Dirk-Jan van Manen

On the use of multicomponent streamer recordings for reconstruction of pressure wavefields in the crossline direction

Three-component measurements of particle motion would bring significant benefits to towed-marine seismic data if processed in conjunction with the pressure data. We show that particle velocity measurements can increase the effective Nyquist wavenumber by a factor of two or three, depending on how they are used. A true multicomponent streamer would enable accurate data reconstruction in the crossline direction with cable separations for which pressure-only data would be irrecoverably aliased. We also show that conventional workflows aimed at reducing these aliasing effects, such as moveout correction applied before interpolation, are compatible with multicomponent measurements. Some benefits of velocity measurements for deghosting data are well known. We outline how the new measurements might be used to address some long-standing deghosting challenges of particular interest. Specifically, we propose methods for recovering de-ghosted data between streamers and for 3D deghosting of seismic data at the stream...

Interferometric modeling of wave propagation in inhomogeneous elastic media using time reversal and reciprocity

Time reversal of arbitrary, elastodynamic wavefields in partially open media can be achieved by measuring the wavefield on a surface surrounding the medium and applying the time reverse of those measurements as a boundary condition. We use a representation theorem to derive an expression for the time-reversed wavefield at arbitrary points in the interior. When this expression is used to compute, in a second point, the time-reversed wavefield originating from a point source, the time-reversed Green’s function between the two points is observed. By invoking reciprocity, we obtain an expression that is suitable for modeling of wave propagation through the medium. From this we develop an efficient and flexible two-stage modeling scheme. In the initial phase, the model is illuminated systematically from a surface surrounding the medium using a sequence of conventional forward-modeling runs. Full waveforms are stored for as many points in the interior as possible. In the second phase, Green’s functions between ...

Crossline wavefield reconstruction from multicomponent streamer data: Part 2 — Joint interpolation and 3D up/down separation by generalized matching pursuit

Computation of the 3D upgoing/downgoing separated wavefield at any desired position within a marine streamer spread is enabled by multicomponent streamers that can measure the crossline and vertical components of water-particle motion in addition to the pressure. We introduce the concept of simultaneous interpolation and deghosting and describe a new technique, generalized matching pursuit (GMP), to achieve this. This method is based on the matching-pursuit technique and iteratively reconstructs the signal as a combination of optimal basis functions. In the GMP method, the basis functions describing the unknown 3D upgoing wavefield are filtered by appropriate forward ghost operators before being matched to the multicomponent measurements. As a data-dependent method, GMP can operate on data samples that are highly aliased in the crossline direction without relying on assumptions about seismic events such as linearity. The technique is naturally suitable for data with only a small number of samples that may be irregularly spaced. We demonstrate the efficacy and robustness of the GMP method on several synthetic data sets of increasing complexity and in the presence of noise.

Interferometric ground-roll removal: Attenuation of scattered surface waves in single-sensor data

Land seismic data are contaminated by surface waves (or ground roll). These surface waves are a form of source-generated noise and can be strongly scattered by near-surface heterogeneities. The resulting scattered ground roll can be particularly difficult to separate from the desired reflection data, especially when this scattered ground roll propagates in the crossline direction. We have used seismic interferometry to estimate scattered surface waves, recorded during an exploration seismic survey, between pairs of receiver locations. Where sources and receivers coincide, these interreceiver surface-wave estimates were adaptively subtracted from the data. This predictive-subtraction process can successfully attenuate scattered surface waves while preserving the valuable reflected arrivals, forming a new method of scattered ground-roll attenuation. We refer to this as interferometric ground-roll removal.

Exact wave field simulation for finite-volume scattering problems.

An exact boundary condition is presented for scattering problems involving spatially limited perturbations of arbitrary magnitude to a background model in generally inhomogeneous acoustic media. The boundary condition decouples the wave propagation on a perturbed domain while maintaining all interactions with the background model, thus eliminating the need to regenerate the wave field response on the full model. The method, which is explicit, relies on a Kirchhoff-type integral extrapolation to update the boundary condition at every time step of the simulation. The Greens functions required for extrapolation through the background model are computed efficiently using wave field interferometry.

