试论古水动力演化的旋回性与油气的多期次运聚

水动力已经成为盆地分析和油气勘探中的重要内容。由于油气的运聚与成藏作用都是发生于地质历史时期的特定历史事件,要准确分析流体运移特征,就必须首先了解古水动力的演化历史。将压实曲线分析、盆地数值模拟以及流体包裹体测试等方法相结合,可以获得古水动力演化的概况。通过对我国中西部鄂尔多斯、吐哈、准噶尔等含油气盆地的古水动力恢复和研究发现,受盆地后期改造强烈的宏观背景影响,古水动力场的发育和演化往往具有旋回性,具体表现为地层过剩压力幅度随时间的演化呈两个以上增-减-增的序列,流体势平面分布在不同地质时期的演化具有明显差异。由此形成流体在水动力背景下运移、聚集和成藏的多期次特点,具体表现为多期次的排烃作用、油气二次运移聚集的阶段性以及古、今油气藏分布上的差异性。

A View on Cycles of Paleo-Hydrodynamics Evolution andPhases of Hydrocarbon Migration and Accumulation

The hydrodynamics has been an important content in basin analysis and petroleum exploration. Before the characteristics of fluid migration and accumulation being studied, evolution history of paleo-hydrodynamics must be restored first of all, because of being as specific history events set in geologically history periods. The outline of paleo-hydrodynamics evolution could be obtained by means of integrating methods of compaction curves analysis, basin numerical modelling and fluid enclosure determining. It is discovered that the development and evolution of paleo-hydrodynamics are of cycles, on the background of cycling evolution of basins, by way of restoring and investigating paleo-hydrodynamics in NW China petroliferous basins. The hydrodynamic cycle is charactertic ot evolution of overpressure along with times composed of two or more circulations from increasing to decreasing, and plane distribution of fluid potentials being of several stages in different geologic periods. So the characteristics of fluid migration, accumulation and pool forming lying on hydrodynamic environments are formed, such as multi-phase of main expulsion, stages of hydrocarbon secondary migration and accumulation, divergence of reservoir distribution between geologic periods and present .