I n each drilling process, drilling fluid is important and critical. Successor failure in drilling operations can not be separated from the use and quality ofsludge made. The drilling mud itself is divided into three types of mud, namelywater-based mud, oil-based mud and synthetic oil-based sludge. Each type ofdrilling mud has its own advantages and disadvantages. The choice of drillingmud type is based on the formation layer to be penetrated. The use of water-basedsludge in the reactive shale layer can cause drilling problems, namely swelling.Swelling is one of the drilling problems that occurs due to the meeting of waterwith clay minerals. When water meets the shale layer, water will enter into andcontaminate clay minerals. The mineral clay will expand and can cause a series ofdrill pipes to be pinched. Mineral clay can expand up to 20 times its initialvolume. The use of proper drilling mud can avoid the cause of swelling. Waterbaseddrilling mud can be used in the shale layer using additional substances suchas shale inhibitors. The addition of shale inhibitor substances aims to prevent clayminerals from developing when they meet with water. KCL polymer is a shaleinhibitor. Therefore, the selection of the title of this final assignment with the titlePlanning of the drilling mud program on the X Y-hole well needs to be done.Because it can overcome the problem of drilling in the form of swelling thatoccurs in the Y field X wells.