Gas Accumulations in Shallow-depth Sarmatian Reservoirs from Moldavian Platform (Romania)

The studied area is located in the NW of Moldavian Platform, the oldest platform unit of the Romanian territory, representing the western margin of the East European Platform. The integrated analysis and correlation of seismic reflection surveys and wireline logs, together with mud logging and additional geological data, allow a better delineation and characterization of the Sarmatian (Middle-Late Miocene) gas reservoirs from this area. A gradually decreasing reservoir quality and, most likely, hydrocarbon potential from NW towards SE is suggested, related to sedimentary facies changes. Thermal maturation models indicate that two hydrocarbon systems are present in the Moldavian Platform: a thermogenic hydrocarbon system of Paleozoic age and a biogenic hydrocarbon system of Miocene age. This analysis is focused on the biogenic hydrocarbon system of Miocene age, which contains significant gas fields. The gas is represented by more than 98% methane and is reservoired especially in the lower part of the Sarmatian deposits, where suitable conditions for accumulation and sealing are encountered. The hydrocarbon entrapment is in structural traps of faulted monocline type and in sands / sandstones that pinch-out forming lithostratigraphic traps.