Electric log interpretation for the evaluation of salt water intrusion in the eastern Niger Delta

The Niger Delta (75 000 km 2 ) comprises a thick (up to 9000 m) sequence of clastic sediments subdivided into the Akata, Agbada and Benin Formations in ascending order. Sands of the Benin Formation constitute aquifers which have been exploited for water supply, although in parts of the delta many of them have been abandoned due to high salinity. Interpretation of 267 oilwell logs for delineating the fresh water-bearing aquifers is reported here. While fresh water sands occur at the upper zone of the Benin Formation in most places, saline water sands were found at the upper zone at depths (ranging from 30 to 947 m) in two well-defined areas, underlain by fresh water sands. The saline water is thought to be connate. The fresh water/saline water interface has been mapped throughout the eastern Niger Delta and is found to be deepest (2237 m) 44 km westsouthwest of Port Harcourt.