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Understanding of the Petroleum System(s) of the Western Black Sea: Insights from 3-D Basin Modeling

Abstract

Several hydrocarbon accumulations have been found in the Western Black Sea Basin (WBSB) to date, proving the presence of both thermogenic and biogenic petroleum systems. Whereas most accumulations are located on the present day shelf the recent Domino-1gas discovery was drilled in the deep-water of the Romanian Black Sea. The presence of oleanane biomarker in all oil fields on the Romanian shelf proves the existence of a Tertiary thermogenic petroleum system likely sourced by the Latest Eocene(?) to Miocene black shales (Maykop succession). In addition, older source rocks may be locally present in different parts of the basin. The relative contribution of these different source rock intervals to the petroleum system and the hydrocarbon migration itself in time and space are poorly understood. In this study, we performed 3D basin and petroleum system modeling to evaluate the charge model of the WBSB focusing on the Maykop section. The model is built on the regional-scale interpretation of recently acquired long-offset 2D reflection seismic data sets and is calibrated with proprietary and publicly available well, geochemical, and temperature data. The sensitivity of the thermal models on source maturity has been tested. The basin models considered fit between two end member scenarios (a “hot” and a “cold” model). Whereas the “hot” model provides good results in the shallow water areas, the “cold” model is considered more valid for the deep-water areas of the WBSB. Hydrocarbon expulsion maps were calculated for both scenarios at various stratigraphic levels. In order to simulate the migration pathways, facies maps were constructed for key stratigraphic horizons based on well, seismic facies and outcrop data. These basin-scale facies maps were used as the input to constrain the lateral (facies properties) and the vertical (i.e. seal) migration capacity of various sedimentary units driving the migration. In our models, the preferential migration directions and drainage areas were identified and potential hydrocarbon accumulations have been outlined. The results highlight the vastly underexplored exploration potential associated with the deep Maykopian section of the WBSB.