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Thesis Defense

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Ohad Barak

Stanford Exploration Project

February 24th 2017

Seismic Rotational Data:

acquisition, processing and applications

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Seismic exploration

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Marine acquisition

Land acquisition

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Seismic land data

Data courtesy of Shell

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Reflections

Surface waves

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Subsurface image

Image courtesy of Chris Leader

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What do seismic data represent?

Data courtesy of Shell

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Vertical

ground motion

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Axiom

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The universe has

three spatial dimensions

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Axiom

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The universe has

three spatial dimensions

Six degrees of freedom

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Six degrees of freedom

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Z

Yaw

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Six degrees of freedom

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Z

Yaw

X

Roll

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Six degrees of freedom

10

Z

Yaw

X

Roll

Y

Pitch

Axis

Particle Velocity

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Rotation Rate

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Z

Vertical

vz

Yaw

rz

X

Radial

vx

Roll

rx

Y

Transverse

vy

Pitch

ry

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Six degrees of freedom

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Z

Yaw

X

Roll

Y

Pitch

  • Accelerometers
  • Gyroscopes
  • (GPS, Pitot, Pressure, ….)

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Six degrees of freedom

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Six degrees of freedom

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Six degrees of freedom

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  • MEMS accelerometers
  • MEMS gyroscopes

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Six degrees of freedom

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Electrokinetic rotation sensor

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Six degrees of freedom

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Electrokinetic rotation sensor

Not used in current

seismic acquisition

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(no market)

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Agenda

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  • Current industrial seismic acquisition:
    • What do we record?
  • Continuum mechanics background:
    • What should we also record?

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Agenda

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  • Current industrial seismic acquisition:
    • What do we record?
  • Continuum mechanics background:
    • What should we also record?

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Marine streamer acquisition

Current seismic acquisition technology / Continuum mechanics background

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Hydrophone

Pressure sensor

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Marine streamer acquisition

Current seismic acquisition technology / Continuum mechanics background

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Hydrophone

Pressure sensor

P-wave

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Ocean bottom acquisition

Current seismic acquisition technology / Continuum mechanics background

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Hydrophone+3C geophone

Pressure +

Translations

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Ocean bottom acquisition

Current seismic acquisition technology / Continuum mechanics background

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P-wave

Shear wave

P-wave

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Land acquisition

Current seismic acquisition technology / Continuum mechanics background

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P-wave

Shear wave

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Elastic waves

Current seismic acquisition technology / Continuum mechanics background

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Rotation

Sensor?

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Rotated monuments in the near field of earthquakes

Current seismic acquisition technology / Continuum mechanics background

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Lee et al., 2006

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The first seismometer

Current seismic acquisition technology / Continuum mechanics background

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Chang Heng, China,

132 AD

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“Earthquake Weathercock”

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Seisball visualization of 6C seismic motions

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1C

3C

6C

Current seismic acquisition technology / Continuum mechanics background

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Vertical

Radial

Transverse

Yaw

Roll

Pitch

Data courtesy of Chevron

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Time (sec)

Offset (m)

0

1.5

-400

0

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Agenda

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  • Current industrial seismic acquisition:
    • What do we record?
  • Continuum mechanics background:
    • What should we also record?

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Continuum mechanics: Infinitesimal displacements

Current rotational acquisition / Rotations from magnetic projections / Silver Lake magnetic-rotation experiment

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Infinitesimal strains

Current seismic acquisition technology / Continuum mechanics background

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Relative displacement between

the two points P and Q:

L: Displacement-gradient tensor

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Infinitesimal strains

Current seismic acquisition technology / Continuum mechanics background

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L: Displacement-gradient tensor

Symmetric

Anti-Symmetric

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Infinitesimal strains

Current seismic acquisition technology / Continuum mechanics background

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Symmetric

Cauchy infinitesimal strain tensor

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Infinitesimal strains

Current seismic acquisition technology / Continuum mechanics background

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Symmetric

Cauchy infinitesimal strain tensor

stress

strain

Hooke’s law:

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Infinitesimal strains

Current seismic acquisition technology / Continuum mechanics background

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Infinitesimal rotation tensor

Anti-

symmetric

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Infinitesimal strains

Current seismic acquisition technology / Continuum mechanics background

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Anti-

symmetric

Infinitesimal rotation vector

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Dilatational strain

Current seismic acquisition technology / Continuum mechanics background

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Displacement vector

Pujol, 2003

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Simple shear strain

Current seismic acquisition technology / Continuum mechanics background

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Displacement vector

Pujol, 2003

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Pure shear strain I

Current seismic acquisition technology / Continuum mechanics background

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Displacement vector

Pujol, 2003

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Pure shear strain II

Current seismic acquisition technology / Continuum mechanics background

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Displacement vector

Pujol, 2003

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Pure rotational strain

Current seismic acquisition technology / Continuum mechanics background

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Displacement vector

Pujol, 2003

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Same translations, different strains

Current seismic acquisition technology / Continuum mechanics background

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Wave mode: shear wave

Strain: Simple shear

Wave mode: P-wave

Strain: Dilatational

  • Volume change
  • No rotation
  • No volume change
  • Rotation

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Same translations, different strains

Current seismic acquisition technology / Continuum mechanics background

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Wave mode: shear wave

Strain: Simple shear

Wave mode: P-wave

Strain: Dilatational

  • Volume change
  • No rotation
  • No volume change
  • Rotation

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Same translations, different strains

Current seismic acquisition technology / Continuum mechanics background

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Wave mode: shear wave

Strain: Simple shear

Wave mode: P-wave

Strain: Dilatational

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  • Volume change
  • No rotation
  • No volume change
  • Rotation

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Rayleigh surface wave

Current seismic acquisition technology / Continuum mechanics background

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Dan Russell, Pennsylvania State University

http://www.acs.psu.edu/drussell/Demos/waves/wavemotion.html

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What should we also record?

Current seismic acquisition technology / Continuum mechanics background

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What should we also record?

Current seismic acquisition technology / Continuum mechanics background

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Hydrophone

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What should we also record?

Current seismic acquisition technology / Continuum mechanics background

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Hydrophone

Geophones:

Translations

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Strains

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What should we also record?

Current seismic acquisition technology / Continuum mechanics background

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Hydrophone

Yaw

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Pitch

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Roll

Geophones:

Translations

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Strains

Rotation sensors

Record more strains!

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Thesis structure

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  • Introduction
  • Chapter 2: Seismic rotations from induction-coil magnetometers
    • Silver Lake multicomponent seismic / EM survey
  • Chapter 3: Wave-mode separation with translations and rotations
    • Kettleman six-component survey
  • Chapter 4: Automatic wave-mode identification using machine learning

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What is recorded by current seismic acquisition?

Current rotational acquisition / Rotations from magnetic projections / Silver Lake magnetic-rotation experiment

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  • 1 hydrophone: pressure
  • 3 geophones: displacements

We do not record rotations:

P-wave

S-wave

stress

strain

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What is six-component data�Acquisition of rotational data�What can we do with six-component data

Rotations are strains

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Hooke’s law:

Rotations are caused by the

anti-symmetric strains:

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Seismic exploration

Images courtesy of Chris Leader

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MAZ

NATS

WATS

OBN

Coil

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Example shot record

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Example shot record

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Direct arrival

Refractions

Reflections

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Earth model

Images courtesy of Chris Leader

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