Multiscale porosity measurements of Shale rocks using multiple gas adsorption and mercury intrusion porosimetry

Unconventional oil and gas production from shale has revolutionized the world energy landscape. Shale is a fine-grained sedimentary rock, composed of solid organic matter (OM) scattered in a mineral framework. The decomposition of this OM at high temperature leads to the generation of hydrocarbons during a process known as maturation. The resulting organic matter develops a nanoscale porosity that governs the ability of a shale petroleum reservoir to store and then to yield oil and gas. The mineral matrix also contributes to the overall porosity leading to a pore size distribution spanning from a few Å to the µm range. In this work, we have combined gas adsorption of multiple gases (CO₂, H₂, N_2, and Ar) and mercury intrusion porosimetry to study the pore system of 5 samples from the Vaca Muerta formation that differ in maturities. Indeed, while gas adsorption allows probing the micro and mesoporosity (< 50nm), mercury intrusion allows for the characterization of the macroporosity (10nm to 500µm). Rather than using a fragmented approach of simple overlays from individual techniques, a unified approach that utilizes a kernel constructed from model isotherms and model intrusion curves is used to calculate the complete pore size distribution and the total pore volume of the material.