Papers by Francis Omonefe
Amplitude variation with offset inversion using the reflectivity method
GEOPHYSICS, 2016
Most existing amplitude variation with offset (AVO) inversion methods are based on the Zoeppritz’... more Most existing amplitude variation with offset (AVO) inversion methods are based on the Zoeppritz’s equation or its approximations. These methods assume that the amplitude of seismic data depends only on the reflection coefficients, which means that the wave-propagation effects, such as geometric spreading, attenuation, transmission loss, and multiples, have been fully corrected or attenuated before inversion. However, these requirements are very strict and can hardly be satisfied. Under a 1D assumption, reflectivity-method-based inversions are able to handle transmission losses and internal multiples. Applications of these inversions, however, are still time-consuming and complex in computation of differential seismograms. We have evaluated an inversion methodology based on the vectorized reflectivity method, in which the differential seismograms can be calculated from analytical expressions. It is computationally efficient. A modification is implemented to transform the inversion f...
Site Suitability Study for Solid Waste Dumpsite Selection Using Geospatial-Based Multi-Criteria Analysis in Yenagoa, Bayelsa State Nigeria
Annals of Geographical Studies
Environmental monitory and impact assessment of solid waste dumpsite using multispectral imagery in Yenagoa, Bayelsa state, Nigeria
International Journal of Environmental Science and Technology, 2021
This research presents a novel approach of using open data multispectral imagery as indicators No... more This research presents a novel approach of using open data multispectral imagery as indicators Normalized Difference Vegetation Index, Land Surface Temperature (LST), Green-Shortwave Infrared index and Soil Adjusted Vegetation Index to monitor and assess the impact of dumpsites on the environment in Yenagoa Metropolis, Bayelsa State Nigeria. The outcome uncovers that the LST at the dumpsites was higher than the immediate environment, and the SAVI, NDVI, and G-SWIR values were lower than the immediate surrounding. The high estimations of LST at the dumpsites portray the impact of gases released as a result of decomposition activities, while low values of SAVI and NDVI show vegetation reaction to soil and groundwater pollution due to leachate invasion, lastly G-SWIR indicates discriminations of moisture content of soil and vegetation in leachate infiltration. The outcome shows correlation is significant with the NDVI and G-SWIR value at each of the dumpsites which indicate indirect relationship R 2 . NDVI versus G-SWIR = 0.6271, NDVI versus SAVI = 0.9084, these values indicate highly significant correlated in dumpsite reflectance, while SAVI versus G-SWIR = 0.73 is strongly correlated, indicating increase in waste quantity expected to result in high decomposition, gas emissions and contamination in the environment. The selected heavy metals analyzed for river water are lead (Pb), Zinc (Zn), iron (Fe), cadmium (Cd), nickel (Ni) and chromium (Cr6+). Indicated that all the heavy metals in river water are above the detectable limit by WHO 2011 which imply Epie creek is highly polluted and is due to illegal dumpsites present.
Journal of Asian Scientific Research
Managing resources in marine areas necessitates a thorough understanding of coastal processes. Th... more Managing resources in marine areas necessitates a thorough understanding of coastal processes. This study examines the changes to the shoreline between 1990 and 2021 and assesses how those changes have impacted land use and land cover (LULC). In Yenagoa, Bayelsa State, Nigeria, over a period of 31 years, shoreline changes in the Ikoli River, River Nun, and Oxbow Lake revealed notable oscillations caused by erosion. In particular, band ratios are used to classify LULC maps for each district across the relevant years. The shoreline along the River Nun ranges from 31% to 35%, with 2013 being the highest; along the Ikoli River, it is 33% to 35%, with 2021 being the highest; and along Oxbow Lake, it is 21% to 35%, with 2021 being the highest, according to accurate evaluations of the United States Geological Survey datasets using ArcGIS software. Due to sand mining, boat traffic, heavy rain, fish farming, and oil and gas operations in the area, LULC predicts a sharp decline in vegetation ...
Journal of Engineering Research and Reports
Three surface refraction seismic profiles were conducted in a site targeted for huge construction... more Three surface refraction seismic profiles were conducted in a site targeted for huge construction in an underdeveloped area in Opolo, Yenagoa city to portray some of the subsurface soil engineering characteristics for the purposes of construction. The Generalized Reciprocal Method (GRM) was used to interpret the acquired P and S-wave. Various shallow rock engineering parameters such as Oedometric modulus, Concentration Index, Material Index, Lame’s constant, Density Gradient, Stress Ratio, Shear modulus, Bearing capacity, and N-value were calculated in other to assess the strength of the subsurface from a geophysical and engineering perspective. The values from the seismic velocity and strength parameters indicates that the bedrock layer (layer 3) of the area studied is characterized by more competent rock quality than layer 1 and 2. Hence, the Opolo site is suggested for construction activities with percussive measures.
Journal of Geography, Environment and Earth Science International
Flood has been a serious hazard for the past decades in Nigeria at large. The incidence of 2012 a... more Flood has been a serious hazard for the past decades in Nigeria at large. The incidence of 2012 and 2018 flood disaster in Yenagoa, Amassoma and other parts of the state have not been recover till date and the government is not consigned about the well been of the people. The major causes of the flood are attributed to increased rainfall and lack of drainages including dredging of rivers and disobeying of environmental law and infrastructure failure. Coastal Towns or communities are one of the most affected areas of flood and their farms and fishing implements were washed away by the floodwater in 2012 and 2018 in Bayelsa State. Flood management is needed for provision of time information so quick response can be done as soon as possible. Using SRTM data to produce digital elevation model and IDW Contour, the 3D model from ground data of Yenagoa metropolis using ArcGIS 10.6 to generate and analyze them. As a result of field survey, flood level calculation was made to classified floo...
IJCIRAS, 2020
The AVO Fluid Inversion (AFI) procedure is used to calculate reservoir fluid probability and it h... more The AVO Fluid Inversion (AFI) procedure is used to calculate reservoir fluid probability and it helps to reduce the uncertainty in conventional AVO techniques. By the use of Shuey's AVO gradient and intercept theory, Monte-Carlo simulation, Biot-Gassmann fluid substitution, and Bayesian estimation fluid probability maps was built. Burial depth of interest is between 800m to 2300m. The result from AFI shows that areas penetrated by the wells have gas and oil probability greater than 0.4. The results gave a measured level of confidence that can guide any oil and gas investor to evaluate their chance of drilling success.
Journal of Engineering Research and Reports, 2019
Three surface refraction seismic profiles were conducted in a site targeted for huge construction... more Three surface refraction seismic profiles were conducted in a site targeted for huge construction in an underdeveloped area in Opolo, Yenagoa city to portray some of the subsurface soil engineering characteristics for the purposes of construction. The Generalized Reciprocal Method (GRM) was used to interpret the acquired P and S-wave. Various shallow rock engineering parameters such as Oedometric modulus, Concentration Index, Material Index, Lame's constant, Density Gradient, Stress Ratio, Shear modulus, Bearing capacity, and N-value were calculated in other to assess the strength of the subsurface from a geophysical and engineering perspective. The values from the seismic velocity and strength parameters indicates that the bedrock layer (layer 3) of the area studied is characterized by more competent rock quality than layer 1 and 2. Hence, the Opolo site is suggested for construction activities with percussive measures. Case Study Omonefe et al.; JERR, 4(4): 1-12, 2019; Article no.JERR.48786 2
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Papers by Francis Omonefe