GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.1 GNGTS 2024 Density values in the shallow crust: analysis and comparison of deep well data in the Adriatc region (Italy) M.T. Mariucci 1 , P. Montone 1 , P. Balossino 2 1 Isttuto Nazionale di Geofsica e Vulcanologia, Rome, Italy 2 Former ENI S.p.A. Natural Resources, Italy A detailed knowledge of rock densites helps in constraining the interpretaton of crustal structures and their modelling. This work presents the results of a frst systematc comparison between two datasets relatve to density data of geological formatons crossed by 13 deep wells. The wells are located in the Adriatc region and reach depths of over 5000 meters. The main lithologies involved include sedimentary rocks such as clays, sandstones, marls, evaporites, and carbonate rocks. The frst dataset concerns density values obtained from the analysis of sonic logs recorded along the wells, by applying the relaton proposed by Gardner et al. (1974). The second dataset refers to in situ density log measurements. We calculated the diferences among the values in the two datasets. The comparison of the densites obtained from various lithologies and geological formatons leads us to draw some inital consideratons regarding the applicability and accuracy of Gardner's formula in the area we analyzed. In the Plio-Quaternary formatons, characterized by clayey-sandy lithologies, the density values derived from sonic velocites are underestmated by at least 0.1 g/cm 3 with respect to the values measured by density logs. Whereas, densites of the carbonate sequences are overestmated by the same extent. Noteworthy, especially for gypsum units, the density estmates deviate from the real values, overestmatng by a factor of approximately 0.3 g/cm 3 . The results that we obtained emphasize the diferences in density values when using the Gardner formula and suggest the need for taking into account the possible errors in the specifc geological context or instead lithologies, such as those explored in this study. Since usually density values have to rely on evaluatons and not real measurements, we should try to obtain the best possible estmates. We think that contnuing in comparisons with as much data as possible of density log data and velocity-derived density data could produce also a numerical correcton to adapt the Gardner rule to the Italian area. References Gardner G.H.F., Gardner L.W., Gregory A.R.; 1974: Formaton velocity and density—the diagnostc basics for stratgraphic traps. Geophysics, 39, 770–780. Corresponding author: mariateresa.mariucci@ingv.it