TX 75083-3836 U.S.A., fax 1.972.952.9435. AbstractTo qualify for use on a world record extended reach drilling (ERD) well, a trial well was selected to demonstrate the technical benefits of using a uniquely designed, low-rheology, synthetic-based drilling fluid. The 8½-in., production hole section was 1,755 ft (535 m) long and drilled to 20,472 ft (6,240 m) at an angle of 25°. Prior to drilling this section, a low-rheology drilling fluid was selected. Selection analysis was based on assessment of key drilling parameters as compared with wells drilled previously using a conventional API barite-weighted synthetic fluid. A unique characteristic of the low-rheology drilling fluid is its use of specially treated, micron-sized, barite-weight material (TMSB). It can be formulated with a much-reduced rheological profile without the risk of barite sag. This paper presents the background work performed leading up to the field trial. Field data is presented comparing the drilling performance and fluid characteristics between the low-rheology fluid and the previously used conventional API barite-weighted synthetic fluid system. Significant reductions in equivalent circulating density and standpipe pressures were accomplished, as well as torque reductions of up to 30%. Results demonstrated the low-rheology, synthetic-based drilling fluid's ability to reduce drilling risk. This paper reports the economic and technical benefits realized from using this fluid, including the first use of 400-mesh prototype shaker screens (API 200 mesh), the much reduced dilution factors, and cuttings re-injection volumes.