In this paper, a novel model is proposed for predicting thermo-physical properties of superheated steam (SHS) in SHS injection wells and for estimating wellbore heat efficiency. Firstly, a novel mathematical model is proposed for predicting pressure, temperature as well as superheat degree in SHS injection wells. Secondly, the direct and indirect methods are introduced to estimate the wellbore heat efficiency. Thirdly, the model solving process is introduced in detail. After validation of the model, sensitivity analysis is conducted. Results indicate that: (1). The superheat degree at well bottom increases with the increase of injection rate. (2). The superheat degree at well bottom increases with the increase of injection temperature. (3). The superheat degree at well bottorn decreases with the increase of injection pressure. In order to obtain a higher superheat degree at well bottom, the injection pressure cannot be too high. This paper presents a basic reference for engineers in optimization of injection parameters as well as estimation of wellbore heat efficiency of SHS injection wells. (C) 2017 Elsevier Ltd. All rights reserved.