Experimental Study on the Impact of Hydrogen Peroxide on the Alteration of Shale Properties During the Oxidative Dissolution Process

Gas extraction from shale is challenging due to the extremely low permeability of shale formations. In response, an oxidative dissolution treatment method was introduced to eliminate organic matter (kerogen) present in shale rock, enhance pore diameter, and increase the permeability of the formation. This research study investigates the potential of hydrogen peroxide (H₂O₂) as an effective oxidizing agent for enhancing the properties of shale cores. In detail, the impact of the oxidative dissolution process on the characteristics of shale cores was assessed utilizing two chemical systems: H₂O₂ alone and a slick water recipe (containing several additives and H₂O₂) with concentrations of 30% H₂O₂. Four shale cores were separately immersed in both solutions for durations of 2 and 4 hours at a temperature of 120°F. Various characterization techniques were employed to detect the alterations in core properties subsequent to the introduction of the chemical systems. The oxidative treatment of Eagle Ford shale cores utilizing H₂O₂ and the slick water system resulted in considerable alterations in surface morphology, porosity, and chemical composition. The SEM analysis indicated a significant enhancement in micro-porosity and surface etching, particularly following 4 hours of treatment at 120 °F, which suggests the progressive oxidative decomposition of kerogen within the Eagle Ford shale matrix. Complementary EDX data corroborated a substantial reduction in carbon content, decreasing from approximately 14.2 wt.% in untreated cores to 7.8 wt.% and 6.1 wt.% after treatment with H₂O₂ alone and the slick water formulation, respectively. Photographic images further substantiated these findings, demonstrating notable darkening and textural roughness post-treatment, as well as visual indicators of surface oxidation and the removal of organic matter. Gravimetric analysis revealed consistent weight loss across cores, ranging from 0.006 to 0.030 grams per core, thus verifying the partial dissolution of organic content without compromising core structural integrity. TOC analysis via pyrolysis further affirmed these trends, with TOC values declining from 5.7 wt.% in untreated cores to 3.2 wt.% and 2.6 wt.% following treatment with H₂O₂ and slick water, respectively. Measurements of Young's modulus by AutoScan indicated a reduction in rock stiffness ranging from 30% to 60%, signifying an increase in fractur ability following treatment. Collectively, these findings underscore the viability of H₂O₂-based oxidative strategies, especially when augmented with additive-rich slick water systems, as effective methodologies for enhancing pore network development and gas production in tight shale formations. Future investigations should explore the interplay between organic matter removal and secondary phenomena such as mineral scaling, precipitation, and alterations in thermal stability, all of which may impact long-term permeability and hydrocarbon recovery efficiency.