Petroleum Exploration on Niger Delta: ABSTRACT

Abstract

The Nigerian continental shelf, covering over 40,000 km2 to a water depth of 200 m has been extensively explored since 1962. Most of the shelf is a submarine extension of the Niger delta where the first discovery was made in 1956. The section is a typical delta, where the prodelta shales of the Akata Formation prograde over Paleocene and Upper Cretaceous sediments and are overlain by interbedded sands and shale of the Agbada Formation of the deltaic facies proper. The deltaic facies are overlain by the massive freshwater alluvial-plain sands of the Benin Formation. These are lithostratigraphic units that, depending on the position on the delta, range in age from Eocene to Holocene. The delta is deposited over the boundary between continental and oceanic crusts nd, in large part, overlies the oceanic crust of the Gulf of Guinea. The Akata Formation is thought to be, in part, the source of hydrocarbons. The reservoirs are found in the Agbada Formation and the Agbada shales act as seals. The dominant trapping is by down-to-the-basin growth faulting and the accumulation seems to be the result of migration updip along the major faults. As of January 1978, the Niger delta initial recoverable oil was estimated at 18.76 billion bbl. The major production occurs in a belt that runs approximately east-northeast to west-southwest, with the result that prolific production offshore has mostly been found in two places (east and west of the delta) End_Page 615------------------------------ where the belt crosses the shelf. These offshore prolific areas represent only 25% of the total shelf area. The reported offshore ultimate recoverable oil is 4.8 billion bbl or 25.4% of the Nigerian total. In general, the proportion of natural gas to oil in Nigeria is relatively high and increases basinward. Reserves in the order of 40 to 50 tcf have been reported. However, due to the lack of marketing opportunities, this gas has been found incidentally to oil exploration. It is, therefore, possible that in the least prolific offshore areas, considerable reserves of gas could be established if the proper economic incentives existed. End_of_Article - Last_Page 616------------