ABSTARCT
This study is an attempt to establish the presence of the elements of a petroleum system, the age and environment of deposition of these elements along BIS-01 Well bore through microscopic examination of ditch cutting samples. Seventy-two (72) ditch cutting samples of depth range within 4500ft-11460ft (1372m-3493m) from BIS-01 Well, Greater Ughelli Depobelt, Niger Delta Basin were subjected to microscopic examination to determine their lithological features. The examination revealed four (4) lithofacie units comprising of sandstone, shale, sandy-shale and shaly-sand. The lithofacie units were deduced based on physical and textural properties of the samples. From the resulting lithological log, the top-most shale facie which is about 460ft thick was interpreted to be the cap/seal rock. The sand, sandy-shale and shaly-sand lithofacies constitute the reservoir rock of about 1920ft thick. The lower most, massive shale facie of about 3540ft thickness was interpreted to be the probable source rock for the petroleum system in this field. In a quest to further reduce the resolution of interpretation, forty-nine (49) lithozones were established within these elements. Biostratigraphic interpretation was also carried by analyzing biofacies data, Palynomorph (P-Zone) data and Foram (F-Zone) data. The result of these analysis was then aligned with the Niger Delta chronostratigraphic chart to determine the key bounding surfaces of sediments along the well bore as well as the age of the sediments. Five (5) maximum flooding surfaces and eight (8) sequence boundaries were revealed. The maximum flooding surfaces with their shale markers and interval are; 19.4Ma Oghara shale at 6265ft, 20.2Ma Alabamina 2 at 6688ft, 23.2Ma Bolivina 26 at 7247ft, 26.2Ma Alabamina 1 at 7771ft, 28.1Ma Bolivina 27 at 10280ft. The estimated sequence boundaries are 17.7Ma at 5899ft, 20.4Ma at 6434ft, 20.7Ma at 6688ft, 22.2Ma at 6982ft, 23.7Ma at 7325ft, 24.9Ma at 7485ft, 27.3Ma at 8186ft, 29.3 Ma at 10602ft). The thick bottom shale interpreted to be the possible source rock aligns with the Bolivina 27 shale marker (28.1 Ma), the interpreted reservoir lies between 17.7 Ma – 23.7 Ma age range. The caprock lies above the Oghara shale marker. A sequence stratigraphic model embracing foram abundance pattern shows the abundance of calcareous foraminifera. On this basis, shelf-based environment of deposition was interpreted. The results show the presence of the key elements of a petroleum system which are emplaced in a favorable timing of event.
