Source rocks and hydrocarbon generation in Slovenia (Mura Depression, Pannonian Basin)

Abstract

Source rock analysis (organic carbon, Rock-Eval, gas chromatography, vitrinite reflectance) and numeric modelling techniques have been applied to evaluate the hydrocarbon potential and the timing of hydrocarbon generation in northeastern Slovenia (Mura Depression, Pannonian Basin). Source rocks of Mesozoic age were not detected. Most Tertiary samples are gas prone. Oil-prone sediments occur mainly in Egerian/Eggenburgian, Karpatian and Sarmatian levels. The maturity pattern reflects complex Neogene subsidence and thermal histories. So the thickness of the oil window varies from about 300 m (Maribor–Somat area) to 1500 m (Ljutomer Depression). The top of the oil window lies below a depth of 2500 m in the Ljutomer Depression whereas it reaches the surface in the Maribor area. Three main hydrocarbon generation phases are distinguished in different parts of the Mura Depression: (a) a Karpatian/Badenian stage due to extremely elevated heat-flow (Maribor–Somat–Radkersburg area, Boc Anticline, probably Ormoz–Selnica Anticline); (b) a middle/late Miocene to early Pliocene stage due to Miocene deep burial (Ormoz–Selnica Anticline); (c) a late Miocene to present generation stage (Ljutomer Depression, eastern margin of the Murska–Sobota High).