TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractAlbacora Leste, one of the largest Campos Basin deep-water oilfields, was discovered in March of 1986. Oil field development area involves 141km 2 and water depth ranges from 800 to 2000m. In order to exploit the field, 30 horizontal wells -16 producers and 14 injectors -will be connected to an FPSO unit (P-50). Expected total reserves are 565 million barrels of oil.Albacora Leste main reservoirs are Miocene sandstones with high porosity and permeability. The depositional model is interpreted as a complex turbidity system, mainly represented by channels, lobes and overbank facies. Net thickness ranges from 5 to 35m, suggesting horizontal well drilling. After the deposition stage, erosive channels introduced flow barriers that generated different reservoir compartments. These compartments impacted drainage pattern design and were checked through reservoir pressure data after long term pilot well production, log interpretation, and fluid samples analyses. Small gas caps showing different gas/oil contacts were detected all over the field area, introducing an additional challenge for field development.Intensive application of the following technologies was important to make field development technically and economically successful: (1) high quality 3D seismic; (2) image logs and LWD (logging while drilling); (3) long gravelpacked horizontal wells; (4) thermally insulated flowlines, allowing flow assurance for distant satellite wells; and (5) massive sea water injection for sweep, and reservoir pressure maintenance. In order to avoid scale deposition as a result of sea water injection, a Sulphate Removal Unit was installed in the P-50 FPSO.This paper presents the key aspects of the reservoirs, the drainage modeling and design, as well as the strategy adopted during project implementation, in order to overcome main reservoir uncertainties, such as fluid type, connectivity, and net pay, accomplishing at the end a successful project execution.