To better understand the remaining oil distribution in heavy oil reservoir with the unconsolidation sandstone before and after the infilling of the inverted nine-spot well pattern，the physical experiments were conducted to analyze the flow field and displacement efficiency after the infilling of inverted nine-spot well pattern using the three-dimensional physical model based on the practical reservoir petrophysical characters in well group. The variation of the pressure field，saturation field and displacement efficiency were obtained and analyzed after the infilling of inverted nine-spot well pattern.Before infilling，the regions with better reservoir properties have higher displacement efficiency and bigger growth rate of displacement efficiency. After infilling，the displacement efficiency became lower because of the water breakthrough at the area with better reservoir properties within a certain range of permeability. Infilling of well pattern and changing producers to injectors can improve the controlling degree of the water flooding and enhance oil recovery of 11.8%. For the reservoirs with the edge and bottom water before infilling，the remaining oil is vertically enriched in the middle and upper layers，and the remaining oil is horizontally distributed in the areas with the poor reservoir properties and regions between the edge wells and corner wells. After infilling，the remaining oil is distributed in the low-permeability regions between the producers and infill wells.