The Petroleum Systems of Deep Water Namibia

Roger Swart
NAMCOR (Pty) Ltd, Windhoek, Namibia

The Cretaceous-Tertiary basins offshore Namibia are underexplored with only 14 wells (7 of which are in the Kudu Gas Field area) being drilled in an area that covers over 350,000 sq km. Although no commercial discoveries have been made outside of the Kudu Gas Field as yet, the wells have proven that the various elements of a petroleum system are all present. Excellent source and reservoir sequences have been found of various ages and have been described comprehensively before. New seabed geochemical sampling, heat flow data and high quality regional 2D seismic data has given further evidence for the presence of petroleum systems. This presentation will focus on the new data and the implications for future deep water exploration in south western Africa.

In 2003, 3300 km of long offset seismic data was acquired west and south of the Kudu field in the Orange Basin and 1016 km in the Walvis Basin. This data, acquired with 8,000 m offsets and processed with fully ray traced Kirchoff pre-stack time migration (UTMOST), has dramatically improved structural imaging within the complex shelf-edge slump zone which has, in turn, led to significantly improved imaging of the Kudu reservoir section and the deeper pre-rift sediments. The long offset data also allows improved multiple attenuation together with higher fold of stack thus reducing noise in the data. It also allows more accurate AVO analysis for deeper reservoir potential including the Kudu reservoir section.

In the surface geochemical sampling programme, evidence for thermogenic hydrocarbons was found in the Namibe, Walvis and Luederitz Basins. The stable isotopes indicate that the hydrocarbons have, at least in part, been derived from a marine, oil prone source rock.