The petroleum system in Central Italy and the Adriatic Sea is of great interest for future hydrocarbon exploration. However, major uncertainties remain about key risk elements such as source rock spatial distribution and maturation history, the timing of hydrocarbon migration, and the nature of migration pathways. This paper presents a new regional‐scale petroleum systems model based on an integrated inter‐disciplinary study which includes public‐domain subsurface data on key petroleum systems elements, heat‐flow and petroleum geochemical data, and an extensive set of 1D basin models. Results show the importance of the Mesozoic palaeogeographic and stratigraphic setting which was characterized by the presence of platform and basinal domains. Thermal data highlight an overall higher basal heat flow in platform domains which persist at the present‐day. Considering the geochemical and thermal characteristics of possible source rocks in the study area, the Upper Triassic Burano Formation appears to be the most likely active source rock but only in those geological domains where it has been deeply buried. In particular, source rocks reached maturity only during the most recent Apennine deformation phase in the late Pliocene/early Pleistocene, i.e. after the deposition of regional seals such as the Messinian Gessoso‐Solfifera Formation. Lateral migration is suggested to have occurred to explain most of the known oil accumulations. The margin of the Apulia Platform could have acted as a migration pathway for hydrocarbons, connecting basinal kitchens to the carbonate reservoir units at the top of the platform succession within which oil and gas accumulations have been proven. Heavy oils could represent early expulsion products from the source rock, but may also locally be a result of biodegradation due to recent partial exhumation of the traps and the loss of lighter components. The results of this study may support ongoing and future exploration efforts over other carbonate platforms in the study area, and more widely on carbonate targets elsewhere in the Mediterranean region.
<p>The Central Apennines fold-and-thrust belt (Central Italy) is characterized by the presence of several active faults, potentially capable of generating damaging earthquakes. To support seismic hazard studies over the area, a new 3D velocity model was built, integrating a wide range of surface and subsurface data.</p><p>The tectonic framework of the area (from Sulmona plain to Maiella Mt), is still debated in literature, also due to the lack of both an adequate geophysical data set and a reliable velocity model at the crustal scale.</p><p>In addition, the low number of seismic stations available for the acquisition of Vp/Vs arrival times, and the very low seismicity detected in the study area (the Sulmona and Caramanico Apennine valleys are considered as &#8220;seismic gaps&#8221;), lead to a difficult interpretation of the subsurface tectonic structures.</p><p>3D velocity modelling could well represent an important tool to support these deep crustal reconstructions as well earthquake relocation studies and could enhance the definition of seismogenic faults deep geometries, hence supporting a better risk assessment over the area of these potential locked faults.</p><p>Using the knowledge developed within the oil&gas industry as well in gas/CO<sub>2</sub> storage projects for the construction of 3D velocity models, extensively used to obtain subsurface imaging and define the geometry of the reservoirs and traps in the depth domain, a similar methodological approach was implemented over the study area.</p><p>The subsurface dataset was partially inherited by the past hydrocarbon exploration activities (e.g. seismic lines, exploration wells and sonic logs) and by the literature (e.g. time/depth regional models). Tomographic sections and relocated earthquake hypocentres were also integrated form geophysical studies. Geological maps (1:50.000 & 1:100.000 scale) represent the surface dataset that we used to create the surface interpretation of the regional geology.</p><p>As a first step, 18 2D balanced regional geological cross-sections, dip-oriented (W-E) across the Central Apennine, were built define the structural picture at regional scale. The cross-sections were built using MOVE (Petroleum Experts) and Petrel (Schlumberger) software. The following modelling step was the 3D model construction, in which the surface/subsurface data as well as all the geological sections were integrated in the final 3D structural and geological model.</p><p>The main geological layers reconstructed in the 3D model were than populated using the appropriated interval velocity values, building the final 3D velocity model in which the lateral velocity variation due to the presence of different facies/geological domains were considered.</p><p>As one of the results, we defined several 1D-velocity models coherent with the regional 3D velocity model, in which the key seismic stations and the earthquakes hypocentres dataset for the most potential seismogenic faults were included. 1D models were characterized by different degree of simplification, in order to test diverse approaches for the earthquake relocation. For this exercise, we used public dataset extracted by the analysis of microseismicity of the Sulmona basin.</p><p>We believe that the proposed approach can represents an effective method for combining geological and geophysical data to improve the subsurface and seismogenic faults interpretation, contributing to the seismic hazard assessment.</p>
<p>The Central Apennines is characterized by the presence of several active Plio-Quaternary normal faults, potentially capable of generating damaging earthquakes (as occurred in the recent past).</p><p>The seismicity registered for central Italy in the last 20 years by the seismic network of INGV (National Institute of Geophysics and Volcanology) highlights the presence of a regional seismic gap in the Sulmona and Caramanico Plio-Quaternary intermountain basins. In the study area, the magnitude of historical earthquakes ranges of from 5 to 6.8 Mw (from the 2nd century A.D. to 1933), while paleoseismological studies assigned a possible magnitude of 6.7 &#177; 0.1 to 4 earthquakes in the Sulmona basin (based on the fault length and the average of slip rate per event, estimated to be 1m). The high magnitude recorded for the destructive 1915 Avezzano earthquake (about 7 Mw), located in the Fucino basin (about 25 km to the west of the Sulmona basin), could suggest a similar potential seismic hazard also for the Sulmona and Caramanico normal faults. However, uncertainties remain on the activation mechanism related to the possible earthquake, expected in the study area. To reduce these uncertainties, we use a 3D modelling approach to perform a detailed calculation of the &#8220;active&#8221; rock volume of the hanging wall of the Sulmona and Caramanico faults (brittle volume), making an estimation of the possible maximum magnitude associated with these normal faults (testing different scenarios on the earthquake enucleation).</p><p>To reach this goal, a 3D structural and geological model was carried out starting from the available geological cartography, exploration wells, geophysical data (such as seismic sections and relocated earthquakes), and geological models from the literature. As a first step, several 2D balanced geological cross-sections were built across the Central Apennines to define the main structural picture at the regional scale (still discussed in literature). Cross-sections were built using MOVE (Petroleum Experts), while 3D modelling was completed using Petrel (Schlumberger) software. For the 3D modelling phase, the brittle-ductile transition (BDT) was used to localize the bottom of the potential brittle volumes at depth (assumed as maximum depth of the hypocenter). Following this methodology, the maximum magnitudes were estimated of the Sulmona (7.1 Mw, BDT at 17 km) and Caramanico (7.2 Mw, BDT at 20 km) normal faults. With the aim of simulating a more conservative scenario, the effects of a possible shallower structural cut-off for the Sulmona (8 km) and Caramanico (10 km) areas were investigated. The resulting reduced brittle volumes led to lower magnitude values estimate (6.6 Mw for the Sulmona, and 6.8 Mw for the Caramanico faults).</p><p>This approach allowed to make an estimate of the expected magnitudes for future seismic events associated to the Sulmona and Caramanico regional extensional faults, considering two different fault activation models (because of the regional structural uncertainties). Our work also demonstrates the importance of implementing robust 3D geological models to support seismogenic potential evaluation and seismic hazard studies.</p>
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