Petroleum sporo-pollen assemblages and petroleum source rocks

Abstract

Based on the investigations of sporo-pollen assemblages in individual petroleum reservoir beds, it is possible to predict the petroleum source rocks. Such investigation is applied to the basins in China selected for study. In the Tarim Basin, Triassic and Jurassic sequences should be the main petroleum source rocks, while Carboniferous sequences should have been the source of some petroleum, and the Permian and Cretaceous sequences might contain petroleum source rocks. Ten formations or groups are identifiable for the North Tarim petroliferous region, four formations for the Kuqa Depression, and three for the Kashi and Yecheng Sags. In the East Junggar Depression, four Permian formations are identified as the main source rocks, while five Triassic formations are secondary in importance. Carboniferous and Jurassic rocks also have some potential. In the South Junggar Depression, four Jurassic formations and one Oligocene formation should be the main source rocks. In the Qiktim oil field, only a Jurassic monotype sporo-pollen assemblage is found. In the Turpan Depression of the Turpan-Hami Basin, four Jurassic formations are implicated. In the Qaidam Basin, two Jurassic formations are implicated in the North Border Block-fault Zone. In the Mangnai Depression, Paleocene to Eocene and Oligocene to Miocene formations are identified as the main petroleum source rocks. In the West Jiuquan Basin, the black shales of the Lower Cretaceous Lower Xinminbu Formation should be the petroleum source rocks. In the Liaohe Basin, two Oligocene formations are implicated. In the Beibu Gulf Depression of the western North Shelf of South China Sea, Eocene and Oligocene formations are predicted as the source rocks. In the Zhujiang Mouth Depression of the eastern North Shelf of South China Sea, three formations of Eocene and Oligocene ages are implicated.