Introduction One of the earlier waterfloods in Trinidad was in the El Blanco area of the Nanette Field. The El Blanco area was discovered in March 1966 and rapid field development followed, Primary. production was by solution gas drive, and reached its peak during 1968. A reservoir engineering study was made with tee objective of increasing recovery, and a peripheral waterflood commenced in August 1969. Production response to the flood has been generally favourable.. GEOLOGY The Navette Field is located in the Guayaguayare area of South East Trinidad, forming part of the south eastern flank of the Lizard Springs anticline (see Figure 1). Numerous cross faults occur in the field The El Blanco area, containing the largest fault block, covers the eastern one third of the area. (See Figure 2). Production is from Lower Gros Morne sands of Miocene age. The Lower Gros Morne Zone 4 is one of several Lower Gros Morne sands production in the area, and has been divided into an upper and lower zone, The lower zone consists of a massive fine-grained oil sand underlain by water, while the upper zone is characterized by alternating thin sands and shales. (See type log Figure 3). The sands were derived from a mixed source including volcanic rocks and deposited in the shallow marine, portion of a deltaic complex. The formation consists of vary fine grained sand medium grey, siltstone and shale.