柴达木盆地北缘地区油气运聚特征

Features of hydrocarbon migration and accumulation in the northern marginal zone of Chaidamu Basin

从可溶有机质饱和烃色谱、甾烷、萜烷生物标志物和天然气碳同位素等分析资料看,柴北缘目前已发现的油气与该区侏罗系中、下统烃源岩具有很好的可比性,且柴北缘不同地区的原油来自于区内侏罗系烃源岩的不同层段,运移距离也有差异。活动性断层、不整合面、可渗透性地层为柴北缘主要的油气运移通道。根据该区有机包裹体的均一化温度测试结果,确定柴北缘地区油气大量运移时期应在E3—N1、N2。通过盆地模拟法,分别计算了该区主要输导层路乐河组、下油砂山组地层流体势(油、气、水势)。根据现今路乐河组和上、下油砂山组地层流体势和构造格局将柴北缘划分为鄂博梁—鸭湖、冷湖、南八仙—马海、平台、鱼卡等5个运聚单元。

From the analysis of the saturated hydrocarbon chromatogram of soluble organic matter,the biologic markers of gonane and terpane,and the carbon isotopes of the natural gas, the new discovered hydrocarbon showing in the northern marginal zone of Chaidamu Basin has some comparability with Middle-Low Jurassic source rocks in the same region.The crude oil of different zones in the northern marginal zone of Chaidamu Basin comes from different Jurassic source rock layers in the same region and the migration distances are different.The major hydrocarbon migration pathways in the northern marginal zone of Chaidamu Basin are active faults,unconformable surfaces and permeable formations.According to the homogenization temperature test results of the organic enclosures of this region,it is decided that most of the hydrocarbon migration in the northern marginal zone of Chaidamu Basin had taken place in the periods of E_3-N_1 and N_2.Through the simulation of formation pressure with the basin simulation method, the fluid (oil,water and gas) potential of the main transmission formations (Lulehe and lower Youshasan formations),is calculated.According to the current formation potential and the structural framework of Lulehe formation, and upper and lower Youshasan formations,the northern marginal zone of Chaidamu Basin is divided into five migration and accumulation units:Eboliang-yahu,Lenghu,Nanbaxian,Pingtai and Yuka.