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通过对产在自生胶结物中的水溶液包裹体和石油包裹体的分析,研究了乌拉油田的成岩史和石油充填史。研究结果表明,虽然对反应速率和石油饱和程度仍然知之不多,但在石油到达砂岩之后,成岩作用仍持续活跃。自生石英中包裹体的显微测温证实,石英胶结作用开始广泛发生的温度在110℃左右(相对埋深2.5km),且这一过程延续至今。与此同时,自生钠长石亦以粒间和粒内胶结物的形式存在。大量的石油包裹体主要产于钠长石和石英胶结物中,其胶结物捕集的包裹体可作为该构造中到达的石油的主要载体。通过石油和矿物表面间的薄水层的扩散作用,可能以自生石英和自生钠长石沉淀的溶质质量传递为主。早期形成的钾长石次生增长体中石油包裹体的分析表明,在最近25Ma快速沉降之前,有些二次运移的石油可能到达了浅埋深的储层中。与乌拉组储层孔隙游离石油相比,钾长石包裹体中的石油显然来自不同的生油相。测试的大多数成熟度参数表明,后者的成熟度较低。后期石英和钠长石捕集的石油包裹体,同样具有钾长石和乌拉组储层中DST原油的某些特征。因此,这些特征可能反映了在石英成岩作用过程中,乌拉油田石油的聚集是渐进变化的。
Through the analysis of the fluid inclusions and petroleum inclusions in the authigenic cements, the diagenesis and oil filling history of the Wula oilfield are studied. The results show that although the rate of reaction and the degree of oil saturation are still poorly understood, the diagenesis has continued to be active after the oil reached the sandstone. The microscopic temperature measurement of inclusions in authigenic quartz confirmed that the temperature at which quartz cementation begins to occur is about 110 ℃ (relative depth 2.5km), and the process continues to this day. At the same time, self-born albite also exists in the form of intergranular and intragranular cement. A large number of petroleum inclusions are mainly produced in albite and quartz cements, and the cement-entrapped inclusions can serve as the main carrier for the petroleum arriving in this formation. Through the diffusion of thin layers of water between the surface of oil and minerals, the mass transfer of solute may be dominated by precipitated quartz and authigenic albite. The analysis of petroleum inclusions in the early formation of K-feldspar secondary growth suggests that some secondary migration of oil may have reached shallow-depth reservoirs before the rapid subsidence of 25 Ma. The oil in the K-feldspar inclusions apparently comes from different raw oil phases compared to the pore-free petroleum in the Wula Formation. Most of the maturity parameters tested indicate that the latter are less mature. Later petroleum inclusions captured by quartz and albite also have some of the characteristics of DST crude oil in potash feldspar and Wula Formation reservoirs. Therefore, these characteristics may reflect the gradual change of oil accumulation in the Wula field during quartz diagenesis.