Pore Characterization Utilizing CCSEM Image Analysis in Diagenetically Overprinted Carbonates

Robert M. Rogers and Tore Wiksveen
University of Texas at Arlington, USA

Understanding attributes of Leonardian aged tidal flat and intertidal carbonate pore systems can be a major aid in the completion process of any well. The purpose of this project was to capture digital SEM images from polished and epoxy impregnated samples. Images were captured from low magnification (LMSEM: 500-50,000 microns) to high magnification (HMSEM: 0.5- 500 microns) and Binarize LMSEM images into a macropore and matrix phase by assigning pore phases to all pixels containing white or gray and to binarize HMSEM images into a micropore and solid phase by utilizing a threshold. Image analysis software locates and labels each pore, surface area, perimeter, and diameter. A stage file created five pore size classes and differentiated between pore areas: 0.5-49um², 50-499um², 500-4999um², and 5000-50,000um².

Utilizing a 2-point scan, initial analysis showed a discrepancy between the total porosity of the sample calculated on the SEM and those calculated using gas expansion. The average total area for each sample was 5.8mm². The porosity varied from the gas porosity by an average of 120%.

A second 8-point system was used to calculate the porosity of each sample. The area scanned was 46mm², with gas analysis varying from SEM analysis by 75%. Reduction in the discrepancy between sample analysis and gas analysis was due to large variability in the porosity of each sample. While an 8-point analysis is advantageous for initial quantification, more accurate representation of the porosity may be obtained by creating a rectangular area encompassing the entirety of the sample.

AAPG Search and Discovery Article #90182©2013 AAPG/SEG Student Expo, Houston, Texas, September 16-17, 2013