黔中隆起东部龙里—凯里地区油苗有机地球化学特征及其成因分析

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

黔中隆起东部发现有大量的中—古生界油苗。应用色谱、色谱-质谱及同位素等测试技术,系统地研究了油苗的地球化学特征及油源。结果表明,受黔中多期次构造抬升活动的影响油苗的热演化程度均处于成熟阶段;大冶组(T1d)原油的生物标志物、族组分及单体烃碳同位素组成与古生界油苗存在明显差异,其烃源岩为研究区西南部的T1d油页岩;茅口组(P2m)原油为单源供烃,与栖霞组(P1q)烃源岩具亲缘关系;红花园组(O1h)原油具混源特征,主要来源于下寒武统牛蹄唐组,同时受翁项群组(S2w)泥质岩段的影响。其中,S2w泥质岩段具晚期生烃的特征,预示着研究区下古生界存在一套特殊的含油气组合,这对评价该地区的油气前景具积极意义。

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 SilurianWengxiangqun Formation is the product of late hydrocarbon generation, suggesting the probable existence of a set of special oilbearing compositions. These data are of positive significance for petroleum prospecting in this area.