| Abstrakt: |
Integration of core and petrographic thin sections within ca. 84 ft. interval of the Eperon-08 well, onshore Niger Delta, enabled interpretations of depositional environment, age and reservoir quality of the H-4000 reservoir. Sedimentological analysis revealed five lithofacies within the cored section, including cross-bedded fine- to medium-grained sandstone, parallel laminated sandstone, crudely cross-bedded coarse-grained to gravely sandstone, wave-rippled sandy heteroliths and parallel laminated mudstone. Three genetic units were derived by grouping co-occurring lithofacies: coastal plain, fluvial channel, and tidal channel. Occasional Skolithosand Ophiomorphashow mostly rare to moderate bioturbation intensity. Biostratigraphic analysis of 30 core plugs showed the occurrence of sparse planktonic and rich benthic foraminifera such as Catapsydrax dissimilis, Globigerinoides primordiusand Hanzawaia strattoni, Nonionella aurisand Pseudononion japonicum,respectively.The dominant calcareous nannofossils species were Helicosphaera ampliapertaand Cyclicargolithus floridanus, while the palynoflora is quantitatively dominated by rainforest and brackish swamp species that include Psilatricolporites crassusand Retitricolporites irregularis.An Early Miocene age was inferred using the maker species. Petrographic analysis of 15 thin-section slides showed the samples are poorly consolidated, very fine- to coarse-grained subarkose sandstones, with moderate to good sorting of angular to subrounded grains. Visual estimate of intergranular porosity ranged from ca. 12%–16%, with evident dissolution-induced secondary porosity increasing total porosity to ca. 20%–26%, which generally decreased with increasing matrix content. The preponderance of point and planar grain-to-grain contact types and widespread secondary porosity suggest an eogenetic diagenesis stage for the interval. These results have important implications for reservoir quality and property modelling. |
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