6 months at CWP: Done a lot, but not done yet

Or: how to deal with black magic

by

Dr. Ernst Niederleithinger

Senior Scientist and Deputy Division Leader atBAM( Federal Institute for Materials Research and Testing)

Berlin, Germany

Visiting Research Professor at Colorado School of Mines

CWP Seminar, 2013-12-02 Niederleithinger 1

Motivation to come here:

But there was more than that!CWP Seminar, 2013-12-02 Niederleithinger 2

Content

Things to be cared about in geophysics and NDT:

Events

Changes

Images

Where to go from here?

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Events

Seismics: Earthquakes, fracking,….

Concrete: Load induced cracks,…

Localization, Characterization

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Events

One tool: Time Reversal (Fink et al.)

Reciprocity

Inject time reversed signals at receivers

Energy will focus at source

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Events

One tool: Time Reversal (Fink et al.)

Reciprocity

Inject time reversed signals at receivers

Energy will focus at source

Improvement?Deconvolution!

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Does it really work? Experiment!

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Does it really work? Experiment!

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Setup: forward

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Data: forward

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Setup: backwards

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Data: backward

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Focus!

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Next topic: Changes

Seismics: stress, oil/gas content,….

Concrete: stress, degradation,….

Both: Detect it as early as possible!

„Global“ changes: Coda Wave Interferometry

Localization? Ideas by Pacheco & Snieder, Larose, Sens-Schönfelder,….

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Simple experiments: subtle changes detected,but no localization!

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Localization is possible!

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Don’t believe it? Experiment!

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Don’t believe it? Experiment!

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Don’t believe it? Experiment!

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Results (“simple” CWI)

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Results (“simple” CWI)

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Preliminary Results (“advanced” CWI)

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Preliminary Results (“advanced” CWI)

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Last but not least: Imaging

Seismics: Layers, structures, hydrocarbons

Concrete: rebars, tendons, voids, cracks,…

Both: Mapping (multiple) reflections recorded close to/at the surface to where they belong! Same math+physics!

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RTM

Ultrasonic black magic in TV

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SAFT imaging

Main contributors to SAFT: Langenberg, Mayer, Marklein,University of Kassel

Friese et al., SMT 2008

Synthetic aperture focusing technique

Family of methods

Constant and multi-offset data

Direct reflections only

Phase evaluation possible (Krause et al., SF&R 2008)

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Reverse Time Migration!

Sabine Müller Ernst Niederleithinger Maria Grohmann Martin Krause

Thomas Bohlen Paul Sava

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Synthetic example 1

RTM

Model used for simulating data

Velocity modelfor migration

RTM result

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Off to Horstwalde

Foundation slab at our test site

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Off to Horstwalde

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Off to Horstwalde

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Off to Horstwalde

Simulations

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Off to Horstwalde

Real data

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Back to the lab

Measurements:

• Polyamide block,(100*60*30 cm³)

• Point contact transducersin arrays of 4

• P, SHx, SHy

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Back to the lab

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Back to the lab

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Seismic Interferometry

Seismic Interferometry

• Reconstruction of Greens functions

• Data, where you think you don‘t have data

• Gerald Schuster• Roel Snieder

• Kees Wapenaar

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„Green‘s function retrieval“, „Seismic Interferometry“

Trace interpolation, synthetic example (44 sources)

Seismic Interferometry

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„Green‘s function retrieval“, „Seismic Interferometry“

Trace interpolation, synthetic example (44 sources)

Seismic Interferometry

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„Virtual Real Source“ (Behura, 2006)

synthetic example (11 sources)

Seismic Interferometry

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Back to the lab

Just more black magic? Experiment!

(on the way)

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That will be simple. Reality is much more complicated:

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Let‘s steal anotherblack magic idea:

Autofocusing

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Let‘s steal anotherblack magic idea:

Autofocusing

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