Mud weight is normally adjusted by adding:

• A. Calcium carbonate
• B. Barite or bentonite
• C. Water
• D. Sodium chloride

Answer: (B)

Mud weight is adjusted by adding solids with higher density to the drilling fluid so the column of mud can exert enough hydrostatic pressure to balance formation pressure. The most common weighting agent is barite, a very dense, inert mineral that raises density without reacting with the mud or formations. Bentonite, while primarily used to improve rheology and filtration control, is sometimes included in mud formulations and can contribute to density in certain systems. That combination of barite or bentonite-based products used to achieve the target density is why this option is the best fit.

Calcium carbonate is a lighter filler and doesn’t provide the needed high density. Water lowers density, and sodium chloride only raises density modestly and isn’t used for substantial mud-weight adjustments.