关键词: 古油藏, 地球化学, 流体包裹体, 裂变径迹, (U-Th)/He, 海相油气, 中扬子

Abstract:

Field investigation, organic geochemistry, fluid inclusion and low temperature thermochronology analysis were carried out for further understanding characteristic, formation and destroy process of the Permian paleo-oil seepage in Jingshan area, the north edge of the central Yangtze block. The Permian source rock with high organic abundance and type I organic matter is considered to be the best source rock. The hydrocarbon are mainly preserved in hole, crack or crack-hole, show olivine or brown yellow color, are easy-volatizing light oil, and are expulsed from the Permian source rock. The preservation conditions may be the key factor for the paleooil seepage. Based on fluid inclusion analysis and basin modeling, Permian hydrocarbon source rock started to generate oil during the Early Triassic, there must exist one or more thermal fluid activities which were related to petroleum migration or redistribution in the Late Triassic-Late Jurassic. By low temperature thermochronology analysis, the reservoir experienced three stages of tectonic movement after its formation: 1)Strong uplift and rapid cooling during Jurassic-Early Cretaceous stage; 2)Slow uplift stage during the Late Cretaceous-Early Paleogene； 3)Strong uplift and cooling since the Middle Paleogene, and the first event applies the greatest impaction on the reservoir and maybe even destroy it. Through the paleo-oil seepage analysis, the central Yangtze region may be gets primary oil or gas reservoirs reserved in cracks or/and hole developed within Permian strata, especially where the Yanshanian tectonic influence is weak.

Key words: paleo-oil reservoir, geochemistry, fluid inclusion, fission track, (U-Th)/He, marine petroleum, Middle Yangtze block