US Patent 9410066 Drilling lost circulation material

An engineered composition for reducing lost circulation in a well includes a mixture of coarse, medium and optional fine particles, and a blend of long fibers and short fibers. The long fibers are rigid and the short fibers are flexible. The long fibers form a tridimensional mat or net in the lost-circulation pathway that traps the mixture of particles and short flexible fibers to form a mud cake. The mixture of particles and blend of fibers may be added to water based and oil-based drilling fluids. The composition, size, and concentration of each component of the mixture of particles and blend of fibers may be fine-tuned for each application.