# Analysis of Hydrocarbon Enrichment in Tight Sandstone Reservoirs in the Eastern Baiyun Depression
## 4 Basic Characteristics of Paleogene Reservoir Formation Elements in the Eastern Baiyun Depression
### The Target of WXD-7 Region
#### 5.3.2 Hydrocarbon Accumulation Model  
The structural target of the WXD-7 region is located at the west margin of the eastern low bulge. The main strata studied in this study are the sedimentary strata of Member 4 and Member 5 of the Wenchang Formation, which belong to the stratigraphic trap type. The water depth is about 680-1210 m, and the peak depth is about 3950 m. LGH-8 well drilling reveals that the source rock of the Wenchang Formation has good oil generation potential. Therefore, according to the comprehensive study, the main source rocks of the WXD-7 region structural target come from the east wing of the Baiyun main depression and LGH-2 Depression (WC-EP), among which, the trap area of the Wen4 Formation and the Wen5 formation in this study is about 44 km\({}^{2}\) and 52 km\({}^{2}\), respectively.  
The hydrocarbon accumulation model of the WXD-7 region structure target is mainly a source-sand near-source accumulation model, and the east wing of the main depression mainly provides source rock, that is, hydrocarbon supply in the eastern wing of the main depression (Figure 10). The target of the WXD-7 region is the lateral transport system of the sand body, and the typical self-reservoir cap combination is developed. The well-developed reservoir sandstone of the Wenchang Formation also develops a good cover layer of sand-mud interlayer, showing a self-generation and self-storage model. In the development period of the Wenchang Formation, especially in the fourth and fifth members of the Wenchang Formation, relatively high-quality reservoirs, namely, delta sandstone, were developed. At the same time, the thick mudstone developed in the Zhuhai Formation is a good sealing cap layer, which is conducive to the formation of a high-quality reservoir cap combination. In the migration path, the structural target belongs to the dominant migration type of near-source slope, the delta sand body and the source rock can be finger-like contact, the oil and gas belong to near-source migration, and the oil and gas migration efficiency is high. Therefore, based on the analysis of various factors, it is concluded that the target of the WXD-7 region structure develops a large-scale delta system, the combination conditions of the source reservoir and cap are superior, and the structure is located on the favorable path of oil and gas migration and accumulation, which is conducive to the large-scale accumulation of reservoirs, but there are certain exploration risks in terms of reservoir physical properties and trap conditions.  
According to current geological research in the eastern region of the Baiyun Depression, the combination of overpressure systems, favorable reservoirs and basement structures controls the favorable areas for oil and gas. The periphery of large nose-shaped uplifts, shallow burial depths and relatively low geothermal gradients provide favorable conditions for the development of large-scale stratigraphic overlap and ancient buried hill composite enclosures, with favorable reservoir formation conditions, trap boundary conditions and high-quality large-scale reservoirs being the main controlling factors. Due to the influence of diagenesis, the physical properties of the middle and deep reservoirs are generally poor, while the thick and coarse-grained sandstone in the high-energy phase zone still has the conditions for developing good physical reservoirs under larger burial depths, which is also the target we are looking for.