Digital rock physics and laboratory considerations on a high-porosity volcanic rock

Laura L Schepp,Erik H Saenger,David Uribe,Donald A Swanson,Benedikt Ahrens,Maria Osorno,Mirko Siegert,Mandy Duda,Martin Balcewicz,Holger Steeb,Benoit Nigon,Ferdinand Stöckhert,Marcel Gurris,Mathias Nehler

doi:10.1038/s41598-020-62741-1

Abstract

Digital rock physics combines microtomographic imaging with advanced numerical simulations of effective material properties. It is used to complement laboratory investigations with the aim to gain a deeper understanding of relevant physical processes related to transport and effective mechanical properties. We apply digital rock physics to reticulite, a natural mineral with a strong analogy to synthetic open-cell foams. We consider reticulite an end-member for high-porosity materials with a high stiffness and brittleness. For this specific material, hydro-mechanical experiments are very difficult to perform. Reticulite is a pyroclastic rock formed during intense Hawaiian fountaining events. The honeycombed network of bubbles is supported by glassy threads and forms a structure with a porosity of more than 80%. Comparing experimental with numerical results and theoretical estimates, we demonstrate the high potential of in situ characterization with respect to the investigation of effective material properties. We show that a digital rock physics workflow, so far applied to conventional rocks, yields reasonable results for high-porosity rocks and can be adopted for fabricated foam-like materials with similar properties. Numerically determined porosities, effective elastic properties, thermal conductivities and permeabilities of reticulite show a fair agreement to experimental results that required exeptionally high experimental efforts.

Highlights

Digital rock physics combines microtomographic imaging with advanced numerical simulations of effective material properties
The cross sections of these struts have a triangular shape with a thickness ranging between approximately 45 μm and 75 μm as deduced from digital microscopy (Fig. 2) and Scanning Electron Microscope (SEM) measurements (Fig. 3)
SEM images on a different sample only sporadically show intact skins that are limited to comparatively small quadrilateral combs (Fig. 3)

Summary

Introduction

Digital rock physics combines microtomographic imaging with advanced numerical simulations of effective material properties. We consider reticulite an end-member for high-porosity materials with a high stiffness and brittleness. Comparing experimental with numerical results and theoretical estimates, we demonstrate the high potential of in situ characterization with respect to the investigation of effective material properties. We show that a digital rock physics workflow, so far applied to conventional rocks, yields reasonable results for high-porosity rocks and can be adopted for fabricated foam-like materials with similar properties. Determined porosities, effective elastic properties, thermal conductivities and permeabilities of reticulite show a fair agreement to experimental results that required exeptionally high experimental efforts. The present study focuses on DRP applied to a rock material considered as end-member with respect to porosity and stiffness (and brittleness) of the skeleton, reticulite.

Methods

Results

Conclusion