Organic geochemistry of Longli-Kaili oil seepages on the east margin of the Central Guizhou Uplift

Abstract：Massive Paleozoic-Mesozoic oil-seepages occur in the east Guizhou uplift. In this paper, crude oil samples were analyzed by GC, GC-MS and IRMS, with a discussion on their organic geochemistry and the oil-source correlation. The results show that all of the crude oils are maturate and influenced by multi-uplift tectonic activities. The crude oils from Lower Triassic Daye Formation originated from oil shale in this formation and are different from Paleozoic oil-seepages in biomarkers, family composition and free carbon isotopic composition. The crude oils from Middle Permian Maokou Formation is genetically related to Lower Permian Qixia Formation, the crude oils from Lower Ordovician Honghuayuan Formation originated from shale section of Middle Silurian Wengxiangqun Formation and Lower Cambrian Niutitang Formation, and the shale member of Middle Silurian Wengxiangqun Formation is the product of late hydrocarbon generation, suggesting the probable existence of a set of special oil-bearing compositions. These data are of positive significance for petroleum prospecting in this area.