Hierarchical modeling method based on multilevel architecture surface restriction and its application in point-bar internal architecture of a complex meandering river

Abstract

To date, the modeling method of point bar internal architecture has still not been fully developed. Traditional methods for point bar architecture modeling usually require a finer mesh, which is more expensive computationally, and upscaling the model can possibly generate a misleading model. The above restricts the industrial application of the architecture model to just oilfield development. Therefore, this paper explores and develops a hierarchical modeling method based on multilevel architecture interface constraints. This method attempts to introduce the surface-based method into the lateral accretion layer modeling of the point bars, and encapsulates and combines the top and bottom surfaces of different architecture elements as their spatial stack sequence to provide convenience for the subsequent model upscaling. During the modeling process, by using the nonuniform grid technology, different grid densities were implemented for the lateral accretion layer and lateral accretion body respectively to achieve the upscaling and simplification of the grid; In order to smooth the simulation and improve the convergence of the model, two grid orthogonalization correction schemes have also been proposed. Finally, the composite point bar sand body model can be formed by splicing and assembling different single-point bar with the hierarchical modeling method. This method has been validated in the B layer of M oilfield, which deposits the meandering river environment. Compared with older models, the new one can represent the 3D shape and physical properties of the underground architecture with a smaller number of grids. Due to the reasonable number and approximate orthogonal type of the grid, this model has a faster calculation speed and better convergence in the numerical simulation process. The simulation results show that in the oilfield development process, injected water will not spread in the traditional way, but is more affected by the architecture of the interface. In the vertical direction, the injected water flows along the bottom of the channel, and the residual oil existed in the upper part of the reservoir; in the horizontal direction, the injected water flows along the extension direction of the lateral accretion layer, and residual oil exists in the area of imperfect injection-production pattern. The above research can help us evaluate the reservoir better, and provide a specific guidance for adjustment and tapping the potential of residual oil and water-flooding optimization in a fluvial reservoir.