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Abstract: The Role of Outcrop Data in Performance Prediction of Non-Fractured Carbonate Fields

Charles Kerans, F. Jerry Lucia, F. Wang

Quantification of facies architecture for use in modeling of carbonate reservoirs requires delineation of petrophysically significant facies in 3D space, assessment of the degree of petrophysical heterogeneity within a facies, and integration of geostatistical tools for retailing this architecture during scale-up for flow modeling.

An overwhelming amount of data from core description and interpretation of wireline logs from carbonate fields demonstrates that depositional facies and petrophysical properties vary vertically in the range of cm to a few meters. A vertically cyclical stratification of both depositional and petrophysical properties in the range of 1-10 m can also be demonstrated through geostatistical analysis, reflecting a fundamental control by Milankovich or another external high- frequency forcing function. The fundamental unknown in reservoir characterization is lateral continuity.

Outcrops remain the only practical source of data on lateral variations of facies/petrophysical architecture. Two approaches to the analysis of reservoir architecture in outcrop are (1) geologic mapping followed by dense grid mapping of porosity/permeability structure, resulting in pixel-based geostatistical renditions of permeability, and (2) statistical analysis of depositional or rock- fabric-facies objects followed by grid and horizontal traverse mapping within objects for assessment of intra-object heterogeneity, resulting in bouillon-type object-oriented images. Ultimately, bouillon-based images will be superior for performance prediction because they maximize geologic information in rendering the 3D image of reservoir architecture. Currently data on carbonate facies objects is parse, and continued outcrop work will be essential. Data sets discussed include the Permian of west Texas and Cretaceous of southwest Texas.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France