Browsing by Author "Bishanga, Januarius Matata"

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    3D geocellular modeling for reservoir characterization of lacustrine turbidite reservoirs: Submember 3 of the third member of the Eocene Shahejie Formation, Dongying depression, Eastern China
    (Elsevier, 2022) Lutome, Marco Shaban; Lin, Chengyan; Chunmei, Dong; Zhang, Xianguo; Bishanga, Januarius Matata
    3D geocellular modeling is increasingly essential in the petroleum industry; it brings together all petroleum disciplines, and it is commonly used in simulation and production forecast. However, modeling slope and deep-water turbidite reservoirs using conventional modeling methods pose a significant challenge due to the structural complexity and thin-beds associated with these reservoirs. Through the innovative modeling technology of PaleoScan, the reservoirs in Sub member 3 of the third member of the Shahejie Formation are modeled to understand the structural framework. The resulting model is populated with petrophysical properties i.e., porosity and permeability to predict their lateral and vertical distribution within these sandstone reservoirs. The study suggests that the reservoir in the highstand system tract (HST) is characterized by the clinoforms configuration framework. The reservoir is highly faulted mainly in the northern and southeastern parts of the depression. The sedimentary layers are deposited across the slope and downlapping, thinning, and terminating toward to the west. The two isochore surface maps reveal sediment thickness variation and depositional trends within each individual depositional layer. The zones or areas that corresponds to low values on the thickness maps suggest minor uplifts associated with intensive faulting in the Eocene period. These topographical highs played a fundamental role in distributing the sediments delivered to the basin from distant sources. The maps reveal that sediments that filled the basin appear to come from different source points, primarily delivered from the north, southeast, and northeast of the basin with varying depositional trends. The modeled porosity and permeability indicate that the delta fed turbidite reservoirs are characterized by medium to high porosity values of 10e20% and low to medium permeability values of 30-410mD, respectively. The porosity values increase to the southeast and toward the basinwards (west) while permeability varies within the individual sedimentary layers. The distribution of porosity and permeability is not uniform vertically. This suggests the presence of mixed none-reservoir layers with locally and periodically deposited sandstone reservoirs within the stratigraphic during rapid delta progradation. The HST is characterized by six different delta progradation cycles; each phase produced locally deposited lacustrine turbidite sandstones in the basin, which are essential reservoirs in this Formation. The innovative PaleoScan interpretation technology has successfully created a high-resolution 3D reservoir model of this complex geology-such innovative technology is vital to similar complex geology globally.
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    Origin and source characterization of methane in the shallow-water environment of Southern Lake Tanganyika Rift Basin, Tanzania
    (Current Science Association, 2021) Bishanga, Januarius Matata; Qiang, Jin
    Lake Tanganyika, located in the western part of Tanzania between 3°S and 9°S lat, harbours hydrocarbon and non-hydrocarbon gases in its northern and southern shallow-water environment. In this study, a geochemical analysis of stable carbon and hydrogen isotopes and an interpretation of individual gas molecular composition were done in order to determine the origin and composition of the naturally occurring hydrocarbon gases in Tanganyika Basin. Nitrogen, a non-hydrocarbon gas is a major component (76.69%–78.31%) by volume percentage followed by methane (11.68%–12.94%) and other higher hydrocarbons (0.16%–1.63%). The isotopic composition of carbon δ 13C1 and hydrogen δ DC1 ranges from –65.32‰ to –65.81‰ and –272.5‰ to –275.9‰ respectively. The isotopic compositions of ethane (δ DC2 = –36.7‰ to –35.2‰) and propane (δ DC3 = –31.3‰ to –27.5‰) reflect the thermogenic origin of these higher hydrocarbons. According to molecular characterization of carbon and hydrogen isotope ratios and δ D-values, methane gas falls in the biogenic origin category and is formed by carbon dioxide reduction. The isotopic composition of CO2 varies between –8.6‰ and –3.4‰. CO2 reduction is also regarded as a mechanism of biogenic methane formation based on carbon isotope fractionation factors (greater than 0.16).
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    Trace and rare earth element geochemistry of organic-rich sediments in the lacustrine Rukwa rift basin, Tanzania: implications for paleoproductivity, paleosalinity, and redox conditions
    (Springer Nature, 2021) Bishanga, Januarius Matata; Qiang, Jin
    Coal and mudstone beds in the Namwele coalfield, lacustrine Rukwa rift basin belong to the Late Carboniferous to Early Permian age. However, their origin, depositional environment, and organic matter enrichment in such a setting have not been well studied. In this study, samples were collected from the field outcrops and analyzed for their hydrocarbon generation potential, trace element (TE), and rare earth element (REE) proxies to examine their origin, paleoproductivity, organic matter enrichment, paleosalinity, and redox conditions. The results show that the total organic contents (TOC) of the investigated samples range from 3.74 to 13.6%, with an average of 7.21%. The anomalous TOC is a proof that sediments deposited in an oxic condition and low sedimentation rate. Concentrations and ratios of various redox indicators such as vanadium, nickel, copper, chromium, uranium, and thorium (V/Cr, V/(V + Ni), Ni/Co, and U/Th) suggest that the organic-rich sediments had strong terrestrial organic matter input and deposited under oxic conditions. The TOC versus redox ratios show negative correlation coefficients proving that oxic conditions are not suitable for organic matter preservation. According to the boron/gallium (B/Ga) ratio, water salinity ranges between 0.2 and 4.15 during sedimentation, indicating a freshwater environment. The more significant content of the trace elements Ni and Cu implies a high flux of organic matter. Lanthanum/ytterbium (La/Yb)n ratio is an indicator for characterizing different enrichment levels between light REE and heavy REE. The results show that samples are enriched in light REE, with (La/Yb)n, indicating a low sedimentation rate. These findings contribute to studies of the same sedimentary environment settings and further extend our knowledge of the potential organic-rich resources in the Rukwa rift basin.