Coiled Tubing Calculators
Five calculators for coiled tubing operations, all from OD and wall thickness. Results update instantly, in field or SI units.
Educational quick-check calculators: not an approved procedure and not a substitute for your company software or a qualified engineer’s review.
Pipe capacity and displacement
ID, internal capacity, closed- and open-end displacement, steel area and weight per foot.
How it is calculated
Capacity (bbl/ft) = ID² / 1029.4
Closed-end displacement = OD² / 1029.4 ; steel displacement = (OD² − ID²) / 1029.4
As = (π/4)(OD² − ID²) ; W (lb/ft) = 10.69 · (OD − t) · t = 3.4032 · As
Assumptions
- Nominal dimensions: the actual wall varies within manufacturing tolerance and thins with use.
- 1029.4 comes from 1 bbl = 9,702 in³. Weight is plain steel tube without connectors or coating (0.2836 lb/in³).
Worked example
1.75 × 0.134 in, 15,000 ft → ID = 1.482 in, capacity = 1.482²/1029.4 = 0.002134 bbl/ft, volume = 32.00 bbl, As = 0.6803 in², weight = 2.315 lb/ft.
Sources: API Spec 5ST (coiled tubing dimensions) · API Spec 5L / 5CT plain-end weight formula w = 10.69 (D − t) t · Halliburton Cementing Tables (capacity constant 1029.4) · Tenaris Coiled Tubes / Global Tubing technical data sheets (compare with your string)
Educational quick-check tool, not an approved procedure. Follow your company procedures and the manufacturer’s data.
Volume to nozzle and bottoms up
Internal volume of the whole string (including the wraps on the reel) to reach the nozzle, then the annulus back to surface.
How it is calculated
V_ann = (D_well² − OD²) / 1029.4 × Depth
t = V / Q
Assumptions
- One wellbore ID down to the nozzle; for a tapered completion add the sections.
- Returns equal the pump rate (no losses, no gas). Depth is measured depth (MD).
Worked example
1.75 × 0.134 in, 16,000 ft on the reel, nozzle at 10,000 ft inside 2.992 in tubing, 2.0 bbl/min → CT = 34.14 bbl (17.1 min), annulus = (2.992² − 1.75²)/1029.4 × 10,000 = 57.21 bbl (28.6 min), full circulation = 91.35 bbl (45.7 min).
Sources: Halliburton Cementing Tables (capacities) · ICoTA — An Introduction to Coiled Tubing (volumes and circulation)
Educational quick-check tool, not an approved procedure. Follow your company procedures and the manufacturer’s data.
Free point from stretch
Free length above the stuck point from the pull difference and measured stretch (Hooke’s law).
How it is calculated
As = (π/4)(OD² − ID²)
FPC = E · As / 12,000 → L = ΔL × FPC / ΔF(klbf)
Assumptions
- Take the first reading after pulling above the hanging weight (Tenaris: at least 500 lbf) and stay in the elastic range.
- No friction: in deviated wells the real free length is longer than calculated. CT on the reel and above the injector is not part of the length.
- E is 26 to 30×10⁶ psi for CT steels (CTES); manufacturer tables may use a slightly smaller area (minimum wall), so use their FPC when available.
Worked example
1.75 × 0.134 in (As = 0.6803 in²), ΔF = 5,000 lbf, ΔL = 24 in, E = 30×10⁶ psi → L = 30×10⁶ × 0.6803 × 24 / (12 × 5,000) = 8,164 ft, FPC = 1,701.
Sources: Baker Hughes — Tech Facts, Tubing, Drill Pipe and Casing Stretch Data (general stretch formula, E = 30×10⁶ psi) · Tenaris Coiled Tubes — Free Point Calculation & CT Stretch Table (2007) · CTES — Coiled Tubing Manual, Ch. 3 (E = 26–30×10⁶ psi for CT steels)
Educational quick-check tool, not an approved procedure. Follow your company procedures and the manufacturer’s data.
Buoyed weight in fluid
Weight in air and in fluid, with different fluids inside and outside the CT.
How it is calculated
w_b = w_air + 0.05195 · (ρi · Ai − ρo · Ao) [ρ in ppg, A in in²]
Same fluid in and out: BF = 1 − ρ / 65.5
0.05195 = 12 / 231 (in³ per ft per gal)
Assumptions
- Vertical well, no friction, same fluid over the whole length. Excludes wellhead pressure acting on the CT area at the stripper and stripper friction, which both change the weight indicator reading.
- Steel density 0.2836 lb/in³ (65.5 ppg).
Worked example
1.75 × 0.134 in, 10,000 ft, 8.6 ppg outside, 8.34 ppg inside → w_air = 2.315 lb/ft, w_b = 2.315 + 0.05195 × (8.34 × 1.7250 − 8.6 × 2.4053) = 1.988 lb/ft, total 23,152 lbf in air and 19,880 lbf buoyed.
Sources: Bourgoyne, A.T. et al. — Applied Drilling Engineering, SPE Textbook Vol. 2 (buoyancy) · API Spec 5L / 5CT plain-end weight formula · CTES — Coiled Tubing Manual (weight in fluid)
Educational quick-check tool, not an approved procedure. Follow your company procedures and the manufacturer’s data.
Annular velocity during cleanout
Upward fluid velocity in the CT-to-tubing annulus, compared with the particle settling velocity if known.
How it is calculated
AV (ft/min) = Q (bbl/min) / annular capacity
AV / v_s ≥ 2 (common rule of thumb, vertical wells)
Assumptions
- Incompressible fluid, average velocity over the section. No nitrogen or gas expansion.
- The “at least twice the settling velocity” rule is a common rule of thumb for vertical wells, not a standard; deviated and horizontal wells need higher velocities and proper models.
Worked example
2.0 bbl/min in 2.992 in tubing with a 1.75 in CT → annular capacity = 0.005721 bbl/ft, velocity = 2.0/0.005721 = 349.6 ft/min (106.5 m/min), that is 5.83 × a 60 ft/min settling velocity.
Sources: Halliburton Cementing Tables (annular capacities) · Bourgoyne, A.T. et al. — Applied Drilling Engineering (annular velocity, particle slip)
Educational quick-check tool, not an approved procedure. Follow your company procedures and the manufacturer’s data.