Onaiwu D. Oduwa

This project work has attempted to determine the extent to which shale (clays) and silt or siltstones affect porosity, formation water saturation and some other petrophysical properties obtained from data collected from five wells situated in the Brown fields along the coastal swamps in the western onshore region of the Niger -Delta (Brown field). It is established that porosity and permeability of sandstones depends on grain size, sorting, cementation and compaction and these parameters are significantly affected by significant presence of shale (clay) and silt in the formation. Shale formations are believed to be fine-grained, loose and flexible mixtures of clay-sized or colloidal particles. These fine-grained particles affect porosity, which is the percentage of void spaces in the overall rock volume. The work evaluated relevant well and reservoir parameters of interest with respect to the various depths of reservoir sands and correlated wells, using its findings to confirm trends conformable to Niger - Delta basin oil and gas reservoirs. The porosity of the different units of reservoir sands showed variation laterally with porosity values decreasing with a combination of increasing reservoir depth and average shale volume. Consequently, permeability was observed to decrease with increasing depth, though sand Z has high permeability values than sands X and Y lying several feet above it. The reservoir sands X, Y and Z have slightly reduced porosity and permeability due to high volume of clays (shales) and silts (siltstones) often associated with the environment. The porosities of the reservoir sands are good to very good; their permeability moderate to good with high and widespread oil and gas accumulation throughout the Brown field. The hydrocarbon resources are considered exploitable for profit.