Influence Of Alluvial Fan Reservoir Architecture On Remaining Oil Distribution,example From The Xiaoji Oilfield,Huanghua Depression

Alluvial fan reservoirs have strong heterogeneity and complex internal structure,which results in relatively low average recovery rate and relatively large remaining recoverable reserves of this type of reservoir.Discussing the influence of alluvial fan reservoir architecture on remaining oil distribution is helpful to further guide the potential tapping work of the remaining oil in this reservoir.This paper takes the alluvial fan reservoir developed in the first member of the Kongdian Formation,Xiaoji Oilfield,Huanghua Depression as the research object,and refers to the research results of the alluvial fan reservoir architecture in Dagang oilfield,establish a detailed geological model that can reflect the geometry and contact relationship of different grades of architecture units,combined with reservoir numerical simulation technology and macro & micro remaining oil distribution physics simulation experiments,summarize the influence of the alluvial fan reservoir architecture on the distribution of remaining oil from three dimensions of reservoir scale,sand body scale and pore scale respectively.The research shows that:(1)under the control of the architecture,there are mainly four types of reservoir scale remaining oils in this area,including braided sand island enrichment type remaining oil,braided channel enrichment type remaining oil,braided channel weakly connected type remaining oil,and overflow sand body enrichment type remaining oil.(2)The number and position of interlayers in braided sand island have obvious control on the distribution and recovery of remaining oil in the sand body.The accretion sand body sandwiched between the two interlayers is the key area for remaining oil enrichment.Highly efficient recovery can be achieved by horizontal drilling,increasing displacement speed,and plugging water flooded layers,with efficiency decrease in turn.(3)By establishing the quantitative micro-residual oil classification evaluation criteria,the residual oil of the pore scale in this area can be classified into three categories: migration type,adhesion type and retention type.The above three different categories can be further divided into six different types based on their connectivity.