Tectonic Controls on Sediment Input into the Northeastern Black Sea – Implications for Hydrocarbon Reservoir Quality

Siliciclastic reservoir presence and quality are key exploration risks within the Eastern Black Sea. Large-scale fluvial systems draining the crystalline East European Craton to the north had the capacity to deliver significant quantities of reservoir quality sand into the basin (and its pre-rift) during the Mesozoic and Cenozoic. This potential is exemplified by the adjacent South Caspian Basin that, during its Messinian isolation, received up to 7 km of Productive Series fluvio-lacustrine sediment, largely from the incised palaeo-Volga River system. Sandstone-prone elements of this series form the main reservoir interval within the South Caspian Basin and are estimated to contain reserves of ~7 BBOe and 1.2 trillion m3 of gas.

The northern margin of the Eastern Black Sea (unlike the South Caspian) has been the locus of long-lived active basin- and mountain-forming events. The Greater Caucasus Basin opened during Early Jurassic extension to transtension and formed an intermediate sediment sink for southerly-draining sediment transport systems during much of the Jurassic to Eocene. This was subsequently inverted from the Late Eocene-Oligocene onward during the evolution of the Greater Caucasus mountain belt. As well as forming a barrier to northerly-derived systems, this range also formed a source of more locally-derived sediment of variable reservoir quality. These factors are likely to limit the amount of East European Craton-derived reservoir quality sandstones within the Eastern Black Sea, although detailed facies mapping and provenance analysis have identified the presence of other, more localised, quartz-rich sediment sources that may have contributed sediment to the basin.