Annular Hydraulics and Velocity Guide
A drilling annular hydraulics guide connecting flow rate, annular geometry, average velocity, hole-cleaning limits, pump output, pressure loss, and equivalent circulating density.
linked formula references
verified source links
Practical workflow
- 1
Divide the well into intervals with distinct hole, casing, drillpipe, or collar geometry.
- 2
Convert pump output to circulating flow rate and calculate average annular velocity for each interval.
- 3
Review inclination, rheology, cuttings properties, pipe eccentricity, and operational evidence before judging transport.
- 4
Calculate pressure loss and ECD at the same rate and confirm the full operating window remains acceptable.
Geometry and flow-rate basis
Calculate annular velocity for each material hole or casing interval because outer diameter and pipe outside diameter determine annular area. The smallest clearance does not automatically have the worst cleaning behavior, but it will have the highest average velocity at a fixed flow rate.
Use actual circulating flow when available. Pump displacement times strokes per minute is a theoretical rate and should be adjusted for the operating efficiency or losses appropriate to the field workflow.
Velocity is one part of hole cleaning
SLB identifies annular velocity, hole angle, and flow profile as principal controls on carrying capacity, with mud weight, cuttings size, pipe position, and pipe movement also affecting transport. An average-velocity calculator therefore supports, but cannot close, a hole-cleaning assessment.
Check the proposed rate against standpipe pressure, surface equipment limits, downhole motor or tool limits, annular pressure loss, ECD, formation integrity, and lost-circulation margin before increasing circulation.
Start with these calculators
These links keep the guide close to the working calculator flow.