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浅水三角洲储集层在陆相湖盆油气勘探中具有重要的意义,但基于密井网资料的精细研究仍十分缺乏。以高分辨率层序地层学和沉积学理论为指导,以松辽盆地扶余油田DT91区块白垩系泉头组四段第Ⅲ砂组14余口取心井的岩心资料和700余口密井网测井资料为对象,分析了高频基准面旋回下浅水三角洲及其砂体的发育规律。研究结果表明:(1)浅水三角洲储集层主要发育在河道、漫溢砂、分流砂坝、天然堤、决口扇和席状砂等6种成因砂体,以河道砂体和分流砂坝砂体为主。(2)在岩心和测井曲线上可识别出河道底部冲刷面、进积—退积作用面、退积—进积作用面和湖泛面等4种基准面旋回物理界面;并识别出3大类、7亚类超短期基准面旋回类型。(3)高频基准面旋回演化过程中,湖泊浅水三角洲沉积区可容空间变化不大,沉积物供给通量在可容空间增长速率(accommodation increasing rate,A)和沉积物供给通量(sediment supply rate,S)的比值A/S变化中起着主导作用,进而控制着成因砂体的数量和空间接触关系。当A/S值由小变大时,浅水三角洲的规模快速变小,成因砂体的数量也相应减少;同时,成因砂体垂向接触方式由下切叠加式→加积叠加式→孤立式变化,砂体平面分布的复合连片程度也发生由高到低的变化。
Shallow delta reservoirs are of great significance in the exploration of oil and gas in continental lacustrine reservoirs. However, the detailed study based on the data of close well nets is still scarce. Guided by the theory of high-resolution sequence stratigraphy and sedimentology, the core data of more than 14 coring wells in the No.3 sand group of the fourth member of the Cretaceous Quantou Formation in the DT91 block, Fuyu Oilfield, Songliao Basin, This paper analyzes the development of shallow water delta and its sand body under high frequency base plane cycles. The results show that: (1) The shallow-water delta reservoirs mainly develop in 6 types of sand body, such as river channel, diffuse sand, distributary bar, natural bank, rupture mouth fan and sand-like sand, Mainly. (2) Four datum surface physical interfaces were found on the core and well logging curve such as scouring surface at the bottom of the channel, sediment-sedimentary facies-sedimentary surface, sedimentary-sedimentary facies, and lake flooding surface. And 3 Category 7, Ultra-short-term base-level cycle types. (3) During the evolution of high-frequency base-level cycles, the available space of the shallow lacustrine delta sediments changed little, and the sediment supply fluxes varied with the increasing of accommodation increasing rate (A) and sediment flux supply rate, S) plays a leading role in the change of A / S ratio, which in turn controls the quantity and spatial contact of genetic sand body. When the value of A / S increases from small to large, the size of shallow water delta decreases rapidly and the number of genetic sand bodies decreases correspondingly. At the same time, the vertical contact mode of genetic sand body changes from undercut over to overridden to overlay. , The level of composite contiguous sand body distribution changes from high to low.