Full-waveform inversion of variable-depth streamer data: An application to shallow channel modeling in the North Sea

Wide-azimuth long-offset ocean bottom cable (OBC)/ocean bottom node surveys provide a suitable framework to perform computationally efficient frequency-domain full-waveform inversion (FWI) with a few discrete frequencies. Frequency-domain seismic modeling is performed efficiently with moderate computational resources for a large number of sources with a sparse multifrontal direct solver (Gauss-elimination techniques for sparse matrices). Approximate solutions of the time-harmonic wave equation are computed using a block low-rank (BLR) approximation, leading to a significant reduction in the operation count and in the volume of communication during the lower upper (LU) factorization as well as offering great potential for reduction in the memory demand. Moreover, the sparsity of the seismic source vectors is exploited to speed up the forward elimination step during the computation of the monochromatic wavefields. The relevance and the computational efficiency of the frequency-domain FWI performed in the viscoacoustic vertical transverse isotropic (VTI) approximation was tested with a real 3D OBC case study from the North Sea. The FWI subsurface models indicate a dramatic resolution improvement relative to the initial model built by reflection traveltime tomography. The amplitude errors introduced in the modeled wavefields by the BLR approximation for different low-rank thresholds have a negligible footprint in the FWI results. With respect to a standard multifrontal sparse direct factorization, and without compromise of the accuracy of the imaging, the BLR approximation can bring a reduction of the LU factor size by a factor of up to three. This reduction is not yet exploited to reduce the effective memory usage (ongoing work). The flop reduction can be larger than a factor of 10 and can bring a factor of time reduction of around three. Moreover, this reduction factor tends to increase with frequency, namely with the matrix size. Frequency-domain viscoacoustic VTI FWI can be viewed as an efficient tool to build an initial model for elastic FWI of 4C OBC data.

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Application of Full Waveform Inversion to variable-depth streamer data

10.1190/segam2012-0613.1 ◽

2012 ◽

Cited By ~ 3

Author(s):

Richard Jupp ◽

Andrew Ratcliffe ◽

Richard Wombell

Keyword(s):

Waveform Inversion ◽

Full Waveform Inversion ◽

Variable Depth ◽

Full Waveform ◽

Streamer Data

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Full-waveform inversion in a shallow water environment: A North Sea 3D towed-streamer data example

10.1190/segam2013-1310.1 ◽

2013 ◽

Author(s):

Kathy Zou ◽

Lars Tore Langlo ◽

Grunde Rønholt ◽

Jaime Ramos-Martinez ◽

Steve Kelly

Keyword(s):

Shallow Water ◽

North Sea ◽

Waveform Inversion ◽

Water Environment ◽

Full Waveform Inversion ◽

Full Waveform ◽

Shallow Water Environment ◽

Streamer Data

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A parameterization study for elastic VTI full-waveform inversion of hydrophone components: Synthetic and North Sea field data examples

Geophysics ◽

10.1190/geo2017-0073.1 ◽

2017 ◽

Vol 82 (6) ◽

pp. R299-R308 ◽

Cited By ~ 11

Author(s):

Antoine Guitton ◽

Tariq Alkhalifah

Keyword(s):

North Sea ◽

Waveform Inversion ◽

Transversely Isotropic ◽

Horizontal Velocity ◽

Full Waveform Inversion ◽

Ocean Bottom ◽

S Wave ◽

Data Set ◽

Full Waveform ◽

Streamer Data

Choosing the right parameterization to describe a transversely isotropic medium with a vertical symmetry axis (VTI) allows us to match the scattering potential of these parameters to the available data in a way that avoids a potential tradeoff and focuses on the parameters to which the data are sensitive. For 2D elastic full-waveform inversion in VTI media of pressure components and for data with a reasonable range of offsets (as with those found in conventional streamer data acquisition systems), assuming that we have a kinematically accurate normal moveout velocity ([Formula: see text]) and anellipticity parameter [Formula: see text] (or horizontal velocity [Formula: see text]) obtained from tomographic methods, a parameterization in terms of horizontal velocity [Formula: see text], [Formula: see text], and [Formula: see text] is preferred to the more conventional parameterization in terms of [Formula: see text], [Formula: see text], and [Formula: see text]. In the [Formula: see text], [Formula: see text], and [Formula: see text] parameterization and for reasonable scattering angles (<[Formula: see text]), [Formula: see text] acts as a “garbage collector” and absorbs most of the amplitude discrepancies between the modeled and observed data, more so when density [Formula: see text] and S-wave velocity [Formula: see text] are not inverted for (a standard practice with streamer data). On the contrary, in the [Formula: see text], [Formula: see text], and [Formula: see text] parameterization, [Formula: see text] is mostly sensitive to large scattering angles, leaving [Formula: see text] exposed to strong leakages from [Formula: see text] mainly. These assertions will be demonstrated on the synthetic Marmousi II as well as a North Sea ocean bottom cable data set, in which inverting for the horizontal velocity rather than the vertical velocity yields more accurate models and migrated images.

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