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<p>Lacustrine source rocks are key contributors to global hydrocarbon deposits. However, their distribution is often irregular and confined to specific stratigraphic horizons. Therefore, a comprehensive geochemical analysis is required to determine their stratigraphic position and lateral extent in relation to the surrounding carrier beds. In this study, a geochemical analysis of core and outcrop samples was conducted to assess the organic matter content, types, and quality, as well as to reconstruct the thermal evolution and prevailing paleoredox conditions within the Cenozoic sediments of the Eyasi-Wembere Basin, Tanzania. The results reveal significant variation in the organic matter content, types, and quality, both vertically and laterally. Total Organic Carbon (TOC) values range from 0.16 to 1.88 wt%, with an average of 0.62 wt%. The S2 and Hydrogen Index (HI) also exhibit notable fluctuations, with S2 values ranging from 0.16 to 7.15&#xa0;mg HC/g (average: 1.56&#xa0;mg HC/g) and HI values ranging from 18 to 420&#xa0;mg HC/g TOC (average: 18&#xa0;mg HC/g TOC). The organic matter is composed of kerogen types II, II/III, III, and IV, each exhibiting varying degrees of thermal maturation, ranging from immature to mature. The evaluated source rock intervals demonstrate potential from poor to good, with only a limited number of intervals exhibiting high-quality organic matter, primarily located in the deeper sections. Variations in source rock quality were influenced by fluctuations in paleoredox conditions, sediment influx, subsidence rates, and climate, as reflected in the changes in elemental data. This study offers valuable insights into the spatial distribution of source rocks within the East African Rift, demonstrating that they are confined to specific stratigraphic intervals. The findings are crucial for identifying regions with the highest potential for oil generation.</p>

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Geochemical evaluation of the Cenozoic hydrocarbon source rocks in the Eyasi Wembere Basin, Northeast Tanzania

  • 期刊论文

  • 发表日期：

    2025年6月17日

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  • John William Gama,
  • Emily Barnabas Kiswaka,
  • Venance Emmanuel Mboya,
  • Habibu Luumi Mamboli Mohamed

摘要

Lacustrine source rocks are key contributors to global hydrocarbon deposits. However, their distribution is often irregular and confined to specific stratigraphic horizons. Therefore, a comprehensive geochemical analysis is required to determine their stratigraphic position and lateral extent in relation to the surrounding carrier beds. In this study, a geochemical analysis of core and outcrop samples was conducted to assess the organic matter content, types, and quality, as well as to reconstruct the thermal evolution and prevailing paleoredox conditions within the Cenozoic sediments of the Eyasi-Wembere Basin, Tanzania. The results reveal significant variation in the organic matter content, types, and quality, both vertically and laterally. Total Organic Carbon (TOC) values range from 0.16 to 1.88 wt%, with an average of 0.62 wt%. The S2 and Hydrogen Index (HI) also exhibit notable fluctuations, with S2 values ranging from 0.16 to 7.15 mg HC/g (average: 1.56 mg HC/g) and HI values ranging from 18 to 420 mg HC/g TOC (average: 18 mg HC/g TOC). The organic matter is composed of kerogen types II, II/III, III, and IV, each exhibiting varying degrees of thermal maturation, ranging from immature to mature. The evaluated source rock intervals demonstrate potential from poor to good, with only a limited number of intervals exhibiting high-quality organic matter, primarily located in the deeper sections. Variations in source rock quality were influenced by fluctuations in paleoredox conditions, sediment influx, subsidence rates, and climate, as reflected in the changes in elemental data. This study offers valuable insights into the spatial distribution of source rocks within the East African Rift, demonstrating that they are confined to specific stratigraphic intervals. The findings are crucial for identifying regions with the highest potential for oil generation.