IMPROVING BASEMENT DEPTH MAPPING USING JOINT 3D INVERSION OF MT PHASE AND AMPLITUDE

Abstract

Summary Electromagnetic methods are established tools alongside gravity and magnetics for non-seismic mapping of crystalline basement. Accurately mapping the boundary between sedimentary cover rocks and the crystalline basement has implications for hydrocarbon prospectivity of a basin. We apply 3D joint inversion of MT amplitude and phase data to image and resolve an observed discrepancy between basement depth interpreted from seismic and that from independent gravity and magnetic 2D modelling in offshore Borneo. We performed an unconstrained 3D inversion of the available marine MT datasets using CGG’s RLM3D inversion code. The 3D MT inversion result suggests a basement structure different from those previously interpreted using 2D structural restoration from seismic image and 2D potential field inversion. We suggest that 3D inversion is required for such complex terrains.