Caprock analysis from the Mihályi-Répcelak natural CO2 occurrence, Western Hungary

Csilla Király, Ágnes Szamosfalvi, László Zilahi-Sebess, Péter Kónya, I. Kovács, Eszter Sendula, Csaba Szabó, György Falus

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Abstract

Caprock integrity is one of the most important factors regarding the long-term safe underground storage of CO2. As a result of geochemical reactions among the caprock mineralogy and CO2 saturated pore water, the physical properties of caprock such as porosity, permeability may change, which could affect its sealing capacity. Natural CO2 occurrences can help to understand these long term reactions under storage conditions on geological timescale. Our study area, the Mihályi-Répcelak natural CO2 occurrence, is believed to be leak-proof system on geological timescale. To identify and understand the mineral reactions in the caprocks we applied XRD, FTIR-ATR and SEM analysis of drill cores derived from the study area. The petrophysical properties of the studied rock samples were determined from the interpretation of geophysical well-logs and grain size distribution. The effective porosity (~4 %), permeability (0.026 mD) and clay content (~80 %) of the drill cores imply that the studied clayey caprocks represent an adequate physical barrier to the CO2. Our analytical results show that dawsonite has formed within the caprocks. In most cases the dawsonite crystallized after albite dissolution. This implies that CO2 or CO2-saturated brine can penetrate into the caprock resulting in mineral reactions and most likely changing the porosity and permeability of the sealing lithology. On the other hand the caprock may react as a geochemical buffer for the CO2 and, at least part of it, can be stored within the caprock as solid phase, thereby increasing the storage capacity of the system.

Original languageEnglish
Article number635
JournalEnvironmental Earth Sciences
Volume75
Issue number8
DOIs
Publication statusPublished - Apr 1 2016

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Keywords

  • Caprock analysis
  • Dawsonite
  • Natural CO occurrence
  • Pannonian Basin
  • Physical properties

ASJC Scopus subject areas

  • Soil Science
  • Environmental Chemistry
  • Water Science and Technology
  • Pollution
  • Global and Planetary Change
  • Geology
  • Earth-Surface Processes

Cite this

Király, C., Szamosfalvi, Á., Zilahi-Sebess, L., Kónya, P., Kovács, I., Sendula, E., Szabó, C., & Falus, G. (2016). Caprock analysis from the Mihályi-Répcelak natural CO2 occurrence, Western Hungary. Environmental Earth Sciences, 75(8), [635]. https://doi.org/10.1007/s12665-016-5399-6