The Golfo San Jorge gas play located at the center basin constitutes a frontier area for exploration and development, compared with its flanks, where the hydrocarbon production is concentrated. Ninety percent of this play is situated at the Gran Bajo Oriental block (2650 km2) operated by Tecpetrol since 2018, and includes Estancia La Mariposa (ELMA) and Lomita de la Costa-Cerro Mangrullo (LDLCCEMA) oil fields. Studies done in cores and cuttings on exploratory wells in GBO, together with the integration of oilfield data from the ELMA and LDLC wells, allowed identifying and characterizing uncompacted reservoirs in the Mina del Carmen Formation (MEC) at critical range depths of 3.500 mbbp. These reservoirs are clastic, mainly composed of friable conglomerates to medium-grained sandstones deposits, associated to sandy-gravelly channel facies, reaching 10-12 m layer thickness, and with porosities of 15% and permeabilities close to 3 mD in reservoir conditions. The porosity is intergranular and intra-cement, with a diagenetically early phase characterized by chlorite rims, which prevents siliceous cement formation. These reservoirs have presented in productive wells important shows while drilling, mud density decrease up to 100 gr/l, and andoccasionally field gas burning. Initial flow, ranges from 80.000 m3/d pre-frac up to 130.000 m3/d post-frac. Additionally, reservoir facies with worse petrophysics conditions were also identified; these are related to very fine sandstones associated to shallow channels and unconfined flows deposits. They reach up to 5-7 m layer thickness, and present porosities of 5% and permeabilities of 0.03 mD in reservoir conditions. These reservoirs present proved development ing in the uppermost 800 m of Mina del Carmen Formation (reaching up to 80 m of total thickness). At deeper intervals CO2 presence and the proportional increment of layers with poorer reservoirs conditions constitute an economic limit for this play.