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The Impact of Model Based Offset Scaling Technique on the Amplitude Variation with Offset Responses from 3D Seismic Data Acquired from the Tano Basin, Offshore Ghana

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International Journal of Geosciences 2024年第1期15卷 40-53页

作者： Striggner Bedu-Addo sylvester kojo danuor Aboagye Menyeh Department of Physics Kwame Nkrumah University of Science and Technology Kumasi Ghana

Amplitudes have been found to be a function of incident angle and offset. Hence data required to test for amplitude variation with angle or offset needs to have its amplitudes for all offsets preserved and not stacked. Amplitude Variation with Offset (AVO)/Amplitude Variation with Angle (AVA) is necessary to account for information in the offset/angle parameter (mode converted S-wave and P-wave velocities). Since amplitudes are a function of the converted S- and P-waves, it is important to investigate the dependence of amplitudes on the elastic (P- and S-waves) parameters from the seismic data. By modelling these effects for different reservoir fluids via fluid substitution, various AVO geobody classes present along the well and in the entire seismic cube can be observed. AVO analysis was performed on one test well (Well_1) and 3D pre-stack angle gathers from the Tano Basin. The analysis involves creating a synthetic model to infer the effect of offset scaling techniques on amplitude responses in the Tano basin as compared to the effect of unscaled seismic data. The spectral balance process was performed to match the amplitude spectra of all angle stacks to that of the mid (26°) stack on the test lines. The process had an effect primarily on the far (34° - 40°) stacks. The frequency content of these stacks slightly increased to match that of the near and mid stacks. In offset scaling process, the root mean square (RMS) amplitude comparison between the synthetic and seismic suggests that the amplitude of the far traces should be reduced relative to the nears by up to 16%. However, the exact scaler values depend on the time window considered. This suggests that the amplitude scaling with offset delivered from seismic processing is only approximately correct and needs to be checked with well synthetics and adjusted accordingly prior to use for AVO studies. The AVO attribute volumes generated were better at resolving anomalies on spectrally balanced and offset scaled da

关键词： Amplitude Variation with Offset (AVO) Model Based Offset Scaling Technique Tano Basin

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Petrophysical Evaluation of Cape Three Points Reservoirs

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International Journal of Geosciences 2024年第2期15卷 162-179页

作者： Striggner Bedu-Addo sylvester kojo danuor Larry Pax Chegbeleh Department of Physics Kwame Nkrumah University of Science and Technology Kumasi Ghana Department of Earth Science University of Ghana Accra Ghana

The findings of a study to ascertain and assess the petrophysical characteristics of Cape Three Points reservoirs in the Western basin with a view to describe the reservoir quantitatively using Well Logs, Petrel and Techlog. The investigated characteristics, which were all deduced from geophysical wire-line logs, include lithology, porosity, permeability, fluid saturation, and net to gross thickness. To characterise the reservoir on the field, a suite of wire-line logs including gamma ray, resistivity, spontaneous potential, and density logs for three wells (WELL_1X, WELL_2X, and WELL_3X) from the Tano Cape Three Point basin were studied. The analyses that were done included lithology delineation, reservoir identification, and petrophysical parameter determination for the identified reservoirs. The tops and bases of the three wells analysed were marked at a depth of 1203.06 - 2015.64 m, 3863.03 - 4253.85 m and 2497.38 - 2560.32 m respectively. There were no hydrocarbons in the reservoirs from the studies. The petrophysical parameters computed for each reservoir provided porosities of 13%, 3% and 11% respectively. The water saturation also determined for these three wells (WELL_1X, WELL_2X and WELL_3X) were 94%, 95% and 89% respectively. These results together with the behaviour of the density and neutron logs suggested that these wells are wildcat wells.

