Hydrofluoric acid is one of the few chemicals, which could be used for alumosilicates dissolution in almost all the temperature range. These properties determine wide implementation of mud acid in oil and gas producing industry. High reactivity of mud acid also has several drawbacks such as high probability of secondary and tertiary precipitates formation in pore volume, which becomes even higher at high alumosilicate content in formation matrix and pore volume, high reactivity of these alumosilicates and high concentration of hydrofluoric acid in mud acid. All of the above factors might decrease productivity index of treated well below the productivity level achieved prior to the acid treatment. This means that pore plugging by secondary and tertiary precipitates might be more severe comparing to the pore plugging by the initial colmatants. The source of secondary and tertiary precipitates is a reaction between spent acid and remaining alumosilicates in oil or gas bearing formation. This process is forced by too high concentration of aluminum and silicon fluorides and their complexes in spent mud acid, which caused by too high reaction rate of mud acid and alumosilicates. All these facts require design and production of novel retarded fluoro-based acid systems able to complex aluminum and silicon soluble compounds to reduce their hydrolysis rate for implementation in highly reactive formations. The article presents the results of implementation of specifically designed organic mud acid system.
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