Abstract The drastic decline of shale gas production after fracturing depresses the development of this unconventional gas resource. Although shale oxidant stimulation can dissolve unstable composition to enhance permeability, the shale-fluids interaction during this stimulation process is still not yet clear. In this study, the organic-rich shale collected from the Cambrian Shuijingtuo Formation of Yichang, Hubei province, China was selected to react with three oxidants, hydrogen peroxide (H2O2), sodium hypochlorite (NaClO) and sodium persulfate (Na2S2O8) at formation temperature. Variation of water chemistry, mineral composition and micromorphology were analyzed to reveal the mechanism of shale oxidative dissolution and evaluate its influence on shale permeability enhancement. Results showed that pyrite and OM can be discrepantly oxidized with different oxidants. At the same oxidation duration, the acidic environment was beneficial for carbonate dissolution, while the alkaline environment was favorable to the dissolution of dolomite and tectosilicate minerals such as quartz, albite, illite and chlorite. Nevertheless, the serious thermal decomposition of H2O2, precipitation of gypsum and ferric hydroxide (Fe(OH)3) occurred during shale-fluids interaction at formation temperature might impede the enhancement of shale permeability. The oxidative dissolution of shale also brought about the release of trace elements, which might result in groundwater pollution. For the in-situ application of shale oxidative dissolution, difficulties such as thermal decomposition, secondary minerals precipitation and possible groundwater pollution should be considered further in the future.

中文翻译：

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过氧化氢、次氯酸钠和过硫酸钠氧化溶解过程中页岩-流体相互作用的实验研究

摘要 压裂后页岩气产量急剧下降，抑制了这一非常规气资源的开发。尽管页岩氧化剂增产可以溶解不稳定成分以提高渗透率，但在增产过程中页岩-流体的相互作用尚不清楚。本研究选取湖北宜昌寒武系水井沱组富机页岩与过氧化氢 (H2O2)、次氯酸钠 (NaClO) 和过硫酸钠 (Na2S2O8) 三种氧化剂在地层温度下反应. 分析了水化学、矿物组成和微形态的变化，以揭示页岩氧化溶解的机制并评估其对页岩渗透率增强的影响。结果表明，黄铁矿和OM可以被不同的氧化剂氧化。在相同氧化持续时间下，酸性环境有利于碳酸盐岩溶蚀，而碱性环境有利于白云石和石英、钠长石、伊利石和绿泥石等硅酸盐矿物的溶蚀。然而，在地层温度下页岩-流体相互作用过程中发生的 H2O2 严重热分解、石膏和氢氧化铁 (Fe(OH)3) 的沉淀可能会阻碍页岩渗透率的提高。页岩的氧化溶解也带来了微量元素的释放，可能造成地下水污染。针对页岩氧化溶解、热分解等困难的原位应用，