It is used to control and eliminate lost circulation due to fracures, broken formations. Lost-circulation materials can be broadly defined to include any material that seals or bridges against permeable or fractured formations to inhibit the loss of whole drilling fluid. An enormous variety of materials have been used to bridge, mat, and/or plug voids to combat loss of circulation. These materials can be divided into four categories: fibrous materials, flake materials, granular materials, and blends containing fibrous, flake, and granular materials.