Wave Propagation in Porous Media Saturated with Two Fluids Is it Feasible to Detect Leakage of a CO2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {CO}_{2}$$\end{document} Storage Site Using Seismic Waves?

• Published in: Transport in porous media Vol. 107; no. 1; pp. 49 - 63
• Main Authors: Boxberg, Marc S., Prévost, Jean H., Tromp, Jeroen
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 2015
• Subjects: Civil Engineering; Classical and Continuum Physics; Earth and Environmental Science; Earth Sciences; Geotechnical Engineering & Applied Earth Sciences; Hydrogeology; Hydrology/Water Resources; Industrial Chemistry/Chemical Engineering; Unsaturated porous media; Wave propagation; Biot theory; Geologic carbon sequestration; Monitoring
• ISSN: 0169-3913; 1573-1634
• DOI: 10.1007/s11242-014-0424-2

When it comes to geological storage of
CO
2
, monitoring is crucial to detect leakage in the caprock. In our study, we investigated the wave speeds of porous media filled with
CO
2
and water in order to determine reservoir changes. We focused on deep storage sites where
CO
2
is in a supercritical state. In case of a leak,
CO
2
rises and eventually starts to boil as soon as it reaches temperatures or pressures below the critical point. At this point, there are two distinct phases in the pore space. We derived the necessary equations to calculate the wave speeds for unsaturated porous media and tested the equations for a representative storage scenario. We found that there are three modes of pressure waves instead of two for the saturated case. The new mode has a very small wave speed and is highly attenuated. This mode will most likely be very hard to detect in practice and therefore it may be necessary to use time-lapse seismic migration to detect leakage.