It is a well-established fact that fluids affect the mechanical behavior of rocks and a many experimental evidences have been reported so far describing their impact over relevant properties such us UCS, brittleness, etc. In the case of cracking and crack propagation the role of fluids has been commonly reduced to a hydro-mechanical coupling by which its pressurization in poorly-connected, constrained volumes (e.g. saturated micro cracks) promotes crack propagation due to the increase of pore pressure in cracks and its squeeze towards pores (squirt flow). On the other hand, chemical stimulation (i.e. injection of chemically reactive agents) has been thoroughly applied to oil & gas as well as geothermal reservoirs to enhance their performance. However, the results obtained under field conditions have not yet gained a sufficient level of understanding what indicates that it is still needed a greater effort to better understand some fundamental aspects of fluid/rock interactions, especially from the standpoint of their chemo-hydro-mechanical couplings. In the present contribution we will illustrate some ongoing results of an experimental exploratory survey performed at room P&T conditions, focused in the assessment of the effect of reactive and non-reactive fluids on crack initiation and propagation in two types of rock: A sandstone and two granites. The main measured reference property to evaluate fluid impacts is mode I fracture toughness. The results suggest that not all fluids equally enhance rock cracking (or crack propagation) while the relevance of the chemical mechanisms involved is not akin in the two studied rock types. Furthermore, some ideas on further steps including fracture toughness testing above-ambient P&T conditions will be presented.

It is a well-established fact that fluids affect the mechanical behavior of rocks and a many experimental evidences have been reported so far describing their impact over relevant properties such us UCS, brittleness, etc. In the case of cracking and crack propagation the role of fluids has been commonly reduced to a hydro-mechanical coupling by which its pressurization in poorly-connected, constrained volumes (e.g. saturated micro cracks) promotes crack propagation due to the increase of pore pressure in cracks and its squeeze towards pores (squirt flow). On the other hand, chemical stimulation (i.e. injection of chemically reactive agents) has been thoroughly applied to oil & gas as well as geothermal reservoirs to enhance their performance. However, the results obtained under field conditions have not yet gained a sufficient level of understanding what indicates that it is still needed a greater effort to better understand some fundamental aspects of fluid/rock interactions, especially from the standpoint of their chemo-hydro-mechanical couplings.

In the present contribution we will illustrate some ongoing results of an experimental exploratory survey performed at room P&T conditions, focused in the assessment of the effect of reactive and non-reactive fluids on crack initiation and propagation in two types of rock: A sandstone and two granites. The main measured reference property to evaluate fluid impacts is mode I fracture toughness. The results suggest that not all fluids equally enhance rock cracking (or crack propagation) while the relevance of the chemical mechanisms involved is not akin in the two studied rock types. Furthermore, some ideas on further steps including fracture toughness testing above-ambient P&T conditions will be presented.