Abstract: The fracturing pressure of ultra-deep reservoir is high, and the requirement on power and carrying capacity of treatment equipment is even more strict, so that there are some hidden troubles in safe work practice. Fracturing pressure model of ultra-deep reservoir is studied, fracturing pressure prediction model of perforated well established by utilizing acid sensitivity of rock mechanical properties and acid pretreatment to decrease formation fracturing pressure, and mechanisms of acidizing pretreatment decreasing fracturing pressure analyzed. According to lab study for a certain western deep gas reservoir about the variation of rock elastic modulus, Poisson ratio and rock compressive strength, fracturing pressure of the reservoir before and after acidizing pretreatment is calculated. The results show that fracturing pressure declines dramatically after acidizing pretreatment, and acidizing pretreatment has significant effect on decreasing pressure of fracturing operation. Under available engineering and technical condition, the job supplies good means for accurately forecasting fracturing pressure and operation pressure, reasonably selecting operation equipment and decreasing risk of reservoir reformation.

Key words: ultra-deep well fracturing, fracturing pressure prediction, acidizing pretreatment, decreasing formation fracturing pressure, calculation analysis