Interactions between reservoir rocks and engineering fluids during hydraulic fracturing have potential for modification of pores and flow paths by mineral transformation and precipitation and contamination of production fluids by metals and other salts. In order to infer how these interactions affect hydraulic fracturing performance, this study investigates interactions between engineering water and reservoir rocks from different chemofacies in Lower Eagle Ford Group under relevant temperature and pressure conditions. Rock samples were selected from five chemofacies in Lower Eagle Ford Group, which were divided by variations in different element concentrations and total organic carbon (TOC). Static and dynamic experiments were conducted at different condition. In static experiments, crushed reservoir rock samples were exposed to deionized water for three weeks at room condition. In the dynamic experiment, deionized water was continuously injected to the experimental system for three hours at reservoir condition. Rock samples were characterized by XRF before experiments to estimate major and trace elemental concentrations. Water samples after experiments were analyzed for ion contents, total dissolved solids (TDS), particle size and zeta potential. ANOVA single factor analysis using Tukey HSD and principal component analysis (PCA) were used to assess the similarity and difference in interactions between chemofacies. Water parameters were used to determine the tendency of suspensions to precipitate and potential to modify flow pathway during hydraulic fracturing.
This study provides information on interactions likely forming between water and Eagle Ford reservoir rocks and key geochemical tracers indicative of the effective surface areas where interactions occur. The information enhances the understanding of water-rock interaction mechanisms and distribution of fracture networks.