Petroleum engineers have paid more attention to the exploration and development of HP/HT deep gas reserves due to the increasing demands of hydrocarbon resources in the last decades. The pressure and temperature of fluid are two main parameters for petroleum engineers to design the well completion and surface facilities. It is costly and difficult to run wireline tools to measure pressure and temperature profiles in HP/HT deep gas wells because of high pressure, high temperature and production of sour components. In this study, a new numerical model is developed for calculating pressure and temperature profiles in HP/HT deep gas wells. The developed model is based on simultaneous solution of mass and momentum balance in the wellbore and energy balance equation for carbon dioxide in the wellbore and the surrounding formation. Results showed a large difference between the earth temperature and gas flow temperature inside tubing. Considering this fact is so important during well completion and surface facilities design. This study further showed pressure gradient is constant in HP/HT gas wells. Copyright © (2012) by the European Association of Geoscientists & Engineers All rights reserved.