Effects of Hydrochloric Acid on the Mechanical and Elastic Properties of Tight Dolomite

The acid-rock reaction on fracture wall has effect on the mechanical properties of rock, which would further affect the acid-fracture propagation and strength of the pillars. The effects of hydrochloric acid on the elastic and mechanical properties of tight dolomite have been assessed under triaxial stress in the laboratory. Tight dolomite were divided into acid-treatment and un-treatment groups. During the acid-treatment process, samples were exposed to hydrochloric acid in the reaction kettle with different acid-rock reaction time under high temperature and high pressure. All samples were subjected to triaxial loading up to mechanical failure under the same condition. The results show that with increase of acid-rock reaction time, acid only causes dissolution on the contact face and deepens etching groove, while the porosity and permeability of samples barely change after acid-treatment. After acid-treatment, the failure form of rock is converted from elasticity to elasticity-plasticity, and the plasticity failure becomes obvious gradually with increase of acid-contact time. The elastic moduli and Poisson's ratio reduce significantly after acid-treatment; however there is no obvious relationship between the reduction range of mechanical parameters and acid-contact time. This study reflects the effect of acid on the mechanical of tight dolomite under high temperature high pressure.