Browsing by Author "Opuwari, Mimonitu"
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Item 3D static modeling and CO2 static storage estimation of the hydrocarbon-depleted charis beservoir, Bredasdorp basin, South Africa(Natural Resources Research, 2023) Afolayan, Blessing Ayotomiwa; Opuwari, Mimonitu; Mackay, EricAn essential greenhouse gas effect mitigation technology is carbon capture, utilization and storage, with carbon dioxide (CO2) injection into underground geological formations as a core of carbon sequestration. Developing a robust 3D static model of the formation of interest for CO2 storage is paramount to deduce its facies changes and petrophysical properties. This study investigates a depleted oilfield reservoir within the Bredasdorp Basin, offshore South Africa. It is a sandstone reservoir with effective porosity mean of 13.92% and dominant permeability values of 100–560 mD (1 mD = 9.869233 × 10–16 m2). The petrophysical properties are facies controlled, as the southwestern area with siltstone and shale facies has reduced porosity and permeability. The volume of shale model shows that the reservoir is composed of clean sands, and water saturation is 10–90%, hence suitable for CO2 storage based on petrophysical characteristics. Static storage capacity of the reservoir as virgin aquifer and virgin oilfield estimates sequestration of 0.71 Mt (million tons) and 1.62 Mt of CO2, respectively. Sensitivity studies showed reservoir depletion at bubble point pressure increased storage capacity more than twice the depletion at initial reservoir pressure. Reservoir pressure below bubble point with the presence of gas cap also increased storage capacity markedly.Item Determination of total organic carbon content using Passey's method in coals of the central Kalahari Karoo Basin, Botswana(2022) Mabitje, Mamphedi Sylvia; Opuwari, MimonituThis paper focuses on determining total organic carbon (TOC) from boreholes in the Kalahari Basin, Botswana, using Passey's method. The Kalahari Karoo basin is one of several basins in southern Africa filled with Late Carboniferous to Jurassic sedimentary strata that host Permian age coal seams. Nine exploration boreholes (wells) drilled in the central Kalahari Karoo basin are used to determine the Total Organic Carbon potential. Vitrinite reflectance (Ro), proximate and ultimate analyses were conducted on cored coal intervals. Passey's ΔLogR method applied in this study employs resistivity and porosity logs to identify and quantify potential source rocks. Results of Passey's method compared with laboratory-measured carbon showed that Passey's method effectively identifies coal intervals. In terms of TOC calculations, the method works poorly in coal metamorphosed by dolerite intrusions.Item Geological and geophysical evaluation of the Thebe field, Block XX, offshore Western Australia(University of the Western Cape, 2013) Bailey, Brett B.; Opuwari, MimonituThe North West Shelf of Australia is a prolific gas province. The Thebe Gas Field is situated within the northern central Exmouth Plateau in the Northern Carnarvon Basin. The Exmouth Plateau is a submerged continental block whose culmination lies at about 800m below sea level. The seismic data used for this study is the HEX07B survey which was conducted in 2007. The objective of this study was to interpret all available seismic data, of which six horizons were picked, generating two-way-time structure maps and an average velocity map, performing depth conversion and generating various depth maps. The horizons picked were the economic basement, Triassic Mungaroo, Murat Siltstone, Muderong Shale, Gearle Siltstone and the Sea Bed. The horizon of interest was the Triassic Mungaroo Formation and therefore it was the only horizon with an average velocity map. The seismic sections were used in conjunction with the structure maps generated to identify possible locations for appraisal wells to be drilled. Prospect X was identified on the basis of amplitude and structure present within the Triassic Mungaroo Formation. The final task was to calculate the volumes present and a Monte-Carlo Simulation was used for this. The results obtained showed that Prospect X has a good petroleum system in place. The Mungaroo Formation is identified as being the possible source and reservoir rock, the Muderong Shale is the seal, structural traps are provided by large fault block and faults provided the migration pathways