Acid Sensitive Aluminosilicates: Dissolution Kinetics and Fluid Selection for Matrix Stimulation Treatments

Dissolution kinetics of analcime (a zeolite ), chlorite, and illite (layered aluminosilicates) were determined in HCl and mixtures of HF acid systems. Analcime dissolved at a much higher (by an order of magnitude) rate than kaolin, chlorite, or illite in 15 wt % HCl or 9/1-mud acid. Mud acid treatments (9/1 and 12/3) for two formations were compared using batch reactor experiments and simulations with a validated geochemical model. The simulator was a valuable tool to extrapolate the experimental results in reservoir conditions over a broad range of temperature. The outputs showed the different effects of the acids and allowed the determination of the critical temperature for each treatment. 9/1-mud acid had a higher T_c (T = temperature, c = catalytic activity) than 12/3 mud acid, although 12/3 mud acid was more stimulating at low temperature when no zeolite was present. Acetic acid (10%) could be used without damaging the formation at higher temperature than HCl (10%). At low temperature, HCl 10% was more efficient in dissolving carbonates prior to the main stage. Based on the simulations, guidelines could be provided to optimize an acid treatment, and to avoid damaging the reservoir.