cause radial deformation that couples to axial length change through Poisson's ratio), and buckling (when compressive forces exceed the critical buckling load).
The Paslay-Dawson equation gives the critical force for the onset of helical buckling in a confined pipe. Below this force, the pipe remains straight. Above it, the pipe buckles into a helical shape inside the casing or wellbore, causing shortening and increased contact forces. Severe buckling can lead to tubing lock-up, inability to circulate, or mechanical failure. For horizontal and deviated wells, the critical buckling force varies with inclination angle.
These calculations are essential for setting packer-to-tubing seal assemblies, determining tubing movement allowances, designing expansion joints, and evaluating the risk of tubing failure during stimulation or thermal operations (steam injection, SAGD, CSS). In operations with large temperature swings (e.g., steam injection where ΔT can exceed 400 °F), thermal effects can dominate and produce several feet of tubing movement.
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