关键词： Petrophysical Cape Three Points Reservoirs

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Geophysical Interpretation of Possible Gold Mineralization Zones in Kyerano, South-Western Ghana Using Aeromagnetic and Radiometric Datasets

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Journal of Geoscience and Environment Protection 2015年第4期3卷 67-82页

作者： David Dotse Wemegah Kwasi Preko Reginald Mensah Noye Benjamin Boadi Aboagye Menyeh sylvester kojo danuor Thomas Amenyoh Geophysics Section Department of Physics Kwame Nkrumah University of Science and Technology Kumasi Ghana HydroGeophysics Group (HGG) Department of Earth Sciences University of Aarhus Aarhus Denmark Department of Earth Sciences University of Ghana Legon Ghana

Airborne magnetic and radiometric datasets are used to interpret the geology and geological structural patterns which serve as potential gold mineralization zones in the Kyerano area located at south-western boundary of the prospective Sefwi Gold Belt and the Kumasi Basin in south-western Ghana. The geophysical data processing approach adopted concentrated on mapping geological boundaries, geological structures and possible gold mineralization zones is link to hydrothermally altered zones. The application of the enhancement filtering algorithms such as the reduction to the pole and analytic signal to the magnetic data, as well as the ternary radiometric image aided in the mapping of the mafic metavolcanics, basin metasediments and the belt-type granitoid complexes. The first vertical derivative and tilt angle derivative filters helped to delineate fractures, folds, and the contact zones of the formations such as that of the metavolcanics-metasediments that host the main Bibiani Shear Zone. Lineament analysis of the structures using rose diagram, reveals two main tectonic episodes in the area. These are NE-SW and NNW-SSE trending regional structures which account for about 90% of the extracted structures and are associated with the D1 and D2 deformational episodes of the Birimian Formation respectively. These structures are major fracture systems and play a pivotal role in the localization of gold mineralization in the study area.

关键词： Aeromagnetic Aeroradiometric Fault Shear Zones Structures

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Integrated Geophysical and Geological Mapping of the Lithological and Geological Structures at a Proposed Generator Site

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Journal of Geoscience and Environment Protection 2019年第12期7卷 73-85页

作者： Akwasi Acheampong Aning Vandycke Sarpong Asare David Dotse Wemegah Reginald Mensah Noye Kwasi Preko sylvester kojo danuor Department of Physics Kwame Nkrumah University of Science and Technology Kumasi Ghana

The discovery of oil in commercial quantity in Ghana has led to increase in infrastructural development to provide the needed services to the oil industry. The siting of these industries requires the characterization of the subsurface to determine its suitability to host these facilities. It is in this line that seismic refraction and geo-electrical surveys were conducted on a site near Takoradi, Ghana that has been planned to host a generator and its appurtenances for the oil industry. The objective of the survey was to provide subsurface information critical for the design of earthing system for the proposed generator plant and its appurtenances. The ABEM SAS4000 Terrameter with the Lund imaging system and a 24-channel ABEM Terraloc MK6 were respectively used for the electrical and seismic refraction data collection. The seismic refraction and resistivity results identify three lithological units namely, dry gravel, sand and silty clay layer, water saturated sand and silty clay layer and granodiorites basement rocks. The first layer has a thickness of 10 m and the second layer with thickness in the range of 5 to 10 m. The lithological classifications as obtained from these results correlate with the drill logs. Electrical grounding will be suitable at a depth of 10 m beneath resistivity profile two at a distance between 32 to 52 m.

关键词： Electrical Resistivity Tomography Seismic Refraction Borehole Subsurface Mapping

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Performance of Continuous Wavelet Transform over Fourier Transform in Features Resolutions

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International Journal of Geosciences 2024年第2期15卷 87-105页

作者： Michael K. Appiah sylvester K. danuor Alfred K. Bienibuor Department of Physics Kwame Nkrumah University of Science and Technology (KNUST) Kumasi Ghana Department of Chemical Sciences University of Energy and Natural Resources Sunyani Ghana

