Abstract The shale-fracturing fluid interaction and its effects on the pore structures and adsorption characteristics of shale are the key factors affecting shale gas exploration. To address this problem, the black shale samples obtained from the Lower Silurian Longmaxi Formation in Sichuan Basin, China were exposed to slick water fracturing fluid at the simulation conditions of 100 °C and 50 MPa for 72 h through a fluid-rock interaction simulation instrument. The slick water fracturing fluid contained 0.2 wt.% friction reducer, 1 wt.% clay control agent, 0.15 wt.% cleanup agent and 0.05 wt.% demulsifier. The mineral composition, pore structure and methane adsorption capacity of shale samples before and after slick water fracturing fluid treatment were measured by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), low-pressure nitrogen adsorption and methane isothermal adsorption experiments using the gravimetric method. The results showed that the carbonate minerals were dissolved during treatment, and as a result, the samples developed many dissolution pores measuring 2–5 μm in diameter, while the other minerals remained relatively undisturbed. The specific surface area and total pore volume of shale sample were reduced after the reaction, and the shale-fracturing fluid interaction exhibited a stronger influence on the mesopores. However, the average pore diameter of nanopore was enlarged after the reaction, increasing from 4.29 nm to 4.78 nm. The changes of fractal dimensions suggested an increase in the roughness of pore surfaces, and the pore structure became more regular. The methane adsorption capacity in shale treated with fracturing fluid was reduced from 1.23 mmol/g to 0.95 mmol/g. The changes in the pore structure and adsorption characteristics of shale could affect the gas flow and gas adsorption capacity. These results indicated that the slick water fracturing fluid may play an important role in shale matrix stimulation.

中文翻译：

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滑溜水压裂液对页岩储集岩孔隙结构及吸附特性的影响

摘要 页岩-压裂液相互作用及其对页岩孔隙结构和吸附特性的影响是影响页岩气勘探的关键因素。针对这一问题，通过流岩相互作用模拟仪器，将四川盆地下志留统龙马溪组黑色页岩样品暴露于滑溜水压裂液中，模拟条件为100℃、50MPa，时间为72h。 . 滑溜水压裂液含有0.2wt.%减摩剂、1wt.%粘土控制剂、0.15wt.%净化剂和0.05wt.%破乳剂。采用X射线衍射仪（XRD）、场发射扫描电子显微镜（FE-SEM）对滑溜水压裂液处理前后页岩样品的矿物组成、孔隙结构和甲烷吸附能力进行测定，使用重量法进行低压氮气吸附和甲烷等温吸附实验。结果表明，碳酸盐矿物在处理过程中发生溶解，因此样品中形成了许多直径为 2-5 μm 的溶蚀孔，而其他矿物保持相对不受干扰。反应后页岩样品的比表面积和总孔隙体积减小，页岩-压裂液相互作用对中孔的影响更大。然而，反应后纳米孔的平均孔径增大，从 4.29 nm 增加到 4.78 nm。分形维数的变化表明孔隙表面粗糙度增加，孔隙结构变得更加规则。压裂液处理页岩甲烷吸附量从1.23 mmol/g降低到0.95 mmol/g。页岩孔隙结构和吸附特性的变化会影响气体流动和气体吸附能力。这些结果表明滑溜水压裂液可能在页岩基质增产中起重要作用。