Enhanced pore space analysis by use of &amp;lt;i&amp;gt;μ&amp;lt;/i&amp;gt;-CT, MIP, NMR, and SIP

Zeyu Zhang,Matthias Halisch,Andreas Weller,Sabine Kruschwitz

doi:10.5194/se-9-1225-2018

Abstract

Abstract. We investigate the pore space of rock samples with respect to different petrophysical parameters using various methods, which provide data on pore size distributions, including micro computed tomography (μ-CT), mercury intrusion porosimetry (MIP), nuclear magnetic resonance (NMR), and spectral-induced polarization (SIP). The resulting cumulative distributions of pore volume as a function of pore size are compared. Considering that the methods differ with regard to their limits of resolution, a multiple-length-scale characterization of the pore space is proposed, that is based on a combination of the results from all of these methods. The approach is demonstrated using samples of Bentheimer and Röttbacher sandstone. Additionally, we compare the potential of SIP to provide a pore size distribution with other commonly used methods (MIP, NMR). The limits of resolution of SIP depend on the usable frequency range (between 0.002 and 100 Hz). The methods with similar resolution show a similar behavior of the cumulative pore volume distribution in the overlapping pore size range. We assume that μ-CT and NMR provide the pore body size while MIP and SIP characterize the pore throat size. Our study shows that a good agreement between the pore radius distributions can only be achieved if the curves are adjusted considering the resolution and pore volume in the relevant range of pore radii. The MIP curve with the widest range in resolution should be used as reference.

Highlights

Transport and storage properties of reservoir rocks are determined by the size and arrangement of the pores
In this paper we use the term geometry to refer to the relevant pore sizes, such as the pore throat radius, pore body radius, body to throat ratio, shape of the pore, and pore volume corresponding to a certain pore radius
The sample investigated in our study is characterized by a porosity of 0.238 measured by mercury intrusion porosimetry (MIP), a gas permeability of 4.25 × 10−13 m2, and a specific surface area of 0.3 m2 g−1 determined by the nitrogen adsorption method

Summary

Introduction

Transport and storage properties of reservoir rocks are determined by the size and arrangement of the pores. Different methods have been developed to determine the pore size distribution of rocks. These methods are based on different physical principles. It can be expected that the methods recognize different geometries and sizes. The ranges of pore sizes that are resolved by the methods are different (Meyer et al, 1997). Rouquerol et al (1994) stated in the conclusions of their recommendations for the characterization of porous solids that no experimental method provides the absolute value of parameters such as porosity, pore size, surface area, or surface roughness. That means that the value of the parameter depends on the spatial resolution of the method

Objectives

Results

Discussion

Conclusion