Sedimentological and Petrographic Analysis of Side Wall Samples from the Niger Delta Basin, Nigeria: Implications for Depositional Environments and Reservoir Quality.

Abstract

The aim of the present study is to examine the Sedimentological and Petrographic nature of Side Wall Samples from the Niger Delta Basin, Nigeria with a view to establishing their Implications for Depositional Environments and Reservoir Quality. Sidewall samples were collected using a coring tool at depths ranging from 2433ft to 5916ft. A total of 22 samples were labeled, stored in airtight bags, and transported to the lab for analysis. The sedimentological analysis involved determining grain size distribution using a comparator. Lithologic description identified dominant lithology, texture, and color, aiding interpretation of depositional environments and sedimentary facies. A magnifying lens enabled detailed observation of individual grains or mineral crystals. Petrographic analysis used a microscope to identify mineral composition, texture, and fabric of the sediment. Diagenetic features like cementation, compaction, and dissolution were recorded. Acid tests detected carbonate minerals, while hydrocarbon stain tests identified hydrocarbon presence. Visual examination of the samples under a binocular microscope revealed two lithologies, shale and sandstone, with varying percentages of sand and shale. Associated minerals, including mica flakes, quartz crystals exhibiting growth patterns, coal particles, ferruginized materials, silt, and carbonate materials were identified. Results of laboratory analysis suggest that the samples were deposited in a marine environment with varying energy levels. Diagenetic processes include compaction, cementation, and dissolution, which have implications for reservoir quality. The sandstones with well-sorted, angular, and coarse grains have good reservoir potential, while those with poor sorting and sub-angular to sub-rounded grains have limited potential. These findings have important implications for hydrocarbon exploration and development in the area.