Organic geochemical and petrographic characteristics of the Miocene Salif organic-rich shales in the Tihama Basin, Red Sea of Yemen: Implications for paleoenvironmental conditions and oil-generation potential

• The Miocene Salif shale rocks have rich-organic matter with high total organic carbon (TOC) content.
• The kerogen is characterized by predominantly Type II kerogen and mixed Type II–III with Type III kerogen.
• The Salif organic-rich shales have very good oil-generative potential.

This study is the first investigation which provides information regarding the organic geochemical and petrographic characteristics of Miocene Salif organic-rich shales from Tihama Basin in the Red Sea, Yemen. We evaluate organic matter content, type, maturity, and oil-generation potential as well as depositional environmental conditions. The total organic carbon (TOC) contents of the Miocene Salif shales vary between 0.59% and 5.40%, indicating fair to very good source rock potential. The Salif shales have hydrogen index values in the range of 64–576 mg HC/g TOC. The organic matter in the Salif shales are dominated by Type II kerogen and mixed II–III kerogens with a minor contribution of Type III kerogen, as supported by kerogen microscopy. This is also confirmed by their biomarker and carbon isotope results, which indicate that the Salif shales were deposited in highly reducing marine conditions and received high contributions of aquatic organic matter (e.g., algal and microbial) and terrigenous organic matter. Consequently, the Salif Formation is likely to be an oil-source rock. Maturity indicators such as vitrinite reflectance and pyrolysis data (i.e., Tmax and PI) indicate that most of the Salif shale samples are generally thermally mature, at the early-mature to peak oil window stage. The new data presented in this paper suggest that early-mature oil has been generated from Miocene Salif organic-rich shales, so exploration strategies should focus on the known location of Miocene Salif organic-rich shales for predicting the location of the source kitchen.