ABSTRACT:

The Vaca Muerta formation has been under study as a potential shale reservoir since approximately 2007; however, the first well, targeting this formation, was drilled in 2010. During the last few years, many works showing different discoveries about Vaca Muerta mechanical rock properties have been published. All of them are an invaluable piece of work; nevertheless, they do not give a full characterization of Vaca Muerta mechanical rock properties. Until today, many meters of core samples were recovered from Vaca Muerta formation and a complete set of rock mechanics laboratory tests have been performed on core plugs to accurately characterize all the parameters that governs the mechanical behavior of the rock. In addition, to further understand the variability in the mechanical response of the rock, changes in the setting up of the laboratory tests were done in similar plugs on a same core sample (sister samples). It is the aim of this paper to present an overview of recent Vaca Muerta research works which include mechanical laboratory characterization of the rock and discuss about how different laboratory test parameters such as temperature, confining pressure, time, and fluid saturation among others affects the mechanical response of the rock. To complete the understanding of the Vaca Muerta formation mechanical behavior, special laboratory studies like Biot's coefficient and creep test were performed in some core shale gas samples; nevertheless, in this work, the quality and validity of these results are left as an open discussion. The most important conclusion of the analysis done in this work is that some elastic properties are not mainly controlled by the “rock families or facies”. As a result, a unique correlation between many elastic properties has been found and a simple workflow to fully characterize the rock mechanical properties of Vaca Muerta formation is proposed.

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