Structural Geology and Depositional Environments of the Mardin Group Carbonates in the Cemberlitas Oil Field in Southeastern Anatolia, Turkey

Mulayim, Oguz; Cemen, Ibrahim

The frontal belt of the southeastern Anatolia fold-thrust belt in Turkey contains several small to mid size oil fields, producing from the Cretaceous Mardin Group carbonates. Most of the oil fields are located along the east-west to southwest to northeast trending, narrow and asymetrical anticlinal structures which are associated with contractional faulting in the area. Cemberlitas oil field in Adiyaman, Turkey is one of the most important oil field in the region. This study is aimed at determining the nature of hyrocarbon trapping mechanism and depositional environments of the Cretaceous Mardin Group carbonate rocks in the Cemberlitas oil field based on our interpretation of available well logs and 2-D reflection profiles. Data from 54 exploration and production wells were also used to determine a sequence stratigraphic framework for the Mardin Group to identify transgressive-regressive (T-R) sequences and diagenetic attributes of the group, especially dolomitization.

The Late Cretaceous (Aptian-Lower Campanian) Mardin Group is deposited on the shelf-to intrashelf part of a passive continental margin of the Arabian plate which collided with the Anatolian plate during Miocene as a result of continuning compressional tectonics since Cretaceous. The Miocene collision resulted in closure of the southern branch of Neothetis and gave way to Miocene indentation tectonics and associated strike-slip faulting in southeastern Anatolia, Turkey.

The Derdere and Karababa Formations of the Mardin Group are the main reservoirs in the Cemberlitas oil field. They were deposited during secular transgression and regression during the Aptian to Lower Campanian time and show variable thicknesses within the oil field. The Mardin Group carbonates in the Derdere and Karababa Formations have undergone both early and late diagenesis resulting from the existence of shallowing-upward depositional cycles and burial- tectonic stresses during the Late Cretaceous. Fracturing and dolomitization are important effects on reservoir quality in the Cemberlitas oil field. The reservoir quality, on the field scale, is better at the structurally high intervals due to increased frequency and intesity of fractures and intensified late dolomitization, providing necessary porosity and permeablity for oil production.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013