Formation mechanism and distribution characteristics of micro residual oil in ultra-high water cut reservoirs a case study of yangsanmu oilfield

The formation mechanism and distribution characteristics of microscopic remaining oil are the basis for efficient development and enhanced oil recovery of heavy oil reservoirs in ultra-high water cut stage. This paper takes Yangsanmu heavy oil reservoir in Huanghua depression as an example, micro-displacement simulation experiment based on microscopic pore structure analysis. Through parallel experiments, the remaining oil displacement effects of water flooding combined with polymer flooding, water flooding and surfactant polymer system combination, water flooding and poly-alkaline ternary composite flooding were compared. The formation mechanism and distribution pattern of remaining oil under different displacement medium conditions were studied to find a reasonable displacement medium system. The experimental results show that the formation of microscopic remaining oil in the study area is related to the stripping effect, the flow around, the pinch action occurs, the run through effect and the adherent flow. The distribution types of remaining oil are mainly angular type, pore wall oil film type, throat retention type, dispersed oil drop type and porphyritic remaining oil in macropores. The analysis of residual oil saturation under different displacement media shows that the combined flooding effect of water flooding and poly-alkaline ternary composite flooding are the best, followed by water flooding and surfactant polymer system combination flooding. This study provides guidance for the remaining oil exploration plan of the ultra-high water cut stage heavy oil reservoir in this area.