关键词: 铀, 地球化学, 油气藏预测, 盖层, 断层, 封闭性, 评价

Abstract: Relations between the enrichment of Uranium and the migration of hydrocarbon in sedimentary basins were discussed in thispaper.A dish-like anomaly model of Uranium migration and enrichment in the overlying rocks of reservoir was also explored.Insedimentary rocks the migration and enrichment of Uranium are caused by transformation between U⁴⁺ and [UO₂]²⁺.U⁴⁺ is oxidized to [UO₂]²⁺ for migration in oxidizing environments,while[UO₂]²⁺ is reduced to U⁴⁺ for precipitation in reducing environments.Organic matter and generated oil gas are common reductants in sedimentary basins,and the movements of hydrocarbonare major factors controlling the migration and enrichment of Uranium.Vertical movements and dissipation of hydrocarbon resultin obvious enrichment of Uranium along hydrocarbon leaking passages and also in overlying rocks of reservoir.Therefore characteristics of Uranium migration and enrichment can be used to determine distributions of deep reservoirs and hydrocarbon dissipation passages.This method can also be effectively used to evaluate sealing abilities of cap rocks and faults in addition to forecastoccurrences of different reservoir traps.Due to its radioactivity,Uranium content can be easily measured in fields by gamma-rayspectrometer.This is a new useful method for oil gas exploration.

Key words: Uranium, forecasting of oil & gas reservoir, caprock, fault, seal ability, evaluation