Identification and quantitative description of large pore path in unconsolidated sandstone reservoir during the ultra-high water-cut stage

In unconsolidated sandstone reservoirs associated with fluvial sedimentation, large pore paths are likely to be formed under the long-term scour action of injected water. In this paper, the high-velocity non-Darcy flowing characteristics in large pore paths were analyzed. Based on the identification criteria for high-velocity non-Darcy flow, the identification criteria for large pore paths are established. According to the characteristic parameters of 101 relative permeability curves from the fluvial sedimentary units of the uncompartmentalized oilfields in Shengli oil region, the relation formulae between characteristic parameters of relative permeability curve and permeability are established. Considering the change of reservoir permeability and the relative permeability curve with permeability, a reservoir numerical simulation model is setup. The Ng63+4 development unit of the west seventh block of Gudong Oilfield is taken as a typical reservoir. The distribution position, area and volume of the large pore paths in Ng63+4 development unit are quantitatively described. The results show that the identification criteria of large pore paths which take into consideration the water–oil well spacing, production pressure difference and permeability can be used in the reservoir numerical simulation results to describe the large pore paths.