Laboratory rock characterization is fundamental in helping understand the subsurface, its components and thereafter infer where and how to proceed with the extraction of hydrocarbons. Well logging tools are equally important and should be considered complementary to laboratory results. In this work we propose an integrated and innovative laboratory methodology focused on non-destructive characterization and minimizing the amount of sample required. The full methodology includes petrophysical, mineralogical and geochemical characterization. Results on total and effective porosity will be presented, compared and validated with well logs from three different wells in oil window, corresponding to the Vaca Muerta formation.
The oil and gas industry relies on petrophysical studies to make important economic decisions and guide the extraction process. This information can be obtained in situ using well logging tools (Coates 1999), or in the lab by extracting rock samples (cores, rotary sidewall plugs, outcrops, or cuttings). Complete characterization of conventional reservoirs is somewhat a standard practice and there is even a recommended practice for core analysis (API RP 40). On the other hand, unconventional plays, in particular shale rocks with heterogenous lithologies and presence of organic matter still represent a challenge. Thus, there is a requirement in the industry to develop innovative characterization workflows.
Laboratory analysis requires the extraction of rock samples from the subsurface, which is a very time consuming and expensive process. The value of rock samples favors the development of characterization techniques that are non-destructive and require less amount of rock (Masiero 2022). With this in mind, we present petrophysical results obtained on rock samples from three different wells from the Vaca Muerta Formation. This formation is a marine source rock with the following characteristics: average TOC content 1-8%; moderate depths of 3150 m; overpressure between 47-61 MPa; no expandable clays in mature areas; and different landing zones for oil, wet and dry gas production (Brisson 2020, Dominguez 2019, Sagasti 2014, Spacapan 2021, Uliana 1993,).
The focus is set on correctly measuring total and effective porosity, using the least amount of sample possible and with non-destructive experiments. Porosity is one of the most important rock properties, allowing for the estimation of hydrocarbon reserves and thus value a formation, basin or well.
