Reservoir Potential, Environment of Deposition, Tectonic Setting, and Provenance of Rock Units in the Anambra Basin, Southeastern Nigeria

A total of eight (8) sandstone samples were subjected to sedimentological and inorganic geochemical analyses in the investigation of reservoir potential, environment of deposition, tectonic setting, and provenance of Campano-Maastrichtian rock units in Anambra Basin, southeastern Nigeria. Sedimentological studies reveal that samples of Owelli and Ajali Sandstones are coarse to medium grained, poorly sorted to moderately sorted sediments deposited in a fluvial environment. The heavy mineral assemblages made up of garnet, epidote and staurolite suggest a metamorphic source while tourmaline and zircon suggest igneous or metamorphic sources. The high maturity indices (58.6 to 71.4) as well as the high percentage of quartz (68 to 74%) suggest mature sandstones that can act as reservoir for generated hydrocarbon. The major oxides discriminate function diagram shows active passive margin for the sandstone samples. Quartzose sedimentary provenance was shown for the sediments which have been highly reworked from original igneous and metamorphic sources, possibly from Abakiliki uplift, Oban massif and/or Obudu basement rocks in the southeast. The high chemical index of alteration (averaging 93%) and the low ratio of K2O/Al2O3 (0.02 to 0.11) in the sediments confirms sedimentary recycling and intensive source area weathering