3.1 Mud Weight or Density
Density is defined as the mass per unit volume as shown below
\(Density,\ \rho=\frac{Mass,\ m}{Volume,\ V}\) (7)
Controlling the density of the drilling fluid system is important to provide adequate hydrostatic head. The hydrostatic head of drilling fluids prevents influx of formation fluids hence it is necessary to know the density of the fluid. The value must not be too high as to cause loss of circulation, which could result in destruction of the formation. The normal value for pressure gradient by water is about 0.433 psi/ft. (433 psi/1000ft). The calibrated values of the mud balance which is the apparatus used to measure the mud weight or density is as shown below.
P = 0.052 x ρ x h
Where, P = pressure (psi), ρ = mud weight or density (ppg) and h = formation depth (ft.)