The main objective of this study is to perform a real case study of an Iranian gas condensate reservoir for the purpose of underground gas storage. Doing such a study for this reservoir will aid in the development of this technology and will also demonstrate a new concept for underground gas storage in partially depleted gas reservoirs. After gathering some data about the reservoir and preparing a geological model for the field, a simulation plan was considered for this field. A geostatic model was converted to a;dynamic one by assigning reservoir fluid and rock data. Finally, a compositional model of the reservoir was prepared and verified to be accurate through a history matching process. After verifying the accuracy of the model and validating it, different scenarios for underground gas storage were developed. Depletion and gas storage scenarios were constructed for the field and results were obtained. Gas storage in a partially depleted gas reservoir was also considered in these scenarios for developing this field. After comparing different scenarios, some practical results were achieved and the best scenario for developing this field was chosen.