Mineralogical, geochemical and kinetic characteristics of the Shiranish formation of the Euphrates graben (Syria) and assessment of its oil source potential

The Shiranish formation within the central Euphrates graben consists of thick successions of argillites and wackestones enriched in organic carbon. Comprehensive mineralogical, geochemical, and kinetic investigations made it possible to specify the stratigraphic subdivision and to identify the factors controlling the generative potential of these rocks. Based on variations in hydrogen (HI) and oxygen (OI) indices, total organic carbon (TOC) content, and activation energy distributions, the Shiranish formation was divided into lower (LSF) and upper (USF) formations, with the upper member further subdivided into two intervals (USF-1 and USF-2). The USF exhibits higher oil-generating potential (TOC up to 4 %, HI up to 500 mg HC/g TOC) with relatively narrow activation energy distributions, whereas the LSF is characterized by broader activation energy spectra and predominantly gas-generating potential. Mineralogical features, including the presence of ankerite and pyrite, indicate the influence of clay-rich material and significant methanogenesis during early diagenesis. Kinetic modeling revealed differences in predicted maturity temperatures: 136 °C for the USF and 144 °C for the LSF, reflecting facies variations and heterogeneity of the organic matter. These findings provide new insights into the petroleum source rock potential of the Shiranish formation and highlight prospective intervals for future hydrocarbon exploration in the central Euphrates graben.

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