Fracture and Karst Features Affecting Reservoir Performance in a Mississippian Reservoir, Cheyenne County, Colorado

Kansas Geological Survey

KGS Open-file 2006-14

Core to Log Comparison

Composition Graph

We use an Excel spreadsheet to set up the matrix algebra solution for compositional analysis. The MINVERSE function within Excel is used to perform the operation through inversion of the matrix of the log properties of the components.
The logs used in the composition analysis are: Gamma Ray, Neutron Porosity (percent), Bulk Density, and Photoelectric Volumetric Cross Section. By premultiplying the logs by this inverse matrix, we can determine the percentage of calcite, dolomite, quartz, shale, and porosity.


Composition graphs using GR, Neutron porosity (percent), Photoelectric, Grain Density, and Bulk Density.


Porosity Comparison

Porosity from core analysis is plotted against Neutron Density Average porosity from logs. There is a fairly good match between the two data sets for the Spergen section.

Last Modified May 2006