PALYNOSTRATIGRAPHY, PALEOCLIMATE AND SEQUENCE STRATIGRAPHIC ANALYSIS OF EMI-4 WELL, NIGER DELTA, NIGERIA

Abstract

Palynostratigraphic, Paleoclimatic and Sequence Stratigraphic analyses were conducted in a section of Emi-4 well, Offshore Niger Delta to establish palynozones, relative age, paleodepositional setting and reconstruct paleoclimatic changes overtime within the section of the well. The intercalation of the sandy and shaly intervals of the section evidenced from lithologic, textural, and wire line log data suggested that the entire studied interval belong to the Agbada Formation. Thirty-six (36) ditch cuttings within 6,158 ft - 10,452 ft were subjected to standard palynological analysis involving sample maceration with 10% HCl and 40% HF acids to remove carbonates and siliceous components, neutralization with distilled water and sieving through 5-micron sieve, followed by separation of palynomorphs from residue and mounting on glass slides for microscopic analysis. Recovered palynomorphs are marked by dominance of pollen and spores over dinoflagellate cysts. The occurrences of age diagnostic palynomorphs such as Echiperiporites estelae, Belskipollis elegans, Verrutricolporites rotundiporus, Retribrevitricolpites protrudens, Pachydermites diederixi, Peregrinipollis nigericus, Cassoretitriletes vanraadshooveni, Magnastriatites howardii, Retistephanocolpites gracilis, Racemonocolpites hians, Praedapollis flexibilis, Elaeis guineensis, and Zonocostites ramonae at some intervals of the studied wells suggest early Miocene to late Miocene age. Three distinct interval palynostratigraphic zones were delineated using the international stratigraphic guide for the establishments of biozones, they are Racemonocolpites hians - Cyperaceaepollis sp. Zone (early Miocene); Gemmemonoporites sp. - Magnastriatites howardi Zone (middle Miocene) and Pachydemites diederixi - Retibrevitricolporites protrudens Zone (late Miocene). The sequence stratigraphic study identified Maximum Flooding Surfaces (MFS) within the well intervals along with the identification of Highstand Systems Tract (HST) and Transgressive Systems Tract (TST). Paleoclimatic interpretations based on palynological evidence suggest the presence of wet climatic conditions throughout the studied intervals, characterized by abundant mangrove, freshwater, and rainforest taxa.