Tracer investigations is a direct and one of the most reliable methods to determine presence/source of subsurface connectivity, which have found use in geological exploration for study of reservoir fluids’ behavior and diagnostics of horizontal wells without resorting to well logging, as well as in environmental studies for evaluation of leak integrity of waste pits and search for pollution sources. In oil industry, the efficacy of tracer investigations is determined by the tracer characteristics. Tritium used to be applied on a wide scale in previous years, has all necessary characteristics to provide for accuracy and reliability of results, however, it does not meet the requirements regarding nuclear safety, so its application is restricted. Tracer systems in current use, which are organic dyes (fluorescent, ionic, alcoholic), also have a number of drawbacks, namely, a limited product range, a complicated procedure for quantitative identification of tracers. Besides, bright colors of fluorescent tracers considerably restrict hydrogeological surveys and might affect applicability of fresh water resources. To improve efficiency of upstream operations, it is important to find optimal tracers for reservoir studies to have real-time data about reservoir fluids’ behavior, inflow of reservoir fluids to wells, including horizontal wells. The synthesized carbon quantum dots specimens allowed to expand the range of tracers. The laboratory tests determined the efficiency of carbon quantum dots in comparison with the known fluorescein tracers. The paper presents a number of key indicators determined in the course of experiments such as minimal measurement limit (luminescent emission intensity), Stokes shift (difference between waves of excitation and emission), and results of core analyses. The synthesized carbon quantum dots made possible to expand the applicability of tracers and to improve performance as compared with conventional tracers. Results of laboratory experiments demonstrate good potential of the synthesized carbon quantum dots as tracers for reservoir management and ecological monitoring.
References
1. Zaytsev V.I., Sokolovskiy E.V., Sultanov S.A. et al., Primenenie tritievogo indikatora dlya kontrolya za razrabotkoy neftyanykh mestorozhdeniy v SSSR (The use of a tritium indicator for monitoring the development of oil fields in the USSR), Ser. Neftyanaya promyshlennost', Moscow: Publ. of ,VNIIOENG, 1982, V. 1(25), 39 p.
2. Morozov O.N., Andriyanov M.A., Koloda A.V. et al., Use of intelligent tracer technology for inflow monitoring in horizontal producers of the Prirazlomnoye oilfield (In Russ.), Ekspozitsiya Neft' Gaz, 2017, no. 7 (60), pp. 24–29.
3. Hartvig S.K., Huseby O., Yasin V. et al., Use a new class of partitioning tracers to assess EOR and IOR potential in the Bockstedt field, Proceedings of IOR 2015 – 18th European Symposium on Improved Oil Recovery, Apr. 2015, DOI: https://doi.org/10.3997/2214-4609.201412118.
4. Sanni M., Al-Abbad M., Kokal S., Dugstad O., Hartvig S., Huseby O., Pushing the envelope of residual oil measurement: a field case study of a new class of inter-well chemical tracers, SPE-181324-MS, 2016, DOI: https://doi.org/10.2118/181324-MS.
5. Huseby O., Galdiga C., Zarruk G.A. et al., New tracers to measure residual oil and fractional flow in push and pull tracer tests, SPE-190421-MS, 2018, DOI: https://doi.org/10.2118/190421-MS.
6. Mingazov M.N., Strizhenok A.A., Anoshina M.M. et al., Utochnenie geologicheskogo stroeniya i prognoz treshchinovatosti bashkirskikh otlozheniy Vishnevo-Polyanskogo mestorozhdeniya (Clarification of the geological structure and prediction of fracturing of the Bashkir deposits of the Vishnevo-Polyanskoye field), Proceedings of TatNIPIneft' / OAO “Tatneft'”, 2014, V. 82, pp. 52–58.
7. Mingazov M.N., Strizhenok A.A., Kamyshnikov A.G. et al., Izuchenie neodnorodnosti verkhnepermskikh otlozheniy Ashal'chinskogo mestorozhdeniya sverkhvyazkoy nefti (Study of the heterogeneity of the Upper Permian deposits of the Ashalchinskoye super-viscous oil field), Proceedings of TatNIPIneft' / OAO “Tatneft'”, 2015, V. 83, pp. 307–312.
8. Kubarev P.N., Kamyshnikov A.G., Kondakov S.V., Primenenie mnogoindikatornogo metoda issledovaniya mezhskvazhinnogo prostranstva na ob"ektakh PAO “Tatneft'” (Application of the multi-indicator method for studying the interwell space at the facilities of Tatneft PJSC), Proceedings of scientific and technical conference dedicated to the 60th anniversary of TatNIPIneft PJSC Tatneft, Bugul'ma, 13-14 April 2016, Naberezhnye Chelny: Ekspozitsiya Neft' Gaz Publ., 2016, pp. 145–149.
9. Antonov G.P., Abramov M.A., Kubarev P.N., Carrying out tracer studies to control and regulate the process of waterflooding of oil deposits at Tatneft (In Russ.) Inzhenernaya praktika, 2015, no. 5, pp. 56–68.
10. Mingazov M.N., Strizhenok A.A., Fatkhullin R.R. et al., Experience on applying indicative studies for hydrodynamic relations between Sakmarian and Upper Permian deposits in Ashalchinsky field of heavy oil (In Russ.), Georesursy = Georesources, 2015, no. 1, pp. 29–32.
11. Molaei M.J., A review on nanostructured carbon quantum dots and their applications in biotechnology, sensors, and chemiluminescence, Talanta, 2019, V. 196, pp. 456-478, DOI: https://doi.org/10.1016/j.talanta.2018.12.042.
12. Mintz K.J., Zhou Y., Leblanc R.M., Recent development of carbon quantum dots regarding their optical properties, photoluminescence mechanism, and core structure, Nanoscale, 2019, V. 11, no. 11, pp. 4634-4652, DOI: https://doi.org/10.1039/C8NR10059D.
13. Devi P., Rajputa P., Thakurab A. et al., Recent advances in carbon quantum dot-based sensing of heavy metals in water, TrAC Trends in Analytical Chemistry, 2019, V. 114, pp. 171–195, DOI: https://doi.org/10.1016/j.trac.2019.03.003.
14. Xuejiao Chen, Fuchun Gong, Zhong Cao et al., Highly cysteine-selective fluorescent nanoprobes based on ultrabright and directly synthesized carbon quantum dots, Analytical and Bioanalytical Chemistry, 2018, V. 410, no. 12, pp. 2961–2970, DOI:10.1007/s00216-018-0980-3
15. Ellis E.S., Al'-Askar M., Khotan M. et al., Saudi Aramco studies nanoparticle oil tracers in Ghawar field, Oil&Gas Journal Russia, 2017, no. 12 (122), pp. 64–69.
