Lithofacies combination recognition and its impact on the reservoir in No.8 sand group of the second member of Shahejie Formation in the south of Tuo11 area
The mid-high permeability sandstone reservoir has been in the late stage of ultra-high water cut after several decades of water flooding. The high water consumption zone with strong water absorption and low displacement efficiency were inevitably formed in the sandstone reservoirs,moreover formed only at a specific position of single sandbody. It has been difficult for regarding the geological analysis of single sand body as the research unit to meet the needs of residual oil excavation in such reservoirs. Based on the lithofacies analysis of core and outcrop,the development geological research unit was refined into the lithofacies combination grade with lithology as the main controlling factor,and the conventional logging data of the lithofacies combination were interpreted geologically by the grey correlation analysis method. Based on the well data,the lithofacies modes of the composite mouth sand bars and the single sand bodies in No.8 sand group of the second member of Shahejie Formation were summarized in the south of Tuo11 area. Combining with the seepage characteristics of the reservoir,it was concluded from the standpoint of static geological factors that the high water consumption zone would develop in the superposition mode of bar Ⅱ-bar Ⅱ in the composite sand bodies,and in the middle part of the lobe body of the single main bar Ⅱ mode in the single sand body,and the development position of the high water consumption zone corresponds to that of the bar Ⅱ in vertical direction.