高频基准面旋回控制的砂质辫状河储层内部构型模式及形成机理

Sandy braided river reservoir plays an important role in enhancing oil recovery of maturing oilfields. It is of great significance to establish the internal architecture patterns and clarify the internal architecture formation mechanism of reservoir for the future exploration and development. The project intends to use the methods of combining outcrop observation and interpretation, flume experiment, and sedimentary numerical simulation to explore the internal architecture patterns and formation mechanism controlled by high-frequency base-level cycles. This research focuses on three aspects: (1) Based on the short-term base-level cycles, the architecture features of different stages are characterized, as well as the stacking relations of braided channels, braided bars, vertical accretions and falling-silt mud drapes. (2) The geometrical parameters such as thickness, width, length, inclination and other geometric parameters of the braided river reservoir at different stages are measured to establish the quantitative relationships between the scale parameters of architecture elements. (3) The evolution processes of braided channels, braided bars, vertical accretions and falling-silt mud drapes in different stages of short-term base-level cycles are analyzed. The main controlling factors and formation mechanism for the different distribution of internal reservoir architecture is discussed. After solving the problems above, it is expected to provide theoretical model guidance for the prediction of complex architecture of subsurface sandy braided river reservoir, and publish 2-3 SCI papers in domestic and foreign journals.

砂质辫状河储层是国内外老油田提高采收率的重点对象，建立储层内部构型模式，阐明储层内部构型形成机理，对于油气精细勘探和开发具有重要的现实意义。本项目拟采用野外露头观测与解释、水槽模拟实验与沉积数值模拟相结合的研究方法，对高频基准面旋回控制的储层内部构型模式与形成机理欠缺这一核心问题进行探索，重点开展3方面研究：①精细刻画短期基准面旋回不同阶段砂质辫状河储层构型特征，建立辫状河道与心滩坝、心滩坝内部垂积体与落淤层等储层内部构型叠置样式；②测量短期基准面旋回不同阶段的辫状河储层内部构型单元厚度、宽度、长度、倾角等几何参数，建立构型规模参数之间的定量关系；③分析短期基准面旋回不同阶段辫状河道、心滩坝及心滩坝内部垂积体与落淤层的发育演化过程，探讨储层内部构型差异分布的主控因素与形成机理。期待解决上列问题后，为地下油田砂质辫状河复杂储层构型预测提供理论模式指导，并在国内外期刊上发表2-3篇SCI论文。

辫状河沉积是沉积盆地的重要组成部分，是国内外油气资源的重要载体，探究其内部构型模式与形成机理，即丰富了沉积学理论，又促进了油气勘探和开发。本项目基于砂质辫状河露头与现代沉积，结合沉积模拟实验，研究了不同沉积沉积条件下（综合因素高频基准面旋回，单一因素沉积物粒度、流量、水深等）砂质辫状河类型、形成演化过程、多样化的内部构型模式及形成机理，并将上述沉积模式应用于地下辫状河储层构型解剖。研究结果表明，基准面是控制辫状河类型的重要因素，基准面由低到高，河流的地貌演化速率降低、稳定性增强，河流类型依次为游荡型辫状河、稳定型（心滩型）辫状河、“辫-曲”过渡型河流。游荡型辫状河内部河道频繁改道，冲刷面与沟道极为发育，心滩内部沙丘交错排列，不发育典型落淤层与垂积体；稳定型辫状河内部辫状河道与心滩坝边界清晰，心滩由多期落淤层与垂积体组成；“辫-曲”过渡阶段可见低弯度曲流河与稳定型辫状河共存或交替出现。就单一因素而言，水深与地形坡度是控制砂坝差异化定量模式的重要主要因素：水深是控制砂坝规模（面积与厚度）的主要因素，即水深增加，砂坝面积与厚度随之增大；地形坡度是控制砂坝的形态主要因素，坡度越大，心滩“长宽比”越大。此外，分别针对典型的游荡型辫状河、稳定型辫状河与曲流河建立了一系列、多样化定量构型模式。同时，研究成果对其他沉积相类型构型模式及形成机理研究具有重要借鉴意义。