关键词: 火山物质识别, 元素面扫描, 碎屑锆石, 年代学, 储层, 油气地质, 古近系, 珠一坳陷

Abstract:  The focus of exploration gradually shifted from shallow to deep Paleogene strata in Zhu Ⅰ depression, the Pearl River Mouth basin. Volcanic materials are widely developed in Paleogene strata, which is one of the important factors affecting the physical properties of deep clastic rock reservoirs. This study comprehensively utilizes methods such as thin section, element surface scanning, morphological characteristics and U-Pb dating of detrital zircons, combined with the volcanic background of the study area, to study the volcanic materials properties of the Paleogene detrital reservoirs in the Zhu Ⅰ depression. The results showed that the Paleogene in the study area mainly developed acidic, intermediate, and basic volcanic materials. Acidic volcanic materials often have a high mass fraction of Si, rich in Al and K. The alteration products are mainly clay minerals such as kaolinite and illite, and their formation is related to acidic magma eruptions. They are often associated with acidic volcanic rock fragments such as rhyolite and can be identified as synsedimentary volcanic zircons, mainly distributed in the Lufeng sag. The intermediate volcanic materials have a moderate Si mass fraction and are relatively rich in potassium. The main alteration product is authigenic quartz, often associated with intermediate volcanic rock fragments such as andesite. It is distributed in Enping sag, eastern Yangjiang sag, and Lufeng sag. The basic volcanic materials have extremely low Si mass fraction and is rich in Fe and Mg. The alteration products are mainly mafic clay minerals and zeolite, mainly distributed in the Huizhou sag, with a small amount distributed in the Xijiang sag. In addition, a small amount of alkaline volcanic materials is locally developed in the Lufeng sag 13 structural belt of the study area, which is mainly distinguished by the alteration product being apatite. Low porosity and low permeability are commonly observed in tuffaceous reservoirs, but under specific diagenetic conditions, the locally developed small amount of volcanic materials and the dissolution properties of volcanic materials can play a role in increasing and preserving pores, which has a certain improvement significance for later petroleum charging.

Key words: volcanic material identification, element surface scanning, detrital zircon, chronology, reservoir, petroleum geology, Paleogene, Zhu Ⅰ depression