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Los Molles Formation (Lower to Middle Jurassic), deposited under the first marine event above the synrift continental deposits of the Precuyo, is the second most important source rock of the Neuquen Basin after Vaca Muerta Formation. Los Molles Formation extends over more than 45,000 km2 and can be recognized in different geographic areas within the basin. Los Molles Formation, with a thickness that varies from 100 to 800 m, has a total organic content (TOC) ranging from 1 to 5%, vitrinite reflectance (%Ro) 0.8 to 2, Hydrogen Index 300–500 mg HC/gTOC, SPI of 6 t HC/m2, kerogen type II-III and a VKA of algal amorphous with variable terrestrial contribution. In the studied area, the unit is subdivided into three members, with different characteristics that reflect distinctive sedimentary environments from shallow marine to deltaic. In addition to its condition of source rock, conventional and unconventional shale and tight reservoirs are currently being developed mainly within the vicinity of the depocenter of the basin, mostly related to gas prone basin centered gas systems. Volume estimation assigns 190 to 270 TCF of gas to this formation and 3.7 BBO. Outcrops, three cores and fifteen wells with open hole logs consist of the database for this study. Deductive methodologies were used to characterize the formation with standard log analysis that consist of differentiating reservoir to non-reservoir rocks, sandstones, silt, tuff, clay, porosity, water saturation, permeability, TOC, Young's modulus, Poisson's ratio and brittleness index. Inductive methodologies (clustering) were used for determining electrofacies that correspond to: Sp, sand, medium to very coarse, may be pebbly, solitary or grouped; Sh, sand very fine to very coarse, may be pebbly, horizontal lamination; Fm, mud, silt, massive; and Gm, massive or crudely bedded gravel, horizontal bedding, imbrication. The results of this study demonstrate the importance of taking advantage of different techniques when studying elements of the petroleum system related to Los Molles Formation. |
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