Abstract: Controlling Parameters of Mineral Diagenesis in Reservoirs: the Contribution of Numerical Modeling

Brosse, Etienne; Le Gallo, Yann; Bazin, Brigitte and Jeffrey, S. - IFP

Mineral diagenesis of reservoirs can be governed by several parameters: some of them related to the basin-scale geological history (temperature, pressure, mechanical stress, hydrodynamism); others related to the reservoir-scale sediments (stratigraphic architecture, facies characters, mineral composition, petrophysical features). In a given geological context, only a part of these parameters really influence the diagenetic transformations that can occur. When calibrated on sufficient data, a modeling approach is able to disentangle the respective role of the various parameters involved. It can thus provide guidelines for a better understanding of the diagenetic evolution and heterogeneities.

A reaction-transport numerical model is used, Diaphore, that integrates the various coupled mechanisms acting during diagenesis, except pressure-solution. When the flow of water is the governing factor of the mineral evolution, reaction fronts can develop and cross the reservoir. But hydrocarbons filling is likely to stop these fronts. When petrographic controls are available in the oil zone of a reservoir, the model can be used to interpret the heterogeneity of the mineral proportions observed at the field scale.

Examples are presented from the Brent and Rotliegend provinces. Appropriate sensitivity tests provide a hierarchy, in the given geological context reconstructed from the various data provided by Inorganic Geochemistry, the respective role played by the water composition, by the temperature, or by the kinetics of the reactions. The modeling results can put some constrains on the velocity of the water flow responsible of the fronts, and on the epoch of oil migration.

AAPG Search and Discovery Article #90933©1998 ABGP/AAPG International Conference and Exhibition, Rio de Janeiro, Brazil