This study presents a comparative analysis of two image enhancement techniques, Continuous Wavelet Transform (CWT) and Fast Fourier Transform (FFT), in the context of improving the clarity of high-quality 3D seismic data obtained from the Tano Basin in West Africa, Ghana. The research focuses on a comparative analysis of image clarity in seismic attribute analysis to facilitate the identification of reservoir features within the subsurface structures. The findings of the study indicate that CWT has a significant advantage over FFT in terms of image quality and identifying subsurface structures. The results demonstrate the superior performance of CWT in providing a better representation, making it more effective for seismic attribute analysis. The study highlights the importance of choosing the appropriate image enhancement technique based on the specific application needs and the broader context of the study. While CWT provides high-quality images and superior performance in identifying subsurface structures, the selection between these methods should be made judiciously, taking into account the objectives of the study and the characteristics of the signals being analyzed. The research provides valuable insights into the decision-making process for selecting image enhancement techniques in seismic data analysis, helping researchers and practitioners make informed choices that cater to the unique requirements of their studies. Ultimately, this study contributes to the advancement of the field of subsurface imaging and geological feature identification.

关键词： Continuous Wavelet Transform (CWT) Fast Fourier Transform (FFT) Reservoir Characterization Tano Basin Seismic Data Spectral Decomposition

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Turbidite Dynamics and Hydrocarbon Reservoir Formation in the Tano Basin: A Coastal West African Perspective

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International Journal of Geosciences 2024年第2期15卷 137-161页

作者： Michael K. Appiah sylvester K. danuor Striggner Bedu-Addo Alfred K. Bienibuor Department of Physics Kwame Nkrumah University of Science and Technology (KNUST) Kumasi Ghana Department of Chemical Sciences University of Energy and Natural Resources Sunyani Ghana

This study examines the turbidite dynamics and hydrocarbon reservoir formation in Ghana’s Tano Basin, which is located in coastal West Africa. Through an exploration of geological processes spanning millions of years, we uncover key factors shaping hydrocarbon accumulation, including source rock richness, temperature, pressure, and geological structures. The research offers valuable insights applicable to exploration, management, and sustainable resource exploitation in coastal West Africa. It facilitates the identification of exploration targets with higher hydrocarbon potential, enables the anticipation of reservoir potential within the Tano Basin, and assists in tailoring exploration and management strategies to specific geological conditions of the Tano Basin. Analysis of fluvial channels sheds light on their impact on landscape formation and hydrocarbon exploration. The investigation into turbidite systems unveils intricate interactions involving tectonics, sea-level fluctuations, and sedimentation patterns, influencing the development of reservoirs. An understanding of sediment transport and depositional settings is essential for efficient reservoir management. Geomorphological features, such as channels, submarine canyons, and distinct channel types, are essential in this situation. A detailed examination of turbidite channel structures, encompassing canyons, channel complexes, convex channels, and U-shaped channels, provides valuable insights and aids in identifying exploration targets like basal lag, channel levees, and lobes. These findings underscore the enduring significance of turbidite systems as conduits for sediment transport, contributing to enhanced reservoir management and efficient hydrocarbon production. The study also highlights how important it is to examine the configuration of sedimentary layers, stacking patterns, and angular laminated facies to identify turbidites, understand reservoir distribution, and improve well design. The dynamic nat

关键词： Reservoir Characterization Tano Basin Seismic Data Hydrocarbon Potential Channels Turbidites

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Entomological Survey of Malaria Vectors within the Kumasi Metropolitan AreamA Study of Three Communities： Emena, Atonsu and Akropong

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Journal of Environmental Science and Engineering(B) 2012年第2期1卷 144-154页

作者： Samuel C.K. Tay sylvester K. danuor Andy Morse Caminade Caminade Kingsley Badu Harry Hoffman Abruquah School of Medical Sciences Kwame Nkrumah University of Science and Technology Kumasi 40100 Ghana Meteorology and Climate Science Unit Department of Physics Kumasi 40100 Ghana School of Environmental Sciences University of Liverpool Liverpool L69 7ZT UK Climate and Human Research Unit Centre for Global Health Kenya Medical Research Institute Kisumu 40100 Kenya Department of Pure and Applied Biology Kwame Nkrumah University of Science and Technology Kumasi 40100 Ghana University Hospital Kwame Nkrumah University of Science and Technology Kumasi 40100 Ghana

