The calculation of the bottom hole pressure（BHP）in the high temperature and high pressure the gas wells with should consider the temperature changes inside the wellbore. The coupling of the pressure and temperature need to be solved simultaneously. The current calculation methods considering the wellbore heat transfer

and the coupling of pressure and temperature mainly apply to the steady flow. However

they don’t apply to the transition flow during the shut-in period. Meanwhile

the wellbore heat transmission of the offshore gas well in high temperature and high pressure should consider the effects of sea water. Nevertheless

there are fewer examples of this research. According to the problems above and based on the basic equation

we established a new calculation model

which considers wellbore storage

and the heat transfer among the wellbore

adjacent formation and sea water.This method is successfully applied to the BHP calculation and well testing analysis for the well M1 during the shut-in period in M gas field of the western South China Sea

thus providing the basis for the temperature and pressure calculation and well testing optimization of high temperature and high pressure offshore gas well.