Buoyancy

The effect on the weight of an object run in a fluid

Buoyance is the force applied upwards on an object partially submerged in fluid, this force is generated by the weight of the fluid displaced by the object.

For drilling this means that the string weight when in hole will be less than the calculated weight in air. In order to calculate the reduced weight, the units for the density of steel needs to match the units for the density of the fluid.

e.g. mud in ppg, steel density = 65.5ppg

mud in lb/ft3, steel density = 489 lb/ft3

BF = (Steel Density-mud density)/mud density Or use the handy calculator linked below