It is well known that the seismic velocity in sandstones saturated with brine does not depend on temperatures in the range of 34–38 °C (e.g. Mavko, 2005). To demonstrate this we calculated the difference in Vp between both temperature scenarios present at the Ketzin site at the time of the 1st 3D seismic repeat campaign (Ivanova et al., 2012) using Gassmann's equations (1951) for 50% CO2 saturation. The resulting difference between the scenarios in Vp is less than 5 m/s. Considering the uncertainties (e.g. ±5% error in CO2 saturation) in the petrophysical experiments (Kummerow and Spangenberg, 2011; Ivanova et al., 2012) corresponding to ±70 m/s in Vp (Fig. 5), we did not take into account the Vp changes (Fig. 5, Eq. (1)) due to the different temperature scenarios (34 and 38 °C).
seismic velocity in sandstones saturated with brine does not depend on
temperatures
range of 34–38 °C
°C
CO2 saturation
50%
%
scenarios
Vp
less than 5 m/s
m/s
CO2 saturation
error
±5%
%
petrophysical experiments
Vp
±70 m/s
m/s
scenarios
temperature
34 and 38 °C
°C