Anatomy and kinematic evolution of an ancient passive margin involved into an orogenic wedge (Western Southern Alps, Varese area, Italy and Switzerland)

We make use of own geological mapping, interpretations of seismic reflection profiles and deep geophysical data to build a lithospheric-scale cross-section across the European Western Southern Alps (Varese area) and to model a progressive restoration from the end of Mesozoic rifting to present-day. Early phases of Alpine orogeny were characterized by Europe-directed thrusting, whereas post-Oligocene shortening led to basement-involving crustal accretion accompanied by backfolding, and consistent with the kinematics of the adjoining Ivrea Zone. Wedging was favored by a significant component of reactivation of the inherited Adriatic rifted margin. Our results also suggest that, during the collisional and post-collisional tectonics, lithosphere dynamics drove diachronically the onset of tectonic phases (i.e., wedging and slab retreat), from east to west, across the Western Southern Alps

RESERVOIR MODELLING AND UNCERTAINTY EVALUATION BY MEANS OF ALTERNATIVE STRUCTURAL SCENARIOS: THE ACCETTURA FIELD CASE OF STUDY (S. APENNINES, ITALY)

The goal of this dissertation is to quantitatively explore the uncertainties generated by the combination of geological information, seismic and wells and production data, linked to the building of static reservoir models. To face the evaluation of uncertainties, we adopt a multistep workflow: combining possible stratigraphic and structural interpretations in discrete scenarios; performing a 2D sequential restoration, generating alternative 3D models populated with reservoir properties and associated uncertainties. Alternative models have been then compared with production history, in order to check the consistency of the assumed models. The considered case of study is the Accettura Gas Field (AGF), located within the Garaguso Concession (held by Edison E&P) in the Bradanic Foredeep (BF) of the southern Apennines. We have considered unexplored structural solutions in order to figure out alternative scenarios on the structural control of the gas field. Four alternative scenarios of static reservoir models have been built for AGF and structural validation by balanced cross-sections across the BF were performed. A global uncertainty evaluation of the proposed scenarios was performed using stochastic techniques. The results show that the choice of structural model and the petrophysical properties impact the hydrocarbon deterministic and probabilistic volumetric assessment (Gas Initially In Place - GIIP) that affect both the estimate of mean volume and the range of uncertainty

Frontal accretion vs. foreland plate deformation: discriminating the style of post-collisional shortening in the Apennines

Interpretation of confidential and public data was carried out in this study focusing on the structural setting and seismic stratigraphy of both foreland basin deposits and underlying shallow water carbonates of the foreland plate. Our structural interpretation, supported by accurate depth conversion of the seismic data and 2D restoration, reveals how the style of deformation of the foreland carbonate platform is dominated by positive inversion involving the oblique-slip reactivation of high-angle, inherited extensional faults rooted below the base of the carbonate succession. Rather than thrust accretion involving the foreland carbonate platform postulated by thin-skinned thrusting models, the observed structures record post-collisional foreland plate deformation associated with the far-field transmission of compressive stresses. Plio-Pleistocene foreland shortening resulted in the formation of segmented positive flower structures arranged in a right-stepping en-\ue9chelon pattern and in the coeval development of bending-moment faults accommodating arc-parallel extension in the growing anticlines. Our results emphasize the importance of Permo-Triassic extensional faults during later shortening, reducing on the other hand the role locally played by forebulge-and foreland plate flexuring-related normal faults in inversion structures involving the foreland carbonate platform. Oblique-slip faulting with substantial strike-slip components of motion and associated positive structures exerted a significant control in the development of structural traps and related hydrocarbon accumulation in the deformed foreland plate