Review of long-term researches on acidizing of production and injection wells using solid acid compositions based on sulfamic acid, that were carried out at the National University of Oil and Gas Gubkin University, is presented in this paper. Sulfamic acid is formed by the interaction of carbamide and oleum at 60–70°C and is produced in the form of non-adsorbing water crystals. The behavior of the acid is associated with the formation of zwitter-ions in water, which contribute to activity increase of synthetic surfactants. Sulfamic acid has advantages over hydrochloric acid; it has a slower reaction rate with carbonate rock and is less aggressive towards metal surfaces of production equipment. Sulfamic acid produces less viscous oil-acid emulsions that do not form sludge deposits. Injection of sulfamic acid solutions into oil-saturated porous medium under thermobaric conditions of the formation leads to higher phase permeability to the displacing fluid than for hydrochloric acid. Based on the obtained regularities of interaction of sulfamic acid with rock, formation fluids and damaging agents of bottomhole formation zone, solid acid compositions for treating wells operating low-temperature depleted formations were developed. The acid treatments results confirmed the effectiveness of multistage technologies based on the application of the solid acid compositions. Previous studies showed that sulfamic acid is prone to hydrolysis at temperatures above 60°C; however, the developed technologies allow the use of the acid compositions at higher temperatures.
Acknowledgment. This work was supported by the Ministry of Science and Higher Education of the Russian Federation under agreement No. 075-15-2020-936 within the framework of the development program for a world-class Research Center.
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