Abstract Oxidation stimulation of gas-bearing shale is promising in enhancing shale gas recovery by improving shale matrix conductivity and promoting gas desorption. However, this technology is still in its infancy. Shale-oxidant interaction which is critical for the efficiency, safety and environment friendly of shale oxidation stimulation is still needed to be explored. In this study, carbonate-rich shale and silicate-rich shale, collected from Shuijingtuo Formation in Yichang, Hubei province of China, were used to conduct oxidative dissolution experiments with hydrogen peroxide (H2O2), sodium hypochlorite (NaClO) and sodium persulfate (Na2S2O8) at formation temperature. Combined with the analysis of water chemistry of reacted solutions, as well as the mineral composition, micromorphology, TOC content and mass change of shales, the conclusion that silicate-rich shale is more suitable for oxidation stimulation can be obtained. Na2S2O8 is more superior than H2O2 and NaClO, while the optimal OM removal oxidant is NaClO. The contribution of mineral-oxidants reaction is more profound than the organic matter removal to shale oxidative dissolution. Carbonates and pyrite are both critical minerals. Carbonates dissolution can buffer the solution pH which impedes the acid corrosion of other minerals and also releases Ca to participate in the precipitation of gypsum, which brings threaten to the effectiveness of shale oxidative stimulation by clogging pores throat and fracture or may help to induce spontaneous microfracture propagation caused by crystal growth. What's more, the dissolution of carbonates can accelerate the oxidation of organic matter, however the precipitation of gypsum can inversely hinder its oxidation. Iron-bearing mineral precipitation and other aluminosilicate minerals precipitation at alkaline condition is another important negative factor for shale oxidation stimulation. In order to accurately evaluate the effect of oxidation stimulation on shale gas recovery, the flow-through experiments should be conducted in the future.

中文翻译：

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H2O2、Na2S2O8和NaClO氧化溶解富碳酸盐页岩和富硅酸盐页岩的实验研究：氧化刺激对页岩气采收的启示

摘要 含气页岩氧化增产通过提高页岩基质电导率和促进气体解吸来提高页岩气采收率。然而，这项技术仍处于起步阶段。对于页岩氧化增产的效率、安全性和环境友好性至关重要的页岩-氧化剂相互作用仍有待探索。本研究以湖北宜昌水井沱组富碳酸盐页岩和富硅酸盐页岩为原料，采用过氧化氢（H2O2）、次氯酸钠（NaClO）和过硫酸钠（Na2S2O8）进行氧化溶解实验。 ) 在地层温度。结合反应溶液的水化学分析，以及页岩的矿物成分、微观形貌、TOC含量和质量变化，可以得出富硅酸盐页岩更适合氧化增产的结论。Na2S2O8优于H2O2和NaClO，而最佳去除OM的氧化剂是NaClO。矿物-氧化剂反应对页岩氧化溶解作用比有机物去除作用更深远。碳酸盐和黄铁矿都是重要的矿物。碳酸盐溶解可以缓冲溶液pH值，阻碍其他矿物的酸蚀，同时释放Ca参与石膏的沉淀，堵塞孔喉和裂缝，威胁页岩氧化刺激的有效性，或可能有助于诱发自发微裂缝晶体生长引起的传播。更重要的是，碳酸盐的溶解可以加速有机物的氧化，然而，石膏的沉淀会反过来阻碍其氧化。碱性条件下的含铁矿物沉淀和其他铝硅酸盐矿物沉淀是页岩氧化增产的另一个重要不利因素。为准确评价氧化增产对页岩气采收率的影响，今后应开展贯流实验。