Abstract

Microporous aggregates of kaolin minerals and illite are common products filling the intergranular volume (IGV) of deeply buried sandstones. Using BSEi (backscattered electron imaging), a full analysis of IGV is difficult and time consuming since it necessitates a two-step process, at the scales of (1) macroporosity between the detrital grains, and (2) microporosity within the clay aggregates. The 14C-PMMA method permits the mapping and quantification of the connected porosity in sandstone core samples across scales. This method is based on the complete impregnation of the connected porosity by 14C-labeled MethylMethAcrylate (MMA) monomer, and its subsequent in situ polymerization. Imaging the spatial distribution of the radioactive tracer within a section of an impregnated sample allows an integrated analysis of IGV from the core scale to the nanometer scale. This technique is illustrated through analysis of the clay cement of a medium- to coarse-grained sandstone from the Athabasca Basin (Canada). The measured connected porosity distributions of kaolin mineral aggregates (average porosity 42%) and illite fillings (average porosity 70%) are in accordance with Gaussian distributions. This method also permits quantification of the relative volumetric amounts of the both illite and kaolin aggregate.

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