Measuring, imaging and modelling solute transport in a microporous limestone

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Title: Measuring, imaging and modelling solute transport in a microporous limestone
Authors: Kurotori, T
Zahasky, C
Hosseinzadeh Hejazi, SA
Shah, S
Benson, S
Pini, R
Item Type: Journal Article
Abstract: The analysis of dispersive flows in heterogeneous porous media is complicated by the appearance of anomalous transport. Novel laboratory protocols are needed to probe the mixing process by measuring the spatial structure of the concentration field in the medium. Here, we report on a systematic investigation of miscible displacements in a microporous limestone over the range of Péclet numbers, . Our approach combines pulse-tracer tests with the simultaneous imaging of the flow by Positron Emission Tomography (PET). Validation of the experimental protocol is achieved by means of control experiments on random beadpacks, as well as by comparing observations with both brine- and radio-tracers (labelled with 11C or 18F). The application of residence time distribution functions reveals mass transport limitations in the porous rock in the form of a characteristic flow-rate effect. Two transport models, namely the Advection Dispersion Equation (ADE) and the Multi-Rate Mass Transfer (MRMT) model, are thoroughly evaluated with both the experimental breakthrough curves and the internal concentration profiles. We observe that the dispersion coefficient scales linearly with the Péclet number for both porous systems. The tracer profiles acquired on the rock sample are successfully described upon application of the MRMT model that uses two representative grain sizes and a fraction of intra-granular pore space that is independent of the fluid velocity. The analysis of the PET images evidences the presence of macrodispersive spreading caused by subcore-scale heterogeneities, which contribute significantly to the value of the estimated core-scale dispersivity. This effect can be significantly reduced upon application of the ‘dispersion-echo’ technique, which enables decoupling the effects of spreading and mixing in heterogeneous porous media. These observations are likely to apply to any laboratory-scale rock sample and the approach presented here provides a practical means to study anomalous transport in these systems.
Issue Date: 16-Mar-2019
Date of Acceptance: 2-Nov-2018
ISSN: 1873-4405
Publisher: Elsevier
Start Page: 366
End Page: 383
Journal / Book Title: Chemical Engineering Science
Volume: 196
Copyright Statement: © 2018 Elsevier Ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Licence
Sponsor/Funder: Qatar Shell Research and Technology Center QSTP LLC
Qatar Shell Research and Technology Center QSTP LLC
Qatar Petroleum
Funder's Grant Number: 490000724
Keywords: 0904 Chemical Engineering
0913 Mechanical Engineering
Chemical Engineering
Publication Status: Published
Embargo Date: 2019-11-03
Online Publication Date: 2018-11-03
Appears in Collections:Faculty of Engineering
Chemical Engineering

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