MultiFocusing© TechnologyMarianne Rauch-Davies, Ph.D.David Schwartz

Contents

• MultiFocusing© theory

• MultiFocusing© vs. conventional processing

• Diffraction

Conventional PSTM MultiFocusing© Post-STM

The Image is the message……

MultiFocusing imagingNMO/time and depth migration imaging

Wave front parameters analysis

Stacking Velocity analysis

Pre-stack seismic data

MultiFocusing© CMP

Real geology is not simple

MultiFocusing© theory

Common Reflection / Depth Point Stacking

SHOTS RECEIVERS

REFLECTOR

COMMON REFLECTING POINT

2

220 V

xtt

Conventional stack

v+

+

+

vv

vv

v

vv

+

+

+

Shot coordinate

Rec

eive

r co

ordi

nate

++ +

++

+

++

Normal move out equation is valid when only traces with equal distance to shot and receiver are stacked within a CDP gather (red)

CMP position

CMP traces

MF traces++

Conventional stack

MultiFocusing time correction formula is valid for arbitrary subsurface structure and for arbitrary source-receiver configurations

0

22 sin2)(

V

RXXRR ss

0

22 sin2)(

V

RXXRR rr

source and receiver positions

are the radii of curvature of the wavefronts

rs XandX

is the emergence angle of the normal ray

),,( CEECRE RRR

),,,,( 0 rsCRE XXXR focusing parameter

MultiFocusing move-out correction

CRE Radius & CEE Radius and emergence angle bX0

βО

D

Rcee

О

X0

β

Rcre

Rcre – radius of curvature of common reflection elementRcee – radius of curvature of reflected surface

2D MultiFocusing – 3 parameters

3D MultiFocusing - 8 parameters

The MF sums the data along the MF stacking surface

MF stacking surface

MultiFocusing stack

v

+

+ ++

v

+

vv

vv

v

vv

++

Shot coordinate

Rec

eive

r co

ordi

nate

++ +

++

+

++

+ CMP tracesMF traces+

CMP position

+

+

++

+

+++++

+ + + ++

+

++

+++

Normal move out equation is valid when only traces with equal distance to shot and receiver are stacked within a CDP gather.Nearby traces (green) can not be used but are utilized by our MultiFocusing™ methodology.

MultiFocusing stack

X0Xi

t0-Δt

t0

t0+Δt

TIM

E

Rcre β

Wavefront

z0

z0-Δz

z0+ΔzX0

Reflector

Xi

X

DE

PT

H

Velocity corridor picking

Conventional stacksp1 sp2 sp3 sp4 sp5

sp1 sp2 sp3 sp4 sp5

Geomage MultiFocusing stacksp1 sp2 sp3 sp4 sp5

sp1 sp2 sp3 sp4 sp5

Synthetic horizontal reflector

Rugged Topography – synthetic example

Conventional

MultiFocusing©

Rugged Topography – real data

Anisotropy study begins with scanning for 5 parameters

MultiFocusing anisotropy

V Slow V Fast V Azimuth

Anisotropy attributes

Anisotropy cubes

Enhanced Pre-Stack Gathers

The MF sums the data along the green surface. The partial MF sums the data around the specified point (point A). The partial MF is shown in red coincides locally with the MF stacking surface.

MF stacking surface

A

Enhanced MultiFocusing gathers

Original Gather MF Enhanced Gather

Enhanced MultiFocusing gathers

MF Enhanced Gather after MF-MoveOutMF Enhanced Gather

MultiFocusing – enhanced pre-stack gathers

Original gathers

MultiFocusing enhanced gathers

MultiFocusing© vs. conventional processing

Examples around the globe

• Increases poor signal/noise ratio

• Resolves signal over rugged topography

• Resolves curved reflectors/ dipping events

• Resolves variable velocity

• Azimuth preservation

• Use diffraction to detect natural fracturing

The MultiFocusing method - advantages

Conventional processing MultiFocusing processing

Reprocessing of vintage seismic data

Reprocessing of seismic data in foothills

Conventional processing MultiFocusing processing

Increasing vertical Resolution (~ 25% in frequency bandwidth)

Conventional processing MultiFocusing processing

Salt body

Salt dome body contouring

Better multiple attenuation

PSDM Post stack depth migrated MF

PSDM Post stack depth migrated MF

PSDM Post stack depth migrated MF

Depth 3D processing

Conventional processing MultiFocusing processing

Eastern Europe (fold 32) – 1920 ms

500 ms

Conventional processing MultiFocusing processing

600 ms

Conventional processing MultiFocusing processing

Diffraction

A diffraction occurs when a wave encounters an obstacle.

In classical physics, the diffraction phenomenon is described as the apparent bending of waves around small obstacles and the spreading out of waves past small openings.

Research suggests that this can be used to map fractures in the sub-surface from seismic.

Wave front

Obstacle

Diffraction - definition

How do we identify discontinuities?

X0

О

D

Rcee

О

X0

β

Rcre

β

Reflection interface

MultiFocusing ray scheme

О

X0

β

Rcre=Rcee

0

22 sin2

V

RXRXR ss 0

22 sin2

V

RXRXR RR

MultiFocusing scheme for diffractions

Fractures

Numerical model

Size of fracture: 1 x 0.3 meter

Fracture intensity

GMF Stack

GMF Post-STM

GMF Diffraction Stack

GMF Diffraction Post-STM

Offshore 2D – Mediterranean Basin

Geomage MultiFocusing – structure stack

Offshore 2D - Mediterranean Basin

Geomage MultiFocusing – Diffraction stack

Offshore 2D - Mediterranean Basin

MultiFocusing – migrated diffraction stack

Offshore 2D - Mediterranean Basin

MultiFocusing – migrated diffraction stack

Colored on migrated MF stack

Example – 3D diffraction volume

Thank You