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Description
Hydraulic fracturing introduces large volumes of water-based fluids into shale, creating fracture networks and opportunities for fluid–rock interactions. This study investigates mineralogical alterations arising from the interaction of acidic stimulation fluids with shale, with emphasis on secondary ferric (hydr)oxide [Fe(OH)₃] precipitation. Two experimental conditions were considered: a brine-only case and a brine-plus-stimulation (B + S) case, where stimulation fluid was introduced midway. FIB-SEM and SEM imaging revealed two Fe(OH)₃ phases: one replacing framboidal pyrite and another forming loose aggregates in secondary pores created by ankerite dissolution, both confined to nanoscale domains. A reactive transport model, calibrated against these observations, indicated similar solubilities for both Fe(OH)₃ phases, slower kinetics for pyrite-replacing Fe(OH)₃, and a strong influence of experimental design on Fe(OH)₃ distribution. The results improve understanding of the implications of these phenomena on transport processes in shale.
| Country | United States |
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