Most of borehole instability problems occur when argillaceous rocks such as shales are drilled and the drilling fluid interacts with the rock. The rock-fluid interaction is materialized through the exchange of ions and water molecules between the drilling fluid and the rock, generating pore pressure variation inside the shale and changes in minerals structure. The present work has the objective of studying the changes in the physicochemical properties of shale samples when immersed in the water, inorganic and organic salts. Immersion equipment was developed in which shale samples are put in contact with fluid. The results show that immersion of shale samples in salt solutions reduce, when compared with de-ionized water, the changes in mechanics, chemical and electrochemical of solutions. The results also show that the shales from offshore platform are more reactive than terrestrial basin, in function of shale s individual constituents and microstructure. When immersed, the chlorides and formates reduce the rock water content, the changes in the rock pH, water activity of shale and interstitial water, in the cation exchange capacity, in the chemical composition of rock and interstitial water e reduce the shale s loss of mass. The results indicate that the ions presents in the rock and the fluids flow in the direction of decreasing solute concentration gradient. This result in the alteration the exchangeable bases of shales and the specific surface of clays minerals. The electronic and optic microscopy and energy dispersion spectrometry indicated a deposition of salts in the surface of samples.