Abstract: Because the near wellbore friction pressures were very high in pre-frac mini fracturing tests in two gas wells in an oilfield, reperforations were then conducted to reduce the high friction pressure. The well jobs were successful, but the operation costs were high. The post-frac analysis showed that the amounts of the fracturing fluid pumped in such pre-frac mini fracturing tests were too small to effectively displace gas and thus causing gas-liquid two phase flow in the near wellbore pore spaces, which accounted for the high friction pressures. This paper presents the theoretical analysis of the fracturing friction pressures and proposed a new mini-frac method. Application of it to many wells indicate that such two-phase flow interference can be removed by over 85%, hence, the operation time and costs have been reduced greatly.

Key words: near wellbore friction pressure, two phases flow, mini-frac, pressure decline test