Abstract
A subsurface study of the Agbada Formation in the Akpor and Apara oilfields in the eastern Niger Delta was undertaken in order to determine the depositional development of the reservoir sand‐bodies.In the study area, the formation comprises a maximum of 29 relatively thick sandstones, cyclically interbedded with shales of varying thicknesses. The lowest tow sand units, separated by a shale unit and located near the base, produce petroleium from ten wells in both fields. Each sand‐body exhibits a coarsening‐upward textural gradient.The lower sand‐body (Unit A), which is oval‐shpaed, moderately‐ to poorly‐sorted, fine‐ to very coarse‐grained, carbonaceous, with clay and lignite horizons, is interpreted as a deltaic sand. The unit appears to have migrated landwards (north) (destructive delta), probably as a result of localized transgression, and developed maximum thickness between the two fields.The upper sand (Unit B) is fine‐to‐pebbly in grain size, well‐sorted and glauconitic. Maximum development occurred slightly east of the delat. As the unit prograded in a predominantly southerly direction, genetic currents simultenously caused it to be channelized. This sand‐body is interpreted as an offshore marine bar. The intervening carbonacous shale is thought to be of logoonal origin.Since the geometries of these sand‐bodies are not conclusively delimited by the existing well density, their pinch‐out edges to the north, east and west may constitute prolific stratigraphic traps.
Published Version
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