Nanoindentation has arisen as a promising technique to geomechanically characterize small cutting samples obtained during drilling a well. This technique is a useful tool to characterize unconventional reservoirs during the exploration phase. While we have previously analyzed cutting rock samples from Palermo Aike Fm. (Austral-Magallanes Basin, Argentina) in which not enough data was available to cross check the technique, we now analyze Vaca Muerta Fm. (Neuquen Basin, Argentina) core rock samples that have a thoughtful geomechanical characterization. In this work we compare the properties obtained by nanoindentation to those obtained from a validated geomechanical model. Additionally, we compare nanoindentation data with laboratory tests obtained by static and dynamic experiments at plug scale. The results show that the elastic modulus obtained by nanoindentation matches the elastic modulus obtained with ultrasonic wave test under high confining pressure. Furthermore, it correlates to the ones obtained by triaxial compressive tests as well as with the modulus obtained from a calibrated geomechanical model. Additionally, good correlation is also seen when hardness data from nanoindentation is compared with uniaxial compressive strength (UCS) measured in plugs and with scratch resistance from core samples, but in a different order of magnitude. Using the elastic modulus and hardness obtained from nanoindentation we were able to screen data equivalent to confined dynamic Young modulus, UCS and scratch resistance measured in the cores. Therefore, nanoindentation in cutting is a cheap method to obtain mechanical properties when information or samples are not available, valuing cutting samples obtained prior to drilling new wells and getting cores and logs. Furthermore, it could be useful to determine the variations of these properties in horizontal wells where sonic logs are expensive and difficult to run.
Exploration projects often rely on drill cuttings as the sole source of rock samples from a given area of interest. However, estimating the mechanical properties of these cuttings is a challenge due to the small sizes of the samples. Fortunately, the nanoindentation technique can overcome this issue, as demonstrated by several studies (Shukla et al., 2013; Glover et al., 2016; Ma et al., 2020). This method allows the determination of the indentation modulus, hardness, and fracture toughness of rock samples using a small amount of material from the measurement of load-displacement curves. Previous research has shown that there is a strong correlation between the indentation modulus and the dynamic Young modulus (Kumar et al., 2012; Dang et al., 2017; Celleri et al., 2020, Noya et al., 2021), indicating that the former can be used to describe the elastic behavior of rock samples during dynamic tests at high confining pressures.
