Ven-Fyber Medium™ is a premium blend of micronized, surface-modified organic fibers for the prevention and remediation of seepage loss to moderate whole fluid losses in drilling fluid applications. Ven-Fyber Medium™ is field proven around the world for the prevention and mitigation of seepage & moderate to severe whole fluid losses. Ven-Fyber Medium™ is composed of a blend of differing types of surface-modified micronized cellulosic fibers. The differing types and sizes of the source materials provide excellent bridging and matting of thief zones in the near well-bore formation for effective sealing and prevention of whole fluid losses.