Removal of the filter cake created by the mud for hydrogeological drilling by the method of acidizing

The article describes issue of a mud for hydrogeological wells and a method of removing sediment accumulated on the well filter and in the near-well zone after borehole drilling. Developed fluid formula is based on both primary criterion of selecting the best technological parameters of the mud and restrictive ecological standards. Because of the contact between the mud and the underground water (which is the main source of potable water), a need to select appropriate components such as biodegradable polymers (Guar-Gum, XC) and other organic compounds that are not causing harmful environmental effects has arisen. Furthermore, developed formula allows for relatively easy removal of mud remains from the well filter and near-well zone, inereasing well efficiency. The paper includes research findings of sediment acidizing by the procedure called "soft acidizing". Any information about practical application of this procedure can hardly be found in specialized literature. Therefore, concentrations and variations of the acetic, hydrochloric and citric acids were subject of research and analysis.