## 5 Sequence Development Model and Deposition Evolution
### Reservoir Properties and Prediction Discussion  
Based on the analysis of the sequence stratigraphic characteristics, the establishment of a sequence development model and the discussion of a sequence stratigraphic sedimentary process, combined with the characteristics of seismic reflection, it is found that during the period of the upper high system tract of the fourth member of the Shahejie Formation in the B structural belt, the fan delta in the area received the supply of the eastern source. At this time, the salt rock activity did not affect the formation development. The salt structure pierced the stratum, which blocked the salt rock in the east side of the salt uplift, thickened the lithologic sand body to the east, and over-pinched out in the west. The overall distribution was fan-shaped, and the mudstone-salt rock cap rock combination was formed in the contact area between the fan delta front and the salt lake (Figure 17a). The volcanic  
Figure 16: Steep-slope–gentle slope differential contrast sequence stratigraphic model.  
activity in the lower part of the fourth member of the D structural belt caused the uplift of the southern gentle slope to form a good volcanic rock block. During the period of the low-stand system tract in the upper sub-member of the fourth member, the braided river delta was formed due to the influence of the western provenance. The lithologic sand bodies were accumulated in the east, and the lithologic bodies were superimposed in a large range in the longitudinal direction. The braided river delta front and the shallow lake mudstone were deposited alternately, forming a good reservoir-cap combination (Figure 17b). The salt rock did not pierce the strata when the fan deltas of the upper high system tract and the low system tract of the fourth member of the Shahejie Formation (Figure 17c) and the lower high system tract and the low system tract of the fourth member of the Shahejie Formation (Figure 17d) in the E structural belt were developed. Its development was affected by the supply of the eastern provenance and the southern provenance at the same time. The later salt rock activity caused the salt rock to pierce the strata and form a salt dome to block and seal, the lithologic sand body was wedged downward and pinched out to the west, and the upper part of the sand body was covered by mudstone. The sand body and the lacustrine mudstone and salt rock form a good source-reservoir-cap configuration. The three structural belts all developed and formed a favorable lithology body, which is expected to achieve better oil and gas discovery.  
Figure 17: Favorable trap seismic profile and plane distribution map: (**a**) B structural belt favorable lithology and plane distribution; (**b**) Structural belt favorable lithology and plane distribution; (**c**) the upper high system tract and the low system tract of the fourth member of the Shahejie Formation of E structural belt favorable lithology and plane distribution; (**d**) the lower high system tract and the low system tract of the fourth member of the Shahejie Formation of E structural belt favorable lithology and plane distribution.