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Quantitative Approach to Mineralogy and Porosity Determinations

Hoal, Karin 1; Stammer, Jane 1; Appleby, Sarah 1
1 Advanced Mineralogy Research Center, Colorado School of Mines, Golden, CO.

The key parameters used in characterizing rocks include mineralogy, modal mineral proportions, mineral relationships and associations, porosity, and fracture distribution. Once identified and quantified, these parameters then can be linked to physical characteristics of the materials such as density, conductivity, permeability, and hardness. Traditionally, optical microscopy coupled with other techniques such as x-ray diffraction, x-ray fluorescence, electron microprobe, and scanning electron microscopy have been used to identify these attributes, but either the contextual information is lost (textures, associations) or the sample population is too small to make predictive assessments of how the materials behave in the ground or in response to a mechanism such as fluid flow. The Colorado School of Mines Advanced Mineralogy Research Center is the first institution to use quantitative mineralogical tools in a research and applications environment. The system used is a QEMSCAN® instrument, which utilizes four EDS detectors and a powerful software platform to obtain images and digital data at 150 determinations per second. Large sample sets such as thousands of well cuttings particles, and small areas such as micron-scale porosity determinations, provide spatial and numeric mineralogical information that apply to predicting materials behavior during resource extraction. This quantitative mineralogy technology was originally developed for the mining industry, where fluid flow, mineralization, and alteration directly impact the behavior of rocks during processing and extraction. We have applied it to oil shales, carbonates, siliciclastics, and clay-rich rocks where porosity, fracture distribution, and mineralogical relationships impact process development. Examples such as modal variations and pore-throat mineral determinations, quantified over significant intervals, demonstrate the importance of key mineral attributes to reservoir studies. Utilizing geomet concepts that integrate geology, mineralogy, processing, and environmental impact, economic models illustrate the financial benefit of conducting up-front mineral characterization.


AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009