from the source in to the reservoir. The volumes were calculated using three areas identified on the structure maps by three closing contours. These areas are the P90, P50, P10 and the volumes for the gas in place were as follows, P90 = 893 Bcf (0.9Tcf), P50 = 1128 Bcf (1.1 Tcf), P10 = 1367 Bcf (1.4Tcf). Using the various parameters the probability of success for Prospect X was calculated to be 20%.Item The impact of detrital minerals on reservoir flow zones in the North Eastern Bredasdorp basin, South Africa, using core data(MDPI, 2022) Opuwari, Mimonitu; Ubong, Moses Okon; Jamjam, SimamkeleThe present study uses core data to group reservoirs of a gas field in the Bredasdorp Basin offshore South Africa into flow zones. One hundred and sixty-eight core porosity and permeability data were used to establish reservoir zones from the flow zone indicator (FZI) and Winland’s methods. Storage and flow capacities were determined from the stratigraphy-modified Lorenz plot (SMLP) method. The effects of the mineralogy on the flow zones were established from mineralogy composition analyses using quantitative X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). Results reveal five flow zones grouped as high, moderate, low, very low, and tight reservoir rocks.Item Metal–metal correlation of biodegraded crude oil and associated economic crops from the Eastern Dahomey Basin, Nigeria(MDPI, 2022) Mohammed, Saeed; Opuwari, Mimonitu; Titinchi, SalamThe presence of heavy metals in plants from oil sand deposits may reflect mineralization resulting from petroleum biodegradation. Petroleum composition and heavy metal analyses were performed using thermal desorption gas chromatography and atomic absorption spectrophotometry on oil sand and plant root samples from the same localities in the Dahomey Basin. The results from the oil sand showed mainly heavy-end hydrocarbon components, humps of unresolved complex mixtures (UCM), absences of C6-C12 hydrocarbon chains, pristane, and phytane, indicating severe biodegradation. In addition, they showed varying concentrations of vanadium (2.699–7.708 ppm), nickel (4.005–11.716 ppm), chromium (1.686–5.733 ppm), cobalt (0.953–3.223 ppm), lead (0.649–0.978 ppm), and cadmium (0.188–0.461 ppm). Furthermore, these heavy metals were present in Citrus, Theobroma Cacao, Elaeis guineensis, and Cola.Item New insights in the evaluation of reserves of selected wells of the Pletmos Basin offshore South Africa(One Petro, 2016) Elamri, Samir; Opuwari, MimonituThe area evaluated has similar structural styles and settings as the producing neighboring fields of F-A and E-M in the adjacent Bredasdorp basin Offshore South Africa. The main objective of this study is to create a 3-D-static model and estimate hydrocarbon reserves. Based on log signatures, petrophysical properties and structural configurations, the reservoirs were divided vertically into three reservoir units in order to be properly modelled in 3-D space. The thicknesses of the layers were determined based on the vertical heterogeneity in the reservoir properties. Facies interpretation was performed based on log signatures, core description and previous geological studies. The volume of clay and porosity was used to classify facies into five units of sand, shaly sand, silt, and clay. From petrophysical interpretation, a synthetic permeability log was generated in the wells which ties closely with core data.Item An overview of trace elements in soils of Keana-Awe Brine-Fields, Middle Benue Trough, Nigeria(Taylor & Francis: STM, Behavioural Science and Public Health Titles, 2017) Sallau, Adamu; Momoh, Abuh; Opuwari, Mimonitu; Akinyemi, Segun; Lar, UriahThe objective of this study was to determine the concentration of trace elements in soils of Keana-Awe brine-fields. Composite soil samples were randomly collected at a depth of 0–15 cm and were analysed for molybdenum, zinc, arsenic, lead, cobalt, chromium, copper, barium and nickel using Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). Quantification of the degree of soil contamination by these trace elements was carried out using the enrichment factor (EF) and the geo-accumulation index (Igeo). The data were subjected to principal component analysis (PCA). The average concentrations were 1.56 ppm molybdenum, 1116.42 ppm zinc, 23.80 ppm arsenic, 71.40 ppm lead, 17.64 ppm cobalt, 237.35 ppm chromium, 24.16 ppm copper, 254.67 ppm barium and 143.71 ppm