1.
n. [Drilling Fluids]
The mass per unit volume of a
drilling fluid, synonymous with mud density. Weight is reported in lbm/gal (also known as
ppg), kg/m
3 or g/cm
3 (also called
specific gravity or SG), lb/ft
3 or in hydrostatic gradient, lb/in
2/ft (psi/ft) or pptf (psi/1000 ft). Mud weight controls
hydrostatic pressure in a wellbore and prevents unwanted flow into the well. The weight of the mud also prevents collapse of
casing and the
openhole. Excessive mud weight can cause
lost circulation by propagating, and then filling, fractures in the
rock. Mud weight (density) test procedures using a mud balance have been standardized and published by the
API.