摘要： 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。

关键词: 基准面旋回, 浅水三角洲, 成因砂体, 发育规律, 扶余油田, 松辽盆地

Abstract: Shallow-water delta reservoirs play an important role in the petroleum exploration of lacustrine basin,but so far,research based on data of dense well block is rare. Guided by high-resolution sequence stratigraphic theory and sedimentology, and based on 14 core well data and 700 well logging data of the 3rd Group of Member 4 of Cretaceous Quantou Formation in DT91 block of Fuyu Oilfield in Songliao basin,this paper analyzed the development regularity of shallow-water delta and sand bodies under control of high-frequency base-level cycle. The result indicated that: (1)Six types of sandbodies including channel sandbodies,overflowed sandboies,distributary bar,natural levee,crevasse splay and sheet sandbodies are widely developed in the shallow-water delta reservoirs,and channel and distributary bar sandbodies are dominant;(2)Four physical interfaces of base-level cycle including channel erosion surface,progradation-retrogradation,retrogradation-progradation interfaces and flood surface can be indentified in drilling cores and well logging data; seven types of super-short-term base-level cycle can be identified. (3)During the evolution of high frequency base level cycle,the accommodation for a shallow water delta showed little variation,while the sediment supply rate played the main role in the variation of A/S(accommodation increasing rate,A;sediment supply rate,S),and thus controlled the variation of quantity and space contact relationship of genetic sandbodies. As the A/S increased,the scale of shallow water delta and the quantity of genetic sandbodies were rapidly decreased;Accordingly,genetic sandbodies stacking pattern changed from downcuting,overlapping to solitary,and the continuous degree of the planar diatribution of sandbodies changed from higher to lower.

Key words: base-level cycle, shallow-water delta, genetic sandbodies, development regularity, Fuyu Oilfield, Songliao Basin

中图分类号: 

• P512.2