title: Pore-scale micro-computed-tomography imaging: nonwetting-phase cluster-size distribution during drainage and imbibition.
abstract: We investigated the cluster-size distribution of the residual nonwetting phase in a sintered glass-bead porous medium at two-phase flow conditions, by means of micro-computed-tomography (μCT) imaging with pore-scale resolution. Cluster-size distribution functions and cluster volumes were obtained by image analysis for a range of injected pore volumes under both imbibition and drainage conditions; the field of view was larger than the porosity-based representative elementary volume (REV). We did not attempt to make a definition for a two-phase REV but used the nonwetting-phase cluster-size distribution as an indicator. Most of the nonwetting-phase total volume was found to be contained in clusters that were one to two orders of magnitude larger than the porosity-based REV. The largest observed clusters in fact ranged in volume from 65% to 99% of the entire nonwetting phase in the field of view. As a consequence, the largest clusters observed were statistically not represented and were found to be smaller than the estimated maximum cluster length. The results indicate that the two-phase REV is larger than the field of view attainable by μCT scanning, at a resolution which allows for the accurate determination of cluster connectivity.
authors.affiliation: Shell Global Solutions International BV, Rijswijk, The Netherlands and Department of Chemical Engineering, Imperial College London, United Kingdom.
authors.forename: A
authors.initials: A
authors.lastname: Georgiadis
authors.forename: S
authors.initials: S
authors.lastname: Berg
authors.forename: A
authors.initials: A
authors.lastname: Makurat
authors.forename: G
authors.initials: G
authors.lastname: Maitland
authors.forename: H
authors.initials: H
authors.lastname: Ott