International Geologiical Congress - Oslo 2008


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GEP-19 Carbonate reservoirs and plays


Reservoir characterisation and facies modelling of heterogeneous fractured carbonate reservoirs in the Middle East


Petter Soerhaug, StatoilHydro (Islamic Republic of Iran)
Ian Sharp, StatoilHydro (Norway)
Jean-Christophe Embry, StatoilHydro (Norway)
David Hunt, StatoilHydro (Norway)
Jan C. Rivenas, StatoilHydro (Norway)
Thomas Sperre, StatoilHydro (Brazil)
Stian Soltvedt, StatoilHydro (Norway)
Cecilie Otterlei, StatoilHydro (Norway)


Reservoir characterisation and modelling of low porosity/permeability fracture controlled carbonate reservoirs in the Middle East represents a major challenge to the Exploration + Production. In this contribution we demonstrate that whilst accurate description and implementation of a good fracture model is key to understanding flow behaviour, facies (matrix) modelling also plays a significant role. This is especially so in the presence of secondary dolomite geobodies.
Regional fieldwork and limited core data have highlighted a hierarchy of heterogeneity, which we have divided into i) depositional heterogeneity, ii) diagenetic heterogeneity and iii) fracture heterogeneity.
Depositional heterogeneity is captured by bio-facies modelling of facies belts, in this case represented by a strongly progradational rudistic carbonate shelf. The biofacies, (basin-slope, shelf margin grainstone, lagoonal-platform top wackestones and lagoonal-platform top tidal shoals) are over printed by litho facies consisting of mainly chalky limestone, dolomitic limestone and dolomite, which represent diagenetic facies.
A major source of heterogeneity in the studied example is hydrothermal dolomite plumes. These are represented in the model as plug dolomite formed along fault/fracture zones, and strata bound dolomites which typically "migrate out" from the fault zones following "higher-permeability" zones or beneath aquitards. Chalky (microporous) facies are interpreted to be connected to the dolomite plumes and form a halo around the dolomite objects. Different chalky facies are also modelled for each biofacies to capture the differences in petrophysical properties inherited from the.biofacies.
This poster focuses on the workflow in building such a facies model and on the importance of a facies model for defining fluid flow.


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