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Enhanced Reservoir Characterization and Permeability Prediction of Heterogeneous Carbonate Reservoirs from Sonic Velocity and Digital Image Analysis

Thornton, John E.*1; Grammer, G. Michael 2
(1) Rockies Exploration, Shell Upstream Americas, Houston, TX.
(2) Michigan Geological Repository for Research and Education, Western Michigan University, Kalamazoo, MI.

Heterogeneous pore architecture complicates carbonate reservoir characterization due to the interplay of primary depositional fabrics and diagenetic processes. Ordovician Trenton and Black River carbonates in the Michigan Basin represent one of the classic examples for hydrothermal dolomite reservoirs, with main play strategies being directed by 3-D seismic to identify structural conduits related to flower structures. Recent work has shown, however, that secondary reservoirs exist due to lateral migration of reservoir-forming dolomite that is controlled by facies and stratigraphic architecture.

These secondary reservoirs are highly heterogeneous and have been highly altered by hydrothermal dolomite. Millimeter (thin section, minipermeameter), centimeter (core plug) and decimeter (whole core) scales of porosity and permeability measurement exhibit considerable variability in these carbonates, in part due to the influence of bioturbation and subsequent diagenetic alteration. Comparison of thin section porosity, core plug porosity and permeability and gridded minipermeability measurements on core show that porosity values may range from near zero to 8% and permeabilities may vary by several orders of magnitude within a one foot core interval.

Sonic velocity is a measure of both porosity and pore architecture in three dimensions, and thus may be used as a first order approximation of permeability. Digital image analysis measurements of pore architecture predict P-wave velocity of carbonate core plugs to within 5.3%. Permeability of carbonate core plugs is predicted with accuracy of 82% when two- and three-dimensional measures of pore architecture (digital image analysis of thin sections and sonic velocity of core plugs) are integrated with measures of porosity and density.

 

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California