The main purpose of using CMC Carboxymethylcellulose in drilling is ♦ Minimize water loss and control the fluid system. ♦ Provides shale inhibition by preventing well bore against collapse due to their film forming properties. ♦ Improves the cooling and lubricating properties of the drilling fluid. ♦ Helps protect the thermal and biological stability of the fluid CMC Carboxymethyl cellulose and PAC Polyanionic Cellulose are used to control and manage the rheological properties of the fluid. During the drilling process it is important to control water loss because It effects all lubrication and pumping the drilling mud. CMC is also used as a thickening agent, for example, in the oil-drilling industry as an ingredient of drilling mud, where it acts as a viscosity modifier and water retention agent. Two kinds of CMC called HV (high viscose) and LV (low viscose) provides to pump drilling mud easily.