Reservoir Pore-Throat Characteristics Evolution During Waterflooding: A Theoretical Study

Abstract

During waterflooding, pore-throat structure of the porous media in the reservoir changes continually, which causes the great challenge in reservoir modeling and simulation. However, through the evolution mechanism of pore-throat characteristics for the reservoir during waterflooding has been intensively investigated in the past several decades, the essential controls on pore-throat structure evolution of reservoir rocks are not studied much. It is of theoretical and practical significance to use analytical methods to study the evolution of pore-throat characteristics of porous media during waterflooding. However, because of the disordered and extremely complicated microstructures of porous media, the theoretical model for stress sensitivity is scarce. The objective of this work is to establish a novel and reasonable quantitative model to determine the essential controls on pore-throat structure evolution of reservoir rocks. The theoretical model is derived from the fractal geometry. The predictions from the proposed model agree well with the available experimental data presented in the literature, which verified the novel quantitative model. There is no empirical constant and every parameter in the model has specific physical significance. In addition, the evolution rule for the pore-throat structure parameters has been obtained. The results show that the pore-throat structure of porous media becomes more complex and more heterogeneous after waterflooding. The pore-throat parameters (e.g. porosity, permeability, the maximum pore-throat radius, average pore-throat radius and sorting coefficient, etc.) will change during waterflooding. This work presents accurate and fast analytical models to perform the evolution rule of pore-throat characteristics of porous media during waterflooding. The proposed models can reveal more mechanisms that affect the coupled flow deformation behavior in porous media.