Massimiliano Vassallo

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...

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.

Crossline wavefield reconstruction from multicomponent streamer data: Part 1 — Multichannel interpolation by matching pursuit (MIMAP) using pressure and its crossline gradient

We introduce a technique that uses multicomponent seismic measurements to reconstruct the seismic wavefield at any desired crossline position between towed streamers. This method, called multichannel interpolation by matching pursuit (MIMAP), operates on pressure and crossline particle-motion measurements. It is based on the matching-pursuit technique and iteratively reconstructs the signal as a combination of optimal basis functions. Being a data-dependent technique, MIMAP can interpolate severely aliased data without assumptions about seismic events such as linearity or the model related to the seismic wavefield. MIMAP has the capability to perform well in the presence of irregular sampling and is robust when only a small number of samples are available. Using synthetic data examples, we show that the new method has the potential to interpolate signals that are sampled at realistic crossline streamer spacing and in the presence of noise.

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...

Matching Pursuit Methods Applied to Multicomponent Marine Seismic Acquisition – The Issue of Crossline Aliasing

In this work we analyze the theoretical aspects of spatial aliasing in the crossline direction in marine seismic acquisition. We also explain the benefits of the additional measurements acquired by a multicomponent towed streamer, able to measure the three components of the particle velocity vector in addition to the pressure wavefield. We propose matching pursuit based techniques to reconstruct a 3D full bandwidth seismic wavefield on a fine receiver grid. The techniques that we describe process multicomponent seismic data; they calculate the desired 3D wavefield with satisfactory quality despite the severe aliasing that affects each of the individual input measurements in the crossline direction.

Parametric Matching Pursuit Methods to Reconstruct Seismic Data Acquired with Multichannel Sampling

In marine seismic data acquisition, multichannel sampling can occur in various scenarios, including over/under streamers, multicomponent streamer, and multicomponent ocean-bottom node. In these various multichannel sampling scenarios, each channel outputs samples of a filtered version of a seismic wavefield. These filters are different for each channel; the data are often coarsely and irregularly sampled. The objective is to reconstruct the unknown wavefield from the multichannel samples. In this paper, we discuss how parametric matching pursuit methods can be extended to solve such reconstruction problems. We give two examples based on data that a multicomponent streamer could record and show the form the reconstruction problem takes when two- and three-component data are available.

Reverse-time Imaging of Dual-source 4C Marine Seismic Data Using Primaries, Ghosts, and Multiples

Novel technologies in marine seismic data acquisition allow for the recording of full vectoracoustic (VA) data: four-component recordings (pressure and three-component acceleration) of fields excited both by pressure-only as well as dipole/gradient sources. Here we present a wave-equation, nonlinear, reverse-time imaging method that takes full advantage of acoustic dual-source (monopole and dipole sources) multi-component data. The method’s formulation relies on source-receiver scattering reciprocity relations that make proper use of VA fields both in the wavefield extrapolation and imaging condition steps in a self-consistent manner. The new VA imaging method is capable of simultaneously focusing energy from upgoing and both receiver- and sourceside ghost arrivals, while jointly using information fromprimaries and multiples contained in each of these fields. Additionally, VA imaging handles image amplitudes better than conventional reversetime migration because it does not require far-field radiation assumptions, properly handling finite-aperture directivity information directly from dual-source four-component data. While the method does not require any deghosting as a preprocessing step, it can use previously separated up and downgoing fields to generate independent subsurface images. This allows for new approaches in the design of marine seismic acquisition. We demonstrate the method using synthetic examples, which include complex stratigraphic and structural subsurface features.

Anti-alias Optimal Interpolation with Priors

We introduce a new technique referred to as Optimal Interpolation with Priors, or OIP, for interpolation of irregularly sampled signals, using prior estimates of their spectral content, which is optimal in the least square sense. In this paper, after introducing this technique and describing its basic advantages with respect to other state of the art regularization techniques, we demonstrate its potential to interpolate signals that are spatially aliased, based on realistic prior information. We also propose an algorithm to obtain a reliable prior estimate of the signal spectrum. The combined use of this algorithm and OIP, referred to henceforth as Anti-Alias OIP (AA-OIP), can be applied to datasets irregularly sampled in multi-dimensional spaces.

On the Role of Priors in Generalized Matching Pursuit to Reconstruct Wavefields from Multicomponent Streamer Data

In conventional single-component data acquisition, a common way to solve the problem of reconstructing aliased seismic data is to use priors that are computed at low frequencies and applied at high frequencies. In contrast, parametric matching pursuit methods such as Generalized Matching Pursuit applied on multicomponent data do not need priors in most conditions to achieve accurate reconstruction under aliasing. In this paper, we examine how and when soft priors can provide further robustness to multichannel matching pursuit algorithms. We illustrate our concepts on synthetic data generated by finite-difference modelling and on data acquired by a 3D-4C towed cable array. We find that multicomponent data allow matching pursuit algorithms to compute and use the priors in ways that are not possible with single-component data. For instance, the priors can be estimated by matching pursuit within an intermediate temporal frequency band, where the signal-to-noise ratios of all the components are high, while the data are already subject to spatial aliasing. The priors generated at these intermediate frequencies can then be used at higher frequencies where the aliasing is stronger, and also at lower frequencies, still aliased and affected by stronger noise.

Crossline Wavefield Reconstruction From Multi-component Streamer Data: Multichannel Interpolation By Matching Pursuit

We introduce a new technique that uses multicomponent seismic measurements that would be recorded by a true multicomponent streamer to reconstruct the seismic wavefield at any desired position between streamers. This method, called Multichannel Interpolation by Matching Pursuit (MIMAP), operates on pressure and crossline particle motion measurements. As a data-dependent technique, MIMAP can interpolate severely aliased data without any assumptions about seismic events such as linearity or the model related to the seismic wavefield. MIMAP has the capability to perform well in the presence of irregular sampling and is robust even when only a small number of samples are available.