页岩气井用石英砂的耐老化机理研究

Study on Aging Resistance Mechanism of Quartz Sand Used in Shale Gas Wells

石英砂是非常规气体开采中非常实用的一种基础材料,在地层水模拟石英砂服役过程中,发现其破碎率下降。选用两种规格的石英砂在地层水中恒温浸泡不同时间,通过对浸泡前后的石英砂进行XRF、XRD、SEM、EDS、XPS、FT-IR等表征,探索石英砂的耐老化机理。XRF结果表明石英砂浸泡后ClO_(2)含量增加,XRD结果出现了SiCl_(4)和钙长石新峰,XPS结果出现了Cl2p和Ca 2p峰。这些结果揭示出地层水中的Cl-离子进入石英砂间隙中,与SiO_(2)反应生成SiCl_(4),从而生成硅酸凝胶,包覆在石英砂表面,阻断了石英砂与水的接触,加上石英砂表面附着有生成的钙长石,增加了石英砂的强度,从而提高了石英砂的抗破碎能力。

Quartz sand is a very practical basic material in unconventional gas mining.In the service process of quartz sand simulated by formation water,it was found that the breakage ratio decreased.Two kinds of quartz sand were selected to soak in formation water at constant temperature for different time.XRF,XRD,SEM,EDS,XPS and FT-IR were used to characterize the quartz sand before and after soaking to explore its aging resistance mechanism.XRF results show that the content of ClO_(2) increases after soaking,SiCl_(4) and anorthite peaks are detected in XRD results,and Cl 2p and Ca 2p peaks also appear in XPS results.These results reveal that Cl-ions in formation water can enter the quartz sand gap and react with SiO_(2) to form SiCl_(4),thereby generating silica gel,which coats the surface of quartz sand and blocks the contact between quartz sand and water.In addition,the formed anorthite is attached to the surface of quartz sand,which increases the strength of quartz sand,thus improving the crushing resistance of quartz sand.