Premium Blend II™ is a premium fine/medium blend of micronized, surface-modified organic fibers for the prevention and remediation of seepage loss to moderate whole fluid losses in drilling fluid applications. Premium Blend II™ is composed of a blend of differing types of surface modified micronized cellulosic fibers and cellophane flakes. 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.