SPE Members Abstract The first wells have been successfully completed offshore Gulf of Mexico using a new synthetic-based drilling fluid. Polyalphaolefin (PAO), the synthetic base used for these fluids, is unique to the drilling fluids industry at this time. The environmental benefits of PAO-based synthetic systems over conventional oil-based fluids and some water-based fluids has already been presented in prior papers. However, the practical benefits gained from utilizing PAO as an alternative to conventional systems can now be documented after a series of highly successful field tests in the Gulf of Mexico. The non-aqueous PAO system has been used on several wells in the Gulf of Mexico to drill problematic formations previously drilled with either inhibitive waterbased or oil-based fluids. Wells with angles up to 86 and formations from 4500 ft to 18300 ft have been successfully drilled. Direct comparisons can be made regarding performance benefits of PAO-based synthetic systems verses waterbased and oil-based systems previously used to drill in the same location. Benefits in hole stability, cuttings integrity, lubrication, and gauge wellbores, all leading to increased penetration rates and subsequent reduction in drilling days, can be seen. This paper reviews the results of the first field tests with PAO synthetic systems in the Gulf of Mexico concentrating on the practical aspects of drilling rather than the detailed environmental information which has been covered in prior literature. Introduction Drilling in certain areas of the Gulf Coast demands a great deal from a mud system. Massive sections of extremely reactive, hydratable shales commonly known as "gumbo" must be drilled at shallow depths. These often create the need for high dilution rates with waterbased muds and still create wellbore instability problems even with the most inhibitive systems. The need for weighted systems and the requirement for directional wells from platforms has lead to the use of both diesel-based and low toxicity invert oil mud systems. Although conventional oil muds have provided the best available technology in the past, the environmental constraints placed on these systems add many directly related operational problems and costs. P. 405^