Petroleum Geology of Carbonate Reservoirs

1. Introduction  What are carbonate reservoirs? Finding and developing carbonate reservoirs Sources for reservoir data Unique attributes of carbonate rocks

2. Petrological properties of carbonate reservoirs Fundamental (primary) rock properties Texture, fabric, composition, and sedimentary structures Classification schemes for carbonate rocks Dunham, Folk, Wright, and Embry and Klovan Dependent (secondary) properties Porosity Definition Measurement and classification schemes Permeability Darcy's law, definition, and method of calculation Specific, effective, and relative permeability Relationship to porosity Tertiary properties of reservoir rocks Properties measured with borehole logs and imaging devices Data from borehole logs: application to reservoir analysis

3. Petrophysical properties of carbonate reservoirs Saturation, Wettability, Capillarity Saturation Definition Determination of Sw and So Choosing m, n, and a exponents in the Archie equation Wettability Definition Water-wet and oil-wet reservoirs Capillarity and capillary properties of reservoirs Capillarity and capillary pressure Pore geometry, pore throats, and coordination numbers Capillary pressure curves and reservoir performance characteristics Converting mercury-air capillary pressure data to oil-water equivalents Height of oil column and pore-throat diameter calculations Mercury withdrawal efficiency and reservoir recovery efficiency

4. Stratigraphic principles Carbonate depositional platforms Rock, time, and time-rock units Correlation Anatomy of depositional units – depositional “architecture” Depositional facies and sequences Standard microfacies and standard sequences Sequence stratigraphy Definitions and scales of observation Carbonate sequence stratigraphy Sequence stratigraphy and reservoir characterization

5. Depositional carbonate reservoirs Depositional porosity Depositional Environments and Facies Depositional models for ramps and shelves Paleotopography and depositional facies Diagnosis and mapping of depositional reservoirs

6. Diagenetic carbonate reservoirs Environments of diagenesis Vadose, phreatic, mixing zone, and burial Diagenetic processes Dissolution, cementation, recrystallization, replacement, and compaction Diagenetic porosity Enhanced porosity: characteristics of dissolution, recrystallization, and replacement-generated pores. Reduced porosity: characteristics of compaction, cementation, pressure solution, replacement and recrystallization. Paleostructure and diagenetic reservoirs Diagnosis and mapping of diagenetic reservoirs

7. Fractured carbonate reservoirs Brittle fracture, structural geometry, and fracture types Fracture trends and structural geometry Core examination and diagnosis of fractured reservoirs Detecting natural fractures while drilling Borehole images for identifying and mapping fractures Generating a geological model for fractured reservoirs Diagnosis and mapping of fractured reservoirs

8. Visualizing and analyzing carbonate reservoirs Identifying and mapping reservoirs Petrological - petrophysical characterization Stratigraphy, petrography, log signatures, and capillary pressures Geological concept for reservoir origin and dimensions Flow units within reservoirs Identification, ranking, and mapping flow units Depositional, diagenetic, and fractured reservoirs Mapping techniques Porosity – permeability combinations Genetic pore classifications Special techniques – MICP, NMR, Image logs, and CT scans Spatial distribution of flow units in complex reservoir systems Predictive models for the three fundamental reservoir types Depositional reservoir models Diagenetic reservoir models Fractured reservoir models