*3.2. Velocity Variation from Logging Data to Seismic Data Based on Rock Physics Model and Backus Averaging Method*

In this section, logging data is used for demonstration of velocity difference between upscaling by the pore fluid dissolution model and the Backus averaging method. Firstly, the Backus averaging method is applied, and the velocity variation is shown in Figure 5. Using different sizes of windows, the velocity results from the Backus averaging method show different properties. As the size of the window becomes larger, the velocity curve shows larger divergence from the real data. However, the velocity from all these three cases varies in the same range as that of the real data.

**Figure 5.** P\_wave velocity calculated by using the Backus averaging method. The red solid curve is the real data, and the blue dash curve is the result from the Backus averaging method. (**a**) 16 samples in a window, (**b**) 8 samples in a window, (**c**) 4 sample in a window.

Then, the SLS model and the constant Q model are both applied to the real data for velocity correction. The results are shown in Figure 6. Compared with that of the Backus averaging method, the velocity upscaled by the SLS model and constant Q model contains obvious variation from read data. Both the models result in smaller velocity values than the real data. The SLS model always yields smaller velocity than the constant Q model in these cases.
