# Analysis of Hydrocarbon Enrichment in Tight Sandstone Reservoirs in the Eastern Baiyun Depression
## 1 Introduction  
Because of the increasing difficulty of oil and gas discovery, structure-lithology and stratigraphic lithology reservoirs are very important in exploration in deep-water and deep-formation conditions [1; 2]. At present, many large and medium-sized oil and gas fields composed of lithologic and structural hydrocarbon reservoirs have been discovered in China, especially in the Baiyun Depression [3]. The Baiyun Depression is a hydrocarbon-rich depression with good formation conditions for middle-deep lithology/stratigraphic traps and great resources and development potential [4; 5]. However, it is still faced with relatively single reservoir locations, mainly small oil and gas fields, and the diagenesis of the middle-deep reservoir is affected by other factors [6]. Therefore, further research should be carried out. The upper member of the Enping Formation in the north slope of the Baiyun Depression is a large delta with continuous progradation, which belongs to the progradation reflection structure, and the source is mainly from the NW direction. The Baiyundong area has obvious mid-depression uplift landforms, and provenance analysis is difficult and needs to be combined with paleogeography analysis, heavy minerals, debris components, seismic facies and seismic sedimentology analysis techniques. There are typical differences in the relationship between sedimentary facies types and the spatial allocation of sedimentary bodies in the two regions in different sedimentary periods. Inaddition, several different types of source-sink systems are developed in the study area, and there are essential differences among them. The exploration of the Baiyun Depression can be divided into three stages. The first stage is 1979-2001, which is the initial study and exploration stage. During this stage, the major targets were the large structural traps in the Panyu uplift and Dongsha uplift, but no industrial discoveries were made. The second stage is 2001-2015. After the failure in the uplifts, we turned to the northern and eastern slopes near the hydrocarbon generation centers. In the northern slope, breakthroughs were made in the lower Miocene by drilling the structural traps controlled by antithetic normal faults, which also showed bright spot characters and several important gas fields were found. In the uplift area between the eastern center and the Yunli Uplift, middle-large gas fields were discovered in deep-water fans and shelf-edge deltas from structural and lithological traps, including the first large deepwater gas field, Liwan 3-1. In the northeastern slope, three important oilfields with light crude oil were also found in this stage. During this peak period, the most important medium-shallower traps were drilled. So, after that, we turned to new areas, such as the west and southwest, new layers, such as middle-deep layers, and new trap types, such as stratigraphic-lithology traps. Many wells were drilled, with no significant discoveries. Several wells targeted in the middle-deep layers of the Paleogene also failed due to high temperature, high compaction, uncertainties in the traps and accumulation. The exploration of the Paleogene is still faced with several problems, such as the fact that there are relatively few reservoir locations, mainly small oil and gas fields, and the diagenesis of the middle-deep reservoir is affected by other factors [6]. In the Baiyun Depression, relatively few wells have been drilled into the target layer, the burial depth is generally large, and the reservoir diagenesis has undergone a long history of diagenesis. The diagenesis of the reservoir is affected by various geological processes. The difficulties in analyzing and characterizing the structural and stratigraphic lithologic traps are as follows: the thickness of the target sand body is often less than the vertical resolution of the seismic layer, and the boundary of the seismic reflection abnormal body is often fuzzy.