SnubCalc help and methodology
SnubCalc combines a snubbing calculator, pipe-data reference and an interactive BHA/BOP staging simulator. This guide describes the calculations and models currently implemented; it does not certify a field procedure or equipment rating.
Calculator inputs and units
Use the unit printed beside each control. Surface pressure is entered in kPa; annular pressure is in psi. Tubing depth and true vertical depth (TVD) are metres. Fluid density is kg/m³, tubing and hanger diameters are inches, and friction is a percentage.
The tubing selector uses fixed data for 2⅜, 2⅞ and 3½ inch tubing. Weight, inside diameter and collar diameter come from that selection. Pipe Data displays results for the same calculator inputs; it is not a separate set of editable pipe specifications.
What the calculations do
- Hydrostatic pressure uses density × gravity × TVD, converted to kPa. Bottom-hole pressure adds the entered surface pressure.
- Snub force combines pressure acting on the tubing outside area with the existing annular-drag estimate. Fluid selection and friction affect the effective tubing-weight calculation used for length to snub.
- J55/L80 strength and collapse estimates use the selected tubing dimensions and the fixed grade values in the calculator.
- Buckling uses Euler or Johnson calculations selected by slenderness. The displayed strength and buckling safety results use the existing application factors.
- Pipe capacity, displacement and connection-torque estimates retain allowances calibrated to the original workbook sample. They are not a substitute for a manufacturer's connection torque or pipe-performance table.
The calculation code retains its original workbook conventions, including a 9.6 m joint length, steel density of 7,850 kg/m³ and elastic modulus of 29,500,000 psi. Gravity defaults to 9.80665 m/s². These fixed assumptions are not independent user controls. Use the displayed units and verify the suitability of the assumptions against the actual job, tubular specification and approved procedure.
Using BHA/BOP staging
Open Staging to assemble the stack and BHA. Build / Size Components lets you add, remove, reorder and size available components. The model loads when the staging view becomes visible.
Move the BHA with the slider or switch to 10 cm or 1 cm steps. Zero sets the reference for net pipe-down travel. Camera pan, rotate and fit controls change the view without changing the engineering setup. Cutaway switches the view of the same components.
Click the annular or individual ram cavity to change its state. Ordinary closed rams stop movement; stripping rams allow matching tubing until an upset or coupling reaches them. These interactions model the application's existing constraints, not a complete well-control sequence.
Model sources and limits
SnubCalc models combine supplied CAD, measured or user-specified dimensions and reconstructed visual details. Some snubbing-unit details were reconstructed from photographs. X/XN landing nipples use the supplied reference dimensions and tubing connections. A rendered component is not a certified manufacturing drawing or proof that real equipment is compatible.
Use current manufacturer drawings, connection specifications, pressure ratings and your approved operating procedure for actual equipment. The source repository documents model provenance and regeneration alongside the CAD generators; original CAD files are excluded from the public website.
Keep a copy of your setup
Staging autosaves configuration in this browser on this device. Use Export setup to download a JSON backup and Import setup to validate and restore it. Import shows a preview before replacement. Transient positions, zero references and closed barriers reset on import.
Clearing browser storage or changing devices can remove local saves. If you previously used the address without “www”, use Recover a setup saved on snubcalc.com on that same device and browser.
Feedback and privacy
The Comments section accepts public feedback. Do not post private job information. Optional analytics counts the controls used, without sending their engineering values. See Privacy or change your choice using Analytics settings below.