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<p>This study integrates organic and inorganic geochemical analyses to evaluate the hydrocarbon generative potential of Upper Jurassic-Lower Cretaceous (UJLC) sediments in the Senegalo-Mauritanian (SM) Basin. Representative limestone and shale have been characterized using Rock-Eval pyrolysis and LECO, as well as Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The Total Organic Carbon (TOC) values of Jurassic, Neocomian, Aptian, and Albian sediments range, respectively, between 0.11 and 0.438 wt%; 0.10 and 0.76 wt%; 0.12 and 0.86 wt%; and 0.2 and 2.43 wt%. Based on the HI values, the UJLC samples of the SM Basin suggest a higher terrigenous contribution, indicating type III kerogen. However, 15.38% of the Albian samples and 33% of Neocomian samples show the presence of type II/type I kerogen. Cross plots of Hydrogen Index (HI) versus Tmax show that the majority of Albian samples are within the mature zone with the potential to generate oil and little gas. The Aptian sediments are present in equal proportion between immature and mature zones, while Neocomian and Jurassic sediments are partly within the immature zone. Additionally, the calculated Vitrinite Reflectance (Ro) values indicate that the majority of Jurassic and Neocomian samples are immature, whereas Albian and Aptian samples have Ro values exceeding 0.6% or even 0.8%. The Production Index (PI) observed in the samples increased with lithology and depth with high value in limestones of the Neocomian and Upper Jurassic sequence. Compared to the Jurassic and Neocomian samples, Albian and Aptian samples present fair hydrocarbon generative potential. The Low HC generative potential of the UJLC sequence may be related to the moderate-to-low primary productivity observed from Ba/Al, Cu/Al, and Ni/Al proxies, or to the oxic environment of deposition, which does not favor organic matter preservation. Incorporating organic matter proxies into source rock evaluation is highly beneficial to the assessment of the petroleum potential of the studied basin. It reduces exploration uncertainty and provides guidance for future resource development in this underexplored margin.</p>

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Integrated organic and inorganic geochemistry for assessing the hydrocarbon potential of Upper Jurassic-Lower Cretaceous sediments in the Senegalo-Mauritanian Basin, West Africa

  • 期刊论文

  • 发表日期：

    2025年11月19日

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  • Ndeye Khady Ndiaye,
  • Matthew Essien Nton,
  • Cheikh Abdoul Kader Fofana,
  • Thierno Seydou Ly,
  • Arsene Frederic Boissy,
  • Godfrey Peter Mweemba

摘要

This study integrates organic and inorganic geochemical analyses to evaluate the hydrocarbon generative potential of Upper Jurassic-Lower Cretaceous (UJLC) sediments in the Senegalo-Mauritanian (SM) Basin. Representative limestone and shale have been characterized using Rock-Eval pyrolysis and LECO, as well as Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The Total Organic Carbon (TOC) values of Jurassic, Neocomian, Aptian, and Albian sediments range, respectively, between 0.11 and 0.438 wt%; 0.10 and 0.76 wt%; 0.12 and 0.86 wt%; and 0.2 and 2.43 wt%. Based on the HI values, the UJLC samples of the SM Basin suggest a higher terrigenous contribution, indicating type III kerogen. However, 15.38% of the Albian samples and 33% of Neocomian samples show the presence of type II/type I kerogen. Cross plots of Hydrogen Index (HI) versus Tmax show that the majority of Albian samples are within the mature zone with the potential to generate oil and little gas. The Aptian sediments are present in equal proportion between immature and mature zones, while Neocomian and Jurassic sediments are partly within the immature zone. Additionally, the calculated Vitrinite Reflectance (Ro) values indicate that the majority of Jurassic and Neocomian samples are immature, whereas Albian and Aptian samples have Ro values exceeding 0.6% or even 0.8%. The Production Index (PI) observed in the samples increased with lithology and depth with high value in limestones of the Neocomian and Upper Jurassic sequence. Compared to the Jurassic and Neocomian samples, Albian and Aptian samples present fair hydrocarbon generative potential. The Low HC generative potential of the UJLC sequence may be related to the moderate-to-low primary productivity observed from Ba/Al, Cu/Al, and Ni/Al proxies, or to the oxic environment of deposition, which does not favor organic matter preservation. Incorporating organic matter proxies into source rock evaluation is highly beneficial to the assessment of the petroleum potential of the studied basin. It reduces exploration uncertainty and provides guidance for future resource development in this underexplored margin.