In 1996, Chevron Nigeria Ltd. acquired a repeat 3D-seismic survey over the Meren field, offshore Nigeria, for time-lapse seismic reservoir-monitoring purposes. By comparing the 1996 survey with a Chew-ron legacy 3D survey dating fi om 1987, the time-lapse 4D-seismic images show evidence of significant reservoir-fluid changes during the 9-year interval. A detailed 4D-seismic interpretation of the Meren E-OS reservoir sand in Block 2 suggests that water from two injectors has very preferential channel-flow characteristics not previously discernible from well data alone. Also, the 4D-seismic interpretation has identified three areas that may contain major amounts of bypassed oil reserves, and has better defined the leaking or sealing nature of reservoir faults.