The Effect of Spent Acid on Carbonate Rock Wettability during Matrix Acidizing Treatment

The purpose of current study is to investigate the effect of spent acid on wettability alteration of carbonated rock. Spent acid was prepared from HCl 15 %. Linear core flooding was conducted to inject spent acid through carbonate rock and sessile drop technique was used to determine theoriginal and altered wettability of carbonate rock samples.The analysis of experiments performed before spent acid injection indicates that the contact angle of n-heptane droplet on polished rock surface surrounded by distilled water attained an average angle of 143 degrees. This angle lies in the range of water-wet rock. After acid treatment average of attained contact angle is 124 degrees.This angle also lies in the range of water-wet rock; but the contact angle in this case is less than the contact angle of intact carbonate rock; therefore spent acid tends the carbonate rock toward the oil wet phase.

Keywords:

Spent acid , wettability , contact angle , polished rock sample , sessile drop technique