Ensuring well injectivity and integrity over the lifetime of CO2 geological storage operations is crucial for both the technical and economical success of such projects. Another key point is the monitoring issue, which requires reliable parameters to convert seismic data into CO2 saturation distribution maps. A specific difference between CO2 injection and conventional hydrocarbon gas injection is the possibility of geochemical reactions between the mobile reactive brine and the host formation during CO2 injection leading to modifications of the rock flow, geomechanical and petro-acoustical properties. The main objective of the paper is to experimentally investigate the variation of these properties for several levels of rock alteration. For the first time an innovative experimental procedure leading to a homogeneous dissolution pattern of the rock samples, avoiding especially any wormholing process that would drive to erroneous measurements at the core scale is presented. The proposed approach relies on the injection of a retarded acid solution, which is activated only when in place under specific temperature conditions. Porosity, permeability, geomechanical and petro-acoustical measurements were performed both on a low and a high permeability set of carbonate samples, either under their native state or different states of alteration. The results show that permeability evolution follows an increasing trend due to the dissolution process. Nevertheless, permeability increases are rather limited even in the case of very pronounced porosity increases (4-5 porosity units). This effect is attributed to the mobilization of fines that are destabilized when the rock alteration is severe. From the geomechanical and petro-acoustical points of view, altered samples usually show a decrease in stiffness and shear strength. To our knowledge, similar set of petrophysical measurements conducted on samples with different levels of rock alteration has not been published earlier. Therefore, this work will contribute to the development of the constitutive laws to be implemented in the geomechanical reactive transport simulators used to model the geological CO2 storage.
An experimental investigation of the rock properties evolution associated to different levels of CO2 injection like alteration processes
Experimentelle Untersuchung der Veränderungen von Gesteinseigenschaften in Verbindung mit verschiedenen CO2-Injektionsgraden
2006
15 Seiten, 9 Bilder, 1 Tabelle, 28 Quellen
Aufsatz (Konferenz)
Englisch
Bohrloch , CO2 , Lagerung (Vorrat) , Sättigung , Injektion , Kohlenwasserstoff , Salzlösung , Gestein , Fließen , Temperatur , Porosität , Permeabilität , Auflösung , feines Pulver , Steifigkeit , Scherfestigkeit , akustische Eigenschaft
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