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.