Potential field analysis of the East African Rift in eastern Tanzania – guiding seismic survey planning

Summary

Recent oil discoveries in the Kenyan Lokichar Basin, along the eastern branch of the East African Rift system, have enhanced the oil and gas potential within the Tanzanian and Kenyan portions of the rift system. A combination of airborne gravity and magnetic surveying was completed over sections of the eastern branch of the East African Rift in eastern Tanzania to investigate the potential for thicker accumulations of Tertiary and Karoo sediments. The objective was to identify prospective basin areas warranting evaluation by seismic surveying. Interpretation and modelling of the regional aeromagnetic data identified major basement fault systems controlling basin formation and provided a qualitative assessment of depth to basement. Density contrasts typically expected for Precambrian basement and Karoo and Tertiary sedimentary sequences were used for forward modelling of the airborne gravity data. This showed the potential for up to 7 km thickness of basin sediments within the rift, and highlighted the possibility of Tertiary sediment within one of the identified sub-basins. Subsequent 2D seismic acquisition has refined the basin geometry, and identified an intra-basin structure of exploration interest.

• East African Rift
• magnetics
• gravity