Pore Scale Observations of Trapped CO2 in Mixed-Wet Carbonate Rock: Applications to Storage in Oil Fields

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Title: Pore Scale Observations of Trapped CO2 in Mixed-Wet Carbonate Rock: Applications to Storage in Oil Fields
Authors: Al-menhali, A
Menke, H
Blunt, MJ
Krevor, SC
Item Type: Journal Article
Abstract: Geologic CO2 storage has been identified as a key to avoiding dangerous climate change. Storage in oil reservoirs dominates the portfolio of existing projects due to favorable economics. However, in an earlier related work (Al-Menhali and Krevor Environ. Sci. Technol. 2016, 50, 2727−2734), it was identified that an important trapping mechanism, residual trapping, is weakened in rocks with a mixed wetting state typical of oil reservoirs. We investigated the physical basis of this weakened trapping using pore scale observations of supercritical CO2 in mixed-wet carbonates. The wetting alteration induced by oil provided CO2-wet surfaces that served as conduits to flow. In situ measurements of contact angles showed that CO2 varied from nonwetting to wetting throughout the pore space, with contact angles ranging 25° < θ < 127°; in contrast, an inert gas, N2, was nonwetting with a smaller range of contact angle 24° < θ < 68°. Observations of trapped ganglia morphology showed that this wettability allowed CO2 to create large, connected, ganglia by inhabiting small pores in mixed-wet rocks. The connected ganglia persisted after three pore volumes of brine injection, facilitating the desaturation that leads to decreased trapping relative to water-wet systems.
Issue Date: 17-Aug-2016
Date of Acceptance: 17-Aug-2016
ISSN: 0013-936X
Publisher: American Chemical Society
Start Page: 10282
End Page: 10290
Journal / Book Title: Environmental Science & Technology
Volume: 50
Issue: 18
Copyright Statement: This document is the Accepted Manuscript version of a Published Work that appeared in final form in Environmental Science & Technology, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see
Sponsor/Funder: Qatar Shell Research and Technology Center QSTP LLC
Qatar Science & Technology Park
Funder's Grant Number: 490000724
Keywords: Environmental Sciences
MD Multidisciplinary
Publication Status: Published
Appears in Collections:Faculty of Engineering
Earth Science and Engineering

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