In the last decades the exploratory projects in the Golfo San Jorge basin were focused on the basal units of the Chubut Group to extend the development of the mature fields. Apart from its well-known role as source rock, the Pozo D-129 Formation has documented oil & gas production in different areas of the basin, specially in clastic reservoirs which are intercalated with shales and limestones. The aim of this study consisted of developing an integrated multiscale analysis using well and seismic data. To accomplish this objective, wells that have drilled partially or completely the unit have been involved. The paleotopography and the main structural lineaments have affected the stratigraphic configuration, as well as the expansion-contraction lacustrine cycles. Towards the septentrional sector of the northern flank, shallower sequences were deposited while in the meridional sector, deeper facies are dominant. In addition, the Pozo D-129 Formation has a predominant transgressive arrangement which begins with prograding facies composed of alluvial fans and fan deltas facies, followed by a pyroclastic climax predominantly lacustrine and ends with the greatest expansion of the lake, consisting of deep lacustrine shales intercalated by limestone packages in its proximal areas. These facies variations have its correlation with petrophysical quality, being the clastic and shallower facies, the better. This analysis reassesses the value of old information that can be updated and used to rejuvenate the geological models of a mature basin and add value to the exploration portfolio in the search of new opportunities for deeper reservoirs.