[Objective]It has become a mature method to exploit shale gas by chemical oxidation and infiltration technology，The purpose of this study is to explore the influence of geochemical factors in the exploitation process. [Methods] In this study, the Doushantuo Formation shale in Yichang, Hubei Province, which has a good shale gas exploitation prospect and rich organic matter content of pyrite, was selected as the research object. Two commonly used oxidants, 15wt% H2O2 and 0.5mol/L Na2S2O8, were selected to carry out the oxidation corrosion experiment at normal temperature and pressure. The results were measured by the determination of cation concentration, pH, Eh, mass loss and XRD analysis after the reaction. According to the relevant ground water data, Na+ and SO42- are selected because they are the main ions in the Doushantuo Formation Marine sedimentary water, and Ca2+ and Mg2+, which are easy to precipitate by SO42- in the overlying Dengying formation water, are selected. The four ions and their concentrations, as well as the influence of pH and temperature, which have strong influence on the oxidation and dissolution effect in related mining technologies, are also selected. [Results]The results show that Na2S2O8 is superior to H2O2, and the advanced oxidation process driven by pyrite and the erosion effect of carbonate under acid production make the acidic environment more suitable for the dissolution of carbonate-rich shale, and the stronger the acidity, the better the oxidation dissolution effect. For carbonate-rich shale, it is necessary to appropriately increase the acidity of the reaction system to increase the permeability of shale. Temperature rise can promote the thermal decomposition of Na2S2O8 and H2O2.The thermal decomposition of H2O2 produces O2, and Na2S2O8 produces H2SO4, O2 and SO4?- with strong oxidation, so that the promotion effect of temperature on Na2S2O8 is better than H2O2. Sodium ion (chloride) can promote the release of Ca2+ and Mg2+ in the oxidation process of Na2S2O8 and H2O2, so the groundwater environment with high concentration of NaCl plays a positive role in the oxidation and dissolution of shale. Magnesium silicate precipitation will be produced in the reaction system of weakly basic magnesium ion, which is more obvious to inhibit the oxidative corrosion of H2O2. Both calcium ions and sulfate ions can produce gypsum precipitation by influencing the interaction between the reactions, thus affecting the oxidative dissolution of shale. Low concentration of exogenous calcium ions inhibits the buffer effect of carbonate and produces a promotion effect, while high concentration of exogenous calcium ions will produce secondary mineral precipitation, block shale pores and hinder the oxidation and dissolution of shale. However, the effect of sulfate ions on the oxidative corrosion of shale is opposite to that of calcium ions. The low concentration of exogenous sulfate ions inhibits the oxidative corrosion of shale by generating secondary ore and inhibiting the oxidation reaction of pyrite. [Conclusion]Therefore, in the future, in the process of shale gas oxidative fracturing, it is necessary to investigate the water chemical parameters of the exploitation formation in advance, and select the oxidation liquid and mining mode according to temperature, pH and cation ions. In chemical oxidation infiltration technology, there are still some problems, such as O2 doping in natural gas caused by H2O2 decomposition, which needs further research.
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