山东东营凹陷砂岩中NaCl-CaCl_2-H_2O体系包裹体的发现及其意义

The occurrence of NaCl-CaCl_2-H_2O system fluid inclusions in sandstones of the Dongying depression,Shandong,and the significance

油田水的成分和变化是含油气盆地演化历史的重要部分.由于油田水的取样十分困难且数据有限很难进行系统分析,本文通过包裹体显微测温学与油田水采样的结果相结合的方法,对东营牛庄洼陷中油田水的成分进行了研究.砂岩中穿插石英颗粒的最后一期包裹体,记录了最晚期的油田水成分.对最晚期的流体包裹体的显微测温学结果表明,晚期流体包裹体主要为NaCl-CaCl2-H2O体系,这与相同或者相近深度油井油田水采样的成分基本一致,证明了该方法的有效性.这种方法便捷、有效,有着良好发展前景.

The evolution and geochemistry of oil-field water are very important to understand the geologic history of an oil gas basin. However, since difficulty in sampling oil-field water, the compositions of oil-field water have poorly been known so far. In this study, we use fluid inclusions crossing quartz grains in sandstones to determine the compositions of oil-field water in the Dongying depression, Shandong province, eastern China. The secondary fluid inclusions crossing quartz grains in sandstones can record the oil-field water at the last time during the burial history. Our results based on microthermometry methods show that some secondary fluid inclusions record a NaCl^- CaCl2- H2O system according to abnormal low temperature phase transition, and are consistent with the results obtained from the CaCl2 type oil-field water samples collected at the nearly same depths. However, there are data that indicate that some secondary fluid inclusions are not a NaCI--CaCl2- H2O system, which are consistent with the results of the NaHCO3 typeoil-field water samples collected at the nearly same depths. Our results indicate that the secondary fluid inclusions in quartz grains can well record the compositions of oil-field water, and the microthermometry method is very useful and quick to judge the types of oil-field water.