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The Filo Morado field produces hydrocarbons from primary porosity and fractured reservoirs such as the Mulichinco Fm., a fine grained calcareous sandstone and sandy limestone with 4 to 6% primary porosity. This unit has been developed as a conventional reservoir; most of the wells resulted dry or with a very low accumulated production. New 3D seismic information is scarce and highly laterally displaced due to the structural and geological complexities. 3D geologic modeling was made from twelve 2D structural sections. The different horizons were connected to generate a 3D solid model, with different velocity layers to perform a depth migration of the seismic data. The corrected seismic data allowed to characterize the 3D geometrical distribution of the faults and geological data. 3D structural analysis, combined with surface and depth data (logs, cores, well cutting, etc.) made possible to propose a kinematic model as a doubling detachment east-directed fold combined with backthrusting that tilted and displaced the flat crest to the west. Fracture geometry was inferred from core analysis, borehole images and outcrops. Fracture genesis may be related to flexural slip and to accommodation zones and to the regional stress field after the folding mechanism was locked. A development well was drilled to structurally evaluate the different segments of the structure. Drilling results as well as production data suggest that the forelimb environment is highly fractured; in accordance with the model predictions. Introduction The development of naturally fractured reservoirs associated with complex structures is highly dependent on the amount of preexisting borehole and surface information1,2, as well as on the knowledge of the structure geometry. The chances of success in fracture array prediction derived from a stochastic approach will increase accordingly to the amount of data and sampling direction of the measurements taken on natural data. Borehole fracture geometry coming from resistivity or sonic image logs is not always available in old fields, and therefore fracture geometry predictions will rely on geological analysis that may explain the field production and evolution. Any new well proposed to intersect the open fractures would follow a deterministic approach, trying to explain and predict the genesis and geometry of the natural fractures. An example of the last case is the Filo Morado field of the Neuquén Basin (Fig. 1), where the fractured reservoir of the Mulichinco Fm. was developed like a primary porosity reservoir during the late 80's and early 90's; and consequently no much information about the natural fractures was collected. In addition to this, most of the development wells resulted dry or with a very low accumulated production. In the last three years, taking advantage of the high oil prices, a new effort to develop the field was made. A new 3D seismic survey was carried out on the field to image the structure. Because of the complexity of the structure, the Mulichinco Fm. was almost not imaged by the seismic and therefore no new wells were proposed. In the last year a new technique was used to understand the geometry of the structure and relate that to the fracturing process in order to predict fracture clustering and propose a new prospect. The purpose of this study is to show the method that was used to propose the new well to develop the fractured reservoir of the Mulichinco Formation as well as to gather as much information as possible from the natural fracture network. The Filo Morado Field. This field is located at the thrust front zone of the Neuquén basin of Argentina (Figs. 1, 2). It was discovered in 1983 by YPF, the former Argentine national oil company, and is still on production. The field has three main reservoir units (Fig. 3), the Troncoso-Chorreado Inferior and Avilé members, and the Mulichinco Formation. The first two are primary porosity reservoirs, and the latter is a naturally fractured reservoir. The field have accumulated a production of more than 30 MMbbl, and at the present it is producing 3200 bbl oil/day.