Rock-Fabric/Petrophysical Classification of Carbonate Pore Space for Reservoir Characterization

The goal of reservoir characterization is to describe the spatial distribution of petrophysical parameters such as porosity, permeability, and saturation. Wireline logs, core analyses, production data, pressure buildups, and tracer tests provide quantitative measurements of petrophysical parameters in the vicinity of the wellbore. These wellbore data must be integrated with a geologic model to display the petrophysical properties in three-dimensional space. Studies that relate rock fabric to pore-size distribution, and thus to petrophysical properties, are key to quantification of geologic models in numerical terms for input into computer simulators.

Geologic models are generally based on observations that are interpreted in terms of depositional environments and sequences. In the subsurface, cores and wireline logs are the main source of data for these interpretations. Engineering models are based on wireline log calculations and average rock properties from core analyses. Numerical engineering data and interpretive geologic data are joined at the rock fabric level because the pore structure is fundamental to petrophysical properties, and the pore structure is the result of spatially distributed depositional and diagenetic processes.

The purpose of this report is to (1) describe the relationship between carbonate rock fabrics and petrophysical properties, (2) suggest a generic petrophysical classification of carbonate pore space, and (3) determine the important geologic parameters to be mapped to allow accurate quantification of carbonate geologic models.