Source-Rock Hydrocarbon Potential of the Middle Triassic—Lower Jurassic Cudi Group Units, Eastern Southeast Turkey

Abstract

The southern part of Southeast Turkey constitutes the northern margin of the Arabian plate. The region contains rock units ranging in age from Paleozoic to Mesozoic. The source-rock potential of the Middle Triassic-Lower Jurassic Cudi Group in the eastern part of Southeast Turkey was investigated. Samples were obtained from six wells (çilesiz-1, B. Yolaçan-1, G. Dinçer-1, çamurlu-101, çamurlu-102, and Yolaçan-3). The source-rock potential of these units was evaluated by organicgeochemical and petrographic analyses. Sediments have an average of 0.15% total organic carbon (TOC). Commonly, TOC is higher in carbonate-rich facies than in evaporitic deposits. TOC analyses of the Cudi Group shows that these formations are poor to moderate in organic matter. The S1 (average 0.25 mgHC/gTOC), S2 (0.40 mgHC/gTOC), hydrogen index (HI) (average 235 mgHC/gTOC), oxygen index (OI) (average 231 mgCO2/gTOC), and Tmax (average 422°C) values from the Rock-Eval pyrolysis indicate that the dominant organic matter consists of types II and III kerogen, which have gas generative potential. Production index (PI) values indicate samples containing secondarily migrated hydrocarbons. Optical investigation demonstrates that the organic matter is mainly amorphous (70-90%) and of marine origin, but includes small amounts of terrigenous organic matter (10-30%). Results suggest that these beds probably do not constitute a source of liquid hydrocarbons but may represent a source of gas.