Palynofacies Analysis, Organic Thermal Maturation and Source Rock Evaluation of Sedimentary Succession from Oligocene to Early Miocene Age in X2 Well, Greater Ughelli DepoBelt, Niger Delta Basin, Nigeria

摘要

One hundred and ninety (190) ditch cutting samples of depth range within 20ft- 11820ft (6.09m-3603.7m) from X2 Well Greater Ughelli DepoBelt, Niger Delta Basin were subjected to palynological and palynofacies analysis combined with sedimentological studies, with a view to define its organic thermal maturation and source rock potential. The analysis of the ditch cutting samples were carried out using reflected light microscope for lithologic description while the palynofacies analysis was carried out using transmitted light microscope. The sedimentological analysis reveals forty-nine (49) lithozones and seven (7) lithofacies units, which were deduced based on their mineralogical composition, textural properties, fossil content, homogeneity and heterogeneity of the lithofacies units. The major lithofacies units penetrated in the well are sandstone, shaly sand, sandy shale, clay, sandy clay, clayey sand and shale. Its associated minerals include quartz, feldspar, calcium carbonate and glauconite. Identification of the petroleum play elements and hydrocarbon potential of the X2 Well were equally established. The result from the palynofacies analysis reveals miospores (pollen and spores), woody plant materials (black wood and phytoclast), amorphous organic matter which were used to characterize the well of its kerogen type and maturity. Fifty (50) lithofacies units were subjected to palynofacies analysis, this indicates a potential for hydrocarbon generation. Presence of the dark brown to black wood plant material (black wood and phytoclast) suggest gas-prone for this well. However, the high abundance of light brown to brown colour index of spore/pollen shows that the organic matter of X2 Well falls within the zone of mature main phase liquid hydrocarbon generation (Spore Color Index of 4-6). Palynofacies analysis of X2 Well shows that the well can yield about 70% of oil and 30% of gas (kerogen type II).