Abstract: Reservoir Quality Prediction Through Simulation of Sandstone Diagenesis: Cusiana Field, Eastern Colombia

Bonnell, L. M. - Geologica A.S.; Warren, E. A. - BP Exploration Colombia; and Lander, R. H. - Geologica A.S.

The Mirador and Barco Formations are Eocene-age reservoir units in the Cusiana Field of eastern Colombia. These sandstones are compositionally simple, consisting primarily of quartz with little feldspar or authigenic clay. Grain sizes vary from very fine grained to very coarse grained. The units have undergone a complex burial history that has led to extensive porosity loss. Porosity varies significantly but is typically less than 10%.

We used the Exemplar model to simulate compaction and quartz cementation in these sandstones using the burial history published by Cazier and others (1995). Preliminary results show a strong correlation between grain size, quartz cement abundance, and porosity. Very fine grained samples have predicted quartz cement abundances in excess of 16% and model porosities of near 0%. By contrast, very coarse grained samples have predicted quartz cement abundances of less than 4% and porosity values near 15%. The onset of significant quartz cementation is modeled to be ~15 Ma. The rate of quartz cementation has decreased over the last 5 m.y. as a result of uplift of the area associated with the deformation in the Easter Cordillera.

lntergranular volumes are significantly lower than sandstones of similar composition and texture occurring in continental, rift, and passive margin basins which may reflect a tectonic overprint. Empirically calibrated values for the kinetics of quartz cementation for Mirador and Barco Formation sandstones, however, are comparable to sandstones from other basin types.

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