Establishment and Application of a Novel Four-Dimensional Model for Simulation of a Natural Water Flooding Reservoir—A Case Study of Nanpu No. 2 Structure in the BHW Basin

Abstract

Long-term development of fluvial reservoirs causes regular changes in the microscopic pore-throat structure, physical properties and phase permeability curves of the reservoirs, and the evolution history of different oil layer varies. These effects can be explored using a four-dimensional (4D) model of the maturing field. The logging curves of 89 sand bodies of the Nanpu No. 2 structure in the Bohai Bay Basin were restored to the non-water flooded state based on the changing status of water flooding layers at different stages and levels, and an original geological model was established by combining data for the old wells. The time-varying relationship was incorporated in the dynamic model with surface flux as the variable, and the numerical simulation analysis was conducted based on the reservoir time-varying characteristics. The results showed that ① the logging data of the water-flooded layer significantly affected the simulation results of the geological model and can only be used for the establishment of the initial geological model after repositioning of time and space; ② the time variation of reservoir properties and relative permeability markedly affected the simulation results of the remaining oil. Reservoir parameters and fluid properties simulated by the 4D model were consistent with the data of water flooded layers in new wells during different periods; ③ the novel method significantly improved the fitting rate of the dynamic model, and the model was used to quantitatively describe the morphology of dominant seepage channels and reservoir variation parameters. The novel idea of ‘retreat as progress’ and ‘bring in to solve’ achieved the solution of the dynamic and static parameters of the 4D model according to each time step of space-time evolution. The results provide a guide for comprehensive adjustment and evaluation of Nanpu Oilfield for 52 well-times with an oil increase of 1.68 × 104 tons for the different stages.