On data-independent multicomponent interpolators and the use of priors for optimal reconstruction and 3D up/down separation of pressure wavefields

In marine acquisition, the interference between the upgoing and downgoing wavefields introduces a receiver ghost which reduces the effective bandwidth of the seismic wavefield. A two-component streamer provides means for removing the receiver ghost by measuring pressure and vertical particle velocity. However, due to nonuniform and relatively sparse sampling in the crossline direction, the seismic data are usually severely aliased in the crossline direction and the deghosting may not be feasible in a true 3D sense. A true multicomponent streamer measures all components of the particle motion wavefield in addition to the pressure wavefield. This enables solving the 3D deghosting and crossline reconstruction problems simultaneously, without making assumptions on the wavefield or the subsurface. We havedeveloped two data-independent algorithms suited for multicomponent acquisition. The first algorithm reconstructs the total pressure wavefield in the crossline direction by using the pressure and the crossline...

Introduction to the supplement on seismic modeling with applications to acquisition, processing, and interpretation

Modeling of seismic wave propagation plays a key role in almost every aspect of exploration seismology. Fundamentally, it provides a means of understanding the character of recorded seismic data. Although analytical or semianalytical solutions exist for several canonical models, those are often insufficient to explain the full plethora of phenomena that arise in complex heterogeneous earth models governed by, e.g., anisotropic, viscoelastic, or poroelastic rheologies. Typical manifestations of such complex phenomena that are observed widely in surface seismic data include scattering, generation of multiples, and interface waves. Another application area of seismic modeling is survey evaluation and design, in which different acquisition geometries and subsurface model hypotheses are assessed to choose an optimal acquisition and processing strategy. A recent example in which seismic modeling is having a significant impact and proving to be a valuable tool is 3D wide-azimuth acquisition design in high-risk, high-reward ultra-deepwater exploration scenarios (see, for instance, contributions in this supplement).

Immersive experimentation in a wave propagation laboratory

A wave propagation laboratory is proposed which enables the study of the interaction of broadband signals with complex materials. A physical experiment is dynamically linked to a numerical simulation in real time through transmitting and recording transducer surfaces surrounding the target. The numerical simulation represents an arbitrarily larger domain, allowing experiments to be performed in a total environment much greater than the laboratory experiment itself. Specific applications include the study of non-linear effects or wave propagation in media where the physics of wave propagation is not well understood such as the effect of fine scale heterogeneity on broadband propagating waves.

Deconvolution imaging conditions and cross-talk suppression

Deconvolution imaging conditions offer improved resolution over standard, crosscorrelation-based imaging conditions. Additionally, these imaging conditions produce a result more directly related to a reflection coefficient than do crosscorrelation-based imaging conditions. In simple analytical cases, deconvolution imaging conditions also offer the possibility of eliminating crosstalk (i.e., energy in the image due to reflected energy arriving at a location at the same time as incident energy that did not cause the reflected energy) when the full up- and down-going wavefields are used. This means that in such cases, surface-related multiples can be eliminated from the image, or that multiple shots could potentially be fired simultaneously without degrading the image. However, this cross-talk-suppression property is not observed in most situations. We show that this is due to a number of issues: the correct order of deconvolution must be used, stabilization causes imperfect deconvolution, finite apertures lead to some of the signal being lost, and an assumption of horizontal stratification is often not being met. Further, imperfect knowledge of the incident and reflected field due to such factors as anisotropy, poorly estimated velocity fields, and measurement noise can also lead to imperfect deconvolution. Thus, deconvolution imaging conditions should not be counted on to completely eliminate crosstalk from images.

Mitigation of streamer noise impact in multicomponent streamer wavefield reconstruction

where ρ is the density of the medium. It is known (Linden, 1959) that the crossline component of the pressure gradient, Py, gives an important contribution in recovering from the cross-line aliasing, allowing the multi-channel reconstruction in the crossline direction of the seismic pressure. The MIMAP technique (Multichannel Interpolation by Matching Pursuit, Vassallo et al., 2010), has been proposed to exploit the anti-aliasing potential of two-component seismic data, P and Py, in realistic acquisition settings. It has also been discovered that the combined use of pressure, crossline and vertical component of the pressure gradient, P, Py and Pz, gives even more benefit, as it allows joint-interpolation and 3D deghosting of severely aliased data (Ozbek et al., 2010). Ozbek et al. (2010) introduced Generalized Matching Pursuit (GMP) as a technique to achieve this. Both MIMAP and GMP rely on the combination of measurements of different nature: in this paper we describe how this combination needs to take into account the differences between the signals and the noise characteristics that are observed on multicomponent marine measurements.