压裂返排液中溴盐示踪剂的酚红分光光度法检测

The Detection of Bromide Tracer in Hydraulic Fracturing Flowback

随着压裂改造规模的扩大,对化学示踪剂及其检测技术的需求随之增加,但是压裂液添加剂很可能影响检测的灵敏度和准确性。实验研究了瓜胶(HPGG)及聚丙烯酰胺(HPAM)压裂液的模拟返排液中溴离子的酚红分光光度法检测方法及其影响因素。通过分析酚红分光光度法的测定原理,优化了酚红及氯胺T的加量、氧化时间等关键影响因素,指出检测出溴离子的关键在于,酸性条件下(p H值为4.7~5.7)要保证酚红的当量数大于氯胺T的当量数、氯胺T的当量数大于溴离子的当量数。实验建立了酚红光度法测定2种压裂返排液中溴离子浓度的工作曲线,浓度检测范围为2~20 mg/L,线性相关系数在99%以上。检测时应对返排液进行过滤处理,保持溴离子标准工作曲线的操作条件与试样测试时一致,以抵消复杂成分的影响。该方法对溴盐示踪剂的推广应用具有指导意义。

With increasing scale in reservoir fracturing, more rigorous requirement has been placed on chemical tracers and their detection whose sensitivity and accuracy are both affected by the addition of fracturing fuid additives. In laboratory studies, two simulated fracturing fuid samples formulated with HPGG and HPAM respectively, were detected for the bromide ions using phenol red spectrophotometry method, and the factors affecting the detection were also studied. Key factors affecting the detection, such as amount of phenol red and chloramine T, and time for the oxidation reaction were optimized based on the analysis of the measurement principles of the phenol red spectrophotometry. It is pointed out in the paper that for the bromide ions to be detected, it is critical that at pH between 4.7 - 5.7 （acidic）, the equivalent number of phenol red should be greater than that of chloramine T, whose equivalent number should in turn be greater than that of the bromide ions. Working curves were calculated for the detection of bromide ions in two hydraulic fracturing fowback fuids with the phenol red spectrophotometry. Using the two working curves, concentrations of bromides up to 2-20 mg/L can be detected with linearly dependent coeffcient not less than 99%. When detecting the bromide ions, the fracturing fowback fuids should frst be fltered, ensuring that the operational conditions for the standard working curve of bromide ions are in agreement with the operational conditions under which the samples are detected, thereby to eliminate the effects of other complex components that may exist in the fracturing fowback fuids. This detection method is instructive in promoting the use of bromide tracers in fracturing fuids.