Abstract: Foam fluid lift can effectively drain the residual acid in acidizing treatment wells.According to energy conservation equation，mass conservation equation and momentum conservation equation，an array of ordinary differential equation for calculating the temperature and pressure distributions of foam fluid in the wellbore is established in consideration of the heat exchange between the foam fluid in the annular space and the injected fluid from tube.Boundary and
limited conditions are provided.Coupled solve of temperature and pressure distributions by using numerical method is conducted.Distribution of foam temperature，foam quality and pressure in wellbore is obtained.The results show that as the increase of well depth，foam pressure and foam density increase.Threshold pressure and balance pressure of foam fluid lift are both lower than that of nitrogen gas lift.As the increase of acid flow，the depth of circle point，threshold pressure and balance pressure are all increasing.

Key words: foam fluid, lift, acid drainage, mathematical model, parameter design