A fresh approach to investigating CO2 storage: Experimental CO2-water-rock interactions in a low-salinity reservoir system

Farquhar, S. M., Pearce, J. K., Dawson, G. K. W., Golab, A., Sommacal, S., Kirste, D., Biddle, D. and Golding, S. D. (2015) A fresh approach to investigating CO2 storage: Experimental CO2-water-rock interactions in a low-salinity reservoir system. Chemical Geology, 399 98-122. doi:10.1016/j.chemgeo.2014.10.006

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Author Farquhar, S. M.
Pearce, J. K.
Dawson, G. K. W.
Golab, A.
Sommacal, S.
Kirste, D.
Biddle, D.
Golding, S. D.
Title A fresh approach to investigating CO2 storage: Experimental CO2-water-rock interactions in a low-salinity reservoir system
Journal name Chemical Geology   Check publisher's open access policy
ISSN 0009-2541
Publication date 2015-04-02
Year available 2014
Sub-type Article (original research)
DOI 10.1016/j.chemgeo.2014.10.006
Volume 399
Start page 98
End page 122
Total pages 25
Place of publication Amsterdam, Netherlands
Publisher Elsevier
Language eng
Abstract The interactions between CO2, water and rock in low-salinity host formations remain largely unexplored for conditions relevant to CO2 injection and storage. Core samples and sub-plugs from five Jurassic-aged Surat Basin sandstones and siltstones of varying mineralogy have been experimentally reacted in low-salinity water with supercritical CO2 at simulated in situ reservoir conditions (P=12MPa and T=60°C) for 16days (384h), with a view to characterising potential CO2-water-rock interactions in fresh or low-salinity potential siliclastic CO2 storage targets located in Queensland, Australia. CO2-water-rock reactions were coupled with detailed mineral and porosity characterisation, obtained prior to and following reaction, to identify changes in the mineralogy and porosity of selected reservoir and seal rocks during simulated CO2 injection. Aqueous element concentrations were measured from fluid extracts obtained periodically throughout the experiments to infer fluid-rock reactions over time. Fluid analyses show an evolution of dissolved concentration over time, with most major (e.g. Ca, Fe, Si, Mg, Mn) and minor (e.g. S, Sr, Ba, Zn) components increasing in concentration during reaction with CO2. Similar trends between elements reflect shared sources and/or similar release mechanisms, such as dissolution and desorption with decreasing pH. Small decreases in concentration of selected elements were observed towards the end of some experiments; however, no precipitation of minerals was directly observed in petrography. Sample characterisation on a fine scale allowed direct scrutiny of mineralogical and porosity changes by comparing pre- and post-reaction observations. Scanning electron microscopy and registered 3D images from micro-computed tomography (micro-CT) indicate dissolution of minerals, including carbonates, chlorite, biotite members, and, to a lesser extent, feldspars. Quantitative mineral mapping of sub-plugs identified dissolution of calcite from carbonate cemented core, with a decrease in calcite content from 17vol.% to 15vol.% following reaction, and a subsequent increase in porosity of 1.1vol.%. Kinetic geochemical modelling of the CO2-water-rock experiments successfully reproduced the general trends observed in aqueous geochemistry for the investigated major elements. After coupling experimental geochemistry with detailed sample characterisation and numerical modelling, expected initial reactions in the near-well region include partial dissolution and desorption of calcite, mixed carbonates, chloritic clays and annite due to pH decrease, followed in the longer-term by dissolution of additional silicates, such as feldspars. Dissolution of carbonates is predicted to improve injectivity in the near-well environment and contribute to the eventual re-precipitation of carbonates in the far field.
Keyword Batch reaction experiments
CO2 storage
CO2-water-rock interactions
Low-salinity reservoirs
Surat Basin
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Earth Sciences Publications
School of Chemical Engineering Publications
Official 2015 Collection
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Citation counts: TR Web of Science Citation Count  Cited 23 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 21 times in Scopus Article | Citations
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Created: Tue, 18 Nov 2014, 01:34:36 EST by System User on behalf of School of Earth Sciences