Lost circulation can occur during drilling or primary cementing procedures, resulting in ineffective mud removal and poor zonal isolation, increasing the need for expensive and time-consuming remedial cementing jobs. The Schlumberger Losseal family of reinforced composite mat pills enables the mitigation of risks associated lost-circulation issues encountered during cementing and drilling operations. The Losseal system combines fibers and solids into a specifically engineered, flexible fiber additive pill, which uses synergy between the physical characteristics of the fibers and solids, effectively plugging fractures that cause partial or total losses while drilling or cementing. An impermeable grid is also created, which is strong enough to withstand additional pressure from mud density increases, as well as any additional pressure from future drilling or cementing operations.