T he drilling mud as a drilling fluid is one important part in determining the success of the drilling operation. Drilling mud in order to function properly and optimally, the physical properties of the drilling mud must be controlled. Physical properties of the drilling mud include mud density, viscosity, and so that power (gel strength). Of controlling the physical properties of the sludge will get optimum penetration that allows the drilling time will be shorter. The selection of the type of mud in drilling operations must comply with the conditions of formation and characteristics that will be penetrated in order to the function properly drilling mud. The system serves as the addition of potassium lignite deflokulan good for the type of water based mud and as a provider of K ions, where high concentrations of potassium can be used to inhibit the development of shale. Potassium lignite can also be used to improve the rheological properties of the mud and helps maintain a constant pH. It is especially effective to stabilize the high-temperature sludge affected. At this final project aims to investigated and search for the exact composition of the mud to the mud system potassium based lignite. Then performed an analysis of the effect of high temperature on the composition of the sludge, in order to know the composition of the sludge which is most appropriate and which can be used in the mud system