# Analysis of Hydrocarbon Enrichment in Tight Sandstone Reservoirs in the Eastern Baiyun Depression
## 3 Structure and Multiple Reconstruction Characteristics of Eastern Baiyun Depression
### Multiple Transformation Characteristics of \"Extension-Detachment-Differential Magma Penetration\"
#### 3.2.2 Differential Magma Penetration  
The widely developed volcanic activities in and around the South China Sea have recorded important information about the evolution of the South China Sea and related deep dynamic processes, and the study of igneous rocks is of great significance for understanding the mantle evolution, crust-mantle interaction, seafloor spreading and the formation of the deep-sea basin in the South China Sea [38]. Since the late Cenozoic, the passive continental margin of the South China Sea has experienced frequent and intense magmatic activity due to the superimposed effects of various factors. According to the detailed interpretation of drilling data and 3D seismic data, the magma floor invasion occurred in different degrees during T83-T70 in the eastern Baiyun Depression. Subsequently, the magma eruption mainly developed the overflow phase of volcanic eruption during the South China Sea movement, and the development period was relatively concentrated. The magma of volcanic eruption effusive facies mainly presents the form of a zonal distribution in the Baiyun depression, and the occurrence of effusive facies magma in different regions has certain similarities, but the development times, profile characteristics and development forms are different to some extent. The strata lifted upward, thinned down and contained more upper super cusps in the interior, forming a mantle structure, which reflected the syn-sedimentary nature of volcanic activity. If the formation caused by volcanic magma or volcanic activity rises above the surface and is  
Figure 3: Typical seismic profile characteristics of the two-stage separation system in eastern Baiyun. The solid red lines represent the interpreted faults. The red dotted lines represent possible faults. Red arrows indicate the position and direction of the profile line. exposed upon the lake's surface, it provides a source to the surrounding area and can form a certain prograde reflection structure, indicating the direction of the source. Because the Baiyun depression is located in the crustal thinning zone, magma intrudes into the strata from the mantle or erupts to the surface and then condenses into igneous rocks. This study shows that the volcanic rocks' development age is related to the crust and mantle equalization, the northward migration of the shelf slope line, the strong subsidence during the depression, and the southward transition of the south ocean mid-ridge. In the early stage, it was mainly a high-angle fault depression, and, in the later stage, the strata were uplifted and separated into low-angle fault depositional centers and migrated to the main Baiyun depression. The main period of Paleogene magmatic floor encroachment in eastern Baiyun is T83-T70 (Figure 4). Relatively speaking, the development age of extrusive magma is mainly concentrated in the period from 23.8 Ma to 17.5 Ma, while the magma that developed before and after 18.5 Ma developed in a large range in the three main areas of the Baiyun depression, showing a near east-west distribution in space. Under the influence of magmatic floor invasion, magmatic activity is frequent, and the strata of T80 and below show obvious deformation characteristics. Among them, the magma floor invasion is the most intense in the LGH-2 well area, and the accommodating space and formation thickness in the area with strong magma floor invasion are small. In contrast, other regions with weak magma floor invasion have larger space and thickness. Figure 4: Different characteristic profiles of magmatic floor encroachment at different structural locations in the eastern Baiyun Depression. (**A**) Northwest-Southeast direction structural seismic profile of the eastern Baiyun Depression. The solid red lines represent the interpreted faults. The red dotted lines represent possible faults. Red arrows indicate the position and direction of the profile line. (**B**) West-East direction structural seismic profile of the eastern Baiyun Depression. The solid red lines represent the interpreted faults.