nickel. Cobalt, nickel and chromium showed positive loadings in component 1 with a total variance of 29.56%. Zinc, copper and lead showed positive loadings in component 2 with a total variance of 18.79%, while copper showed negative loading in component 3 with a total variance of 14.79%. Considering the concentration of trace elements in the soils and statistical analyses, we conclude that soils of the study area were severely enriched in molybdenum, cobalt, chromium, copper, barium, nickel, while arsenic and zinc are in excessive concentrations in the soils. These trace elements could have originated from geogenic and anthropogenic sources.Item Petrophysical interpretation and fluid substitution modelling of the upper shallow marine sandstone reservoirs in the Bredasdorp Basin, offshore South Africa(Springer Nature, 2020) Magoba, Moses; Opuwari, MimonituThe fluid substitution method is used for predicting elastic properties of reservoir rocks and their dependence on pore fluid and porosity. This method makes it possible to predict changes in elastic response of a rock saturation with different fluids. This study focused on the Upper Shallow Marine sandstone reservoirs of five selected wells (MM1, MM2, MM3, MM4, and MM5) in the Bredasdorp Basin, offshore South Africa. The integration of petrophysics and rock physics (Gassmann fluid substitution) was applied to the upper shallow marine sandstone reservoirs for reservoir characterisation. The objective of the study was to calculate the volume of clay, porosity, water saturation, permeability, and hydrocarbon saturation, and the application of the Gassmann fluid substitution modelling to determine the effect of different pore fluids (brine, oil, and gas) on acoustic properties (compressional velocity, shear velocity, and density) using rock frame properties.Item Sandstone reservoir zonation of the north-western Bredasdorp Basin South Africa using core data(Elsevier, 2021) Opuwari, Mimonitu; Dominick, NehemiahThis study delineates sandstone reservoir flow zones in the north-western Bredasdorp Basin, offshore South Africa, using conventional core porosity and permeability data. The workflow begins by integrating sedimen- tology reports and logs to identify lithofacies before evaluating petrophysical flow zones. Three lithofacies were classified as lithofacies 1, 2, and 3. Lithofacies 1 is a silty shale and bioturbated sandstone, lithofacies 2 is an interbedded sandstone and shale, with very fine sandstone with well-sorted grains, and is heavily cemented. Conversely, lithofacies 3 is a fine-to medium-grained sandstone with minor shale that is moderately cementation. Lithofacies 3 is ranked as the best reservoir rock, followed by lithofacies 2 and 1. Four independent reservoir zonation methods (permeability anisotropy, Winland r35 pore throat, flow zone indicator (FZI), and stratigraphic modified Lorenz lot (SMLP)) were applied to core samples from three wells (MO4, MO5, and MO6). The core samples predominantly had slight anisotropic permeability (0.5–1.1). The reservoir units were ranked into four flow zone categories as tight, very low, low, and moderate, based on porosity and permeability, and calculated parameters.Item Shale-gas potential from Cretaceous succession in South Africa’s orange basin: insights from integrated geochemical evaluations(Taylor & Francis, 2022) Opuwari, Mimonitu; Yelwa, Nura Abdulmumini; Mustapha, Khairul AzlanShale sediments were collected from four Cretaceous stratigraphic units across four explorations well locations in South Africa’s Orange Basin and analysed to determine organic-matter characteristics, such as amount, quality, thermal maturity, and their viability as gas resources. The geochemical results show that the Cretaceous shales contain moderate organic quantities, as shown by TOC averagely up to 1.29%. The organic facies consist primarily of Type III kerogen, as proven alongside low hydrogen indexes between 40 and 133 mg HC/g TOC. As seen under a reflected light microscope, the dominance of such land plant-rich organic matter is in harmony with the significant amount of Vitrinite macerals. These organic sediments can produce primarily gas when they mature. The geological and geochemical properties of the organic sediments, chiefly Type III kerogen, generate both wet and dry gas, particularly when adequate thermal maturity is enhanced at deeper locations. Thus, the Orange Basin is considered promising for