Oil and gas fields—transfer zone relationships, Thrace basin, NW Turkey

Abstract

In the Thrace basin, oil and gas are produced from carbonate and sandstone reservoirs of Eocene and Oligocene age. Detailed geological and geophysical studies reveal that earlier and Eocene structures were influenced by basement paleotopography resulting from late Cretaceous movements between the Arabian and Anatolian plates while latest Miocene structures were generated by splays of the North Anatolian Fault in the Thrace basin. The Eocene structures, which contain the Hamitabat gas and Deveçatagì and K. Osmancìk oil fields, trend in a NE-SW direction. However, Miocene structures which are gas producers in the Karacaoglan and Umurca fields, are oriented in a NW-SE direction, parallel to the strike of the main faults which accommodate the transfer zones in the Thrace basin. The transfer zones occur between faults that dip in opposite directions (conjugate) and in the same directions (synthetic). The formation of reservoir zones, improvement of reservoir characteristics and generation of oil and gas in the oil window zone were influenced by the timing of faulting and appearance of the transfer zones in the Thrace basin.