Stuck Pipe — Free Point Calculator
Estimate the depth at which your drillpipe is stuck using stretch test (overpull) data. Includes differential sticking force estimation.
Free Point Depth (Stretch Method)
Additional pull above free-hanging weight
Pipe elongation from overpull
Hookload before stuck (for reference)
Free Point = (Stretch × As × E) / (Overpull × 12)
Where E = 30×106 psi, As = π/4 × (OD² - ID²)
Estimated Free Point Depth
--
Cross-Section Area
--
in²
Stress Under Overpull
--
psi
Strain
--
in/in
Max Pull Applied
--
lbs
Differential Sticking Force Estimate
Estimate the force holding the pipe against the wellbore wall due to differential pressure.
Typically 1-3 in
Typically 0.05-0.15
Differential Pressure
--
psi
Contact Area
--
in²
Sticking Force
--
lbs
How this was calculated
Free Point Depth: L = (e × As × E) / (F × 12), where e = stretch (in), As = pipe cross-section area (in²), E = Young's modulus (30×106 psi), F = overpull (lbs), 12 converts ft to in.
Differential Sticking Force: Fstick = ΔP × Acontact × μfc, where ΔP = (MW - PP) × 0.052 × TVD, Acontact = contact length × arc width.
Assumptions: Uniform pipe properties. Elastic deformation only. Young's modulus E = 30×106 psi (steel).
Related Tool
Hydrostatic Pressure Calculator
Calculate wellbore pressures and safe drilling windows.
Open Hydrostatic Calculator →Related Tool
Torque & Drag Calculator
Estimate hookload and drag for drillstring operations.
Open T&D Calculator →Stuck pipe events can cost $100K-$1M+ per incident. Need help with stuck pipe prevention strategies, real-time monitoring, or fishing operation planning?
Book a free strategy call →Understanding Free Point Estimation
When drillpipe becomes stuck in the wellbore, determining the depth of the stuck point is critical for planning a fishing or backoff operation. The stretch test (also called the overpull test) is the most common field method for estimating the free point depth. By applying a known overpull force above the free-hanging weight of the string and measuring the resulting pipe elongation (stretch), the free length of pipe can be calculated using basic elasticity principles.
The formula relies on Hooke's Law: the stretch of a pipe under axial load is proportional to the load and the free length, and inversely proportional to the cross-sectional area and Young's modulus. Steel drillpipe has a well-known modulus of elasticity (approximately 30 million psi), making this calculation straightforward once the overpull and stretch are measured.
Differential sticking occurs when the drillstring is pressed against a permeable formation by the differential pressure between the mud column and the formation pore pressure. The sticking force depends on the differential pressure, the contact area between pipe and formation, and the friction coefficient of the filter cake. Reducing overbalance, keeping pipe moving, and using low-friction filter cake additives are key prevention strategies.
All calculations run in your browser. Built by Groundwork Analytics. Get in touch or email info@petropt.com.