Injection wells have been used in enhanced oil recovery and carbon dioxide sequestration in petroleum industries for many decades. Pressure and temperature profiles of fluid flow in the injection well are two main parameters of interest for petroleum engineers to determine optimum injection conditions and wellbore completion design especially in thermal injection projects and deep wells. Although some sophisticated software packages are available for such purpose, but they suffer from slow running time, difficulty of model building skills for inexperienced users and assumptions used in those packages. In this study, a new rapid and robust procedure has been developed to calculate the pressure and temperature profiles along the depth of the wellbore by solving governing wellbore equations. The wellbore is discretized into segments and wellbore governing equations of mass, momentum and energy balance is solved simultaneously in every segment. Five injection cases from literatures, incompressible and compressible fluid flows, were used to confirm that the procedure is reproducible in terms of its behaviour, which is similar to field data.