The impact of pore size distribution data presentation format on pore structure interpretation of shales

Abstract

A deeper understanding of pore structures in unconventional shale plays can lead to a better evaluation of storage and transport capacity in these complicated rock types. This task is usually done through pore size distribution (PSD) analysis. In this study, N2 adsorption and high-pressure mercury intrusion porosimetry (MIP) were employed to investigate several shale samples. Three different mathematical forms of PSD data presentation: Incremental pore volume versus diameter (DV ), differential pore volume versus diameter (DV /Dd) and the log differential pore volume versus diameter (DV /Dlog d), were used to analyze pore structures from these two different methods. The comparison of the results showed that each form of PSD data presentation could demonstrate various types of important pore information. The DV curve is significantly dependent on the experimental data points’ spacing while the other two are not affected. The DV /Dd curve would incite the existence of smaller pore ranges while the DV /Dlog d would embolden larger pore ranges. Additionally, multifractal analysis from each data presentation style illustrated that the heterogeneity index of PSD calculated from the DV /Dd curve is much significant than the one obtained from the DV /Dlog d curve. DV /Dd is more appropriate to be used for characterizing PSD data from N2 adsorption while DV /Dlogd is preferred when MIP data is collected from larger pores.