Minerals Dissolution Effect on the Mechanical Properties of Synthetic Carbonatic Rocks under a Reactive Fluid Injection

Abstract

This research aims to evaluate the change in the stiffness and shear strength of synthetic carbonate rocks submitted to a reactive injection fluid. Therefore, laboratory tests were carried out with two types of cemented carbonatic rock artificially produced. The synthetic rocks were subjected to physical characterization tests (mineralogy, computed tomography, porosity, etc.) and mechanical characterization (uniaxial compressive strength and Brazilian tests) before and after the dissolution process to assess any changes in the samples. The dissolution test was performed in a modified oedometer cell, which allowed for measurements of horizontal displacements. The loading and dissolution phases were conducted using water and an acid solution to evaluate the influence of pH on their initial characteristics of the samples. The X-ray diffraction analysis revealed that the increase in maximum porosity by 57.8% and the increase in permeability were due to the dissolution of minerals. During dissolution, the horizontal stress increased linearly, and the maximum volumetric strain was 12.8%, owing to the loss of mass. This was also reflected in the mechanical characteristics since the samples lost about 72% of the strength after the dissolution with the acid solution. The study carried out in this paper helps explain and estimate changes on a micro-scale, that is, to understand how the dissolution of bonds between grains leads to macro-scale changes, such as the loss of mechanical strength causing irreversible damage to the rock.