Petroleum Geology Of Niger Delta And Evaluation Of The Hydrocarbon Potential In Stubb Creek Marginal Oil Field

Niger delta is one of the most petroliferous basins, and its known oil and gasresources rank the province as the twelfth largest in the world. The features ofpetroleum geology of the Niger delta, whose evolution history could be divided intoearly and late stages, are very complicated. In the Niger delta, some macrostructuraltrends and structural styles induced by the gravitational spreading are predominant.The basement of the Niger delta is composed of Precambrian metamorphosedrocks, igneous and Jurassic volcanic and the depositional sequences attain Cretaceous,Tertiary and Quaternary which consist of three sedimentation cycles with obviousdiachroneity. In response to variable rates of subsidence and sediment supply, thediscrete depobelts were formed in various depositional stages.Petroleum in the Niger Delta is produced from sandstone and unconsolidatedsands predominantly in the Agbada Formation. Characteristics of the reservoirs in theAgbada Formation are controlled by depositional environment and by depth of burial.The primary seal rock in the Niger Delta is the interbedded shale within the AgbadaFormation. The shale provides three types of seals-clay smears along faults,interbedded sealing units against which reservoir sands are juxtaposed due to faulting,and vertical seals. The marine shale within the upper Akata Formation and the shaleinterbedded with paralic sandstone within the lower Agbada Formation are the mostefficient source rocks for the Niger Delta oils, which are considered to be good andbest source rocks, and their organic-matter belongs to â…¢- and â…¡-type.Most known traps in the Niger Delta fields are structural although stratigraphictraps are not uncommon. The reservoir types involve roller anticlines, collapsed creststructures, diapiric structures, faulted noses and blocks, as well as stratigraphic-lithological reservoirs. The hydrocarbon distribution was strictly governed by faultsand their assembles, trap types, lithological assembles and their configurations.The structural styles in the Stubb Creek marginal oilfield mostly involveanticlines, faulted blocks and noses. The fault-anticlinal, faulted and fault-lithologicalreservoirs are also common in the Stubb Creek oilfield. The depositional covers attain7 layers with hydrocarbon which consist of 4 oil layers and 3 gas layers. Thecalculation results by inputting varying parameter show that there is abundanthydrocarbon in the Stubb Creek oilfield. The petroleum mainly distributes in thefootwall, and the conventional structural traps, deep traps, stratigraphic- lithologicaltraps and footwall traps of the syndepositional faults should be the importantexploration objectives.By comprising the Stubb Creek marginal oilfield with other similar oilfields inthe adjacent regions, this dissertation concludes that the C9.0, D3.0, D5.0 and D8.0oil-layers in the Stubb Creek oilfield have commercial development values, and thefinal recoverable reserves may be exceed 5 million tons.