Methanogenesis in a Continuous Hydrocarbon Generation Process for 3D Migration Basin Model – Eastern Mediterranean Offshore

Active exploration in Eastern Mediterranean offshore has led to important hydrocarbon discoveries over the last decades in several petroleum plays such as Post-Messinian clastics in the Nile Delta, Oligo-Miocene turbiditic sandstones or Mesozoic shallow-water carbonates in the deep offshore.

The main objective of this study is to provide an understanding of pressure and thermal evolution in response to dramatic events such as the Messinian Salinity Crisis, but also an assessment of source rock contribution to each petroleum systems.

Play assessment in that area implies to take into account biogenic gas generation and preservation in the system from Cenozoic sources. Achieving this requires to establish a dedicated workflow in the frame of available basin model capabilities to reflect microbial activity as a kinetic reaction without exaggerating the amount of gas generated.

In the context of thick Nile Delta sequences, the burial reached by Cenozoic source rocks is sufficient to start more classical thermogenic reactions. Then biogenic gas generation kinetics must be coupled with classical kinetics. It leads to the definition of 8 distinct kerogens depending on mixtures between Type II and III, and biogenic efficiency. This geochemical model is used in 3D migration simulations, showing that rapid pressure changes caused by the Messinian Salinity Crisis have a major impact on hydrocarbon accumulations (possible flushing, reorganization of migration pathways) whereas deeper, but more speculative thermogenic petroleum systems are less affected.