The aim of this work was to characterize a gas sand reservoir: to evaluate areal distribution and estimate gross and net thickness. To that end, 3D seismic data, well data and seismic interpretation were used. Regarding to methodology, a prior feasibility study was performed, which consisted in: i) analysis of vertical seismic resolution vs thickness of the sand of interest; ii) availability of density and dipolar sonic well logs information, and iii) calculations of elastic parameters and generation of crossplots, in which a strong correlation between S impedance and Gamma Ray was observed. The results of this analysis motivated the realization of a simultaneous inversion. The interpretation of the different cubes derived from the simultaneous inversion allowed the extraction of attributes in a time window corresponding to the thickness of the productive sand. In particular, S Impedance cube was used, and from the observed regression (attribute vs gross), a gross thickness map consistent with well data was obtained, verifying the feasibility analysis. Subsequently, a gross/net relationship was determined to finally obtain a pseudonet map from the gross thickness map. In conclusion, a pseudonet map was obtained from the interpretation of the simultaneous inversion results. This map was verified with the last well drilled, obtaining good predictive results and it will also help to adjust the location and estimate the thickness of the next wells to drill. In addition, it will contribute as input to a simulation model, volumetric and reserves calculation of the productive sand.