Effects of porosity heterogeneity on chemical dissolution-front instability in fluid-saturated rocks

Abstract

Homogeneity and heterogeneity are two totally different concepts in nature. At the particle length scale, rocks exhibit strong heterogeneity in their constituents and porosities. When the heterogeneity of porosity obeys the random uniform distribution, both the mean value and the variance of porosities in the heterogeneous porosity field can be used to reflect the overall heterogeneous characteristics of the porosity field. The main purpose of this work is to investigate the effects of porosity heterogeneity on chemical dissolution front instability in fluid-saturated rocks by the computational simulation method. The related computational simulation results have demonstrated that: 1) since the propagation speed of a chemical dissolution front is inversely proportional to the difference between the final porosity and the mean value of porosities in the initial porosity field, an increase in the extent of the porosity heterogeneity can cause an increase in the mean value of porosities in the initial porosity field and an increase in the propagation speed of the chemical dissolution front. 2) An increase in the variance of porosities in the initial porosity field can cause an increase in the instability probability of the chemical dissolution front in the fluid-saturated rock. 3) The greater the mean value of porosities in the initial porosity field, the quicker the irregular morphology of the chemical dissolution front changes in the supercritical chemical dissolution systems. This means that the irregular morphology of a chemical dissolution front grows quicker in a porosity field of heterogeneity than it does in that of homogeneity when the chemical dissolution system is at a supercritical stage.