Petrophysical characteristics and fluid flow in the Derdere formation around Beşikli - Tokaris fields, SE Turkey

Tandırcıoğlu, Ahmet
The study area is located in southeast Turkey, mainly in the Petroleum Districts XI and XII. Major oil fields in the area produce oil from the Upper Cretaceous Derdere Formation, one of the most extensive and well-developed reservoir formations in southeast Turkey. In this study, petrophysical characteristics and the formation water flow in the Derdere Formation are determined using the data from well logs, core analyses, well tests and chemical analyses of the formation water. In addition, an attempt is made to explain the reasons of unexpected absence of oil in the exploration wells drilled to the north and northeast of the producing oil fields Tokaris, İkizce, Beşikli, and Doğu Beşikli. Three major lithofacies in the Derdere Formation are recognized from well log data. The best distinction of the lithofacies is observed on the density- neutron crossplot. Lithofacies- 1, found at the lower part of the Derdere Formation, shows the characteristics of a good source and seal rock. Petrophysical characteristics indicate that Lithofacies-2, composed of indolomites, is the best reservoir rock and can be considered as a continuous flow unit. Lithofacies-3 consists of bioclastic limestones with high porosities; however, permeabilities in this lithofacies are low due to the vuggy/moldic nature of the porosity type. The flow direction of the Derdere formation waters is mainly from east towards west and southwest. Total dissolved solid, sodium chloride, chloride, sodium and calcium concentrations of the Derdere Formation waters increase along the flow path towards west. On the other hand, bicarbonate concentrations show a general decrease towards west. Moreover, HC03-Na type water with negative index of base exchange values is found in the eastern part, indicating active hydrodynamic conditions and effects of meteoric water, whereas Cl-Ca type water indicating isolation from the effects of the meteoric water and hydrostatic conditions, is found in the Derdere formation waters of the oil fields located in the west. Consequently, the absence of oil in the eastern part of the study area can be a result of the active hydrodynamic groundwater percolation within the Derdere Formation towards west and southwest, where the oil fields are present.
Citation Formats
A. Tandırcıoğlu, “Petrophysical characteristics and fluid flow in the Derdere formation around Beşikli - Tokaris fields, SE Turkey,” Ph.D. - Doctoral Program, Middle East Technical University, 2002.