Impact of parameters׳ time variation on waterflooding reservoir performance

In this paper, experimental statistic data from cores of Shengli oilfield, China were utilized. Firstly, the relationship between permeability/wettability/oil viscosity and the ratio of flow-through water volume to pore volume were presented. Secondly, the ratio of grid flow-through water volume to pore volume, denoted as Rwpv, was used to describe the parameter time-variation mechanism. Finally, a numerical simulation software package was developed by introducing Rwpv into the traditional black oil model to characterize the time-variation mechanism in water-drive reservoirs. The new simulator was verified through comparing with commercial reservoir simulator ECLIPSE and experimental data. Simulation results show that the time-variation of permeability and oil viscosity decreases the ultimate recovery compared to the cases without considering time-variation effects; and wettability time-variation makes the reservoir rock more water-wet, which leads to higher ultimate recovery. This research found that both time-variation effects affect the ultimate oil recovery, but in different ways; and time-variation impact becomes increasingly significant as the waterflooding process becomes longer. Both the experimental results and numerical simulations significantly improve the interpretation of the parameters׳ time variation mechanisms and effect on waterflooding.