砂质辫状河沉积模式的建立——以委内瑞拉奥里诺科重油带H区块为例

委内瑞拉奥里诺科重油带H区块Oficina下段发育大面积分布的砂质辫状河沉积,储层内重油资源丰富,拥有巨大的开发潜力。研究区目前尚处于开发前期的油藏评价阶段,平均井距较大且缺少三维地震资料覆盖,仅局部存在一定数量的新钻水平井。考虑到现有资料的实际情况,首先从动态角度分别对心滩砂坝与辫状河道的形成、演化过程予以分析,并重点讨论了活动河道、砂质河道充填、废弃河道充填三种河道存在状态的区别。在此基础上,采用现代沉积类比、经验公式调研、水平井资料应用等手段,对研究区辫状河主要沉积单元的关键参数进行表征,以恢复其发育规模。根据以上研究成果,总结本区的砂质辫状河沉积模式,并在其指导下建立三维地质模型。将该模型与研究区的储层分布预测工作相结合,取得了良好的应用效果,对于后续开发方案的实施以及提高新井的砂岩钻遇率具有重要意义。

Establishment of the Depositional Model of Sandy Braided River: A Case from the H Block in Orinoco Heavy Oil Belt,Venezuela

The lower member of formation Oficina of H block in Venezuela's Orinoco heavy oil belt is dominated with extensively distributed sandy braided river deposits. The heavy oil resources within the reservoir is rich and has a huge potential for development. At present, the oilfield is at the stage of reservoir evaluation before the development and it has relatively large well spacing with no 3D seismic coverage, only a limited number of newly drilled horizontal wells exist within part of the block. According to the existing data available in the study area, first of all, the paper analyzes the formation and evolution of the sand bar and channel from the dynamic point of view, focusing on the differences between the three statuses of active channel, sandy channel fill and the abandoned channel fill. On this basis, study methods such as modern sedimentation analogy, empirical formula utilization, application of horizontal well data are used to characterize the key parameters of the main units in braided river and to restore its scale. Based on the above research results, this paper summarizes the depositional model of sandy braided river and accomplishes the establishment of a 3D geological model under its guidance. This model is combined with prediction of reservoir distribution in the study area and good application results have been achieved. It is of great importance to guide the implementation of subsequent development plan and to improve the sand encountering ratio for the new wells to be drilled.