In order to solve problems associated with acidizing the oil reservoir in K 1 S 2 «Tuha» oilfield, the paper analyses the petrologic feature of the reservoir stratum and the character of the clay mineral based on the special geologic feature of the reservoir stratum. The rock samples consist of different minerals and have been chosen to react with 15%HCl, 12%HCl+3%HF and 10%HF+8%HBF 4 . The mechanism of acid sensitivity has been evaluated. Results show a medium to strong acid sensitivity for

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... reservoir to hydrochloric acid with a sensitivity index of 17.63% to 30.79%. The acid sensitivity index of the reservoir to 12%HCl+3%HF is 52.87% to 60.84%. This is the strongest acid sensitivity. The acid sensitivity index of the reservoir to 10%HF+8%HBF 4 is -21.3% ~ -23.3% indicating no acid sensitivity. The primary cause of the acid sensitivity is due to the presence of various common clay minerals. In order to realize the effect of increasing acidification in K 1 S 2 «Tuha» oilfield, the geological characteristics of the research should be strengthen and the results used to simulate the effect on production.