Clarifying pore diameter, pore width, and their relationship through pressure measurements: A critical study. (September 2019)

• Record Type: Journal Article
• Authors: Rijfkogel, Luke S.; Ghanbarian, Behzad; Hu, Qinhong; Liu, Hui-Hai
• Is Part Of: Marine and petroleum geology. Volume 107(2019)
• Page Start: 142
• Page End: 148
• Publication Date: 2019-09
• Subjects: Pore diameter -- Pore width -- Pore size distribution -- Mercury porosimetry -- Nitrogen sorption isotherm; Submarine geology -- Periodicals; Petroleum -- Geology -- Periodicals; Géologie sous-marine -- Périodiques; Pétrole -- Géologie -- Périodiques; Petroleum -- Geology; Submarine geology; Periodicals; Electronic journals; 551.468
• DOI: 10.1016/j.marpetgeo.2019.05.019
• Languages: English
• ISSNs: 0264-8172

Abstract

Abstract: Understanding geometrical and topological properties of the pore space in permeable media is of paramount importance, particularly in oil and gas production. Pore space characteristics such as pore sizes and their probability distributions, as well as pore's connectivity are main factors in the modeling of fluid flow and chemical transport in soils and rocks. A common method to determine the pore size is to convert an implemented pressure via either the Young-Laplace or Kelvin equation by assuming a specific pore shape. Simple geometries such as cylindrical and slit-shaped have been frequently used in the literature, particularly to represent pores and to derive theoretical models estimating permeability from pore-throat size distribution. In this study, we clarify the relationship between pore diameter ( d ) and pore width ( w ), two terms interchangeably used in the literature. The former corresponds to a cylindrical pore, while the latter to a slit-shaped one. We emphasize that d = 2 w, in contrast to previously published studies claiming that the diameter of a cylindrical pore is equal to the distance between sides of a slit-shaped pore (i.e., d = w ). In addition, we discuss that comparing/combining pore size distribution derived from mercury intrusion porosimetry and that determined from nitrogen adsorption isotherm is not supported, unless the effect of hysteresis is trivial, as most probably the former represents pore-throat while the latter pore-body size distributions. Highlights: Diameter of a cylindrical pore is twice as large as width of a slit-shaped pore ( d = 2 w ). Assuming d = w results into inaccurate predictions of permeability. Mercury intrusion porosimetry and nitrogen adsorption isotherm are not combinable, unless hysteresis is negligible.