塔里木盆地非稳态油藏特征与形成机制

塔里木叠合盆地地质演化历史漫长，经历了多期次的构造沉降、隆升和多期次油气成藏与调整过程，形成了多种类型的油气藏。通过系统研究海相油藏的地质特征，发现一些油藏的油水界面呈现不平衡性、油气物理化学性质和含油饱和度等平面分布具有渐变性、油藏主体与圈闭中心具有非协调性，反映出这类油藏可能正处于动态聚集或调整过程中，进而提出非稳态油藏的概念。非稳态油藏的形成是由于地质构造的变动、储层非均质性或其他因素，导致油藏的稳定滞后于圈闭的调整，致使油藏尚未形成统一的油水界面。按照其形成机制、形成过程以及油水界面类型、成藏模式等，对非稳态油藏进行了分类。提出非稳态油藏的研究以动静态相结合的地质解剖为主，综合运用地质与地球化学手段，结合物理模拟和数值模拟，定量评价古今油水界面的迁移和变化，精细恢复圈闭的演化过程，再现非稳态油藏的形成过程，可实现对非稳态油藏分布的有效预测。

Characters and formation mechanism of unsteady reservoirs in Tarim Basin

The superimposed Tarim Basin has experienced a long evolutionary history, including multi-stage subsidence, uplift, hydrocarbon-accumulation and adjustment processes, thus, a variety of reservoir types with complex gas-water contact were formed. By systematically summarizing geological features of oil-gas reservoirs in the basin, we discovered that some of the oil reservoirs are characterized by imbalance of oil-water contact(OWC), gradational changes in the plane distribution of physicochemical properties and oil saturation, and discordant locations of the major reservoir body and trap center, indicating a dynamic aggregation or adjustment process that these reservoirs are currently experiencing, consequently a concept of ‘unsteady reservoir’ was proposed. An unsteady reservoir is formed under rapidly tectonic movement, during which the reservoir heterogeneity or other factors may result in the stabilization of the reservoir lagging behind the trap’s adjustment and the uniform oil-water contact uncompleted. We classified unsteady reservoirs according to the formation mechanism, formation process, types of oil-water contact and accumulation patterns. It was proposed that the study of unsteady reservoirs should focus on integrating static and dynamic geological dissections, synthetically applying geological and geochemical methods, combining physical modeling with numerical simulation, quantitatively assessing paleo- and present-OWC migration and variation, and precisely restoring the evolutionary process of traps so as to reproduce the formation process of unsteady reservoirs and effectively predict their distribution.