Influence of pore-fluid chemistry and temperature on fracture of sandstone under confining pressure

Abstract

To evaluate the effect of chemical solutions on the strength properties of porous rocks, triaxial and uniaxial compression experiments have been made on Coconino sandstone injected with distilled water and dilute solutions of aluminum and ferric chloride. Confining pressure and internal pore pressure were applied and measured independently. Temperature was varied from 24° to 200°C. Results indicate that the strength and ductility of the sandstone are dependent on the type and concentration of the cations in the aqueous phase. Dilute solutions of aluminum and ferric iron salts, in addition to water, react with the surface structure of quartz and probably other silicates, and weaken the surface silicon-oxygen bonds by hydrolysis. This leads to a reduction in surface energy, surface cohesion, and breaking strength. ...