Palynostratigraphic and palynofacies analysis of x and y wells, offshore Niger Delta, Nigeria

Abstract

A detailed palynostratigraphic and palynofacies study was carried out on two shallow offshore wells, codenamed Well X and Well Y, from the Niger Delta Basin, Nigeria. The study is aimed at establishing the age and palaeoenvironment of the sedimentary sequences penetrated by the wells. Standard palynological/palynofacies laboratory procedures were used to free the palynomorphs and palynomacerals from the embedding matrices.
Prepared palynological slides were studied using the Leitz Ortholux II transmitted light microscope. The palynofloral assemblages recorded from the two well sequences include well-preserved palynomorphs such as Zonocostites ramonae, Monoporites annulatus, Retitricolporites irregularis, Cyperaceaepollis sp., Echitricolporites spinosus and Nymphaeapollis clarus among others. The recognition of diagnostic pollen of Cyperaceaepollis sp. and Nymphaeapollis clarus as well as the associated palynomorph assemblage aided the delineation of the well sequences into the P830, P840-P850 and P860 subzones of the P800 palynological zone in the late Miocene. The relative abundance of particulate organic matter (Amorphous Organic Matter (AOM), Phytoclasts and Palynomorphs) revealed the delineation of three palynofacies assemblages, PF-A, PF-B and PF-C, suggesting three distinct paleoenvironments of deposition. These paleoenvironments range from distal shelf through marginal to proximal with varying conditions from oxic, suboxic to anoxic, thus suggesting marginal marine to coastal deltaic environments of deposition for the sedimentary sequences penetrated by the two wells.

Keywords: Late Miocene, Niger Delta, Paleoenvironment, Palynostratigraphy, Palynofacies.