Lajas Reservorio is the name of an informal reservoir sandstone unit, that belongs to the basal section of Lajas Formation in the Loma Negra block located in the eastern part of the Neuquén Basin. The reservoir is divided into two sections. The upper section with better petrophysics conditions is filled with gas whereas the lower section has non reservoir conditions. The upper section pinches out to the east part of the field, together with a gradual reduction of the net pay. The Lajas Reservorio – Precuyo interval is defined with seismic data as a depositional sequence The interval was divided into parasequences throw the presence of thiny muddy levels. The lower parasequence shows a gradual improvement in its petrophysics characteristics to the east. Seismic interpretation of the 3D cube indicates that the parasequence present in the east part of the field is the lower one. This was one of the arguments to support the proposal of a new well to the east despite the upper section with reservoir conditions is absent. Finally the Lajas Reservorio – Precuyo interval is defined as a transgressive regressive cycle. The lower parasequence has a retrogradational pattern belongs to the transgressive cycle whereas the upper parasequences show a progradational pattern and belongs to the regressive cycle.