S U M M A R YGravitational signatures of subduction are a major feature of the Earth's gravity pattern, being visible as lineaments parallel to the arc-trench systems. The novelty of our study resides in the simulation of this subduction fingerprint via a newly developed dynamic subduction model based on the finite-element approach, which includes the compositional stratification of the lithosphere into a light upper crust and a dense lithospheric mantle. Crustal material sinks in the mantle in proximity to the top of the slab due to the viscous dragging forces and off-scraping of the overriding plate. We show that the sinking of light crustal material from both the subducting and overriding plates to depths of the order of 200 km may be responsible for a trough of about 100 MGal extending 100-200 km in a direction perpendicular to the trench. This anomaly is superimposed on a global positive gravity anomaly due to thermal contraction of the mantlelithosphere system. The negative gravity anomaly due to compositional stratification of the crust has comparable magnitude and horizontal extent of that due to the negative dynamic topography of the trench. The gravity patterns from compositional stratification of the crust and from dynamic trench topography are evaluated for different tectonic subduction styles related to active convergence, with and without roll-back. In general, we found that case without roll-back produces a broader and smoother dynamic topography gravity anomaly than with roll-back, while the gravity signature from compositional stratification is less sensitive to the style of subduction.

Numerical modelling of the Aegean and Calabrian subductions using geological reconstructions starting 75–80 Myr before the present reproduces the present‐day geometries of the slabs and mantle wedges imaged by seismic tomography. The change from a shallow subduction dip of about 15° from the surface to a depth of 200 km into a dip of 60° below this depth in the Aegean subduction is caused by the south‐west migration of the trench at the velocity of 3 cm/yr, obtained from GPS and geological data. The largest dip of 70° Calabrian subduction is caused by the termination of the active phase of opening of the Tyrrhenian back‐arc basin and by the essentially purely gravitational sinking of the slab, in agreement with the null trench‐migration velocity obtained from GPS data in Calabria. These two different tectonic settings are the ultimate causes of the different styles of seismicity within the two subduction complexes.

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Time-lapse or 4D methodology, that uses repeated 3D seismic surveys to monitor fluids saturations changes in reservoir, is a recommended tool for reservoir management in particular in deepwater fields where additional investments must be carefully evaluated due to the associated costs.This paper presents a real case of a successful rejuvenation project of a deepwater field in West Africa, supported by integrated 4D and reservoir 3D studies. The field, located in 800 m of water depth, has been producing for 10 years with a rate currently equal to the half of the FPSO nameplate capacity. In 2010 a seismic acquisition specifically designed for 4D purposes was executed and, integrated with the historical production data, led to a revision of the levels' potentiality. Reservoir barriers and fluids movements, water and gas in particular generated by the injection, have been modeled based on 4D acoustic impedance differences and were supported by history matching on the dynamic model. The strongly integrated approach supported a volumes in place revision that drove a sidetrack campaign on two wells to reach undrained areas. The integrated study highlighted also the possible risk of water encroachment on one of the targets of the two wells, that was therefore considered as a secondary target in the sidetrack plan. The result of the drilling campaign, combined with near field exploration, confirmed the expectations and contributed to double the production back to the initial peak plateau rate. Lesson learnt on this successful integration among disciplines are presented.