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Geofluids
Volume 2017, Article ID 4278621, 17 pages
https://doi.org/10.1155/2017/4278621
Research Article

Numerical Investigation into the Impact of CO2-Water-Rock Interactions on CO2 Injectivity at the Shenhua CCS Demonstration Project, China

1School of Environmental Studies, China University of Geosciences, Wuhan 430074, China
2The Queensland Geothermal Energy Centre of Excellence, School of Mechanical and Mining Engineering, The University of Queensland, St Lucia, QLD 4072, Australia
3China Shenhua Coal Liquefaction Co., Ltd., Ordos 017209, China

Correspondence should be addressed to Yilian Li; nc.ude.guc@il.ly

Received 25 February 2017; Revised 17 May 2017; Accepted 28 June 2017; Published 3 August 2017

Academic Editor: Tianfu Xu

Copyright © 2017 Guodong Yang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

A 100,000 t/year demonstration project for carbon dioxide (CO2) capture and storage in the deep saline formations of the Ordos Basin, China, has been successfully completed. Field observations suggested that the injectivity increased nearly tenfold after CO2 injection commenced without substantial pressure build-up. In order to evaluate whether this unique phenomenon could be attributed to geochemical changes, reactive transport modeling was conducted to investigate CO2-water-rock interactions and changes in porosity and permeability induced by CO2 injection. The results indicated that using porosity-permeability relationships that include tortuosity, grain size, and percolation porosity, other than typical Kozeny-Carman porosity-permeability relationship, it is possible to explain the considerable injectivity increase as a consequence of mineral dissolution. These models might be justified in terms of selective dissolution along flow paths and by dissolution or migration of plugging fines. In terms of geochemical changes, dolomite dissolution is the largest source of porosity increase. Formation physical properties such as temperature, pressure, and brine salinity were found to have modest effects on mineral dissolution and precipitation. Results from this study could have practical implications for a successful CO2 injection and enhanced oil/gas/geothermal production in low-permeability formations, potentially providing a new basis for screening of storage sites and reservoirs.