Document Type : Research Paper
Department of Petroleum Engineering, Faculty of Chemical Engineering, Tarbiat Modares University, Tehran, Iran
This study aims to numerically determine the roles of the geochemical reactions during the injection of a strong acid into a sandstone sample. As a case study, we used laboratory results of hydrochloric acid (HCl) injection into a sandstone core plug sample from the literature. As the exact cement composition of the implemented sandstone was not available, two probable cement compositions were considered (i.e., calcite and dolomite cement). A fully-implicit model, coded in Python, was used to simulate the underlying geochemical reactions during the HCl injection (i.e., equilibrium and kinetical reactions). In addition, the reactive surface area and porosity-permeability changes of the rock sample were included in the model. The modelling results show that dolomite cement matched better than calcite cement with the experimental acidizing data. A perfect effluent pH prediction was therefore achieved when the reactive surface area was considered as a function of mineral volume fraction. Moreover, a detailed analysis of the dissolution/precipitation rate of different minerals involved in simulations was provided. The presented model improves our understanding of sandstone acidizing by determining dominant reactions.