Supplementary Studies of Textural and Mineralogical Changes in Reservoir and Caprocks from Selected Potential Sites Suitable for Underground CO2 Storage

Abstract

The purpose of this article is to present the results of the study, which are supplementary to the results obtained earlier by Tarkowski and Wdowin in Oil Gas Sci Technol 66:137-150, 2011, on the impact of CO2 on rocks in order to determine the effects of carbon dioxide sequestration. Its aim was to observe changes, in textural parameters (BET surface area, pore size distribution) and mineral composition, resulting from experimental exposure of reservoir and caprock samples to CO2 at subsurface conditions. The samples were Jurassic (sandstones, dolostone) and Cretaceous (sandstones, limestone) rocks of central Poland. The experiments were conducted in the presence of CO2 and brines for a 3-month period at simulated formation conditions (T = 55 °C, P = 12 MPa-Jurassic, T = 45°C, P = 10 MPa-Cretaceous) using a laboratory apparatus. An increase in BET surface area was observed in sandstones after the experiment. The analysis of dolostone revealed a decrease in the BET values and a slight increase of this parameter was observed in limestone. The clay fraction in the dolostone showed the presence of kaolinite and micas in mineral composition. Illite-smectite from the clay fraction of the limestone showed a shift of the d(001) basal spacing towards lower values due to the replacement of calcium by sodium (from Jackson treatment) in the interlayer space. This shift proves the occurrence of smectite layers. The mineral compositions and surface parameters of the studied reservoir and caprocks indicate that rock properties changed very differently. © 2013 The Author(s).