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The classification of drilling fluid

2012-09-26

Drilling fluids are generally categorized as “water-base” or“oilbase”, and as “weighted” or “unweighted” muds. Water-base Muds contain water as the liquid phase and are used to drill most of the wells in the world because they are relatively simple, expense is usually reasonable, and water is commonly available in most places.

Oil-base Mud contains either natural oil or synthetic oil as the continuous liquid phase and is used for maximum holes protection. Oil base mud and synthetic oil mud are usually much more expensive than water-base mud and therefore are only used when there is a specific need, such as to keep the hole from swelling or caving in, or to reduce friction and prevent stuck pipe in very crooked or high angle holes. Either water-base or oil-base mud can be used as “weighted” mud.

Weighted Mud refers to any mud which has barite or barite substitutes added to increase density. These mud normally have a density greater than 10.0 lbs/gal. The solids in weighted mud consist of drilled solids from the hole, plus barite, plus commercial clays added to control fluid loss and viscosity.

Unweighted Mud refers to any mud which has not had barite added. This mud type normally has a density of less than 10.0 lbs/gal. The solids in unweighted mud consist of drilled solids from the holes, plus commercial clays.