Interpretation method of tight sandstone based on seismic forward modeling: a case study of Permian in Southeast Ordos Basin

Based on Permian data and the reflection coefficient convolved 0 degrees and 90 degrees phase ricker wavelets form different phases of synthetic seismic sections. This paper theoretically discusses three aspects: one is Permian sandstone thickness and seismic amplitude, the second is tight sandstone (tuning) thickness and seismic wave frequency, and the last is tight sandstone and seismic wave phase. The result shows that when sandstone thickness is greater than seismic wavelength lambda/4, the sandstone thickness can be determined through the time difference between the sandstone's top and bottom Peaks and troughs. When sandstone thickness is less than lambda/4, only the seismic reflection amplitude of the top surface of sandstone was used to determine the thickness of sandstone. In the 0 degrees phase seismic model, peaks were located on the thin layer's upper part and trough in the lower half, with no correspondence between the polar and lithology. In the 90 degrees phase synthesis record, the thin sandstone layer roughly corresponds to the seismic reflection trough. 0 degrees and 90 degrees phase synthesis have the exact vertical resolution; the frequency variation can reflect sand body distribution. The optimal frequency makes the thickest layer of sandstone reach amplitude-frequency tuning (tuning frequency).