Pore Analysis of Mississippian Carbonate Reservoir in Southwest Kansas Using Petrographic Image Analysis

Robert J. Dietterich, W. E. Full

Petrographic image analysis (PIA) provides pore data that can be analyzed via vector-analytic algorithms and regression analysis. Results define various pore types within the reservoir, and indicate pore variables and specific pore types that influence permeability. This information can be used to determine reservoir characteristics important to hydrocarbon production.

A reservoir in the St. Louis Limestone (Mississippian) in southwest Kansas was subjected to PIA. The Damme field, located in Finney County, Kansas, consists of an oolitic-skeletal grainstone with well-developed intergranular porosity. PIA, using a computer-based pore-analysis system designed at the University of South Carolina, provided variables defining the pore complex. Analysis of these variables via EXTENDED CABFAC/QMODEL unmixing algorithms separated pores into distinct classes or clusters. Within the reservoir, five clusters were defined; two clusters were from low-porosity areas represented by small, rough pores with no interconnections.

The highly porous producing zone defined by three clusters contains medium to large, moderately smooth pores with enhanced interconnections in two clusters and isolated pores in the third. Regression analysis of pore types and pore data versus core-measured permeability indicates number and size of pore throats, and certain pore types that influence permeability. Permeability can be predicted with R² values up to 0.98. Combining computer-based analysis with petrophysical and geophysical data provides the information needed for a detailed reservoir description.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.