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Ordonez A.,Petroleum Geo Services ASA | Ordonez A.,University of Oslo | Sollner W.,Petroleum Geo Services ASA | Kluver T.,Petroleum Geo Services ASA | Gelius L.J.,University of Oslo
Geophysics | Year: 2013

Migration of primary and multiple reflections leads to enhanced subsurface illumination and to increased image resolution. A joint migration approach using the complete wavefield requires properly imaged primaries and multiples of all orders. In recent works, primaries and multiples have therefore been imaged separately, using the upgoing and downgoing pressure wavefields obtained by decomposing dual-sensor streamer data. The matches between the corresponding depth images are still not found to be sufficiently accurate, so new and more appropriate imaging conditions need to be found. We reviewed the classical imaging approach used in one-way wave-equation migration, with the aim of extending it for simultaneous migration of primaries and all orders of multiples. Based on Rayleigh's reciprocity theorem and well-known theoretical developments, we derived a new imaging condition described in terms of the upgoing pressure wavefield and a filtered version of the downgoing vertical-velocity wavefield. To evaluate the efficiency of this new imaging approach, primaries and multiples were separately migrated using synthetic and real data examples. These results were compared to those obtained using a conventional imaging condition. We found that the use of the new imaging condition led to a better match between the depth images and spectra of the migrated primaries and migrated multiples. © 2014 Society of Exploration Geophysicists.

McKay A.J.,Petroleum Geo Services ASA | Widmaier M.,Petroleum Geo Services ASA | Bhuiyan A.H.,Petroleum Geo Services ASA | Beenfeldt J.,Petroleum Geo Services ASA | Engelmark F.E.,Petroleum Geo Services ASA
Shallow Anomalies Workshop: Indications of Prospective Petroleum Systems? | Year: 2014

Recent developments in broadband marine seismic and EM technology enables high-resolution imaging and improved characterisation of shallow anomalies. In particular, broad-band dual sensor seismic data enables separated wavefield imaging that produces high resolution images of the shallow sub-surface even when a wide 3D seismic spread is employed in shallow water. In addition, by using the full wavefield in, for example, full waveform inversion, shallow velocity variations associated with channels, pock-marks and gas-pockets can be imaged. By using a Towed Streamer EM system it is now possible to acquire Controlled Source Electromagnetic (CSEM) data simultaneously with seismic data using a single vessel. CSEM data enables the sub-surface resistivity to be determined, and the simultaneous acquisition enables CSEM data to be acquired efficiently, cost-effectively and early in the exploration cycle. By combining the high-resolution structural and velocity seismic images with images of sub-surface resistivity, it is possible to determine the origin, potential drilling hazard, and resource potential of shallow anomalies.

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