Acid treatments are the most widely used methods to improve the well performance. Acid pumping is aimed not only on controlling the clogging of the bottomhole area, but also on improving the permeability by dissolving the minerals and creating new filtering channels. Acid treatment technology depends on many factors, including the specific geophysical conditions of the target area and type of applied acids and acid compositions. The important role during the acid treatment designing is given to a correct selection of process liquids. So, optimization of the acid composition to the mineralogy of the reservoir rock is one of the prerequisite for successful acid treatment, since chemical reactions within the reservoir are the key factors for the efficiency of the process. Practically, selection of the required acid composition is performed without the necessary research-methodological justification. So, for example, selection of acid compound for clastic reservoir treatment does not consider the mineralogy of the specific interval leading to a decreased efficiency of such treatments.
The study introduces a complex research-methodological approach to justify the selection of formulary process solutions, considering the specifics of reservoir mineralogy and pressure-temperature conditions. The approach includes the historic analysis of acid treatments results in Vietsovpetro wells, reservoir mineralogy analysis with a justified selection of main compounds for each group, adaptation of base compound formula for the specific geophysical conditions, laboratory and pilot testing. Reservoir mineralogy analysis showed that Vietsovpetro fields’ sandstones are mostly arcosic. Main acid compositions for all applied areas should consider the high content of feldspars with further fine-tuning in terms of permeability, high content of clays, zeolites, chlorites and reservoir temperature value. Basic acid compositions matrix under various permeability values has been developed for the main clastic pay zones of White Tiger, Dragon, White Bear and White Hare fields. Acid compositions formulas have been improved to adapt to the specific geophysical conditions. Main conclusions and recommendations on selecting the acid compositions formulas for the specific geophysical conditions have been verified by the laboratory and pilot testing.
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