shale gas exploration and production.Item Source rock evaluation of Afowo clay type from the Eastern Dahomey Basin, Nigeria: Insights from different measurements(Springer Nature, 2020) Mohammed, Saeed; Opuwari, Mimonitu; Titinchi, SalamThe Cretaceous Afowo Formation in the Eastern Dohamey Basin is characterized by an admixture of lithofacies ranging from sandstones, claystones, shales, clays, sand/shale, and sand/clay intercalations. The sandy facies, a mix of sandstone, clay, shale, and intercalations, contain biodegraded hydrocarbons while the shales and claystones that underlie it are rich in organic matter. The hydrocarbon-bearing interval is commonly referred to as the oil sand or tar sand. In this study, Afowo clay type underlying an outcrop of the oil sand was appraised for its hydrocarbon potential with loss on ignition, thermogravimetry, and rock evaluation pyrolysis.Item Static reservoir modeling using stochastic method: A case study of the cretaceous sequence of Gamtoos Basin, Ofshore, South Africa(Springer, 2021) Ayodele, Oluwatoyin Lasisi; Chatterjee, Tapas; Opuwari, MimonituGamtoos Basin is an echelon sub-basin under the Outeniqua ofshore Basin of South Africa. It is a complex rift-type basin with both onshore and ofshore components and consists of relatively simple half-grabens bounded by a major fault to the northeast. This study is mainly focused on the evaluation of the reservoir heterogeneity of the Valanginian depositional sequence. The prime objective of this work is to generate a 3D static reservoir model for a better understanding of the spatial distribution of discrete and continuous reservoir properties (porosity, permeability, and water saturation). The methodology adopted in this work includes the integration of 2D seismic and well-log data. These data were used to construct 3D models of lithofacies, porosity, permeability, and water saturation through petrophysical analysis, upscaling, Sequential Indicator Simulation, and Sequential Gaussian Simulation algorithms, respectively. Results indicated that static reservoir modeling adequately captured reservoir geometry and spatial properties distribution. In this study, the static geocellular model delineates lithology into three facies: sandstone, silt, and shale. Petrophysical models were integrated with facies within the reservoir to identify the best location that has the potential to produce hydrocarbon. The statistical analysis model revealed sandstone is the best facies and that the porosity, permeability, and water saturation ranges between 8 and 22%, 0.1 mD (<1.0 mD) to 1.0 mD, and 30–55%. Geocellular model results showed that the northwestern part of the Gamtoos Basin has the best petrophysical properties, followed by the central part of the Basin. Findings from this study have provided the information needed for further gas exploration, appraisal, and development programs in the Gamtoos Basin.Item Untitled(2021) Yelwa, Nura A.; Mustapha, Khairul A.; Opuwari, Mimonitu; Aziz, Azharuddin A.Aptian to Campanian sediments from the Western ofshore to Central Orange Basin were studied by integrating molecular geochemistry, inorganic and isotopic studies to recognize their geochemical characteristics via the reconstruction of the Orange basin’s paleoweathering, paleosalinity, paleovegetation, paleoclimate, and tectonic records. Molecular analyses of both aliphatic and aromatic compounds reveal an input dominantly from a marine source. The source rocks accumulated in a reduced, anoxic, saline water column. Based on various biomarker proxies and vitrinite refectance data, some samples are thermally mature to produce petroleum, while others are not. According to the V/Ni ratio, samples from the Orange Basin in South Africa are mainly anoxic, with only a few samples ranging from suboxic to anoxic. This is congruent with biomarker and isotope analyses that further indicate the presence of marine-derived source rocks with some terrestrial remains gener ating hydrocarbons. The investigated sediments are made up of intermediate igneous rocks that have undergone moderate chemical weathering. Geochemical fgures on tectonic setting discriminant function diagrams revealed a continental rift of passive margin settings. As a result, the extrapolated crustal processes are directly analogous to the genesis and evolution of the Orange Basin, demonstrating Gondwana’s breaking up and the opening of the Atlantic Ocean Margin.