Evolution of overmature marine shale porosity and implication to the free gas volume

The porosities of the Lower Cambrian shale and Upper Ordovician-Lower Silurian marine shale from the Sichuan Basin were analyzed using He-Hg porosimetry and field-emission scanning electron microscopy, to discuss the relationship of porosity to the organic matter maturity, total organic carbon (TOC) and free gas volume. Overmature (Ro greater than 2%) shale samples with a TOC less than 5% display a positive correlation between TOC and porosity,...