Imaging the Foinaven ghost

Godfrey, Robert; Kristiansen, P.; Armstrong, Bill; Cooper, Mike; Thorogood, Ed

doi:10.1190/1.1820147

Cited by 26 publications

(7 citation statements)

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“…Having pressure information just above the seabed has been turned to an advantage for the separation of up-and downgoing (receiver-side ghost) waves using techniques such as "PZ summation" (Barr and Sanders, 1989;Soubaras, 1996;Schalkwijk et al, 1999); imaging using these separate components of the seismic data allows the reconstruction of the frequency band affected by the ghost notch effect (Godfrey et al, 1998;Grion et al, 2007;Dash et al, 2009). However, these additional data are often not used while performing migration, particularly during wavefield extrapolation: Receiver-side wavefields are generally obtained by backpropagation of particle velocity components at the receiver locations (Chang andMcMechan, 1986, 1994;Sun and McMechan, 1986;Yan and Sava, 2008).…”

Section: Ravasi and Curtismentioning

confidence: 99%

“…Several authors have used the receiver ghost for migration of ocean-bottom data (Godfrey et al, 1998;Ronen et al, 2005;Grion et al, 2007;Dash et al, 2009). Muijs et al (2007) make an early attempt to image using primary and free-surface multiples together: the final image contains crosstalk artifacts however; they are caused by interference of up-and downgoing waves not associated with the same subsurface reflector.…”

Section: Introductionmentioning

confidence: 98%

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Elastic imaging with exact wavefield extrapolation for application to ocean-bottom 4C seismic data

Ravasi

Curtis

2013

GEOPHYSICS

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A central component of imaging methods is receiver-side wavefield backpropagation or extrapolation in which the wavefield from a physical source scattered at any point in the subsurface is estimated from data recorded by receivers located near or at the Earth's surface. Elastic reverse-time migration usually accomplishes wavefield extrapolation by simultaneous reversed-time 'injection' of the particle displacements (or velocities) recorded at each receiver location into a wavefield modeling code. Here, we formulate an exact integral expression based on reciprocity theory that uses a combination of velocity-stress recordings and quadrupole-dipole backpropagating sources, rather than the commonly used approximate formula involving only particle velocity data and dipole backpropagating sources. The latter approximation results in two types of nonphysical waves in the scattered wavefield estimate: First, each arrival contained in the data is injected upward and downward rather than unidirectionally as in the true time-reversed experiment; second, all injected energy emits compressional and shear propagating modes in the model simulation (e.g., if a recorded P-wave is injected, both P and S propagating waves result). These artifacts vanish if the exact wavefield extrapolation integral is used. Finally, we show that such a formula is suitable for extrapolation of ocean-bottom 4C data: Due to the fluid-solid boundary conditions at the seabed, the data recorded in standard surveys are sufficient to perform backpropagation using the exact equations. Synthetic examples provide numerical evidence of the importance of correcting such errors.

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Section: Ravasi and Curtismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Elastic imaging with exact wavefield extrapolation for application to ocean-bottom 4C seismic data

Ravasi

Curtis

2013

GEOPHYSICS

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“…However, migration of the upgoing primary wavefield is not the best option for sparse receiver geometries. In such cases, OBS multiples can provide a better structural image of the subsurface from a wider angle and thus can be used for migration ͑Godfrey et al, 1998;Ebrom et al, 2000;Ronen et al, 2005;Grion et al, 2007͒. This is because downgoing receiver ghosts bounce from the same reflectors as the primary waves but farther away from the receiver station ͑Figure 1͒.…”

Section: Migrationmentioning

confidence: 95%

Wide-area imaging from OBS multiples

et al. 2009

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The subseafloor structure offshore western Canada was imaged using first-order water-layer multiples from oceanbottom seismometer ͑OBS͒ data and the results were compared to conventional imaging using primary reflections. This multiple-migration ͑mirror-imaging͒ method uses the downgoing pressure wavefield just above the seafloor, which is devoid of any primary reflections but consists of receiverside ghosts of these primary reflections. The mirror-imaging method employs a primaries-only Kirchhoff prestack depth migration algorithm to image the receiver ghosts. The additional travel path of the multiples through the water layer is accounted for by a simple manipulation of the velocity model and processing datum: the receivers lie not on the seabed but on a sea surface twice as high as the true water column. Migration results show that the multiple-migrated image provides a much broader illumination of the subsurface than is possible for conventional imaging using the primaries, especially for the very shallow reflections and sparse OBS spacing. The resulting image from mirror imaging has illumination comparable to the vertical incidence surface streamer ͑single-channel͒ reflection data.

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“…It is well known in OBC and OBN processing that the upgoing wavefield cannot build an unbiased image of the seafloor and of nearsurface reflectors (Figure 3). To get rid of this limitation, mirror imaging has been proposed (Godfrey et al, 1998;Grion et al, 2007). It consists of imaging the subsurface with the downgoing wavefield measured at the receiver.…”

Section: A R I N E a N D S E A B E D T E C H N O L O G Ymentioning

confidence: 99%

A large-scale validation of OBN technology for time-lapse studies through a pilot test, deep offshore Angola

Boëlle¹,

Brechet²,

Ceragioli³

et al. 2012

The Leading Edge

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In early phases of offshore field development, repeated marine seismic surveys recorded with towed streamers have been successfully processed to image changes in reservoir fluids through time and hence have contributed to important reservoir development decisions such as elaborating future production and injection plans. In such cases, the negative impact of surface or underwater obstacles on the final image has been mitigated using undershooting strategies. Nevertheless, even in the most favorable cases, this has been achieved at the expense of 4D repeatability because short-offset illumination is missing in the undershoot survey and the azimuthal distribution within the offset classes becomes inconsistent with the base streamer data. As the field development proceeds, especially in deep offshore contexts, a complex network of in-sea and subsea installations is progressively put in place and the Health, Safety, and Environmental (HSE) issues related to seismic vessels or recording cables coming close to production facilities can no longer be neglected, making the conventional streamer or OBC acquisitions challenging, or simply not feasible. As a result, industry is proposing a “sea-floor receiver” solution with ocean-bottom nodes (OBN) for imaging and monitoring reservoir production below infrastructures. OBN are autonomous seismic recording systems deployed on the seafloor with remotely operated vehicles (ROVs). Previous tests and studies (Boelle et al., 2005; Ceragioli et al., 2006) have shown that OBN technology may be appropriate for reservoir monitoring. Here we present the results of the first large-scale OBN project completed by Total E&P Angola, between September 2008 and April 2009, over the deep-water Dalia Field, Block 17, with the aim of validating the use of this technology for 4D seismic reservoir monitoring.

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Imaging the Foinaven ghost

Cited by 26 publications

References 0 publications

Elastic imaging with exact wavefield extrapolation for application to ocean-bottom 4C seismic data

Elastic imaging with exact wavefield extrapolation for application to ocean-bottom 4C seismic data

Wide-area imaging from OBS multiples

A large-scale validation of OBN technology for time-lapse studies through a pilot test, deep offshore Angola

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