Modeling of Microbial Gas Generation: Application to the Eastern
Mediterranean “Biogenic Play”
Published in Geologica Acta, www.geologica-acta.com
F. SCHNEIDER , M. DUBILLE, L. MONTADERT
(1) Beicip-Franlab, 232 Avenue Napoléon Bonaparte, 92500 Rueil-Malmaison, France.
Biogenic gas is becoming increasingly important as an exploration target in the
petroleum industry because it occurs in geologically predictable circumstances and
in large quantities at shallow depths as free gas or gas hydrates. As accumulations
of biogenic gas result in a subtle synchronization between early generation and
early trapping, we integrated a macroscopic model of microbial gas generation
within a 3D basin and petroleum system forward simulator.
The macroscopic model is based on a microscopic model, which consists in a 1D
sedimentary column that accounts for sedimentation, compaction, Darcy flow and
Diffusion flow. The organic carbon is the only non-soluble element considered in
this version of the model. The dissolved elements are O2, SO4
2-, H2, CH3COOH,
and CH4. Methane is dissolved in water or present as a free phase if its
concentration exceeds its solubility at given pressure and temperature. In this
microscopic model, the transformation of substrate into biomass is described
through a set of logistic equations coupled with the transport equations (advection
Based on the microscopic considerations we developed the macroscopic model of
low maturity / biogenic gas generation in which hydrocarbons are generated
through first order kinetic reactions at low maturity. This macroscopic model is
adapted to petroleum system modeling at basin scale with TemisFlow®, which
aims to understand and predict hydrocarbon generation, migration, and
accumulation. It is composed of: 1) A source rock criteria which allow defining the
biogenic gas source rocks potential, and 2) A kinetic model of methane generation.
The previous model has been successfully applied on different basins such as the
Carupano Basin from the offshore Venezuela, the Magdalena Delta (offshore
Colombia) and the offshore Vietnam where direct observations of low-maturity gas
were available. Furthermore, it has been applied in the offshore Lebanon in order
to check the viability of a biogenic gas system.
Keywords: Biogenic Gas, Basin Model, Petroleum System, Eastern Mediterranean