**1. Introduction**

The drilling fluid is a general term for liquid-based, gas-based and combinations thereof that serves as the focus in a circulating system of a rotary drilling rig. Usually, it is designed to perform certain functions, possess the required properties to furnish the desired functions and satisfy recommended specifications when tests are conducted [1, 2]. Its design involves basic knowledge of chemistry, physics, mathematics and sound knowledge of petroleum engineering principles and oilfield practices.
