Saramet, Mihai¹, Gheorghe Gavrilescu¹, Constantin Cranganu² 
(1) "Al. I. Cuza" University, Faculty of Geography-Geology, Iasi, Romania 
(2) Brooklyn College of the City University of New York, Brooklyn, NY

ABSTRACT: The Role of Oligocene Formations in Hydrocarbon Generation and Accumulation in the Histria Petroleum System of the Romanian Shelf of the Black Sea

The western basin of the Black Sea started to form during Upper Aptian – Albian period as an intracontinental rift basin. This basin was produced by a relief inversion due to a hinge movement of an emerged median massif, situated in the present Black Sea basin. The opening of the intracontinental rift was accompanied by a translation of different crustal blocks along several transcurrent faults acting at the edge of the European continental landmass. The movement of continental blocks along these faults induced an alternation of trantensive and transpresive regimes that reflected in evolution of both sedimentary and subsidence rates, as well as in initiation of tectonic inversions. The Histria depression formed during Upper Aptian – Albian time as a continuation of the emerged part of the North Dobrogea orogen. During the transpresive period, which started in Oligocene, a very rapid subsidence and tectonic inversions took place. Consequently, the sedimentation rate exceeded the subsidence rate, and the basin filled up with sediments. The Histria petroleum system consists of two sub-systems: 1) a hydrocarbon generation-expulsion sub-system, defined by Oligocene source rocks, and 2) a migration-accumulation sub-system formed by trap and reservoir rocks of Albian, Upper Cretaceous, and Eocene age. Seismic and well log studies revealed the dual character of Oligocene rocks: a) they are the source rocks for the Histria petroleum system; b) by incorporating and distributing overpressures inside them, they contributed to both downward movement of fluids from the source rocks and sealing of reservoirs in adjacent rocks.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.