Drilling calculation guides
These guides cover the sums that drillers, assistant drillers, toolpushers, mud engineers, mud loggers and well site supervisors use every day: pressures, volumes, pump strokes, kill sheets, trip sheets, mud weights, cement, string loads and surveys. Each one explains a formula, where its constants come from, where it is used on the rig, and the mistakes that most often lead to wrong answers. Every guide has at least one worked example with realistic numbers, and most include a metric version alongside US oilfield units.
They are written for three kinds of reader. Students and new hands preparing for IWCF or IADC WellSharp courses can use them to understand why a formula works rather than just remembering it. Crews on the rig can use them to check a number quickly before it goes on a sheet. Engineers and supervisors can use them as a plain-language reference when explaining a calculation to someone else.
If you are new to the subject, start with hydrostatic pressure and hole volumes: almost everything else is built on those two. From there, the well control guides (kick signs, kill sheets, leak-off tests and trip sheets) follow naturally, and the mud, cement and drill string guides can be read in any order. Each guide links to the ones that use its results.
To get the most out of the examples, work them yourself with a calculator before reading the answer, then repeat them with the figures from your own well. If your result differs, check the units first, then whether a depth is measured or true vertical, then whether a diameter is inside or outside.
The guides are for training and for checking your own work. They are not a substitute for your company's procedures, your well programme or the judgement of the people responsible for the well.
Pressure and well control
Hydrostatic pressure, mud gradient and equivalent mud weight
Pressure from a column of mud, gradients and EMW: the base of every well control sum.
Kick warning signs, flow checks and shut-in data
The early signs that the well is flowing, how to flow check, and what to record after shutting in.
How to fill in a kill sheet (wait and weight method)
Kill mud weight, ICP, FCP, strokes and the drill pipe pressure step-down, step by step.
Leak-off test, formation strength and MAASP
Turning a leak-off test into EMW, running an FIT, and keeping MAASP up to date.
Trip sheets: hole fill, pipe displacement and swab checks
Calculated hole fill for dry and wet trips, slugs, trip margin and how to spot swabbing early.
Volumes, pumps and hydraulics
Hole volume, pipe capacity and annular capacity
Capacity of hole, pipe and annulus in bbl/ft and L/m, and the full circulating volume.
Mud pump output, strokes to bit and bottoms-up time
Triplex and duplex output per stroke, efficiency, strokes to bit and bottoms-up.
Annular velocity and equivalent circulating density (ECD)
How fast mud moves up the annulus, and how circulating raises the bottomhole pressure.
Bit hydraulics: TFA, nozzle velocity, HSI and impact force
Nozzle area, jet velocity, bit pressure drop and the hydraulic power that cleans the bit.
Mud tank volume: rectangular and cylindrical pits
Barrels and barrels per inch for rectangular, vertical and horizontal tanks, plus metric.
Drilling unit conversions: ppg, sg, psi, bar, bbl and m³
Density, pressure, gradient, volume, flow, load and torque conversions with worked examples.
Mud and cement
Drilling fluid properties: mud weight, PV, YP and gels
What the mud report numbers mean and how they affect hole cleaning, ECD and well control.
Weighting up mud with barite
How much barite raises the mud weight, how much the volume grows, and diluting back down.
Cement volume: slurry, sacks, mix water and displacement
Slurry volume with excess, sacks from yield, mix water and the strokes to bump the plug.
Drill string, casing and directional
BHA basics: collars, HWDP, stabilizers and weight on bit
How many collars a bit weight needs, where the neutral point sits, and what each component does.
Buoyancy factor, hookload and weight on bit
How mud weight reduces string weight, and how to read hookload and weight on bit correctly.
Torque and drag basics: friction factors and hookloads
Pick-up, slack-off and rotating weights, friction factors and what a broomstick plot tells you.
Stuck pipe: causes, first actions and free point from stretch
Differential and mechanical sticking, the first actions to take, and estimating the free point.
Directional survey calculations: minimum curvature step by step
Turning inclination and azimuth readings into TVD, north, east and dogleg severity.
Casing design basics: burst, collapse and tension
The three main loads on a casing string and how design factors are applied to them.
Do it on your phone
DrillPro runs every one of these calculations on its own screens, keeps your sheets, and exports them to PDF and Excel. It works on Android, the web and desktop.