This study describes the bio-ecology of local Anopheles vectors, their abundance, type and vectoral competence in three communities around Kumasi Metropolis. The study sites were selected based on bio-ecologic zones （urban, peri-urban and rural） which influence habitat and behavior. Pyrethrum spray catch was used in the collection of indoor resting mosquitoes from bedrooms of study communities （June-August 2008）. The identification of mosquitoes was based on morphological keys earlier described. The blood meal taken and the stage of digestion and egg development were also observed. A total of 293 mosquitoes were collected and 50.5% were A. gambiae s.I. Of the three bio-ecologic zones： urban, 53.4% were A. gambiae s.l, 27.2% Culex and 19.4% Mansonia; peri-urban, 58% A. gambiae s. 1 and 42% Culex pipien s. 1 and rural, 40.2% A. gambiae s. 1, and 58.8% Culex sp respectively. About 96.6% of all mosquitoes collected had taken blood meals, with 50% of these being Anopheles gambiae s.I. Our findings indicate that urban rather exhibits rural characteristics and can best be described as ＂urban poor＂. However, more data need to be collected to ascertain this. The anopheline mosquitoes in the study communities are highly endophillic and anthropophagic and thus have high vectoral competence. The authors recommend frequent mosquito surveillance to avert malaria epidemic.

关键词： Malaria vector entomological data anopheline vectors spray catch.

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Validation of TRMM and FEWS Satellite Rainfall Estimates with Rain Gauge Measurement over Ashanti Region, Ghana

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Atmospheric and Climate Sciences 2016年第4期6卷 500-518页

作者： Leonard K. Amekudzi Marian A. Osei Winifred A. Atiah Jeffrey N. A. Aryee Maureen A. Ahiataku Emmanuel Quansah Kwasi Preko sylvester K. danuor Andreas H. Fink Meteorology and Climate Science Unit Department of Physics Kwame Nkrumah University of Science and Technology Kumasi Ghana Ghana Meteorological Agency Accra Ghana Karlsruhe Institute of Technology (KIT) Institute of Meteorology and Climate Research Karlsruhe Germany

Satellite rainfall estimates have predominantly been used for climate impact studies due to poor rain gauge network in sub-Saharan Africa. However, there are limited microscale studies within the sub-region that have assessed the performance of these satellite products, which is the focus of the present study. This paper therefore considers validation of Tropical Rainfall Measuring Mission (TRMM) and Famine Early Warning System (FEWS) satellite estimates with rain gauge measurements over Ashanti region of Ghana. First, a consistency assessment of the two gauge data products, the Automatic Rain Gauge (ARG) and Ghana Meteorological Agency (GMet) Standard Rain Gauge (SRG) measurements, was performed. This showed a very good agreement with correlation coefficient of 0.99. Secondly, satellite rainfall products from TRMM and FEWS were validated with the two gauge measurements. Validation results showed good agreement with correlation coefficients of 0.6 and 0.7 for TRMM and FEWS with SRG, and 0.87 and 0.86 for TRMM and FEWS with ARG respectively. Probability Of Detection (POD) and Volumetric Hit Index (VHI) were found to be greater than 0.9. Volumetric Critical Success Index (VCSI) was 0.9 and 0.8 for TRMM and FEWS respectively with low False Alarm Ratio (FAR) and insignificant Volumetric Miss Index (VMI). In general, relatively low biases and RMSE values were observed. The biases were less than 1.3 and 0.8 for TRMM and FEWS-RFE respectively. These indicate high rainfall detection capabilities of both satellite products. In addition, both TRMM and FEWS were able to capture the onset, peak and cessation of the rainy season, as well as the dry spells. Although TRMM and FEWS sometimes under/overestimated rainfall, they have the potential to be used for agricultural and other hydro-climatic impact studies over the region. The Dynamic-Aerosol-Cloud-Chemistry Interactions in West Africa (DACCIWA) project will provide an improved spatial gauge network database over the study are

关键词： Rain Gauge Validation TRMM and FEWS-RFE DACCIWA Project Ashanti Region

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