Abstract:  In recent years, Mesozoic magmatic rock has been found in many offshore petroleum-bearing basins in China, and it is widely distributed, such as the Bohai Bay basin, the East China Sea basin, the Pearl River Mouth basin, and the Qiongdongnan basin. Petrological, geochemical and reservoir research of Mesozoic magmatic rock in these basins are not only of theoretical significance for the formation and evolution of the basement of basins, but also of practical value for oil and gas exploration in magmatic buried hills. This paper systematically compares the characteristics of Mesozoic magmatic rock and the types of oil and gas reservoirs in the typical basins of the Bohai Bay basin, the Pearl River Mouth basin, and the East China Sea basin using petrological, geochemical, and petroleum geological data. Research has shown that the Mesozoic magmatic rock in China’s offshore petroleum-bearing basins consists of two major categories of volcanic and intrusive rocks with more than 20 types of lithologies. There are different volcanic rocks from basic to acid in the Bohai Bay basin, and a lack of basic volcanic rocks in other basins. They developed mainly in three stages: Late Jurassic, Early Cretaceous, and Late Cretaceous. Controlled by the subduction of the Paleo-Pacific plate and subsequent back-arc rifting, the offshore basins underwent differential tectonic evolutions under a transition environment from a compression in the Jurassic to an extension in the Cretaceous. The East China Sea basin and the Bohai Bay basin underwent back-arc rifting, and the Pearl River Mouth basin was an offshore magmatic arc. There are three types of reservoirs, namely, granitic weathered crusts, igneous complex, and intermediate-acidic volcanic rocks. Favorable lithological facies, intense tectonic and weathering modification, and strong dissolution are the keys to the reservoir formation of magmatic rocks for buried hills.

Key words: offshore petroleum-bearing basins, Mesozoic, magmatic rock, magmatic reservoir, buried hills, Bohai Bay basin, East China Sea basin, Pearl River Mouth basin