The Importance of Multi-Scale Petroleum System Assessment for Plays and Prospects De-Risking in the Eastern Mediterranean Basin

Abstract

Identifying the potential geological risks before drilling leads and prospects is a common practice for E&P operator companies. Traps and reservoir quality often receive the main attention during risk assessment. However, in the Eastern Mediterranean the biogenic gas sources generation, the synchrony between trap formation and hydrocarbon charge, and more important, the hydrocarbon preservation related to the large-scale hydrodynamics of the basin, are less analyzed or understood. A key element in the Eastern Mediterranean mega basin is the assessment of the biogenic gas potential, both in term of generation but also of preservation in the geological system. The effectiveness of biogenic gas systems is mainly controlled by the past thermal gradients and sedimentation rates. Contrarily to conventional source rocks, significant rock volumes with low organic matter content are likely involved in the biogenic gas generation process. In the deepest parts of the basin, Tertiary biogenic gas source rocks are now undergoing catagenesis. Another key element is the fluid flow history from the core of the Eastern Mediterranean basin toward its margins (including Eratosthenes Sea Mount). The hydrodynamics is first induced by high sedimentation rates and sediments compaction within the Nile Delta and the Levant Basin during the Oligo-Miocene and Plio-Pleistocene. During the Messinian Crisis short term 1400m sea level drop followed by massive impervious evaporite deposition plays a very important role in the evolution of fluid flow orientation, pressure gradients and hydrocarbon migration and dis-migration. The fluid flow is also controlled by the presence of a relatively well-connected pressure unit in Oligo-Miocene sands throughout the Levant Basin. Active hydrodynamism and buoyancy of biogenic gas are the main factors controlling the hydrocarbon migration mechanisms. A lateral long distance up-dip fill-and-spill migration is observed. Therefore, a more complete understanding of the petroleum system behavior is achieved by recognizing the origin of the geochemical and physical phenomena occurring in the subsurface, in a regional or semi-regional basin scale. It will allow to recognize the hydrocarbon generation and the pore pressure and fluid flow regime patterns, which are not caught at limited prospect scale. Basin modeling techniques offer the possibility to estimate the heating rates of sedimentary basins, the timing and quantities of generation of biogenic or thermogenic hydrocarbons and, finally the pore pressure-effective stress regimes responsible, in part, for the hydrocarbon migration and effective charge.

AAPG Datapages/Search and Discovery Article #90355 © 2019 AAPG Africa Region, The Eastern Mediterranean Mega-Basin: New Data, New Ideas and New Opportunities, Alexandra, Egypt, September 6-7, 2019