Bernard Giroux edited Experimental results.tex  over 9 years ago

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\subsection{Experimental results}  An essential characteristic of the measurements was to ensure that the variations of the waveform are linked only to the change on of  the properties of fluids and not to changes in pressure. Thus, all measurements were carried out at constant differential pressure of 14 MPa (corresponding to the reservoir conditions) by varying the confining pressure and the pore pressure according to: to  \begin{equation}   P_{d} = P_{c} - P_{p} P_{p},  \end{equation}  where $P_{d}$ is differential pressure, $P_{c}$ is  confining pressure and $P_{p}$ is  pore pressure.\\ pressure.  As the sample is buffered by two alluminium cap, the travel time measured must be corrected to obtain the wave velocity $\nu$ of the sample using: using  \begin{equation}   \nu = \frac{L_{s}}{t_{bs}-t_{b}} \frac{L_{s}}{t_{bs}-t_{b}},  \end{equation}  where $L_s$ is the sample length and $t_{bs} - t_{b}$ is the difference between the travel time through the alluminum buffer and the sample $t_{bs}$ and the traveltime through the alluminum buffer without sample $t_b$.\\ $t_b$.  We presents here the measurements made for full CO$_2$ saturation at two constant temperature (25 and 35 $^{\circ}$C) with the pore pressure varying form 2 to 25 MPa in each case. Carbon dioxide is a gas in gaseous state  at low lower  pore pressure pressure,  and in  liquid or supercritical fluid state  at higher pore pressures pressures,  depending on the temperature as shown in Fig. \ref{fig:fig3}. Wave velocities and signal amplitude for P- $P$-  and S-wave of $S$-wave for  the two constant temperature runs are plotted in Fig \ref{fig:fig4}. In each subplots, CA (red) and CH (yellow) results are shown.\\