S. Chang, G. Thomas, W. Wang, H. Ow
Keywords: optical sensor, chemical sensor, rapid sensing, DPA sensor, solid phase extraction
Summary:Oil field tracers can provide useful reservoir information such as well connectivity and volumetric sweep efficiency, which are applied for production optimization. During processing of the high saline produced water sample containing the near real-time detectable tracers, solid phase extraction is used to improve sensitivity by removing salts and impurities. Multiple tracer candidates are successfully extracted and optically detected by judicious adjustment of the salinity. The optical fluorescence detection of Advanced Tracers from produced water using solid phase extraction was demonstrated in our previous study. The high salinity of produced water and dissolved organic matter has a significant impact on the extraction efficiency of Advanced Tracers during solid phase extraction process. We improved the solid phase extraction efficiency of Advanced Tracers by investigating the effects of salinity adjustment and the capacity of solid phase extraction cartridges. Lowering salinity of the produced water prior to extraction and expanding the capacity of the solid phase extraction sorbent materials in the cartridge have been investigated in the experiment. The efficiency of the extraction was improved by an automated solid phase extraction system and validated by our customized high-performance liquid chromatography (HPLC) inline time-resolved fluorescence detection system. Various Advanced Barcoded Tracers in produced water solution have been extracted and the extraction efficiencies were calculated depending on the various salinities and solid phase extraction capacities. By increasing the capacity of the solid phase extraction sorbent materials and decreasing the salinity of produced water, Advanced Tracers were extracted more efficiently in presence of dissolved organic matter and high salt content. The improved extraction efficiency of the Advanced Tracers provides enhanced preconcentration factors, enabling unprecedented low detection limits for the Advanced Tracers. The developed method demonstrates the important advantages of improving the detectability of multiple Tracers in the presence of high salt content and dissolved organic matter. The utilization of the automated detection not only minimizes human intervention, but also improves the sample analysis throughput. This technology for tracers in produced water will be systematically validated for the upcoming field deployment, paving the way toward the development of a near-real-time tracer sample analysis approach for full-field application.