Water as a drilling fluid does not qualify as a mud. If there are no hole (formation) problems that prevent its being the most economical drilling fluid; if neither the geologist, palentologist, nor production supervisor have valid objections; and if it is available, water is seldom if ever surpassed. When the formation requires, or a supervisor demands , filtrate control and / or viscosity and /or gels in the drilling fluid, a “mud” is built. Or if the fluid density required is too high for salt water alone , mud properties are required to suspend barites.
Functions of drilling fluid
EFFECT OF ADDING BENTONITE ON MUD PROPERTIES FOR FRESH AND SALT WATER BASE MUD:
Many of the components in drilling fluids can affect the efficiency of solids-control devices. As discussed in the previous section, fluid rheology, shale inhibition potential, wetting characteristics, lubricity, and corrosivity can all affect both the properties of cuttings and the performance of solids-control equipment. Key components that affect those properties include colloidal materials, macropolymers, conventional polymers, and surface-active materials.