The majority of oil fields in the Russian Federation are developed using reservoir pressure maintenance (RPM). This means that only producing and injection wells are used in development system. Injection wells are used to pump foul water – the mixture of produced water and water from surface sources (usually it is fresh). Such a mixing causes balance shift and precipitations. Generally, both technical state of RPM systems and the quality of water used for injection is a serious problem for operators. This water contains mechanical impurities, oil products, precipitating salts and a large number of ferric iron ions that appear due to corrosion of oilfield equipment (first of all, the tubing). This water goes to formation that results in the contamination of bottomhole zone, wellbore damage and, as a consequence, in oil recovery reduction.

The most widespread technology for bottomhole formation zone cleanout of injection wells is acid treatment. Hydrochloric acid is used for carbonate formation treatment, and mud acid (combination of hydrochloric and hydrofluoric acids) is applied for terrigenous formation treatment.

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