Well cementing operations are crucial during the drilling and completion of oil wells. The cement sheath must have sealing ability throughout the well's life and provide long-term zonal isolation in hostile downhole conditions to avoid potential remedial costs and environmental impacts. In the development of API cements, the reinforcement with dispersed fibers plays an important role. Screening tests were performed to evaluate fiber types (carbon, polypropylene, mineral) with the aim of comparing cement composites that provide improvements in mechanical behavior. All the slurries showed pumpability values at room temperature below 70Bc (Beardon units of consistency) and are regarded to be pumpable. All the fiber reinforced cement composites presented a notable increase in impact resistance (up to 120%) and flexural strength (up to 80%) compared to the values for unreinforced matrix. Carbon and mineral fibers also show a noteworthy capacity to increase or maintain the tensile and compressive strengths (data were usually in the ranges 1-2 and 30-45MPa, respectively) of API cement systems; however, compressive and tensile strength data decrease significantly with the addition of polypropylene fiber type (up to 65 and 25%, respectively). The study mineral fiber with nano-silica could be useful to carry out well cementing jobs.