Diego Rovetta

Exploration beyond seismic: The role of electromagnetics and gravity gradiometry in deep water subsalt plays of the Red Sea

ABSTRACTThe Red Sea is characterized by thick salt sequences representing a seal for potential hydrocarbon accumulations within Tertiary formations deposited over deep basement structures. The Red Sea “salt” is characterized by halite concentrations embedded in layered evaporite sequences composed of evaporite and clastic lithologies. Salt complicates seismic exploration efforts in the Red Sea by generating vertical and lateral velocity variations that are difficult to estimate by seismic methods alone. In these conditions, the exploration challenges of independently imaging the subsalt section and provide enhanced velocity model building capabilities were addressed by a multigeophysics strategy involving marine electromagnetics (magnetotellurics and controlled source electromagnetics [CSEM]) and gravity gradiometry surveys colocated with wide azimuth seismic. Three-dimensional inversion of MT and CSEM is performed first with minimal a priori constraints and then by including variable amounts of interpret...

3D Seismic-gravity Simultaneous Joint Inversion for Near Surface Velocity Estimation

A novel 3D simultaneous joint inversion scheme for gravity and seismic travel time data is developed to solve for near-surface complex velocity distributions. The method incorporates industry-standard gravity and travel time inversion techniques while the joint inversion problem is solved by the introduction of various regularization functions about the model such as a-priori parameter distribution information, solution-space bounds, structural similarity via cross-gradient constraints and rock physics relations. The effectiveness of our joint inversion is demonstrated against a synthetic model representing a complex pattern of near-surface anomalies incorporating low and high velocity and density bodies. Results demonstrate the superiority of our approach where the shallow anomalies are better reconstructed by the joint inversion rather than that obtained by the single-domain inversions. The developed algorithm is tested with real data from Saudi Arabia acquired over a wadi structure. The results show a significant uplift of the time stack using the seismic-gravity joint inversion velocity model. The developed methodology is part of a multi-geophysics platform for near-surface velocity model building in complex geology scenarios.