Drilling Well Design Concepts Quiz

The ECD is calculated as: $r = \frac{P},{0.052D}$, where r is the mud density in ppg, P is the sum of the hydrostatic pressure and the frictional pressure drop in the annulus between the depth D and surface in psig, and D is the true vertical depth in feet.

The example calculates the static mud density required to prevent flow from a permeable stratum at 12,200ft if the pore pressure of the formation fluid is 8500psig. The solution is: $r = \frac{8500},{0.052 \times 12,200} = 13.4lbm/gal$. The mud density must be at least 13.4 lbm/gal.

ECD refers to the effective density exerted by a circulating fluid against the formation that takes into account the pressure drop in the annulus above the point being considered.

Hydrostatic Pressure in Liquid Column is the pressure exerted by a column of liquid at equilibrium due to the force of gravity.

The frictional pressure drop in the annulus is significant for calculating ECD as it affects the effective density exerted by the circulating fluid against the formation, and thus must be considered in the ECD calculation.