I In a drilling operation, drilling mud is something very important. Due to various factors affecting the drilling mud as penetration rate (rate of penetration), the efficiency of drilling time, drilling operation costs, to safety during the process of drilling underway. Use the right kind of drilling mud is expected to help achieve optimum results from a drilling operation. Along with the deepening of the depth of a well, the higher the temperature due to the geothermal gradient. This is clearly an obstacle during the drilling process because it can change the physical and rheological properties of the drilling mud. Plus, if the penetrated layer is an active shale formation wells which can cause hydration of clay, so the swelling clay may occur which can cause entrapment series of drill pipe (pipe stuck). Clay hydration is affected by the salinity levels of the formation water and also the salinity levels of the drilling mud itself. Therefore, drilling mud that can overcoming these problems is necessary, one of which is by using oil based mud (OBM). Oil based mud has advantages in overcoming the above problems as compared to water-based mud. Oil based mud discussed in this case is using the basic ingredients of the SF-05 (Smooth Fluid-05) domistically produced, and seen its ability to salinity levels that vary.