川南页岩气压裂返排液^(226)Ra放射性影响评估与研究

The Impact Assessment and Study of ^(226)Ra Radioactivity in Shale Gas Flowback Water in the Southern Sichuan Basin

黑色页岩层中所含^(226)Ra随返排液排出,是页岩气开发的环境风险之一。基于川南压裂返排液水质及放射性水平的调查研究,建立了^(226)Ra放射性浓度与TDS的关系。同时,结合压裂返排液的处理过程,分析了压裂返排液^(226)Ra的归趋,并对处理过程产生的污泥进行了放射性评价。结果表明,^(226)Ra含量处于四川省江河水和泉水正常背景值范围内;^(226)Ra在软化过程中与Ba^(2+)通过共沉淀机制转移至污泥,但污泥内外照射指数均低于限值,且浓度值远低于天然放射性核素免管浓度值,可免于核辐射防护监管;软化处理可显著降低页岩气压裂返排液的总α、总β放射性水平,避免页岩气压裂返排液给环境带来的风险。

^(226)Ra in black shale would be carried out during the flowback process,which may cause the radioactivity risk of flowback water.The relationship between ^(226)Ra and TDS was established based on the investigation of water quality and radioactivity level of flowback water in the southern Sichuan Basin.The fate of ^(226)Ra was determined and the radioactive level in sludge was evaluated during the process.The results showed that ^(226)Ra radioactivity of Sichuan shale gas flowback water was in the normal Sichuan river and spring background value range,^(226)Ra co-precipitated with Ba2+into sludge together in the softening process,but the low internal and external irradiation index and concentration indicated that radiation supervision should be exempted.After softening,grossαand grossβradioactivity in flowback water did not exceed the maximum permissible emission concentration,so this can avoid environmental risks associated with shale gas fracturing flowback water.