Effect of acid-temperature-pressure on the damage characteristics of sandstone

The primary objective of this study is to experimentally study the effects of different curing temperatures (25, 50 and 75 degrees C) and pressures (5, 10 and 15 MPa) on the mechanical properties and damage deterioration mechanism of sandstone samples subjected to pH3 H2SO4. The responses of mass loss, aperture structure based on NMR, deformation behaviour and mechanical parameters of sandstone were compared and analyzed. The micro-structure change in sandstone samples was observed and analyzed with SEM-EDS. The deterioration mechanism of sandstone after treatment with acid-temperature-pressure (ATP) was discussed considering pH and ion concentration in acidic solution. The results indicated that mass, uniaxial compressive strength and elastic modulus of the samples decreased and sandstone sample porosity as well as pH and ion concentration of corrosion solution increased after treatment with APT. Under the same conditions, increasing curing temperature had apparent deterioration effect on acid-corroded sandstone, yet increasing pressure had little effect on it, especially the pressure increased from 10 MPa to 15 MPa. The results of SEM and electron spectroscopy showed that the microstructure, defects and mineral content of sandstone changed after treatment with ATP. The secondary pores increased and the surface structures became loose. The chemical reactions between sandstone samples and acidic solutions with different curing temperatures and pressures as well as the damage mechanism underlying the interaction were discussed in the theoretical context of chemical kinetics.