## 5 Sandstone Prediction by Seismic Inversion  
The sensitive density curve and shale content curve are used to simulate the waveform indication. The initial velocity is calculated by acoustic DT, the density is calculated by GGK density curve, and the zero-phase wavelet and the main frequency of 25 Hz are used for synthetic recording, based on which of the seismic calibration of key wells is carried out. The waveform characteristics of seismic records are in good agreement with synthetic records, and the correlation coefficient is higher (both above 0.58). The sensitivity of acoustic  
Figure 8: Well-seismic tie profile showing the sequence correlation feature (C-A-B). Figure 7: Well tie profile showing the sequence correlation feature (C-A-B). DT and wave impedance is poor, which cannot effectively distinguish sandstone from mudstone (Figure 9). However, the GGK (density) and VSH (shale content) are sensitive to sand and mud, and, therefore, are used to predict the distribution of sand bodies. The GGK parameter waveform simulation results show that sand bodies of SQ3-1 and SQ3-2 (J2-J4) and sand bodies of SQ3-4 and SQ3-5 (J7-J8) have relatively good prediction results. However, the sand body description effect of SQ4-1(9) is not very accurate (Figure 10). Comparatively, the simulation results of the VSH parameter waveform indicate that the sand body distribution of the inversion body is in high agreement with the interpretation conclusion on the well, and the sand body distribution features that the sand bodies of SQ3-4, SQ3-5, and SQ4-1 are more developed than those of SQ3-1 and SQ3-2 (Figure 11). Both results show that the top and bottom of SQ3 developed good reservoir sandstones. Figure 10: Well-seismic-tie profile showing the GGK simulation result with the red color indicating a high sandstone ratio (G-C-A-B-D-F-E). Figure 9: Sensitivity of acoustic DT (**a**), wave impedance (**b**), GGK (**c**), and VSH (**d**) to distinguish sandstone from mudstone. The average amplitude attribute and stratum thickness of all fourth-order sequences are extracted and compared with the results of the GGK density inversion and VSH shale content parameter inversion of the sand body thickness. The inversion thickness maps of the main sandstone reservoirs (SQ3-1, SQ3-2, SQ3-4, and SQ3-5) are made to show the sandstone distribution features of these fourth-order sequences (Figure 12). Figure 11: Well-seismic tie profile showing the VSH simulation result with the red color indicating a high sandstone ratio (G-C-A-B-D-F-E). SQ1-1: The average amplitude attribute is quite different from the inversion thickness of strata and sand bodies and the thickness of strata, probably because the overall amplitude of the seismic reflection layer here is strong. SQ1-1 sequence thickness is mainly between 13.4 and 51.3 m. The sand body inversion results of SQ1-1 show that the sequence sandstone is developed in the south of the study area. SQ2-1: The average amplitude attribute is quite different from the stratum thickness, probably because the overall amplitude of the seismic reflection layer here is strong. SQ1 sequence thickness is mainly between 15 and 45 m. The inversion results of the GGK and VSH sand bodies in SQ1 are quite different, which may be related to the overall high-density value of this section, and its GGK curve baseline is higher than that of the J5-6 mudstone section. SQ2-2: The average amplitude attribute shows that SQ2-2 has a strong amplitude in the north and southeast of the study area. The stratigraphic thickness map shows that the SQ2-2 sequence is thick in the east of the study area, and the sand body inversion results of SQ2-2 show that the sequence sandstone is well developed in the south and middle of the study area. SQ3-1: The average amplitude attribute is consistent with the inversion thickness of the stratum and sand body and stratum thickness. The stratigraphic thickness map shows that the SQ3-1 sequence is thick in the north-central part of the study area.