Abstract
Vitric tuff is the most common reservoir rock in Akita. Fujioka and Yoshikawa recently suggested that the permeability of vitric tuff decreased when the tuff reacted with high alkali drilling mud under well conditions. They also said that oil wells producing oil from such a reservoir were required to be stimulated by acidizing treatment. Our purpose here is to investigate the reactions of hydrochloric acid on vitric tuff. The vitric tuffs used in these experiments were from 10 per cent to 20 per cent soluble when the pulverized samples were immersed in HCL at 30°C for 24 hours. The permeability of the vitric tuffs was measured with the apparatus shown in Fig. 4. Hydrochrolic acid and 1.5 per cent NaCl solution were used in the flow tests. The results are shown in Fig. 6 and Fig. 7.
