MICRONIZED CELLULOSE FIBRE lost circulation material is a natural cellulose fiber that can be used in pills, sweeps and maintenance treatments with minimal adverse effect on rheology and filtration control properties. The cellulosic material helps decrease the permeability of the wallcake in all drilling fluid types. MICRONIZED CELLULOSE FIBRE lost circulation material additions do not interfere with pumping equipment or downhole tools when used in the proper concentration ranges. These materials are compatible with water and non-aqueous based fluids.