Organic Geochemical Evaluation of Middle-Late Eocene Hamitabat and Celaliye Shales in the Kırklareli Area, Northwest of the Thrace Basin, Turkey

ABSTRACT This study was carried out on the Middle-Late Eocene dark gray-black colored organically rich shales of the Celaliye and Hamitabat formations, Northwest of the Thrace Basin. The shale core samples were collected from sixteen wells from the Kırklareli area in the northwest of the Thrace Basin and were evaluated by subjecting them to organic geochemical analyses (Total organic carbon -TOC (weight percentage - wt%), Rock-Eval -RE, and Vitrinite Reflection - Ro%)). Generally, in terms of TOC values, the Celaliye and Hamitabat formations shales show fair-good-very good source rock characteristics. Celaliye and Hamitabat formations shales are suitable for hydrocarbon production when Tmax (maximum pyrolysis yield temperature) is above 430o C. According to Tmax values, Celaliye Formation is mature-overmature source rock (Tmax=445–485 oC) in I-well between 3142–3240 m. The Hamitabat Formation is extremely mature with Tmax values varying between 463–514 oC in the I-well (at the depth: 3560–3678 m) and is thought to be suitable for gas generation. The high TOC values (> 1.0 %) of the Celaliye and Hamitabat formations in the I-well in the study area and the fact that their petroleum generation potentials vary between 27.90 and 36.1 mg HC/g rock indicate very good oil source rock properties. In the studied formations, Ro% values increase with the increase in depth in the wells. However, some well cuttings of the Hamitabat Formation show irregular Ro values. According to production index (PI) values, shales of both formations can produce oil. But it is more suitable for gas generation. Hydrogen index (HI) values for both formations are generally in the range of 50-200 mgHC/g TOC and are Type III kerogen and gas. Samples are between Type II and Type III kerogen in the HI-Tmax and HI-Oxygen index (OI) graphs. It is concentrated in Type III. This type of organic matter can produce gas according to RE pyrolysis.