Modeling Sandstone Acidizing by Image Processing

The reactivity of acid with rock in an acidizing process depends on the abundance and the geometrical arrangement of various minerals with respect to each other. A model is developed to compute the rate of acid consumption and the change in rock porosity as a function of time. The minerals are located in accordance with thin section images. Under specified reaction kinetics, real time simulation of mineral dissolution is conducted graphically on a computer. Since the rate of reaction of each mineral is known, an erosion process is used to update the image of the rock as a function of time. This procedure can be recorded by a series of images and the porosity, permeability and cumulative acid consumption can be computed. It is shown that this model can provide substantially different results than a simple model that is based only on the mineral abundance in the rock matrix. In some cases this can have a significant impact on acidizing simulators that are currently used. Such simulators do not use petrographic information on the relative location of minerals in modelling acid consumption rates.