Abstract: To definite the characteristics of mid-deep paleogene sandstone reservoirs and the controlling effect of dissolution on high-quality reservoirs in Baiyun Sag, Pearl River Mouth Basin, South China Sea, according to the core observation, casting slice, field emission scanning electron microscopy and observation results, the lithological characteristics, reservoir space characteristics and physical characteristics of Paleogene sandstone reservoirs in Baiyun Sag were described in combination with X-ray diffraction, mercury penetration analysis and other data and technical means. In addition, a deep study was conducted on the diagenesis related to reservoir physical properties and reservoir quality. As found in the results, the reservoir sandstones in the East Sub-sag of Baiyun Sag are mainly composed of feldspathic quartz sandstone and lithic quartz sandstone. The lithology of the North Slope of Baiyun Sag is more complex than that of the East Sub-sag, primarily composed of feldspathic quartz sandstone, with a small amount of feldspathic lithic quartz sandstone. The pores of the mid-deep reservoirs in the East Sub-sag include intergranular and intragranular dissolved pores. The pore development degree of reservoirs in the North Slope is slightly higher than that of the East Sub-sag, with a higher content of intergranular dissolved pores, intragranular dissolved pores and mold pores. The reservoirs in Baiyun Sag are generally characterized by low porosity and permeability. The dissolved pore formed by the interaction of organic acids with feldspar and igneous rock debris is the most important factor that controls the physical properties of the Paleozoic sandstone reservoir in the study area. The study results can become certain reference and guidance for the exploration and development of sandstone reservoirs in Baiyun Sag, Pearl River Mouth Basin.

Key words: Paleogene, sandstone, reservoir characteristics, dissolution, mid-deep layer, Baiyun Sag, Pearl River Mouth Basin