Experimental optimization of concentration ratio of buffering acid used for removing plugging of coal seam

Buffered soil acid is one of the commonly used acid solutions for removing plugging of coal seam. However, the effect of acidizing and plugging removal is different when the concentration ration of HF, HCl and CH3COOH is different. In this paper, the corrosion experiments and H+ reaction rate experiments of solid particles in mud drilling fluid with different concentrations of HF, HCl and CH3COOH were carried out, on this basis, the optimal concentration ratio of buffering acid is obtained. According to the permeability change of coal sample before and after removing plugging, the decontamination effect of optimized acid solution was evaluated. The results show that in the buffering acid system, HF mainly reacts with the solid particles in the drilling fluid. The addition of HCl in HF will promote the reaction, while the addition of CH3COOH in HF will reduce the reaction rate. When the concentration of HF is 9%, the dissolution rate is the highest, which can reach 45.02%. The optimized concentration ratio of buffering mud acid is 3%HCl+9%HF+7%CH3COOH. The permeability of the optimized buffering acid removing plugging coal sample can be restored to 92.08%-110.88% of that before pollution.