Numerical modeling of self-limiting and self-enhancing caprock alteration induced by CO2 storage in a depleted gas reservoir

Numerical modeling of self-limiting and self-enhancing caprock alteration induced by CO 2 storage in a depleted gas reservoir Fabrizio Gherardi 1, *, Tianfu Xu 2 and Karsten Pruess 2 Istituto di Geoscienze e Georisorse (IGG) – Consiglio Nazionale delle Ricerche (CNR), 56124 Pisa, Italy Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 * Corresponding author. Tel.: +39 050 315 3409; fax: +39 050 315 2322; E-mail address: f.gherardi@igg.cnr.it Abstract This paper presents numerical simulations of reactive transport which may be induced in the caprock of an on-shore depleted gas reservoir by the geological sequestration of carbon dioxide. The objective is to verify that CO 2 geological disposal activities currently being planned for the study area are safe and do not induce any undesired environmental impact. In our model, fluid flow and mineral alteration are induced in the caprock by penetration of high CO 2 concentrations from the underlying reservoir, where it was assumed that large amounts of CO 2 have already been injected at depth. The main focus is on the potential effect of precipitation and dissolution processes on the sealing efficiency of caprock formations. Concerns that some leakage may occur in the investigated system arise because the seal is made up of potentially highly-reactive rocks, consisting of carbonate-rich shales (calcite+dolomite averaging up to more than 30% of solid volume fraction). Batch simulations and multi-dimensional 1D and 2D modeling have been used to investigate multicomponent geochemical processes. Numerical simulations account for fracture-matrix interactions, gas

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