Basin scale, high-resolution 3D facies modeling of tectonically-confined turbidites: An example from the Firenzuola System (Marnoso-arenacea Formation, northern Apennines, Italy)

Facies modeling is an important step in reservoir characterization, because each facies is related to specific petrophysical properties, and the assessment of their spatial arrangement is key for hydrocarbon recovery estimations. Most datasets related to subsurface sedimentary basins in exploration areas are limited to seismic resolution, which is lower than the actual thickness range of the beds in most depositional systems. In that way, detailed studies carried out in the outcropping area of collisional margins can be used as analogs of subsurface reservoirs with similar geologic settings in order to better predict heterogeneities and properties distribution, with no limitation of resolution. This study provides an experimental 3D high-resolution facies model based on 5,500m (about 18,000ft) of bed-by-bed measurements divided into seven stratigraphic logs, collected over several years of field studies in the Marnoso-arenacea Formation (MAF, northern Apennines, Italy). It focuses on the upper Serravallian Firenzuola turbidite system, which was deposited in a highly confined inner foredeep during an important phase of growth and propagation of the Monte Castellaccio thrust and Verghereto high. The syn-sedimentary activity of these tectonic structures deeply affected sediment dispersal patterns and facies distribution of the inner foredeep that became, in the final narrowing phase, a piggyback-type basin and induced the coeval shift of the main depositional area to an outer and relatively wider basin representing the new depocenter of the MAF foredeep. The modeling has provided quantitative analysis of turbidite facies trends and a numerical dataset suitable for further geostatistical and petrophysical studies.