Well volumes & circulation time
Annular and string volumes section by section, then the strokes and the minutes to bottoms-up and to a full circulation.
Drilling
Torque & drag — soft string
Pick-up, slack-off and rotating hookload and surface torque from a survey, a string tally and a friction factor.
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How it is calculated
- Johancsik soft-string: normal force Fn = √[(Ft·Δα·sinĪ)² + (Ft·Δθ + W·sinĪ)²] on each 30 ft element.
- Axial force integrates from the bit upwards: ΔFt = W·cosĪ ± μ·Fn, with the sign set by direction of travel.
- Torque accumulates as μ·Fn·r with r the pipe radius. Rotating off bottom carries no axial friction, which is why it sits between pick-up and slack-off.
- Buoyancy factor = 1 − MW/65.5, applied to every element weight.
Standards it speaks
Where this stops being true
Soft string means the pipe is treated as a cable: it carries no bending stiffness and touches the wall everywhere. That is a good approximation for drill pipe in a smooth hole and a poor one for stiff BHA components through a dogleg, for anything in compression, and for a well with a tortuous, wiggly survey. Once slack-off goes into compression the model is outside its range and the answer it gives is optimistic. A single friction factor per hole section is also a fiction that absorbs cuttings beds, key seats and differential sticking into one number.
The capability that automates this
- DR-05Stuck Pipe PredictionWarns that the string is becoming hard to move, typically twenty to sixty minutes before it stops moving at all.
- DR-06Real-Time Torque, Drag & HydraulicsCompares what the string should weigh and how hard the pumps should work against what is actually measured, and flags the gap.
Related tools
ECD & bottom-hole circulating pressure
Annular pressure loss, flow regime and the equivalent circulating density the formation actually sees while the pumps are running.
Bit hydraulics & nozzle selection
Total flow area, nozzle pressure drop, HSI and jet impact force — plus the nozzle size that would put the optimum share of pump pressure at the bit.
Directional survey — minimum curvature
Paste MD, inclination and azimuth and get TVD, northings, eastings, dogleg severity, vertical section and closure — with the well path drawn.