Drilling is one of the most common methods for the production of hydrocarbon or geothermal sources. Success of drilling operations depend on the mechanical and thermal properties of drilling mud. Since ensure direct connect between formation and surface, it is main factor which should be control in drilling. It provides some basic properties during the drilling process such as controlling the formation pressure, carrying the cuttings from bit to surface, suspending solids in the mud when circulation is stopped, forming low-permeability filter cake, maintaining the stability of the borehole, reducing friction between the drilling string and the sides of the hole, cooling and lubricating the bit, assisting in the collection and interpretation of information available from cuttings etc. One of the most significant tasks of the drilling mud is controlling the formation pressure. This pressure, also named as hydrostatic pressure, depends on the depth and mud weight. Also, the mud weight depends mainly High Gravity Solids (HGS), such as barite or calcium carbonate, in the drilling mud. Hence, it is necessary to add these materials when the weight of the mud is desired to be increased.