The Cañadón León block is located on the southern flank of the Gulf of San Jorge basin. This area has more than 2000 wells drilled and only 110 wells reach more than 100 meters within the Pozo D-129 Formation. This unit is the base of the Chubut Group, deposited in a lacustrine environment with a wide areal distribution. Cañadón León - Central is the most productive field with an area P50 of 10.5 km2. The smooth structure has a low angle (4-5°) and NE dip, the productive reservoirs are between 2200-2400 md. The reservoirs have a total thickness of 100 meters, the porosity is between 8-22% and the permeabilities between 0.001-1 mD, up to 10 mD, indicating mixed tight and conventional reservoir conditions. Tight reservoirś production depends on hydraulic fracturing. The object of this work is to perform the technical/economic feasibility study of horizontal wells in the productive sands of Pozo D-129 Formation. The study determines through a geological / dynamic model the oil and gas production, considering different scenarios and uncertainties. Currently, the production of the Pozo D-129 Formation come from vertical wells. To optimize the field development, a static (geological, geophysical and petrophysical) / dynamic model was performed to evaluate the productivity of a multi-fractured horizontal well in the reservoir, the first in the CGSJ. Searching production potential and profitability of the area, this study results in a development plan with a pilot project to drill a horizontal well.