This paper is focused on how a field test for gas injection was simulated, in a gas and condensate reservoir in tight sands deposits belonging to Lajas Fm. from Cuyo Group, in the Neuquén Basin. The Lajas Fm. is conformed of siliciclastic rocks from a delta front with an average of 600 meters of total thickness and 100 meters of mineralized thickness and conform the main target formation in General Fernandez Oro area. A compositional numerical simulation was performed in the pilot area, wich intended to reproduce fluid composition and its vertical variations. A good history match was achieved in the phase when the well was a gas producer and in the latter injection phase. The field data and the simulation results showed low production of liquid hydrocarbons, below the expected results. These results discouraged the continuity of this project, however, it was thought to re shape the project to a seasonal gas storage project. The recovery ratio in 4 months was about 60%, and then the well was closed. After 9 months, the well was on stream again and about 90% of injected volume has been recovered. If there is opportunity to inject in a few wells, the total storage capacity can be compared with actual storage projects in the area.