Sedimentary Facies and Grain Size Distribution; Insights into Ogwashi-Asaba Formation, Niger Delta Basin

Abstract

The Niger Delta is renowned for being one of the most productive hydrocarbon
provinces globally. This productivity is primarily attributed to its complex
geological history, which is marked by intricate stratigraphy and various
sedimentary facies. These sedimentary facies, which are distinct bodies of sediment
with specific characteristics, provide essential information about past
environments and sedimentary processes, about the complex stratigraphy and
diverse sedimentary facies. Stratigraphic sequences in the Niger Delta include
alternating layers of sandstones, shales, and siltstones. Sediment samples were
collected with cores too, from the Ogwashi-Asaba formation, and a detailed field
analysis was documented. Grain size, petrographic, and geochemical analysis were
carried out in the lab, from the samples collected. The analyzed parameters suggest
that the sandstone samples from the Ogwashi-Asaba Formation are
predominantly fluviatile. Graphic Mean (Mz) ranges from 1.4 to 2.1 phi. Grain
Size Composition 2-20% very fine sand, 6-66% fine sand, 45-87% medium to
coarse sand, and 70-100% very coarse sand. Sorting (σ1) ranges from 1.1 to 2.1
phi, with 64.71% of sediments being very poorly sorted and 35.29% poorly sorted.
Graphic Skewness (Sk) ranges from -0.6 to +0.5, indicating varying energy
conditions. Graphic Kurtosis (KG): Ranges from 0.8 to 1.9, with curves varying
from leptokurtic to platykurtic. These sedimentary processes shaping the
Ogwashi-Asaba formation creates a diverse stratigraphy and a variety of
sedimentary facies. Each provides valuable insights into past environmental
conditions and sedimentary dynamics. A comprehensive understanding of these
processes enhances the potential for hydrocarbon exploration and the reservoir
characterization of the province