Integrated Organic Petrography and Rock-Eval Evaluation of the UDY Well Source Rocks, Niger Delta Basin, Nigeria

This study integrates organic petrography and Rock–Eval pyrolysis to characterize kerogen type, thermal maturity, depositional environment, and hydrocarbon potential of the UDY well source rock interval (4050ft – 4250ft) in Utapate Oilfield, Niger Delta Basin. Petrographic analysis reveals vitrinite-dominated organic matter (74 -76.4 %), moderate liptinite enrichments (23.6 -25.2 %), trace inertinite (< 1%), suggesting a mixed terrestrial-algal organic matter source, typical of marginal marine or delta front settings. Rock–Eval results reveal high TOC (~3.8–4.0 wt.%), indicating good organic richness. S2 values (8–11 mg HC/g) and Hydrogen Index (HI) values (235–290 mg HC/g TOC) demonstrate good remaining generative potential and classify the kerogen as mixed Type II/III. Measured vitrinite reflectance (~0.58%) and Tmax values (427–430 °C) place the samples within the early oil window. High S1 values (8 to 10 mg/g), S1/TOC (>230 mg/g TOC) and elevated PI (0.44–0.47) suggest significant free hydrocarbon presence, likely due to migrated oil or early generation with limited expulsion. The combined results indicate that the UDY well sample interval is a high-quality source rock with considerable retained hydrocarbons and strong potential for both oil and gas generation during continued burial. This combined dataset provides a strong framework for evaluating hydrocarbon potential within the UDY stratigraphic interval and for regional petroleum systems modeling.