Llancanelo is a heavy oil field located in Malargüe department, southern of Mendoza province. The field is operated by YPF S.A. (100% of participation). The oil is a heavy to extra heavy one with around 12 API degrees and 2.000 to 10.000 cP at reservoir temperature. First wells were drilled in 1937 and field development was intermittent up to 2010 when drilling activity was resumed. Llancanelo presents many challenges; seventy five percent of the area is in a natural reserve called Laguna de Llancanelo (RAMSAR site). OPEX is elevated mainly because of high energy requirement associated with the high viscosities (Oil Liquated Gas is used to heat and power the entire production system and surface facilities, and oil production is delivered by truck). Currently the electrification of the entire field is under construction with the main objective of reduce OPEX. Field development and optimization planning involves the use of downhole heaters to reduce oil viscosity and enhanced its mobility; geosteering multilateral wells to increase contacted reservoir; drilling appraisal wells in areas with higher productive potential associated with the influence of the geothermal gradient. The structure corresponds to a reverse faulted anticline, slightly asymmetric and elongated in NW-SE direction, with a maximum displacement along the fault plane up to one hundred meters (the hanging wall is to the west part and the foot wall to the east part of the fault surface). Reservoirs are related to alluvial fans (sandstones and conglomerates) located in the upper part of the Neuquén Group. Stratigraphically they make an arrange of three electro-sequences informally named (from the bottom to the top) Blue, Olive and Green. These units are hydraulic isolated from each other by two sealing layers called Shale I and Shale II (these are fine to medium grain sandstones with a pelitic matrix). Integration of existing with the new data acquired in the last years (cores, mudlogging, and electrical logging) allowed to enrich the rock-log relationship and therefore getting a better understanding of the reservoir characteristics: sedimentological, stratigraphic, structural, and diagenetic; all of these are very important aspects for reservoir characterization as well as in geosteering new wells. This is the first of two papers in which the workflow for grid construction and probabilistic property modelling for the static model is presented. The second paper is focused on the dynamic model and how the uncertainties were assessed in the workflow with probabilistic approach.