Analyzing a suitable elastic geomechanical model for Vaca Muerta Formation Agustin Sosa Massaro a, * , D. Nicolas Espinoza b , Marcelo Frydman c , Silvia Barredo a , Sergio Cuervo d a Department of Petroleum at Instituto Tecnol ogico de Buenos Aires (ITBA), Buenos Aires, Argentina b Department of Petroleum and Geosystems Engineering, The University of Texas at Austin, USA c Schlumberger Technology Integration Center, Buenos Aires, Argentina d Unconventional Resources - Asset Development Team, Chevron, Houston, USA Keywords: Elastic geomechanical model Vaca Muerta Formation Heterogeneity VTI Anisotropy abstract Accurate geomechanical evaluation of oil and gas reservoir rocks is important to provide design pa- rameters for drilling, completion and predict production rates. In particular, shale reservoir rocks are geologically complex and heterogeneous. Wells need to be hydraulically fractured for stimulation and, in complex tectonic environments, it is to consider that rock fabric and in situ stress, strongly influence fracture propagation geometry. This article presents a combined wellbore-laboratory characterization of the geomechanical properties of a well in El Trapial/Curamched Field, over the Vaca Muerta Formation, located in the Neuqu en Basin in Argentina. The study shows the results of triaxial tests with acoustic measurements in rock plugs from outcrops and field cores, and corresponding dynamic to static correlations considering various elastic models. The models, with increasing complexity, include the Isotropic Elastic Model (IEM), the Aniso- tropic Elastic Model (AEM) and the Detailed Anisotropic Elastic Model (DAEM). Each model shows advantages over the others. An IEM offers a quick overview, being easy to run without much detailed data for heterogeneous and anisotropic rocks. The DAEM requires significant amounts of data, time and a multidisciplinary team to arrive to a detailed model. Finally, an AEM suits well to an anisotropic and realistic rock without the need of massive amounts of data. 1. Introduction Shales are one of the most abundant sedimentary rocks in the earth's crust and constitute a large proportion of the clastic fill in sedimentary basins. In petroliferous hydrocarbon bearing basins, organic shales are the source rock for gas and petroleum generation and shales of all types can be seals to traps (Kuila et al., 2010). In Argentina, the Vaca Muerta Formation, located in the Neuqu en Basin, is growing in economic importance, being the second largest shale gas in proven reserves, and the fourth largest with respect to oil, according to the US Energy Information Administration (EIA, 2014 reports). Shale formations exhibit anisotropic properties due to their intrinsic lamination at various scales as well as the existence of microfractures at preferred orientations. Moreover, they exhibit large spatial heterogeneity because of the change in properties in all direction, meaning that the material properties change by location, especially in vertical direction (Mokhtari et al., 2014a,b). Anisotropy and heterogeneity affect various properties of shales such as tensile strength (Mokhtari et al., 2014a,b), compressive strength (Mokhtari et al., 2013a), permeability (Tutuncu and Mese, 2011; Tutuncu, 2012; Mokhtari et al., 2013b) and elastic (sonic) properties (Thomsen, 1986; Vernik and Nur, 1992; Wang, 2002; Tutuncu, 2010, 2012; and Mese and Tutuncu, 2011). Due to the anisotropy and heterogeneity, shale reservoirs, require detailed geomechanical characterization to obtain cost- effective drilling, completion and production. The degree of anisotropy or heterogeneity in transport and mechanical properties can result in different implications (Mokhtari et al., 2014a,b). Havens (2011), demonstrated how considering mechanical anisot- ropy could improve the estimation of minimum horizontal stress in the Bakken shale. Serejian and Ghassemi (2011) determined the * Corresponding author. E-mail address: sosamassaroagustin@gmail.com (A. Sosa Massaro).