A New Model for Predicting Wormhole Structure and Formation in Acid Stimulation of Carbonates

Abstract

Abstract We present a new averaged model for describing wormhole formation in carbonates. The model presented here captures the reaction and transport mechanisms at the pore scale and couples it to the Darcy scale through the use of two concentration variables, structure property correlations and mass transfer and dispersion coefficients. A salient feature of the model is that it captures both the reaction and mass transfer controlled regimes simultaneously, thus enabling the study of a wide range of stimulation fluids. Three important dimensionless parameters are identified in the model, namely, the Thiele modulus (pore scale parameter), Damköhler number (core scale parameter) and the acid capacity number that depends on the fluid/mineral system. Comparison of model predictions to experimental data shows good agreement. A preliminary analysis is presented on the factors that influence wormhole density.