**7.4 Changes in mechanical properties**

Juan et al. [113] investigated the relative impacts of slickwater and linear gel on mechanical properties of different rock types in the Permian basin. Reactions for these set of experiments were conducted at elevated temperature and pressure conditions, 190°F and 1000 psi respectively. Their findings indicated that: linear gel caused more mechanical (Young's Modulus) reduction, about 27% compared to slickwater, about 14%; Samples with higher contents of carbonates sustained more damage relative to low carbonate samples, with carbonate etching being the primary damage mechanism in slickwater whilst that in the

### *Review of Geochemical and Geo-Mechanical Impact of Clay-Fluid Interactions Relevant… DOI: http://dx.doi.org/10.5772/intechopen.98881*

linear gel is aggressive dissolution; Most carbonate dissolution happened within the first five hours of the reaction. This experiment provides critical information on reactions between rocks and fluids at elevated temperatures and could be repeated for other types of fracturing fluids in different formations to observe the responses.

Temperature differences between injected fracturing fluids and formation have been reported to exert significant mechanical impacts during fracturing. This observation has gained attention and has become focus area for researchers. Vena et al. [114] studied the impact of large temperature differentials between formation and invading fracturing fluids. They took particular interest in changes such as clay swelling, imbibition and other mechanisms that adversely affect formation permeability. Their results indicate an initially pronounced impact on stress regimes within the formation leading to development of micro-fractures which are sealed over time. Similar findings were obtained by Elputranto et al. [115] when they used high resolution simulation methods to assess the response of formation to fluid with high temperature and salinity differentials to formation. Since perpetual propagation or opening of these micro-fractures will greatly enhance permeability of a reservoir, future research should be focused on understanding the mechanisms that can sustain these micro-fractures.

Elputranto et al. [115] used high resolution simulated models to investigate the mechanical impact on the interface between hydraulic fracture and matrix due to reactions emanating from cold and low salinity fracturing fluid invading rock formation. They simulated the responses during the well shut-in period and flowback and production periods. Their results show that thermo-elastic effects are generated in the formation that lead to increased permeability which is short lived. Based on results from this work, future research will focus on how to sustain and possibly allow better propagation of these short-lived fractures created due to thermo-elastic effects of fracturing fluid interaction with formation. Achieving this will lead to significantly improved permeability and production.
