ECD & bottom-hole circulating pressure
Annular pressure loss, flow regime and the equivalent circulating density the formation actually sees while the pumps are running.
Drilling
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.
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How it is calculated
- Annular capacity per section is π(Dh² − Dp²)/4, string capacity is πDi²/4, both computed in SI and reported in bbl and bbl/ft.
- Effective pump output is displacement × volumetric efficiency. Strokes to bottoms-up is annular volume divided by that.
- Annular velocity per section is flow rate divided by that section's annular area — the number that decides whether the hole cleans.
Standards it speaks
Where this stops being true
It is a geometric volume of an in-gauge hole. Real open hole is washed out, and a caliper commonly shows 5–15 % more volume than the bit size implies — which is exactly the error that lands a cement job short. Where a caliper exists, enter the caliper average as the hole diameter rather than the bit size.
Related tools
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.
Kill sheet — driller's method
Kill mud weight, initial and final circulating pressure and the step-down schedule, for rehearsal and for checking a sheet that has already been worked.
Training aid