Oligocene Osmancik formation, upper Eocene-lower Oligocene Mezardere formation, and Eocene Hamitabat, Sogucak, and Ceylan formations encountered in the Habiller-2 and Havsa-1 wells drilled in the Thrace basin are composed of shale, limestone, tuff, and sandstone. On the basis of organic geochemical and organic facies observations, organic components of the Oligocene Osmancik formation, upper Eocene-lower Oligocene Mezardere formation, and Eocene Hamitabat, Sogucak, and Ceylan formations are generally herbaceous, algae/amorphous material (Type It and Type III kerogens). In the Habiller-2 well, organic material contents of Oligocene Osmancik formation, upper Eocene-lower Oligocene Mezardere formation, and Eocene Hamitabat, Sogucak, and Ceylan formations are between 0.02 and 1.38 wt% and that of the upper Eocene-lower Oligocene Mezardere formation in the Havza-1 well ranges from 0.31 to 1.06 wt%. On the basis of these values, Eocene-Oligocene units in both wells show weak to good source rock potentials. According to T-max, vitrinite reflection and Spore Color Index evaluations, Eocene-Oligocene units in the Habiller-2 and Havsa-1 wells are at immature and mature oil zones.