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One of the most common ways of carbonate scale removal is cyclic flushing of pumps and filters with hydrochloric acid which is noted for its high dissolving capacity and low price. Application of this technique requires considering the effect of high reservoir temperatures which intensify reactivity of typical acid solutions and reduce the efficiency of scale inhibitors, resulting in substantial increase of downhole equipment corrosion rate. Nonaggressive chemicals are available that are used for dissolving inorganic salts of calcium, magnesium, and iron, while simultaneously preventing their re-deposition by aggregating cations in chelates. One of such chemicals is disodium EDTA (Trilon B). This paper presents the results of laboratory experiments for Trilon B-based solution development to remove scale under high-temperature conditions, as well as the results of corrosiveness reduction tests. Three various solutions were tested for corrosiveness. Minimal rate of corrosion for Trilon B-based solution was determined at 130oC. Quantitative and qualitative chemical analysis of scale composition was performed. Pilot tests of a new solution proved its high efficiency in scale removal from downhole pumping equipment. Laboratory and pilot tests showed that Trilon B-based solution is more efficient in removing inorganic scale from oilfield equipment during heavy oil production, compared to inhibited hydrochloric acid. References 1. Persiyantsev M.N., Dobycha nefti v oslozhnennykh usloviyakh (Oil production in complicated conditions), Moscow: Nedra-Biznestsentr Publ., 2000, 653 p. 2. Nikishina L.I., Eksperimental'nye i promyslovye issledovaniya metodov bor'by s otlozheniem soley (Experimental and field research of methods to control the scale), Moscow: Publ. of VNIIOENG, 1977, 99 p. 3. Lyushin S.F. et al., Otlozheniya neorganicheskikh soley v skvazhinakh, prizaboynoy zone plasta i metody ikh predotvrashcheniya (Deposits of inorganic salts in wells, bottomhole formation zone and methods of its prevention), Moscow: Publ. of VNIIOENG, 1983, 99 p. 4. Ibragimov N.G. et al., Oslozhneniya v neftedobyche (Complications in oil production): edited by Ibragimov N.G., Ishemguzhin E.I., Ufa: Monografiya Publ., 2003, 301 p. 5. Kashchavtsev V.E., Mishchenko I.T., Soleobrazovanie pri dobyche nefti (Salt formation in oil production), Moscow: Orbita-M Publ., 2004, 432 p. 6. Kelland M.A., Production chemicals for the oil and gas industry, CRC Press, Taylor & Francis Group, 2014. XVIII, 412 p. 7. Kolotyrkin Ya.M., Popov Yu.A., Alekseev Yu.V., Fundamentals of the theory of pitting development (In Russ.), Itogi nauki i tekhniki. Ser. korroziya i zashchita ot korrozii, 1982, V. 9, pp. 88–139.
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