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针对陆相碎屑岩特超低渗储层油气运聚成藏研究中存在的问题,选择鄂尔多斯盆地西部延长组下组合砂岩油藏储层为研究对象,分析其沉积结构构造、成岩作用与致密化过程的非均质性,认识储集空间的非均质性分布规律与石油充注特征。研究发现,河湖相特超低渗含油储层表现出较强的非均质性,含油砂岩与不含油砂岩交互成层,其中不含油砂岩可分为3类:钙质砂岩、富软颗粒砂岩和含水砂岩。其成岩过程迥然,其中钙质砂岩和富软颗粒砂岩的发育多与中—低级构型界面有关。含油砂岩中可识别出3期沥青,分别对应于晚侏罗世、早白垩世中期、早白垩世晚期的石油充注。以这些沥青为时间标志可将含油砂岩中的成岩过程划分为3期,并在含水砂岩中识别出对应的3期成岩过程。在钙质胶结和富软颗粒致密砂岩中,成岩作用主要发生在第1充注之前,其构成了储层内的隔夹层,并且往往形成不同层次、不完全封隔的似网状结构,影响甚至控制了后期的流体活动,引起后期成岩作用和油气充注过程的非均匀性。在储层非均质性及沉积构造分析、成岩过程及其与油气充注关系研究、古物性恢复的基础上,提出了结构非均质性特超低渗砂岩油藏成藏模式。
Aiming at the existing problems in the study of hydrocarbon migration and accumulation in terrestrial clastic ultra-low permeability reservoirs, we selected the reservoir of the lower combined sandstone reservoir in the Yanchang Formation in the western Ordos Basin as the research object, and analyzed its sedimentary structure, diagenesis and compactness Heterogeneity of the process, knowledge of the heterogeneity of reservoir space and oil charging characteristics. The results show that the ultra-low permeability oil-bearing reservoirs in the facies of the rivers and lakes show strong heterogeneity. The oil-bearing sandstone and the oil-free sandstone interact with each other. There are three types of oil-free sandstone: calcareous sandstone, Sandstone and watery sandstone. The process of diagenesis is quite different. Among them, the development of calcareous sandstone and soft-rich sandstone are mostly related to the medium-low configuration interface. Three phases of bitumen can be identified in the oil-bearing sandstone, corresponding to petroleum charge in Late Jurassic, Early Cretaceous and Early Early Cretaceous, respectively. Using these bitumen as a time marker, the diagenetic processes in oil-bearing sandstones can be divided into three stages and the corresponding three-stage diagenetic processes were identified in the water-bearing sandstones. In the calcareous cementation and the soft-rich sandstone, the diagenesis mainly occurred before the first charge, which formed the intercalated layers in the reservoirs and often formed different layers of network-like structures that were not completely isolated and influenced Even control the fluid activities in the later period, causing the late diagenesis and non-uniformity of hydrocarbon filling process. Based on the analysis of reservoir heterogeneity and sedimentary structure, diagenesis process and its relationship with hydrocarbon filling and the restoration of antiquarian property, a reservoir forming model of structurally heterogeneous ultra-low permeability sandstone reservoir is proposed.