Modeling matrix acidizing in naturally fractured carbonate reservoirs

Abstract

Natural fractures, often developed in carbonate reservoirs, have significant influence on flow fields, thus affecting wormhole propagation in matrix acidizing. They are vital factors to be considered in modeling of matrix acidizing and field treatment designs. This paper conducts a research on wormholing behavior under radial flooding conditions in naturally fractured carbonates. Firstly, statistical natural fracture models are established by using the method of Monte Carlo, based on which generate natural fracture distributions. Then the natural fractures are projected onto the matrix porosity distribution to generate a porous media of matrix and natural fractures. Secondly, Coupling the porosity distribution and natural fracture distribution with a two-scale continuum wormhole model forms a new wormhole propagation model with natural fracture effect. Finally, based on the model, extensive numerical simulation is conducted to investigate wormholing characteristics in presence of natural fractures. Parameter sensitivity analysis is done to determine the effect of the natural fracture parameters on wormhole propagation behavior. This study reveals the mechanism of wormholing in presence of natural fractures, identifies the effect of natural fractures, and provides theoretical basis for matrix acidizing designs in naturally fractured carbonates.