KARSTIC RESERVOIRS OF THE MID‐CRETACEOUS MARDIN GROUP, SE TURKEY: Tectonic and Eustatic Controls on their Genesis, Distribution and Preservation

Abstract

The mid‐Cretaceous Mardin Group is the main producing reservoir interval in the oilfields of SE Turkey. During the mid‐Cretaceous, deposition of lime mudstones and bioclastic limestones took place on a carbonate platform. Repeated tectonic uplift occurred locally throughout this time, during the early stages of the closure of the southern Neotethys. The interplay of eustatic transgressions and regressions with local tectonic uplift controlled deposition and diagenesis, the latter including major secondary porosity development during dolomitization and karstification. Minor shortening and uplift in the Late Cretaceous and Palaeogene created structural traps and may also have enhanced fracture porosity. Major thin‐skinned thrust tectonics breached many reservoirs in the late Miocene. Surface anticlines which formed during the Miocene have attracted most of the exploration drilling to date, but may be the sites of the most intense breaching of the reservoirs. The distribution of the best potential reservoirs is not necessarily linked to the positions of Miocene anticlines.