Impact of maturity on producible shale oil volumes in the Silurian (Llandovery) hot shales of the northern Arabian plate, southeastern Turkey

Abstract

The Silurian (Llandovery) hot shales in southeastern Turkey have excellent source rock potential, with an average total organic carbon (TOC) of 5.9 wt. % and generation potential values of 14.9 mg HC/g TOC. The hot shales contain type II organic matter and demonstrate oil and secondary gas generation potential. Hydrogen indices range from 36 to 510 mg HC/g TOC, depending on maturity. The hot shales in the Gulf Kevan 1 and Turkish Petroleum (TP) Dogan 1 wells are immature-early mature with a vitrinite reflectance equivalent (R-equ) of 0.58%-0.76%. The hot shales in the TP Soguktepe 1 and TP K. Migo 2 wells are mature and in the oil window at 0.78%-0.92% R-equ. The hot shales are interpreted to be in the wet gas-condensate maturity window with 1.08%-1.30% R-equ in the TP G. Hazro 2 and TP-Arco Abdulaziz 1 wells. Corrected (evaporation loss restored using oil API gravity values) oil saturation index values (OSIc) within the Gulf Kevan 1, TP Dogan 1, and TP-Arco Abdulaziz 1 wells are less than 100 mg HC/g TOC, which indicates that unconventional commercial oil production is not probable. The OSIc values of the mature hot shales at the TP Soguktepe 1, TP K. Migo 2, and TP G. Hazro 2 wells all exceed 100 mg HC/g TOC, indicating potentially producible oil and wet gas condensate. Thus, producible oil and wet gas condensate in the hot shale play appear present in areas that have been assessed as having between 0.8% and 1.1% R-equ.