GENETIC HOMOGENEITY AND RESERVOIR CONNECTIVITY IN THE NIGER DELTA PETROLEUM SYSTEM: EVIDENCE FROM INTEGRATED MULTIVARIATE BIOMARKER GEOCHEMISTRY

Reservoir connectivity remains a major source of uncertainty in structurally complex deltaic petroleum systems, where fault segmentation and stratigraphic heterogeneity may obscure fluid communication. This study evaluates basin-scale reservoir connectivity across the major depobelts of the Niger Delta Basin using integrated oil geochemical fingerprinting and multivariate statistical analysis. Twenty-five crude oil samples from producing reservoirs in the Northern Delta, Greater Ughelli, Central Swamp, Coastal Swamp, and Shallow Offshore depobelts were analyzed using gas chromatography–mass spectrometry (GC–MS). Diagnostic biomarker parameters were statistically evaluated using hierarchical cluster analysis (HCA), principal component analysis (PCA), correlation analysis, and radar plot visualization. Biomarker distributions indicate strong compositional similarity among the oils, characterized by mixed terrestrial–marine organic matter input, deltaic depositional conditions, and comparable thermal maturity. HCA results reveal tight clustering of samples at low linkage distances, with extensive intermixing of oils from different depobelts. PCA shows that 79.48% of total variance is explained by five principal components, dominated by terrestrial input and redox-sensitive biomarker ratios, while maturity-related parameters contribute secondary variability. The absence of discrete clustering in multivariate space demonstrates that the oils belong to a single dominant genetic family. The integrated geochemical and statistical evidence indicates basin-scale charge system continuity and extensive migration across structurally distinct depobelts. These findings demonstrate that structural compartmentalization in the Niger Delta does not necessarily equate to geochemical isolation.