Time-Dependent Measurements of Shale's Compressive Strength When Contacting Ionic Solutions.

Abstract

Time-dependent measurements of uniaxial compressive strength, and ionic and water transport were conducted to analyze the alteration of shale’s strength, as a function of time, when exposed to aqueous solutions. Results showed that the compressive strength of shale is time-dependent, and it relies highly on water activity and ionic concentration differences between shale and aqueous solutions. Data obtained from this work showed that time-dependent water and ion transport into shale correlated well with compressive strength measurements. It was revealed that initial water extraction by osmosis strengthened shale until ions and their associated water clouds invaded shale causing reduction in its strength. It is quite possible that water flow by diffusion osmosis may have counteracted water flow by chemical osmosis rendering ionic diffusion as the primary regulator on shale strength alteration. Furthermore, it was found that alteration of compressive strength when it interacted with aqueous solutions could be adequately explained within the confines of chemical osmosis, ionic diffusion, and diffusion osmosis. Data suggests that the impact of chemical osmosis on compressive strength is observed earlier than ionic diffusion and diffusion osmosis. Data also showed that potassium ions seem to contribute to the enhancement of the compressive strength of shale.